ELECTROMEMBRANE EXTRACTION AND ELECTROCHEMICAL MEASUREMENT
SYSTEM FOR HEAVY METAL IONS DETECTION IN AQUATIC ENVIRONMENTAL
SAMPLES
HAMSAWAHINI KUNASHEGARAN
UNIVERSITI TEKNOLOGI MALAYSIA
ELECTROMEMBRANE EXTRACTION AND ELECTROCHEMICAL
MEASUREMENT SYSTEM FOR HEAVY METAL IONS DETECTION IN
AQUATIC ENVIRONMENTAL SAMPLES
HAMSAWAHINI A/P KUNASHEGARAN
A thesis submitted in fulfilment of the
requirements for the award of the degree of
Doctor of Philosophy (Chemistry)
Faculty of Science
Universiti Teknologi Malaysia
AUGUST 2018
iii
In the name of God, The greatest and The kindest of all,
I dedicate this thesis
Specially to my Husband, Dinesh
For not giving up on me and tolerating my madness
My beloved daughter, Varnikaa
For reminding me of the goodness in this world and inspiring me to be the better
version of myself
Prof. Dr. Rahmalan Ahamad, Prof. Dr. Abdull Rahim Bin Mohd Yusuff
and Dr. Sathishkumar Palanivel
For guidance, knowledge, patience and trust on me
My beloved Amma and Appa
For always believed in me
My siblings
The whole family
For their endless love, support, encouragement, prayer for my success in
completing the journey of my research
iv
ACKNOWLEDGEMENT
First and foremost, I would like to thank God for His blessing and for the
strength that lead me this whole journey of this research. I would like to express my
deepest gratitude to my current and former supervisors, Prof. Dr. Rahmalan Ahamad
and Prof Dr. Abdull Rahim Bin Mohd Yusuf, respectively for their guidance,
knowledge, motivation, patience and trust on me throughout this whole work.
My gratitude is also extended to Dr. Sathishkumar Palanivel for his guidance
and advice while writing my research papers. My special thanks to Prof. Datuk Dr.
Ahmad Fauzi Bin Ismail and his research team members for their technical
assistance during my working in Advanced Membrane Technology Research Centre
(AMTEC).
Appreciation is also addressed to many other laboratory officers in the
Department of Chemistry, Faculty Science their help and assistance. I also
appreciated the financial assistance provided by Ministry of Higher Education
(MyPhD) during my Ph.D. candidature.
Finally, I am greatly indebted to my parents, siblings and husband for their
endless love, concern and encouragement all these years. I was blessed to have their
supports and spiritual strength to complete my research and thesis writing. There is
no better phrase than “Thank You for Everything and May God Bless all of you.”
v
ABSTRACT
Water contamination is a worldwide problem which deserves attention due to its
negative impact on ecosystem, human health as well as economic growth. Heavy metals are
a group of the pollutants that have received particular attention due to their high toxicity
even at concentration as low as parts per billion (ppb). Technology advancement in the field
of separation and detection of heavy metals has introduced sensitive and selective analytical
instruments for real aquatic environmental samples. However, real sample matrices can
reduce the quality of results. In modern analytical chemistry, there is a high demand for
accurate quantification of trace and ultra-trace of heavy metals from real aqueous samples. In
the present study, electromembrane extraction (EME) and electrochemical techniques were
combined to develop effective electrodes which can separate, pre-concentrate and determine
heavy metals such as Pb(II), Cr(VI) and Cd(II) in real aqueous samples. Electrochemically
reduced graphene oxide-graphite reinforced carbon (ErGO-GRC) was utilised in conjunction
with square wave anodic stripping voltammetry (SWASV) for the determination of Pb(II).
Meanwhile, selective and sensitive determinations of Cr(VI) was carried out using ex-situ
prepared nafion-coated antimony film on graphite reinforced carbon (NSbFE-GRC) by
square wave adsorptive stripping voltammetry (SWAdSV) in the presence of diethyltriamine
pentacetic acid (DTPA). Ex-situ prepared NSbFE-GRC was also used for simultaneous
determination of Pb(II) and Cd(II) by SWASV. Simple polyvinylidene fluoride (PVDF) flat
sheet membranes were synthesised and characterised in order to combine these developed
electrochemical techniques with EME. Heavy metals were extracted from an aqueous sample
solution into an acidic acceptor phase in the lumen of a PVDF membrane bag by the
application of voltage across the supported liquid membrane (SLM), consisting of organic
solvent and complexing carriers. Parameters affecting the EME were optimised for heavy
metals. The PVDF–ErGO–GRC electrode system attained enrichment factors of 40 times
and 80% extraction with relative standard deviation (n = 5) of 8.3% for Pb(II). Good
linearity in the range of 0.25-2 nM was obtained with correlation coefficient of 0.999. The
Pb(II) ions detection limit of PVDF–ErGO–GRC electrode was 0.09 nM. Meanwhile, the
PVDF–NSbFE–GRC system attained enrichment factors of 86.6 times, 95.6% extraction,
and good linearity in the range of 10-60 pM with correlation coefficient of 0.9933.
Furthermore, the limit of Cr(VI) detection was found to be around 0.83 pM for the developed
PVDF–NSbFE–GRC electrode. On the other hand, the PVDF–NSbFE–GRC was able to
attain enrichment factors of 49.3 and 68.4 times, 82.6% and 114.0% extractions, and good
linearity ranging from 2 to 10 pM with correlation coefficients of 0.9953 and 0.9883 for
Pb(II) and Cd(II), respectively. Furthermore, the limits of detection for Pb(II) and Cd(II)
were found to be around 0.65 pM and 0.60 pM, respectively. A chargeable battery operated
portable EME system was developed for quantitative determination of heavy metals. The
newly developed single setup electrochemical system was applied to the analysis of real
aqueous samples such as tap water, industrial waste water, river water and sea water, and it
was able to extract with percentage of extraction in the range of 78.7 -103.0% compared to
commercially available direct current power supply.
vi
ABSTRAK
Pencemaran air adalah masalah di seluruh dunia yang patut diberi perhatian
disebabkan oleh impak negatif terhadap ekosistem, kesihatan manusia serta pertumbuhan
ekonomi. Logam berat merupakan satu kumpulan pencemar yang telah menerima perhatian
khusus kerana ketoksikannya yang tinggi walaupun pada kepekatan serendah bahagian per
bilion (ppb). Kemajuan teknologi dalam bidang pemisahan dan pengesanan logam berat
telah memperkenalkan instrumen analisis yang peka dan selektif bagi sampel persekitaran
akuatik. Walau bagaimanapun, matriks sampel sebenar boleh mengurangkan kualiti hasil.
Dalam kimia analisis moden, terdapat permintaan yang tinggi bagi kuantifikasi tepat logam
berat surih dan ultra surih daripada sampel akueus sebenar. Dalam kajian ini, teknik
pengekstrakan elektromembran (EME) dan elektrokimia digabungkan untuk menghasilkan
elektrod yang boleh memisahkan, pra-memekatkan dan menentukan logam berat misalnya
Pb(II), Cr(VI) dan Cd(II) daripada sampel akueus sebenar. Karbon diperkuatkan grafin
oksida-grafit secara penurunan elektrokimia (ErGO-GRC) telah digunakan sempena dengan
voltammetri pelucutan anod gelombang segiempat (SWASV) bagi penentuan Pb(II).
Sementara itu, penentuan selektif dan sensitif Cr(VI) dijalankan menggunakan filem
antimoni yang dilapisi dengan nafion pada karbon diperkuatkan grafit (NSbFE-GRC) yang
disediakan dengan voltammetri pelucutan penjerapan gelombang segiempat (SWAdSV)
dengan kehadiran asid dietiltriamina pentasetik (DTPA). NSbFE-GRC yang disediakan
secara ex-situ juga digunakan untuk penentuan Pb(II) dan Cd(II) dengan SWASV. Membran
lembaran rata polivinilidena fluorida (PVDF) yang mudah telah disintesis dan dicirikan
untuk menggabungkan teknik elektrokimia yang dibangunkan itu dengan EME. Logam berat
telah diekstrak daripada larutan sampel akueus ke dalam fasa penerima berasid di dalam
lumen beg membran PVDF dengan menggunakan voltan merentasi membran cecair
disokong (SLM), yang terdiri daripada pelarut organik dan pembawa pengkompleks.
Parameter yang mempengaruhi EME telah dioptimumkan bagi logam berat. Sistem elektrod
PVDF-ErGO-GRC mencapai faktor pengayaan 40 kali dan pengekstrakan 80% dengan
sisihan piawai relatif (n = 5) 8.3% bagi Pb(II). Lineariti yang baik dalam julat 0.25-2 nM
telah diperolehi dengan pekali korelasi 0.999. Had pengesanan ion Pb(II) elektrod PVDF-
ErGO-GRC adalah 0.09 nM. Sementara itu, sistem PVDF-NSbFE-GRC mencapai faktor
pengayaan 86.6 kali, pengekstrakan 95.6%, dan lineariti yang baik dalam julat 10-60 pM
dengan pekali korelasi 0.9933. Tambahan pula, had pengesanan Cr(VI) didapati sekitar 0.83
pM bagi elektrod PVDF-NSbFE-GRC yang dibangunkan. Sebaliknya, PVDF-NSbFE-GRC
telah dapat mencapai faktor pengayaan 49.3 dan 68.4 kali, pengekstrakan 82.6% dan
114.0%, dan lineariti yang baik dari 2 hingga 10 pM dengan pekali korelasi masing-masing
0.9953 dan 0.9883 bagi Pb(II) dan Cd(II). Tambahan pula, didapati had pengesanan bagi
Pb(II) dan Cd(II) masing-masing adalah sekitar 0.65 pM dan 0.60 pM. Sistem EME mudah
alih yang menggunakan bateri boleh dicas semula telah dibangunkan bagi penentuan
kuantitatif logam berat. Sistem elektrokimia persediaan tunggal baharu yang dibangunkan itu
telah digunakan untuk analisis sampel akueus sebenar misalnya air paip, air sisa industri, air
sungai dan air laut, dan ia dapat mengekstrak dengan peratus pengekstrakan dalam julat
78.1-103.0% berbanding pembekal arus terus komersial.
vii
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES xiv
LIST OF FIGURES xviii
LIST OF ABBREVIATIONS xxx
LIST OF SYMBOLS xxxv
LIST OF APENDICES xxxvi
1 INTRODUCTION 1
1.1 Background of Research 1
1.2 Problem Statement 2
1.3 Objectives of the Study 4
1.4 Scope of the Study 4
1.5 Significance of Study 6
1.6 Novelty of Study 6
1.7 Thesis Outline 7
2 LITERATURE REVIEW 8
2.1 Green Separation and Pre-concentration
Techniques
8
2.1.1 Microextraction 8
viii
2.1.1.1 Solid-Phase Microextraction
(SPME)
9
2.1.1.2 Liquid-Phase Microextraction
(LPME)
9
2.1.2 Supported Liquid Membrane (SLM) 12
2.1.3 Electromembrane Extraction (EME) 15
2.1.3.1 The Principle of EME 16
2.1.3.2 Theoretical Aspects of EME 17
2.1.3.3 Different EME Configuration 19
2.2 Conventional Techniques for Heavy Metal
Determination
24
2.3 Voltammetric Techniques for Heavy Metal 29
2.3.1 Overview of Voltammetry 29
2.3.2 Electrode Modification 34
2.3.2.1 Graphite Reinforcement
Carbon
39
2.3.2.2 Metal Film Electrodes 41
2.4 Reduced Graphene Oxide 57
2.5 Electromembrane: Advances to Hyphenation
with Voltammetry
69
2.6 Summary 72
3 METHODOLOGY 73
3.1 Chemical and Reagents 73
3.2 General Instrumentation 74
3.3 Preparation of Stock Solution 75
3.3.1 Britton Robinson Buffer (BRB), 0.04M 75
3.3.2 Sodium Hydroxide (NaOH), 0.1M 75
3.3.3 Diethyltriamine Pentacetic (DTPA),
0.1M
75
3.3.4 Potassium Hydroxide (KOH), 2.0M 75
3.4 Liquid-Liquid Extraction 76
ix
3.4.1 Solubility of Complexing Carrier in
Organic Solvent
76
3.4.2 Liquid-liquid Extraction Experiments 76
3.4.3 Optimization of Experimental
Parameters
77
3.4.3.1 Effect of pH and Type of
Complexing Carrier
77
3.4.3.2 Effect of Organic Solvents 78
3.4.3.3 Effect of Stripping Phase 79
3.5 Preparation of Electrochemically Reduce
Graphene Oxide Modified Graphite
Reinforcement Carbon
80
3.5.1 Instrumentation 81
3.5.2 Preparation of Exfoliated Graphene
Oxide
81
3.5.3 Electrode Preparation 82
3.5.4 Electrochemical Analysis 82
3.6 Preparation of Nafion Coated Antimony Film
Modified Graphite Reinforcement Carbon
83
3.6.1 Instrumentation 83
3.6.2 Electrode Preparation 83
3.6.3 Electrode Electrochemical Analysis 84
3.7 Effects of Coexisting Ions on Detecting Pb(II),
Cd(II) and Cr(VI)
85
3.8 Calibration Curve 85
3.9 Application of ERGO-GRC and NSbFE-GRC
electrode to Real Water Samples
85
3.10 Fabrication and Characterization of PVDF
Membrane
86
3.11 Preparation of agarose gel 86
3.12 Electromembrane Extraction 87
3.13 Application of PVDF-ERGO-GRC and PVDF
NSbFE-GRC Electrode to Real Water Samples
89
x
3.14 Development of Portable and Chargeable EME
Sampling Device
90
4 PRELIMINARY STUDIES AND
VOLTAMMETRY TECHNIQUES
95
4.1 Liquid – Liquid Extraction 95
4.1.1 Selection of Organic Solvent 95
4.1.2 Liquid-Liquid Extraction of Pb(II) 98
4.1.3 Liquid-Liquid Extraction of Cr(VI) 102
4.1.4 Liquid-Liquid Extraction of Cd(II) 109
4.2 Electrochemical Analysis 114
4.2.1 Electrochemically Reduced Graphene
Oxide
115
4.2.1.1 FE-SEM Analysis 115
4.2.1.2 Fourier Transform Infrared
Spectrometer (FTIR) of
Graphene Oxide
117
4.2.1.3 Characterisation of Electrode 118
4.2.1.4 Electrochemical Behaviour of
Pb(II) at ErGO-GRC
119
4.2.1.5 Effect of Different GRC
Grade on ErGO Modification
120
4.2.1.6 Effect of constant applied
cathodic potential and
reduction time
121
4.2.1.7 Effect of pH Time 125
4.2.1.8 Effect of Drop-Cast Drying 128
4.2.1.9 Reproducibility, Stability and
Selectivity
130
4.2.1.10 Application of ErGO-GRC
Electrode in Real Sample
Analysis
133
4.2.2 Nafion-Coated Ex-situ Antimony Film 135
xi
modified Graphite Reinforced Carbon
(NSbFE-GRC) for Simultaneous
Detection of Pb(II) and Cd(II)
4.2.2.1 FE-SEM Analysis 135
4.2.2.2 Characterisation of NSbFE-
GRC
136
4.2.2.3 Effect of Sb(III)
Concentration, Electrolysis
Time Plating Potential and
Concentration of HCl
138
4.2.2.4 Effect of Accumulation
Potential
141
4.2.2.5 Effect of Accumulation Time 142
4.2.2.6 Effect of Frequency, Step
Potential and Pulse
Amplitude
142
4.2.2.7 Reproducibility, Stability and
Selectivity
143
4.2.2.8 Application of NSbFE-GRC
Electrodes to Real Sample
Analysis
145
4.2.3 Nafion-Coated Ex-situ
Antimony Film modified
Graphite Reinforced Carbon
(NSbFE-GRC) for Selective
Detection of Cr(VI)
147
4.2.3.1 Characterisation of NSbFE-
GRC
147
4.2.3.2 Effect of Sb(III)
Concentration, Plating Time
and Plating Potential
149
4.2.3.3 Effect of pH 152
4.2.3.4 Effect of 153
xii
Diethyltriaminepentacetic
Acid (DTPA) Concentration
4.2.3.5 Effect of KNO3 154
4.2.3.6 Effect of Adsorptive Potential
(Eads)
155
4.2.3.7 Effect of Adsorptive Time
(tads)
156
4.2.3.8 Effect of Frequency, Step
Potential and Pulse
Amplitude
157
4.2.3.9 Reproducibility, Stability and
Selectivity
157
4.2.3.10 Application of NSbFE-GRC
Electrodes to Real-Life
Sample Analysis
160
4.3 Summary 161
5 ELECTROMEMBRANE AND PORTABLE
POWER SUPPY DEVICE
162
5.1 Electromembrane Extraction 162
5.1.1 Influence of Membrane Composition on
Extraction Voltage
163
5.1.1.1 The influence of membrane
composition on extraction
voltage
167
5.1.2 Effect of Organic Solvents 169
5.1.3 Effect of pH on donor phase 172
5.1.4 Effect of carrier concentration in 1-
octanol
175
5.1.5 Effect of Stirring Rate 178
5.1.6 Effect of Extraction Time 180
5.1.7 Effect of Volume Ratio of Acceptor
Phase to Donor Phase
183
xiii
5.1.8 Effect of Agarose gel 185
5.1.9 Analytical performance 188
5.1.9.1 Calibration Graph for
Selective Determination of
Cr(VI)
189
5.1.9.2 Calibration Graph for
Selective Determination of
Pb(II)
192
5.1.9.3 Calibration Graph for
Simultaneous Detection of
Pb(II) and Cd(II)
194
5.2 Portable Power Supply Device (PPSD) 198
5.2.1 Application PPSD on Selective EME 200
5.2.2 Application PPSD on Simultaneous
EME
201
5.3 Summary 204
6 CONCLUSION AND RECOMMENDATIONS 205
6.1 Conclusion 205
6.2 Recommendations 206
REFERENCES 208
Appendices A-G 242-248
xiv
LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 Application of EME for heavy metal separation and pre-
concentration
21
2.2 Maximum permissible levels of some heavy metals in
drinking water regulated or recommended by WHO and
EPA
26
2.3 Previous reports on analytical spectroscopic technique
for heavy metals determination
27
2.4 Voltammetric techniques applied for environmental
applications
30
2.5 Previous reports on Bare electrode (Unmodified) for
heavy metal ion detection
36
2.6 The property and advantage of modifier on the surface
of working electrodes
37
2.7 Previous reports on Mercury film electrode for heavy
metal ion detection
43
2.8 Previous reports on Bismuth film electrode for heavy
metal ion detection
45
2.9 Recent reports on antimony film electrode for heavy
metal ion detection
51
2.10 Recent reports on Copper, lead, tin, gallium film
electrodes for heavy metal ion detection
54
2.11 The property and advantages of graphene and graphene
oxide on the surface of working electrodes
60
2.12 Recent reports on reduced graphene oxide modified
electrode for heavy metal ion detection
62
3.1 Extraction conditions for each metal ions of interest 78
xv
3.2 Operating condition for each metal to analyse the effect
of organic solvents
79
3.3 Operating condition for each metal to analyse the effect
of stripping phase
80
3.4 The operating conditions in EME optimisation and
electrochemical determination
91
3.5 The parameters involved for simultaneous separation
and pre-concentration of Pb(II), Cr(VI) and Cd(II)
94
4.1 Miscibility of organic solvent with selected complexing
carriers
96
4.2 Viscosity, surface tension and solvent density of
toluene, NPOE, 1-Octanol (Dzygiel and Wieczorek,
2010)
97
4.3 Operating conditions for Pb(II) extraction studies 98
4.4 The operating condition of Cr(VI) for ICPMS 103
4.5 Operating Conditions for cadmium (II) extraction
studies
110
4.6 Effect of HCl concentration on GO film reduction and
C/O ratio
127
4.7 Comparison of different electrodes for the determination
of Pb(II)
132
4.8 Interference for determining1µM Pb(II) in 1.0 M HCl 132
4.9 The determination of Pb(II) ions in real and spiked
samples
133
4.10 Comparison of different electrode for Pb(II) ions
determination in real samples
134
4.11 Comparison of SbFE electrodes for the determination of
Pb(II) and Cd(II).
145
4.12 The determination of Pb(II) and Cd(II) ions in real and
spiked samples
146
4.13 Comparison of different electrodes for the determination
of Cr(VI).
159
4.14 The determination of Cr(VI) in real and spiked samples 160
xvi
5.1 Parameters involved in EME and electrochemical
determination of Cr(VI), Pb(II) and Cd(II) on
investigating the influence of membrane composition
(PVDF12, PVDF17 and PVDF22) on extraction voltage.
165
5.2 Characterisation of PVDF membrane 167
5.3 Parameters involved in EME and electrochemical
determination of Cr(VI), Pb(II) and Cd(II) on
investigating the effect of organic solvents (Toluene,
NPOE and 1-octanol).
171
5.4 Parameters involved in EME and electrochemical
determination of Cr(VI), Pb(II) and Cd(II) on
investigating the effect pH on donor phase (pH 1 to 9).
174
5.5 Parameters involved in EME and electrochemical
determination of Cr(VI), Pb(II) and Cd(II) on
investigating the effect of carrier concentration in 1-
octanol
177
5.6 Parameters involved in EME and electrochemical
determination of Cr(VI), Pb(II) and Cd(II) on
investigating the effect of stirring rate
179
5.7 Parameters involved in EME and electrochemical
determination of Cr(VI), Pb(II) and Cd(II) on
investigating the effect of extraction
182
5.8 Parameters involved in EME and electrochemical
determination of Cr(VI), Pb(II) and Cd(II) on
investigating the effect of volume ratio of acceptor
phase to donor phase
184
5.9 Parameters involved in EME and electrochemical
determination of Cr(VI), Pb(II) and Cd(II) on
investigating the effect agarose gel
187
5.10 Parameters involved in EME and electrochemical
determination for calibration curve of Pb(II), Cd(II) and
Cr(VI)
191
xvii
5.11 The determination of Cr(VI) in water samples using
EME-SWAdSV system
192
5.12 The determination of Pb(II) ions in water samples using
EME-SWV system
194
5.13 The determination of Pb(II) and Cd(II) in water samples
using EME-SWASV system
197
5.14 Cd(II) extraction efficiency using commercial DC
power supply and PSSD
200
5.15 Simultaneous EME of Cr(VI), Pb(II) and Cd(II) using
PPSD-PVDF-NSbFE-GRC in Sea water
202
5.16 Simultaneous EME of Cr(VI), Pb(II) and Cd(II) using
PPSD-PVDF-NSbFE-GRC in Industrial waste water
202
5.17 Parameters involved in EME and electrochemical
determination for calibration curve of Pb(II), Cd(II) and
Cr(VI)
203
xviii
LIST OF FIGURES
FIGURE NO. TITLE PAGE
2.1 The general concept of supported liquid membrane
(SLM). Mn+
: metal ions, A: carrier, H+: counter ion
and MAn: metal-carrier complex
12
2.2 Microextraction modes used in HF-LPME. (A) three-
phase system; and (B) two-phase system
14
2.3 Schematic illustration of an electromembrane
extraction (EME) setup
17
2.4 Drop-to-drop EME setup 20
2.5 Online EME 23
2.6 Picture of the Pa-EME system (a) and a principle
drawing of a single well (b)
24
2.7 Schematic diagram of electrochemical cell (a) Cross-
section side view; and (b) Top view of cap.
32
2.8 Metals and semi-metals that can be determined by
stripping voltammetry.
33
2.9 Schematic for the oxidation procedures of graphite to
GO by using the Staudenmaier (GO-ST), Hofmann
(GO-HO), Hummers (GO- HU), and Tour (GO-TO)
methods (Chua et al. 2012).
58
2.10 Schematic chemical structures of graphene, graphene
oxide, and reduced graphene oxide
58
2.11 Route of graphite to reduce graphene oxide
(Graphene‐ Based Materials Functionalization with
Natural Polymeric Biomolecules).
59
xix
2.12 Cyclic voltammograms of a GO-modified GCE in PBS
(pH 5.0) pre-aerated with nitrogen gas at a scan rate of
50 mV/s and with initial potential at 0.0 V(Guo et al.
2009).
66
2.13 CVs of the ErGO/GCE (electrochemically reduced at -
1.3 V for different time) in 5mM HCl at a scan rate of
100 mV s-1 (Guo et al. 2009).
67
2.14 Cyclic voltammetric profiles of electrochemical
reduction of oxygen-containing groups. Conditions:
PBS (50mm), background electrolyte (pH 7.2). Scan
rate: 100 mVs-1
(Chua et al. 2012)
68
2.15 Schematic presentation of (A) EME set up and (B)
voltammetric determination of selected heavy metals
in a single drop (Kamyabi & Aghaei 2016a; Kamyabi
& Aghaei 2016b)
70
2.16 Schematic illustrations of the equipment used for
extraction (A) and for in-situ determination of CLZ by
EME-DPV (B) (Rouhollahi et al. 2016)
71
2.17 The schematic illustration of the electromembrane
extraction (EME) and electrochemical detection setup
for diclofenac (Rouhollahi et al. 2016).
72
3.1 The design for simultaneous separation, pre-
concentration of EME with electrochemical detection
system: EME extraction (step I) and detection (step II)
of Pb(II) (WE: working electrode, RE: reference
electrode and AE: auxiliary electrode).
88
3.2 The design for simultaneous separation, pre-
concentration of EME with electrochemical detection
system: EME extraction (step I) and detection (step II)
of Cr(VI) (WE: working electrode, RE: reference
electrode and AE: auxiliary electrode).
88
xx
3.3 The design for simultaneous separation, pre-
concentration of EME with electrochemical detection
system: EME extraction (step I) and detection (step II)
of Pb(II) and Cd(II) (WE: working electrode, RE:
reference electrode and AE: auxiliary electrode).
89
3.4 Circuit for portable and chargeable EME device
(portable power supply device (PPSD))
92
3.5 The parallel EME setup for simultaneous separation
and pre-concentration of Pb(II), Cr(VI) and Cd(II)
93
4.1 The effect of pH and the type of complexing carriers
on the percentage of Pb(II) extraction.
99
4.2 The effect of the lead species on the percentage of
Pb(II) extraction using 20 % of D2EHPA in toluene.
100
4.3 The effect of organic solvent (Toluene, NPOE, n-
heptane and 1-octanol) on PbCl2 and PbNO3.
101
4.4 Effect of acceptor phase on the stripping studies of
Cr(VI), and Other conditions as stipulated in Table 4.4.
102
4.5 The effect of pH and the type of complexing carriers
on the percentage of Cr(VI) extraction.
104
4.6 The effect of types of acid on the percentage of Cr(VI)
extraction using Aliquat 336 as complexing carrier.
106
4.7 The effect of types of mineral acid on the percentage
of Cr(VI) extraction using TBP as complexing carrier.
107
4.8 Effect of organic solvent on the extraction of
chromium (VI) using TBP and Aliquat 336 in acidic
medium. Other conditions as stipulated in Table 4.4.
108
4.9 Effect of acceptor phase on the stripping studies of
Cr(VI), and Other conditions as stipulated in Table 4.4
109
4.10 The effect of pH and the type of complexing carriers
on the percentage of Cd(II) extraction.
111
4.11 The effect of NaCl concentration (0.1 – 1.0 M) on the
percentage of Cd(II) extraction.
112
xxi
4.12 Effect of organic solvent on the extraction of Cd(II)
using D2EHPA and Aliquat 336. Other conditions as
stipulated in Table 4.4.
113
4.13 Effect of acceptor phase on the stripping studies of
Cr(VI), and other conditions as stipulated in Table 4.4
114
4.14 FE-SEM images of (a) GRC, (b) GO-GRC and (c)
ErGO-GRC
116
4.15 FTIR Spectrum for Graphene Oxide 117
4.16 Cyclic voltammogram of (a) first scan, (b) second
scan, and (c) third scan of GO/(HB)GRC in 0.1M HCl
with experimental parameters as follows: Ei = 0 mV,
Ef = -1700 mV and scan rate = 100 mVs-1
.
118
4.17 Cyclic voltammogram obtained for 1.2 mM of Pb(II)
ions in 0.1M HCl (pH 2) with experimental parameters
as follows: Ei = -1200 mV, and scan rate = 100mVs-1
.
120
4.18 Effect of different grades of GRC on the cyclic
voltammetry peak current of ErGO modified electrode
and unmodified electrode in 0.1M HCl with 2 mM of
Pb(II) ions
121
4.19 The resistivity value for GRC grades electrode 122
4.20 Cyclic voltammogram of GO-GRC fabricated at
different cathodic potentials of -0.5 V to -1.5 V in 0.1
M HCl solution containing 1.2 mM of Pb(II) ions with
experimental parameters as follows: Ei = -1200 mV
and scan rate = 100 mVs-1
. The GO modified HB-GRC
was immersed into 0.1 M HCl solution, and the
cathodic potentials were applied using a potentiostat
for 10 min.
123
4.21 Current vs time (i vs t) for the electrolysis of 10 μL
GO modified GRC at potential (a) -0.5 V, (b) -0.7 V
(c) -0.8 V, and (d) -1.0 V in 0.1M HCl.
124
xxii
4.22 SWVs shows the effect of HCl concentration on Pb(II)
ions (6 x10 -8
M) with experimental parameters as
follows: Ei = -1200 mV, Ef = 0 mV, S.W. amplitute =
35 mV, step frequency = 50Hz, step height = 1 mV,
volume of GO = 10 μl of 0.1% of aqueous colloidal,
reduction potential of GO = -0.8 V for 10 min for
ErGO modified GRC.
126
4.23 SWVs shows the effect of HCl concentration on Pb(II)
ions (6 x10 -8
M) with experimental parameters as
follows: Ei = -1200 mV, Ef = 0 mV, S.W. amplitute =
35 mV, step frequency = 50Hz, step height = 1 mV,
volume of GO = 10 μl of 0.1% of aqueous colloidal,
reduction potential of GO = -0.8V for 10 min for
ErGO modified GRC.
126
4.24 Peak potential versus pH with experimental parameters
as follows: Ei = -1200 mV, Ef = 0 mV, S.W. amplitute
= 35 mV, step frequency = 50Hz , step height = 1 mV,
volume of GO = 10 μl of 0.1% of aqueous colloidal,
reduction potential of GO = -0.8V for 10 min for
ErGO modified GRC
128
4.25 The effect of modification time of electrode in 0.1 M
HCl on Pb(II) ions (1 x10 -6
M) with experimental
parameters as follows: Ei = -1200 mV, Ef = 0 mV,
S.W. amplitute = 35 mV, step frequency = 50Hz , step
height = 1 mV, volume of GO = 10 µl of 0.1% of
aqueous colloidal, reduction potential of GO = -0.8V
for 10 min for ErGO modified GRC.
129
xxiii
4.26 SWVs shows the oxidation peak current of Pb(II) ions
for Pb(II) ions concentration (a) 3, (b) 4.5, (c) 6.0, (d)
7.5, (e) 9.0, (f) 10.5, (g) 12.0, (h) 13.5, (i) 15.0 nM;
with experimental parameters as follows: Ei = -1200
mV, Ef = 0 mV, S.W. amplitute = 35 mV, step
frequency = 50 Hz, step height = 1 mV, volume of
GO= 10 µL of 0.1% of aqueous colloidal, reduction
potential of GO = -0.8 V for 10 min for ErGO
modified GRC. The calibration plot is shown in the
inset.
131
4.27 FE-SEM images of (a) GRC, (b) N-GRC, (c) SbFE-
GRC and (d) NSbFE-GRC
136
4.28 SWASV of 0.5 nM of Pb(II) and Cd(II) using bare
GRC, N-GRC, SbFE-GRC and NSbFE-GRC. Plating
conditions: 0.01M HCl, 10 mgL-1
of Sb(II), -1200 V
plating potential and 240 s of plating time. Detection
conditions: Eacc: −1.0 V; tacc: 60 s; step amplitude: 4
mV, pulse amplitude: 50 mV, and frequency: 25 Hz.
137
4.29 Effect of HCl concentration on plating and detection of
10 nM of Pb(II) and Cd(II) in 0.1 M HCl. Conditions:
Eacc: −1.0 V; tacc: 35 s; step amplitude: 4 mV, pulse
amplitude: 50 mV, and frequency: 25 Hz.
138
4.30 Effect of concentration of Sb(III) on plating and
detection of Pb(II) and Cd(II) in 0.1 M HCl.
Conditions: Eacc: −1.0 V; tacc: 35 s; step amplitude: 4
mV, pulse amplitude: 50 mV, and frequency: 25 Hz.
139
4.31 The effect of plating time on the oxidation peak
current of Pb(II) and Cd(II) in 0.1 M HCl. Conditions:
Eacc: −1.0 V; tacc: 35 s; step amplitude: 4 mV, pulse
amplitude: 50 mV, and frequency: 25 Hz.
140
xxiv
4.32 The effect of plating potential on the oxidation peak
current of Pb(II) and Cd(II) in 0.1 M HCl. Conditions:
Eacc: −1.0 V; tacc: 35 s; step amplitude: 4 mV, pulse
amplitude: 50 mV, and frequency: 25 Hz.
140
4.33 The effect of the accumulation potential (Eacc) on the
oxidation peak current of the Pb(II) and Cd(II).
Conditions: Eacc: − 0.6 to -1.6 V; tacc: 35 s; step
amplitude: 4 mV, pulse amplitude: 50 mV, and
frequency: 25 Hz.
141
4.34 The effect of accumulation time (tacc) on the oxidation
peak current of the Pb(II) and Cd(II). Conditions: Eacc:
-1.2 V; tacc: 0-100 s; step amplitude: 4 mV, pulse
amplitude: 50 mV, and frequency: 25 Hz.
142
4.35 SWASVs shows the oxidation peak current of Pb(II)
and Cd(II) for Pb(II) ions concentration (a) 0, (b) 0.1,
(c) 0.2, (d) 0.3, (e) 0.4, (f) 0.5 and (g) 0.6 nM with
experimental parameters as follows: Ei = -1200 mV,
Ef = -0.2 mV, S.W. amplitute = 50 mV, step frequency
= 50Hz, step height = 1 mV.
144
4.36 The calibration plot for (a) Pb(II) and (b) Cd(II).
Experimental parameters as in caption Figure 4.33.
144
4.37 SWAdSV of Cr(III)-DTPA (25 nM) using N-GRC,
SbFE-GRC and NSbFE-GRC in acetate buffer (pH 6).
Conditions: Concentration of Sb(III): 0.2 – 2.5 mgL-1
,
concentration of DTPA: 5 mM, concentration of
KNO3: 0.5 M, Eads: −0.80 V; tads: 120 s; step
amplitude: 5 mV, pulse amplitude: 25 mV, and
frequency: 25 Hz.
149
xxv
4.38 Effect of concentration of Sb(III) on reduction peak
current of Cr(III)-DTPA (50 nM) using SWAdSV in
acetate buffer (pH 6). Conditions: Concentration of
Sb(III): 0.2 – 2.5 mgL-1
, Sb(III) plating time: 150 s,
Sb(III) plating potential -1.0 V, concentration of
DTPA: 5 mM, concentration of KNO3: 0.5 M, Eads:
−0.80 V; tads: 120 s; step amplitude: 5 mV, pulse
amplitude: 25 mV, and frequency: 25 Hz.
150
4.39 Effect of Sb(III) plating time on reduction peak current
of Cr(III)-DTPA (50 nM) using SWAdSV in acetate
buffer (pH 6). Conditions: Concentration of Sb(III):
1.0 mgL-1
, Sb(III) plating time: 0 - 300 s, Sb(III)
plating potential: -1.0 V, concentration of DTPA: 5
mM, concentration of KNO3: 0.5 M, Eads: −0.80 V;
tads: 120 s; step amplitude: 5 mV, pulse amplitude: 25
mV, and frequency: 25 Hz.
151
4.40 Effect of Sb(III) plating potential on reduction peak
current of Cr(III)-DTPA (50 nM) using SWAdSV in
acetate buffer (pH 6). Conditions: Concentration of
Sb(III): 1.0 mgL-1
, Sb(III) plating time: 240 s, Sb(III)
plating potential -0.9 to -1.5 V, concentration of
DTPA: 5 mM, concentration of KNO3: 0.5 M, Eads: -
0.80 V; tads: 120 s; step amplitude: 5 mV, pulse
amplitude: 25 mV, and frequency: 25 Hz.
151
4.41 Effect of pH of buffer (2 to 9) on reduction peak
current of Cr(III)-DTPA (20 nM). Conditions:
Concentration of Sb(III): 1.0 mgL-1
, Sb(III) plating
time: 240 s, Sb(III) plating potential -1.2 V,
concentration of DTPA: 10 mM, concentration of
KNO3: 0.5 M, Eads: −0.80 V; tads: 120 s; step
amplitude: 5 mV, pulse amplitude: 25 mV, and
frequency: 25 Hz.
152
xxvi
4.42 Effect of concentration of DTPA on reduction peak
current of Cr(III)-DTPA (20 nM) using SWAdSV in
acetate buffer (pH 6). Conditions: Concentration of
Sb(III): 1.0 mgL-1
, Sb(III) plating time: 240 s, Sb(III)
plating potential -1.2 V, concentration of DTPA: 0 - 30
mM, concentration of KNO3: 0.5 M, Eads: −0.80 V;
tads: 120 s; step amplitude: 5 mV, pulse amplitude: 25
mV, and frequency: 25 Hz.
153
4.43 Effect of KNO3 concentration on reduction peak
current of Cr(III)-DTPA (20 nM) using SWAdSV in
acetate buffer (pH 6). Conditions: Concentration of
Sb(III): 1.0 mgL-1
, Sb(III) plating time: 240 s, Sb(III)
plating potential -1.2 V, concentration of DTPA: 15
mM, concentration of KNO3: 0 – 1.0 M, Eads: −0.80 V;
tads: 120 s; step amplitude: 5 mV, pulse amplitude: 25
mV, and frequency: 25 Hz.
154
4.44 Effect of adsorptive potential on reduction peak
current of Cr(III)-DTPA (25 nM) using SWAdSV in
acetate buffer (pH 6). Conditions: Concentration of
Sb(III): 1.0 mgL-1
, Sb(III) plating time: 240 s, Sb(III)
plating potential -1.2 V, concentration of DTPA: 15
mM, concentration of KNO3: 0.6 M, Eads: - 0.5 to -1.1
V; tads: 120 s; step amplitude: 5 mV, pulse amplitude:
25 mV, and frequency: 25 Hz.
155
4.45 Effect of adsorptive time on reduction peak current of
Cr(III)-DTPA (20 nM) using SWAdSV in acetate
buffer (pH 6). Conditions: Concentration of Sb(III):
1.0 mgL-1
, Sb(III) plating time: 240 s, Sb(III) plating
potential: -1.2 V, concentration of DTPA: 15 mM,
concentration of KNO3: 0.6 M, Eads: - 0.80 V; tads: 0 -
500 s; step amplitude: 5 mV, pulse amplitude: 25 mV,
and frequency: 25 Hz.
156
xxvii
4.46
SWAdSVs shows the reduction peak current of Cr(VI)
for concentration: (a) 0, (b) 0.2, (c) 0.3, (d) 0.4, (e) 0.5,
(f) 0.6, and (g) 0.7 nM with experimental parameters
as follows: Concentration of Sb(III): 1.0 mgL-1,
Sb(III) plating time: 240 s, Sb(III) plating potential: -
1.2 V, concentration of DTPA: 15 mM, concentration
of KNO3: 0.6 M, Eads: - 0.80 V; tads: 200 s; step
amplitude: 5 mV, pulse amplitude: 25 mV, and
frequency: 25 Hz. The calibration plot is shown in the
inset.
158
5.1 The influence of membrane composition (PVDF12,
PVDF17 and PVDF22) on extraction voltage of
selective EME for (a) Cr(VI)-NSbFE-GRC and (b)
Pb(II)-ErGO-GRC and simultaneous EME for (c)
Pb(II)-NSbFE-GRC and (d) Cd(II)-NSbFE-GRC. The
parameters involved in EME and electrochemical
determination stipulated in Table 5.1.
164
5.2 FE-SEM image of (a) PVDF22, (b) PVDF17 and (c)
PVDF12 membranes
168
5.3 The effect of organic solvents (1-octanol, NPOE,
toluene) on selective EME for (a) Cr(VI)-NSbFE-GRC
and (b) Pb(II)-ErGO-GRC and simultaneous EME for
(c) Pb(II)-NSbFE-GRC and (d) Cd(II)-NSbFE-GRC.
The parameters involved in EME and electrochemical
determination stipulated in Table 5.3.
170
5.4 The effect of pH of donor phase on (pH 1 to 9) on
selective EME for (a) Cr(VI)-NSbFE-GRC and (b)
Pb(II)-ErGO-GRC and simultaneous EME for (c)
Pb(II)-NSbFE-GRC and (d) Cd(II)-NSbFE-GRC. The
parameters involved in EME and electrochemical
determination stipulated in Table 5.4.
173
xxviii
5.5 The effect of carrier concentration in 1-octanol on
selective EME for (a) Cr(VI)-NSbFE-GRC and (b)
Pb(II)-ErGO-GRC and simultaneous EME for (c)
Pb(II)-NSbFE-GRC and (d) Cd(II)-NSbFE-GRC. The
parameters involved in EME and electrochemical
determination stipulated in Table 5.5.
176
5.6 The effect of stirring rate on selective EME for (a)
Cr(VI)-NSbFE-GRC and (b) Pb(II)-ErGO-GRC and
simultaneous EME for (c) Pb(II)-NSbFE-GRC and (d)
Cd(II)-NSbFE-GRC. The parameters involved in EME
and electrochemical determination stipulated in Table
5.6.
178
5.7 The effect of extraction time on selective EME for (a)
Cr(VI)-NSbFE-GRC and (b) Pb(II)-ErGO-GRC and
simultaneous EME for (c) Pb(II)-NSbFE-GRC and (d)
Cd(II)-NSbFE-GRC. The parameters involved in EME
and electrochemical determination stipulated in Table
5.7.
181
5.8 The effect of donor phase volume on selective EME
for (a) Cr(VI)-NSbFE-GRC and (b) Pb(II)-ErGO-GRC
and simultaneous EME for (c) Pb(II)-NSbFE-GRC and
(d) Cd(II)-NSbFE-GRC. The parameters involved in
EME and electrochemical determination stipulated in
Table 5.8.
183
5.9 Effect of agarose gel as salt bridge (a) without and (b)
with on detection of 0.25 nM Cr(VI). The parameters
involved in EME and electrochemical determination
stipulated in Table 5.9.
186
5.10 Effect of agarose gel as salt bridge (a) without and (b)
with on detection of 1.0 nM Pb(II). The parameters
involved in EME and electrochemical determination
stipulated in Table 5.9.
188
xxix
5.11 Effect of agarose gel as salt bridge (a) without and (b)
with on detection of 0.1 nM Cd(II) and Pb(II). The
parameters involved in EME and electrochemical
determination stipulated in Table 5.9.
188
5.12 SWAdSV shows the oxidation peak current of Cr(VI)
at different concentrations: (a) 10, (b) 20, (c) 30, (d)
40, (e) 50 and (f) 60 pM; with extraction condition as
shown in Table 5.10. The calibration plot is shown in
the inset.
190
5.13 SWASV shows the oxidation peak current of Pb(II) at
different concentrations: (a) 0.25, (b) 0.5, (c) 0.75, (d)
1.0, (e) 1.25, (f) 1.5, (g) 1.75 and (h) 2.0 nM; with
extraction condition as shown in Table 5.10. The
calibration plot is shown in the inset.
193
5.14 SWV shows the oxidation peak current of Pb(II) and
Cd(II) at different concentrations: (a) 0, (b) 2, (c) 4, (d)
6, (e) 8, and (f) 10 pM; with extraction condition as
shown in Table 5.10.
196
5.15 The calibration plot for (a) Pb(II) and (b) Cd(II)
ranging from 0 to 10 pM
196
5.16 Comparative in term of size of commercial DC power
supply and PSSD
199
5.17 (a) Front and (b) side view of portable power supply
device (PSSD)
199
xxx
LIST OF ABBREVIATION
2-MBT - 2-mercaptobenzothiazole
2-MBT - 2-mercaptobenzothizole
4-CNPy - 4-cyanopyridine
4-Cpy - 4-cyanopyridine
AAS - Atomic absorption spectrophotometry
ADDPA - ammonium diethyl dithiophosphate
AdSV - Adsorptive Stripping voltammetry
Aliquat 336 - Tricaprylylmethyl ammonium chloride
AlOOH - Aluminium oxide hydroxide
AP - acceptor phase
ASV - Anodic stripping voltammetry
AuNP - Gold nano particles
Au-RGO -
modification of GC electrode with gold - reduced
graphene oxide
BDDE - boron-doped diamond
BiFe - Bismuth film electrode
BRB - Britton-Robinson buffer
Cd(II) - Cadmium ions
CDC - Centre for Disease Control
CE - capillary electrophoresis
AE - auxilary electrode
CE-C4D -
capillary electrophoresis with capacitively coupled
contactless conductivity detection
CeO2 - Cerium(IV) oxide
CF - carbon fiber
CH3COOH - acetic acid
CLZ - clozapine
xxxi
CNTs - Carbon nanotubes
CPE - Carbon paste electrode
Cr - Chromium
Cr–DPC - Cr-diphenyl carbazide
CSV - Cathodic Stripping Voltammetry
CV - Cyclic voltammetry
CW - carbowax
Cyphos 101 - phosphonium chloride
D2EHPA - di-2-ethylhexylphosphoric acid
DC - Direct current
DLLME - dispersive liquid–liquid microextraction
DME - dropping mercury electrode
DP - donor phase
DP - donor phase
DPAdSV - Differential Pulse Adsorptive Stripping Voltammetry
DPASV - Differential pulse anodic stripping voltammetry
DPV) - differential pulse voltammetry
DSPE - dispersive solid phase extraction
DTPA - Diethyltriamine Pentacetic Acid
EDTA - Ethylenediaminetetraacetic acid
EFi - enrichment factor of analyte i
EFmax - maximum attainable EF
EG - Exfoliated graphite
EME - Electromembrane extraction
EPA - US Environmental Protection Agency
ER - extraction recovery
ErGO - Electrochemically reduced graphene oxide
ErGO-GRC - electrochemically reduced graphene oxide
ERi - extraction recovery of analytes i
FAO - Joint Food and Agricultural Organization
FESEM - Field emission scanning electron microscopy
GC - Glassy carbon
GCE - Glassy carbon electrode
xxxii
GF-AAS - graphite furnace atomic absorption spectroscopy
GRC - graphite reinforcement carbon
H2SO4 - sulphuric acid
HCl - hydrochloric acid
HF-LPME - hollow fiber-liquid phase microextraction
HMDE - hanging mercury drop electrode
HNO3 - nitric acid
HPLC - High performance liquid chromatography
HP-β-CD - Hydroxypropyl-β-cyclodextrin
ICPMS - Inductively coupled plasma-mass spectrometry
ICP-OES - inductively coupled plasma-optical emission spectrometry
IL - Ionic liquids
KOH - Potassium Hydroxide
LLE - liquid –liquid extraction
LOD - Limit of detection
LPME - liquid phase microextraction
LSV - Linear sweep voltammetry
MFE - Mercury film electrode
MWCNT - Multi-walled carbon nanotubes
NAA - Neutron activation analysis
NaCl - sodium chloride
NaMM - An antimony film modified sodium montmorillonite
NaOH - Sodium hydroxide
NPOE - nitrophenyl octyl ether
NPOE - 2-Nitrophenyl octyl ether
NSbFE-GRC - nafion coated-antimony film
OPFP - Ionic liquid n-octylpyridinum hexafluorophosphate
PA - polyacrylate
Pa-EME - parallel electromembrane extraction
PALME - parallel artificial liquid membrane microextraction
PANI - Polyaniline
Pb(II) - Lead
PbNPs-SH- - a lead nanoparticles-modified thiol-functionalized
xxxiii
PF/GCE - polysiloxane film GC electrode
PDMS - polydimethylsiloxane
PhACs - pharmaceutical active compounds
PMMA -
polypropylene membrane bonded in-between two poly-
methyl methacrylate
PP - Polypropylene
ppb - parts per billion
PPHF - Polypropylene hollow fiber
PPSD - Portable power supply device
Pt - platinum
PTFE - Polytetra fluoroethylene
PVDF - Polyvinlidine fluoride
RE - reference electrode
rGO - reduced graphene oxide
Ru(bpy)3]2+
- Tris(bipyridine)ruthenium(II)
SAMs - self-assembled monolayers
SbNP - Antimony nano particles
SbNP - antimony nanoparticles
SCP - Stripping chrono potentiometry
SDME - single-drop microextraction
SFFTCCV -
stripping fast Fourier transform continuous cyclic
voltammetry
SFOD-ME - Solidified floating organic drop - microextraction
SLM - supported liquid membrane
SMDE - static mercury drop electrode
SnNP - Tin nanoparticles
SPCE - screen printed carbon electrode
SPE - Screen printed electrode
SPME - solid-phase microextraction
SWAdSV - Square Wave Adsorptive Stripping Voltammetry
SWASV - Square Wave Anodic Stripping Voltammetry
SWCNT - single-wall carbon nanotubes
TBP - tributhylphosphate
xxxiv
UV - ultraviolet
WE - working electrode
WHO - World Health Organization
XRF - X-ray Fluorescence Spectrometry
xxxv
LIST OF SYMBOL
g - Gram
c - Concentration
Eacc - Deposition potential
Ef - Final potential
Ei - Initial potential
Ep - Peak potential
Hz - Hertz
Ip - Peak current
M - Molar
mM - Milimolar
mg - Milligram
min - Minutes
mL - Milliliter
mm - Millimeter
ppb - Part per billion
r2 - Correlation coefficient
mgL-1
- Milligram per liter
s - Seconds
tacc - Deposition time
V - Voltage
v/v - Volume per volume
ᵒ C - Degree Celsius
mA - Micro ampere
µL - Micro Liter
µgL-1
- Microgram per liter
µM - Micro molar
xxxvi
LIST OF APPENDICES
APPENDIX. TITLE PAGE
A Cr(VI) extraction efficiency using commercial DC
power supply and PSSD. The parameter involved
stipulated in Table 5.14.
242
B Pb(II) extraction efficiency using commercial DC
power supply and PSSD. The parameter involved
stipulated in Table 5.14.
243
C Simultaneous EME of Cr(VI), Pb(II) and Cd(II) using
PPSD-PVDF-NSbFE-GRC in Tap Water. The
parameter involved stipulated in Table 5.17.
244
D Simultaneous EME of Cr(VI), Pb(II) and Cd(II) using
PPSD-PVDF-NSbFE-GRC in River Water. The
parameter involved stipulated in Table 5.17.
245
E Simultaneous EME of (a) Cr(VI), (b) Pb(II) and (c)
Cd(II) using PPSD-PVDF-NSbFE-GRC in Industrial
waste water. The parameter involved stipulated in
Table 5.17.
246
F List of publication 247
G List of presentation 248
CHAPTER 1
INTRODUCTION
1.1 Background of Research
Water contamination is a worldwide problem which deserves attention due to
its negative impact on eco-system, human health as well as economic growth (Ben
Salem et al. 2014; Kim & Kang 2016). Heavy metals, as one of the pollutant
categories receive concern due to their high toxicity even at concentration as low as
parts per billion (ppb). Furthermore, the toxicity of heavy metals can be increased by
transformation to more toxic compounds due to their average long-life. Depending
on the type and speciation of heavy metal, it accumulates mainly in bones, brain,
kidney and muscles, which may cause serious illnesses such as anaemia, kidney
diseases, nervous disorders and sickness or even death among (Chen et al. 2012; Ben
Salem et al. 2014; D. Wang et al. 2016). In infant and children, exposure to heavy
metals above the standard level can result in delays in physical and mental
development (Y. Wang et al. 2016a; Liu et al. 2014; Xia et al. 2016). Therefore, the
determination of heavy metals has contributed to the awareness among human to
provide beneficial guidance on the physiological effect on body and environment.
There are numerous analytical techniques such as graphite furnace atomic
absorption spectroscopy (GF-AAS) (Dokpikul et al. 2018; Behbahani et al. 2015;
Cervantes et al. 2017; Schneider et al. 2017; Zhong et al. 2016), inductively coupled
plasma mass spectroscopy (ICP-MS) (Cervantes et al. 2017), neutron activation
analysis (NAA) (Namieśnik & Rabajczyk 2012) have been proposed for the
determination of heavy metal ions. These analytical techniques are advantages in
terms of sensitivity and multiple elemental analysis. However, these instruments
2
incur high cost. Nowadays, voltammetry techniques are much interested for the
determination of heavy metal ions, due to their highly sensitive, low cost, simple
operation and minimum use of reagents as well as suitable for speciation
measurements (Y. Wang et al. 2016b; Liu et al. 2014). However, heavy metal in
aquatic environmental samples are usually obtained in extreamely low level of
concentration such as sub-ppb or ppt. Moreover, aquatic environmental samples are
too complex for a direct measurement due to matrix interferences. These diffuculties
can be overcome by separating and preconcentrating the heavy metal ions prior to the
determination by any analytical techniques. Thus, there is a need to develop an
effective analytical method which allows separating, detecting and quantifying low
levels of heavy metal ions in aqueous environmental samples.
1.2 Problem Statement
Sampling, sample preparation, separation, detection and data analysis are the
most important steps in analytical process. When dealing with real sample matrix
samples each step equally important for collecting reproducible and reliable data.
Technology advancement in the field of separation and detection have introduced
sensitive and selective analytical instrument. However, real sample matrices can
reduce the quality of results. In modern analytical chemistry, there is a high demand
for accurate quantification of trace and ultra-trace of heavy metals from real aqueous
sample matrices. Hence, the determination of trace heavy metals depends on
instruments that capable of reaching detection limits as low as good selectivity.
However, to achieve this practice the number of interfering compounds must be kept
to a minimum to avoid severe matrix interference. In addition, there is also a demand
for pre-concentration of trace heavy metals to reach lower concentration limits for
sufficient detection. Recently, integrated and automated systems have been
increasing popular to reduce analysis time and labour. However, the demand for
highly time-efficient systems becomes challenging for separation of heavy metals
from real sample matrices.
3
The problems associated with heavy metals in the environment clearly
demand for an effective sustainable green analytical method which can
simultaneously pre-concentrate, separate, and detect with lower detection limits.
Several approaches such as ion-exchange separation (Aydin et al. 2011; Cechinel et
al. 2017), single-drop micro-extraction (SDME) (Manzoori et al. 2009), dispersive
liquid–liquid microextraction (DLLME) (Zhou et al. 2011; Dokpikul et al. 2018;
López-García et al. 2013), solid phase extraction (SPE) (Cervantes et al. 2017;
Pourreza & Naghdi 2014) and dispersive solid phase extraction (DSPE) (Fasih
Ramandi & Shemirani 2015; Behbahani et al. 2015) are available for the separation
and pre-concentration of heavy metal ions from aqueous environmental samples.
However, such procedures are time-consuming and prone to contamination.
Electromembrane extraction (EME) is a new concept of hollow fiber-liquid
phase microextraction (HF-LPME) in which an electrical field serves as a driving
force for the analytes to transfer between the donor phase (DP) and the supported
liquid membrane (SLM) and also between the SLM and the acceptor phase (AP)
(Fotouhi et al. 2011; Gjelstad et al. 2006). Interestingly, the combination of EME
and electrochemical studies has been popular in detecting pharmaceutical active
compounds (PhACs) such as sufentanil (Ahmar et al. 2013), morphine (Ahmar et al.
2014), dextromethorphan (Fakhari et al. 2014), diclofenic (Mofidi et al. 2017) and
clozapine (Rouhollahi et al. 2016) due to the unique opportunities of addressing the
challenges of green analytical chemistry by providing effective process of separating,
pre-concentrating and detecting while minimizing its environmental impact.
Studies published utilize modified solid electrodes such screen printed
(Fakhari et al. 2014; Ahmar et al. 2013) , carbon paste (Mofidi et al. 2017), and
glassy carbon (Kamyabi & Aghaei 2016a; Kamyabi & Aghaei 2016b) electrodes
where the solution from AP is collected using microsyringe and the pH of the
solution adjusted before the analyte can be detected using electrochemical
techniques. This is due to the low volume and inappropriate condition of aqueous AP
in EME such as pH and type of buffer solution, which is not suitable for
conventional electrochemical measurements. Therefore, the purpose of this research
is to develop an electrochemical electrode system with EME as a part of the
4
electrode that can directly separate, pre- concentrate and detect heavy metal ions in
real aqueous environmental samples.
1.3 Objectives of the Study
The objectives of this study are as follows:
a) To determine the potential complexing carriers using liquid-liquid extraction
technique for selected heavy metal ions;
b) To examine electrochemical response of the selected heavy metal ions under
conditions suitable for the acceptor phase;
c) To investigate the transport of the selected heavy metal ions across the EME
using PVDF flat sheet membrane; and
d) To develop and apply portable power supply device for EME system of
heavy metals in real samples such as tap, river, sea and industrial waste
water.
1.4 Scope of the Study
This study was conducted to investigate a simultaneous separation, pre-
concentration, and detection system for heavy metal ions such as Cr(VI), Pb(II), and
Cd(II) based on combination of voltammetry technique with EME. In achieving the
objectives of the research there are few important tasks need to be carried out and
five research scopes have been identified for accomplishing the objectives. The
scopes are:
1) Preliminary study was conducted by optimizing parameters for liquid –liquid
extraction (LLE) such as six (6) type of complexing carriers (4-cyanopyridine
(4-Cpy), 2-mercaptobenzothiazole (2-MBT), Tricaprylylmethyl ammonium
chloride (Aliquat 336), tributhylphosphate (TBP), di-2-ethylhexylphosphoric
5
acid (D2EHPA), trihexyl(tetradecyl)phosphonium chloride (Cyphos 101) four
(4) types of organic solvents (toluene, n-octanol, n-heptane and NPOE), pH
and type of stripping phase. This was investigated to understand the
complexing and stripping ability between carrier and heavy metal ions. The
selection of appropriate acceptor phase of heavy metal ion from carrier is very
crucial, as this aqueous phase condition was used to develop the
electrochemical detection for earlier mentioned heavy metal ions.
2) Heavy metal ions were detected using voltammetry technique based on the AP
of LLE by using solid electrode. The solid electrodes used in this study were
nafion coated-antimony film (NSbFE-GRC) and electrochemically reduced
graphene oxide (ErGO-GRC) modified on graphite reinforcement carbon as
substrate material. The ex-situ prepared NSbFE-GRC was used to selectively
detect Cr(VI) with the presence of DTPA using square wave adsorptive
stripping voltammetry (SWAdSV). NSbFE-GRC was also utilized for
simultaneous detection of Cd(II) and Pb(II) by using square wave anodic
stripping voltammetry (SWASV). Whereas, ErGO-GRC was used to
selectively detect Pb(II) using SWASV.
3) EME study was carried out by applying voltage using DC supply system with
the appropriate carrier in organic solvent supported by a fabricated PVDF
membrane which interposed between the aqueous sample matrix containing the
targeted heavy metal ions and acceptor phase. Polyvinylidene (PVDF)
membrane with different polymer percentage concentration (12%, 17% and
22%) fabricated and characterized to determine the functional groups, water
contact angles, thickness and porosity of membrane. In order to optimize the
EME, parameters such as the influence of membrane composition on extraction
voltage, extraction time, pH of the donor phase, stirring rate, carrier
concentration, organic solvent and agarose gel were assessed.
4) Portable power supply device (PPSD) was developed and used as portable
sampling system for selective and simultaneous EME to separate and pre-
6
concentrate Pb(II), Cd(II) and Cr(VI) in real samples such as tap, river, sea and
industrial waste water prior to detect using voltammetry techniques.
1.5 Significance of Study
The quick separation, pre-concentration and determination of trace and
ultratrace quantities of heavy metal in sample matrices with complex or variable
composition by simple method has become the major interest in analytical chemistry.
The construction of sensitive EME with GRC modified electrode have fast response,
linear dynamic range, low cost, environmentally friendly and ease for preparation
had been adding an advantage. Furthermore, this developed analytical technique was
able to comply with the principle of sustainable development and green chemistry.
Rapid growths of electromembrane studies demand the development of
portable power supply device (PPSD) with battery. A portable power supply device
(PPSD) with chargeable Li-ion battery have made on-site sampling or extraction.
This developed portable device might be a powerful tool with combination of EME
and voltammetry for simultaneous separation, pre-concentration and detection of
trace level Pb(II), Cd(II) and Cr(VI) present in real aqueous samples. This may be
open up possibilities of development of other technical configurations in the future
such as a portable EME or chronoamperometry system with software.
1.6 Novelty of Study
Till 2015, no research was carried out on the application of EME as a part of
the electrochemical electrode system that can directly separate, pre-concentrate and
detect heavy metal ions in real environmental samples. However, the combination of
these methods started to get attention for heavy metal ions such as Hg(II) (Kamyabi
& Aghaei 2016a) and As (III) (Kamyabi & Aghaei 2016b) after the publication by
Hamsawahini et al. (2015). Moreover, this is the first sudy that reported on the
7
development of a portable power supply device (PPSD) using chargable lithium ion
battery for on-site EME sampling.
1.7 Thesis Outline
This thesis consists of six chapters. Chapter 1 describes in detail the research
background, problem statement, objectives, scope as well as significance of the
study. Chapter 2 compiles the literature review of separation and pre-concentration
methods and voltammetry techniques for heavy metals. Chapter 3 describes
methodologies and applications that involve LLE, voltammetry, electromembrane
and portable power supply device development.
Chapter 4 describes the preliminary studies conducted to investigate potential
complexing carriers using liquid-liquid extraction technique for heavy metal ions
including Cr(VI), Pb(II), and Cd(II). ICPMS and AAS used to determine the
efficiency of metal extraction using complexing carriers. The results obtained used in
developing EME technique for respective metals. This chapter also discusses on
modified graphite reinforcement carbon electrodes in determination of Cr(VI),
Pb(II), and Cd(II) using voltammetry techniques. NSbFE-GRC and ErGO-GRC used
to determine the presence of Cr(VI), Pb(II), and Cd(II) in water samples such as
industrial waste water, river water, sea water and tap water.
Chapter 5 reports the development of EME using fabricated flat sheet PVDF
membrane for Cr(VI), Pb(II), and Cd(II). EME techniques combined voltammetry
techniques discussed in Chapter 4 which simultaneouly separate, pre-concentrate and
determine Cr(VI), Pb(II), and Cd(II) in water samples such as industrial waste water,
river water, sea water and tap water. Furthermore, this chapter describes the
developed portable power supply device for EME and its efficiency for Cr(VI),
Pb(II) and Cd(II) selective and simultaneous extraction in real samples such as tap,
river, sea and industrial waste water. Finally, Chapter 6 summarizes the overall
results obtained with suggestions for future work.
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