tengku nur zulaikha-thesis psm 20102011
TRANSCRIPT
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RECOVERY OF SILVER FROM PHOTOGRAPHIC WASTE USING
EXTRACTANT IMPREGNATED RESIN (EIR)
TENGKU NUR ZULAIKHA BT TENGKU MALIM BUSU
UNIVERSITI TEKNOLOGI MALAYSIA
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UNIVERSITI TEKNOLOGI MALAYSIA
NOTES: * If the thesis is CONFIDENTAL or RESTRICTED, please attach
with the letter from the organization with period and reasons for confidentiality orrestriction.
DECLARATION OF THESIS AND COPYRIGHT
AUTHORS FULL NAME : TENGKU NUR ZULAIKHA BT
TENGKU MALIM BUSU
DATE OF BIRTH : 03RD APRIL 1988
TITLE : RECOVERY OF SILVER FROM PHOTOGRAPHIC
WASTE USING EXTRACTANT IMPREGNATED
RESIN (EIR)
ACADEMIC SESSION : 2010/2011
I declare that this thesis was classified as:
CONFIDENTIAL (Contains confidential information under the Official
Secret Act 1972)*
RESTRICTED (Contains restricted information as specified by the
organization where research was done)*
OPEN ACCESS I agree that my thesis to be published as online open access
(full text)
I acknowledged that Universiti Teknologi Malaysia reserves the right as follows:
1. The thesis is the property of Universiti Teknologi Malaysia.2. The Library of Universiti Teknologi Malaysia has the right to make copies for the
purpose of research only.
3. The Library has the right to make copies of the thesis for academic exchange.
CERTIFIED BY:
880403115258 PM DR. HANAPI BIN MAT
(NEW I.C. NO.) (NAME OF SUPERVISOR)
Date: Date:
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I hereby declare that I have read this thesis and in my opinion this thesis issufficient in terms of scope and quality for the award of the degree of Bachelor of
Engineering (Chemical)
Signature :
Name : PM DR. HANAPI BIN MAT
Date :
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RECOVERY OF SILVER FROM PHOTOGRAPHIC WASTE USING
EXTRACTANT IMPREGNATED RESIN (EIR)
TENGKU NUR ZULAIKHA BT TENGKU MALIM BUSU
A thesis submitted in fulfillment of the
requirements for the award of the degree of
Bachelor of Engineering (Chemical)
Faculty of Chemical Engineering and Natural Resources Engineering
Universiti Teknologi Malaysia
OCTOBER 2010
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DECLARATION
I declare that this thesis entitled Recovery of Silver from Photographic Waste Using
Extractant Impregnated Resin (EIR) is the result of my own research except as cited
in the references. This thesis has not been accepted for any degree and is not
concurrently submitted in candidature of any other degree.
Signature :
Name : TENGKU NUR ZULAIKHA BT
TENGKU MALIM BUSU
Date :
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To my beloved parents and siblings
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ACKNOWLEDGEMENTS
First and foremost, I would like to acknowledge the undergraduate projects
supervisor, Assoc. Prof. Madya Dr. Hanapi bin Mat for his supervision and support
through out the project period. He gave many guidelines and sources in order to help
me complete the experimental part and discussion on the result gotten.
I am also very thankful to my friends with under same supervisor for giving
ideas to help me complete the research in the time being. We shared our sharing joys
and frustration during this time. Thank you very much. Special thanks are also
dedicated to Encik Yasin for helping me in sample analyzing.
Finally, I thank my beloved parent, Tengku Malim Busu and Salmah andsiblings for their understanding and support in almost everything. Sorry for my
careless love for all of you during the time I accomplished this research.
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ABSTRACT
The field of adsorption by Extractant Impregnated Resin (EIR) is recently
undergoing many researches in industrial separation technology especially heavy
metal recovery. This study is carried out to recover one of the metal which is silver
from photographic waste as it has economic value and its toxicity that will cause a
serious problem to the environment. The adsorption using Extractant Impregnated
Resin (SIR) was used to extract silver from synthetic and real photographic waste.
EIRs were prepared by using Amberlite XAD-2 and XAD-7 as polymer matrices,
ethanol and kerosene as diluents and Cyanex302 as extractant agent. The
unmodified and modified XAD-2 and XAD-7 adsorbents were analyzed using
Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope
(SEM) analysis. The adsorption of Ag(I) in silver solution using EIRs was
conducted in a batch system. Atomic Absorption Spectrophotometer (AAS) was
used to analyze the concentration of silver solution before and after adsorption
process. The parameters governing the performance of adsorption of silver that been
investigated were pH, type of diluents and type of polymer adsorbents. The result
shows that EIR XAD2-Cyanex302 and EIR XAD7-Cyanex302 with diluents
kerosene have higher capacity of silver adsorption. Adsorption of Ag(I) at varies
initial pH of silver solution shows that adsorption performance using EIR does not
depend on pH. Kinetic adsorption shows that maximum time required for achievingequilibrium condition is 34 hours. In the photographic waste, adsorption of Ag(I)
using EIR XAD7-Cyanex302 (kerosene) has higher capacity and selectivity towards
silver than other metals.
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TABLE OF CONTENTS
CHAPTER TITLE PAGE
TITLE PAGE i
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENTS iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES xi
LIST OF FIGURES xii
LIST OF SYMBOLS xiv
LIST OF ABBREVIATIONS xv
LIST OF APPENDICES xvi
1 INTRODUCTION
1.1 Research Background 1
1.2 Objectives and Scope of Research 2
1.3 Thesis Outline 3
1.4 Summary 4
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2 LITERATURE REVIEW
2.1 Introduction 5
2.2 Silver Metal 6
2.2.1 Introduction 6
2.2.2 Application of silver metal 6
2.3 Silver in Photographic Waste 8
2.3.1 Introduction to photographic waste 8
2.3.2 Photographic waste management 9
2.4 Process of Silver Recovery 102.4.1 Introduction 10
2.4.2 Electrolysis 11
2.4.3 Metallic replacement 12
2.4.4 Chemical precipitation 12
2.4.5 Ion exchange 13
2.4.6 Reverse osmosis 14
2.4.7 Evaporation 15
2.5 Adsorption Process in Silver Recovery 17
2.5.1 Introduction 17
2.5.2 Adsorption equilibrium 18
2.5.3 Adsorption kinetic 19
2.6 Adsorbent for Silver Recovery 20
2.6.1 Type of adsorbent 20
2.6.2 Functionalization of adsorbent 21
2.6.3 Extractant Impregnated Resin (EIR)
for silver recovery 22
2.6.3.1 Basic principles 22
2.6.3.2 Extraction mechanism 23
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2.6.3.3 Advantages of extractant impregnated
resin (EIR) 23
2.6.3.4 Current applications of Extractant
Impregnated Resin (EIR) 24
2.7 Summary 26
3 METHODOLOGY 27
3.1 Introduction 27
3.2 Chemicals 27
3.3 Experimental Procedures 29
3.3.1 Preparation of pure resin 29
3.3.2 Impregnation procedure 29
3.3.3 Characterization of Extractant Impregnated0
Resin (EIR) 31
3.3.4 Adsorption of silver Extractant Impregnated
Resin (EIR) 30
3.3.5 Analytical Procedures 31
3.3.5.1 pH determination 31
3.3.5.2 Silver content analysis using
Atomatic Absorption Spectrophotometer (AAS) 31
4 RESULT AND DISCUSSION 34
4.1 Introduction 34
4.2 Extractant Impregnated Resin (EIR) Screening 35
4.2.1 Extractant, resin and solvent selection 35
4.2.2 Extractant Impregnated Resin(EIR)s
analysis
4.2.2.1 Functional Group Analysis using
Fourier Transform Infrared
Spectroscopy (FTIR) 36
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LIST OF TABLES
TABLE TITLE
PAGE
2.1 Chemical properties in photographic waste 82.2 Physical properties in photographic waste 9
2.3 Comparison of silver recovery method 16
3.1 Properties of extractant Cyanex 302 29
3.2 Properties of diluents kerosene and ethanol 29
3.3 Properties of Resin XAD-2 and XAD-7 30
3.4 The instrument set-up conditions for determination of
silver by AAS using air-acetylene method. 34
4.1 Characterization of metals in photographic waste before
and after adsorption process 50
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LIST OF FIGURES
FIGURE NO TITLE
PAGE
2.1 Electrolysis cell for electrolysis metal recovery 112.2 Metallic replacement metal recovery 12
2.3 Ion exchange metal recovery 14
2.4 Mechanism of adsorption and desorption process 17
2.5 Effect of temperature, pressure and concentration towards
adsorption capacity 19
2.6 EIR principle of a macroporous particle impregnated with a 16
complexing agent E 24
4.1 Chemical structure of extractant Cyanex302 37
4.2 Chemical structure of monomer Styrene DVB in
Amberlite XAD-2 38
4.3 Chemical structure of monomer acrylic in Amberlite XAD-7 38
4.4 IR spectra of pure resin XAD-2 and EIRs 39
4.5 IR spectra of pure resin XAD-7 and EIRs 40
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4.6 Scanning electron microscope pictures of
(a) unimpregnated Amberlite XAD-2 and
(b) impregnated XAD-2 (EIR) with kerosene solvent 42
4.7 Scanning electron microscope pictures of
(a) unimpregnated Amberlite XAD-7 and
(b) impregnated XAD-7 (EIR) with ethanol solvent 43
4.8 Silver adsorption process from silver solution by different
type of EIRs 45
4.9 Effect of initial pH in silver adsorption 47
4.10 General effect of pH on metal extraction 48
4.11 Kinetic adsorption of silver extraction by EIR for 72 hours 49
4.12 Extraction of metals from photographic waste 51
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LIST OF SYMBOLS
Ag - Silver
Cd(II) - Cadmium
Cu(II) - Copper
Fe(III) - Ferum
NaCl - Sodium Chloride
Ni(II) - Nickel
cP - Centipoice
ppm - Part per million
pHe - pH equilibrium
Ce - Final/ Equilibrium concentration
Co - Initial concentration
Qe - Amount of silver adsorbed at equilibrium
rpm - Rotation per minute
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LIST OF ABBREVIATIONS
AAS - Atomatic Absorption Spectrophotometer
EIR/SIR - Extractant/Solvent Impregnated Resin
EPA - Environmental Protection Agency
PRBs - Permeable Reactive Barriers
RCRA - Resource Conservation and Recovery Act
RO - Reverse osmosis
SEM - Scanning Electron Microscope
FTIR - Fourier Transform Infrared Spectroscopy
DVB - Divinyl benzene
IR - Infrared
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LIST OF APPENDICES
APPENDIX TITLE
PAGE
A1 Data of silver adsorption by different types of EIRs 59
A2 Data of silver adsorption by pH effect 60
A3 Data of kinetic adsorption of silver 61
A4 Data of metals adsorption for real photographic waste 61
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CHAPTER 1
INTRODUCTION
1.1 Research Background
Silver is very useful metal in industrial field. The demand for silver comes
primarily from three areas; industrial uses, jewelry and silverware, and photography.
These industries represent 95 percent of annual silver consumption. Silvers superior
properties make it a highly desirable industrial component in manufactured products.
Silvers artistic beauty and status make it one of the most romantic and sought after
precious metals (Northwest Territorial Mint, 2005). As a result of high demand of
silver, new technology needs to be developed to get silver from other sources due to
the limitation of silver resource.
From the article by Crystal et al. (1982), the survey by Goldman Environment
Consultant Inc. gave response about a revealing indication of how photographers
dispose of photographic. Most of them (76% of the respondents) do not employ any
form of silver recovery. This result was suspected by knowledgeable industry
informants, but has not previously been confirmed by survey. So, many
environmental organizations concern to invent the management of photochemical
waste. In order to reduce the silver loadings to the environment, effort need to be
devoted to both finding a more cost-effective disposal method and to changing the
attitudes of photographers about the importance of silver recovery.
Therefore, silver recovery from photochemical waste needs appropriate and
effective methods that can be implemented to make compliance with the waste
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discharge regulations as well as the economic advantages due to the increasing price
of the precious silver. In the earlier research, there were many methods to recover
silver for the solution such as electrolysis recovery, metallic replacement, chemical
precipitation, ion exchange, reverse osmosis and evaporation.
However, because of the disadvantages among these methods, the new
technology of adsorption was studied. The recent research show many successes in
recovery of precious metal by using extractant impregnated resin (EIR). Therefore,
silver recovery from photographic waste using extractant impregnated resin need to
be studied to improve its performance.
1.2 Objectives and Scope of Research
The main purpose of this study is to determine the possibility of developing
the adsorption by extractant impregnated resin (EIR) for silver recovery from
photographic waste. Besides that, this study have purpose to determine the
adsorption capacity of silver substance from synthesis EIR adsorption and to evaluate
the efficiency and selectivity of EIR silver adsorption for real photographic waste. In
order to achieve these objectives, a fundamental study of the process is to be
specifically studied as scopes of the research. Thus, the best method can be
determined to recover silver selectively from photographic waste.
First, the objective of this research is to modify the polymer adsorbent andcharacterized EIR which is modified adsorbent. Amberlite XAD-2 and XAD-7 were
used as matrix polymer (adsorbent) for EIR synthesis. Both resins were impregnated
with Cyanex 302 by using ethanol and kerosene as its solvents. The synthesized
EIRs were then characterized. SEM analysis was used in studying the effect of the
impregnation to the resin morphology. In order to identify the successfulness of the
EIR impregnation process, FTIR analysis was also been determined. For this
analysis, some of the functional group regarding to the Cyanex302 chemical
structure could be determined.
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Besides that, this research is done in order to determine silver adsorption of
silver solution by extractant impregnated resin (EIR). Several types of EIRs will be
tested to determine their performance in the adsorption of silver. Batch adsorption
process was used to determine Ag(I) adsorption. Silver aqueous solution (100ppm)
was prepared from Ag(I), 2.2M. After EIR selection, the suitable pH for silver
extraction will tested to get best performance of extractant impregnated resin (EIR).
The amount of Ag(I) adsorption was studied at varies pH in order to determine an
optimum pH for maximum adsorption capacity. In addition, In addition, kinetic
study also was carried out for determining the maximum time required to achieve
equilibrium.
Lastly, this research has purpose to determine the selectivity of the EIR into
real photographic waste. The EIR adsorbent that gave highest performance of
adsorption was selected as adsorbent in photographic waste. The adsorption process
for real photographic waste was done similar to silver solution.
1.3 Thesis Outline
This proposal consists five chapters. Chapter 1 gives a description of the
background of the study, which also defined the research objectives and scopes. A
literature review on silver in industry, photographic waste and some silver recovery
methods including Extractant Impregnated Resin (EIR) has been discussed in
Chapter II. Chapter III presents the methodology used throughout the study. Chapter
IV is the result and discussion on the lab experiment of the study. Lastly, the
conclusion and some useful recommendations have been proposed at the end of this
thesis in Chapter V.
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1.4 Summary
The photographic waste has many hazardous contaminations that can cause
environmental problems and shortage resource of precious metals. Therefore,several silver recovery methods have been reported to overcome the problems as
pollution controlled. In this study, silver recovery method using Extractant
Impregnated Resin (EIR) is chosen as an effective method because of its advantages
compared to other methods.
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CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
The highly used of heavy metal in industrial and other processes have
increased rapidly and caused large amount of waste. Thus, this scenario is causing
several serious pollutions in the environment. The presence of heavy metal in the
environment causes adverse effects to human health. Therefore, the toxic heavy
metal should be removed before discharge to environment. However, some of the
effluents may contain a small amount of precious metal such as gold, platinum and
silver. These metals are very valuable materials and only exist at a small amount in
the earth.
Besides being used as jewellery, precious metals also are widely used in the
industrial process such as electronic manufacturing, currency, dental filling and
photographic. Recycling of those waste sources is one of the best methods for
fulfilling a high demand of the precious metals. Several studies have been developed
for recovery of precious metal from several wastes including electrolysis, metallic
replacement, chemical precipitation, ion exchange, reverse osmosis and evaporation
(Nakiboglu et al., 2001).
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2.2 Silver Metal
2.2.1 Introduction
Silver is a metallic chemical element with the chemical symbol Ag and
atomic number 47. A soft, white, lustrous transition metal, it has the highest
electrical conductivity of any element and the highest thermal conductivity of any
metal. The metal occurs naturally in its pure, free form (native silver), as an alloy
with gold and other metals, and in minerals such as argentite and chlorargyrite. Most
silver is produced as a by-product ofcopper, gold, lead, and zinc refining.
2.2.2 Application of silver metal
Many well known uses of silver involve its precious metal properties,
including currency, decorative items and mirrors. The contrast between the
appearances of its bright white color in contrast with other media makes it very
useful to the visual arts. It has also long been used to confer high monetary value as
objects (such as silver coins and investment bars) or make objects symbolic of high
social or political rank.
Jewelry and silverware are traditionally made from sterling silver (standard
silver), an alloy of 92.5% silver with 7.5% copper. In the US, only an alloyconsisting of at least 92.5% fine silver can be marketed as "silver" (thus frequently
stamped 925). Sterling silver is harder than pure silver, and has a lower melting point
(893 C) than either pure silver or pure copper. Britannia silver is an alternative
hallmark-quality standard containing 95.8% silver, often used to make silver
tableware and wrought plate. With the addition ofgermanium, the patented modified
alloy Argentium Sterling Silver is formed, with improved properties including
resistance to firescale. Treister, Mikhail YU (Ancient Civilizations from Scythia to
Siberia, 2004).
http://en.wikipedia.org/wiki/Chemical_elementhttp://en.wikipedia.org/wiki/Chemical_symbolhttp://en.wikipedia.org/wiki/Atomic_numberhttp://en.wikipedia.org/wiki/Transition_metalhttp://en.wikipedia.org/wiki/Electrical_conductivityhttp://en.wikipedia.org/wiki/Thermal_conductivityhttp://en.wikipedia.org/wiki/Alloyhttp://en.wikipedia.org/wiki/Goldhttp://en.wikipedia.org/wiki/Argentitehttp://en.wikipedia.org/wiki/Chlorargyritehttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Goldhttp://en.wikipedia.org/wiki/Leadhttp://en.wikipedia.org/wiki/Zinchttp://en.wikipedia.org/wiki/Refininghttp://en.wikipedia.org/wiki/Precious_metalhttp://en.wikipedia.org/wiki/Coinshttp://en.wikipedia.org/wiki/Sterling_silverhttp://en.wikipedia.org/wiki/Britannia_silverhttp://en.wikipedia.org/wiki/Hallmarkhttp://en.wikipedia.org/wiki/Germaniumhttp://en.wikipedia.org/wiki/Argentium_sterling_silverhttp://en.wikipedia.org/wiki/Firescalehttp://en.wikipedia.org/wiki/Firescalehttp://en.wikipedia.org/wiki/Argentium_sterling_silverhttp://en.wikipedia.org/wiki/Germaniumhttp://en.wikipedia.org/wiki/Hallmarkhttp://en.wikipedia.org/wiki/Britannia_silverhttp://en.wikipedia.org/wiki/Sterling_silverhttp://en.wikipedia.org/wiki/Coinshttp://en.wikipedia.org/wiki/Precious_metalhttp://en.wikipedia.org/wiki/Refininghttp://en.wikipedia.org/wiki/Zinchttp://en.wikipedia.org/wiki/Leadhttp://en.wikipedia.org/wiki/Goldhttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Chlorargyritehttp://en.wikipedia.org/wiki/Argentitehttp://en.wikipedia.org/wiki/Goldhttp://en.wikipedia.org/wiki/Alloyhttp://en.wikipedia.org/wiki/Thermal_conductivityhttp://en.wikipedia.org/wiki/Electrical_conductivityhttp://en.wikipedia.org/wiki/Transition_metalhttp://en.wikipedia.org/wiki/Atomic_numberhttp://en.wikipedia.org/wiki/Chemical_symbolhttp://en.wikipedia.org/wiki/Chemical_element -
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Silver, in the form of electrum (a gold-silver alloy), was coined to produce
money in around 700 BC by the Lydians. Later, silver was refined and coined in its
pure form. Many nations used silver as the basic unit of monetary value. In the
modern world, silver bullion has the ISO currency code XAG. The name of the
United Kingdom monetary unit "pound" () reflects the fact that it originally
represented the value of one troy pound of sterling silver. In the 1800s, many nations,
such as the United States and Great Britain, switched from silver to a gold standard
of monetary value, then in the 20th century to fiat currency (Jason, 2009).
Silver can be alloyed with mercury, tin and other metals at room temperature
to make amalgams that are widely used for dental fillings. To make dental amalgam,a mixture of powdered silver and other metals is mixed with mercury to make a stiff
paste that can be adapted to the shape of a cavity. The dental amalgam achieves
initial hardness within minutes but sets hard in a few hours.
In photography industries, 30.98% of the silver consumed in 1998 in the form
of silver nitrate and silver halides. In 2001, 23.47% was used for photography, while
20.03% was used in jewelry, 38.51% for industrial uses, and only 3.5% for coins andmedals. The use of silver in photography has rapidly declined, due to the lower
demand for consumer color film from the advent of digital technology, since in 2007
of the 894.5 million ounces of silver in supply, just 128.3 million ounces (14.3%)
were consumed by the photographic sector, and the total amount of silver consumed
in 2007 by the photographic sector compared to 1998 is just 50% (Isaac, 1966).
http://en.wikipedia.org/wiki/Electrumhttp://en.wikipedia.org/wiki/Lydiahttp://en.wikipedia.org/wiki/Bullionhttp://en.wikipedia.org/wiki/ISO_4217http://en.wikipedia.org/wiki/Pound_sterlinghttp://en.wikipedia.org/wiki/Troy_poundhttp://en.wikipedia.org/wiki/United_Stateshttp://en.wikipedia.org/wiki/Great_Britainhttp://en.wikipedia.org/wiki/Gold_standardhttp://en.wikipedia.org/wiki/Fiat_currencyhttp://en.wikipedia.org/wiki/Amalgam_%28chemistry%29http://en.wikipedia.org/wiki/Dental_amalgamhttp://en.wikipedia.org/wiki/Halogenhttp://en.wikipedia.org/wiki/Isaac_Asimovhttp://en.wikipedia.org/wiki/Isaac_Asimovhttp://en.wikipedia.org/wiki/Halogenhttp://en.wikipedia.org/wiki/Dental_amalgamhttp://en.wikipedia.org/wiki/Amalgam_%28chemistry%29http://en.wikipedia.org/wiki/Fiat_currencyhttp://en.wikipedia.org/wiki/Gold_standardhttp://en.wikipedia.org/wiki/Great_Britainhttp://en.wikipedia.org/wiki/United_Stateshttp://en.wikipedia.org/wiki/Troy_poundhttp://en.wikipedia.org/wiki/Pound_sterlinghttp://en.wikipedia.org/wiki/ISO_4217http://en.wikipedia.org/wiki/Bullionhttp://en.wikipedia.org/wiki/Lydiahttp://en.wikipedia.org/wiki/Electrum -
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2.3 Silver in Photographic Waste
2.3.1 Introduction to photographic waste
Photographic processing in industry produces a variety of chemical wastes.
The main chemicals of concern are silver, ammonia and sulphur compounds. Silver
compounds accumulate in the solid byproducts (biosolids) from wastewater
treatment plants and may limit the potential for recycling this valuable nutrient
resource. They can also have a toxic effect on the environment. The
environmentalist is therefore concerned to minimize silver discharge to its sewers.
Since silver is a precious metal, it is also in the interest of photo lab operators tominimize their wastes, and therefore reduce their chemical costs. Ammonia and
sulphur compounds can, under certain conditions, produce toxic gases or corrosive
substances in the sewer that might be a danger to human or accelerate damage to the
sewer fabric (Water Cooperation, 2003)
Table 2.1: Chemical properties in photographic waste (Othman et. al., 2005).
Cations Concentration
(ppm)
Anions Concentration
(ppm)
Physical
properties
Ag 2490.522 Cl 249 pH
8.02
Na 3628.63 NO3 2202 Density
1.04 g/ml
K 6238.059 SO42
3712 Viscosity0.77cP
Fe 1478.909 F 62
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Table 2.2: Physical properties in photographic waste (Othman et. al., 2005).
pH 8.02
Density (g/ml) 1.04
Viscosity (cP) 0.77
2.3.2 Photographic waste management
The photographic waste management need to be done before discharge into
environment. The amount of chemical waste in the photochemical waste need toreduce lower from the limit of that contamination regilated by environmental
organization.
In photographic waste, the silver is present mainly as soluble silver-
thiosulphate complex with a small amount of silver sulfide. The silver concentration
can range between 5mg/l and 12,000mg/l depends on the stage from which the
wastes originate and the type of film being generated (Cornell University, 2003). It
has been reported by Farmer et al. (1996) that 25% of the world's silver needs are
supplied by recycling and that 75% of this is obtained from photographic waste1.
For this reason, the methods applied to recover silver from photographic waste are
important in reducing cost and time, and have a positive effect on environmental
pollution.
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2.4 Process of Silver Recovery
2.4.1 Introduction
Silver, one of the precious and noble metals, is used in large quantities for
many purposes, particularly in the photographic industry. Silver recovery methods
implemented are electrolysis, metallic replacement, chemical precipitation, ion
exchange, reverse osmosis and evaporation (Nakiboglu et al., 2001).
2.4.2 Electrolysis recovery method.
When electric current is passed between two electrodes immersed in the
silver-bearing fixer, the silver is electronically deposited upon the cathode. This
silver can be stripped from the cathode and refined. This method permits re-use of
the fixer. A recirculating electrolytic recovery system has advantages over systems
that only remove silver. Silver is removed from fixer solution by the recovery cellwhich is connected "in-line" as part of a recirculation system. Fixer solution
reclaimed by electrolytic silver recovery can have limited reuse in the photo process.
By recirculating the delivered fixer to the in-use process tank, less fresh fixer
solution is needed to replenish the bath. Fixer replenishment can be reduced 20
percent or more without degradation of product quality. Chemical replenishment can
be managed through the frequent and consistent use of test strips. A properly
designed recirculating system can lower the silver in the fixer from a concentrationof 1 ounce/gal. to 1 ounce/100 gals. The amount of silver carried over to the rinse
water is similarly reduced (The North Carolina Division of Pollution Prevention and
Environmental Assistance, 1982).
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Figure 2.1: Electrolysis cell for electrolysis of silver recovery (The NorthCarolina Division of Pollution Prevention and Environmental Assistance,
1982)
2.4.3 Metallic replacement.
This method consists of replacing the metallic silver with a less valuable base
metal such as iron, zinc, or copper. As an example, if steel wool is inserted into the
exhausted fixer solution, the silver in solution is replaced by the iron, and the silveraccumulates on the bottom of the container in the form of sludge. The sludge are
removed and refined to reclaim the silver. The fixer must be discarded after silver
recovery by this method. Metallic replacement requires little capital expenditure for
equipment and requires only a few simple plumbing connections. The equipment
consists of a plastic container, plastic-lined steel or stainless steel drum filled with
metal, usually steel wool, and some plastic hose and plumbing connections. Silver is
recovered when the silver-bearing solution flows through the cartridge and makes
contact with the steel wool. The iron goes into solution as an ion, and the metallic
silver is released as a solid to collect in sludge at the bottom of the cartridge or is
deposited on the steel wool. The yield a user can expect is determined by the silver
concentrations in solution, the volume of solution that is run through the cartridge,
and the care with which the operation is managed. When silver is no longer
effectively removed, the silver-bearing sludge is sent to a refiner who will refine it
and pay the customer for the recovered silver (The North Carolina Division of
Pollution Prevention and Environmental Assistance, 1982).
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Figure 2.2 : Metallic replacement of silver recovery (Eastman Kodak Company,
1982)
2.4.4 Chemical precipitation.
Another option is chemical precipitation with sodium sulfide, sodium
borohydride or sodium dithionite. Silver can be reclaimed from fixer by the addition
of certain chemicals to the exhausted fixer. The silver is precipitated out of thesolution in the form of a sludge that can be recovered and refined. The chemical
reaction generates obnoxious fumes and odors, and separate facilities are
recommended for this method of silver recovery. The fixer must be discarded. This
can remove virtually 100 percent of the silver and most other metals from
photographic effluent. With the addition of alkaline sodium sulfide and the resulting
precipitation of silver sulfide, levels of soluble silver below 0.1 mg/l are possible.
However, the more difficult part of the process is the separation of the precipitatefrom the liquid. Total silver levels of 0.5 to 1.0 mg/l are usually obtained due to
filtration limitations. This process requires only a small capital expenditure and uses
chemicals which are relatively inexpensive. It is not as widely used as the
electrolytic or metallic replacement methods because of the inconvenience of
handling large amounts of chemicals, the separation process required, and the
problem of concentrating finely precipitated silver sulfide particles into a sludge that
can be dried and refined. Also, careful pH control is required to avoid generation of
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highly toxic hydrogen sulfide gas (The North Carolina Division of Pollution
Prevention and Environmental Assistance, 1982).
2.4.5 Ion exchange
Ion exchange is generally used for effective recovery of silver from rinse
water or other dilute solutions of silver. The ion exchange method involves the
exchange of ions in the solution with ions of a similar charge on the resin. The
soluble silver thiosulfate complex is exchanged with the anion on the resin. This is
the exhaustion step and is accomplished by running the solution through a column
containing the resin. For large operations, the next step is the regeneration step in
which the silver is removed from the resin column with a silver complexing agent
such as ammonium thiosulfate. This step includes several backwashes to remove
particulate matter and excess regenerant before the next exhaustion step is initiated.
Silver is then recovered from the thiosulfate regenerant with an electrolytic recovery
cell. For smaller operations an alternative to performing the regeneration step on-site
would be to remove the resin from the column and send it to a refiner for silver
reclamation. Important factors in considering an ion exchange system for silver
recovery are: selection of the resin, flow rate of the silver-bearing solution, column
configuration and selection of the regenerant. It has been demonstrated that the use
of ion exchange can reduce the silver concentration in photographic effluent to levels
in the range of 0.5 to 2 mg/l and can recover over 98 percent of the available silver.
If this method is used as a tailing method after primary recovery by electrolysis,
levels in the range of 0.1 to 1 mg/l can be obtained (The North Carolina Division ofPollution Prevention and Environmental Assistance, 1982).
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Figure 2.3: Ion exchange of silver recovery (The North Carolina Division of
Pollution Prevention and Environmental Assistance, 1982).
2.4.6 Reverse osmosis
Reverse osmosis (RO) is also used for dilute solutions. RO uses high
pressure to force the silver-bearing solution through a semipermeable membrane to
separate larger molecules, such as salts and organics1 from smaller molecules like
water. The extent of separation is determined by membrane surface chemistry and
pore size, fluid pressure and wastewater characteristics. For removal of silver, after-
fix rinse water is flow-equalized, filtered and pumped through an RO unit. Once the
silver is separated from the water in this manner it can be recovered by conventional
means such as metallic replacement, electrolytic recovery or chemical precipitation.
Operating problems include fouling of the membrane and biological growth (The
North Carolina Division of Pollution Prevention and Environmental Assistance,
1982).
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2.4.7 Evaporation
Evaporation is another option for managing waste photographic solutions.
The wastewaters are collected and heated to evaporate all liquids. The resultingsludge is collected in filter bags. These bags can be sent to a silver reclaimer for
recovery. The major advantage of the evaporation technique is it achieves "zero"
water discharge. This method would be useful to operations that do not have access
to sewer connections or wastewater discharge. A disadvantage is that the organics
and ammonia in the waste solution may also be evaporated, creating an air pollution
problem. A charcoal air filter may be necessary to capture the organics. Filter
purchase, disposal and electrical power add to operating costs (The North CarolinaDivision of Pollution Prevention and Environmental Assistance, 1982).
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Table 2.3: Comparison of silver recovery methods (State Department of
Health/Solid and Hazardous Waste Branch, 2005)
METHOD ADVANTAGES DISADVANTAGES
Metallic
Replacement
Low investmentLow operating costs;Simplest operation
High iron content ofeffluentSilver recovered as sludgeHigh silver concentrationin effluent unless two unitsare in servies
Ion Exchange Can attain 0.1-2.00 mgAg+/LGood for very low Aglimits.
Only for low silverconcentration influentComplex operation
High investment.ElectrolyticRecovery
Recovers silver as puremetalHigh silver recovery.
Potential for sulfideformationHigh silver concentrationin effluent.
Precipitation Can attain 0.1 mg.AG+/L;Low investment
Complex operationSilver recovered as sludgeTreated solution cannot bereused
Potential H2S release.
ReverseOsmosis
Also recovers otherchemicalsPurified water is recycled.
Concentration requiresfurther processingHigh investmentHigh operating cost.
Evaporation Minimum aqueouseffluentWater conservation.
High energy requirementSilver recovered as sludgeOrganic contaminant
buildupPotential air emissions.
Adsorption simple operationeasy to separate liquid andsolid phase
adsorbent not selective tosilver metal ion
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2.5 Adsorption Process in Silver Recovery
2.5.1 Introduction
Adsorption process is an attraction between dissimilar molecule species (as of
gases, solutes, or liquids) and the surfaces of solid bodies with which they make a
direct contact. This process creates a film of the adsorbate (the molecules or atoms
being accumulated) on the surface of the adsorbent. It involves the separation of a
substance from the one phase accompanied by its accumulation or concentration at
the surface of another (Weber 1985). In practical operation, maximum capacity of
adsorbent cannot fully utilize due to the existing of mass transfer effect. It is essentialto have information on adsorption equilibrium and kinetics of the adsorption process
which basically controlled by adsorption parameters in order to estimate the
adsorption capacity practically or dynamic adsorption (Slejko, 1985). The
adsorption performance depends on several parameters related to the adsorbent,
adsorbate and the system parameters.
Figure 2.4: Mechanism of adsorption and desorption process
The physical and chemical characteristics of the adsorbents plays important
role during the adsorption process. The physical properties including surface area,
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pore and particle size distribution directly affect the adsorption performance. Bajpai
and Rohit (2007) stated that smaller particle sizes will have higher surface area for
contact with adsorbates. Moreover, pore size and pore volume play also a big role
during the adsorption process. Adsorbents which have higher pore volume also can
give adsorb high capacity of metal.
For the adsorbate, the parameters that may affect the adsorption performance
include concentration, pH, molecular structure, molecular polarity, and competitive
of the adsorbate in adsorption process. In term molecular structure, some adsorbent
will be selective to some particular chemical structure (Crini and Badot, 2008;
Slejko, 1985). In the case of adsorbate in liquid phase, the pH and concentration ofthe adsorbate solution play an important role in determining adsorption capacity.
Condition of adsorption process such as temperature and pressure would
determine the adsorption performance especially in adsorption rate. At high
temperature, the adsorption of adsorbate increases because high temperature provides
a faster rate of diffusion of adsorbate molecules from the solution to the adsorbents
(Crini and Badot, 2008). Adsorption reactions are normally exothermic.
2.5.3 Adsorption equilibrium
When an adsorbent is in contact with the surrounding fluids of a certain
composition, adsorption takes places and after a sufficient long time, the adsorbentand the surrounding reach equilibrium (Suzuki, 1990). The capacity of adsorbate that
can be adsorbed depends on the concentration or partial pressure in the bulk fluid
phase and temperature The equilibrium adsorption data can be expressed in the form
of isotherms (amount of adsorbed at constant temperature as the function pressure or
concentration), isosteres (relates the equilibrium pressure of the fluids adsorbate to
the temperature of the system for the constant amount of the adsorbed phase) or
isobars (functional relationship between the amount of adsorbed and the temperatureat the constant pressure and concentration) (Tompkins, 1978). The concentration in
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solid phase is expressed as q, kg adsorbate (solute)/kg adsorbent (solid), and in the
fluid phase (gas or liquid) as c, kg adsorbate/m3 fluid. The relations are illustrated at
Figure 2.9.
a b
Figure 2.5: Effect of temperature, pressure and concentration towards adsorption
capacity (a) amount of adsorbed with concentration and temperature depending
(adsorption isosteres) (b) amount of adsorbed versus concentration or pressure
(adsorption isotherm) (Suzuki, 1990).
2.5.4 Adsorption kinetic
Adsorption kinetic models present relationship between the solute uptake rate
and time (important in treatment process design). Kinetics study is one of the
important characteristics for metal adsorption behavior. It determines the rate of
adsorption which is a mass transfer of adsorbate from fluid to solid which is
influenced by several factors. Mass transfer as third fundamental transfer occurs in
the adsorption process. The factors are really related to diffusion since it was one of
the mechanisms of adsorption process which include diffusion to the external
surface, deposition on the surface, diffusion in the pores, and diffusion along the
surface (Dabrowski, 2001). From the kinetics study, the time dependence of such
system and the required contact time for sorption process to be completed can be
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determined (Augustine et al., 2007). This data is the most importance, especially
when designing batch sorption systems (Augustine et al., 2007).
2.6 Adsorbent for Silver Recovery
2.6.1 Type of adsorbent
Adsorbents are used usually in the form of spherical pellets, rods, moldings,
or monoliths with hydrodynamic diameters between 0.5 and 10 mm. They must havehigh abrasion resistance, high thermal stability and small pore diameters, which
results in higher exposed surface area and hence high surface capacity for effective
adsorption. The adsorbents must also have a distinct pore structure which enables
fast transport of the gaseous vapors. There are four classes of adsorbents that are
being used in industry such as oxygen containing compound, carbon based
compound, and polymer based compound and biomaterial compound.
Biomaterial compound adsorbent is a recent study of adsorbent on heavy
metal as an economical method of heavy metal recovery. In Nigeria, Okieimen et al.
(1991) and Horsfall and Spiff (2004) have used groundnut husk, fluted pumpkin and
wild cocoyam respectively for removal of heavy metals from aqueous solutions. The
term, biosorption is used to in the adsorption process. Agricultural materials have
also been used. These include rice bran, soybean and cottonseed hulls (Marshall and
Johns, 1996), crop milling waste (Saeedet al.,
2005), groundnut husk (Okieimenet
al., 1985).
Carbon-based compounds are typically hydrophobic and non-polar, including
materials such as activated carbon and graphite. Commercial activated carbon
adsorbent extensively used for waste water treatment due to its elevated surface area
such as removal of organic compound from industry waste water (Mendez et al.,
2007). This adsorbent is an environment friendly adsorbent.
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Oxygen-containing compounds are typically hydrophilic and polar, including
materials such as silica gel and zeolites. Zeolite are used for drying, separation of
hydrocarbons, mixture and many other applications.
Polymer-based compounds are polar or non-polar functional groups in a
porous polymer matrix. The study by Budd et al., (2003) stated that this adsorbent
has considerable aesthetic appeal of crystalline nanoporous materials, together with
the opportunities for size and shape selectivity
2.6.2 Functionalization of adsorbent
In order to increase the adsorption efficiency of those materials for silver
recovery, functionalization procedure was proposed. The functionalization of active
group in the adsorbent matrices was carried out through the by molecular imprinting,
covalent grafting synthesis and impregnation process.
The synthesis of adsorbents through impregnation method is relatively a very
simple process. It involves the physical interaction between the solid supports and
the chelate ligands. There are two methods of impregnation which are dry or wet
impregnation method. The wet impregnation is also known as extractant
impregnated resins (EIRs). For EIRs method, matrices are soaked in the solution
containing selected ligands. After standing for some times in order to allow
achieving equilibrium, supernatant then are removed. In the case of dryimpregnation method, the active groups in solid or powder form such as elemental
sulfur compounds are directly adsorbed into the polymeric support. A typical
procedure for this technique involves the mixing of support materials (e.g. carbon)
with elemental sulfur, heated at high temperature for several hours under nitrogen
environment and finally cooled at room temperature (Wakui et. al., 2007)
The covalent grafting is basically a method used to functionalize polymericmaterials with ligands through the formation of covalent bonding in which electrons
http://en.wikipedia.org/wiki/Silica_gelhttp://en.wikipedia.org/wiki/Zeoliteshttp://en.wikipedia.org/wiki/Zeoliteshttp://en.wikipedia.org/wiki/Silica_gel -
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are shared rather than transferred. Basically, there are two methods which include
post functionalization and in-situ synthesis. Post functionalized synthesis also
known as two step synthesis where the first step involves preparing the polymer
matrices, and then followed by immobilization of ligands. In-situ synthesis involved
incorporation of organofunctional groups during the matrix support preparation.
Molecular imprinting is a concept of preparing substrateselective
recognition sites in a matrix using a molecular template. In molecular imprinting,
functional monomers are associated with a template (atom, ion, molecule, complex
or molecular, ionic or macromolecular assembly, including micro-organism). It
involves arranging monomers of polymerization synthesis around the template
molecule so that complexes between the monomer and template molecules.
2.6.3 Extractant Impregnated Resin (EIR) for silver recovery
2.6.3.1 Basic principles
Extractant Impregnated Resin (EIR) is an extraction agents used in the metal
recovery from aqueous solution such as extraction of copper, zinc, uranium and
nickel, or any of these, from aqueous solutions containing same macroporous
polymer supporting a specific extractant for such metals. The polymer being
rendered by the method of physical impregnation which is the attachment with
suitable functional groups, or attaching such functional groups to the polymer an
agent. The concept of EIRs is based on the incorporation of a selective extractive
reagent into a porous particle by these physical impregnation (Babic et al., 2006).
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2.6.3.2 Extractant Impreganted Resin(EIR) mechanisms
The concept of SIRs is based on the incorporation of a selective extractive
reagent into a porous particle by physical impregnation. In order to apply thistechnology for the removal of components from water, it is necessary to fill the pores
with a water-insoluble organic phase. However, silver does not show strong
tendency to transfer from an aqueous to an organic phase. To improve their affinity
for organic phase, it is functionalized with a complexing agent capable of forming a
complex with metal, which remains in the organic phase. This reaction should be
reversible but sufficiently strong to increase the metals affinity for organic phase by
several orders of magnitude to obtain an economically feasible process. Ascomplexing agents, primary amines can be used because they form stable Schiff
bases in reaction with metal. (Burghoffet al., 2008).
Figure 2.6: EIR principle of a macroporous particle impregnated with a
complexing agent E (Burghoffet al., 2009)
2.6.3.3 Advantages of extractant impregnated resin (EIR)
Extractant Impregnated Resin is a combination of adsorption and reactive
extraction. Techniques such as reactive extraction and adsorption have been
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investigated and used for this type of separations, but also suffer from significant
drawbacks. Reactive extraction usually has problems with phase separation due to
the emulsion formation. To increase the contact area it is necessary to vigorously
mix the phases which leads to the loss of reagent (Jerabek et al., 1996)
In addition, reactive extraction is not very feasible for the recovery of species
present in low concentration due to the high excess of solvent/reactant required and
not very suitable for recovering species from viscous solutions. Concerning
adsorption, nonfunctionalized resins tend to have low capacity and low selectivity.
Better performing chelating, ion exchange or enantiomer selective resins are very
expensive due to their difficult and time consuming preparation. Therefore, the needexists for the development of a new technique able to fulfill the targeted
requirements. The suitable technique should avoid the mentioned disadvantages of
the conventional techniques but maintain their advantages. For instance, adsorption
is rather suitable for processing dilute solutions, the used equipment is relatively
simple and easy to operate and there is no problem of liquid/solid phase separation.
On the other hand, reactive extraction has high capacity and high selectivity toward
the target compounds and usually offers high mass transfer rates. Additionally, a
reagent in a free solution is much cheaper than chemical ly functionalized
adsorbents (Babic et al., 2008).
2.6.4.4 Current applications of extractant impregnated resin (EIR)
Beside recovery of precious metal, extractant impregnated resin (EIR) also
has several current applications in many field. EIR was being used in
chromatographic separation of toxic elements. Extraction chromatography with
macroeticular polymer bead impregnated with mono-thiodibenzoylmethane solution
was investigated by Sugii et al. (1982) for separation of Ni(II), Fe(III) and Co(II).
The extraction behavior of these metals with SIR was similar to the findings with the
solvent alone by conventional liquid-liquid extraction (Kawahara et al., 2000). It
was reported that a macro-porous resin impregnated with a newly synthesized
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hydrophobic extractant, bis(2-ethylhexyl)ammonium bis(2-ethylhexyl)
dithiocarbamate, (BBDC) has been found to extract As(III) from solution. As(III)
retained on a column was quantitatively eluted with an alkaline solution (Wakui et
al., 1998).
EIR is also useful in extraction of rare and valuable metals. The investigation
of extraction of gold from solutions containing zinc and copper has been attempts to
develop polymeric adsorbents that can be applied to the recovery of precious metals
from aqueous solution. Two methods were used in selecting polymeric adsorbents
which either commercially available ion-exchange resins or hybrid absorber prepared
by impregnation and physically immobilization of selective and specific reagentsconventionally used in solvent extraction onto high specific surface polymeric
materials (Kabay et al., 2010).
In radioanalytical separations, EIR is as adsorbent. An adsorption method for
determination of the distribution of Np amongst its oxidation states by the use of
EIRs and bismuth phosphate as adsorbents was also reported (Kirishima et al., 2003).
The loading and elution behavior of uranium from nitric acid using atricyclohexylphosphate impregnated Amberlite XAD-7 resin was reported elsewhere
(Brahmmananda Rao et al., 2003). The extraction of TcO-4, UO2+
2, and iodine
species onto XAD-7 resin impregnated with trihexyltetradecylphosphonium chloride
was investigated. It was found that pertechnetate and iodine species can be separated
from hexavalent actinides in aqueous media at moderately low acidities and that
pertechnetate and iodine can be stripped at very low or very high nitric acid
concentrations (Cocaliaet al
., 2007)
Besides, EIR also being applied in purification of wet process phosphoric
acid. Solvent-impregnated resins were also developed for the recovery of uranium
from wet process phosphoric acid (Belfer et al., 1984). Extraction of Cd(II) and
Cu(II) from phosphoric acid solutions by SIRs containing Cyanex 302 was reported
by Kabay et al., (1998). Elsewhere, Cyanex 302 was impregnated into macro-porous
Diaion HP-10 and HP-1 MG polymeric resin matrices and used as an extractant torecover Cd(II) from concentrated phosphoric acid
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2.7 Summary
The photographic waste which come from photographic industry contains
many hazardous contaminations included silver metal. So, there are several popularmethods for silver recovery which are electrolysis, metallic replacement, chemical
precipitation, ion exchange, reverse osmosis and evaporation. All the methods have
their advantages and disadvantages. However, one new method was implemented to
recover silver in effective way. Extraction of silver from photographic waste using
extractant impregnated resin is based on the incorporation of a selective extractive
reagent into a porous particle by physical impregnation. There are several
advantages of EIRs compared to the other methods. Because of its advantages, thereare several new applications of it nowadays.
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CHAPTER 3
METHODOLOGY
3.1 Introduction
This chapter presents all chemicals and procedures used in this study. The
research was conducted using chemicals obtained from various suppliers. The
synthesis, characterization and functionalization procedures were adopted as reported
in the literature. This chapter comprises mainly i) chemicals; ii) EIR synthesis
procedures; iii) EIR characterization procedures, iv) silver adsorption and desorption
procedures; and v) analytical procedures, which were described in some details in the
following sub-sections.
3.2 Chemicals
The chemicals used were Cyanex 302 that ordered from Fluka, kerosene also
from Fluka, ethanol also was obtained from Fluka, Amberlite XAD-2 from Supelco
and XAD-7 was purchased from Merck, Germany. All reactants are manufacture
grade and used as received. Chemical properties of the reagents were shown in table
3.1, 3.2 and 3.3. All chemicals were used directly as supplied. Deionized water used
throughout this work was produced by the Purite Water System (U.K) which is
available in our laboratory.
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Table 3.1: Properties of Cyanex 302
Properties
Physical appearance Light yellow (mobile liquid)
Chemical formula C16H35OPS
Molecular weight (g/mol) 306.49
Assay (%) 85
Density (g/cm3) 0.93
Temperature (oC) 337
Table 3.2: Properties of kerosene and ethanol (Diluents)
Kerosene Ethanol
Physical Appearance Colorless Colorless
Chemical formula - C2H6O
Molecular Weight (g/mol) - 46.07
Density (g/mL) 0.80 0.789
Viscosity (cP) 0.02 1.200
Dielectric constant 2.0-2.2 24.3
Table 3.3: Properties of XAD-2 and XAD-7
Amberlite XAD-2 Amberlite XAD-7
Appearance Hard with sphericalopaque beads
White translucent beads
Porosity (mL/g) 0.65 1.14
Surface Area (m2/g) 300 450
Mean Pore Diameter () 90 100
True Wet Density (g/mL) 1.02 1.05
Skeletal Density (g/mL) 1.08 1.24
Bulk Density (g/L) 640 650
Diluents
Propertie
Resins
Properties
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3.3 Experimental Procedures
3.3.1 Preparation of Pure Resin
XAD-2 and XAD-7 were used as supplied. Before the used of XAD-2 and
XAD-7, these materials were washed first with diionized water water to remove the
salts (NaCl and Na2CO) and excess monomer present on the resins. The resin was
shaking with deionized water using incubator shaker model Innova 4080 for 1 hour
(250 rpm) at room temperature (27oC). Then, the water was removed by filtration.
The resin was rinsed again with deionized water for three to four times and lastly it
was rinsed with diluents (ethanol or kerosene). After filtration, the resins were dried
at 50oC in the oven for 24 hours. Then, resins were vacuum using roto-vapor
vacuum for 5 hours to remove excess diluents and moisture before further
experiment.
3.3.2 Impregnation Procedure
The impregnation of the resin is performed by the dry impregnation method.
Before doing the impregnation process, extractant Cyanex 302 was firstly diluted
with kerosene diluent to concentrations 0.05g Cyanex302 /ml solvent. Dilution
process was repeated for ethanol diluent.
1g of cleaned Amberlite XAD-2 and XAD-7 were put in contact with 5ml of
dilute Cyanex 302 for 48 hours under agitation using incubator shaker model Innova
4080. After that, the samples were filtered and rinsed with deionized water and its
solvent. After filtration, the solvent and moisture were removed by drying in 50oC
oven and lastly vacuumed for 5 hours. After impregnation, the EIRs were produced
as XAD2-Cyanex302 (Kerosene), XAD2-Cyanex302 (Ethanol), XAD7-Cyanex302
(Kerosene) and XAD2-Cyanex302 (Ethanol).
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3.3.3 Characterization of Extractant Impregnated Resin (EIR)
The analysis of the surface structure of extractant impregnated resin (EIR)
and pure resin was carried out using Scanning Electron Microscope (SEM) analysismodel JEPL JSM-6390LV. A small portion of sample was place in copper stab and it
was coated with platinum. The samples were examined using 5-10 kV accelerating
voltage. The SEM images were taken at 100x magnification.
The existence of functional group in the extractant impregnated resin (EIR)
was carried out by using Fourier Transform Infrared Spectrophotometer (FTIR),
Perkin Elmer Model 2000. A small portion of sample was mixed with KBr. Then,this compound was compressed using two stainless steel cylinders to form a thin
transparent solid film. The FTIR analysis was analyzed at region between 370 and
4000 cm-1.
3.3.4 Adsorption of silver by Extractant Impregnated Resin (EIRs)
Adsorption experiment was performed on silver solution at batch system.
0.025g of EIRs were mixed with 25ml silver solution. Initial pH was fixed at 7.56.
The mixture was agitated for 72 hours using a mechanical shaker at room
temperature. After that, the solution was filtered. Concentration of silver in solution
and pH of the solutions was analyzed using AAS analysis and pH meter. Adsorbent
with high adsorption capacity was used to further studies on the kinetic study andadsorption of silver in photographic waste.
For pH effect study, the adsorption experiment was done for EIR XAD2-
Cyanex302 (Kerosene), XAD7-Cyanex302 (Kerosene), pure Amberlite XAD-2 and
pure Amberlite XAD-7. Adsorption process was done as above procedure but pH
was varies at 2.80, 4.61, 7.76 and 9.35 for each samples. pH equilibrium will
measured after 3 days of adsorption process. The amount of silver extracted foreach samples got from AAS analysis.
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Kinetic adsorption was study by adsorption experiment through time. The
preparation of adsorption was following above steps. 200ml of 1000pm silver
solution was mixed with 0.2 g of EIR XAD7-Cyanex302 (kerosene) as the best
adsorbent. During the 3 days of adsorption process, samples of silver solution were
taken for silver content at adsorption time period of 1 minute, 5 minute, 10 minute, 1
hour, 6hour, 34 hour, 54 hour and lastly 73hour).
3.3.5 Analytical Procedures
3.3.5.1 pH determination
The pH of the silver solution was determined using pH meter (Mettler Toledo
Delta 320 pH meter). Calibration was carried out at 2 point calibration using pH 4.01
and pH 10.00 buffer solutions every time before pH measurement. The pH
measurement accuracy was 0.005 pH unit.
3.3.5.2 Silver concentration using Atomatic Absorption Spectrophotometer
(AAS)
Analysis of silver content is performed to characterize the photographic waste
and determine silver concentration in the aqueous solution after adsorption. Silver
metals were determined by using Atomatic Absorption Spectrophotometer (AAS)
model Perkin Elmer Precisely HGA 900. AAS is principal tool for measuring
metallic at ppm level. A liquid sample is sucked through a plastic tube into a flame,
and then the flame evaporates all liquid, breaks all molecules into atoms, and excites
many atoms into high energy states. The concentration of silver was measured by
absorption of light from atoms in flame.
Air-acetylene flame (method 3111B) was used for the silver analysis. The
instrument set-up conditions for the determination of silver are given in Table 3.6.
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The silver calibration curve was obtained by plotting absorbance versus silver
standard concentrations having concentrations between 10-50 ppm, which are within
the linear working range of the silver measurement. All data presented in this thesis
were an average of triplicate measurement results. For the low Ag(II) concentration
(e.g. ppb), the Ag(II) concentration was measured using a continuous Hydride
Generation/Atomic Absorption Spectrophotometric method.
Table 3.4: The instrument set-up conditions for determination of silver
by AAS using air-acetylene method.
Wavelength (nm) 253.7
Slit Flame (nm) 0.2
Flame Air-Acetylene
Air-acetylene flow rate (l/min) 1.50
Air-compressor flow rate (l/min) 10.00
Light sources (Ag Cathode Lamp) EDL
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3.5 Summary
The materials and procedures presented in this chapter were designed based on
objectives and scopes presented in Chapter 1. The procedures used in this research arebased on the previous researchers reported in the literature unless stated otherwise. All
the experimental data was collected, analyzed and discussed in Chapter 4.
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CHAPTER 4
RESULTS AND DISCUSSION
4. 1 Introduction
In purpose to get best model of extractant impregnated resin (EIR) for silver
recovery from photographic waste, detail observation in choosing several important
parameters in EIR synthesis and adsorption must be carried out through the research.
In finding good extractant, adsorbent and diluents, several early studies on
conventional silver extraction process. The screening process was based on their
chemical structure, chemical properties and physical properties.
Adsorption process is a process that involves adhesion between adsorbent
where in this study is EIR and solute which is silver in photographic waste. The
extractant must be unsoluble in aqueous solution. In the context of metal recovery
from photographic waste, the silver aqueous solution is brought into contact with the
adsorbent impregnated with extractant. The metal of interest is extracted by
extractant in the polymer adsorbent pore through adsorption process.
The performance of adsorption process is affected by some typical factors.
pH and type of adsorbent and diluents. Hence, these parameters were manipulated to
investigate their effects on silver extraction from photographic waste. On the other
hand, the main adsorption process condition must be considered thoroughly. Lastly,
kinetic adsorption also needs to be studied to determine required time to have
complete extraction of silver.
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4.2 Extractant Impregnated Resin (EIR) Screening
4.2.1 Extractant, resin and solvent selection
Cyanex302 was chosen as extractant on silver recovery from photographic
wastes. It is due to the potential of this acidic extraxtant to extract silver. In the order
hand, this extractant is readily dissolved in organic solvent which has low toxicity.
P=S functional group in Cyanex302 provide higher extraction towards silver than
other metals existed in the photographic waste. As stated in the Section 3.3.1.2,
Cyanex302 used is 0.05M which diluted with organic solvent. This finding is inline
with reports by Alam et al. (1997).
Resin adsorbents used in this research are Amberlite XAD-2 and Amberlite
XAD-7. Both adsorbents have different monomer component and characteristics.
XAD-2 resin is hydrophobic adsorbent (nonpolar) with styrene DVB as chemical
structure. XAD-7 resin is an adsorbent with intermediate polarity with acrylic as
chemical structure. For those characteristics, there is difference result of
performance of adsorption that had been shown in Section 4.3.
Diluents used in dilution of Cyanex302 were kerosene and ethanol. Both
diluents are organic diluents and aliphatic product that have lower specific gravity
(Ritcey and Ashbrook, 1984). On the other hand, there is big difference in dielectric
constant values in both diluents which indicate polarity of the diluents. Kerosene has
dielectric constant of 2.0-2.2 and ethanol is 24.3 respectively. In the early study,
Sekine and Hesegawa, 1977 suggested that diluents with lower dielectric constant for
highest extraction. This result was shown in section 4.3.1.
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4.2.2 Extractant Impregnated Resin (EIR)s analysis
4.2.2.1 Fourier Transform Infra-Red (FTIR) Spectrophotometer analysis
Extractant impregnated resin (EIR)s were analyzed by Fourier Transform
Infra-Red (FTIR) spectrophotometer. From the IR spectra got from FTIR analysis,
EIRs can be identified by peaks that show functional group. The functional group of
extractant that doesnt have at polymeric resin was being focused to verify the
complete impregnation of EIRs. Figure 4.3 and 4.4 shows the IR spectra of pure
resins Amberlite XAD-2 and XAD-7 and extractant impregnated resin (EIR)s.
Figure 4.1: Chemical structure of extractant Cyanex302
Figure 4.2: Chemical structure of monomer styrene DVB in Amberlite XAD-2
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Figure 4.3: Chemical structure of monomer acrylic acid in Amberlite XAD-7
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Figure 4.4: IR spectra of pure resin XAD-2 and EIR
Pure XAD-2
EIR XAD-2-Cyanex302 (Kerosene)
EIR XAD-2-Cyanex302 (Ethanol)
2952.38
2924.36
2953.25
1602.79
1633.56
1600.00
1148.39
C-H bondC=C bond P=O bond
4000
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Figure 4.5: IR spectra of pure resin XAD-7 and EIRs
2924.36
1639.16
1148.07
2952.38
2953.75
1600.00
1600.00C-H bond
C=C bond
P=O bond
Pure XAD-
EIR XAD-7-Cyanex302 (Kerosene)
EIR XAD-7-Cyanex302 (Ethanol)
4000
cm-1
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Adsorbent Amberlite XAD-2 is polymeric adsorbent which is hydrophobic
crosslinked polystyrene copolymer resin. Its monomer is styrene DVB which its
chemical structure was shown in the figure 4.2. Adsorbent Amberlite XAD-7 has
monomers of acrylic acid. IR spectra of impregnated resin for both adsorbent have
additional peak compared to unimpregnated resin (pure resin). However, only EIRs
with its extractant Cyanex 302 diluted with kerosene showed the additional peak.
This additional peak of IR spectrum of impregnated resin can ensure the existing of
Cyanex302 in the pore of the adsorbents.
However, only EIRs with its extractant Cyanex 302 diluted with kerosene
showed the additional peak. IR spectra of pure amberlite XAD-2 and both EIRsshowed strong adsorption band at 2924.36 cm-1, 2952.38 cm-1, 2953.25 cm-1
respectively due to C-H group in Cyanex302 and styrene DVB. XAD-7 and both
EIRs showed strong adsorption band at 2924.36 cm -1, 2953.75 cm-1, 2952.38 cm-1
respectively due to C-H group in Cyanex302 and acrylic acid It cannot determined
that Cyanex302 present in the EIRs. The most obvious peak that showed the existing
of Cyanex302 in EIRs is at 1148.39 cm-1 which was found at EIR XAD2-Cyanex302
(kerosene) and 1148.07cm-1 at EIR XAD7-Cyanex302 (kerosene). This strong
adsorption band indicated the functional group of P=O in Cyanex302. The peak for
S-H group in Cyanex 302 cannot be seen in IR spectra of EIR because the adsorption
band is too weak. This information confirmed the success of impregnation
Amberlite XAD-2 and XAD-7 with Cyanex 302 by solvent kerosene.
4.2.2.2 Surface structure analysis using Scanning Electron Microscope (SEM)
In the preliminary screening of EIRs based on both type of solvent ethanol
and kerosene for resins amberlite XAD-2 and XAD-7 using FTIR analysis, the EIRs
that showed success impregnation of resin with extractant in FTIR analysis had been
carried out with Scanning Electron Microscope (SEM) analysis to analyze the
morphology of the surface structure of unimpregnated resin Amberlite XAD-2 andXAD-7 and its EIRs The SEM images are shown in Figure 4.5 and 4.6.
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(a)
(b)
Figure 4.6: Scanning electron microscope pictures of (a) Pure Amberlite
XAD-2 and (b) EIR XAD2-Cyanex302 (kerosene) (magnification 100x).
From the figure 4.5 (a) and (b), there is no difference in the surface structureof EIR from its original Amberlite XAD-2. XAD-2 has smaller pore size compared
to XAD-7 as stated in table 3.3. Thus, the surface of impregnated resin XAD-2
cannot see clearly through this analysis.
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(a)
(b)
Figure 4.7: Scanning electron microscope pictures of (a) Pure Amberlite XAD-7 and
(b) EIR XAD7-Cyanex302 (kerosene) (magnification 100x)
Figure 4.6(b) show that the surface of EIR has a distinct skin'. This structure
explained that Cyanex302 extractant was impregnated in the pore of Amberlite
XAD-7. Thus, the result analysis confirmed the result of FTIR analysis in the
selection of EIR.
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4.3 Adsorption Process Using Extractant Impregnated Resin (EIR)
4.3.1 Effect of type of EIRs
After adsorption process, content of silver metals in silver solution were
determined by using Atomatic Absorption Spectrophotometer (AAS). From the
result, the amount of silver extracted was calculated for each EIRs and had been
performed in the Figure 4.7.
The quantity of Ag(I) adsorbed onto the EIR phase (Qe, mg/g) was calculatedusing Eq. 4.1.
Q= [(Co-Ce) x V]/m (4.1)
where Co is the initial concentration of the Ag(I) solution (mg/l), C e is the final
concentration of the Ag(I) solution, V the Ag(I) solution volume (l) and m is the
mass of EIRs used (g). Molecular weight of silver is 107.8682.
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Figure 4.8: Silver adsorption process from silver solution by different type of EIRs
(Experimental conditions: Cyanex302=0.05M, agitation speed=250rpm, T=27oC,
pH=7.82)
EIR XAD2-Cyanex302 (kerosene) and XAD7-Cyanex302 (kerosene) show
the best result of adsorption with the adsorption capacity of 0.93mmol/g and
0.94mmol/g respectively. However, EIR XAD2-Cyanex302 (ethanol) and XAD7-
Cyanex302 (ethanol) show the adverse result where they only adsorb 0.5mmol/g and
0.45mmol/g respectively. It confirmed the result of FTIR analysis where both of the
EIR XAD2-Cyanex302 (kerosene) and XAD7-Cyanex302 (kerosene) show the peak
of extractant functional group.
From the result, it shows that EIR with ethanol diluents cannot perform well
because the impregnation of EIR was not completely done. It is because of the high
dielectric constant value of ethanol which is 24.3 compared to kerosene that has very
low dielectric constant of 2.0-2.2. The study by Sekine and Hesegawa, 1977 stated
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that lower dielectric constant, the better adsorption performance. Dielectric constant
indicates the polarity of the diluents. Interaction of the diluents with extractant can
result in lower extraction coefficient for metal ions. Therefore, extraction metals
increase with an increase in the polarity of the diluents.
EIR with polymer resin XAD-7 show a better performance than XAD-2
although just a little bit. This would be the effect from surface area of both
adsorbents. XAD-7 has a larger surface area than XAD-2 with 450m 2/g and 300m2/g,
respectively. The better performance of EIR XAD-7 is also due to its polarity.
Amberlite XAD-2 is hydrophobic adsorbent while Amberlite XAD-7 is adsorbent
with intermediate polarity which can function well in aqueous solution.
4.3.2 Effect of pH of silver solution
Figure 4.9 shows the adsorption performance of EIR and pure resin at various
pH systems. The adsorption of Ag(I) by EIRs were higher compared to pureadsorbent resins at varies pH of silver solution.
However, the pattern of the adsorption of silver does not show same pattern
with general effect of pH on metal extraction (Ritcey and Ashbook, 1984) as
illustrated by Figure 4.10. At low pH values, it is expected that the adsorption
performance will be low due to protonation of metal and at high pH, the adsorption
also decreases as a result of hydrolysis of the metal. However, in this study, theresult shows adsorption do not primarily dependent on pH for metal-extractant
complex formation, but rather on factors like anion concentration in the in the
aqueous solution.
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Figure 4.9: Effect of initial pH in silver adsorption (Experimental condition: EIR
XAD7-Cyanex302 (Kerosene)= 0.0255g, volume silver solution=25ml, agitation
speed=250rpm, T=27oC)
Figure 4.10: General effect of pH on metal extraction (Ritcey and Ashbrook. 1984)
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4.5 Kinetics Adsorption of Silver Adsorption by Extractant Impregnated
Resin (EIR)
Kinetic adsorption show the required time to have a complete adsorption
process. The amount of Ag(I) adsorbed onto synthesized adsorbents at difference
time intervals was illustrated in Figure 4.11. The kinetic was examined up to 3 days
agitation time. It clearly shows that, the amount of Ag(I) adsorbed, Qe increases with
time to a constant maximum adsorption values. The maximum adsorption capacities
of Ag(I) is 1.7 mmol/g. The minimum time required for achieving these maximum
capacities was 34 hours. After that, the increase of contact time between adsorbents
and solution were not having any adsorption activities. It means that, the adsorbentswere saturated and cannot adsorb any metal ions left in the solution.
Kinetic adsorption results also provide the information about the adsorption
rates. The rate increased rapidly in the first 360 minute, after that the adsorption rate
started gradually to become slower as increasing contact time until it achieving the
maximum adsorption capacity. The initial faster rate may be due to the availability
of the adsorbents surfaces to adsorbed Ag(I). According to Smith (1970), theadsorption kinetics depends on the surface area of the adsorbents. As the time
increases, the available surface for Ag(I) ions adsorption become limited, hence the
rates of absorbability become slower.
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Figure 4.11: Kinetic adsorption of silver extraction by EIR XAD7-Cyanex302
(Kerosene) for 72 hours (Experimental condition: EIR XAD7-Cyanex302(Kerosene)
= 0.200g, Volume silver solution=200ml, agitation speed=250rpm, T=27oC)
4.4 Silver Adsorption from Real Photographic Waste
The concentration of metal in photogragraphic waste Ag, K, Na and Fe
before and after adsorption using AAS analysis were tabbulated in table 4.1.
From figure 4.12, sodium and potassium metal does not have any extraction
while extraction of iron is less than 0.6mmol/g. Silver has highest amount extracted
which is 1.6mmol/g. This means that EIR XAD7- Cyanex302 (kerosene) with
optimum parameters was selective towards silver as discussed in the section 4.2 and
4.3.
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Table 4.1: Characterization of metals in photographic waste before and after
adsorption process
Metal
Concentration (ppm)
Before After
Ag 833.2 654.2
K 3172 3172
Na 1771 1771
Fe 1026 961.3
Figure 4.12: Extraction of metals from photographic waste (Experimental condition:
EIR XAD7-Cyanex302 (Kerosene)= 0.0255g, volume photographic waste=25ml, pH
= 8.01, agitation speed=250rpm, T=27oC)
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4.6 Summary
The combination of adsorption and extraction method through synthesis of
extractant impregnated resin (EIR) becomes one of the promising technique in silver
recovery from photographic waste. Silver was extracted from photographic waste in
the certain adsorption parameters being examined. In this process, extractant,
adsorbent and diluents play important roles. Therefore, screening process choose
Cyanex302 as an extractant due to its selectivity towards silver metal. Adsorbent
XAD-7 was chosen that have large surface area and intermediate polarity. Diluent
kerosene was helping the adsorption by having low dielectric constant. In this
process, adsorption performance does not affected by pH as in general. If all theseparameters are utilized in correct condition with proper equipment selection, silver
can be extracted completely from photographic waste.
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CHAPTER 5
CONCLUSION AND RECOMMENDATION
5.1 Conclusions
Silver is one of the most valuable metal exist in the earth. The concentration
of this metal in photographic waste is quite high. Therefore, the recovery of silver
metal from photographic waste is become necessary. Adsorption using Extractant
Impregnated Resin (EIR) is the suggested method that can be implemented in the
photographic waste treatment before discharge.
Amberlite XAD-2 and XAD-7 were selected as adsorbents resin for
impregnation process. They were impregnated with Cyanex302 where ethanol and
kerosene as diluents. The SEM images show that the surface of EIR XAD7-
Cyanex302 (kerosene) has a rough skin compared to pure Amberlite XAD-7 while
for EIR XAD2-Cyanex302, there are no difference between their morphology. From
IR-Spectra, the existing of P=O bond in EIR XAD7-Cyanex302 (kerosene) and
XAD2-Cyanex302 (kerosene) indicate the successfulness of adsorbent modification
by the impregnation process
In order to achieve the objectives, varying the adsorption parameters were
tested to obtain the optimum condition for the SIR to perform. Ag(I) adsorption was
performed under batch process system. EIR XAD7- Cyanex302 with diluent
kerosene provides very attractive result as combination of adsorption parameter to
silver as a target metal ion. Acidic extractant Cyanex302 give high selectivity
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towards silver metal over the other metals. On the other hand, adsorbent XAD-7 was
chosen that have large surface area and intermediate polarity. Diluent kerosene was
helping the adsorption by having low dielectric constant that less interaction with
extractant and easy to vaporize.
The adsorption process at varies pH shows that pH does not affect the
adsorption performance since extractant- metal complex formation is not primarily
dependent on pH. Kinetic study of Ag(I) adsorption process show that the
adsorption achieved equilibrium at 34 hour. In the real photographic waste,
adsorption by EIR XAD7-Cyanex302 (kerosene) show highest adsorption capacity
and selectivity towards Ag(I) metal.
5.2 Recommendations and Future Works
This study stumbled upon several interesting problem which can be subjected
for future research. Therefore, further studies in a few aspects related to this research
could be carried for improvement and modification of this model of study:
i) Impregnation between polymer adsorbent and extractant show good
performance in metal extraction. The study of impregnation synthesis
between another adsorbent such as activated carbon or biomaterial with
extractant might be investigated in order to use economical adsorbent.
ii) The main issue in EIR adsorption process is effectiveness of the adsorption ina large amount of photographic waste. Large amount of photographic waste
need longer time of adsorption for contact time. Therefore, adsorption
process using continous system instead batch system.
iii) Desorption process of silver from EIR does not carried out in this study. So,
silver extracted from photographic waste become waste. Thus, desorption
process will be carried out to prevent another environmental problem.
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REFERENCES
Ayata, S., Kaynak, I. and Merdivan, M. (2008). Solid Phase Extractive
Preconcentration of Silver from Aqueous Samples. J. Environ. Monit.153:
1-4.
Burghoff, B., Zondervan, E. and de Haan , A.B. (2009). Phenol extraction withCyanex 923: Kinetics of the Solvent Impregnated Resin Application. J.
React. Funct. Polym. 69: 264-271.
Navarro, R., Saucedo, I., Nunez, A., Avila, M. and Guibal, E. (2008).
CadmiumExtraction from Hydrochloric Acid Solution XAD-7 Impregnated
With Cyanex921. J. React. Funct. Polym. 68: 557-571.
Kabay, N., Cortina, J.L., Trochimczuk, A. and Streat, M. (2010). Solvent