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Separation techniques

المادة العلمت

همت البدوي/ د

جىزاء الطىهر/أ

:كتابت نقلته

أمنه العبدان/أ

زهرة البلىي/ أ

نهى الجهن/ أ

عائشت السمري/أ

وفاء الجعد/ أ

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SOLVENT EXTRACTION

GENERAL DISCUSSION

Solvent extraction involves the distribution of a solute between

two immiscible liquid phases. This technique is extremely useful

for very rapid and "clean" separations of both organic and

inorganic substances. The separation that can be performed are

simple, clean, rapid and convenient. In many cases separation may

be effected by shaking in a separatory funnel for a few minutes.

1-The distribution coefficient

A solute S will distribute itself between two phases(after shaking

and allowing the phases to separate)and, within limits, the ratio of

the concentrations of the solute in the two phases will be a constant

KD = [S]1/[S]2

Where KD the distribution coefficient and the subscripts represent

solvent 1 (e.g. an organic solvent) and solvent 2 (e.g. water). If the

distribution coefficient is large, the solute will tend toward quantitative

distribution in solvent 1 .

In the practical application of solvent extraction we are interested

primarily in the fraction of the total solute in one or other phase, quite

regardless of its mode of dissociation, association, or interaction with

other dissolved species.

2-The distribution ratio

It is more meaningful to describe a different term, the distribution ratio,

which is the ratio of the concentrations of all the species of the solute in

each phase. In this example, it is given by:

D = [Cs]1/[Cs]2

3- The percent extracted

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The fraction of solute extracted is equal to millimoles of solute in the

organic layer divided by the total number of millimoles of solute. The

millimoles are given by the molarity times the millimiters. Thus, the

percent extracted is given by:

%E = [S]0V0/[S]0V0+[S]aVa×100%

Where V0 and Va are the volumes of the organic and aqueous phases,

respectively. It can be shown form this equation that the percent extracted

is related to the distribution ratio by:

%E = 100D/D+(Va/V0)

The apparatus used for solvent extraction is the separatory funnel

illustrated in figure 1. Mostoften, a solute is extracted form an aqueous

solution into an immiscible organic solvent. After the mixture is shaken

for about a minute, the phases are allowed to separate and the bottom

layer (the denser solvent) is drawn off in a completion.

EXPERIMENT 1 : Separation of iodine

You will be given a homogenous mixture of iodine and sodium chloride

in distilled water.

Discussion

The iodine is separated by an extraction process. The aqueous iodine-salt

solution, is shaken together with an approximately equal volume of

carbon tetrachloride (CCL4). Water and carbon tetrachloride do not mix

(they are insoluble in one another)hence two liquid phases will coexist

here. Iodine vastly prefers to dissolve in CCl4, thus it migrates from the

aqueous(H2O) phase into the non –aqueous (CCl4) phase – we say that

CCl4 "extracts" the I2 from the aqueous phase. Cl has no such tendency

(its solubility in CCl4 is nil) and hence it remains behind in the water

phase.

PROCEDURE

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1-Pour all of filtrate into a clean 125 ml separatory funnel (suspended in

an iron ring on a ring stand) whose stopcock is closed.

2- pour in 20 ml of carbon tetrachloride,

3-Watch the added liquid to see whether it dissolves, floats as an upper

layer, or settles as a lower layer.(Which liquid has the greated density.

CCl4 or H2O?). insert the separatory funnel stopper, and shake the closed

funnel for about sec.(Fig.2).Shake vigorously enough so as to mix the

aqueous and non-aqueous phases intimately. Keep your hand on the

stopper; if internal pressure builds up, the stopper may pop out. To vent

the insife pressure, hold the stopped separatory funnel upside down, allow

the liquids to drain away from the stopcock, and which the tip still

pointing up, open the stopcock momentarily.

Close the stopcock , turn the separatory funnel upright, remove the top

stopper, and allow the layers to separate as completely as possible.

Carefully drain the layer through the stopcocker closing it just before the

last drop og lower layer goes through . What will the lower layer be?

Add another 20ml portion of fresh CCl4to the remaining upper layer and

repeat once more, drawing the second batch of CCl4 into a separate

container . (Why must remove the top stopper from the separatory funnel

each time before attempting to drain out the lower layer?). Repeat a third

time.

Separately save the second and third portions of CCl4, note and compare

their color with the first portion. Show these carbon tetrachloride

solutions to your laboratory instructor. Save the aqueous layer.

IODINE TEST

In the presence of iodine , the white color of the starch paper changes to

deep blue Dip your stirring rod into the solution and then touch it to a

piece of the starch paper. Be sure your stirring rod is thoroughly rinsed

before and after each use.

CHLORIDE TEST

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To a test tube containing the sample (the aqueous layer), add 2 drops of

(AgNO3). You will observe a precipitate.

EXERCISE

Suggest a volumetric method for the determination of iodine and chloride

after the separation. Discuss the theory of the indicator used in each

method.

Experiment2:Determination of nickel as the dimethylglyoxime

complex

:Discussion

Nickel ( 200_400 microgram)forms the red dimethylglyoxime complex

only slightly soluble Alkaline medium; it is

in chloroform (35_50 g/L) NiCl

The optimum pH range for extraction of the nickel complex is 7_12 in the

presence of citrate . The nickel complex absorbs at 366 nm and also at

465_470 nm .

Chemicals:

Ammonium nickel sulphate (0.135 g ),citric acid (A.R.)5 g, ammonia,

dimethylglyoxime,chloroform and aluminium salt.

Procedure :

A homogenous solution of nickel (200_400 ug)ang aluminium (500 ug

)or iron (500 ug )is prepared.Transfer10.0ml of this solution (Ni content

about 200 ug) to a beaker containing 90 ml of water,add5.0g of A.R.citric

acid, and then dilute ammonia solution until the pH is 7.5.cool and

transfer to a separatory funnel,add20 ml of dimethylglyoxime

solution(1)and, after standing for a minute or two,12ml of chloroform.

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Shake for l minute,allow the phases to sette out, separate the red

chloroform. Shake for l minute, allow the phases to settle out, separate

the red chloroform layer, and determine the absorbance at 366 nm in a

1.0.cm absorbance cell against ablank .Extract with a further 12ml of

chloroform and measure the absorbance of the extract at 366 nm ; very

little nickel will be found .Test for the iron or aluminium in the aqueous

layer .

Repeat the experiment in the presence of 500ug of iron (III)and 500ug of

aluminium ion ; on interference will be detected.

Note:

The dimethylglyoxime reagent is prepared py dissolving 0.50g of A.R.

Dimethylglyoxime in 250ml of ammonia solution and diluting to 500 ml

with water.

Report

:1- complete

a-Distribution coefficient is……………

b-Distribution ratio is …………………….

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c-if a solute undergo association,dissociation

or polymerization,isused instead of…………….

2- Like dissolves like. Explain and give examples..

3- Although Ni+2 is an inorganic cation,it can be extracted in

chloroform. Explain

4- Amixture contains ontains only 250ug of Ni and 250ug of fe .can

nickel(II)be separated from iron(III) by solvent extraction and

determined qualitatively?

Experiment 3:Determination of Iron by chloride Extraction

Discussion

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The extraction of iron (III) chloride from hydrochloric acid with diethyl

ether (probably as the solvated complex H[feCL4]) has long been known,

but the amount of metal extracted depends upon the concentration of the

acid and passes through a maximum at about 6M-hydrochloric acid

Elements that extracted well as chloride complexes include

sb(V),As(III),Ga(III),Ge(IV), TI(III),Hg(II) ,Mo(VI),Pt(II),and

Au(III).Elements which are partially extracted include

Sb(III),As(V),V(V),co(II),sn (II),and Sn(IV).many solvents with donor

oxygen atom, including di-isopropyl ether, B,B-dichloro-

diehtylether,ethyl acetate, butyl acetate, and pentyl acetate, have been

employed.

in most cases the optimum extraction depends upon the acid

concentration.

The extraction of large amounts of iron is conveniently made with iso

butyl acetae : this solvent has the merit of low volatility and of almost

negligible temperature rise during the extraction (unlike diethyl ether )

To gain experience in the procedure, experimental details are given for

the extraction of iron (III) in hydrochloric acid solution with diethyl ether

.

Procedure:

Weigh out 16.486 gm of A.R. hydrated ammonium iron (III) sulephate

and dissolve it in 250ml of 6M _hydrochloric acid in a graduated flask .

Extract,25.0 ml of the iron(III) solution (which contains 200mg of fe )

with three 25-ml portions of pure diethyl ether (1): shake gently for 3

minutes during each extraction . combine the three ether extracts and strip

the iron from the ether by shaking with 25 ml of water : approximately

99.9% of the iron is removed by this method. Boil off any ether

remaining in the aqueous extricate on a water bath (caution) , and

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determine the iron by titration with standard 0.1 N-potassium dichromate

after previous reduction to the iron (II)state . The iron recovered should

not be less than99.6 %(2)

Notes:

1- The factors of importance in the diethyl ether extraction of iron are :

a- The iron must be in iron (III) state , since iron (II) chloride is not

extracted .

b- The hydrochloric acid concentration must be close to 6M .

c- The extraction should be carried out in subdued light , since ether

photochemicaly reduces iron (III).

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d- The ether should be free from ethanol and peroxides because these

reduces the ion (III) chloride.

e- The concentration of anions other than chloride should be kept low.

f- Heat is generated be the mixing of the ether and the hydrochloric acid-

iron(III)chloride solution so that cooling of the mixture under the tap or in

ice is essential.

2- The procedure may be adapted to the determination of iron in an iron

ore or a steel . The details are as follows. Dissolve a 0.5gm sample ,

accurately .weighed , in 25 ml of 6M –hydrochloric acid and 4ml of

concentrated nitric acid by heating the mixture on a water bath .

Evaporate the solution to dryness and then dissolve the residue in 15mlof

1:1 hydrochloric acid. Transfer the solution to a continuous extractor and

rinse the vessel with a little 6M-hydrochloric acid Extract the solution

with diethyl ether or with peroxide-free di-isopropyl ether until the ether

iayer above the solution is colorless . Transfer the ethereal solution of the

iron (III) chloride to a separatory funnel, strip the iron from the ethereal

solution by two or three washings with an equal volume of water.

Determine the iron content as above.

Chromatography

Chromatographic techniques may be used for the separation and

analysis of mixture of gases, liquids, or solids . All chromatographic

techniques utilize a tow phase system, one stationary and one mobile .

Separation of the components between the two phase . The process

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differs from ion exchange in that, transfer of a component from the

mobile phase to the stationary phase does not result in the transfer of an

equivalent quantity of a component originally on the stationary phase,

into the mobile phase . In chromatography the stationary phase is

chemically unchanged after the separation process . The elute will only

contain compounds which were present in the original solution or

mixture, no chemical change will have occurred .

The stationary phase may be a solid , or a liquid supported on an inert

solid . The mobile phase may be a gas or a liquid . Accordingly several

types of chromatographic procedures are recognized :

1 – liquid-solid chromatography .

2- Gas-solid chromatography.

3- Gas-liquid chromatography.

4- Liquid-liquid chromatography, a special case of which is known as

paper chromatography . In paper chromatography the stationary phase is

water supported by the cellulose of the paper .

Experiment 1 : chromatography , ascending the separation of pH

indicator mixture

Principle :

To demonstrate the characteristic . invariable movement of a compound

regardless of whether it is alone or in a mixture with other compounds

which separate well from it .

Running time :

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At least 1 hour .

Chemicals :

Methyl orange

Ph.ph

Bromphenol blue

Solvents :

Either (a) n-butanol : ethanol : 2M ammonia

( 60 : 20 :20 by volume )

Or ( 60 : 20 : by volume )

(b) n-butanol :acetic acid glacial : water

( 60 : 15 : 25 by volume ) .

Locating agent : Ammonia .

Procedure :

1- Place 50 ml of the chosen solvent at the bottom of the tank and

replace the lid.

2- Prepare a 25 × 25 cm sheet of paper and apply one drop of each of

the three individual indicators and one drop of the mixture

separately to four origins , using the wire loop .

3- Form the paper into a cylinder and dasten with the tongued clips ,

part G .

4- Hold the origins over ammonia fumes to produce the alkaline color

forms of the indicators i.e. the indicator anions .

5- Place the cylinder rapidly into the tank , before the indicators can

revert to their free acid forms . This is important as the free acid

from may travel with an Rf value different from that of the ionic

form . Do not allow the paper to touch the glass walls .

6- Put the lid on and run solvent for at least one hour . Watch the

initial flow of solvent across the origin and note the immediate

commencement of separation of the indicators in the mixture .

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7- Remove the chromatogram and make the solvent front with a

pencil .

8- Dry the chromatogram .

9- Observe that the mixture of indicators has separated into its three

individual components . Observe the different level reached by

each indicator in the mixture and compare each with the level

reached by the same indicator running by itself from one of the

other origins . Note that the level is the same for each pair of

indicator , regardless of whether they started alone or in mixture

with the other indicators .

Conclusion :

When two or more substances , in a mixture with each other , are

subjected to paper chromatography , each will run independently of the

others and will proceed to the same point that it would have reached had

it been run by itself.

Notes :

1- If the indicators are run in the free acid from they travel to quite

different positions . This can be confirmed by experiment .

2- In this experiment the substances are substances are well separated

. However, in multicomponent mixtures of complex chemical

substances it is likely that some of the components will , at the end

of the run , be found to be located in similar position . Their Rf

values will then be found to differ slightly from the Rf of the

substances run either alone or in simple mixtures .

3- The dyes, also separate well in solvent (a) and can usefully be

included in this experiment .

Report

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Compute and compare the Rf values of each pH indicator

Other experiments were made using the book

Column chromatography

By this method the stationary phase is loaded into a vertical column ,

usually glass, and the moving phase is allowed to flow down it by gravity

or under pressure. In adsorpation chromatography , the substrate is

adsorbed directly on to the solid stationary phase and the liquid, mobile

phase competes with it for the substrate .

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A variety of organic and inorganic liquids is used adsorption

chromatography . The eluting power of a solvent depends on its dielectric

constant which is an approximate measure of solvent polarity.

A mixture of the substance to be separated is dissolved in a small amount

of solvent and added to the top of the column. An equal volume of

solvent is removed form the lower end of the column thus allowing the

mixture to enter the column . The upper portion of the tube is filled with

eluting solvent , and solvent (elute) is continuously removed from the

lower end of the column . The separation process can now take tow

forms:

(1)Elution is continued a clear separation of the components of the

mixture can be seen ; examination of the column under UV light may

facilitate this observation . once a separation has been obtained the

stationary phase can be extruded and that potion of the stationary phase

carrying the compound extracted with a suitable solvent. Obviously this

method is most suitable for colored compounds .

(2)Elution is continued until the various components are eluted from the

column aliquot of the eluate are collected and tested for the compenent of

the mixture. Those portion of the elute containing the same compound

may be combined and the compound extracted by some suitable method ,

e.g. evaporation , precipitation , or liqud-liqud extraction .

The glass column used should have a means of supporting the stationary

phase. Commercial columns process either a porous glass plate fused

onto the base of the column , or a suitable device for supporting a

replaceable nylon net which in turn supports the stationary phase.

Packing of column :

Packing a column is normally carried out by gently pouring a slurry of

the stationary phase into a column which has its outlet closed , whilst the

upper part of the slurry in the column is stirred and /or column is gently

tapped to ensure that no air bubbles are trapped and that the packing

settles evently. Poor column packing give rise to uneven flow and

reduced resolution . the slurry is added until the required height is

obtained .

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Once the required column height has been obtained , the flow of solvent

through the packed column is started by opening the outlet , and

continued until the packing has completely settled. To prevent the surface

of the column from being disturbed either by addition of solvent to the

column or during the application of the sample to the column , it is

normal to place a suitable protection device, such as a filter paper disc or

nylon or rayon gauze, on the surface of the column . once column has

been prepared, it is imperative that no part of it should be allowed to run

dry i.e. a layer of solvent should always be maintained above the column

surface .

Application of the sample :

The sample is first dissolved in the solvent before loading it into the

column . In most experiments, the sample is carefully applied by

capillary tubing and syringe or pump to pass the sample directly to the

column.

This part wasn't performed due to deficiency of chemicals year

2010/2011

Ion exchange

Properties of Ion Exchange

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Ion exchangers operation is dependent upon certain properties of the system. Each

property has an affect on the efficiency and productivity of an ion exchanger. Below

are select properties which affect the system.

The density of resin has an affect upon how the system performs. Properties of resin

should be understood. For example, the density of the dry, water free resin is

generally smaller for anion exchangers than cation exchangers. The density of water

swollen resin depends on the type counter ion, swelling capacity and on the degree of

crosslinking, besides the density of dry resin. Furthermore, it should be noted that

bulk density is different than the density of the swollen resin. These densities are

important because operation is dependent upon the resins.

The mechanical resistance is a variable that is studied for ion exchangers. The

mechanical resistance is found to vary with structure of the system. It should be noted

that air dried resin is destroyed by certain friction. This needs to be thought of in

design stages.

The grain size, is a major part of the fluid flow and effectiveness of seperation of

systems. For example, condensation type resins are generally broken granules. On the

contrary, polymerization-type resins are small beads that are uniformally packed. To

measure the grain size a mesh is used to keep out larger particles. In addition, for

certain processes grain size is extremely important to efficiency. One such process is

seperations carried out by chromotography. The major point of study of grain size is

that it determines the fluid resistance of an ion exchange column made from ion

exchange resin. This can be the key to success of an industrial operation.

The total capacity is a measurement tool used to rate an ion exchanger. The total

capacity is the amount of exchangeable ions of unit weight of resin. The determination

of such factor is done by acid-base titration. Another capacity is salt splitting. This is

the amount of sodium ions absorbed by the cation exchanger in the hydrogen form

from a sodium chloride solution or hydrogen released by unit weight or unit volume.

For an anion exchanger the amount of base liberated from a salt by unit weight or

unit volume of the hydroxyl-form anion-exchange resin. Dissociation constants of

active groups of the resin is a major part of the salt splitting capacity. Further, noted

is the rest capacity which consists of the difference in monofunctinal strongly acidic

or basic resin of splitting capacity. Also, the apparent capacity can be defined as the

affects of multivalent anions on anion exchanger. Further, the break-through capacity

depends on the pH, grain size, column size and flowrate. These capacities are

properties of a system. Knowing and understanding the capacities allows for proper

design.

The porosity of a system controls much of the capacity of the exchanger. The surface

active groups and capillary groups take part in the characteristics of a ion exchanger.

The pores of IERs are of variable size even for the same resin product. Due to

porosity, the affects on capacity of greater sized ions is because of the sieve effect.

The determination of porosity can be done by means of solution containing ions of

known size and similarity by using capacity measurements. Also, the same

measurement can be done by the use of vapor pressures. Although, these methods

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only measure mean particle size, it results in useful knowledge. In addition to the

above, it should be noted that crosslinking affects mean pore size.

The operating rate is essential to chemical engineers. Knowing the affects of

controlling the flow is desireable also. For example, natural zeolite exchangeres

operate slower and an ion exchanger of larger pores quicker. A cation exchanger is

also knowed to set up equilibrium quicker. One may image that the process is

controlled by the chemical reaction. But it is known that the diffusivity is a controlling

factor. In addition, the rate depends on diffusivity constants of active groups of the

resins. Other effects are on account of temperature and looseness of crosslinks

Ion Exchange Columns Aim To plot the breakthrough curve of strong acid cation exchange Amberlyst resins, and

determine their capacity by batch and continuous flow processes.

Theory Ion Exchangers

Of all different natural and synthetic products which show ion exchange properties, the most

important are

ion-exchange resins, ion-exchange coals, mineral ion exchangers, and synthetic inorganic exchangers. Ion

exchangers owe their characteristic properties to a peculiar feature of their structure. They

consist of a framework held together by chemical bonds or lattice energy which carries a positive or

negative surplus

charge. Counter ions of opposite charge move throughout the framework and can be replaced

by other ions of same sign. For example, the framework of a cation exchanger can be regarded as a

macromolecular or

crystalline polyanion, while the framework of an anion exchanger can be regarded as a polycation.

Ion Exchange Resins

These constitute the most important class of ion exchangers. Their frame-work called the matrix, consists

of an irregular, macromolecular, 3-D network of hydrocarbon chains. The matrix carries

ionic groups such

as SO32-

, COO− in cation exchangers and NH+3 , NH+2 in anion exchangers. Ion exchange

resins are thus

cross linked polyelectrolytes. The matrix of the resins is hydrophobic. However, hydrophilic

components are introduced by the incorporation of ionic groups such as SO3H. Linear hydrocarbon

macromolecules

with such molecules are soluble in water. So ion exchange resins are made insoluble by introduction of

cross-links which Interconnect the various hydrocarbon chains. An ion-exchange resin is

practically one

single macromolecule . Its dissolution would require rupture of C-C bonds. Thus resins are insoluble in all

solvents by which they are not destroyed. The matrix is elastic and can swell by taking up

solvent , a fact referred to as ”heteroporosity” or ”heterodictality”.

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The chemical, physical, and mechanical stability and the ion-exchange behavior of the resins

depend primarily on the structure and the degree of cross-linking of the matrix and on the nature and number

of fixed ionic

groups. The degree of cross-linking determines the mesh width of the matrix and thus the

swelling ability of the resin and the mobility of the counter ions in the resin, which in turn determine the rates of

ion-exchange

in the resin. Highly cross linked resins are harder and more resistant to mechanical breakdown.

Amberlyst-15 with sulphonic acid functionality is our resin of interest. It is a highly porous,

macro reticular ion-exchanger prepared by a variation of the conventional pearl-polymerization technique. In

pearl polymerization,

monomers are mixed, and a polymerization catalyst such as benzoyl peroxide is added. The

mixture is then added to an agitated aqueous solution kept at the temperature required for poymerization.

The mixture forms small droplets, which remain suspended. A suspension stabilizer is added

to prevent agglomeration of droplets. In the case of Amberlyst, an organic solvent which is a good

solvent for the

monomer, but a poor solvent for the polymer is added to the polymerization mixture. As polymerization

progresses, the solvent molecules are squeezed out by the growing copolymer regions. In this

way, spherical

beads with wide pores are obtained.

Selectivity

Ion exchangers prefer one species over another due to several causes :

1. The electrostatic interaction between the charged framework and the counter ions depend on the size

and valence of the counter ion.

2. In addition to electrostatic forces, other interactions between ions and their environment

are effective. 3. Large counter ions may be sterically excluded from the narrow pores of the ion exchanger

All these effects depend on the nature of the counter ion and thus may lead to preferential

uptake of a species by the ion exchanger. The ability of the ion-exchanger to distinguish between the various

counter ion species

is called selectivity.

Separation Factor

The preference of the ion exchanger for one of the two counter ions is often expressed by the

separation

factor, defined by… The molal selectivity coefficient , which is used for theoretical studies, is defined as….

The selectivity of the ion exchange process depends on the properties of the ion exchanger

used and the composition of the aqueous phase . In the case of two ions having the same charge and very

similar radii,

the selectivity due to the properties of the ion exchanger (such as acidity, basicity, and the degree of cross

linking ) is not sufficient for ensuring effective separation. In such a case, an appropriate

complexing agent

has to be added to the aqueous phase: the selectivity attained is then either due to the difference in the

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stability constants or to the different charges or structures of the complexes formed.

Increased selectivity can be brought about in many ways. For eg., one can exploit the preference of an exchanger

for highly

charged ions in dilute solutions, or one can choose a chelating resin.

Capacity Capacity is defined as the number of counter-ion equivalents in a specified amount of

material. Capacity

and related data are primarily used for two reasons:- for characterizing ion-exchange materials, and for use

in the numerical calculation of ion-exchange operations. Capacity can be defined in

numerous ways: 1. Capacity (Maximum capacity, ion-exchange capacity) Definition : Number of inorganic

groups per

specified amount of ion-exchanger

2. Scientific Weight Capacity Units : meq/g dry H+ or Cl− form 3. Technical Volume Capacity Units: eq/liter packed bed in H+ or Cl− form and fully water-

swollen

4. Apparent Capacity (Effective Capacity) Definition : Number of exchangeable counter ions per specified

amount of ion exchanger.

Units : meq/g dry H+ or Cl form (apparent weight capacity). Apparent capacity is lower than maximum

capacity when inorganic groups are incompletely ionized ; depends on experimental

conditions

(pH, conc. ,etc) 5. Sorption Capacity. Definition : Amount of solute , taken up by sorption rather than by

exchange, per

specified amount of ion exchanger 6. Useful Capacity Definition : Capacity utilized when equilibrium is not attained Used at low

ionexchange

rates Depends on experimental conditions (ion-exchange rate, etc.)

7. Breakthrough Capacity ( Dynamic Capacity) Definition : Capacity utilized in column operation, Depends

on operating conditions

8. Concentration of fixed ionic groups Definition : Number of fixed ionic groups in meq/cm3 swollen

resin (molarity) or per gram solvent in resin (molality) Depends on experimental

conditions(swelling, etc.) Used in theoretical treatment of ion-exchange phenomena

…………..

Qv = volume cpacity in equivalents per liter packed bed. Qw = Scientific weight capacity in milliequivalents per gram.

b = fractional void volume of packing

W = water content of the resin in weight percent d = density of the swollen resin in grams per ml

B The molality of fixed groups in meq/g is

m =(100 − W) × Qw W × (1 + PQi−MQw × 10−3)

The molarity of fixed groups in meq/ml is

X =d × (100 − W) × Qw

100 × (1 + PQi−MQw × 10−3)

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Batch Process Apparatus

Stirred tank reactor with stirrer, belt, stand, pipette, resins, copper sulphate solution, test

tubes ( 15), ion

meter, cupric electrode, Ionic Strength Adjustor (ISA), volumetric flasks

Procedure

1. Calibrate the ion meter using cupric nitrate standards of concentrations 0.6355 ppm ,

6.355 ppm , 63.55 ppm , and 127.1 ppm.

2. Take known weight of resins in the stirred tank reactor. Fit the reactor on the stand and

attach the belt

to the stirrer which is adjusted on the pulleys. Switch on the stirrer . 3. Pour quickly calculated volume of 800 ppm cupric sulphate solution into the tank and start

the timer

. 4. Withdraw 1 ml samples from the tank using a pipette at every 40 seconds for about 10

minutes.

5. Dilute the samples to 50 ml in volumetric flasks and measure their concentrations using ion meter.

6. Plot a graph of concentration vs. time.

7. The amount of cupric ions consumed is calculated from the initial and final concentrations.

Calculations Initial concentration - C0 ppm

Final concentration - Cf ppm

Qty. of cupric ions used Q =(Cf − C0) × 250/1000000

Capacity of resins = (Q/63.55) eq/g of resin

Observation Table

S.N. Time (min) Cu ion concentration (ppm)

Graph Plot a graph of concentration versus time.

Continuous Process Procedure

1. Take 10 g resins and prepare a slurry with distilled water. Charge the column with the

slurry such that

there are no air bubbles trapped. 2. Keep adding cupric sulphate solution to the resin, and let it flow out at approximately 1

ml/min.

3. After every 20 ml, measure out 1 ml of effluent, dilute it to 50 ml in the volumetric flask and measure

its concentration in the ion meter.

4. A graph of concentration versus volume is plotted .

Observation Table

S.N. Time (min) Cu ion concentration (ppm)

Graph

Plot a graph of concentration versus time.

Results and Comments