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THE MASSACHUSETTS TOXICS USE REDUCTION INSTITUTE

University of Mauachurar at Lowell one University Avenue Lowell, MA 01854 Telephone: (508) 934-3275 FAX: (508) 453-2332

METAL FINISHING INDUSTRY MODULE

TOXICS USE REDUCTION PLANNER CERTIFICATION COURSE

by Chris Ford

INTRODUCTION

The purpose of this module is to discuss Toxics Use Reduction within the framework of the processes involved in Metal Finishing. The intent of the module is to expand on the general knowledge aquired during the toxics use reduction planner curricula. This module will focus on the most current available toxics use techniques available for the metals finishing industry.

The objective is to provide participants with the basic vocabulary and basic process knowledge that will enable them to interact effectively with members of a TURA team within these industry segments. The material will seek to identify those areas of particular concem to the TURA process, review the variety of process characterization approaches and consider some of the options presently being examined within this industry.

It is hoped that with the variety and resources available within this group that the process will be an interactive one, and that participants will not hesitate to contribute their experiences and expertise. The scope of the blueprint of processes and not to be an in depth study in procedures.

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TOXIC USE REDUCTION PLANNING

IN THE METAL FINISHING AND ELECTROPATING INDUSTRIES

TABLE OF CONTENTS

. INTRODUCTION ................................................. 1.

1.0 INDUSTRY OVERVIEW ............................... 2.

2.0 PROCESS CHARACTERIZATION .................. 17

3.0 TOXIC USE REDUCTION OPTIONS ............... 22

REFERENCES ..................................................... 30

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/ PROCESSES IN THE METAL FINISHING INDUSTRY

There are two major types of Electroplating Facilities to be considered: one is a Job Shop and the other is a Captive Shop. A job shop is one that performs work for other companies. They will provide many finishes on a variety of substrates, as their knowledge and physical layout will allow. A captive shop is one that is part of another large company, and performs all its finishing for pieces that are made or provided by that company.

There are also two major ways in which work is handled in Electroplating Facilities. Rack work is work that is held on structures that hold the pieces immobile during finsihing operations. Barrel work is loaded into barrels and tumbles during the finishing operation, in order to provide equal solution access to all parts.

While the type of shop and the way in which work is handled will have an effect on the way toxics use reduction is implemented most of the following processes will be common in all plating operations.

I. CLEANING

A. Degreasing

Often when parts come to the shop for finishing, they have machining oils or buffing compounds from the previous manufacturing steps. These oils need to be removed before the finishing process can proceed. The chlorinated solvents, such as 1, 1,l Trichloroethane, Trichloroethylene, and others serve as degreasing fluids. These fluids are held in units called vapor degreasers. The degreasers have heating coils in the bottom to heat the solvent to boiling. Cooling jackets keep the vapors in the unit. Parts are then dipped into the vapor zone, where the vapors condense on the part, and solvate the oils. The oil/solvent mixture then cascades, or sheets, off the piece. Drawing the work out of the degreaser slowly allows the solvent to evaporate off the piece within the confines of the unit. When the piece is withdrawn, it is clean, oil-free, and dry.

Sources/Contents of Waste: - Fugitive air emissions of solvent. - Off-Site Recycling of solvent. - Still bottoms from still if recycled

on-site.

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B. Soak Cleaning

Soak cleaning usually occurs in a solution of sodium hydroxide, detergent, or other material that can solvate oils and loosen and remove dirt particles. Soak cleaning is used to remove oils and dirt.

SourcedContents of Waste: - Solution contains sodium hydroxide, other detergent aids, oils, greases, buffing compounds, dirt and soils, and basis metals (along with alloying elements). When dumped, it may be treated on-site, or sent off-site for treatment

constituents and contaminants, and are treated in the WTS.

- Rinse waters contain all the bath

c. Electrocleaning

There are three general types of electrocleaning: Direct, Reverse, and Periodic Reverse.

Thw solutions are heavily alkaline and often heated. The work is immersed in the solution, and current is applied.

If the work is the cathode, the cleaning is said to be Direct. In this case, Hydrogen gas is evolved from the surface of the work, and assists in scrubbing oils and dirt from the part's surface. However, any positively charged particles (especially metallics) in the solution will tend to adhere to the work. This type of cleaning is used generally when Reverse Cleaning is harmful to the work.

In Reverse Cleaning, the work is made the anode. In this case, Oxygen gas is evolved at the surface of the piece, and assists in oil and dirt removal. Because of the reversed current, any metallics in the bath can not deposit on the piece. Due to these factors, Reverse Cleaning should be used whenever possible.

Periodic Reverse Cleaning is where the work is made alternately anodic and cathodic. This cleaning technique is used in oxide removal where acidic processes (as will be discussed in the next section) are harmful to the base material.

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SourcedContents of Waste: - Solution contains sodium hydroxide, other detergent aids, oils, greases, buffing compounds, dirt and soils, and basis metals (along with alloying elements). When dumped, it may be treated on-site, or sent off-site for treatment. The Solution is dumped when the amount of owgrease and didsoil make effect cleaning an impossibility. Maintenance adds are made to these solutions

- Rinse waters contain all the bath constituents and contaminants, and are treated in the WTS.

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D. Acid cleaning

Generally called Pickling, this step is performed to remove oxide and scale from the parts. The solution is usually sulfuric or hydrochloric acid, The parts are immersed in this solution, then are removed and rinsed. After this step, the parts are ready for any one of a number of surface finshing proceses.

Sources/Contents of Waste: - Solution contains acid and basis metals. It is dumped when it is no longer able to effectively remove scale and oxide, or when the copper concentration becomes high enough to form an immersion plate on the parts, which is undesirable. No maintenance adds are made to this solution. The solution may be treated off-site, or on site in the WTS.



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11. PLATING PROCESSES

A. Cyanide Based Plating processes

1. Copper Cyanide Plating

This type of plating is widely used as an underplate or pre-plate before a final finishing operation such as nickel or gold. The major constituents of these baths are Potassium Cyanide, Potassium Hydroxide, and Copper Cyanide.

2. Silver/Gold Plating

These metals are generally used asethetically in jewelery, and for superior elecrical conductivity in industrial applications. These baths use cyanide that is complexed with organics. Precious metal plating is far ahead of the "common metals" in terms of conserving solution and recovering metals.

3. Cadmium Plating

Cadmium is a metal that exhibits almost superior corrosion resistance. It is chromated after plating. Its toxicity and very tight regulation by EPA and OSHA have made this material much less used in industrial applications. The largest segment of the cadmium plate market is the Military, which has not yet changed its specifications to replace cadmium with a less toxic material.

4. Zinc Plating

Zinc Plating is very versatile, and like cadmium, is chromated after plating. These chromate films provide further corrosion resistance and are formed in a wide range of colors: clear, yellow, gold, olive- drab.

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- All the cyanide bases processes will have in them cyanide salts, both potassium/sodium cyanide, and metallic cyanide salts. They will also contain either the potassium/sodium hydroxide. Contaminants include any dragged in metaldsalts, and organic breakdown products from added brightners. These solutions are rarely, if ever, dumped. Adds are made continuously, based on laboratory analysis, and the baths are purified on a regular basis.



B. Non-cyanide Based Processes

1. Nickel Plating

There are two main types of Electrolytic Nickel Plating. The first is Sulphamate Nickel. This is also known as dull nickel or engineering nickel. It is very ductile, and can be used in many applications. The primary constituents of this bath are nickel sulfamate, nickel chloride, and boric acid.

The second main type of Electrolytic Nickel Plating is Bright Nickel. It is bright and hard, and is used mainly for decorative purposes. The primary constituents of this bath are nickel sulfate, nickel chloride, and boric acid.

- The solutions contain the nickel salts, nickel chloride and nickel sulfamatehulfate, and boric acid. Contaminants include any dragged in metaldsalts, and organic breakdown products from added brightners. These solutions are rarely, if ever, dumped. Adds are made continuously, based on laboratory analysis, and the baths are purified on a regular basis.



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2. Tin Plating

Electroplated Tin is used mainly for its ductility, corrosion resistance, and consistant plating thickness. Bright Acid Tin is composed mainly of Sulfuric Acid and Tin Metal. Stannate Tin is composed mainly of Potassium Stannate and Potassium Hydroxide.

Contaminants include any dragged in metals/salts, and organic breakdown products from added brightners. These baths also form tin-based sludges, which must be removed on ocassion by settling or filtration. These solutions are rarely, if ever, dumped. Adds are made continuously, based on laboratory analysis, and the baths are purified on a regular basis.



3. Tin/Lead Plating

Tin/Lead Alloy in varying ratios is used generally as a plating upon which soldering can take place. These baths come in two general formulations: Fluoboric Acid Based, and Sulfonic Acid Based. The Fluoboric Acid Based baths can be difficult to treat, due to the presence of fluoborates (boron), which are tightly regulated in some sewer districts. Sulfonic Acid baths are less corrosive and less difficult to treat.

Solutions will contain tin and lead metal, as well as fluoboric or sulfonic acid. Contaminants include any dragged in metals/salts. These solutions are rarely, if ever, dumped. Adds are made continuously, based on laboratory analysis, and the baths are purified on a regular basis.



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C. Electroless Nickel

This form of Nickel, alloyed with Phosphorous, is applied from a solution that does not require electricity to cause the reduction of Nickel ions onto the surface of the part. This results in uniform deposition of nickel onto the work, without the usual vagaries in thickness that result from current density problems.

The most common bath constituents are Nickel Sulfate as the nickel source, and sodium hypophosphite as the reductant.

Solutions will contain Nickel Sulfate, sodium hypophosite, and organic acid such as lactic or glycolic, which are used as chelating agents. Contaminants include any dragged in metals/salts, and organic breakdown products from added brighteners. These solutions are dumped on a regular basis. When the breakdown products of the sodium hypophosphite reach a certain level, they interefere with the reduction reaction. Maintenance additions are made on a regular basis.


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111. Stripping

Ocassionally, either due to internal QA problems, or to work that has a protective metallic coating applied, pieces must be stripped of coatings down to the basis metal.

There are seemingly as many different stripping solutions for as there are base metal/applied coating combinations. In general, they tend to run as either acids, alkalies, or cyanide based. They can be heavily chelated, or not at all. The most important property they have (besides ability to strip the mating) is that they must not attack the base metal.

These solutions contain the stripping components, and large amounts of stripped metal. Contaminants include any dragged in metals/salts. These solutions are dumped when they have stripped the maximum amount of metal that they can. With some solutions, it is possible to increase solution life with additions, but this is finite. Strips used for precious metals are reclaimed off-site by a refiner.


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IV. Surface Treatment of Aluminum

There are two main surface treatments of aluminum: Anodizing and Chromating. Anodizing is the process by which an aluminum part is made anodic (as oppossed to plating where the work is the cathode) in an acidic solution, usually chromic or sulfuric acid, and a film of Aluminum oxide is built up on the surface of the aluminum. Chromating is the process by which a chemical conversion coating of chromate is formed on the aluminum. Both processes use a similiar cleaning scheme.

A. Anodizing

Sulfuric Acid Anodizing takes place in a 15% solution of sulfuric acid. The work is made the anode, and an aluminum oxide coating is built up on the part. This coating provides both corrosion and wear resistance. It is also an excellent basis for dyeing or painting.

- These baths contain acid and large amounts of aluminum from the dissolutive anodizing process. These baths are dumped when the anodizing ability is lowered by the amount of aluminum in the solution. Maintenance additions of acid are made to these baths.


Because of the structure of the coating, it lends itself easily to dyeing. These dyes are organic, or organo-metallic, which often contain chrome (in the trivalent state).

- These baths contain organic dyestuff and some contain trivalent chromium. These dyes are dumped on occassion, as they lose their ability to give deep, rich shading. Maintenance additions are occassionally made to these baths.



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Whether or not the pieces are dyed, they need to be sealed. This can performed with hot water, nickel acetate, or sodium dichromate, depending on the properties required.

- The nickel solution contains the nickel acetate and aluminum. The sodium dichromate seal contains hexavalent chromium and aluminum. The solutions are dumped when their sealing ability is lost due to dragout of solution. Maintenance additions are not made.


B. Chromating

Chromating, depending on the color, takes place in a solution of chromic acid and additives. A simple dip will allow the chromate film to adhere to the aluminum surface. The type of solution will determine the shade or color produced.

- The chromating solutions contain hexavalent chrome and nitric acid. These dyes are dumped on occassion, as they lose their ability to give good color and corrosion resistance. Maintenance additions are made to these solutions.



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V. Cleaning/Surface Preparation

If required, solvent cleaning is performed as above. Soak cleaning is performed in a cleaner that does not contain sodium hydroxide, as aluminum is attacked by sodium hydroxide. One example is a solution of borax (Sodium Tetraborate). These solutions will have basically the Same contaminants as the soak cleaners for the plating processes.

Next, the surface is etched by a sodium hydroxide based etchant. This etch step is performed to thoroughly clean and prepare the suface for further treatment.

- The etchant baths contain sodium hydroxide and aluminum that is removed from the work. The bath is dumped when the amount of aluminum (in the form of sodium aluminate) becomes too high for proper etching to occur. Maintenance additions are made on a regular basis.



The smut formed during this process is then removed with a nitric or nitridhydrofluoric acid dip. The aluminum is now ready for surface finishing.

- These baths contain acid and large amounts of aluminum from the remove smut (aluminum). These baths are dumped often, because the desmutting ability is rapidly lowered by the amount of aluminum removed. Maintenance additions are not made to these baths.


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VI. Rinse Waters

A more detailed discussion of M s e water will follow, but for now let’s discuss some of the operational aspects. The rinse waters have one function - they must remove the chemicals that are dragged out of the preceeding bath sufficiently so that the parts are clean for the next process. If residue remains, it may interfere with the plating/post plating operations, and may also contaminate the next solution, rendering it useless, and nessecitating solution replacement, thereby increasing Toxic Use.

VII. Metal Finishing Industrial Waste Treatment

As we can see from these process diagrams, waste is created by dragout into rinse tanks. These are usually treated in-house by a conventional Waste Treatment System.

These processes can be either continuous flow or batch, depending on the total flow of the system - low flows may be treated in a batch scheme, while higher flow tend to require continuous flow systems.

A. Cyanide Destruction

Solutions that use cyanide require treatment to remove that cyanide completely from the effluent. This is usually performed in a tsvo- stage alkaline chlorination system. In this system, sodium hydroxide and sodium hypochlorite are added to the treatment tank to oxidize the C=N molecule to the cyanate form. After sufficient contact time, the pH is lowered, and further sodium hypochlorite is added. This will cause the cyanate to be oxidized to carbon dioxide and nitrogen gases. It takes about 7 pounds of sodium hydroxide and eight pounds of sodium hypochlorite to completely oxidize 1 pound of cyanide.

B. Chrome Treatment

Chrome solutions must have any hexavalent form of chromium changed to the trivalent form by chemical reduction. This is needed for two reasons: 1. The hexavalent form of chrome is many times more toxic than the trivalent form, and 2. The main treatment for the metal bearing wastestream is precipitation of the metals, and only the trivalent form of chrome will precipitate. In a single step, with the addition of sulfuric acid and sodium

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metabisulfite, hexavalent chrome is reduced to the precipitable trivalent chrome. In general, it takes about 1.5 lbs of sodium metabisulfite, and 0.80 lbs. sulfuric acid to reduce 1 lb of hexavalent chomium.

As you can see in the diagram, these wastes are combined with the acid/alkali rinses, which do not need cyanide or chrome pretreatment. To this tank is added ferrous sulfate and sulfuric acid. The ferrous sulfate is used as a sacrificial metal to tie up chelating agents, and allowing regulated metals to be precipitated in the following step. The amount of ferrous sulfate and sulfuric acid depend on the degree of chelation and pH characterisitcs of the incoming streams.

The aggregated waste streams are then directed to another tank, where the pH is raised to the proper level to precipitate the metal ions from the solution. This metal hydroxide then settles and forms sludge. This sludge is then disposed of as a hazardous waste. The water is tested for residual metal content, which needs to be below the stated discharge limits for the area that the plant is located, and if it is, the water is discharged to the sewer system or surface water.

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Activity #1 Looking at TUR Incentives

Task As the toxics use reduction planner for Plating Co. how would you go about evaluating the possibility of switching from cyanide zinc to a non-cyanide zinc formulation.

Factors to identify:

1. Cost to dispose of cyanide solution. 2. Cost to install new noncyanide solution. 3. Cost/Savings of additions to new solution vs. old solution. 4. Cost/Savings of waste treatment. 5. Cost/Savings due to additionallreduced plating time required. 6. Cost/Savings due to additionallreduced amount of work shop is

able to perform (based on material compatibility with solution). 7. Savings due to falling below threshold reporting limits for

DEP/TURA and EPA.

Information available:

1. Cost to dispose cyanide solution: $3.50 2. Cost to install new solution: $5.00 3. Costs of additions: Salesman est: 1.2 times CN.

CN costs: $4.00/wk. 4. Cost of waste treatment:

need to increase ferrous sulfate and calcium chloride by 15 % , and due to reduced cyanide, reduce soldium hypochlorite by 20%. Original use: Ferrous Sulfate: $2.00/wk

Calcium Chloride: $2.50/wk Hypochlorite: $6.00/wk

Due to heavy chelation in bath,

5. Plating time to achieve same thicknesses is approximately the same.

6. Due to base material incompatibilities, Plating Co. must reject 11 96 of their zinc business based on last year. Last year’s sales of zinc business = $217,400.00.

7. Savings due to fees and time spent on paperwork. Fees = $5,000.00 Man-hours: ?????

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PROCESS CHARACTERIZATION

As we all know Production Unit and Unit of Product are the two main devices currently used to quantify Toxics Use Reduction.

I. Production Unit: The stock definition of PU is: a subfacility level unit of analysis that will more accurately detail toxic chemical use. What does this mean? All the places where the toxic chemical is used must be shown. In order to provide varied facilities a way to do this in a facility specific manner, the choice of production units is left to the facility.

II. Unit of Product: this is semi-dependent on the production unit that you use. A chicken and egg situation? Perhaps, but one that may be managed. The unit of product is very difficult for the metal finisher to define, especially in the job shop situation. Let’s look at some specific instances.

A. Square Area

Square Area is often thought of as the best Unit of Product for the Metal Finishing Shop. Total square footage plated throughout the year provides a means for relating toxic use reduction to relative throughput.

1. Cleaning Processes - doesn’t take into account the condition of the surface of the parts. For instance, let’s say that you degrease 20,000 sq. ft. of work this year. 10,OOO square feet of work has a very thick coat of machining oil, and 10,OOO square feet of work with just a light protective coat of oil. You use 1,000 pounds of degreasing fluid to do this work. Next year, you also degrease 20,000 sq. fi. of work, but 19,OOO sq. ft. has the heavy machining oil, and 1,OOO sq. ft. has the light oil. You now have to use 1,500 pounds of degreasing fluid. By using sq. ft., your total TU has increased, and you must report a BRI of negative 5096, even though in reality, you did not use more toxic chemical to do the same amount of work. This example also holds true for electrolytic cleaning, where you may get parts in that have variable soil and oil amounts, and for pickling, where parts arrive at your plant in varying stages of oxidation (rust). There is no way to quantify the intial state of the work, and that is what determines the toxic use in the initial degreasing, cleaning, and pickling operations.

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2. Plating Process - doesn’t take into account the thickness of the plate, which is important if you are reporting for metals. For instance, let’s say that I plate 20,000 square feet, and 5,000 is plated with 1 uinch, 5,000 is plated with 2 uinces, and 10,OOO is plated with 3 uinches. I used 100 pounds of metal, 60 pounds of which went out with the as product (20,000 sq. ft. with an average of 2.25 uinches). The rest was wasted to the plant Treatment System, as a result of dragout due to surface configuration of the pieces. The next year, I plate the same pieces, but with 2, 4, and 6 uinches respectively. I use 160 pounds of metal, 120 of which goes out on the parts, and the same 40 pounds goes to the waste treatment system because the parts drag out the exact same amount of solution. Now I have to report a BRI of negative 6096, even though I wasted the exact same amount. Try multiplying this times the 40, 50, or even 150 types of parts that an average job shop will plate during the course of one day that are plated to different specifications, and in fact may have a fairly wide tolerance specified (e.g. between 5-8 uinces is allowed). This would require 100% QC to get an average thickness on the pieces and relate that back to the original square footage. A difficult task at best.

B. Amp Hours/Square Foot

Ampere hours/square foot does provide a means to relate thickness and square footage plated to Toxic Chemical Use. Unfortunately, this only works for electrolytic processes. Degreasing, soak cleaning, pickling, electroless plating, and aluminum processes such as etching, dyeing, and chromating obviously do not lend themselves to this unit of product.

C. Counting Units

Number of pieces, number racks processed do not make much sense as units of product. There would be no relation to the amount of Toxic Chemical used per piece or per rack. Some would suggest that each different type of piece that comes in should be considered a unique unit of product. In this case, measuring the amount of toxics used/piece would require that the solutions be analyzed before and after each run of that particular

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part. The difference, divided by the number of pieces (plus the rack), would be the amount used per piece. This would also entail inefficient use of shop resources, as only one type of job could be done in any one production unit at any one time, lest diferent pieces skew the test results. The amount of work required to do this on the number of different jobs run per day in the tyical job shop would be Hurculean, at a minimum. This procedure is an impossibility. These problems are reporting problems. We should now look at TUR from the process standpoint of actually reducing toxics in an environmentally and corporately responsible manner.

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Activity #2 Identifying production units and unit of product

Task: Using the attached process flow diagrams consider how you would divide the facility into production units. Also consider what the unit of product would be for each.

Plating Co. does three processes. 1. Tin Plating after Copper Strike and Copper Plate 2. Nickel Plating after Copper Strike 3. Nickel Plating after Nickel Strike

Decide:

Production Units

Units of Product

List your considerations in deciding on each production unit and unit of prodcut.

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PRODUCTION UNIT ANALYSIS

Degreasing

Electroclean

Pickle

Cyanide Pre-Dip

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Copper Plate

Product

Fl Immersion

Product

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TURA OPTIONS AND TECHNIQUES

I. Input Substitution of non-cyanide plating solutions

Perhaps the single most toxic chemical, on a w/w basis is cyanide, and substitution of this product will have profound effects on all the parameters listed under "incentives." Its use as a cleaning agent, and as a chelating agent in many different types of plating solutions and stripping solutions makes it a difficult material to replace. Also, it is compatible with a wide range of basis materials. Non- cyanide alternatives have proven to be very basis material specific, which does not lend itself to easy substitution. Also, non-cyanide plating solutions are less forgiving than cyanide based baths to cleaning that is less than perfect. With these solutions, it is important to identify the specific applications that these systems are applicable. There are several types of non-cyanide solutions for: Silver Cadmium Zinc Gold Copper CN based Strips

It is important in evaluating these materials that you be aware of toxic chemicals that they may contain. It would not help your company to rid itself of one listed chemical only to exceed threshold quantities of another.

II. Non-Solvent Degreasing

Non-solvent Degreasing is a technique that is beginning to be researched more and more. Most systems now involve a heavily alkaline system, either heated or used ultrasonically. There are several considerations to be taken into account. From a cleaning standpoint, these materials have difficulty penetrating into blind holes and tapped holes of small diamater, due to the high surface tension of the solution. Wetting agents can help to overcome this, with the help of agitation. From a waste standpoint, oils and grease can be dragged out of this solution, and into the plant wastewater. If the plant is not set up to control oil and grease discharges, this may result in violations. Some of these cleaning systems do have devices to separate the oil and greases from the solution, which will have the added effect of prolonging the life of the solution, and keep O+G out of the wastestream.

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III. Ferric Nitrate for Desmutting

Non or Low Nitric Acid/Hydrofluoric Acid Desmutting of Aluminum is a process that is being looked at very closely today. There are several of these products on the market currently. One typical formulation is the use of ferric nitrate as the main desmutting agent.

IV. Solution Conservation

This phrase encompasses a wide range of technologies and techniques that aim to either keep processing solution in the tank to start with, or to remove process chemicals from the rinse water and return them to the solution at the point of origin.

A. Rinse Techniques - it is possible to use less water, rnse parts better, and have available solution that can be retumed to the processing tank. These techniques will help to keep the solution in the tank. Heated Process Tanks offer the greatest degree of potential with solution conservation. Some examples for rinse configurations:

1. Techniques to replace evaporative loses:

a. Work can be spray rinsed directly over the tank. This returns solution directly to the tank, and also replaces water lost. Some practical considerations include water spray onto machinery such as pumps and filtering units, and water spray onto the floor to non- specific waste treatment units (floor spill sumps). Usually, this is done only over large surface area tanks.

b. Running the rinse tank water back into the heated tank at a rate equal to that lost by evaporation accomplishes solution conservation quite well. The key to this technique is that you must use a rinse scheme that cleans the parts effectively while using a small volume of water. This probably means using a multi-stage counter current flow rinse system. The greater the number of stages, the lower the flow needs to be to acheive sufficient cleaning.

c. For nonheated tanks, rinse waters can often be evaporated and retumed to the tank. This evaporation can be hot or cold evaporation. A hot evaporation unit might be no more than a steam coil in a dead rinse, or it may be a special high surface area evaporations system. Cold evaporation units actually operate at ambient temperatures, and are generally proprietary systems. In any case, these systems must be sized approprately. They are also high in energy costs.

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2. Reverse Osmosis and Electrodialysis are two technologies that use selective membranes for solution conservation.

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a. Reverse Osmosis (RO) is a process in which solution (in this case, from a dragout tank) is pumped into a membrane system under pressure, which allows only water to pass through, recirculating the salts back to the dragout tank.

b. Electrodialysis (ED) is a process by which solution is introduced into a vessel with a cathode at one end of the cell and an anode at the other. With two membranes in the cell, ions from the center section will travel through the membrane into the cell containing the electrode to which they are attracted, leaving behind a cell that contains pure water or at least has no charged particles).

One problem with these methods is that they all tend to concentrate not only valuable plating salts, but also contaminants. The main contaminants are organic and metallic. Organic contaminants are removed by carbon frltration of the bath. The activated carbon will absorb organics that would tend to mar the finish of the plate.

Metallic contaminants are dragged into the solution from pre-plating cleaning processes (and also from added city water). They are removed by plating a large surface area cathode at a very low voltage, thus removing the metallics without depleting the solution to a very low level.

It is interesting to note that RO, ED, and Ultrafiltration are also being researched to provide ways to remove contamination, thus extending the life of the bath.

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Activity #3 -- Brainstorming Options and Research Needs

Task Using the posted generic electropating and metal finishing process flow diagrams attempt to identify opprotunities and options for toxics use reduction.

1. Identify your three biggest concems in terms of toxics use within the posted processes.

2. As a class brainstorm available options to address the listed concems.

3. As a class identify needs for further evaluation or research in the identified areas.

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ANODIZING PROCESS FLOW DIAGRAM

Chlorinated >- Solvent

Fugitive Emissions A Solvent Oil and Grease Degreasing

D c Z + e ,

Rinse Water >-

Basis Metal Sodium Hydroxide

;;;Metal

Water >-#

Nitric Acid Hydrofluoric Acid>- Sulfuric Acid

Rinse

Desmut

% ? i 2 $ ' o n e n t s

Basis Metal b Sodium Hydroxide

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Sodium >--. Dichromate

ANODIZmG PROCESS FLOW DIAGRAM (continued)

Dichromate Seal Sodium Dichromate

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Water >- I Rinse Basis Metal I ' Acid Compents

Anodize

Metals Sulfuric Acid

Sulfuric >-, Acid

I Rinse Water

Basis Metal

Water >- Rinse Sodium Dichromate Basis Metal

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MULTIPLE STEP PLATING OPERATION

Pickle Acid Hydrochloric*

A Fugitive Emissions

Basis Metal . Hydrochloric Acid

Solvent D Oil&Grease (Off -site Recyie)

Degreasing Chlorinated>- Solvent

Potassium >- Cyanide

’Odium Hyroxide >- I Anodic yeaning I . BaisMetal Sodium Hydroxide

3% Cyanide PreDip

b

Water >- 1 Rinse.Tank 1 b Water Basis Metal Sodium Hyroxide

I Potassium Cyanide Potassium Hydroxida- I ‘OWer Strike + Copper Cyanide

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MULTIPLE STEP PLATING OPERATION (continued)

Water >-

Potassium Hydroixde Potassium Cyanide >- Copper Cyanide

Rinse Tank

Copper Plate

Water >--. Rinse Tank

0

Potassium Hydroixde Potassium Cyanide Copper Cyanide

D

I 0

Hydrochloric Acid (W

Hydrochloric Acid

t

t I

0

I Nickel Sulfate Nickel Chloride >- I Nickel Plate

w

Boric Acid

29

Metals Hydrochloric Acid

Metals Hydrochloric Acid

REFERENCES

Books

Metal Finishing Guidebook and Directory - Published yearly by Metal and Plastics Publications, Inc. Issued as a thirteenth issue with a subscription to Metal Finishing Magazine. (201) 487-3700. This is a general guide to all phases of electroplating and metal finishing, including ancillary topics such as waste treatment and rinsing.

Water and Waste Control for the Plating Shop, Kushner, Arthur and Kushner, Joseph. Gardner Publications, 1981. This is the essential text on rinsing. In an orderly progression, shows mathematically how to achieve proper rinsing while minimizing water use.

Industrial Wastewater Treatment Technology, Patterson, James. Butterworth Publishers, 80 Montvale Avenue, Stoneham, MA 02180. A text that covers pollution control topics of interest to the electroplater. Of primary interest from a TUR standpoint are the economic analyses presented concerning cost of treatment.

Articles

"Metallic Waste Reduction - An Overview" O'Rourke, James T., Camp Dresser & McKee, Inc.

"Waste Treat or Recovery? An Introduction To Resource Recovery" Werbicki, Joseph., Mirro Brite/Coating Specialties Co.

"Copper, Nickel, and Chromium Recovery In a Jobshop" Nadeau, Tom, and Dejak, Mike. Eco-Tec Ltd.

"Purification and Restoration of Chromic Acid Plating Solutions" Ionsep Brochure 012590.

"Electroplating Overview and Waste Evaluation/Tank Management and Minimizing Dragout and Rinses" Tim Greiner, MA OTA.

"PMF, Inc. Nickel Recovery Project" Collins, Jeff, PMF Inc.

30

1 I 3 1

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-rl

1

J o s c ? h J . \ ! e r b i c l c i , C3F l q i r r o - E r i t e / C o a t i n g S p e c i a l t i e s

5 4 1 P o w t u c k e t Avenue P a w t u c k e t , RI 02860

T h e f i r s t n c i n t t h c t v e h a v e t o e c c e p t i s t h p . t t h e r e a r e no xlngic s o 1 u t i o : i s t o v a s t e t r e a t m e n t p r o b l c n s . l i e h a v e , hov- e v e r , d e v e l o p e d a p r a c t i c a l a p p r o a c h t h a t c a n b r i n g e f f 1 u e r . t c o n t a m i n a t i o n l e v e l s dotin t o a p o i n t w h e r e y o u w i l ' l m e e t l o c a l d i s c h a r z e l i m i t a t i o n s , p o s s i b l y w i t h n o c o n v e n t i o n a l t r e a t m e n t .

Our c o r p o r a t e p h i l o s o p h y i n t h e f i e l d o f i i a o t e t r e a t n e n t i s t w o f o l d : R e c o v e r v a l u a b l e p l a t i n g c h e m i c a l s r a t h e r t h a n d e s t r o y i n g v a l u a b l e p l a t i n g c h e m i c a l s ; a n d , Complement r e c o v - e r y t e c h n i q u e s w i t h n o n - s l y d r e g e n e r a t i n y t e c h n i q u e s .

\.!e h e v e found t h a t t h e i o n - e x c h z n z e a n d t h e e l e c t r o l y t i c 12ro- c e s s c s crc t h e n o s t v i a b l e , c o ~ p l e n e n t a r y t e c h n i q u e s a v z i l - a b l e . Some i n p l a n t c h a n g e s n e e d t o be c a d e i n o r d e r t o a l l o w y o u t o zccommodnte ion -exch ' ange . The c h a n g e s we s u g g e s t e n - p h e s i z e waste r e d u c t i o n a t t h e t a n k %o r e d u c e t h e l o a d i n g on t h e i o n - e x c h a n g e r e s i n i n o r d e r t o m a x i n i z e t h e t i n e b e t w e e n r e m o v a l o r r e g e n e r a t i o n .

T h e s e c h a n g e s w i l l p r o v i d e y o u w i t h a d d i t i o n a l b e n e f i t s con- p a r e d t o t h e use o f c o n v e n t i o n c l t r e a t n e n t t e c h n o l o e i e s . F i r s t , y o u w i l l h a v e l e s s floor s p a c e t a k e n uy: v i t h t r e a t m e n t e q u i p n e n t . S s c o n d , you w i l l h a v e a n u c h l o v e r c a p i t z l i n v e s t - m e n t i n e q u i p m e n t . T h i r d , you w i l l r e d u c e y o u r weter a n d s eve r u s e b i l l s .

T h i s p r e s e n t a t i o n w i l l o u t l i n e t h e p r o c e s s o f c l e e n i n g u p your waste streams. I m u s t p r e f a c e i t by s a y i n g t h a t t h e r e i s r e a l l y o n l y s o much y o u c a n do w i t h t h e s e t e c h n i q u e s . They e r e n o t t h e c o m p l e t e a n s w e r t o a l l y o u r p r o b l e m s , b u t t h e y a r e s i m p l e , i n e x p e n s i v e , End t h e y c a n b e m o s t e f f e c t i v e .

The g e n e r a l l y a c c e p t e d a p p r o a c h e s t o was te t r e a t m e n t ( F i g . 1 L 2 ) c a n be d i v i d e d i n t o d e s t r u c t -- t e c h n o l o g i e s a n d r e c o v e r 2 --- t e c h n o l o g i e s . I'm sure you a r e a l l f a n i l i a r v i t h them; you h a v e r e a d e n o u g h a r t i c l e s o n t r h a t t h e y c a n do a n d w h e t t h e y c a n ' t d o .

J J

Your waste streams s h o u l d b e s e p r e g a t e d . T h e r e a r e t h r e e r e a s o n s why y o u s h o u l d s e g r e g a t e y o u r l i n e s :

- 1 -

1 . L f f i c i e n t t r e a t m e n t -- i f you p u t e v e r y t h i n c t o c c t h c r , y o u 2 c t a n a v e r a g e t r e a t m e n t w h e r e p!i i s a f c c t o r , and y o u c a n ' t r e c o v e r y z n y n e t a l v a i x e s .

2 . You g e t much x o r e e c o n o m i c a l r e c o v e r y .

3 . To i s o l a t e c h e l a t e s , w h i c h would make t r e a t m e n t p r o c e s s e s t o t a l l y i n o p e r a b l e .

F i g u r e 3 s u c g e s t s how t o s e ~ r e ~ a t e waste l i n e s . ' the p o i n t t o m a k e a b o u t s t r e a m s t h a t d o n o t r e q u i r e t r e c t m e n t i s t h a t r e - g u l a t o r y a u t h o r i t i e s d o n ' t l i k e t o s e e y o u u s e n o n - c o n t e c t water t o d i l u t e y o u r p r o c e s s wa te r . S o , i f y o u t a k e R s a n p l e t h a t i n c l u d e s d e g r e a s e r , a i r - c o n c i t i o n i n z , or o t h e r s u c h non- c o n t a c t weter , t h e y e x p e c t y o u t o p r o r ~ t e t h e a n a l y s i s as t h o u e h i t w e r e n o t b e i n g d i l u t e d . One a n s w e r , o f c o u r s e , is t o r e u s e c o o l i n g water t h r o u c h your r i n s e s . Now i t i s ? r o - c e s s w a t e r , a n d y o u h a v e t h e a d v a n t a g e o f i t s d i l u t i o n e f f e c t e v e n t h o u g h i t p r o b a b l y i s n o t a s i g n i f i c a n t f a c t o r .

You , r u s t c o n s i d e r t h e e f f e c t o f c o o l i n z w a t e r f l c v on w a s t e t r e e t n e p t e q u i p m e n t c a p a b i l i t i e s .

You can p u t a n i o n - e x c h a n g e s y s t e r ! z t t h e e n d o f e a c h g l a t i n g t a n k . If y o u p u t i t a t t h e e n d - o f - t h e - p i p e , y o u a r e n ' t g o i n g t o g e t a n y t h i n g b a c k . A f t e r r e g e n e r a t i o n , you w i l l h a v e a mixed was te , a n d m o s t s t u d i e s s a y t h a t n i x e d was te s a r e s i m p l y n o t a n e c o n o m i c a l s o u r c e for r e c o v e r i n g n e t a l v a l u e s .

F i g u r e 4 i s a n EPA s l i d e s h o w i n g s c h e m a t i c a l l y v h r t a c o n v e n - t i o n a l d e s t r u c t s y s t e m l o o k s l i k e . You c a n s u r n i s c t h a t :

1 . I t c a n b e v e r y c o n p l i c a t e d . 2. I t t a k e s u p a l o t o f r o o n . 3 . I t p r o b a b l y c o s t s a l o t o f money. 4 . I t r e q u i r e s some p r e t t y good p e o p l e t o r u n i t . 5. You a r e l o s i n g t h e c h e m i c a l s t h a t y o u a r e h a v i n g t o

6. You a r e a d d i n g d e s t r u c t c h e m i c a l s . 7. You are g e n e r a t i n g a s l u d g e .

d e t r u c t .

D e s t r u c t t e c h n o l o g i e s a r e r e a l l y n o t t h e u a y t h a t you w a n t t o go . We a r e n o t s a y i n g t h a t t h e y d o n ' t w o r k , b u t i f n o t h i n g m o r e , y o u a r e c r e a t i n g a s l u d g e w h i c h i s h a z a r d o u s . Uho n e e d s i t ? T h e r e soon may be no l a n d f i l l s . Try t o a v o i d s l u d g e i f a t a l l p o s a i b l e l

A c r i t i c a l p o i n t t o e m p h a s i z e is t h a t when you n i x metal- b e a r i n g waste s o l u t i o n s a n d u s e a l k a l i n e p r e c i p i t a t i o n w i t h l i m e , h y d r o x i d e or c a r b o n a t e , a l l metels d o n ' t p r e c i p i t a t e

- 2 -

c o c p i e t c ! . : ~ a t t h e same !I!;. S o , i f y o \ : ! ]eve ;i c i x e d s t r e a m , y o u h a v e a p r o b l e n . You have t o u c e t n a v e r a z c 1)':. :<an; t i n e : t h a l e v e l s t i let y o u c a n n t t a i : ~ b y d c i n , : t h i s : i r ~ n o t q u i t c l o w e n o u g h . You c a n u s e L u l f i c i e ? r e c i p i t a t i o n ( l : i g . 5 ) , w h i c h r e s u l t s i n nuch l o v e r r e s i d u a l n e t a l i o n c o n c e n t r a - t i o n s . i!owever, n o t i c e t h c t o p r i g h t - h a n d c o r n e r o f I:icure 5 x h i c h s!iow3 f o r c o n ~ c r i s o i i t h e h y d r o x i d e p e r i ' o r T a n c e . l i o ~ ir.e!iy c f y o u r e a l i z e t h a t i f y o u r a i s e y o u r 25 t o c k i z h , ~ c n y ; : r e c . ' p i t a t e t i m e t a l s s o bscl ; i n t o s o l u t i o r ?

i o n a t t e r w h e t c p p r o a c l i y o u t z k e t o waste t r e a t x e n t , :{ou c o n a t all t i m e s i n p l e n e n t v e t e r - u s e r e d u c t i o r -- e v e t i if o n l y t o s a v e t h e d o l l a r v a l u e o f westea w a t e r and s e w e r use c h a r g e s .

You c a n m i n i m i z e y o u r d r a ! ; o u t v o l u n c . 3: w i l l S G o v e r t h a t v e r y b r i e f l y w i t h you a l i t t l e l a t e r t o s i i 0 . 4 you t h e ~ e t l i o d s t h s t c c n b e u s e d .

Ycu c a n i n p l e m e n t --------L c h e m i c a l r e c o v e r v . I n t h e c o n v e n t i o n a l r e c o v e r ; r t e c h n i q u e s , you e i t h e r r e t u r n ?, c o n z c n t r z t e 6 s o l u - t i o n t o t h e t z n k , d e s t r u c t t h i s c o n c e n t r a $ e , o r r e c o v e r n e t a l s f r o m E. c o n c e n t r o t c us in^ e l e c t r o l y t i c Ket'f.oc?s.

You c e n a l s o U S C i n t e q r a t e d t r e e t m e n t ( F i C . 6 ) . i c i s i s 3 d e s - t r u c t t e c h n o l c s y - w h e r e d r a g o u t z e n e r e l l y z o c s d o w n s t a i r s w h e r e i t i s t r e a t e d 2nd t h e c l e a n e d s o l u t i o n i s s e n t b a c k up- s i ; e . i r s f o r r e u s e i n r i n s e s .

I , . .

---I--vu- i l e s o u r c e R e c o v e r x n e n n s you r e t u r n c a t e r i a l s u n c h a n g e d d i r e c t l y t o t h e t a n k f r o n w h i c h t h e y w e r e d ragged . o u t . I t i s i r ; p o r t a n t t o c c n s i d e r t h a t r i h i l e y o u c a n p l a t e o u t r . e t a l s f r o n d r a g o u t s o l u t i o n s , a g a l l o n o f d r a g g e d o u t n i c k e l s o l u - t i o n , w o r t h a p p r o x i m a t e l y $ 4 . 7 0 , c o n t a i n s a b o u t 1 0 c)z . p e r g a l l o n o f n i c k e l . If n i c k e l meta l i s s e l l i n g f o r $ 3 e ? o u n d , a n d y o u can g e t $3 a pound f o r r e c o v e r e d n i c k e l , y o u ' r e o n l y r e c o v e r i n g a b o u t 602 of t h e v e l n e o f t h a t d r a g g e d o u t g a l l o n o f s o l u t i o n . The q u e s t i o i i a b o u t r e t u r n i n g i m p u r i t i e s t o t h e b a t h i s s e t t l e d by i m p r o v i n g b a t h m e i n t e n o n c e or i n c r e a s i n g c a r b o n t r e a t n e n t / c l e c t r o l y t i c p u r i f i c a t i o n f r e q u e n c i e s a s n e c e s s a r y .

I , l a t e r - u s e r e d u c t i o n ( F i g . 7 ) i s a c c o n p l i s h e d by comnon s e n s e a p p r o a c h e s . T h e r e i s o n l y o n e t h i n g t h e t r i n s i n g d o e s f o r y o u -- i t r e d u c e s t h e i m p u r i t i e s on a p l a t e d p i e c e t o t h e p o i n t w h e r e you c a n p r o g r e s s t o t h e n e x t s t e p a n d g e t a s a t i s f a c t o r y p r o d u c t . Why u s e more water t h a n y o u h a v e t o ?

I am s u r e t h a t y o u ' v e a l r e a d y i m p l e m e n t e d a l o t o f t h e s e . for t h o s e who h a v e n ' t t h o u g h t of e v e r y o n e , l e t ' s c o v e r them b r i e f l y :

- 3 -

F l o v S o n t r c l V,-.lves -- p i c t e r s l i k e t o o i i e n t h e i r \ l a t e r ~ e l v e s f u l l . P u t a : ~ O K ! c o n t r o l v z l v c on e a c h w e t e r l i n e a n a know y o u r flG!:.

----------_____----

A e r a t i o n o f H i n s e s -- w h e t h e r y o u pump t h e r i n s e s , b r i n g e i r a g i t a t i o n i l l , o r u s e n s y p h o n b r e a k e r , t l i c more a g i t a t i o n L O U g e t , t h e r lo re e f f e c t i v e i s y o u r r i n s i n z .

---_--____-_--

-----__ Countercurrentfiounterflow ,-,-,,,,,,---_~ R i n s i n r - i s n c c e ? t c a by j u s t a b o u t e v e r y b o d y t o d a y a s t h e sv.1r . r tes t \:ay t o g o . F i g u r e E shows wa te r c o m i n g i n t o c s i i ~ c l e s t a g e o v c r f l o i r i n g r i n s c t a n k . T h a t i s t h e vc;’ i t was f o r y e a r s a n d y c a r s . F i g u r e 9 s h o v s a d o u b l c F o u n t e r - f l o w r i n s e t a n k v n e r e t h e s a n e a n o c i i t o f x c t e r u s e d i n t h e s i n z l e r i n s e tan!: now f e e d s t:ro r i n s e t a n k s . So, y o u h a v e t u o f o r t h e p r i c e o f o n e .

i ’ i g u r e 10 shows wc te r f l o w s r e q u i r e d f o r e a c h ~ a l - l o n o f d r a z o u t t o a t t e i r . t e n p a r t s p e r : : i l .Liox i n t h e f i n a l r i n s c . The n u n b e r s a r e v c r y s - c r i k i z g . I O U c a n r e d u c e 63-852 by goin;: t o :i 6cu’ol.e c o u r . t e r / c u r r e n t r i n s e s n d ?0-47% by ; o i n g t o a t r i p l e . : l o s t p e o p l e f e e l t h a t a n y t h i n c beyond 2. t r i p l e i s r e z l l y n o t b u y i n g y o u a n y t ? i i n z . T h a t i s u p t o y o u w h e t h e r you c a n a f f o r d t h e e x t r a l a b o r o f g o i n g t o f o u r . F o u r i s b e t t e r t h a n t h r e e , b u t c c n y o u a f f o r d t h e e x t r a s t e p p r o d u c t i o n w i s e ?

.-

C o n d u c t i v i t y C o n t r o l l e r s -- T!:ese d e v i c e s n l l o l ~ water t o f l o u i n t o t h e r i n s e t a n k when t h c wcter i s d i r t y , and. s h u t w a t e r o f f ~ ! i c n t n c r i n s e i s c l s e n . T h a t i s t h e o n l y r e a s o n y o u h o v e r u n n i n g r i n s c s -- b e c a u s e t h e water i s d i r t y . I f t h e water i s c l e a n ,

d o e s n ’ t make sense at a l l . I f you c a n r e u s e c o o l - i n g water , t h a t ’ s g r e a t b e c a u s e i t i s w a t e r y o u h a v e p a i d f o r , a n d i t can do a s e c o n d j o b .

----

why h a v e ? u r e water c o n t i n u a l l y f l o w i n g . I t

3 i n s o T i u e r s -- \,‘hen work e n t c r z t h e r i n s e , t h e o p e r a t o r j u s t h i t s a s w i t c n , w a t e r f l o w s f o r a f i x e d t ime, a n d t h a t i s that. T n a t i s n o t q u i t e a s s o p h i s t i c a t e d a s a r i n s e c o n t r o l l e r , b u t i t works. You c a n l i m i t your w a t e r u e a ~ c a n d g e t good r i n s i n g .

You can r e c i r c u l a t e t r e a t e d r i n s e s if y o u h a v e a b a c k l o g of t r e a t e d r i n s e . You can -have t h i s wa te r i n a - h o l d i n g t a n k a n d pump i t b a c k .

- 4 -

OEen-ended i i o s c s -- I f on:; of ' y o u h a v e h a d a tnnl: o v e r f l o w w h e n sornebod;,. i s f ' i l l i s c i t ?t, t h e er,d o f t h e c a y , :vou know t h e p r o b l e m . I f y o u u s e 8 spr inL-- ioadec l h o s e n o z z l e , y o u e l i n i n a t e p o t e r , t i e l p r o b l e n .

- --------------

D o n ' t w a s h down s n i l l s . U s e 311 a c c o r b c n t n a t e r i e l . S a v e e n a w f u l l o t o f w a t e r . You a r e s t i l l g o i n g t o h a v e t o wash down n t t h e e n d oi ' t h e d a y t o r e x o v e s t a c n n n t w a t e r t h a t l a y s u n d e r t h e f l o o r b o e r d s . i l o w e v c r , i f y o u h a v e a s p i l l , t h e r e ice no s e n s e i n d o i n g a n y t h i n c e x c e p t u s i n g a n c b s o r b e n t n a t e r i z l .

--------------c----

Check y o u r t a n k s e n d make s u r e t h c t t t h e y a r e n o t ---- l e a k i n c ; y o u c a n l o s e a l o t o f c o l u t i o n . I n t h e d a y s o f water s h o r t a g e s t h e y u s e d t o mrI! a b o u t , "One d r o p p e r m i n u t e " f r o m d r i p p i n g f a u c e t s . I t i s t h e same t h i n g w i t h a p l a t i n g t a n k .

----- d i n i n i z i n f : D r a s o u t V o l u m e ( F i C u r e 11 ) - - I f ' you c a n k e e p s o l u t i o n i n t h e t a n k , i t i s n ' t a n o l l u t a n t , a n d you d o n ' t n e e d waste t r e a t m e n t . 5 h a t you c a n ' t k e e p i n w i l l n e e d t o b e c l e a n e d . u p by s o u e c o n v e n - t i o n a l t c c h n i q u e ( s ) .

If you r a c k a p a r t p r o p e r l y s o t h a t i t d o e s f i ' t d r a i n o n t o t h e p a r t b e l o w , d r a i n a g e w i l l b e n o r e e f f e c t i v e .

I i t r i p T i m i n z -- F i g u r e 1 2 s h o w s t h a t i f y o u c a n f i t i t i n t o y o u r p r o d u c t i o n c y c l c , a 1 5 s e c o n d d r i p t i n e w i l l r e m o v e a l l y o u r s o l u t i o n t h a t i s g o i n ; t o d r a i n o f f .

You c a n u s e n o n - i o n i c w e t t i n g . a r e n t s , w h i c h w i l l n o t c o n t r i b u t e a n y f o r e i g n i o n s t o y o u r p l a t i n g b a t h . T h i s w i l l r e d u c e s u r f a c e t e n s i o n a n d r e d u c e t h e a m o u n t o f d r a g o u t o n e v e r y p a r t t h a t I s w i t h - d r a w n f r o m a p l a t i n g t a n k .

You c a n p u t d r a i n b o a r d s b e t w e e n t h e t a n k s t o k e e p s o l u t i o n o f f t h e f l o o r a n d r e t u r n e d t o t a n k s .

You can r e m o v e y o u r N t s s l o w l y a n d s m o o t h l y . If y o u w i t h d r a w them s l o w l y , y o u ' l l f i n d t h a t y o u h a v e much l e s s d r a g o u t t h a n when y o u pull t hem o u t q u i c k l y .

FOR r i n s e s a n d a i r k n i v e s g e n e r a l l y l e n d t h e m s e l v e s ' more t o a u t o m a t i c p l a t i n g t h a n t o r a c k p l a t i n g a n d

r e c o v e r o. g o o d a m o u n t o f d r a g o u t .

---

- 5 -

--------__-_____- Iiaclc r a i n t c n a n c e -- !;any p e o s l c l o s e s o l u t i o r b e c u u s c t h c i r r a c k s e r e f a l l i n [ a p a r t . You c c n a l s o r u i n b a t h s d u e t o c r o s s c o n t a c i n ~ . t i o n c a u s e d o j y

d e r ' c c t i v e r a c k s .

I f y o u c a n u s e a ,Y------,--&,,,--_-~ h i r h e r b a t h t e m p e r a t u r e :rou r r i l l r e d u c e t h e v i s c o s i t y a n d r e d u c e t h e d r a g o u t . ',!it12 mos t n i c k e l t a n k s i t d o e s n ' t riake much d i f f e r e n c c if y o u r a i s e t h e t e r 9 e r a t u r - e u n l e s s ; rou h a v e b i c p a r t s t h a t f l e s h d r y e n d s t a i n 2 s y o u p u l l t h e n o u t .

Use l o v e r c o n c e n t r a t i o n b a t h s i f you cac . You h e v e s e e n t h e l o w n i c k e l b a t h s t h a t c u t t h e n i c k e l c o n - c e n t r a t i o n d u r i n g t h e d a y s o f t h e e n e r g y s h o r t r z e v k e n y o u h a d t o go t o l o w e r o p e r a t i n g t e n g e r a t c r c s on y o u r b e t h s .

---------

I h e v e s e e n some d r a g o u t f i g u T e s p u b l i s h e d by E P f i , t y ; i c a l l y , 1 . 5 g a l l o n s p e r 1 ,000 s q . f t . fly e x p e r i e n c e i f i d i c n t e s t h e t t h c f i g u r e s call be c l o s e r t o 4 ~ n l 1 o r . s p e r 1 , 0 0 0 sq. f t . f o r r a c k ; > l a t i n g a n d e v e n h i g h e r f o r b a r r e l .

F i g u r e 13 s h o w s d r a g o u t d a t a f r o n a l a r g e ? l a t i n G s h o p a t t h e e n d o f o n e s h i f t . I t h i n k t h e y a r e i n p r e s s i v e b e c a u s e t h e y show g r a p h i c a l l y t h e p e r f o r m a n c e o f d r a g o u t t a n k s .

On t h e r a c k n i c k e l t h e f i g u r e s i n p a r e n t h e s e s n e a n t h a t t h e two n i c k e l t a n k s , e a c h v i t h t r ro d r a g o u t s , were f o l l o w e d by a common D r a f o u t ;;3 a n i D r a c o u t : ; 4 . C o n t e n i n e g t l e v e l c a c e aorrn t o 1 . 5 p a r t s p e r z i l l i o n i n t h e f o u r t h c o n c o n n i c k e l t a n k .

,

F r o n t h e r a c k c o p p e r d a t a y o u c a n s ee t h a t h a v i n g f o u r d r a g o u t s b r o u g h t c o p p e r c o n t a m i n a t i o n down t o h a l f a p a r t p e r m i l l i o n .

Now w e a r e g o i n g t o c o v e r t h e f i n a l i t ems , n a m e l y t h e r e c o v e r y t e c h n i q u e s t h a t w e h e v e f o u n d t o be s u c c e s s f u l . We, of c o u r s e , h a v e a d d r e s s e d t h e c o n v e n t i o n a l r e c o v e r y t e c h n o l - o e i e s . T h e y a r e a l l f i n e ; t h e y a l l w o r k , b u t t h e y h a v e a p r i c e ; w h e t h e r i t b e i n manpower , e n e r g y , s p a c e , o r s l u d g e .

I n a d d i t i o n , s o n e c o n v e n t i o n a l r e c o v e r y t e c h n i q u e s ( E l e c t r o - l y t i c , I o n - E x c h a n g e , and C a r b o n A d s o r p t i o n ) r e c o v e r o n l y p a r t o f t h e v a l u e o f t h e d r a g g e d o u t s o l u t i o n . B r i g h t e n e r s , wet - t e r s , c h e m i c a l a d d i t i v e s , and meta l f a b r i c a t i o n c h e r g e s a r e n o t r e c o v e r e d .

L

- 6 -

:.!it11 X e s o u r c e I lecovcr;r :;ou r e iu : -n e l l o f t h e r l r t c r i e l v a l i : e s t h e t :iou p a i d f o r . I ~ i ~ l e m c c t ~ t i o n o f {I:: e f f e c t i v e r e c l e r i a t i o n pro&rac! r e q u i r e s :

1 . D r a g o u t t a n k s on a l l c o n t a m i n a t i n g g r o c e s s e s . D r a g o u t i s r e t u r n e d t o t h e o p e r a t i n g t a n k n u t o c a t i c a l l y t o r e F l c n i s : . ? e v a p o r e t i o n .

2 . !;’urn a n d / o r e c i c ? i f i c i r i n s e s ( o r f o c c p r c y ) t o e f f e c t i v e - l y remove con tnminr . ! i t s from p a r t s .

3 . k c l o s e d - l o o p c o u n t e r f l o w r i n s e t o f e e d b e c k t o t h e drag- o u t t a n k .

4 . The u s e o f s o 3 e t e c h n i q u e t o r e d u c e b a t h vo lume o f r o o c t e m p e r a t u r e b a t h s . T h e s e i n c l u d e : f o r c e d e v a p o r a t i o n , a e r a t i o n , o r a c o m b i n e t i o n o f t a n k o v e r f l o w a n d evapora- t i o n .

T h e s e t e c h n i q u e s r e e u c e a n d c a n e l i n i n a t e t h e n c c d f o r c o n - v e n t i o n 2 1 waste t r e a t m e n t . I n t h o s e i n s t a n c e s v h e r e t h e a b o v e t e c h n i q u e s e l o n e c a n n o t k e e p up r r i t h c o n t e u i n a n t s , e l e c t r o - l y t i c t e c h n i q u e s c a n be e d d e d t o t h e d r a g o u t ( s 1 , a n d i o n - e x c h a n g e c a n be added t o t h e c l o s e d l o o p c o u n t e r f l o w r i n s e s .

U i t h a t t e n t i o n t o d r a g o u t f r o m a c i d p r o c e s s e s , i t is o f t e n p o s s i b l e t o a v o i d p!i’ a d j u s t n e n t o f a n e f f l u e i i t s t r e a n .

- 7 -

FIGURE 1 -- CONVENTIONAL DESTRUCT TECHNOLOGIES -- - _I

1. ALKALINE PRECIPITATION 2. SULFIDE PRECIPITATION 3. CYANIDE OXIDATION 4 . CHROMIUM REDUCTION 5. BOROHYDRIDE PRECIPITATION 6. STARCH XANTHATE 7. FKJA FORMALDEHYDE PRECIPITATION 8. CHELATE DESTRUCT

FIGURE 2

CONVENTIONAL RECOVERY TECHNOLOGIES

1 . ELECTRODIALYSIS 2. REVERSE OSMOSIS 3. EVAPORATIVE RECOVERY 4 . ELECTROLYSIS - DC/PULSE PLATE 5. CARBON ABSORPTION 6. ION-EXCHANGE

- 8 -

1 1 ’1

.. ‘1 :-I, .. . .

n 11

L ‘ I 3

FIGURE 3

STREAM SEGREGATION

1. CYANIDE-BEARING RINSES 2. CHROMIUM-BEARING RINSES 3 . ACID-ALKALI NON-CHELATED RINSES

(WON-CYANIDE, NON-CHROME) 4 . CHELATED RINSES 5. STRONG DUMPS OF EACH ABOVE 6. STREAMS NOT REQUIRING TREATMENT

- 9 -

--.--

I

FICATION CHROMIUM REWCTION

7 Polymor

U A I U U C I I I V I I

- ,

Electropi .

Logond: s = wltorutor c = chlonrutor

ORP oxidation reduction ootontirl CYANIOE I Y . - I - . - L .

lsting industry Conventional Wastewater Treatment

REPRODUCED FROM ENVIRONMENTAL REGULATIONS AND TECHNOLOGY

EPA 625/10-80-001, AUGUST 1980, p e 13.

- 10 -

I 1

I1

11 I 1

I/ I/ I1 ii l l 11 I 1

11 1 1

I/ I 1

I 1

l l

I 1

FIGURE 5

Solubilities of Metal Hydroxides and Sulfides as a Function of pH

2 3 4 6 6 7 8 9 1 0 1 1 1 2 1 3

PH

Not~.--ckn.d ~ M J kr motmi atdidw baed on orwurwntml timu l m t d m S.id.lrr rd8hiIici.r.

R E P R O D U C E D FROM: C O N T R O L A N D T R E A T M E N T TECHNOLOGY FOR THE

M E T A L F I N I S H I N G I N D U S T R Y EPA 625/8-80-003, A U G U S T 1980, p * 3

- 11 -

--I- FIGURE 6

WEM . . L.

Integrated chemical rinse.

-

ENT

REPRODUCED FROMt IN PROCESS POLLUTION ABATEMENT -0 UPGRADING METAL FINISHING

FACILITIES TO REDUCE POLLUTION

EPA 625/3-73-002, JULY 1973, pa 30.

11

- 12 -

FIGURE 7

WATER USE REDUCTION

- FLOW CONTROL VALVES - AERATION/AIR AGITATION/PUMPING - COUNTERCURRENT RINSING - CONDUCTIVITY CONTROLLERS - REUSE COOLING WATER - RINSE TIMER - RECIRCULATE TREATED EFFLUENT - REUSE ACID RINSES AFTER ALKALINE CLEANERS - NO OPEN-EIDED HOSES - CLEAN UP SPILLS WITH ABSORBENT - NO WASHDOWN - INSPECT FOR LEAKING TANKS, VALVES, ETC. (SPRING-LOADED HOSE NOZZLES)

I J - 13 *

REPRODUCED FROM: IN-PROCESS POLLUTION ABATEMENT, UPGRADING METAL-FINISHING

FACILITIES TO REDUCE _OLLUTION

- 14 -

1 1 :1

3 :I [1

3

.

REPRODUCED FROM: IN-PROCESS POLLUTION ABATEMENT, UPGRADING METAL-FINISHING

FACILITIES TO REDUCE POLLUTION

EPA 625/3-73-002, JULY 1973, pa 27.

- 1s -

RINSE RATIO

REDUCTION OF FLOW - I N MULTIPLE RINSE TANKS

---

- PERCENT REDUCTION OF FLOW NO, OF TANKS

11

1 - - 2 3

100 0 90 95

1,000 0 97 99

10,000 0 99 99.8

,

- 14 -

1 n

F I G U R E 2

n

1 1 3 I] 3 11

3 3 1

I 3

MINIMIZING DRACOUT VOLUME

- PROPER RACKING - DRIP TIMERS - WETTING AGENTS - DRAIN BOARDS - REMOVE PARTS SLOWLY - FOG RINSES - RACK MAINTENANCE - INCREASED BATH TEMPERATURES - LOWER CONCENTRATION BATHS ,

- 17 -

11

F I G U R E 12

rYPlCAL 0RAG.OUT CURVES

(3 SECONOS)

-

(15 SECONDS) + DRAG-IN

SOME HORIZONTAL

SURFACES

BENT SHEET

VERTICAL SHEET L 20 40

SECONOS

1 1

- ..

- 18 - . Y

1 1

- ’3

. 1

:.I

FIGURE 13 -

DRAGOUT DATA

BARREL NICKEL

D.O. #1 . . . . . . . 12,800 mg/l Ni D.O. # 2 . . . 49040 mg/l Ni

RACK NICKEL

D.O. #l 1,100 mg/l Ni . . 1,640 mg/l Ni

D.O. AI2 220 mg/l Ni . . . . . 368 mg/l Ni

COMMON D.O. #3 70 mg/l Ni

COMMON D.O. #4 1.5 mg/l Ni

BARREL COPPER

D.O. #l . .. . . 6,100 mg/l Cu D.O. #2 . . . 1,720 mg/l Cu

R A C K COPPER

D.O. #I . . . 740 mg/l Cu D.0. #2 . . . . 110 mg/l Cu D.0. #3 . . . * . 18 mg/l Cu D.O. #4 . . . 0.4 mg/l Cu

- 19 -

Appendix 2

TANK MANAGEMENT AND MINIMIZING DRAGOUT AND RINSES

by Tim Greiner, MA OTA

1 n -1 I 3 c 1 n

.‘1 ‘ I ’ 3 3 I1 !. 1 I d 3 J 3

n

Dragout Management Z q & Jdb4 de+ ,

- bath redacement treatment disposal total

cu $1.75 $0.75 $0.50 $3.00

Ni $3.60 $0.90 $0.75 $5.25

Cr $2.40 $1.10 $1.00 $4.50

Strategy:

1.

2.

3.

reduce dragout

collect and return dragout

reclaim what cannot be collected

AQUEOUS ! r

II Table 8. Drag-out for Various Rack Configurations Item Vertical park, well drained

Vertical park, poorly drained

Vertical parts, very poorly drained

Horizontal park, well drained

Horizontal parts, very poorly drained

Cupshaped parts, very poorly drained

s4urcc: Dumey,1984.

- I

2 0 ll

h e o u t . na1/100 ft2

0.4

4.0

0.8

10.0

8.0 to > 24.0

I Table 9. Flow Rates for Five Riwing Systems I System

Singie 10.0 I Two rinses in series, equal flow of fresh rinse water to each tank

Three rinses in series, equal flow of fnsh rinse water to each tank

Two counterflow rinses, fresh water feed to second tank only

0.6

0 3

0 3

0.1 Three counterflow rinses, fresh water feed to thud tank only

source: Durncy,1984.

< I 1. Reduce dragout

O

O air knives pull part slowly from plating tank

spray or fog rinse over plating tank minimize metal concentration in plating bath use drain boards between tanks use drip bars to hold parts over plating tank

1 3 n 1

0

' . -I

FIGURE '5 Dragout

3

Dragout

PLATING 8ATN RWSL TANK

Drip Board Rating Type of Drip Board Rating

Unacceptable (Without d r i p board)

Sat lsf a c t o t y

. ..... Des l r a b l e

I1

3. Reclaim what cannot be collected

1. Waste exchange

2. Metal recovery via electrolytic, evaporative or ion exchange means.

3. Metal hydroxide precipitation

2. Collect and return dragout

Each dragout tank reduces the rinsewater contaminant concentration by %50.

Return dragout to the plating tank to make up for evaporative losses

Impurities

(SIDE F VIE21

Inscallaclan of a S m a l l Dragout Tank

Counter-current rinsing:

Conserve water use and reduce wastewater treatment

Water flows in a direction counter to the flow of work. costs.

two counter-current tanks: 90-97% water reduction. three counter-current tanks: 95-99% water reduction.

Three Stage Counter-Current Rinse Tank

EX: Ni bath: 270,000 mg/l ids : final rinse: 40 mg/l tds

number of tanks: 1 2 dilution required: 6,750 82.

3 18

Cost-savings: 6 to .6 gpm @ $3.2/1000 gallons = $2,10O/yr.

Reactive Rinsing:

Reuse of contaminated rinse water to conserve water and chemical use.

FIGURE 3 Dangerous Mlsapplfctlon of Reactive R i n s i n g -

. .

1 n

A

DISSOLVED SOLIDS

1

4

DISSOLVED SOLIDS

CATION MEMBRANE

ANION MEMBRANT

3

a 3

Q-

I I I I

I I

I @A I I

I

-0

t RECOVERED SALTS

R I N S E W T E R Q U A L I T Y G U I D E L I N E S

Loca t ion /Opera t r o n Concenc ra t ion

Rinse follovrng CuCl e t c n and p r i o r t o strip

R i n s e f O l l O W i n g a l K t a l i n e c l e a n and p r i o r t o pickle

R i n s e f o l l o w i n g ac id p i c k l e a n d p r i o r to a c i d p l a t e

R i n s e f o l l o w i n g a l k a l i n e clean and p r i o r t o Jr-\ ' inq

Illaximum copper c o n t a m i n a t i o n of r e s i s t s t r i p

A l l O U a D l e f l u o r i d e c o n t a m i n a t i o n of hydrochforrc p i c K l e

R i n s e f o l l o w i n g a l k a l i n e etch r e p l e n i s h e r r i n s e

A l l o w a b l e C a u s t i c (NaOH) i n rinse(s1 f o l l o w i n g r e s i s t s t r i p

F i n a l r i n s e f o l l o w i n g e l e c t r o l e s s coppe r p l a t i n q

F i n a l r i n s e s - g e n e r a l

R i n s e a f t e r n i c k e l (Or Copper or any other heavy mecall

R i n s e a f t e r c y a n i d e

R i n s e a f t e r a l k a l r n e c lean and p r i o r t o a l k a l i n e t i n p l a t i n g

40 mg/l - Total -

Recommended Contaminant

140 mg/l Cu

375 mg/l - Tota l con taminan t s

350 mg/l - 1st s t a g e 5 mg/l - 2nd s t a g e

25 mg/l

2-400 mg/l - Total conta in inants

40 mg/l - Tota l

7 , 5 0 0 mg/l - T o t a l

4

14 71C

Rinsetank Design: I

3 8 . ”1

3

Ensure water is completely mixed to eliminate feed short circuit and use entire tank volume.

Wort

P r o p e r Rinse Tank Design

feed distribution line ($30) air agitation ($60) flow control valve ($25) o r conducticfity controller (SSOO)

a ...

' - 7 I I I I I I I I I I

- A

G w t. 4 3

c

& pc

M C d C 4 al 4 V

u d tn 4 m

f

I L

-7 I I I I 1 I i I I I I I I

- A I 1

11

11

a ' . . * *; I.' .

/.

5.. ,: ' . . .; . _. ..- .. .

. . ' . 1

';" .., 7. , . , . . . . . . :.-..:... .. . . .. .. . . .

Industiiai Ma%eriaIs Fifth Edition

N. IRVING SAX Assisted by:

Marilyn C. Bracken/Robert D. Bruce/Willlam F. Durham/Benjamin Feiner/ Edward G. Fitzgerald/Joseph J. Fitzgerald/ Barbara J. Goldsniith/John H. Harley/

Robert Herrick/Richard J. Lewis/James R. Mahoney/John F. Schmutzl E. June Thompson/Elizabeth K. Weisburger/David Gordon Wilson

VAN NOSTRANO REINHOLD COMPANY NEW YORK CINCINNATI TORONTO LONDON MELBOURNE

TABLE 2.8. Plating. Metal Finishing and Cleaning. and Allied Processes

a

N

Rateof Hood Toxic or Operation Contaminant Flammable Rating Evolution Type Comments

Chrome ploiinr

Cyanide ploring I

(a) Brass-bronze (b) Zinc (E) Copper (other than

conveniionrl) (d) Gold, s i l v e ~ . cadmium,

conveniiond coppcr

Strike (coppcr and 8 i b C f

A c i d ploring (a) Copper (b) Nickel 1 hydrofluoric

acid) (c) Tin (halide bath) (d) Zinc (chlimde bath) (e) Nickel (sulfate and

chloride) ( I ) Tin and zinc (sulfate)

Nuoborore phring (a) Lead (b) Lead-tin. nickel. tin

cadmium. copper. zinc

&lrrrrolc.ts ropptr Anofking.

(a) Chromic acid (b) Sulfuric acid

(a) Brass, bronze. copper (b) Allother

Ekrrropolish

Chromic acid mist

Cyanide and alkali mist Cyanide and alkali mist Cyanide and alkali mist

Cpanidc and alkali mist

S ~ l l u i i c acid mist Hydrogen fluoride gas

Halide mists Chloride mists

Fluoborates. hydrogen fluoride gas Fluoboratc mist

Formaldchydc gas

Chromic acid mist Sulfuric acid mist

Acid mists. arsine Acid mists, arsine

Alkali mists ' . Hydrogen chloride gas

High

Slight Slight Slighf

Slight

Slight

Slight High

Slight Slight

-

-

High Moderate

High

High Slight

l l igh High

Slight High

. ... . . ... .

High

Low Low Low.

Nil-Low

Modcrate

Nil- Low Low-modcrate

Moderate Low -

Low Low-moderate

4

4 4 4

4

4

4 4

4 4

- - i, 4 4

High 4

High 4 Moderate- high 4

Low 4 Moderate 4

High 4 Modcrate 4

=izk

.- b

Hydrogen and oxygen released-possible cx- plosion hazard with roam blanket .

Local exhaust not usually necessary . . . - ._ .. . .

Local exhaust not usually necessary hiagnesium base metal

Local exhaust not usually ncccssary. cthcrwise see Zinc (chloride k t h ) ab&

'

- . ? i

. I 7 ' - . - . , L

-f <'

*- i .

High toxic rating because of arsine possibilit) High toxic rating because of arsine possibilit)

:r. ,. , ':

. : I

. , . . - I... .. . .

., - ; .- . I . . ' I . -.

I p i c :. hig' 'raiin-:'

"Black Magic." "Ebanol." etc. ,

Hood No. I or J(c) rccommcndcd ? Slight High

High Moderate-high (b) Alkaline oxidizing (c) Stainku steel ducaling

(a) Aluminum-nitric acid (b) Aluminum-chromic acid (c) Aluminum-sodium

hydroxide (d) Copper-sulfuric acid

(hydrochloric. sulfuric

(I) Strinlu, steel-nitric acid

Picklinj

- (e) Iron. stccl. nickel

' acid)

Alkali mists Nitric. sulfuric. hydrochloric acids

- . . ' . . . .:

Hood No. I or 4(c) recommended tiigh Moderate

Slight Moderate- high

Slight Low-moderate High Moderate- high

thgh Low Oxides of nitrogen (gas) Chromic acid mists Alkali mists

SulCuric acid mists Hydrogen chloridc gas and

Oxides of nitrogen (gas)

sulfuric acid mist

Passivation. immunization. hood No. I or 4(c) recommended

Hood No. 1 or 4(c) recommended .' a .

- . .

High Moderate

Acid dipping (a) Bright dip-copper. brass,

(b) Zinc-hydrochloric acid

(8) Hydrochloric acid (b) Sulfuric acid (c) Nitric acid (d) Hydrofluoric acid (e) Chromic acid (f) Sodium hydroxide (a) Ammonium hydroxide

(8) Vapor dcgrcasing (b) Alkriine ckaning (c) Emulsion cleaning

bronze, aluminum

. Stripping ogfnu

Metal cleaning

(petroleum and coal tar solvents)

(d) Emulsion clerning (chlorinrted hydro- carbons)

tligh Modcratc-high

High Low

Oxides of nitrogen. sulfuric acid mist Hydrogen chloride gas

Thew items refer to thc stripping of a plated coating from a base metal. The usual stripping agents and rates of evolution are shown. For mixtures ofthe agents. the component with the more stringent requirc- mcnt i s the basis of design.

. '

. . .

. . . . . . , , .*- .! . .

. I-

The lower rate of evolution i s for cold baihs. the higher for heated or air agi- ta:cd baths

High Low-moderate Slight Low-moderate High Modcratc-high

High Low-moderate Slight Low-moderate High Low-moderate

High Low-moderdlc

Hydrogen chloridc gar Sulfuric rcid mists Oxides of niirogen Hydrogen fluoride gas Chromic acid mists Alkali mists Ammonia gas

See Dcgreasing (this section) Alkali mist Solvent vapors

I

Slight Moderate-high Slight-moderate Low-high

Moderate- high Moderate-high Chlorinated hydrocarbon vapor

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1 . .- 0.

82 SECTION 2

TABLE 2.9 Miscellaneous Operations

Type of Air TOXIC or Cleaner (% .*,&

: <w .r,r - Flrmmrble Rate of Hood Industrial

Type Comments AU Cleaners) Contaminant Rating Evolution -_ Operation

Dipping and drying (a) Paint and enamel

(1 ) Dipping ( 2 ) Draining ( 3 ) Air drying

Vapors of petroleum naphtha, and possibly xylene

Slight-High Slight-High Slight-High

High High High

Slight-High

Slight-High

Low-High Low-High Low-High

Hood No. I or 4(c) recommended See also Dilution . Ventilation, this section

Hood No. I or 4(c) Recommended See also Dilution Ventilation, this section

Hood NO. 3 may consist or the entrance to a drying tunnel. Hood No. 6 as ciow as possible 10 ?prr:ion. Hood NO. I to enclose the operation as much as possible. Ventilation mvst also take into account explosive concentrrtions. See also Dilution Ventilation. Fire Safety. Hood No. 6 as close as possible to pot. Products or combustion to be vented to hood or independently.

Hood No. 2 to be shaped to suit operation, if possible 4 in. maximum from tool.

(b) Lacquer (1) Dipping (2) Draining (3) Air drying

flow coating (a) Doctor blade

Vapors of naphtha. esters. aromatics

High High High

Moderate-Hi& Vupors of naphtha and xylene

. .

(b) Deluge Vapors of naphtha and xylene

Moderate-High

. d d

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Melting Slight-High High Metal fume. gases Cloth filters. electrostatic precipitator, hi& efficiency scrubbers (30th fil1crr. elmrmtat ic precipitator. rblolw filter. High efficiency cyclone, cloth filter

Toxic metal machining High

Slight-High

Moderat tHigh

High

Metal dust

Portable grinding, chipping, snaggtng

Garages (a) Local tailpipe

exhaust

Metal, abrasive and possibly silica dust

Carbon monoride. aldehyde, etc.

High High Hood or open pipe end to Not usuauy needed fit over tailpipe.

Vehicles up to 100 hp-IWcfm Vehicles above 100 hp-2Wcfm Diesels-400 cfm 10,OOO clm per running auto 20.W cfm per running truck 200 cfmihp per running diesel Amine vapors can cause contact dermatitis. Hood needed No. I preferable. Ventila- tion must also maintain

CFM per Branch

Ne! usually

(b) General Carbon monoxide. ventilation aldehydes, etc.

Epoxy mixing. p-~t~ing. Vapors a l amine,. etc. styrene, etc.

High

Hi&

Varies

Low-Moderate

required flow at operator's hands.

j j

Substitution material. readily disassembled for cleaning. Smooth piping with a minimum of bends should be used. Floors should be well drained. smooth, and coated with an im- pervious material such as epoxy or polyurethane paint. Completely enclosed reactors and kettles and similar equipment. remotely controlled and automatic processes, and chemical or physical modification of the carcinogen are examples of control by design.

Relief and breather vents must discharge to an exhaust system or air cleaner and not-into the workroom. All carcinogenic operations must be performed in separate rooms or bui1d;ngs used exclusively for these operations and ventilated to maintain negative pressure. Designation of such work places as regulated areas into which only properly protected workers are permitted to enter will limit the number of workers exposed.

Substitution of a non-carcinogenic chemical. when possible, will obviously eliminate exposure. However, this approach must be used with extreme caution. Sub- stitution. especially of a highly toxic non-carcinogen or one of unknown toxicity, may create a false sense of se- curity and lessen attention to strict controls. In addition, substitution may result in a mixture of non- carcinogens which is carcinogenic.

Enclosure and isolation

Particularly hazardous processes within a regulated area can be completely enclosed and ventilated at negative presssure. and operated by remote controls or by a fully protected worker who enters the enclosure only-

"

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TABLE 2. IS. Emissions (Conrinuetl)

. \-

, , . . . . ,. ' . I ' : . .. .. . . . . . . . . . . . . . . . . Industry, Operation, or Process Emissions . .':

;:,.. :,. , . . . 0 , O l J.b i tOO.5 : ' a ' . * . . . . t : , . - . . ,

,, . . . , c . . . 72 Condenser Calciner

INDUSTRIAL AIR CONTAMINANT CONTROL 113

Perlite furnaces Petroleum refineries

Phosphate fertilizer manufacture Normal superphosphate

Grinding, drying Main stack

Triple superphosphate Run -0 f - p il e Granular

Dryer, cooler Ammoniator-granulator

Diammonium phosphate

Phosphoric acid Wet process

Reactor Gypsum pond Condenser

Thermal process

Phthalic anhydride (overall plant) Pipe coating (asphalt or coal tar) Plastics manufacture

Polyvinyl chloride

Polypropylene

General

metal cleaning, etc. Plating, anodizing, etching, pickling,

. ,. ,. .*.: ;::-;. . :' ' , . ' 2 , '

' * - 21 Ib particulates per ton of charge . . ' . . . ..::';-' Petroleum refinery emissions vary ,very !widely ,both . quantitatively and qualitatively. The data do not lend themselves to inclusion in a general table of this type .... .. See the references. . . (pounds per ton of product)

0.15 fluorides

0.03 fluorides7 0.10 fluorides -

. . . . . . 1. . . . . .. .:?? i;:. I.:, .

I . . . '

9 particulates

80 particulates 2 particulates

0.04 fluorides (pounds per ton of product)

18 fluorides I fluorides

20 fluorides 1-6 particulates depending on the degree of air

cleaning which is present in all thermal , process plants

32 Ib organics per ton of product IO Ib particulates per ton of coating material

(pounds per ton of product) 35 particulates 17 gases and vapors 3 particulates

0.7 gases and vapors 5-10 particulatu

Emissions depend on rate of evolution of contaminants from the tank surface. (See Rate of Evolution column in Table 2.8) Emissions can be expressed as a per- centage' ot the weight of make-up chemicals added. .

Rate of Evolution % Loss

. . ..

High - Moderate

LOW Nil

5 % 3 2 0

Polishing and buffing Printing ink manufacture

Vebicle cooking General oils Oleoresinous Alkyds

Pigment mixing -

Raw material dryer . Raw material crushing Melting Curing oven Molding and shakeout

Refractories ( castable)

Rubber compounding Soaps and detergents

0.0054.01 grains per cubic foot of exhaust air

(pounds emit ted/uni t indicated ) 120 gaseous organics per ton of product 40 gaseous organics per ton of product I50 gaseous organics per ton of product 160 gaseous organics per ton of product

2 particulatu per ton of pigment (pounds particulatu per ton of feed material)

30 120 50

0.2 25 0.5 Ib particulates per hour of operation

..

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PMF INC. NICKEL RECOVERY PROJECT

Submitted to : The Connecticut Hazardous Waste Management Service

For futher information contact : PMPC INC.

Palisades Park, New Jersey

. . .. .~ * , , . ., . . , . . , . . . . ,. . ' .

PMF NICKEL RECOVERY

The Basic goal of project P500 was to find a more effective way to treat the 65 to 100 gallons of nickel bearing dragouts from our plating line. The original method used was to precipitate the nickel metal to a nickel hydroxide and allow it to settle. Every night the nickel hydroxide had to be transferred to.settling tanks, where the ph was adjusted, and the nickel was allowed to settle overnight. Though this method had been effective for us in the past as a means of reducing total volume of nickel-bearing solution, it did nothing to reduce the nickel metal. We still had a large volume of nickel hydroxide sludge to send'out for reclaim and were at the mercy of the law of gravity to wait for the nickel hydroxide to settle. Method number 1 below shows a typical daily nickel settling procedure.

Method # 1 ( The old way of precipitation ) 1. Transfer 100 gallons to settling tank 2. Add aprox. 10 lbs. sodium hydroxide 3. Stir, check ph. ( must be between 9.5-11.0 ) 4. Allow to settle overnight 5. By morning nickel should have precipitated to the

bottom of the tank in the form of a plumable nickel hydroxide sludge. The top solution is checked for nickel using an A.A. If no nickel ions are present, the caustic solution can be decanted and neutralized with acid for discharge.

concentrate nickel hydroxide slurry, which can be transferred to a holding tank and sent off-site to recover the nickel value.

7. It must be noted that this procedure is not always 100 X effective and, on the mornings when all the nickel ions had not settled to the bottom of the t a n k , w e were faced with the task of removing the ~ ~ 1 1 amount of nickel with Ion Exchange, or by allowing that bath to set longer.

6. The end result is approximately 30 gallons of

This process could be enhanced by the acquisition of a filter press to dewater the nickel bearing hydroxide slurry, which at this stage is about 50% water. Yet we would still have a hazardous waste to market and send off-site for further treatment. The alternative was to find an efficient and low cost manageable means to reclaim the nickel metal from our nickel drag-out tanks. Being platers at heart, and having some experience with electrolytic recovery of metals such.as gold, silver, and copper, we felt that this was the way to meet our needs.

IONNET CELL TEST REPORT CONTINUED

Reviewing the available equipment and reports on the electrolytic recovery of nickel seemed to bring a negative response as to the effectiveness of this approach. One company, though, PMPC had a new design for an electrolytic recovery cell called the Ionnet, which we felt would fit the bill.

The unit consists of the main plate-out cell with five high surface area cathodes and six anodes arranged so that the solution flows serpentines through the cell passing by the anodes and cathodes. A control valve is located by each anode to adjust the solution height in each chamber. The unit can handle 500 amps.. Solution is pumped through the cell from a lower tank at 30 gpm. The total volume of the cell is 35 gallons, and the anodes are platinumized t it anium .

To define the limits of operation of the cell For the mixture of nickel sulfamate, electroless nickel, watts nickel and woods nickel dragout, which had to be treated daily, we needed to establish the optimum ph, temperature, current, solution flow , nickel concentration, and time required. A series of tests provided these parameters.

Method 2 ( the new electrolytic way )

1. Starting nickel concentration varied with daily production but was generally between 0.5 and 1.5 )

2. The ph of the combined drag-outs was 3.0 to 4.0 3. Flow was restricted only to prevent the cell from

overflowing. 4. A heater was used to raise temperature to 120 deg. . 5. Current ranged from between 100 and 250 amps. while

the voltage was between 6 and 9. Both were dependent on nickel concentration and solution conductivity.

6. Time elapsed could not be more than 24 hours.

Typical results show a depletion of nickel to routinely below 20 ppm level, This remaining 20 ppm was removed with Ion Exchange.

Our goal had been achieved. We had reduced the nickel metal in our dragouts, and in conjunction with the Ion Exchange’system we no longer generated a metal hydroxide sludge that had to be shipped off-site. Other benefits of this.project were the elimination of settling and holding

n IONNET CELL TEST REPORT CONTINUED

1 3 1 n 1 :f 1

3

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t a n k s , less l a b o r , r e d u c t i o n of t h e t o t a l hazardous waste s t o r e d i n t h e p l a n t , and a s a v i n g o f $ 0.86 p e r g a l l o n of d r a g o u t t reated. ( see t a b l e s )

T a b l e 1. I n s t a l l a t i o n Cost

B a s i s u n i t ( w i t h P t clad anodes ) $ 9,500.00 R e c t i f i e r ( 12 v o l t - 500 amps. ) s 1,200.00 Pump ( 3/4 hp 1 $ 500.00 Heater ( 3kw 1 S 500.00 Labor $ 200.00 T o t a l $ 11,900.00

Tab le 2. ( Chemical Treatment

C o s t / g a l l o n based on chemica l p r e c i p i t a t i o n of d r a g o u t s u s i n g chemica l method. T h i s i s based on a a v e r a g e o f 82.5 g a l l o n s per day , w e g e n e r a t e 3300 g a l l o n s of n i c k e l d ragou t i n 40 days . T h i s is reduced t o 1 ,000 g a l l o n s o f n i c k e l hydroxide s l u r r y , t h e minimum amount needed f o r a bu lk o f f - s i t e sh ipment .

Trea tment c o s t of $1 .25 /ga l lon $ 1,25OoOO T r a n s p o r t a t i o n f e e s 600000 A n a l y s i s f e e s 500.00 Labor ( 3 hrs . /day*40 days*SlO/hr S 1,200.00 Chemicals ( $ 4.00/day*40 days ) $ 160.00

T o t a l S 3,710.00

T a b l e 3. ( E l e c t r o l y t i c )

3,300 g a l l o n s treated w i t h Ionne t p l a t e - o u t c e l l over 40 days

Labor ( lhr /day*40 days* tlO/hr.) S 400.00 E l e c t r i c i t y $ 449.50 Chemicals $ 40.00

T o t a l s 889.20

Method 2 t r e a t m e n t ( e l e c t r o l y t i c ) c o s t per g a l l o n is $ 0.26 .

The t a b l e shows a pay back i n 8 . 4 months and a n annual s a v i n g o f $ 17,028 p e r y e a r t h e r e a f t e r based on 19,800 g a l l o n s o f n i c k e l per year.

J

IONNET NICKEL RECOVERY PMF INC. TREATMENT STUDY

CONCENTRATION IN PPY. 14** fl 1200

0:OO 2:OO 4:OO 6:OO 8:OO 1O:OO 12:OO 14:OO 16:OO 18:OO 20:OO

HOURS ON LINE I!

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This report was submitted to The Connecticut Hazardous Waste Management Service by PMF Inc. to fulfill the Matching Challenge Grant which we received from them.

Authors: J e f f Collins is Technical Director at PMF Inc. He is

past president of the Waterbury Branch A.E.S.F. Chapter and a member of ASTM

B.S. in Chemical and Materials Engineering from the University of Connecticut.

Christopher Gervascio is QA manager at PMF Inc. and has a

. i , , . . . . . .. . . . . . . . . . . . . . . . . . , . . . . . . , _ . . .. . ,. . . , ,,. ... ..

J

Copper, Nickel and Chromium Recovery I

In a Jobshop

By Tom Nadeau and Mike Oejak

/-

Plater meets effluent Iimlt8 wlthout producing hmrdous sludge.

G.G. Buffing and Plating is a jobshop in Montreal, Quebec, Canada, that platesdecorative copper, nickel, chromium and hard chrome on a variety of components and trim for automobiles and motorcycles. la 1984, thecompany decided to expand its facilities. How- ever, because it i s located in a high- density urban locale, the area available for expansion was limited. G.G. Buffing elected to build a two-

story addition to the existing plant that would house a new plating line on the

Tom Nadoru, plant manrgor, In chomlcrl rococmy room abow platlng Ilm. Noto IndlVMul rkld-mountod movoy unb.

ground level and all service equipment (scrubbers, rectifiers, pollutioncontrol system, etc.) on the upper level. To receive permission from the City of Montreal to proceed with the expansion, the company was required to submit details of its planned waste- treatment system, demonstrating that it would comply with local discharge standards. The requirements were 5 mg/Leach forcopper, nickel andchro- mium.

Convent i ona I waste treat men t- precipitation and destruction-was considered. And although this approach would have enabled the plant to meet its discharge limits, it

entailed an ongoing cost with no chance of payback. Considering the escalating costs of disposing metal hydroxide sludge, it wasalso reasoned that the operating expenses for such a system could only increase in the future. G.G. Buffing thus decided to use chemical recovery to comply with the discharge limits while reducing operating costs. After evaluating a number of technologies, short-bed ion exchange' was selected for these reasons:

'Patented in Canada, US. and other coontries. Eco-Tec Ltd.. Pickering. Ontario. Canada.

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1 Theequipment wascompact and could fit on the second floor of the building.

2. Although copper, nickel and chromium rinses required separate systems, the equipment was similar in design and operation. This, it was felt, would make it easier for the operators to understand and maintain the systems.

3. Visits to other installations con- firmed that the technology was proven and the equipment reliable.

The recovery systems were installed late in 1984 and started up in early 6 5 . Each is connected to the plating operation in a manner similar to that ‘ahown in Fig. 1. The copper, nickel and chromium plating baths are each

’ followed by three 600gal rinse tanks designed to accommodate counter- current flow. The quality of the water in thefirst rinseismonitored byacon- ductivity probe. When the dragout of plating solution to the first rinse increases the conductivity above a set- point. deionized (DI) water is introduced automatically to the third rinse.

As the rinses counterflow forward, the rising level in the first rinse activates a level controller that starts a pump, transferring rinsewater up to the second-floor feed tank for the re- spective recovery system. The ion exchangers remove the dissolved metal from the rinsewater. Treated copper and nickel rinsewaters then flow to a pit for final pH adjustment andaredischarged. Treated chromium rinsewater is recycled. Periodically, the ion-exchange (IX) resins are regenerated automatically to yield a concentrated metal salt solution that is recycled to the appropriate plating bath.

Copper Recovery Figure 2 illustrates the copper salt recovery process. Copper is plated out of a sulfate solution. Rinsewater from the first rinse following plating is transferred to a feed tank for the copper recovery unit, which begins operation when initiated by a level controller in the feed tank. Rinsewater at about 38 Umin flows through a carbon column to remove organic brightener additive, then through a cadridge pre-filter to remove suspended solids, and, finally, down throughashort(l5-cm high,30- cm diameter) column of fine-mesh cation-exchange resin. Copper cations in solution are exchanged for hydrogen cations on the resin.

The copper concentration of the

rinsewater is reduced from about 300 to less than 1 mg/L. Despite the fact that the water leaving the recovery unit is essentially free of copper, the water isnot recycled forcopper rinsing. This is because the exchange of copper for hydrogen makes the wateracidic. Re- cycling it to the copper rinses would interfere with the operation of the conductivity controller in the first rinse andeventually would reduce theeffec- tivenessof the recovery unit to remove copper.

After a set time, the flow of rinsewater through the cation exchanger is stopped automatically. This time is based on the concentration of copper in the first rinse, the flow rate through the recovery unit, and the capacity of the cation exchanger to effectively maintain a low concentration of cop- perin itseffluent. With theflowof rinsewater stopped, the recovery unit goes through an automatic regeneration sequence. Dilute (about 10 percent) sulfuric acid regenerant is passed up through the cation exchanger. The initial volume leaving the exchanger is displaced rinsewater, which is diverted back to the feed tank. As the sulfuric acid passes through

the cation exchanger, copper is exchanged from the resin for hydrogen. A concentrated copper sulfate solution then leaves the exchanger and is diverted to a holding tank. Water then flows down through the exchanger, rinsing the excess acid and copper solution back into the vessel used to automatically make up the regenerant solution for the next regeneration. This “reciprocated wash” ensures that sulfuric acid is used efficiently and that no copper is lost during regeneration.

The regeneration Sequence takes only abodt 1 min. The recovery unit is then ready to begin another cycle of treating rinsewater as required. The concentrated copper sulfate solution recovered from the rinsewater is added to thecopper Plating bath when needed.

Nickel Recovery Semibright and bright nickel plating processes are carried out in Watts- type baths at G.G. Buffing. Figure 3 depicts the nickel salt recovery process. Rinsewater from bright nickel plating is transferred to the recovery unit feed tank as described above. The nickel recovery unit begins operation when initiated by a level controller in the feed tank. Rinsewater flows at about 38 Umin through a cartridge pre-filter to remove suspended solids, then down through a short (30cm high, 30cm diameter) column of fine- mesh cation-exchange resin.

Nickel cations in solution are exchanged for hydrogen cations on the resin. The nickel concentration of the rinsewater is reduced from about 500 to less than 1 mg/L. As with the copper recovery system, the water is not recycled to the rinses for the same reasons-plus one more. The rinsewater contains organic additives from the plating bath. Being anionic ornon- ionic in nature, these additives are not removed by cation exchange. Con- tinued recycling of the water would result in a high concentration of organics in the rinsewater. This condition can result in an organic film forming on the nickel surface that will affect chromic acid plating, typically resulting in “whitewash” at highcurrent- density areas.

CHROME RECOVERY ONLY WATER

I .._...._....................

P NT EFFLUENT

Fig. 1-Typical recovery ayrtem layout.

2.. . . . . . . . . . . . .* ‘ / .

t

After a pre-set time. as with the copper recovery unit, the flow through the cation exchanger stops and an automatic regeneration sequence begins. Regeneration commences in a manner similar to that with the copper recovery unit. Dilute (about 10 Per- cent) sulfuric acid regenerant i s passed up through the cation exchanger to exchange hydrogen for nickel. After the displacement of rinsewater, a concentrated nickel sulfate solution leaves the cation exchanger. p t this point, the nickel Sulfate solution has a pH of 0.8 to 0.9 due to

,, the excess sulfuric acid required to “‘effectively regenerate the resin. If such

, an acidic concentrate were added to the nickel plating bath, it would result in an unwanted depression of the operating pH from thedesired value of 4.0. To raise the pH of the concentrate. it passes immediately through a second resin column containing a

sorption resin, which has the unique capability to “sorp“ the excess acid from the nickel sulfate.

The concentrate leaves this column with a pH in the acceptable range of 3.0 to 3.5 and flows to a holding tank awaiting recycle to the plating baths. A reciprocated wash of the resin columns with water “regenerates” the sorption resin while rinsing the regenerated cat ion res in and recovering excess acid and nickel sulfate for the subsequent regeneration. Again, nickel loss is prevented and acid consumption is reduced. Once this wash is completed, the unit is ready to begin another automatic cycle.

Chromlc Acid Recovery Chromium is plated from a chromic acid solution. Plating rinsewater is transferred to the recovery unit feed tank as described above (Fig. 4). From the feed tank, rinsewater flows through

CONCENTRATED COPPER SULFATE

COPPER PLATING RINSE WATER

WATER

TO STORAGE FOR ACJD DILUTION

EFFLUENT DILUTE (4.0 ppm COPPER) SULFURIC ACID I

1. ONSTREAM 2 REGENERATION 3. RINSING

1 EFFLUENT (e2.0 ppm NICKEL)

CONENTRAED NICKEL SULFATE pH 4.0

4 WATER

I

(ffT=_LI? SoRPrxm UCwmER wamm

DILUTE TO STORAGE SULFURIC FOR ACID ACID DILUTION

1. ONSTREAM 2. REGENERATION 3. RINSING

Fig. 3-Nlckel u)t rowvery proceu.

a cartridge pre-filter to remove SUS-

pended solids. then down through a short column U 5 c m high, 30em diameter) Of fine-mesh ’cation- exchange resin. Cationic contaminants such as trivalentchromium, iron, nickel and CoPPWareexchanged for hydrogen by the resin. The rinsewater then continues on through a short Column (7-cm high, 30-c-m diameter) Of fine-mesh anion- exchange resin, where the chromate anions are exchanged for hydroxide anions by the resin. DI water leaves the anion exchanger and is recycled to the counterflow rinse system.

The quality of water leaving the recovery unit is continuously mon- itored by an in-line conductivity controller. When the conductivity exceeds 90 micromhos, the flow of water leaving the recovery unit is diverted from the final to the first rinse. By recirculating to the first rinse tank, the anion-exchange resin is more fully loaded with chromate without im- pairing the rinsewater quality. After 15 min, the flow of rinsewater stops and an automatic regeneration sequence begins.

During regeneration, a dilute (10 percent) sulfuric acid solution regenerates the cation exchanger. The regenerant flows to final pH adjustment and is discharged because the concentration of metallic contaminants is lowenough to produce a final plant effluent that does not exceed the environmental limits.

Meanwhile, dilute (5 percent) caustic soda regenerant flows up through the anion exchanger, exchanging chromate for hydroxide. The sodium chromate solution leaving the anion exchanger then flows through another cation exchanger that exchanges sodium for hydrogen, thereby producing chromicacid, which flows toa storage tank. Water is used to rinse the excess chromate and caustic out of the exchanger columns back intoa reservoir for the subsequent regeneration. In this way, chrome loss and regenerant chemical consumption are reduced.

The chromic acid produced by the recovery unit has a lower chromate- to-sulfate ratio (50:l) than the plating bath (150:l) due to the pickup of some sulfuric acid from the cationexchange resins. This iseasilycorrected by adding a small amount (typically 0.7 kg/day) of barium carbonate to precipitate the excess sulfate. The chem- icaI treatment is performed automatically in a small tank that provides mixing, settling and transfer of the

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treated chromic acid to a final holding tank prior to recycle to the plating bath.

Operating Expedence The recovery equipment arrived at the plant as pre-assembled, skid-mounted, automatic units. Installation was carried out by G.G. Buffing personnel following written instructions provided by the supplier. This consisted prima- rily of running interconnecting PVC piping. The systems were started up by the equipment supplier, and G.G. 5uffing workers were trained in their use. Noteworthy experiences during

. the first 10 months of operation are summarized below.

I 1. Suspended Solids: Shortly after startup, the chromic acid recovery system experienced a problem of “foul- ing” of the anion-exchange resin by metalllc hydroxide precipitates. This was traced to suspended solids passing from the chromium rinses into the cation exchanger of the recovery unit. It prevented effective removal of cationic impurities (trivalent chromium, nickel and copper), which then passed to the anionic resin-in the hydroxide form-and precipitated.

The situation was corrected by physically cleaning the chromium rinse tanks, which had contained an accumulation of solids since startup. Also, the pre-filter cartridges of the recovery unit were changed from 10 to a nominal 1 pm. The IX resin was cleaned and the unit restarted.

2. Deionized Water: After approximately 10 months, the nickel plating bath experienced some problems with anode bags becoming clogged due to calcium sulfate crystallization. It was determined that, although DI water was being supplied to the nickel rinses, the recovery unit was using city water with 240 ppm total dissolved solids (TDS) during its reciprocated wash after regeneration. Calcium was entering the system at this point, exchang-

ing onto the resin, then being regenerated off and transferred to the plating bath along with recovered nickel. This situation was corrected by replacing the unit’s water supply with DI water.

3. Nickel Quality: One concern with nickel recovery in duplex (semibright/ bright) nickel plating operations is crosscontamination of organic additives. In particular, the sulfo-organic additivesof a bright nickel plating bath can adversely affect the corrosion resistance of the nickel deposit if they are introduced to the semibright bath. This is important because it is the bright nickel solution that is dragged into the rinses, yet it is the semibright bath that is depleted of nickel and requires the nickel addition. Since the organic additives are anionic or non- ionic, they are not exchanged onto the cation-exchange resin along with nickel.

In order to confirm this, a test in which nickel was plated out of a solution prepared with recovered nickel sulfate wasconducted. The nickel plate then was analyzed for sulfur Content.

The results showed that there was less than 0.W2 percent sulfur in the plate. In this standard test. a level of less than 0.006 percent sulfur is cohsidered acceptable for semibright nickel deposits. On this basis, the recovered product was deemed suitable for recycle to either of the nickel plating baths.

4. Air Locks: On occasion, poor operation for a day or two was noted. The cause was found to be air locks in the piping from the regenerant acid and caustic storage tanks. These air locks could occur if the storage tank was allowed to drain completely prior to refilling. Daily monitoring of the tank levels to ensure that they did not run dry successfully prevented a recurrence of this problem.

5 . Moni tor ing / Maintenance: Monitoring and maintenance of all recovery units have been carried out by the plating managerat G.G. Buffing. This has required an average of 1% hr/day. Monitoring consists of com- pleting log sheets noting parameters such as flow, pressure and visual

I A

1. ONSTREAM

CATION a CATION UaUNGER

2 REGENERA”

T M T W

3. WASH 1 Fig. 4-Chromlc add r.cov*y pro-u.

appearance of rinses for the individual recovery units. Maintaining such a log has been useful when troubleshooting is required, as it provides a convenient history to indicate trends that may have developed. 6. Chromrum Plating: I t was

observed that the throwing power of the chromium plating bath had remained exceptionally good by comparison with experience prior to using such a recovery system. The previous practice was to return as much of the dragout collected in the first rinse to the b y h as evaporation would allow.

The improved plating performance was attributed to the elimination of catlonic contaminants (trivalent chro- m,ium, nickel, iron) being returned to the plating bath due to the nature of

the IX recovery process. The result has been a more pure plating bath with lower electrical resistance and good throwing power.

Performance G.G. Buffing had specified the recovery capacities of the equipment for chromic acid, nickel sulfate and copper sulfate to be 0.6, 2.5 and 2.3 kglhr, respectively. After startup, the systems demonstrated recovery capacities of 0.74, 2.8 and 3.28 kglhr, respectively.

The performance of each of the recovery systems is summarized in Table 1. Note the first rinseconcentra- tions of chromium, nickel and copper (170,460 and 260 mg/L). These repre- sent the concentration of the feeds to

.- d*(=osUkg, $3

0.07 023 026

. 0.05

W.61Ikg 1-

. t

. , ...

. .,..

the recovery units. The concentration of the recovered products indicates factors Of concentration forchromium. nickel, and copper of 31 1,69 and 135 times. The effluent concentrations are averaged over a complete cycle of operation.

It should be noted that theseeffluent streams Only flow when the recovery unit is going through a cycle. If the conductivity controller in the rinse tank detects that the rinsewater contamination is below the set-point, the recovery unit remains in standby with no flow.

The effluent concentration of 20 mg/L chromium for the chromic acid recovery Unit is typical. Despite the concentration, the amount of chromium lost is less than 0.7 percent of the dragout. It is present in the waste stream from the regeneration of the second cation exchanger (used for the conversion of sodium chromate to chromic acid). While the concentration of this point source is high relative to the effluent discharge limit, this waste stream is intermittentand representsa very small portion of the total plant effluent.

Based on theeffluentflowof35to45 Vmin as indicated in Table 2, the discharge from the chromium unit would contribute0.8 mg/L to the final stream concentration when it is flowing. In making a similar calculation for nickel and copper, the effluents from the recovery units are contributing about 0.5 and 0.45 mg/L, respectively, to the final stream, yet an analysis showed higher levels of nickel and copper. This wasattributed in part todripsdur- ing transfer, but it is suspected that most of it comes from spills of small volumes of plating solution while serv- icing bath filters. The small puddles below the catwalk slowly make their way into the waste trench, contributing to the nickel and copper levels detected. Collection and segregated treatment of these spills may be required to meet lower limitsshould they be tightened in the future.

Economics Costs for the recovery of chromium, nickel, and copper using the units are summarized in Tables 3,4 and 5. Note that in each case, a consumption figure for caustic soda is given. Even though no caustic may be used in a recovery unit's operation, it isassumed that it is required for final pH adjustment because the effluent from the cation exchangers will be acidic due to the exchange of metals for hydrogen.

1 1 3 :1

1 1

3 L 'I 13 1J 3 3 J

J

By comparison, the alternative cost of waste treatment and sludge disposal is shown in Tables 6, 7 and 8. The net savings are calculated by difference. The key figure in the waste-treatment calculations is the cost of sludge disposal. At $0.25/kg ($227/ton). this cost IS expected to escalate drastically, resulting in improved future savings for recovery.

The savings realized in the 10 months of operation are summarized in Table 9. Annual savings have been extraf6lated. Maximum potential savings are calculated based on the plating line operating at full capacity

' Conrumptlon

for 6000 hr/year. The greatest savings have been real-

ized by the chromic acid recovery system. The greater benefits and higher utilization of the chromium system compared with the others isdue to the fact that hard chromium production, which does not require nickel or copper plating, is carried out as well as decorative chromium deposition.

The savings for nickel sulfate recovery were moderate but can increase significantly as production rises. Low production in copper plating resulted in minimal savings. Based on the level of copper plating production, a recov- erysystemcould not be justified. How- ever, it should be mentioned that during the initial design stages of the plant, a method to treat or recover the copper effluent had to be included in order for building permits to be granted.

The total annual savings for the first year of operation are calculated to be $13,257. As G.G. Buffing's production increases and if present costs were to remain the same, annual savings could reach as high as $60,222. In all likelihood, however, costs will increase- particularly for sludge disposal-resulting in even greater savings. But even minimal savings are considered acceptable because the installed cost of the recovery system (slightly under $lOO,OOO U.S.) was comparable to that

of NiSQ 6KO.

Net savings = $1.53

- * II

Cortlkg, $

1.14 0.07 0.32

$1 5Wkg

A aximum '

Net 10-month annual potential saving total mvlng savlng mvlng

$4.34 $91 27 $1 0,952 $15.624

$ 6,348 $0.46 $2.55 $1847 $ 2216 $38250

$ 74 . .- $ 89 - Total Annual Saving $13,257 $60222

for a destructiodprecipitation waste- treatment system.

Recommendations Based on the experiences of G.G. Buf- fing, the followlng recommendations should be considered by other plants that may be pondering a similar approach to reducing or eliminating sludge:

0 Proper determination of waste loadings (dragout) to be recovered by the equipment is important. In the cas of G.G. Buffing, production and &out had to be estimated because the plant had not yet been built. ','Existing plants, especially those with constant production, make such

' dragout determinations easily. 0 Designate at least one person in

the plant to be responsible for the system and ensure that he is given company support to spend his full time training during startup.

Maintain daily log sheets and forward them on a weekly basis to the equipment manufacturer for inspection and comment. Such records prove extremely valuable when troubleshooting, as well as for general

monitoring of the system's process and economic performance.

0 If tighter effluent limits need to be met. consider collection and segregated treatment of floor spills and eff luent from the chromic acid recovery unit.

storage capacity to minimize the need for topping up tanks and reduce the About the Authors

Tom Nadeau is plant manager at G.G. likelihood of running dry. Install all equipment in a common Buffing and Plating, 907 Taschereau

area toallow convenient monitoring of Blvd., Longeuil, Quebec, Canada J4K the system. 2x2. He has been in that position sin,ce

0 Prior to startup, Clean OUtall rinse 1983. Previously, he operated his own tanks of accumulated solids that might plating company for 20 years. Mr. clog filters or ion exchangers. Nadeau has been affiliated with the

industry since 1947. Conclusions Mike Dejak is general sales manager Chemical recovery systems for chro- for Eco-Tec Ltd.,925 Brock Rd. South, mium, nickel and copper using short- Pickering, Ontario, Canada L1 W 2x9. bed ion-exchange technology have He has worked in technical service

to meet effluent discharge limits with- abatement and chemical recovery in out producing hazardous sludge. the metal finishing industry. Mr. Dejak

With the escalating costs and risks holds a degree in applied chemistry associated with the disposal of metal and chemical engineering from the hydroxide sludges, which are ClaS- University of Toronto and is a reg- sified as hazardous wastes, such an istered professional engineer in the approach in similar plating operations Province of Ontario. He isa member of should be considered. 0 the AESF Toronto Branch.

0 lnstali sufficient regenerant Debk

successfully allowed a plating jobshop and sales of equipment for pollution II

L

Reprinted from PLATING AS L, SCRFACE FINISHING, April 1986

PURIFICATION AND RESTORATION OF CHROMIC ACID PLATING SOLUTIONS

All chromic acid plating solutions become contaminated with metal impurities (see attached Figure 1). The rate of contamination determines how long a solution can be used and the rate metals must be removed to continuously maintain the solution. Compliance with current and future regulations dictates that it is most prudent and economical to operate a chromic acid plating process as a closed-loop. In the closed loop, the plating solution is the focal point and the solution is continuously maintained at the desired composition to obtain efficiency of plating, production rates and reliable quality of plated parts. The rinse water and process chemicals in the rinse are recovered for use. Purification of the plating solution permits evaporative recovery of the rinse water and chemicals. The rinse can be added as make-up water to the plating solution or a concentrate of chemicals can be added to the plating solution. The rinse water and chemicals can be recovered by a combination of ion exchange and IONSEPTM Electrodialytic Processes. Ionsep offers closed-loop systems (see Figure 2) for chromic acid plating. The first step toward a closed-loop is to provide purification and restoration of the plating solution.

The IONSEP Process is briefly described in the enclosed brochure. A membrane in an electrochemical cell physically separates the chromic acid solution from a mildly alkaline IONSEPTM Catholyte solution. When electricity is passed through the cell, metal cations leave the chromic acid solution through the membrane into the catholyte and are replaced by hydrogen ions in the plating solution to form chromic acid. The metal cations entering the catholyte react with hydroxyl ions to form insoluble hydroxides that can be removed from the olyte as waste (minimum waste). The hydrogen ion e formed at the cell anode to replace the metal cat removed and the hydroxyl ions are formed at the cel thode to precipitate the metal cations. Only electricity and water are consumed. Chromium's ih the chromic acid is converted to chromic acid at the cell anode. Removal of metal impurities and conversion of chromium+' to chromic acid provides purification and restoration of the plating solution. This is done with electricity. There are no chemicals consumed.

Ionsep - 012590 1/4

The IONSEP Processes are covered by U.S. patents and a license is required to operate the process. Know-how for operating the processes is supplied under the terms and conditions of a Licensing AGREEMENT between Ionsep and the operator of the process.

Ionsep sells an Electrochemical System that is suitable for operation of the IONSEPTM Electrodialytic Processes. The system comprises a rectifier, one or more electrochemical cells, a pump and tank for catholyte and other components required to install and operate the process. The user is responsible for operation of the system and, of course, the results obtained.

The Electrochemical System is designed to be operated continuously up to a specified amperage. The capacity to remove metals and oxidize ~hromium'~ is varied by varying amperage of the system. The amount of metals removed per ampere hour is related to the concentration of metals in the plating solution. When the concentration of metals is high, the quantity removed per hour is high. When the concentration is at the 1 to 4 g/1 level (usually maintenance level) the amount of metals removed per day is equal to the amount entering the solution per day. The system is self-regulating. The cell operates at a set voltage and variable amperage. The current increases or decreases with the electrical conductivity of the solution. If metal cations are not being removed, hydrogen ions will be formed at the cell anode and removed like metal cations. In general the cell operates at essentially a constant amperage-voltage relationship.

ries to size each system for each customer so system will reach a maintenance operation as . There is, however, no way fo r Ionsep to

know- control the rate that metals enter the user's plating solution, and, of course, cannot ensure that the maintenance level will be reached or maintained at all times. In general, all systems have met the expected performance.

Ionsep - 012590 2 / 4

1 1

n

:1 '3

'I .-

3

J

BUS BAR PLATING

CHLORIDE

COPPER NICKEL SULFATE BASE METALS

ZINC ALUMINUM I RON

ETC

LINER LEAD CHROMIC ACID

PLATING BATH

I RON CALC I UM

MAGNESIUM

WATER OTCe SULFATE FLUORIDE MAGNESIUM SILICON STRONTIUM

CATALYST '0 Figure 1

CHEMICALS I N CHROMIC ACID PLATING SOLUTIONS

Ionsep - 012590 3 / 4

Figure 2:

U Anion

Regenerof ion Q C ohon R e m Cotion 6

7egenero tion U

ELECTRICALLY CLOSED LOOP FOR CHROMIC ACID SOLUTIONS

.IONSEP E L E ~ R O D I A L Y T I C PROCESS

CAhP DRESSER 8 McKEE INC. a

METALLIC WASTE REDUCTION - AN OVERVIEW

James T. O’Rourke, Ph.D. . Camp Dresser & McKee Inc.

Requlatory Considerations

The metal finishing and electroplating effluent regulations are

the d r i v i n g force. L i t i g a t i o n i s essentially over and the com-

pliance dates are either here or will be here i n the near future.

In most cases the compliance will be achieved mainly by some

chemical precipitation and clarification process which will pro-

duce sludges or other concentrated wastes whose disposal i s

regulated separately .

Disposal of sludges fa1 1 s under hazardous waste regulations (RCRA) . These regulations are i n a s ta te of evolution.

regulatory proposal s are accepted a1 1 generators of hazardous waste,

as l i t t l e as 55 lb/month, may be effected.

residue disposal may rival the cost of treatment. The current

limited availabil i ty of hazardous waste handling and disposal s i tes

(particularly i n Massachusetts and New England) are a factor i n the

high disposal costs. However, ultimate disposal costs are bound t o

I f the current

The very h i g h cost of

k a n t regardless o f the location of the disposal s i tes .

Presently we have regulations on what the groundwater ( d r i n k i n g water)

quality should be.

lations on protection of groundwater supplies a t a Pational level.

As the regulations for protection of d r i n k i n g water grow and mature

i n the future, they will inevitably affect the manner and cost of

However, there are really minimal rules and regu-

disposal of residues.

-2- CAMP DRESSER 8 McKEE INC.

I t is apparent t h a t the reduction o f hazardous and other wastes

their source i s one piece of the overall hazardous waste manage-

ment p lan t h a t we can i l l afford t o overlook.

should be pursued w i t h vigor b u t we should cau t ion t h a t i t is no t

going t o be a complete solution.

here today, and we will concentrate our discussions on t h a t theme.

T h i s conference hopefully will leave you w i t h some helpful t h o u g h t s

about the problems and some of the related solutions.

Source reduction

Source reduction i s the theme

State-of-the-Art

One of the factors t h a t place recovery opt ions a t a disadvantage

over treatment is that recovery systems are relatively complicated

and often a t an experimental stage. All laboratory studies and

their results have not yet been transferred t o the field-scale

applications. I will t r y i n the next few minutes to outline some

of the techniques that have been appl ied, w i t h varied success.

- We must talk both about water reuse and recovery as well as the

r O f course i t

i metals and other chemicals t h a t constitute the "hazardous"

aspects o f these wastes b u t we need t o remember t h a t the cost and

u t i l i t y of disposal a l so depends t o a great extent on volume.

We must therefore do a l l we can t o reduce the volume of wastewater

and water content of sludges to minimize this volume factor.

and reuse of metals and other chemicals.

3; -

1 n 1

4 " . 7

3 3

11

3

-3-

Water use i n the metal finishing

ways -- many of which can be imp

Most of these, counter-current r

etc. are well established and i n

CAMP DRESSER 8 McKEE INC.

industry can be reduced i n many

emented by p l a n t (shop) personnel.

nses, spray v s . emersion rinse,

wide acceptance and use. Sometimes

just the shop layout can assist i n reducing water usage.

When considering the disposal of sludge generated by the wastewater

treatment that is generally inevitable cost comparisons need t o be

made between disposal of "1 iqu id" sludges versus "dewatered" sludges.

The many dewatering devices: rotary drum vacuum f i l t e r s , centrifuges,

recessed cavity plate f i l t e r s , etc. should be investigated.

- B u t the very best way t o reduce the cost of wastewater treatment

and the attendent sludge disposal cost is t o install some material

recovery/reuse system.

are very expensive, these costs can be largely, if not t o t a l l y ,

offset i n some cases by the c o s t savings associated w i t h wastewater

A1 t h o u g h many o f the recovery/reuse systems

and-,sludge disposal AND the reduced raw material cost savings.

R osmosis (RO) for instance can be employed t o recover b o t h

the chemicals from brightener and p l a t i n g solutions a s well as

al lowing the reuse of rinse water.

p l a t i n g operations.

RO has been applied i n nickel

3 J

-4- C A l P DAESSER 8 McKEE INC.

Another "membrane technology" 1 ike R O , electrodialysis ( E D )

employs an ion selective membrane t o concentrate metallic ions

from rinse water t o permit their recycle t o the p l a t i n g baths.

Many of the precious metals, including gold and silver, as well

as zinc, copper, chrome and others can be recovered us ing ED.

Ion exchange i s another "ion concentrating" technology t h a t i s

widely used i n the industry t o recover p l a t i n g metals and t o .

reconstitute plating baths.

t o recover metals from s t r ip solutions.

uses ion exchange to recover and reuse large volumes of rinse water.

Ion exchange i s also widely used

The anodizing industry

Electrolytic recovery results i n direct metal recovery (as the metal )

from concentrated solutions and i s particularly useful i n the

recovery of gold and silver. I t is also used t o recover t i n ,

copper and chrome. A

These few examples should give you an idea of the wide variety o f

logies that can be applied t o assist i n the management of

us wastes generated by the metal finishing industry.

The case studies we will hear later will of course go in to great

detail i n the applisation o f some of the technologies.

1

3 13 **l L ..

J

LJ .1

- 5-

Overview of the Industry

CAMP DRESSER a MCKEE INC.

The metal -bearing wastewater generators i n this area (Massachusetts

and New England) range from the typical electroplating j o b shops

w i t h significant metal concentrations t o the h i g h tech industries

where discharge is a s varied as the industry i t se l f . We have yet

t o see one case which i s representative of many others.

that metals recovery needs t o be evaluated on a case-by-case basis

for each industry.

This means

ELECTROPLATING

Overview

Accoraing to €PA, the electroplating category of Standard Industrial Classification (SIC), code number 3417 consists of facilities which perform any or all of the following specific operations:

Electroplating;

Electroless plating;

Anodizing and coating;

Chemical etching snd milling; and

Printed circuit board manufacturing.

Electroplating is a process by which a metal or plastic object is coated with one or more metals using electrodeposition. E!ectrodeposition is a process by which the object to be plated becomes a csthode and the surrounding solution is the anode in an electrochemical cell. By passing an electrical current through the plating solution, the dissolved metal ions in the plating solution are deposited onto the surface of the plating workpiece. Ferrous or nonferrous objects are commonly plated with aluminum, brass, bronze, cadmium, chromium, copper, iron, lead, nickel, tin, and zinc. The electroplating baths may contain metallic salts, alkalies, and other bath additives. Some of these additives may be used to reduce irregularities in the metal surface, increase brightness of the finished surface, or reduce texture of the plated layer of metal.

An electroplating process generally calls for moving the object to be coated (workpiece) through a series of baths arranged in a carefully designed sequence. Typically, the sequence consists of cleaning, rinsing, and a number of alternating electroplating and rinsing steps. The workpiece can be carried on racks or in barrels. The following list contains the typical composition of various electroplating baths. These include:

Silver;

@I Acid tin;

Stannate ?ine;

I=] Tin-copper alloy;

Tin-nickel al!oy;

9 * 30

1

7

:1

:.I 3 3 -1 3 4 3 J 1

a n

Q 0 II

Acid zinc;

Zinc cyanide;

Gold cyanide;

Iron;

Lead fluoborate;

Lead-tin;

Nickel;

Nickel-acid fluoride;

Brass and brcnze;

Cadmium cyanide;

Cadmium fluoborate;

Copper cyanide; and

Copper fluoborate.

--.--- I-

Waste Characteristics of flectroplathg Industry ........................ "...."...................................----.--.

From a waste reduction standpoint, the ten primary electroplating process wastes can be grouped as follows to reflect only four different process origins:

0 Work cleaning wastes;

Waste rinsewater; and

Spent plating solutions and sludges;

Treatment wastes.

Some or all of the ten waste types may be combined into a single stream before treatment and disposal.

Electroplating facilities must check to see if any in-house chemical wastes are hazardous. The following list of chemicals commonly used in the Electroplaters Industry (SIC Code 3471) would typically be considered hazardous wastes if mixed with other waste materials or if disposed of independently. Facilities handling these materials or

9 - 31

generating these process wastes may be regulated as small quantrty generators (SQGS) or fully regulated large quantrty generators (LQGs) of hazardous wastes. These include:

LI

LI

0

0

0 a

Trichloroethylene;

Methylene chloride;

1 , 1 , l 4richloroethane;

Carbon tetrachloride;

Chlorinated fluorocarbons;

Sludges from vapor degreasers;

Still bottoms from recovery of degreasing solvent:

Non-halogenated solvents like acetone;

Cresol;

Wastewater from electroplating operations;

Spent cyanide plating bath;

Plating bath residues from the bottom of plating baths:

Spent stripping and cleaning bath solutions; and

Quenching water treatment sludges.

Most electroplating hazardous waste is generated from plating rinsewater, electroplating sludges, and sludges from the treatment of waste rinsewaters. Contaminated rinsewater accounts for a majortty of waste produced. Rinsewater is used to remove the drag-out from a workpiece. Drag-out refers to the excess cleaning or plating solution that adheres to the workpiece surface, and gets carried out of the bath along with the workpiece.

Spent cleaning and plating solutions are another waste source. Cleaning solutions may be acidic or basic, and may contain organics. Heavy metals are usually not present, although some cleaning solutions contain cyanide. Spent plating solutions contain high concentrations of metals. These solutions are not regularly discarded. but may require purging if impurities build up.

The wastewater produced in the electroplating process may contain a variety of heavy metals and cyanide. The metals are removed by adding lime or other precipitation

9 - 32

1 1 1

1 - ‘1 I _ ‘1 1 :1 :I 1 3

3

agents. The result is a dilute metal hydroxide sludge, which i(i thickened and then disposed of by landfilling.

The type of hazardous waste generated from electroplating depend on the actual electrodeposition process. The following table describes specific types of waste, sources of these wastes, and RCRA codes for these wastes. For detailed definitions of the hazardous wastes see the Hazardous Waste List in !he Appendices.

ELECTROPLATING PROCESS WASTES

RCRA Codes Waste Descriotion Source

Spent alkaline cleaning solution

Spent acid cleaning

Spent cyanide cleaning solutions

Degreaser sludges

Solvent recycle still bottoms

Spent plating solutions

Filter sludges

Waste rinsewater

Wastewater treatment sludge

Aqueous cleaning FOO9

Acid pickling DOC2

Aqueous cleaning F009

Solvent cleaning FW1, F003, FOOS

Solvent recycling FOO1, F003, F005

Electroplating F007

Electroplating F008

Drag-out, equipment cleaning, spills

F007

Wastewater treatment F006

Vent scrubber wastes Vent scrubbing FOO9

ion exchange resin reagents Demineralization of process water

Stripping wastes Cleaning FOO9

EPA Waste Codes

€PA waste code descriptions :cr common hazardous wastes generated by electroplaters include:

DOOl;

D002;

9 - 33

J

L1

0

0

0 11 11

0007;

0008;

F C d ; F002;

f003;

F004;

F005;

FC06;

F007;

F008;

f009;

F010;

f011;

F012; and

f019.

For detailed chemical definitions see the Hazardous Waste List in the Appendices.

Acuteb Toxic EPA Waste Cod es from SDeafic So urces

P030;

P098; and

P106.

For detailed chemical definitions see the Hazardous Waste List in the Appendices.

Electroplating and Waste Reduction

The mast common waste reduction practices which can be applied to the four main waste streams in the electroplating processes are similar to the cleaning wastes

9 - 3 4

. , .. .......................................................... - .......................... . . . . . . . . . . . . . . . . . . , . . . . . . . . . , . . . . . . . . , . . . . . . . . . .. . . . . . . . . . . . ....................._... ........ . ... ̂ . .. .. . . . . . . .

produced in many other manufacturing processes. A detailed discusston of waste reduction practices for parts Cleaning wastes is provided in Chapter 8 - It/artc Reducrion Options for P a m Clewiing Operatiom.

$Dent Platina Solutions and Sludaes

Plating solutions are not discarded irequently, but do require periodic replacement. Reduction practices available for minimizing spent plating waste include:

13

Increase plating solution life -- The lrfetime of a plating solutron is limited by the accumulation of impurities and/or by depletion of constituents due to drag-out. The impurities build up can be limited by the following techniques:

use purer anodes, b

b

w

reduce drag-in by better rinsing, use deionized or distilled water instead of tap water for make-up, regenerate plating solution through impurity removal, by: -- more efficient filtering of a plating solution, -- reducing the carbonate concentration in cyanide baths using

a technique developed by the U.S. Army (US. Patent 4,365,481), which involves freezing the carbonates out of solution. A metal box containing dry ice and acetone is immersed in the plating bath. Carbonates are precipitated directly onto the outside metal surface of the box which is then removed and the carbonates scraped off the box and discarded as solid waste, and

properly design and maintain racks - Corrosion and salt deposits on the rack will contaminate plating solutions by chipping and falling into the solution;

w

Replace cyanide plating soliJtions with cyanide-free solutions -- A cyanide- zinc solution was replaced with a non-cyanide, non-chelated alkaline zinc solution. Other cyanide-free zinc solutions along with cyanide-free pyrophosphate copper plating solutions have been used. Such replacements often require upgrading of the cleaning techniques used because non-cyanide replacements may require a much more thoroughly cleaned surface to ensure -high quality plating. Military contracts often specify the use of cyanide solutions, thereby preventing the use of non- cyanide replacements;

Replace cadmium-based plating solutions with zinc solutions -- The use of cadmium has been replaced with zinc in many applications;

Replace hexavalent chromium with trivalent chromium --Trivalent chromium has been used in place of the more toxic hexavalent chromium bu: produces a lower qualify surface; and

9 - 35

Re!urn s6ent plaiing solution to manufacturer -- This requires on-site segregation of solutions according to the metal in solution.

Waste Rinsewater

There are several methods available to reduce the amount and toxicity of waste rinsewater. These methods can be grouped into two major techniques:

D(

13

Drag-out reduction -- minimizing drag-out will result in a decrease of the heavy metal content of the ultimate waste (treatment sludge); and ,.

Rinsewater reduction -- decreasing water COnSUmptiOn will decrease the volume of ordinary calcium and magnesium sludge that results when using hard water. The amount of heavy metal sludge produced remains the same. Therefore decreasing the amount of rinsewater without reducing drag-out may result in a smaller, but more highly toxic, volume of treatment sludge.

Draa-out Reduction

Reducing the drag-out reduces the amount of rinsewater needed. Also, less of the plating solution metals leave the process, which ultimately produces savings in raw materials, and treatment and disposal costs. The amount of drag-out depends on the following factors:

c] Surface tension of the plating solution;

c] Viscosity of the plating solution:

c] Physical shape and surface area of the workpiece and rack; and

a Speed of workpiece withdrawal and drainage time.

Generally, drag-out reduction techniques include:

Maximize plating solution operating temperature to lower both the viscosity and surface tension of the solution. The resulting higher evaporation rate may also inhibit the carbon dioxide absorption rate, slowing down the carbonate formation in cyanide solutions. Disadvantages include: b formation of carbonate by cyanide breakdown at elevated

temperatures, w higher energy costs, b higher chance for contamination due to incre'ased make-up

requirement, and b more need for air pollution control due to higher evaporation rage;

Minimize the plating bath chemical concentrations -- For example, it has been found that acceptable chromium plating can be obtained from baths

9 - 36

a

containing cnly 25 to 50 Q'I CrO, comparea to tfia traditlonar COncentratlOn of 250 g/l. Lowering the ccncentration will resillt in: b lower solution ViSCOSity, and b reduced rinsing requirement;

',Vithdraw workpiece at slower rates and allow SufifCient solution drainage time. Such as:

v

30 seconds usualiy aflow most drag-out to drain back to the tank, and 10 seconds still permits good drag-out recovery in application where quick drying is a probtem;

Using surfactants or wetting agents in the process Sath can lower a solutions surface tension enough to reduce drag-out by up to 50%. Only non-ionic wetting agents should be used. The use of surfactants is some?imes limited due to their adverse effect on the quality of the plate produced;

Proper positioning of the workpiece on the plating rack will facilitate the dripping of the drag-out back into the bath. This is best determined experimentally, although the following guidelines were found effective: b orient the surface as close to vertical as possible, b situate the longer dimension of the workpiece horizontally, and

position th8 workpiece with the lower edge tilted from the horizontal so that the runoff is from a corner rather than an entire edge; and

Improved drag-out recoverj by utilizing drainage boards positioned between process and rinse tanks can capture the dripping solution and route it back to the process bath. Incorporating an empty drip tank between the plating bath and the rinsing bath is another option to recover process chemicals for reuse in process baths.

Rinsewater reduction invokes rinsing off the workpiece in the most efficient manner, using the smallest volume of rinsewater. Traditionally, a workpiece would be immersed into a single rinsing bath following a plating bath, and then moved on to the next step in the process. Several methods exist which use less rinsewater than the traditional method, while still adequately rinsing the workpiece. These include:

Counter-flow multiple tank rinsing can reduce rinsewater requirements by 66% with possible theoretical reductions of over 90% reported. In a three- tank, counter-current series system, the:

workpiece enters the first rinse tank, which has the most contaminated rinsewater. It is then moved to the second tank, and then to the last where it contacts fresh rinsewater before moving on to the next step in the process, and

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fresh rinsewater enters only the last (third) rinsing tank. The water then flows into the second tank, then into the first tank from which it is routed to treatment or to the plating tank as a make-up;

Fog nozzles and sprays rinsing a workpiece is more efficient than immersing a workpiece into a water bath. Such considerations include:

fog nozzles and sprays are highly effective on simple workpieces, such as sheets, fog nozzles and sprays are not effective on oddly-shaped objects, since spray cannot make direct contact with the entire surface, fog nozzles use water and air pressure to produce a fine mist and can be used directly over a heated plating bath to rinse the workpiece which allows for simultaneous rinsing and replenishment of the evaporated losses from the tank, and fog nozzles are not used in barrel plating because of the part’s odd shape;

Rinsewater reuse -- Rinsewater picks up contaminants from the workpiece that was rinsed. The same water can be used again in a subsequent plating step if these contaminants do not interfere with the quality of that step. For example, in a nickel plating process, the same rinsewater stream was used for the rinses following the alkaline cleaning, acid dip, and nickel plating tanks. Instead of having three different rinse streams, only one stream was used, greatly reducing the overall rinsewater requirements;

Still rinsing involves immersing the workpiece in a still (no inflow or outflow) rinse tank following the plating bath. The concentrations of the plating bath constituents build up until they become sufficiently high for the rinsewater to be used to replenish the upstream plating bath:

Automatic flow controls control the rinse rate to as slow as possible to avoid variations associated with water line pressure changes and manual control by operator: and

Mechanical and air agitation of the rinsing bath increase the rinsing efficiency.

Metal Recovew Tectrniaues

Techniques to recover metals from rinsewater before treatment include:

p Evaporation;

Reverse osmosis;

Ion exchange;

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1 Elecvolysis; and

Electrcdialysis.

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Many companles have installed such systems to recover metals from waste rinsewater and have found that the investment has paid for Itself in one to five years. Strategic, in- line placement of metal recovery units, such as ion-exchanse columns, can serve to remove metals from spent plating baths and waste rinsewaters. When the ion-exchange resin is regenerated, the metals can be recovered and used to provide plating solutions which can be recycled to the plating baths.

Treatment Wastes

In electroplating, toxic metal sludges result from the conventional treatment processes used to remove metals from wastewater. The volume and toxicity of the sludge produced can be lowered by reducing the metal content in the plating and rinse wastewaters, or by using ditferent precipitating agents. Methods available to accomplish this include:

Use of different precipitating agents -- Normally, hexavalent chromium is treated by being reduced to trivalent chromium with a reducing agent, followed by precipitation with lime. In one instance, sodium hydroxide was used in place of lime which produced 1.98 Ib dry solids/lb Cr(VI) compared to 2.24 Ib dry solids/lb Cr(VI) produced by lime precipitation;

Use of Cr(III) instead of Cr(v1) for plating - One operation reported a 70% reduction in sludge production when trivalent chromium was used for plating instead of hexavalent chromium. This reduction occurred because the necessity to precipitate gypsum was avoided. Gypsum is associated with the excess sulfate ions that are normally added to reduce Cr(lV); and

Use of Separate Treatments - Use of separate treatments for each solution results in a sludge that bears a single metal. The sludge (metal hydroxide) can then be sold, e.g., to a chemical producer.

Wastestream Seareaation

Waste segregatior; is a good operating practice which can reduce the generation of wastes or optimize the reuse of wastestreams. For example:

By isolating cyanide-containing wastestreams from wastestreams containing iron or complexing agents, the formation of cyanide complexes is avoided, and treatment made much easier;

Segregating wastewater streams containing different metals allows for metals recovery or reuse. For example, by treating nickel plating wastewater

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separately, a nickel sludge is produced which can be reused to produce fresh nickel plating solution; and

a In one instance, the scrubber waste from a chromium plating bath was segregated and could then be returned to the bath. This resutted in less waste and increased plating solution life.

Product Substitution

Two possible product substitutions include:

Cadmium plating atterfiatives -- Cadmium-plared products are highly resistant to corrosion on land and in marine environments. Roughly 40% of the total cadmium produced is used by the US. military. It may be possible in some instances to replace cadmium plating with other materials such as: b zinc plating, b titanium dioxide plating using vapor deposition, and b aluminum plating using ion vapor deposition.

None of these coatings have exactly the same properties as cadmium, but some may prove to be satisfactory substitutes nonetheless: and

Chromium plating alternatives -- Substantial waste is produced during chromium plating; therefore, eliminating any unnecessary use is beneficial. For example, chromium-plated car bumpers can be replaced by nickel- plated bumpers, although customer preference for a shinier finish may play a major role.

Reduction Options From Assessment of Electroplating Operation .......... -.-__..- ..................... , ............. -- --.........- ".................."........................................." ..... - .................................................................. The following case study is an example of a waste reduction assessment of a

metal plating operation. This example is reconstructed from an actual assessment. The example describes the waste reduction options that are identified and recommended for this facility.

After the site inspection was completed and additional information was reviewed, the team held a brainstorming session to identify potential waste reduction options for the facility. The following options were proposed during the meeting:

Reduce solutior? drag-out from the plating tanks by: b

b increasing plating solution temperatures, b

b

proper positioning of workpiece on the plating rack, ,

lowering the concentration of plating solution constituents, and increase the recovery of drag-out with drain boards;

Extend plating solution bath life by: b reducing drag-in by better rinsing,

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7 R 1 '3 3 :-I 0 1 3 3 L. -1 3 3 J 1 zl

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c using deionized make-up water,

b

L using purer anodes, and returning spent solutions to the suppliers;

Reduce the use of rinsewater by: t using multiple counter-current rinse tanks, b using still rinsing, and b using spray or fog rinsing;

Prevent dust from the adjacent buffing and polishing room from entering the plating room and contaminating the plating baths: and

Cp Segregate cyanide wastes from the rinse tanks from other wastewater streams, such as floor washings and paint stripping wastes.

The team members each independently reviewed the options and then met to decide which options to study further. The team chose the following options for the feasibility analysis:

Reduce drag-out by using drain boards:

a

Extend bath life using deionized water for make-up;

Use spray rinsing to reduce rinsewater usage; and

Segregate hazardous waste from nonhazardous waste.

Feasibili AnatvsiS

The assessment team conducted technical and economic feasibility analyses on each of the four options. These analyses inctuded:

Use Drain Boards to Reduce Drag-out -- Drain boards are used to collect plating solution that drips off the rack and the workpiece after they are pulled out of the plating tank. The plating solution drains back into the plating tank. This option reduces the a-mount of dilute rinsewater waste, but impurities build up faster in the plating solution. Since drag-out is reduced, make-up chemical consumption is reduced.

The purchase price of drain boards is estimated at $1 15, with installation costs of $200, for a total capital cost of $315. This option is expected to reduce rinsewater disposal costs by $500 per year, and reduce make-up chemicals costs by $400 per year. The resulting payback period is 0.35 years, or about 4 months;

Use Deionized Water for Make-up Solutions and Rinsewater -- Using . deionized water will reduce the build-up of impurities in the plating solutions.

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In panicular, the build-up hardness " m k from tap water will be avpided. Tnis, in turn, will avoid the precipitation of carbonates In the plating tanks. The assessment team decided to combine the e v a h " of this option with :he Drevious omon of using drain boards. The Initial purchase and mrallaticn of the deionizer was $267. When adding the cost of the drain Doards, the total capital cost of this option is 5582. The deicnizer is rented and sewiced by an outside water treating service company for $450 per year. The savings in disposal costs and make-up chemical costs is $900 per year. Therefore, the annual net operating C O S savings 1s $450 per year. The payback period is 1.3 years;

Install Spray Rinses -- Installing spray rinses will reduce the amount of rinsewater required to clean the items. With spray rinse nozzles and controls, rinsing can be done on demand. Rinsewater usage was estimated to be reduced by 50%. The resulting rinse WaStewater is more concentrated and some can be returned to the plating tanks as a water make-up.

The assessment team determined that four spray rinse units would cost S2,120, plus an additional $705 for piping, valves, and installation labor. The total capital cost was $2,825. The reduction in disposal costs were estimated at $350 per year, based on a 50% reduction in rinse wastewater. This resulted in a payback of over 8 years; and

Segregate Hazardous Wastes -- The assessment team recognized that segregating hazardous wastes from nonhazardous wastes could be implemented at virtually no cost and would save money immediately. There were no identified technical problems.

ImDlementation

The procedures for segregating hazardous wastes from nonhazardous wastes were implemented before the feasibility analysis was completed for the other three options. The installation of drain boards and the purchase of a water deionizer were made shortly after the feasibility analysis was completed. The deionized water system was on-line two months later. The assessment team decided not to implement the spray rinse option because of the long payback period.

Future Waste Reduction Assessment

During the next cycle of waste reduction assessments, the assessment team will review previously suggested options in the plating area and will look at ways to reduce the generation of metallic dust in the buffing and polishing area. In the 'meantime, the assessment team will continue to look for additional opportunities to reduce waste throughout the facility.

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the massachusetts toxics use reduction institutesulfonic acid baths are less corrosive and less...

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