Tengku Nur Zulaikha-THESIS PSM 20102011

8/7/2019 Tengku Nur Zulaikha-THESIS PSM 20102011

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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

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