SEPARATION OF ARSENITE AND ARSENATE SPECIES FROM WATER BY

CHARGED ULTRAFILTRATION MEMBRANES

A THESIS SUBMITTED TO

THE GRADUATE SCHOOL OF NATURAL SCIENCES

OF

MIDDLE EAST TECHNICAL UNIVERSITY

BY

AYŞEGÜL SEZDİ

IN PARTIAL FULFILLMENT OF THE REQUIREMENTS

FOR

THE DEGREE OF MASTER OF SCIENCE

IN

CHEMICAL ENGINEERING

JUNE 2012

Approval of the thesis:

SEPARATION OF ARSENITE AND ARSENATE SPECIES

FROM WATER BY CHARGED ULTRAFILTRATION

MEMBRANES

submitted by AYŞEGÜL SEZDİ in partial fulfillment of the requirements for the

degree of Master of Science in Chemical Engineering Department, Middle East

Technical University by,

Prof. Dr. Canan Özgen ___________________

Dean, Graduate School of Natural and Applied Sciences

Prof. Dr. Deniz Üner ____________________

Head of Department, Chemical Engineering

Prof. Dr. A.Tülay Özbelge

Supervisor, Chemical Engineering Dept., METU ____________________

Examining Committee Members:

Prof. Dr. Hayrettin Yücel ____________________

Chemical Engineering Dept., METU

Prof. Dr. Tülay Özbelge ____________________

Chemical Engineering Dept., METU

Prof. Dr. Niyazi Bıçak ____________________

Chemistry Dept., ITU

Prof. Dr. O. Yavuz Ataman ____________________

Chemistry Dept.,METU

Assoc. Prof. Dr. Yusuf Uludağ ____________________

Chemical Engineering Dept., METU

Date: 15.06.2012

iii

I hereby declare that all information in this document has been obtained

and presented in accordance with academic rules ethical conduct. I also

declare that, as required by these rules and conduct, I have fully cited and

referenced all material and results that are not original to this work.

Name, Last name: Ayşegül Sezdi

Signature:

iv

ABSTRACT

SEPARATION OF ARSENITE AND ARSENATE SPECIES FROM

WATER BY CHARGED ULTRAFILTRATION MEMBRANES

Sezdi, Ayşegül

M.Sc. Department of Chemical Engineering

Supervisor: Prof. Dr. Tülay Özbelge

June 2012, 131 pages

Arsenic is found in drinking waters in many countries and since maximum allowable

concentration is as low as 10 µg/L, there are many research efforts to separate it from

water. Membrane methods are used more and more widely in separation operations

in recent years.

Arsenic is mainly present in water as arsenite [As(III)] and arsenate [As(V)]. As pH

of water changes, molecular formulas of As(III) and As(V) change. In this study, the

performance of different ultrafiltration membranes for arsenic removal from water

was investigated at different pH values, different feed concentrations and presence of

other anions (SO42-

, HPO42-

, NO3-, Cl

-). Donnan exclusion effect on separation was

discussed since distribution of arsenite and arsenate anions change in water due to

change in pH of the solution.

v

Experiments were conducted via batch and continuous modes. For continuous

ultrafiltration experiments, 30 kDa of polysulfone and 20 kDa of polyether sulfone

membranes were used. Batch ultrafiltration experiments were performed with the

usage of 3 kDa of regenerated cellulose membrane.

Higher retention values for As(V) were obtained compared to retention values of

As(III). When membranes’ performances were investigated, it was seen that highest

As(V) removal was observed with the usage of polysulfone membrane. Increase in

feed concentration and presence of other anions caused decrement in separation.

Hydride Generation Atomic Absorption Spectrometry was used to perform analyses.

Hydride generator part was designed, constructed and optimized to obtain reliable

and accurate absorbance values.

Keywords: Arsenic, Arsenic removal, Donnan exclusion principle, Ultrafiltration

method.

vi

ÖZ

İYONİK ULTRAFİLTRASYON MEMBRANLARI İLE ARSENİT VE

ARSENATIN SUDAN AYRILMASI

Sezdi, Ayşegül

Yüksek Lisans, Kimya Mühendisliği Bölümü

Tez Yöneticisi: Prof. Dr. Tülay Özbelge

Haziran 2012, 131 sayfa

Arsenik birçok ülkede içme sularında bulunduğundan ve müsaade edilebilir derişim

10 µg/L olduğundan, tüm dünyada sudan ayırma yöntemleri üzerinde çalışılmaktadır.

Membran yöntemleri ayırma işlemlerinde son yıllarda gittikçe yaygın olarak

kullanılmaktadır.

Arsenik suda ağırlıklı olarak arsenit [As(III)] ve arsenat [As(V)] formunda bulunur.

Suyun pHsi değiştikçe, As(III) ve As(V)’in molekül formülleri de değişmektedir. Bu

çalışmada, farklı ultrafiltrasyon membranlarının; farklı pH, başlangıç derişimleri ve

farklı iyonlar varlığında (SO42-

, HPO42-

, NO3-, Cl

-) arsenik giderimi üzerindeki

performansı araştırılmıştır. Arsenit ve arsenat iyonlarının suda bulunma dereceleri

çözeltinin pH değerine göre değiştiğinden ayırma üzerinde Donnan ayırma

prensibinin etkisi tartışılmıştır.

Deneyler, kesikli ve sürekli modlarda gerçekleştirilmiştir. Sürekli ultrafiltrasyon

deneylerinde, 30 kDa’luk polisulfon membranı ve 20 kDa’luk polieter sulfon

vii

membranı kullanılmıştır. Kesikli ultrafiltrasyon deneyleri 3 kDa’luk rejenere selüloz

membranı ile gerçekleştirilmiştir.

Sonuçlar incelendiğinde sudan As(V) gideriminin As(III) giderimine oranla daha

fazla olduğu gözlemlenmiştir. Membran performanslarına bakıldığında en yüksek

arsenik giderimi polisulfon membranı ile elde edilmiştir. Başlangıç derişiminde artış

ve diğer iyonların varlığı arsenik giderimi üzerinde olumsuz bir etki yaratmıştır.

Analizler, Hidrür Sistemli Atomik Absorpsiyon Spektrometri ile gerçekleştirilmiştir.

Hidrür kısmı tasarlanmış, kurulmuş ve güvenilir ve doğru sonuçlar elde edebilmek

için optimize edilmiştir.

Anahtar Kelimeler: Arsenik, Arsenik giderimi, Donnan ayırma prensibi,

Ultrafiltrasyon metodu.

viii

To my family

ix

ACKNOWLEDGEMENTS

I would like to express my deepest thanks to my supervisor Prof. Dr. Tülay Özbelge

for her continual advices, helpful corrections during my study. I also want to thank

Prof. Dr. Önder Özbelge for his helpful suggestions.

I would like to thank Prof. Dr. O. Yavuz Ataman for his enlightening advices.

I would like to thank Hasan Zerze and Saltuk Pirgalıoğlu for their support, continual

patience and the whole things that they showed or taught me throughout the study.

And also I want to thank my sweet lab mate Didem Polat for her greatest support and

sincere friendship.

I wish to express my sincere thanks to Emre Yılmaz for his different perspective

about life and unexpected comments what surprised me most of the time.

I also would like to thank Kerime Güney, Ass. Prof. Dr. Yasin Arslan and Serap

Tekin for their help and suggestions while guiding me how to use HG-AAS

instrument for arsenic determinations.

Finally, I am deeply grateful to my family for their invaluable support, endless love

and encouragement and to my fiancé Tolga for his endless patience and help

throughout my study.

x

TABLE OF CONTENTS

ABSTRACT……………………………………………………………………..…..iv

ÖZ…………………………………………………………………………….……..vi

ACKNOWLEDGEMENTS…………………………………………….…………...ix

TABLE OF CONTENTS……………………………………………...…………….x

LIST OF TABLES…………………………………………………………………xiii

LIST OF FIGURES…………………………………………………...…………….xv

CHAPTERS

1 INTRODUCTION…………………………………………………………1

2 LITERATURE SURVEY………………………………………………… 5

2.1 Arsenic Chemistry…………………………………………………... 5

2.2 Methods used for arsenic removal………………………………….. 8

2.2.1 Coagulation/precipitation…………………………………… 8

2.2.2 Adsorption…………………………………………………... 9

2.2.3 Ion-exchange……………………………………………….. 9

2.2.4 Membrane processes………………………………………. 10

3 EXPERIMENTAL……………………………………………………….. 15

3.1 Materials……………………………………………………………. 15

3.2 Experimental Methods………………………………………………16

3.2.1 Continuous Ultrafiltration Experiments……………………. 16

3.2.2 Batch Ultrafiltration Experiments………………………….. 17

3.2.3 Analysis by Hydride Generation Atomic Absorption

Spectrometry………………………………………………………. 18

3.2.3.1 Design and Construction…………………………. 18

3.2.3.2 Optimization of HG-AAS Instrument…………….20

3.2.3.2.1 Effect of HCl Concentration…………20

3.2.3.2.2 Effect of NaBH4 Concentration…….. 21

3.2.3.2.3 Effect of Argon Flow Rate………….. 22

xi

3.2.3.2.4 Effect of Reaction Coil Length……. 23

3.2.3.2.5 Effect of Stripping Coil Length…… 23

3.2.3.2.6 Effect of Sample Flow Rate and

NaBH4……………………………………………. 24

3.2.3.2.7 Calibration Curves………………… 26

3.2.3.2.8 Reduction of As (V) to As (III)…….28

4 RESULTS AND DISCUSSION…………………………………………. 30

4.1 Continuous Ultrafiltration Experiments……………………………. 31

4.1.1 Experiments Conducted with Polysulfone (PS) Membrane...31

4.1.1.1 Effect of pH on separation of As(III)……………. 31

4.1.1.2 Effect of pH on separation of As(V)…………….. 33

4.1.1.3 Effect of Increasing Feed Concentration of As(V) on

Retention………………………………………………… 37

4.1.1.4 Effect of Other Anions on Retention……………. 39

4.1.2 Experiments Conducted with Polyether Sulfone (PES)

Membrane…………………………………………………………... 41

4.2 Batch Ultrafiltration Experiments………………………………….. 44

4.2.1 Experiments Conducted with As(III) with Regenerated

Cellulose (RC) Membrane………………………………………….. 44

4.2.2 Experiments Conducted with As(V) with Regenerated

Cellulose (RC) Membrane………………………………………….. 45

5 CONCLUSIONS…………………………………………………………. 47

6 RECOMMENDATIONS………………………………………………… 49

REFERENCES…………………………………………………………………….. 50

APPENDICIES…………………………………………………………………….. 55

A ANALYSIS DATA FOR OPTIMIZATION OF HG-AAS……………… 55

B RESULTS OF THE EXPERIMENTS OF AS(III) AND AS(V)

CONDUCTED WITH PS, PES, RC MEMBRANES………………………... 59

B.1 Results of As(III) experiments with PS

membrane…………..……………………………………………………...59

B.2 Results of As(V) experiments with PS membrane……………………61

B.3 Results of Increasing As(V) Concentration on Retention with PS

membrane………………………………………………………………….62

xii

B.4 Results of Other Anions on Retention with PS membrane…………...64

B.5 Results of As(V) experiments with PES membrane.............................65

B.6 Results of As(III) experiments with RC membrane.………………….67

B.7 Results of As(V) experiments with RC membrane...............................68

C ANALYSIS DATA OF AS(III) AND AS(V) EXPERIMENTS

CONDUCTED WITH PS, PES AND RC MEMBRANES……………….…..69

C.1 Detailed Procedures of Analyses for the Experiments conducted with

As(III)……………………………………………………………….……..69

C.2 Detailed Procedures of Analyses for the Experiments conducted with

As(V)………………………………………………………………………70

C.3 Analysis results for As(III) experiments conducted with PS

membrane………………………………………………………………….71

C.4 Analysis results for As(V) experiments conducted with PS

membrane………………………………………………………………….82

C.5 Analysis Results of the Experiments conducted with different As(V)

concentrations with PS membrane……………………...……..…………..92

C.6 Analysis Results of the As(V) Experiments conducted with the presence

of different anions with PS membrane……………………………….…..100

C.7 Analysis results for As(V) experiments conducted with PES

membrane…………………………………………………...……………112

C.8 Analysis results for As(III) experiments conducted with RC

membrane………………………………………………………………...120

C.9 Analysis results for As(V) experiments conducted with RC

membrane………………………………………………………………...126

xiii

LIST OF TABLES

TABLES

Table 2.1: Pore size and applied pressure for membrane processes……….……….10

Table 3.1: Calibration data for lower concentrations……………………….………26

Table 3.2: Calibration data for higher concentrations................................................27

Table 3.3: Calibration data for standards reduced from As(V) to As(III)………….29

Table 4.1: Retention values obtained for As(III) at pH=11.0 and at T=25 °C with PS

membrane. (ΔP=200 kPa)………………………………………….………………..31

Table 4.2: Average retention values for As(III) at pH values between 6-11 with PS

membrane…………………………………………………………………….……...32

Table 4.3: Retention values obtained for As(V) at pH=11.0 at T=25 °C with PS

membrane (ΔP=200 kPa)…………………………………………………………....33

Table 4.4: Average retention values for As(V) at pH values between 6-11 with PS

membrane…………………………………………………………………….……...34

Table 4.5: Average retention values for As (III) and As (V) at pH values between 6-

11 with PS membrane……………………………………………………………….35

Table 4.6: Retention values obtained for CAs(V) = 30 μg/L (ΔP=200 kPa)…………37

Table 4.7: Average retention values for different As(V) concentrations………….. 38

Table 4.8: Results of 2.15x10-7

M of As(V) experiments conducted with 3.125x10-4

M SO42-

presence at pH=10.0 (ΔP=200 kPa)………………………………………. 39

Table 4.9: Average retention values of As(V) with and without anions at pH=10 at

T=25 °C with PS membrane (ΔP=200 kPa)……………………………………….. 40

Table 4.10: Results of 30 μg/L of As(V) experiments conducted at pH=10.0 with

PES membrane (ΔP=200 kPa)………………………………………………………41

xiv

Table 4.11: Average retention values for As(V) at pH values between 6-11 with PES

membrane…………………………………………………………………………....42

Table 4.12: Results of As(III) experiments conducted at pH=7.0 with RC membrane

(ΔP=100 kPa) (Initial concentration of feed: 29.2 μg/L)…………………………... 44

Table 4.13: Comparison of retention values of As(III) experiments conducted at pH

values between 7-10 with RC membrane…………………………………………...45

Table 4.14: Results of As(V) experiments conducted at pH=8.0 with RC membrane

(ΔP=100 kPa) (Initial concentration: 26.7 μg/L)…………………………………... 45

Table 4.15: Comparison of retention values of As(V) experiments conducted at pH

values between 7-10………………………………………………………………... 46

xv

LIST OF FIGURES

FIGURES

Figure 2.1: Molecular structures of (a) arsenic acid and (b) arsenous acid…………..5

Figure 2.2: Eh-pH diagram of aqueous As species…………………………….…….6

Figure 2.3: Distribution of (a) Arsenic (III) and (b) Arsenic (V) species as a function

of pH………………………………………………………………………………… 7

Figure 3.1 Continuous Ultrafiltration set-up………………………………………..17

Figure 3.2: Batch Ultrafiltration set-up…………………………………..………….18

Figure 3.3: Hydride Generator for Arsenic analysis……………………….………..19

Figure 3.4: Absorbance values for 100 μg/L As solution at different HCl

concentrations………………………………………………………..……………...20

Figure 3.5: Absorbance values for 100 μg/L As solution at different NaBH4

concentrations……………………………………………………………………….21

Figure 3.6: Absorbance values for 100 μg/L As solution at different argon flow

rates…………………………………………………………………..……………...22

Figure 3.7: Absorbance values for 100 μg/L As solution at different reaction coil

lengths………………………………………………………………...……………..23

Figure 3.8: Absorbance values for 100 μg/L As solution at different stripping coil

lengths………………………………………………………………………...……..24

Figure 3.9: Absorbance values for 100 μg/L As solution at different sample flow

rates………………………………………………………………………………….25

Figure 3.10: Calibration curve for concentrations lower than 10 μg/L….………….27

Figure 3.11: Calibration curve for concentrations higher than 10 μg/L…………….28

Figure 3.12: Calibration curve for standards reduced from As (V) to As (III)…….29

xvi

Figure 4.1: The retention values obtained for As (III) at pH values between 6-11 with

PS membrane………………………………………………………………………. 32

Figure 4.2: The retention values obtained for As (V) at pH values between 6-11 with

PS membrane………………………………………………………………………..34

Figure 4.3: Comparison of the retention values for As(III) and As(V) at pH values

between 6-11 with PS membrane…………………………………………………... 36

Figure 4.4: Effect of increasing As(V) concentration on retention at pH=10.0 at

T=25 °C with PS membrane (ΔP=200 kPa)……………………………………….. 38

Figure 4.5: Retention values of 2.15x10-7

M of As(V) experiments conducted with

3.125x10-4

M of anions at pH=10.0 at T=25 °C with PS membrane (ΔP=200 kPa)..40

Figure 4.6: The retention values obtained for As (V) at pH values between 6-11 with

PES membrane……………………………………………………………………... 42

Figure 4.7: Comparison of the retention values for As(V) at different pH values with

PS and PES membranes……………………………………………………………. 43

Figure 4.8: Comparison of the retention values for As(III) and As(V) at pH values

between 7-10 with RC membrane………………………………………………….. 46

1

CHAPTER 1

INTRODUCTION

Water has a very important role for life on earth. Recently, increase in population

growth, surface water pollution, and climate change together cause decline in fresh

water sources. Decrease in water availability is likely to cause some health problems

due to decreased food production and less water for safe drinking and domestic uses

(Kanae, 2009).

Recently, cleaning and purification of water sources which contain hazardous

chemicals have become very important due to the decrease in supplies for high-

quality water. Among the hazardous chemicals present in water, arsenic has been

reported as one of the most widespread contaminant in the water sources worldwide.

The reasons of presence of arsenic in water and in the environment are; arsenic-rich

rocks and sediments through which the water has filtered, volcanic deposits,

dissolved minerals which contain arsenic as a constituent, the wastes due to mining

or industrial activity in some areas like; smelting of metal ores and use of arsenical

pesticides used in agriculture (Choong et al., 2007; Jain et al., 2000).

Arsenic is claimed to be very hazardous to human health. Various researches were

carried out to investigate the effects of arsenic on human health (Kapaj et al., 2006;

Mazumder et al., 1988; Ratnaike, 2003) Arsenic can affect the human health through

ingestion, inhalation or skin adsorption. However, ingestion is the most hazardous

one to human health. Health problems because of the ingestion of arsenic in water

are; skin lesions, internal malignancies, neurological effects, hypertension, peripheral

vascular diseases, cardiovascular disease, respiratory diseases, diabetes mellitus.

2

Also, arsenic digestion causes mainly skin, lung, bladder, kidney, liver, and uterus

cancers (Yoshida et al., 2004). To avoid these hazardous effects of arsenic on human

health, the maximum concentration of arsenic is advised as 10 µg/L in public water

systems by World Health Organization (WHO) in 1993 (Smedley et al., 2002).

van Halem et al. (2009) reported the countries which contain arsenic in their water

sources above the permissible value of 10 µg/L. Dissolution of sediments in

Bangladesh, Vietnam and Cambodia is the main reason of arsenic contamination in

the water supplies. There is arsenic contamination in Italy and Mexico due to

dissolution of minerals. The water sources of Chile and Argentina contain arsenic

because of volcanic activities in Andes Mountains. Canada, Germany, Ghana,

Greece, Mexico, South Africa, Thailand, UK, USA, Zimbabwe, Poland, Korea and

Brazil are the countries affected by arsenic contamination due to mining activities.

Turkey is one of the countries affected by arsenic in the water sources. In the study

of Doğan et al. (2005), it was determined that groundwater and drinking-water wells

in Kütahya contain arsenic above permissible value of 10 µg/L. Arsenic

concentrations in Igdeköy village and in Dulkadir village were specified as 8.9-9.3

mg/L and 0.3-0.5 mg/L, respectively, and over thirty people were suffered from skin

disorders due to arsenic ingestion. It was emphasized that in the future, consumption

of water sources containing arsenic might increase the risk of cancers of the skin

and internal organs and these diseases might become the most important health

problem in these regions of Kütahya.

Kavcar et al. (2009) studied the presence of hazardous chemicals in drinking water in

İzmir. Drinking water samples were collected from 100 houses which were chosen

from different regions of İzmir and it was found that arsenic concentration exceeded

the standard level of 10 µg/L in 20% of these water samples.

Altaş et al. (2011) investigated the arsenic presence in Aksaray by collecting and

analyzing water samples from 62 different places and they concluded that 27 of these

stations contained arsenic concentration above 10 µg/L. The values were ranged

between 10.3 and 201 µg/L. They also discussed the method used currently for the

3

water treatment including the units of aeration, coagulation/flocculation, filtration,

and disinfection. It was observed that arsenic concentrations decreased from 51.7 to

13.6 µg/L by using this water treatment plant in Mamasun Dam, the most important

source in Aksaray, and it was concluded that the current water treatment plant was

not sufficient to decrease arsenic concentration below 10 µg/L.

It became crucial to separate arsenic from water because of its presence in public

water supplies excessively and its serious negative effects to human health.

Coagulation/precipitation, adsorption, ion-exchange and membrane processes are the

major methods used for arsenic separation. But there are some disadvantages of these

methods. The production of by products, the release of taste and odor compounds

and sludge disposal related problems are considered as the main limitations of

coagulation/precipitation method. The disadvantages of adsorption method to

separate arsenic from water are listed as; the disposal of the spent media and the

wastewater produced in the course of regeneration/cleaning of the column. Also,

replacing the medium after a few reuses is required because of irreversible fouling

and excessive attrition when adsorption method is used (Ng et al., 2004). Ion-

exchange method has limitations as; difficulty to apply for large capacities due to its

higher treatment cost compared to other methods, requirement of

regeneration/replacement of the medium when the medium is exhausted and the

restriction of arsenic removal by the presence of other anions such as sulfate since

the method is basically about exchanging of ions (Wang et al., 2000).

By using membrane separation processes, lowering arsenic level in water could be

achieved. The main advantages of membrane technology are considered as;

requirements for operation and maintenance are minimal and there is no need to add

chemicals. Therefore, several studies have been made for determination of the

efficiency of arsenic removal by microfiltration, ultrafiltration, nanofiltration, and

reverse osmosis which are all pressure driven membrane processes.

Nanofiltration and reverse osmosis operate at high pressures when compared to

ultrafiltration and microfiltration. High arsenic removal efficiency is achieved by

reverse osmosis and nanofiltration. However, increase in energy required and

4

accordingly higher cost are the main disadvantages of reverse osmosis and

nanofiltration processes. On the other hand, higher water recovery is provided with

the use of ultrafiltration and microfiltration. Also, high fluxes can be obtained at low

pressures. These advantages make ultrafiltration and microfiltration attractive as low-

energy methods for separating arsenic from water. However, microfiltration is not

preferable since its pore size is too large for removing arsenic in water (Pirnie, 2000).

In this study, the applicability of different membranes for arsenic removal from water

was investigated. Effect of pH change, arsenic speciation, different concentrations of

As(V) and other anions were discussed due to the results.

Analyses were carried out via Hydride Generation Atomic Absorption Spectrometry.

Firstly, hydride generator part was designed, constructed and optimized. Then,

analyses of samples obtained from ultrafiltration experiments were performed.

5

CHAPTER 2

LITERATURE SURVEY

2.1 Arsenic Chemistry

Arsenic (As) is a chemical element with atomic number of 33 and atomic mass of

74.92 g/mol. It has the group 15, period 4 and block p of periodic chart. Arsenic

occurs naturally in water. The permissible limit of presence of arsenic in water is

specified as 10 µg/L.

Organic and inorganic forms of arsenic can occur in water, but in general the amount

of organic arsenic is insignificant when compared to inorganic arsenic. Arsenic

occurs mainly in its inorganic forms in natural waters with the valence states of

As(III) and As(V) (Smedley et al., 2002). Presence of arsenic in water threatens

human health. As(III) is more toxic to human health than As(V) species (Mushak,

1985). Arsenite [As(III)] species occur as arsenous acid (As(OH)3) and ions

(H2AsO3−, HAsO3

2−, and AsO3

3−). Arsenate [As(V)] species occur as arsenic acid

(H3AsO4) and arsenate ions (H2AsO4−, HAsO4

2−, AsO4

3−). In Figure 2.1, molecular

structures of arsenous acid and arsenic acid are represented.

Figure 2.1: Molecular structures of (a) arsenic acid and (b) arsenous acid

6

Distribution of As(III) and As(V) species in water is dependent mainly on pH and

redox potential (Eh) (Smedley et al., 2002). Under oxidizing conditions, As(V)

species occur in water, while As(III) species is dominant under reducing conditions.

As pH changes, forms of arsenic species also change.

Figure 2.2: Eh-pH diagram of aqueous As species.

At neutral pH, As(III) exists mostly in the form of As(OH)3 while H2AsO3−

is present

in a small fraction less than 1.0 %. When pH dependence of As(V) is observed, it can

be seen that ions of HAsO42−

and H2AsO4− occur almost in same concentrations at

neutral pH (Sharma et al., 2009).

Dissociation of As(III) species can be observed as the following;

As(OH)3 ↔ As(OH)2O- + H

+ pKa1= 9.2 (1)

As(OH)2O- ↔ As(OH)O2

2- + H

+ pKa2=12.1 (2)

As(OH)O22-

↔ AsO33-

+ H+

pKa3=12.7 (3)

7

Dissociation of As(V) species are shown as follows;

AsO(OH)3 ↔ AsO2(OH)2- + H

+ pKa1= 2.3 (4)

AsO2(OH)2- ↔ AsO3(OH)

2- + H

+ pKa2= 6.8 (5)

AsO3(OH)2-

↔ AsO43-

+ H+

pKa3= 11.6 (6)

Figure 2.3: Distribution of (a) Arsenic (III) and (b) Arsenic (V) species as a function

of pH.

8

2.2 Methods used for arsenic removal

Removing arsenic from water is studied in years. There is a significant technological

development in arsenic removal from water supplies. Recently, researchers focus on

developing more efficient removal technology to obey the permissible limit

concentration of arsenic in water. Also, arsenic removal may be the only way in

many arsenic affected water sources because of lack of any other alternative water

sources. Additionally, the cost of the technology has an important effect on selection

of technology to be used (Ahmed, 2001). Some other requirements should be also

considered and provided for arsenic removal technology such as; technology should

be stiff, environmentally friendly, have the adequate capacity to provide necessary

water to public supply systems uninterruptedly, and meet the requirement of water

quality standards (Duarte et al., 2009).

There are several technologies to separate arsenic from water to meet the specified

water quality standards. The conventional technologies used are listed as;

coagulation/precipitation, adsorption, ion-exchange and membrane processes.

Recently, providing higher arsenic removal efficiencies, minimizing the capital and

operation costs of the systems, resolution of maintenance problems, controlling and

managing the sludge and arsenic concentrates are the main concerns to improve the

conventional technologies (Ahmed, 2001).

2.2.1 Coagulation/precipitation

There are several studies about removing arsenic from water by using

coagulation/precipitation method. Alum (Al2(SO4)3), ferric chloride (FeCl3), or

ferrous sulphate (FeSO4) are the main coagulants used for this method. Removal is

achieved by the adsorption of arsenic species onto the just precipitated Al(OH)3 and

Fe(OH)3 particles. Iron-containing coagulants give better removal efficiencies when

compared to aluminium containing coagulants. (Höll, 2010). However, discharging

of large volumes of sludge containing arsenic is an important limitation of this

method. When it is applied to large-scaled treatment processes, handling of this

sludge is a major problem (Höll, 2010).

9

2.2.2 Adsorption

Arsenic removal by using adsorption method is discussed in many studies in years.

Different adsorbents such as; activated carbon, iron compounds, activated alumina

are used. Adsorbents must be easily available, regenerated quickly and inexpensive.

Activated carbon is the one used mostly for removal of arsenic. Loading capacity of

carbon is low for arsenic. When activated carbon is pre-treated with Cu(II) solution,

it is observed that the removal efficiency of arsenic increases due to formation of

insoluble compounds composed of arsenic and metal ions and it is concluded that

pre-treatment of activated carbon is necessary to obtain efficient removal of arsenic

(Lorenzen et al., 1994). When activated red mud is used as adsorbent, it is observed

that higher arsenic removal values can be obtained but the process for arsenic

removal is pH dependent (Altundoğan et al., 2002). In addition to individual

limitations of adsorbents, there are common limitations arising with the usage of

adsorption method such as the disposal of the spent media, the wastewater produced

during regeneration/cleaning of the column and the requirement of replacing the

medium after a few reuses (Ng et al., 2004).

2.2.3 Ion-exchange

Ion-exchange process is another method used for arsenic removal from water.

Strong-base anion and weak-base anion are the classes of anion exchange resins

used. Generally, strong-base anion resins are preferred for higher arsenic removal

because of their effectiveness over a larger pH range. However, it is observed that in

the presence of sulphate, chloride and other anions, ion exchange method is

ineffective and the removal efficiency of arsenic decreases. Because these anions

may compete with arsenic to hold onto the ion exchange resin due to the order of

preference for exchange. Also, resin must be replaced or regenerated after all

available sites on the resin are exhausted (Wang et al., 2000).

In addition to conventional technologies for arsenic removal, there are some

researches carried out to develop alternative methods. Most of these new

technologies are based on modifying conventional technologies. For instance, arsenic

can be removed with the usage of iron oxide coated sand in fixed bed reactor.

10

Method is based on exchanging of arsenic ions with hydroxides. However, the bed

must be regenerated or replaced when it is exhausted and presence of dissolved

organic matter in water affects the arsenic removal negatively (Pirnie, 2000).

2.2.4 Membrane processes

Membranes are widely used in separation processes. Basically membranes act as a

selective barrier and only allow particular components pass through while the other

components are retained by the membrane when a driving force is applied.

There are pressure driven membranes which require pressure difference as a driving

force for passages of specific component through membrane. Pressure driven

membranes can be divided into four categories which are microfiltration,

ultrafiltration, nanofiltration and reverse osmosis. Microfiltration and ultrafiltration

are classified as low pressure membranes, while nanofiltration and reverse osmosis

are considered as high pressure membranes. Low and high pressure membranes have

different pore sizes. Basically, pore sizes of low pressure membranes are relatively

larger when they are compared to pore sizes of high pressure membranes.

Low and high pressure membranes operate at different pressure ranges. The pore

sizes and applied pressure differences are listed in Table 2.1.

Table 2.1: Pore size and applied pressure for membrane processes (Madaeni, 1999).

RO NF UF MF

Pore size Dense 2-5 nm 5-20 nm 20 nm-1 µm

Applied

pressure (atm) 30-150 5-20 2-7 1-3

The oldest membrane technology is reverse osmosis. It is specified that high removal

efficiencies of arsenic are obtained, when reverse osmosis is applied. However,

application of reverse osmosis is limited especially in poor countries because of high

energy requirement, since they operate at high pressure ranges. Additionally,

presence of other constituents such as iron, manganese, silica in water have negative

11

effects on removing efficiency of arsenic, since they can also be retained by reverse

osmosis (Pirnie, 2000).

Another high pressure membrane technology is nanofiltration method. It is also

effective for removing arsenic from water. Its energy consumption is lower than

reverse osmosis process, since generally lower pressures are applied. However, Sato

et al. (2002) investigated the effect of pressure on arsenic removal by nanofiltration

processes and concluded that as the pressure applied increases, removal efficiency of

arsenic species also increases, which makes nanofiltration process difficult to apply.

Microfiltration method is one of the low pressure processes. This method can be

effective only for removing particulate forms of arsenic because of larger pore sizes

of microfiltration membranes. Microfiltration combined with coagulation processes

is considered as an alternative way to increase removal efficiency of total arsenic

since presence of particulate forms of arsenic is not too much in waters and removal

of dissolved or colloidal arsenic cannot be achieved only by microfiltration. Arsenic

can be adsorbed onto the ferric complex when ferric chloride and ferric sulphate are

used as coagulants. After coagulation is completed, this water is filtered by using

microfiltration. A significant increase is observed by this combined method when

compared to results obtained from microfiltration process only without coagulation

(Pirnie, 2000).

Ultrafiltration is another low pressure membrane process. High fluxes can be

obtained with usage of ultrafiltration membrane. However, it may not be an effective

method to remove total arsenic from water (Weng et al., 2005; Hsieh et al., 2008). To

get higher removal results, complexation enhanced ultrafiltration processes can be

used. The main idea of this separation is attaching small molecules to larger species.

This provides to use a membrane with large pores to separate small molecules. So

low-energy method for separating arsenic from water can be achieved. Complexation

enhanced ultrafiltration is classified due to its complexation agent used such as

micellar enhanced ultrafiltration and polymer enhanced ultrafiltration.

12

Micellar enhanced ultrafiltration is based on introducing a certain amount of cationic

surfactant to feed water and bounding arsenic ions to these surfactants. By this way,

arsenic attached to the surfactant cannot pass through the membrane and removal is

achieved. Iqbal et al. (2007) studied the separation of arsenate from water using four

different cationic surfactant micelles via ultrafiltration method and concluded that

highest removal efficiency (96%) was obtained by using hexadecylpyridinium

chloride (CPC). However, micellar enhanced ultrafiltration has some disadvantages.

In the study of Fillipi et al. (1999), these disadvantages are listed as limitations due to

recovering of surfactants and the leakage of the surfactant through the ultrafiltration

membrane to the permeate stream.

Polymer enhanced ultrafiltration is another type of complexation enhanced

ultrafiltration which is based on attaching the target molecule to water soluble

polymers to form macromolecular complexes. So, only low molecular mass

compounds are permitted to pass through from the membrane. This provides

separation of target ions during the ultrafiltration process. It requires low energy as

well and the complexation of ions occurs in homogeneous phase so that problems

occurring with working multiple phases are eliminated and not observed (Landaburu-

Aguirre et al., 2006). In polymer enhanced ultrafiltration, it is important to select

suitable water-soluble polymeric complexation agent for targeted ions. This method

is used for the separation of heavy metals and metalloids in studies (Müslehiddinoğlu

et al., 1998; Islamoğlu, 2002; Camarillo et al., 2012) In the study of Uludag et al.

(1997), polyethylenimine was used as a polymeric complexation agent for mercury

and continuous ultrafiltration was applied and high removal efficiencies were

obtained.

Recently, several studies for removing arsenic with the usage of polymer enhanced

ultrafiltration process were carried out. It is aimed that removal efficiencies can be

increased by synthesizing suitable polymer for effective arsenic binding. In the study

of Rivas et al. (2007), the properties of Poly(acrylic acid)s with different tin

contents as a water-soluble metal–polymer to retain As(III) from aqueous

solution were investigated in a batch ultrafiltration system. It was observed that

As(III) could be removed from water effectively and the highest retention was

13

obtained when poly(acrylic acid) had 10 wt % of tin. Rivas et al. (2009) investigated

As(V) removal efficiency by using the poly[2-(acryloyloxy)

ethyltrimethylammonium chloride] and poly (vinylbenzyltrimethylammonium

chloride) in a batch ultrafiltration system at different pH values, and concluded that

more efficient retention of As(V) species at higher pH values of 8 and 6, rather than

4, was observed.

In addition to complexation enhanced ultrafiltration processes, an alternative way to

remove arsenic from water is suggested which is based on removing arsenic species

by electrostatic repulsion when negatively charged membranes are used. When

anionic arsenic species are processed in an ultrafiltration system which has

negatively charged membranes, the arsenic species which have same charge with

membrane may not pass through the membrane. This principle is called Donnan

exclusion principle. In the study of Brandhuber et al. (2001), arsenic removal by

negatively charged sulfonated polysulfone ultrafiltration membrane was investigated

and they concluded that arsenic removal efficiency increased as pH of solution

increased; because an increment in pH led an increment in the charge of arsenic

species which can be seen in Figure 2.2 and charge of membrane.

In study of Yoon et al. (2009), negatively charged RO, NF and UF membranes were

used to remove arsenic. The highest removals of As(V) and As(III) were obtained

with the usage of RO membrane as expected. For NF and UF membranes, it was

observed that efficient removals could be obtained for As(V) whereas these

membranes were inefficient to remove As(III).

Seidel et al. (2001) studied role of charge (Donnan) exclusion in removal of arsenic

from water by a negatively charged, loose, sulfonated polysulfone nanofiltration

membrane. Firstly, membrane charge was investigated and it was observed that

charge of membrane was increasing as pH of solution increasing. Experiments were

conducted with both As(III) and As(V) species. For As(V) retention value was

obtained as 85 % at pH=8.5. On the other hand, retention value less than 10 % was

observed for As(III). A decrease of nearly 5% in retention value was obtained for

As(V) with the presence of NaCl salt.

14

Lohokare et al. (2008) studied As(V) removal from water by using polyacrylonitrile

(PAN)-based negatively charged UF membrane. Membrane was treated with sodium

hydroxide and formation of carboxylate groups (COO-) was provided. These

carboxylate groups made the membrane negatively charged and an effective arsenic

removal was achieved. Higher removal efficiencies were observed at higher pH

values (pH ≥ 7).

It seems that most of the studies to separate arsenic from aqueous solutions by

membrane methods are either in batch mode or do not cover the experimental

parameters in a comprehensive manner. Batch studies only give an indication for a

possible separation with the pH, membrane and the polymer; but they do not give a

good understanding of how those parameters will work out in the continuous

applications. The studies made in the continuous mode for charged membranes need

to be extended to a wider pH range with various kinds of membranes. Therefore, this

study is intended to produce experimental data in a wide pH range with various kinds

of membranes at continuous mode.

15

CHAPTER 3

EXPERIMENTAL

3.1 Materials

Standard solutions of inorganic As (III) were prepared by using % 99.99 purity of

sodium (meta) arsenite (AsNaO2) (Aldrich) which has a molecular weight of 129.91

g/mol. Standard solutions of inorganic As (V) were prepared by using sodium

arsenate dibasic heptahydrate (Na2HAsO4•7H2O) (Aldrich) which has a molecular

weight of 312.02 g/mol. Then, these stock solutions were diluted to the desired

concentrations to be used in the ultrafiltration experiments.

For analyses of the samples obtained from ultrafiltration experiments, sodium

borohydride (NaBH4) powder (J.T. Baker), sodium hydroxide (NaOH) pellets (J.T.

Baker) and 37-38 % of hydrochloric acid solution (Merck) were used.

For reduction of As (V) to As (III), potassium iodide (KI) powder (Merck) and

ascorbic acid (Merck) were used.

For experiments conducted to observe anion competition with arsenic, sodium nitrate

(NaNO3) (Merck), sodium sulphate (Na2SO4) (J.T. Baker) and sodium chloride

(NaCl) (J.T. Baker) and Na2HPO4 (Acros) were used.

In the continuous ultrafiltration experiments; polysulfone membrane (PS) (Osmonics

Sepa YMERSP1905) with a molecular weight cut-off of 30000 Da and polyether

16

sulfone membrane (PES) (Osmonics SEPA YMPWSP1905) with a molecular weight

cut-off of 20000 Da were used.

For the batch ultrafiltration experiments, regenerated cellulose (RC) membrane

(Amicon-Millipore) with a molecular weight cut-off of 3000 Da was used.

For the continuous ultrafiltration experiments, SEPA CF membrane cell system was

used. This system has 155 cm2

of effective membrane area. The flow diagram of the

system is shown in Figure 3.1.

For the batch ultrafiltration experiments, Amicon-Millipore Model 8050 membrane

cell system was used. Its effective membrane area is 41.8 cm2. The flow diagram of

the system is illustrated in Figure 3.2.

3.2 Experimental Methods

3.2.1 Continuous Ultrafiltration Experiments

Firstly, feed solutions of Arsenic (III) and Arsenic (V) were prepared and pH of the

solution was adjusted. Then, the feed vessel containing the feed solution was placed

on a magnetic stirrer. By this way, solution was agitated during the whole

experiment.

The temperature of the solution was adjusted by a magnetic stirrer and then the

solution was introduced into the membrane cell by a pump which was operated at

3000 rpm. The pressure of cell was adjusted to 400 kPa by pressurized nitrogen and

the pressure of feed side of the membrane was adjusted to 200 kPa by using a back

pressure valve. By applying this pressure difference in retentate stream, the solution

was forced to pass across the membrane and permeate solution was collected from

permeate stream.

The duration of the experiments was 4 h. Samples were taken from the feed vessel

and permeate stream at every hour of the experiment. Permeate and retentate streams

were returned back to feed vessel to minimize the possibility of the change in

17

concentration of feed solutions during the experiments. In the beginning and at the

end of the experiments, the membrane cell system was washed regularly with pure

water to clean the system and the membrane.

Figure 3.1: Continuous Ultrafiltration set-up: 1- Feed Vessel, 2- pH-meter, 3- Pump,

4- Cell Body, 5- Membrane, 6- Pressure Gauge, 7- Cell Holder, 8- Pressurized

Nitrogen, 9- Back-Pressure Valve, 10- Permeate Stream, 11- Retentate Stream, 12-

Magnetic Stirrer.

3.2.2 Batch Ultrafiltration Experiments

Feed solutions were prepared by following the same procedure described in

continuous ultrafiltration experiments. After adjusting the pH of solutions, the cell

body containing feed solution was placed on a magnetic stirrer. The solution was

agitated during the whole experiment. The system was pressurized by pressurized

nitrogen. Samples were taken from permeate stream to analyze by using Hydride

Generation Atomic Absorption Spectrometry.

18

Figure 3.2: Batch Ultrafiltration set-up: 1- Pressurized Nitrogen, 2- Magnetic Stirrer,

3- Permeate stream, 4- Membrane, 5- Stirrer bar, 6- Cell Body, 7- Stand assembly.

3.2.3 Analysis by Hydride Generation Atomic Absorption Spectrometry

Analyses of the arsenic samples were performed by a Hydride Generation Atomic

Absorption Spectrometer (HG-AAS). The model of Atomic Absorption Spectrometer

was Shimadzu AA 6300, and acetylene/air was used as fuel.

Hydride generator part was designed and constructed for this study by a set of

equipment, and then the parameters of that constructed part that would affect the

absorbance values were optimized.

3.2.3.1 Design and construction

There are various studies in literature about designing and optimizing hydride

generator (Marshall et al., 1998; Sturman, 1985; Lampugnani et al., 2003). The

idea of forming hydride is basically based on reaction of an acidified sample solution

with sodium borohydride solution. Then, absorbance values read after products are

stripped to gas liquid separator. In this study, hydride generator part of the instrument

was designed and constructed by using two peristaltic pumps, PTFE

(Polytetrafluoroethylene) microbore tubing, Tygon Lab Tubing, a Connector "Tee"

to connect three tubes together, a flow meter to adjust the flow rate of argon gas, a

19

Gas/Liquid separator and a quartz T-shaped tube to perform analyses. One of the

peristaltic pumps was used to pump arsenic samples and NaBH4 solution to the

reaction coil. The other peristaltic pump was used to remove liquid waste from the

system.

Figure 3.3: Hydride Generator for Arsenic analysis.

Figure 3.3 shows hydride generator system connected to Atomic Absorption

Spectrometer (AAS) which was used in this study to determine arsenic

concentrations in simulated water samples. The method was based on forming

arsenic trihydride (gas phase) which was carried to a quartz T-shaped tube placed on

the burner of AAS. An air/acetylene flame was used to heat the quartz tube atomizer.

Arsenic samples and sodium borohydride (NaBH4) solution were sent to the reaction

coil by means of a peristaltic pump where gaseous arsenic trihydride (AsH3) was

formed. The products formed in the reaction coil were stripped to Gas/Liquid

separator via argon gas. The part where gaseous products were stripped by argon is

called stripping coil. After stripping section, liquid and gas phases were separated in

the separator and liquid phase was pumped into waste with the help of other

peristaltic pump.

20

3.2.3.2 Optimization of HG-AAS instrument

Before analyzing arsenic samples obtained from ultrafiltration experiments, the

features of the hydride generator system must have been optimized. Firstly, quartz T-

shaped tube was saturated with 10 mg/L As solution to prevent capturing of arsenic

by the tube. Once the tube is saturated with high concentrations of arsenic solution,

the following analyses would give more accurate results because of minimizing the

possibility of arsenic to be captured by the tube. The next step was to optimize the

parameters which were; concentrations of HCl and NaBH4 solutions, flow rate of

argon gas, reaction coil length, stripping coil length, flow rates of arsenic sample and

NaBH4 solution. These parameters were optimized by changing one parameter while

the other parameters were kept constant at the same value. Optimization cycles were

repeated until a stable and repeatable signal was obtained.

3.2.3.2.1 Effect of HCl Concentration

The concentration of HCl was determined in trials. In the optimization part of this

study, the experiments were conducted with 100 µg/L As solutions which contain

different concentrations of HCl prepared between 0.5-3 M. The results can be

observed in Figure 3.4 as absorbance values read vs. concentration values of HCl.

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0 0.5 1 1.5 2 2.5 3 3.5

Ab

s

HCl concentration (M)

Figure 3.4: Absorbance values for 100 µg/L As solution at different HCl

concentrations. Other parameters kept constant as; NaBH4 concentration: 5 g/L,

argon flow rate: 102 mL/min, reaction coil length: 25 cm, stripping coil length: 97.5

cm, sample flow rate: 3.24 mL/min, NaBH4 flow rate: 3.33 mL/min.

21

As seen in Figure 3.4, the optimum HCl concentration was obtained as 1 M. So,

other parameters were determined with solutions containing 1 M HCl. The

equivalent concentrations of HCl solutions were used in standards, samples and

blank to ensure equivalent responses during the analyses. Solution of 1 M HCl was

used as the blank after every measurement.

3.2.3.2.2 Effect of NaBH4 Concentration

In this study, NaBH4 solution was used as the reducing agent to produce arsenic

trihydride. Campbell (1992) reported that NaBH4 solutions could be prepared

between a concentration range of 5 and 50 g/L by the addition of potassium or

sodium hydroxide to make solution alkaline. The alkalinity of NaBH4 solution had

important impact on its stability. According to this information, 6 g of NaOH pellet

was dissolved in 1 L and pH value of this solution was measured as 12.5. So, it was

decided that 6 g of NaOH pellet would be enough to make solution alkaline.

0

0.1

0.2

0.3

0.4

0.5

0 5 10 15 20 25 30

Ab

s

NaBH4 Concentration (g/L)

Figure 3.5: Absorbance values for 100 µg/L As solution at different NaBH4

concentrations. Other parameters kept constant as; HCl concentration: 1M, Argon

flow rate: 102 mL/min, reaction coil length: 25 cm, stripping coil length: 97.5 cm,

sample flow rate: 3.24 mL/min, NaBH4 flow rate: 3.33 mL/min.

Figure 3.5 shows that maximum absorbance values were read when concentration of

NaBH4 solution was 10 g/L. As a result, NaBH4 solutions were prepared for the next

22

experiments by dissolving 10 g of NaBH4 powder and 6 g of NaOH pellets in a 1 L

of solution.

3.2.3.2.3 Effect of Argon Flow Rate

In this study, argon gas was used to strip products obtained in reaction coil to

Gas/Liquid separator and flow rate of argon played an important role on stripping

section. Thus, the flow rate had a significant effect on the absorbance value.

Experiments were conducted in order to observe effect of argon flow rate on

absorbance values. The results are summarized in Figure 3.6 as absorbance values

read vs. flow meter reading in terms of mm.

0.00

0.10

0.20

0.30

0.40

0.50

0.60

5 10 15 20 25 30

Ab

s

Flow meter reading (mm)

Figure 3.6: Absorbance values for 100 µg/L As solution at different argon flow

rates. Other parameters kept constant as; HCl concentration: 1M, NaBH4

concentration: 10 g/L, reaction coil length: 25 cm, stripping coil length: 97.5 cm,

sample flow rate: 3.24 mL/min, NaBH4 flow rate: 3.33 mL/min.

Figure 3.6 shows that the highest and most stable absorbance values were obtained

when the float of the flow meter was at a height of 15 mm. The manufacturer

company of the flow meter is Cole Parmer Inc. From the calibration values provided

by Cole Parmer Inc., it was seen that reading value of 15 mm corresponded to 179

mL/min as specified in Table B.4. So, the flow rate of argon was determined as 179

mL/min.

23

3.2.3.2.4 Effect of Reaction Coil Length

After optimizing flow rate of argon, its flow rate was adjusted to 179 mL/min and the

next experiments were conducted in order to observe the effect of the length of

reaction coil. The results are summarized in Figure 3.7 as absorbance values read vs.

reaction coil length in terms of cm.

0.30

0.40

0.50

0.60

15 20 25 30 35 40 45 50

Ab

s

reaction coil length (cm)

Figure 3.7: Absorbance values for 100 µg/L As solution at different reaction coil

lengths. Other parameters kept constant as; HCl concentration: 1M, NaBH4

concentration: 10 g/L, Argon flow rate: 179 mL/min, stripping coil length: 97.5 cm,

sample flow rate: 3.24 mL/min, NaBH4 flow rate: 3.33 mL/min.

As seen in Figure 3.7, the optimum reaction coil length was obtained as 35 cm long

for this system. Next parameters were optimized by keeping the reaction coil length

constant at 35 cm long.

3.2.3.2.5 Effect of Stripping Coil Length

The next parameter to be optimized was stripping coil length. Results of the

experiments conducted in order to observe effect of length of stripping coil on

absorbance values read are specified in Table 3.6 and Figure 3.8 as absorbance

values read vs. stripping coil length in terms of cm.

24

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0.60

75 80 85 90 95 100 105

Ab

s

stripping coil length (cm)

Figure 3.8: Absorbance values for 100 µg/L As solution at different stripping coil

lengths. Other parameters kept constant as; HCl concentration: 1M, NaBH4

concentration: 10 g/L, Argon flow rate: 179 mL/min, reaction coil length: 35 cm,

sample flow rate: 3.24 mL/min, NaBH4 flow rate: 3.33 mL/min.

Figure 3.8 shows that the highest absorbance values read were achieved at the

stripping coil length of 97.5 cm which was the length chosen in the beginning of the

optimization.

3.2.3.2.6 Effect of sample flow rate and NaBH4

Finally, the flow rates of sample and NaBH4 solution were optimized. The effect of

sample flow rate on absorbance values read was observed by the analyses made. The

results are summarized in Figure 3.9 as absorbance values read vs. sample flow rate

in terms of mL/min.

25

0.00

0.10

0.20

0.30

0.40

0.50

0.60

2.50 2.70 2.90 3.10 3.30 3.50 3.70

Ab

s

Sample flow rate (mL/min)

Figure 3.9: Absorbance values for 100 µg/L As solution at different sample flow

rates. Other parameters kept constant as; HCl concentration: 1M, NaBH4

concentration: 10 g/L, Argon flow rate: 179 mL/min, reaction coil length: 35 cm,

stripping coil length: 97.5 cm, NaBH4 flow rate: 3.33 mL/min.

As can be observed in Figure 3.9, the optimum sample flow rate was obtained as

3.24 mL/min for this system.

When absorbance values for 100 µg/L As solution at different NaBH4 flow rates

were observed, it was seen that absorbance values were almost the same. So, it was

concluded that the absorbance values were not affected by the change in flow rate of

NaBH4 significantly and this value was specified as 3.33 mL/min which was the

value chosen in the beginning of the optimization process.

As a result the optimum values for HG-AAS system are specified as;

HCl concentration in solutions: 1 M,

Concentration of NaBH4 solution: 10 g/L,

Argon flow rate: 179 mL/min,

Reaction coil length: 35 cm,

Stripping coil length: 97.5 cm,

Sample flow rate: 3.24 mL/min

NaBH4 flow rate: 3.33 mL/min.

26

3.2.3.2.7 Calibration Curves

The calibration of the HG-AAS is required in the beginning of every analysis to

make sure that the instrument is providing accurate absorbance values when the

solutions are introduced to the instrument. Therefore, calibration curves were

obtained for concentrations lower than 10 μg/L and higher than 10 μg/L after

parameters of hydride generator part were optimized. The results are given in Tables

3.1 and 3.2 and by using these values, Figures 3.10 and 3.11 were plotted. Calculated

concentration values were determined by substituting average of reading values into

the equations obtained from the Figures 3.10 and 3.11. Then, concentrations of

calculated values and the standard solutions were compared and the error values

were calculated. These error values (%) can be observed in Tables 3.1 and 3.2.

Table 3.1: Calibration data for lower concentrations.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Calculated

concentration

(μg/L)

Error

(%)

3 0.0213 0.0203 0.0214 0.0210 3.28 9.3

4 0.0277 0.028 0.0268 0.0275 4.04 1.1

5 0.0362 0.0387 0.0351 0.0367 5.39 7.8

6 0.0405 0.0411 0.0428 0.0415 6.10 1.6

8 0.0534 0.0521 0.0531 0.0529 7.77 2.8

10 0.0656 0.0652 0.0666 0.0658 9.68 3.2

27

Table 3.2: Calibration data for higher concentrations.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Calculated

concentration

(μg/L)

Error

(%)

10 0.0552 0.0565 0.0561 0.0559 10.55 5.5

20 0.1048 0.1052 0.1107 0.1069 20.17 0.8

30 0.1619 0.1591 0.1571 0.1594 30.07 0.2

40 0.2132 0.2116 0.2117 0.2122 40.03 0.1

50 0.2635 0.2632 0.2623 0.2630 49.62 0.7

y = 0.0068xR² = 0.9946

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0 2 4 6 8 10 12

Ab

s

As concentration (μg/L)

Figure 3.10: Calibration curve for concentrations lower than 10 μg/L.

28

y = 0.0053xR² = 0.9997

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0 10 20 30 40 50 60

Ab

s

As concentration (μg/L)

Figure 3.11: Calibration curve for concentrations higher than 10 μg/L.

From Tables 3.1 and 3.2 and Figures 3.10 and 3.11, the optimization of hydride part

of the instrument was sufficient to obtain reliable results for the analysis of As(III)

samples.

3.2.3.2.8 Reduction of As (V) to As (III)

As (V) samples obtained from ultrafiltration experiments were reduced first to As

(III) to analyze by HG-AAS. Pookrod et al. (2005) used potassium iodide and

ascorbic acid for reduction of As(V) to As (III). 5 g of potassium iodide and 5 g of

ascorbic acid were dissolved in 0.1 L and certain amount of this solution was added

to samples obtained from ultrafiltration experiments.

29

Table 3.3: Calibration data for standards reduced from As (V) to As (III).

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Calculated

concentration

(μg/L)

Error

(%)

5 0.0286 0.0295 0.0304 0.0295 5.36 7.3

10 0.0543 0.0538 0.054 0.0540 9.82 1.8

20 0.1137 0.1135 0.1134 0.1135 20.64 3.2

30 0.1678 0.1668 0.1672 0.1673 30.41 1.4

40 0.2111 0.2105 0.2135 0.2117 38.49 3.8

50 0.2798 0.2765 0.2789 0.2784 50.62 1.2

y = 0.0055xR² = 0.9984

0

0.05

0.1

0.15

0.2

0.25

0.3

0 10 20 30 40 50 60

Ab

s

As concentration (μg/L)

Figure 3.12: Calibration curve for standards reduced from As (V) to As (III).

In Table 3.3 and Figure 3.12, it was observed that the reduction was achieved with

addition of potassium iodide and ascorbic acid to the samples.

30

CHAPTER 4

RESULTS AND DISCUSSION

In this study, it was aimed to separate arsenic from water via batch and continuous

ultrafiltration methods. For continuous ultrafiltration experiments, polysulfone and

polyether sulfone membranes were used. Firstly, experiments using polysulfone

membrane were conducted to observe how pH change, arsenic speciation [As(III)

and As(V)], different concentrations of As(V) and other anions (SO42-

, HPO42-

, NO3-

and Cl-) affect the separation. Secondly, experiments using polyether sulfone to

separate As(V) at different pH values were performed. Finally, batch ultrafiltration

experiments were conducted by using regenerated cellulose membrane for separation

of As(III) and As(V).

Analyses were performed via HG-AAS. After measuring concentrations of permeate

and feed solutions by HG-AAS, the ability of a membrane to retain arsenic was

determined with Retention value which was calculated by using the following

formula:

R (%) (4.1)

Cp : arsenic concentration in the permeate

Cf : arsenic concentration in the feed

Permeate flux (Fp) is defined as the amount of permeate flowing across the

membrane per unit time per unit membrane area.

31

4.1. Continuous Ultrafiltration Experiments

4.1.1. Experiments Conducted with Polysulfone (PS) Membrane

This part consists of experiments conducted with PS membrane. PS membranes were

specified as negatively charged membrane in various studies (Kim et al., 2002;

Brandhuber et al., 2001; Seidel et al., 2001). All these studies showed that membrane

charge increased as pH increased. In the study of Kim et al. (2002), zeta potential

measurements for determination of charge of PS membrane (which has 30 kDa

molecular weight cut-off) were performed. These values were determined as around

-13 mV at pH=8 and -22 mV at pH=12. In this part, influence of arsenic speciation,

pH effect and effect of presence of other anions on retention were investigated.

4.1.1.1. Effect of pH on separation of As(III)

First, experiments were conducted to separate As(III) with PS membrane at different

pH values between 6-11 with 1.0 increments at a temperature of 25.0 °C. Results of a

representative experimental run (which is the one conducted at pH=11) can be

observed in Table 4.1. This table shows that experiment reached steady state in an

hour after experiment was initiated. Also, it can be seen that all permeate

concentrations exceeded the permissible limit of 10 µg/L when initial concentration

of As(III) was 30 µg/L. The results of experiments conducted at pH=10, 9, 8, 7, 6 are

listed in Appendix B.

Table 4.1: Retention values obtained for As(III) at pH=11.0 and at T=25 °C with PS

membrane (ΔP=200 kPa).

t (min) 0 60 120 180 240

Fp (L/m2h) 11.8 11.7 11.9 11.8

pH 10.9 10.9 11.0 11.0 11.0

T(°C) 24.6 25.4 25.6 25.1 25.3

Cf (µg/L) 30.6 31.0 31.1 31.2 31.8

Cp (µg/L) - 19.4 19.2 19.3 19.7

R (%) - 37.4 38.3 38.1 38.1

32

Table 4.2 shows the average retention values for As(III) at pH values between 6-11.

Due to the results, it can be observed that separation of As(III) was not sufficient

with PS membrane. The highest removal was obtained as 38.0 % at pH=11.

Table 4.2: Average retention values for As(III) at pH values between 6-11 with PS

membrane.

pH R (%)

6 4.1

7 6.2

8 10.5

9 34.7

10 36.6

11 38.0

0

10

20

30

40

50

60

70

80

90

100

5 7 9 11 13

R (

%)

pH

Figure 4.1: The retention values obtained for As (III) at pH values between 6-11

with PS membrane.

As seen in Figure 4.1; retention value of As(III) increased as pH increased. In the

study of Brandhuber et al. (2001), the same observations - an increase in retention

with pH increment and inefficient separation of As(III) with PS membrane – were

encountered. However, pressure difference values were not reported in their retention

33

studies. Also, in the study of Seidel et al. (2001), retention values for As(III) were

found to be very low at pH range of 4.5-8.5 with the usage of sulfonated polysulfone

nanofiltration membrane. In that study, higher pH values (pH>8.5) were not studied.

On the other hand, in the present study; the effect of pH could be observed also for

pH>8.5. It can be said that removal of As (III) with PS membrane in this study were

not sufficient as in the literature. There is an increasing behaviour on retention values

as pH increases. In Figure 2.2, it can be seen that As(III) is mostly present as

uncharged species of As(OH)3 at neutral pH. As pH increases, fraction of monovalent

ion of H2AsO3−

rises. Increase in retention of As(III) with increasing pH seems to be

expected due to mentioned Donnan effect on separation. Donnan exclusion principle

might play a role on separation as pH of solution increased.

4.1.1.2. Effect of pH on separation of As(V)

After As(III) experiments, the separation of As(V) from water was investigated with

PS membrane at different pH values between 6-11 with 1.0 increments at a

temperature of 25.0 °C. Results of a representative experimental run (which is the

one conducted at pH=11.0) can be observed in Table 4.3. This table shows that

steady state was attained in an hour after experiment was initiated. Also, it can be

seen that all permeate concentrations were below the permissible limit of 10 µg/L

with initial concentration of As(III) as 30 µg/L. The results of experiments conducted

at pH=10, 9, 8, 7, 6 can be observed in Appendix B.

Table 4.3: Retention values obtained for As(V) at pH=11.0 at T=25 °C with PS

membrane (ΔP=200 kPa).

t (min) 0 60 120 180 240

Fp (L/m2h) 11.6 11.4 11.7 11.4

pH 11.0 11.0 11.0 11.0 11.1

T(°C) 24.9 25.2 25.4 25.3 25.4

Cf (µg/L) 31.6 32.6 32.6 33.1 33.1

Cp (µg/L) - 3.5 3.5 3.4 3.3

R (%) - 89.3 89.3 89.7 90.0

34

Table 4.4 shows the average retention values for As(V) at pH values between 6-11.

Due to the results, separation of As(V) with PS membrane seems to be more efficient

as pH of the solution increases. The highest removal was obtained as 94.7 % at

pH=10.0.

Table 4.4: Average retention values for As(V) at pH values between 6-11 with PS

membrane.

pH R (%)

6 52.0

7 56.9

8 75.1

9 91.5

10 94.7

11 89.6

0

20

40

60

80

100

5 6 7 8 9 10 11 12

R (

%)

pH

Figure 4.2: The retention values obtained for As (V) at pH values between 6-11 with

PS membrane.

As seen in Figure 4.2, an increasing behaviour on retention values was observed as

pH of feed solution increased. The results in Table 4.4 and Fig. 4.2 are consistent

with the ones obtained by Seidel et al. (2001), Brandhuber et al. (2001), Lohokare et

35

al. (2008). In the study of Seidel et al. (2001), sulfonated polysulfone nanofiltration

membrane was used. Lohokare et al. (2008) performed As(V) removal with modified

polyacrylonitrile (PAN) membrane and observed increment in retention when pH of

the solution was increased. This increasing trend in retention values can be due to

As(V) distribution in water at different pH values. When Figure 2.2 was observed,

percentage of presence of divalent arsenic anion (HAsO42-

) decreased as pH of the

solution decreased. At pH 7, almost equal concentrations of HAsO42-

and H2AsO4−

are present. In the study of Seidel et al. (2001), it was claimed that Donnan effect is

more dominant for divalent ions compared to monovalent anions. So, increment was

expected at pH values of pH≥7. Also, no appreciable effect of pH on As(V) retention

was observed between pH=9 and pH=11 (Fig. 4.2). As(V) removal results obtained

by Seidel et al. (2001) were able to be enhanced in the present study by increasing

pH beyond pH=8.5.

In Table 4.5, retention values for the experiments of As(III) and As(V) at the same

pH values were compared to see how arsenic speciation affected the removal. It can

be observed that retention values for As(V) were much higher compared to retention

values for As(III) at all pH values.

Table 4.5: Average retention values for As (III) and As (V) at pH values between 6-

11 with PS membrane.

pH R (%) for As (III) R (%) for As (V)

6 4.1 52.0

7 6.2 56.9

8 10.5 75.1

9 34.7 91.5

10 36.6 94.7

11 38.0 89.6

36

0

10

20

30

40

50

60

70

80

90

100

5 7 9 11 13

R (

%)

pH

As(III)

As(V)

Figure 4.3: Comparison of the retention values for As(III) and As(V) at pH values

between 6-11 with PS membrane.

Figure 4.3 shows the results of As(III) and As(V) at pH values between 6-11. It is

again observed that removal of As(V) was much higher compared to removal of

As(III). It was predicted that distribution of As(III) and As(V) in water caused this

difference. As observed in Fig. 2.2, uncharged species of As(III) is dominant at

neutral pH and monovalent anion form of As(III) is present as pH increases. On the

other hand, As(V) is in monovalent and divalent anion forms at studied pH values.

So, the differences between retention values of As(III) and As(V) is reasonable since

As(V) is present as divalent and monovalent anions while As(III) is present as

uncharged and monovalent anion at that working pH range. Because as mentioned

before, Donnan exclusion is more effective when ion charge of species increases.

Also, this difference may lead the prediction that size exclusion is not dominant in

removal of arsenic since molecular weights of As(III) and As(V) are close to each

other. Divalent ion of As(V) which is HAsO42-

has molecular weight of 140 g/mol

and uncharged species of As(III) which is As(OH)3 has molecular weight of 126

g/mol. If size exclusion played important role on removal of arsenic, similar results

for As(III) and As(V) would be expected.

In the study of Brandhuber et al. (2001), it was also mentioned that membrane charge

affected the removal of arsenic. Because charge of PS membrane increases as pH of

37

solution increases. So, increasing behaviour of As(III) and As(V) removal with

increase of pH may be due to arsenic chemistry and also membrane charge.

4.1.1.3. Effect of Increasing Feed Concentration of As(V) on Retention

To understand the influence of increasing As(V) concentration on retention,

experiments were conducted at pH=10.0 with feed concetration of 30, 100, 500, 1000

and 10 000 µg/L. at a temperature of 25.0 °C. Results of a representative

experimental run (which is the one conducted at CAs(V) = 30 µg/L) can be observed in

Table 4.6. The experiment for 30 µg/L was conducted again. The results of these two

experiments can be seen in Table 4.3 and Table 4.6. When these results were

compared, it was seen that retention values were almost same and close enough

which made the results more reliable. The results of experiments conducted at CAs(V)

=100, 500, 1000 and 10 000 µg/L can be observed in Appendix B.

Table 4.6: Retention values obtained for CAs(V) = 30 µg/L at pH=10.0 at T=25 °C

with PS membrane (ΔP=200 kPa).

t (min) 0 60 120 180 240

Fp (L/m2h) 11.8 11.8 11.9 11.9

pH 10.0 10.0 10.0 10.0 10.1

T(°C) 24.7 25.0 25.3 25.23 25.3

Cf (µg/L) 31.4 31.9 32.7 33.2 34.3

Cp (µg/L) - 1.7 1.8 1.7 1.9

R (%) - 94.7 94.5 94.8 94.5

In Table 4.7, average retention values of experiments conducted at pH=10 can be

seen. It can be observed that the lowest retention value was obtained as 90.8 % at a

feed concentration of CAs(V)= 10000 µg/L.

38

Table 4.7: Average retention values for different As(V) concentrations at pH=10.0 at

T=25 °C with PS membrane (ΔP=200 kPa).

CAs(V) (µg/L) Fp (L/m2h) R (%)

30 11.9 94.6

100 12.0 94.2

500 12.0 93.7

1000 11.9 91.7

10000 11.9 90.8

30 µg/L 100 µg/L 500 µg/L 1 mg/L 10 mg/L

0

10

20

30

40

50

60

70

80

90

100

1

R(%

)

pH=10

Figure 4.4: Effect of increasing As(V) concentration on retention at pH=10.0 at

T=25 °C with PS membrane (ΔP=200 kPa).

As seen in Fig. 4.4, retention values decreased as arsenic concentration of feed

solution increased. It limits the applicability of this membrane itself to separate

arsenic at higher concentrations. In the study of Lohokare et al. (2008), decreasing

behaviour in retention was observed as feed concentration of As(V) increased. This

behaviour was explained via concentration polarization. Accumulation of solute

molecules adjacent to the membrane surface causes concentration polarization. An

increase in arsenic feed concentration may cause increase of arsenic at the membrane

surface. So, increase in concentration polarization and thus decrease in the retention

can be observed. This is probably not the case in present study since concentration

did not affect the permeate flux. Decrease in retention can be explained by increase

39

in ionic strength of feed solution which may give rise to permeation of arsenate

[As(V)] anion.

4.1.1.4. Effect of Other Anions on Retention

Effect of other anions (SO42-

, HPO42-

, NO3- and Cl

-) on retention was investigated.

Experiments were conducted with 30 µg/L of As(V) and 30 mg/L of other anion

selected at a temperature of 25 °C. Results of a representative experimental run

(which is the one conducted with 2.15x10-7

M of As(V) and 3.125x10-4

M SO42-

) can

be seen in Table 4.8. The results for HPO42-

, NO3- and Cl

- are listed in Appendix B.

Table 4.8:Results of 2.15x10-7

M of As(V) experiments conducted with 3.125x10-4

M

SO42-

presence at pH=10.0 at T=25 °C with PS membrane (ΔP=200 kPa).

In Table 4.9, average retention values of As(V) with and without anions at pH=10.0

can be observed. The retention value when only arsenic was present was higher than

retention values with the presence of other anions. Experiments with NO3- and Cl

-

were conducted at two different concentrations of anions. In Table 4.9, decrease in

retention values was observed as concentration of anions (NO3- and Cl

-) in solution

increased. This can be explained with increase in competition of anions with arsenic

as anions’ concentration increased.

t (min) 0 60 120 180 240

Fp (L/m2h) 13.2 12.8 12.9 13.1

pH 10.0 10.0 10.0 9.9 10.0

T(°C) 25.0 25.1 25.5 25.6 25.5

Cf (µg/L) 28.0 27.8 29.8 31.1 31.3

Cp (µg/L) - 3.9 4.3 4.4 4.4

R (%) - 86.0 85.6 85.9 85.9

40

Table 4.9: Average retention values of As(V) with and without anions at pH=10.0 at

T=25 °C with PS membrane (ΔP=200 kPa).

Anion Concentration of anions (M) R (%)

No anion - 94.7

SO42-

3.125x10-4

85.9

HPO42-

3.125x10-4

88.9

NO3- 3.125x10

-4 89.9

NO3- 4.840x10

-4 84.5

Cl- 3.125x10

-4 90.5

Cl- 8.450x10

-4 87.0

SO42- HPO4

2- Cl- NO3-

No anion

0

10

20

30

40

50

60

70

80

90

100

1

R(%

)

pH=10

Figure 4.5: Retention values of 2.15x10-7

M of As(V) experiments conducted with

3.125x10-4

M anions at pH=10.0 at T=25°C with PS membrane (ΔP=200 kPa).

As seen in Fig. 4.5, presence of other anions resulted in a decrease in As(V)

retention. In the study of Brandhuber et al. (2001), decrease in retention of As(V) can

be observed with the presence of other anions. It can be assumed that there was

competition between As(V) and other anions. This also may lead that main

mechanism of separation was based on Donnan exclusion principle.

41

4.1.2. Experiments Conducted with Polyether sulfone (PES) Membrane

In this part, results of experiments conducted with PES membrane were discussed.

PES membranes were specified as slightly negatively charged membrane in various

studies (Weis et al., 2003; Ergican et al., 2005). In the study of Weis et al. (2002),

zeta potential measurements for determination of charge of 30 kDa of PES

membrane were determined between -0.5 and -2 mV.

The separation of As(V) from water was investigated with PES membrane at

different pH values between 7-10 with 1.0 increments at a temperature of 25.0 °C.

Results of a representative experimental run (which is the one conducted at pH=10)

can be observed in Table 4.10. From results it can be seen that steady state was

attained in an hour after experiment was initiated. Also, it can be seen that all

permeate concentrations were higher than the permissible limit of 10 µg/L when

initial concentration of As(III) was 30 µg/L. The results of experiments conducted at

pH= 9, 8, 7 can be observed in Appendix B.

Table 4.10: Results of 30 µg/L of As(V) experiments conducted at pH=10.0 at

T=25°C with PES membrane (ΔP=200 kPa).

Table 4.11 shows that average retention values for As(V) at pH range of 6-11. From

the results, it can be said that efficient removal of As(V) could not be achieved with

PES membrane. The highest removal was obtained as 58.6 % at pH 10.0.

t (min) 0 60 120 180 240

Fp (L/m2h) 7.7 7.7 7.7 7.8

pH 10.0 10.0 10.0 10.0 9.9

T(°C) 25.2 25.7 24.8 24.9 25.8

Cf (µg/L) 30.9 32.0 32.6 33.3 33.4

Cp (µg/L) - 13.4 13.4 13.8 13.8

R (%) - 58.1 58.8 58.7 58.8

42

Table 4.11: Average retention values for As(V) at pH values between 7-10 with PES

membrane.

pH R (%)

7 37.5

8 44.1

9 53.9

10 58.6

0

10

20

30

40

50

60

70

80

90

100

5 6 7 8 9 10 11 12

R(%

)

pH

Figure 4.6: The retention values obtained for As (V) at pH values between 7-10 with

PES membrane.

In Fig. 4.6, effect of pH on retention values with PES membrane can be seen. In the

study of Ergican et al. (2005), retention value of arsenate was obtained as 12.2% at

pH=8. As seen in Table 4.11, As(V) retention at pH=8 was 44 %. There is an

appreciable difference when compared with the result obtained by Ergican et al.

(2005). In the study of Ergican et al. (2005), experiments were carried out in batch

mode ultrafiltration system with 5 kDa PES membrane when initial concentration of

As(V) was 41 µg/L. The difference between results of Ergican et al. (2005) and

results in Fig. 4.6 may be due to the fact that Ergican et al. (2005) performed their

experiments in the batch mode; since in the batch mode, the concentration of As(V)

increases by time which may result in the decrease of retention. In the study of

43

Ergican et al. (2005), arsenate removal may be also suppressed due to higher applied

pressure which may partially overcome the ionic repulsion. Because in the study of

Ergican et al. (2005), applied pressure difference was 414 kPa and permeate flux was

measured as around the value of 180 L/m2h. In present work, this pressure difference

was adjusted to 200 kPa which resulted in a lower permeate flux value of 7.7 L/m2h.

0

10

20

30

40

50

60

70

80

90

100

5 7 9 11

R (

%)

pH

PES membrane

PS membrane

Figure 4.7: Comparison of the retention values for As(V) at different pH values with

PS and PES membranes.

In Fig. 4.7, retention values for As(V) at different pH values with 30 kDa of PS and

20 kDa of PES membranes can be seen. Retention values of experiments conducted

with PS membrane were higher than retention values obtained with PES membrane.

If size exclusion might play important role on separation, removal of As(V) with

PES membrane would have been more effective than PS membrane since PES

membrane has a lower molecular weight cut-off. As mentioned before, zeta potential

of PS membrane was much more in negative values compared to PES membrane.

This difference in retention values may be due to charge of membranes and thus

Donnan effect principle.

44

4.2. Batch Ultrafiltration Experiments

After continuous experiments conducted, batch ultrafiltration experiments were

performed with 3 kDa of regenerated cellulose (RC) membrane. The membrane

charge of RC was measured in several studies (Stana-Kleinschek et al., 2001; Werner

et al., 1999). In the study of Werner et al. (1999), zeta potential values varied

between 0 and – 15 mV and membrane charge increased as pH increased.

4.2.1. Experiments of As(III) Conducted with RC Membrane

Effect of pH on separation of As(III) with RC membrane was discussed. Experiments

were conducted at different pH values between 7-10 with 1.0 increments at a

temperature of 25.0 °C. Results of a representative experimental run (which is the

one conducted at pH=7.0) can be seen in Table 4.12. All permeate concentrations

were higher than the permissible limit of 10 µg/L in Table 4.12 when initial

concentration of As(III) was 30 µg/L. The results of experiments conducted at pH=

9, 8, 7 are listed in Appendix B.

Table 4.12: Results of As(III) experiments conducted at pH=7.0 with RC membrane

(ΔP=100 kPa) (Initial concentration: 29.2 µg/L).

Permeate sample no Cp (µg/L) Retention (%)

1 28.5 2.4

2 28.8 1.5

3 28.6 2.0

4 28.6 2.0

Table 4.13 shows the average retention values of As(III) experiments with RC

membrane. When retention values were observed, it may be said that RC membrane

was not effective for removal of As(III) at pH range of 7-10. The highest removal

was 32.9 % at pH=10.0.

45

Table 4.13: Comparison of retention values of As(III) experiments conducted at pH

values between 7-10 with RC membrane.

pH R (%)

7 2.1

8 10.4

9 28.0

10 32.9

4.2.2. Experiments Conducted with As(V) with RC Membrane

Applicability of RC membrane for As(V) separation was discussed in this part.

Experiments were conducted at different pH values between 7-10 with 1.0

increments at a temperature of 25.0 °C. Results of a representative experimental run

(which is the one conducted at pH=8.0) can be seen in Table 4.14. When Table 4.14

was observed, it can be seen that all permeate concentrations with initial

concentration of 30 µg/L of As(V) were lower than the permissible limit of 10 µg/L.

The results of experiments conducted at pH= 9, 8, 7 are listed in Appendix B.

Table 4.14: Results of As(V) experiments conducted at pH=8.0 with RC membrane

(ΔP=100 kPa) (Initial concentration: 26.7 µg/L).

Permeate sample no Cp (µg/L) Retention (%)

1 6.6 75.3

2 6.6 75.3

3 6.7 75.0

4 6.8 74.5

In Table 4.15, retention values of As(V) at pH values between 7 and 10 were

compared. Higher retention values for As(V) were obtained compared to As(III)

retention values. However, using only RC membrane is not sufficient for removal of

As(V) since the highest retention value was 77.8 % at pH=10.

46

Table 4.15: Comparison of retention values of As(V) experiments conducted at pH

values between 7-10.

pH R (%)

7 66.5

8 75.1

9 76.2

10 77.8

0

10

20

30

40

50

60

70

80

90

100

5 7 9 11

R (

%)

pH

As(V)

As(III)

Figure 4.8: Comparison of the retention values for As(III) and As(V) at pH values

between 7-10 with RC membrane.

Figure 4.8 summarized the results of As(III) and As(V) at pH values between 7-10

with RC membrane. Higher retention values of As(V) were obtained compared to

retention values of As(III). As mentioned before, As(V) is present as divalent and

monovalent anions while As(III) is present as uncharged and monovalent anion at

that pH range.

47

CHAPTER 5

CONCLUSIONS

In this study, firstly construction and optimization of hydride part of atomic

absorption spectrometer were performed. Calibration curves for As(III) and As(V)

standard solutions were obtained after As(V) reduction to As(III) was achieved.

Secondly, ultrafiltration experiments were conducted to remove arsenic from water.

Following conclusions were obtained:

An effective separation of As(III) could not be achieved. The highest removal

value was obtained as 38.0 % at pH=11 for PS membrane and 32.9 % for RC

membrane at pH=10. So, PS and RC membranes may not be suitable for

removal of As(III) in a single UF step.

Results of As(V) showed higher removal values than As(III). The highest

removal was obtained as 94.6 % at pH=10 with PS membrane.

Results showed that most effective separation of As(V) was achieved with PS

membrane compared to RC and PES membranes. Also, it is seen that

retention values increased as pH of feed solution was increased. This was

expected. Because as pH increases, presence of ionic form of As(V) in water

increases. This result supported the idea that separation may be due to ionic

interactions because of PS membrane charge.

48

When effect of increasing As(V) concentration on separation with PS

membrane was investigated, it was observed that retention value decreased

slightly as concentration increased. The lowest value for retention was

obtained as 90.8 % when concentration of As(V) was CAs(V)=10 000 µg/L.

Effect of other anions (SO42-

, HPO42-

, NO3- and Cl

-) on separation with PS

membrane was investigated. It was observed that retention value of arsenic

decreased nearly 10% with the presence of these anions when compared to

the results of the experiments conducted with only arsenic. This may be an

indication of competition of anions with arsenate ions. This situation also

supported the idea of Donnan exclusion principle may play important role on

separation.

It was observed that charged membranes could be an alternative way to

separate As(V) from water at high pH values. However, this method may not

be effective for removal of As(III).

49

CHAPTER 6

RECOMMENDATIONS

Arsenic presence in water sources is a big concern for human health. Studies showed

that many water sources of earth and Turkey contain arsenic in water. That’s why in

this study removal of arsenic via continuous and batch mode ultrafiltration methods

was investigated and results were discussed. The following studies can be

recommended as the further examinations on this subject:

Experiments can be conducted with natural groundwater collected from

Kütahya, İzmir, Aksaray. So, it can be determined whether this method is

sufficient for natural groundwater or not.

This method was insufficient for As(III) removal for PS membrane and RC

membrane. A suitable polymer can be synthesized to bind As(III), so that

polymer enhanced ultrafiltration method can be applied and higher removal

values can be obtained.

In the study, it was also observed that in the experiments of feed arsenic

concentration exceeding 100 µg/L of As(V) caused a decrease in retention

when PS membrane was used. So that, permeate concentration exceeded the

permissible limit of 10 µg/L. It is suggested that successive experiments can

be conducted for the same solution to decrease permeate concentration below

this permissible limit. Alternatively, the studied method can be used in

combination with arsenic removal techniques.

50

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55

APPENDIX A

ANALYSIS DATA FOR OPTIMIZATION OF HG-AAS

Table A.1: Absorbance values for 100 µg/L As solution at different HCl

concentrations.

HCl Concentrations

(M)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of abs

read values

0.5 0.3686 0.3687 0.3921 0.3765

1 0.453 0.4432 0.4242 0.4401

1.5 0.4067 0.4098 0.4163 0.4109

2 0.4103 0.41 0.4211 0.4138

3 0.3967 0.4058 0.4192 0.4072

Table A.2: Absorbance values for 100 µg/L As solution at different NaBH4

concentrations.

NaBH4 Concentration

(g/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of abs

read values

5 0.3628 0.365 0.375 0.3676

10 0.4569 0.4639 0.4673 0.4627

15 0.4058 0.4186 0.428 0.4174

20 0.4075 0.3946 0.3911 0.3977

25 0.3439 0.3446 0.3462 0.3449

56

Table A.3: Absorbance values for 100 µg/L As solution at different argon flow rates.

Argon flow meter

read (mm)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

10 0.4651 0.4564 0.4545 0.4587

15 0.4874 0.4803 0.4888 0.4855

17 0.4062 0.3935 0.3951 0.3983

20 0.248 0.2423 0.2402 0.2435

25 0.2056 0.2023 0.2001 0.2027

Table A.4: Calibration values of flow meter for argon gas.

Flow meter reading (mm) Flow rate (mL/min)

65.0 2279.0

60.0 2027.0

55.0 1830.0

50.0 1591.0

45.0 1355.0

40.0 1144.0

35.0 950.0

30.0 728.0

25.0 518.0

20.0 326.0

15.0 179.0

10.0 102.0

5.0 51.0

57

Table A.5: Absorbance values for 100 µg/L As solution at different reaction coil

lengths.

Reaction coil length

(cm)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

20 0.4618 0.4757 0.4733 0.4703

25 0.4874 0.4803 0.4888 0.4855

30 0.5145 0.5014 0.4977 0.5045

35 0.5427 0.5336 0.5249 0.5337

40 0.5204 0.5135 0.5145 0.5161

45 0.4948 0.496 0.4897 0.4935

Table A.6: Absorbance values for 100 µg/L As solution at different stripping coil

lengths.

Stripping coil length

(cm)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

80 0.4495 0.4457 0.4463 0.4472

85 0.4633 0.4559 0.4628 0.4607

90 0.4811 0.4829 0.4904 0.4848

95 0.4979 0.4944 0.5063 0.4995

97.5 0.5427 0.5336 0.5249 0.5337

100 0.4512 0.4428 0.4495 0.4478

102 0.4356 0.4287 0.4209 0.4284

58

Table A.7: Absorbance values for 100 µg/L As solution at different sample flow

rates.

Sample flow rate

(mL/min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

2.86 0.3941 0.4033 0.3966 0.3980

3.08 0.4220 0.4290 0.4196 0.4235

3.15 0.4416 0.4400 0.4424 0.4413

3.24 0.5235 0.5345 0.5443 0.5341

3.47 0.3661 0.3632 0.3605 0.3633

59

APPENDIX B

RESULTS OF THE EXPERIMENTS OF AS(III) AND AS(V)

CONDUCTED WITH PS, PES, RC MEMBRANES

B.1 Results of As(III) experiments with PS membrane

Table B.1: Retention values obtained for As(III) at pH=10.0 with PS membrane.

t (min) 0 60 120 180 240

pH 10.04 10.01 10.06 10.01 10.04

T(°C) 25.4 25.1 25.0 25.4 25.3

Cf (µg/L) 28.2 28.0 28.3 29.6 30.1

Cp (µg/L) - 17.7 18.1 18.7 19.0

R (%) - 36.8 36.0 36.8 36.9

Table B.2: Retention values obtained for As(III) at pH=9.0 with PS membrane.

t (min) 0 60 120 180 240

pH 9.02 9.02 9.08 9.07 8.98

T(°C) 24.3 25.1 25.2 25.3 25.3

Cf (µg/L) 24.0 24.0 24.3 24.8 25.2

Cp (µg/L) - 15.6 15.8 16.2 16.6

R (%) 35.0 35.0 34.7 34.1

60

Table B.3: Retention values obtained for As (III) at pH=8.0 with PS membrane.

t (min) 0 60 120 180 240

pH 8.03 8.06 7.97 7.99 7.94

T(°C) 25.3 25.4 25.3 25.4 25.2

Cf (µg/L) 26.5 27.2 27.0 27.0 27.3

Cp (µg/L) - 24.3 24.2 24.1 24.5

R (%) - 10.6 10.4 10.7 10.3

Table B.4: Retention values obtained for As (III) at pH=7.0 with PS membrane.

t (min) 0 60 120 180 240

pH 7.03 7.07 7.02 6.96 7.09

T(°C) 24.7 25.1 25.2 25.2 25.1

Cf (µg/L) 33.3 33.4 33.3 33.5 33.1

Cp (µg/L) - 31.5 31.4 31.3 30.9

R (%) - 5.7 5.7 6.6 6.6

Table B.5: Retention values obtained for As(III) at pH=6.0 with PS membrane.

t (min) 0 60 120 180 240

pH 6.02 6.01 5.94 6.01 6.08

T(°C) 24.8 25.2 25.1 25.1 25.1

Cf (µg/L) 28.0 28.6 28.6 28.7 28.6

Cp (µg/L) - 27.4 27.5 27.5 27.4

R (%) - 4.2 3.8 4.2 4.2

61

B.2 Results of As(V) experiments with PS membrane

Table B.6: Retention values obtained for As(V) at pH=10.0 with PS membrane.

t (min) 0 60 120 180 240

pH 10.2 10.01 9.97 9.95 10.03

T(°C) 24.8 25.4 25.4 25.6 25.1

Cf (µg/L) 31.8 31.9 33.8 33.5 34.5

Cp (µg/L) - 1.7 1.8 1.8 1.7

R (%) - 94.7 94.7 94.6 95.1

Table B.7: Retention values obtained for As (V) at pH=9.0 with PS membrane.

t (min) 0 60 120 180 240

pH 9.02 9.02 8.97 8.91 8.95

T(°C) 25.6 25.2 25.3 25.4 25.3

Cf (µg/L) 30.7 30.9 31.7 34.1 34.3

Cp (µg/L) - 2.7 2.7 2.7 3.0

R (%) - 91.2 91.5 92.1 91.3

Table B.8: Retention values obtained for As (V) at pH=8.0 with PS membrane.

t (min) 0 60 120 180 240

pH 8.04 8.02 8.09 8.05 8.03

T(°C) 25.6 25.5 25.5 25.3 25.3

Cf (µg/L) 32.1 32.4 32.4 32.9 33.8

Cp (µg/L) - 7.9 8.2 8.3 8.4

R (%) - 75.6 74.7 74.8 75.1

62

Table B.9: Retention values obtained for As (V) at pH=7.0 with PS membrane.

t (min) 0 60 120 180 240

pH 7.1 7.0 7.0 7.0 7.1

T(°C) 25.8 25.3 25.5 25.6 25.5

Cf (µg/L) 27.7 27.7 28.4 28.1 29.6

Cp (µg/L) - 11.8 12.3 12.2 12.7

R (%) - 57 57 57 57

Table B.10: Retention values obtained for As (V) at pH=6.0 with PS membrane.

t (min) 0 60 120 180 240

pH 6.0 6.1 6.1 6.0 6.0

T(°C) 25.0 25.3 25.2 25.3 24.9

Cf (µg/L) 28.6 28.3 28.9 29.4 29.5

Cp (µg/L) 13.7 13.8 14.1 14.1

R (%) 52 52 52 52

B.3 Results of Increasing As(V) Concentration on Retention with PS

membrane

Table B.11: Retention values obtained for CAs(V) = 100 µg/L with PS membrane.

t (min) 0 60 120 180 240

pH 10.0 10.1 10.1 10. 1 10.0

T(°C) 25.2 25.3 25.6 25.1 25.3

Cf (µg/L) 101.2 101.9 103.6 105.8 107.7

Cp (µg/L) - 6.0 6.0 6.0 6.2

R (%) - 94 94 94 94

63

Table B.12: Retention values obtained for CAs(V) = 500 µg/L with PS membrane.

t (min) 0 60 120 180 240

pH 10.0 10.1 10.0 10.0 10.1

T(°C) 24.5 24.8 25.3 25.1 25.2

Cf (µg/L) 514.6 516.2 525.7 539.8 554.7

Cp (µg/L) - 32.4 32.7 34.6 34.3

R (%) - 94 94 94 94

Table B.13: Retention values obtained for CAs(V) = 1000 µg/L (1 mg/L) with PS

membrane.

t (min) 0 60 120 180 240

pH 10.0 10.0 10.0 10.0 10.0

T(°C) 25.2 25.2 25.1 25.4 25.1

Cf (µg/L) 1126.3 1134.0 1149.5 1182.4 1199.1

Cp (µg/L) - 95.9 96.2 95.9 100.9

R (%) - 92 92 92 92

Table B.14: Retention values obtained for CAs(V) = 10000 µg/L (10 mg/L) with PS

membrane.

t (min) 0 60 120 180 240

pH 7.07 6.96 6.98 6.97 7.06

T(°C) 25.8 25.3 25.5 25.6 25.5

Cf (µg/L) 10323.9 10238.3 10439.0 10804.0 10934.3

Cp (µg/L) - 943.7 987.1 982.4 1009.4

R (%) - 91 91 91 91

64

B.4 Results of Other Anions on Retention with PS membrane

Table B.15: Results of 2.15x10-7

M of As(V) experiments conducted with 3.125x10-4

M HPO42-

presence at pH=10.0.

Table B.16: Results of 2.15x10-7

M of As(V) experiments conducted with 3.125x10-4

M NO3- presence at pH=10.0.

Table B.17: Results of 2.15x10-7

M of As(V) experiments conducted with 4.840x10-4

M NO3- presence at pH=10.0.

t (min) 0 60 120 180 240

pH 10.0 10.1 10.0 9.9 10.0

T(°C) 24.5 25.3 25.5 25.5 25.5

Cf (µg/L) 30.9 31.5 33.4 34.6 34.2

Cp (µg/L) - 3.6 3.6 3.7 4.0

R (%) - 89 89 89 88

t (min) 0 60 120 180 240

pH 10.0 10.1 10.0 10.0 10.0

T(°C) 25.6 25.5 25.7 25.2 25.6

Cf (µg/L) 31.9 31.7 31.3 31.1 32.5

Cp (µg/L) - 3.1 3.3 3.3 3.2

R (%) - 90.4 89.5 89.5 90.3

t (min) 0 60 120 180 240

pH 10.0 10.0 10.2 10.2 10.2

T(°C) 25.0 25.0 25.5 25.4 25.4

Cf (µg/L) 31.6 31.4 32.4 33.1 34.3

Cp (µg/L) - 4.8 5.0 5.0 5.5

R (%) - 84.7 84.6 84.9 84.0

65

Table B.18:Results of 2.15x10-7

M of As(V) experiments conducted with 4.840x10-4

M Cl- presence at pH=10.0.

Table B.19: Results of 2.15x10-7

M of As(V) experiment conducted with 8.450x10-4

M Cl- presence at pH=10.0.

B.5 Results of As(V) experiments with PES membrane

Table B.20: Results of 30 µg/L of As(V) experiments conducted at pH=9.0 with

PES membrane.

t (min) 0 60 120 180 240

pH 10.0 10.0 9.9 10.0 9.9

T(°C) 25.2 25.3 25.8 25.6 25.7

Cf (µg/L) 31.9 31.5 31.5 31.0 33.7

Cp (µg/L) - 2.9 3.0 3.0 3.2

R (%) - 90.8 90.4 90.4 90.6

t (min) 0 60 120 180 240

pH 10.0 9.9 9.9 10.0 10.0

T(°C) 24.5 24.8 25.4 25.4 25.5

Cf (µg/L) 29.2 29.5 29.7 30.6 31.5

Cp (µg/L) - 3.8 3.9 4.1 4.0

R (%) - 87.1 86.9 86.6 87.3

t (min) 0 60 120 180 240

pH 9.1 9.0 9.0 9.0 9.0

T(°C) 25.1 25.1 25.5 25.3 25.5

Cf (µg/L) 30.9 30.5 31.6 31.5 32.0

Cp (µg/L) - 14.1 14.4 14.6 14.8

R (%) - 54 54 54 54

66

Table B.21: Results of 30 µg/L of As(V) experiments conducted at pH=8.0 with

PES membrane.

Table B.22: Results of 30 µg/L of As(V) experiments conducted at pH=7.0 with

PES membrane.

B.6 Results of As(III) experiments with RC membrane

Table B.23: Results of As(III) experiments conducted at pH=10.0 at T=25 °C with

RC membrane (ΔP=100 kPa) (Initial concentration of feed: 31.5 µg/L).

Permeate sample no Cp (µg/L) Retention (%)

1 21.2 32.6

2 21.0 33.5

3 21.2 32.7

4 21.1 32.9

t (min) 0 60 120 180 240

pH 8.06 7.97 7.988 8.01 8.02

T(°C) 24.3 25.1 25.3 25.2 25.4

Cf (µg/L) 30.5 30.3 29.9 30.6 31.8

Cp (µg/L) - 16.9 16.6 17.2 17.8

R (%) - 44 44 44 44

t (min) 0 60 120 180 240

pH 7.0 7.0 6.9 6.9 6.9

T(°C) 24.6 24.6 25.2 24.7 25.2

Cf (µg/L) 31.8 32.3 33.0 33.0 33.9

Cp (µg/L) - 20.2 20.6 20.7 21.1

R (%) - 37 38 37 38

67

Table B.24: Results of As(III) experiments with RC membrane for As(III)

(MWCO=3 kDa) at pH=9.0 (Initial concentration of feed: 33.8 µg/L).

Permeate sample no Cp (µg/L) Retention (%)

1 24.2 28.5

2 24.4 27.9

3 24.5 27.5

4 24.2 28.3

Table B.25: Results of As(III) experiments with RC membrane for As(III)

(MWCO=3 kDa) at pH=8.0 (Initial concentration of feed: 30.3 µg/L).

Permeate sample no Cp (µg/L) Retention (%)

1 27.3 9.9

2 27.1 10.4

3 27.1 10.6

4 27.0 10.8

B.7 Results of As(V) experiments with RC membrane

Table B.26: Results of As(V) experiments conducted at pH=10.0 at T=25 °C with

RC membrane (ΔP=100 kPa) (Initial concentration: 27.9 µg/L).

Permeate sample no Cp (µg/L) Retention (%)

1 6.2 77.7

2 6.2 77.7

3 6.1 78.1

4 6.3 77.4

68

Table B.27: Results of As(V) experiments with RC membrane (MWCO=3 kDa) at

pH=9.0 (Initial concentration: 26.6 µg/L).

Permeate sample no Cp (µg/L) Retention (%)

1 6.2 76.7

2 6.4 76.1

3 6.4 76.0

4 6.4 75.9

Table B.28: Results of As(V) experiments with RC membrane (MWCO=3 kDa) at

pH=7.0 (Initial concentration: 27.7 µg/L).

Permeate sample no Cp (µg/L) Retention (%)

1 9.2 66.8

2 9.2 66.8

3 9.4 66.0

4 9.3 66.3

69

APPENDIX C

ANALYSIS DATA OF AS(III) AND AS(V) EXPERIMENTS

CONDUCTED WITH PS, PES AND RC MEMBRANES

C.1 Detailed Procedures of Analyses for the Experiments conducted

with As(III)

All analyses of As(III) experiments were conducted by following these steps

respectively;

1. Preparation of standard samples of As(III) at different concentration values.

2. Preparation of permeate and feed samples obtained in ultrafiltration

experiments. A certain quantity of hydrochloric acid (HCl) was added to all

samples to make sure all samples contain 1 M HCl (2.07 mL HCl is added to

each 22.93 mL of sample.)

3. Plotting a calibration curve for determination of As concentrations in samples

obtained from ultrafiltration experiments.

4. Determination of diluted concentration values by means of regression

equation of calibration curve.

5. Determination of actual concentration values by taking dilution ratios into

account.

70

C.2 Detailed Procedures of Analyses for the Experiments conducted

with As(V)

All analyses of As(V) experiments were conducted by following these steps

respectively;

1. Preparation of standard samples of As(V) at different concentration values

which contained 1 M HCl and certain amount of solution of KI and Ascorbic

acid for reduction of As(V) to As(III).

2. Preparation of permeate and feed samples obtained in ultrafiltration

experiments. A certain quantity of hydrochloric acid (HCl) and solution of KI

and Ascorbic acid were added to all samples (2.07 mL HCl and 0.5 mL of

solution contained 5 % KI and 5 % ascorbic acid were added to each 22.43

mL of sample.)

3. Plotting a calibration curve for determination of As concentrations in samples

obtained from ultrafiltration experiments.

4. Determination of diluted concentration values by means of regression

equation of calibration curve.

5. Determination of actual concentration values by taking dilution ratios into

account.

71

C.3 Analysis results for As(III) experiments conducted with PS

membrane

Table C.1. Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(III) at pH=11 with PS membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentratio

n

(μg/L)

5 0.0463 0.0489 0.0508 0.0487 5.8

10 0.0925 0.0922 0.0919 0.0922 11.0

20 0.1810 0.1774 0.1873 0.1819 21.7

25 0.2067 0.2117 0.2081 0.2088 24.9

30 0.2467 0.2571 0.2458 0.2499 29.7

35 0.2898 0.2897 0.2871 0.2889 34.4

y = 0.0084xR² = 0.9952

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 5 10 15 20 25 30 35 40

Ab

s

As concentration (μg/L)

Figure C.1: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(III) at pH=11 with PS membrane.

72

Table C.2: Results of the analyses for the feed samples for the experiment of 30

µg/L As(III) at pH=11 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.2429 0.2292 0.2366 0.2362 28.1 30.6

60 0.2386 0.2395 0.2407 0.2396 28.5 31.0

120 0.2389 0.2367 0.2449 0.2402 28.6 31.1

180 0.2389 0.2405 0.2442 0.2412 28.7 31.2

240 0.2493 0.2437 0.2438 0.2456 29.2 31.8

Table C.3: Results of the analyses for the permeate samples for the experiment of 30

µg/L As(III) at pH=11 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.1489 0.1478 0.1525 0.1497 17.8 19.4

120 0.1467 0.1487 0.1494 0.1483 17.7 19.2

180 0.1467 0.1494 0.1519 0.1493 17.8 19.3

240 0.1502 0.1553 0.1508 0.1521 18.1 19.7

73

Table C.4: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(III) at pH=10 with PS membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0286 0.0259 0.0289 0.0278 5.9

10 0.0492 0.0446 0.0455 0.0464 9.9

20 0.0973 0.0958 0.0958 0.0963 20.5

25 0.1171 0.1166 0.1187 0.1175 25.0

30 0.1432 0.1433 0.1469 0.1445 30.7

40 0.1879 0.1858 0.1874 0.1870 39.8

y = 0.0047xR² = 0.9988

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

0 10 20 30 40 50

Ab

s

As concentration (μg/L)

Figure C.2: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(III) at pH=10 with PS membrane.

74

Table C.5: Results of the analyses for the feed samples for the experiment of 30

µg/L As(III) at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1231 0.1221 0.1205 0.1219 25.9 28.2

60 0.1194 0.1217 0.1219 0.1210 25.7 28.0

120 0.1196 0.1186 0.1289 0.1224 26.0 28.3

180 0.1285 0.1274 0.1282 0.1280 27.2 29.6

240 0.1300 0.1308 0.1297 0.1302 27.7 30.1

Table C.6: Results of the analyses for the permeate samples for the experiment of 30

µg/L As(III) at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.0768 0.0759 0.0768 0.0765 16.3 17.7

120 0.0769 0.0792 0.0781 0.0781 16.6 18.1

180 0.0798 0.0796 0.0838 0.0811 17.2 18.7

240 0.0799 0.0818 0.0845 0.0821 17.5 19.0

75

Table C.7: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(III) at pH=9 and pH=8 with PS membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0266 0.0267 0.0276 0.0270 5.3

10 0.0530 0.0523 0.0512 0.0522 10.2

20 0.1043 0.1058 0.1046 0.1049 20.6

25 0.1275 0.1298 0.1262 0.1278 25.1

30 0.1550 0.1502 0.1528 0.1527 29.9

40 0.2120 0.2080 0.2000 0.2067 40.5

y = 0.0051xR² = 0.9995

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0 5 10 15 20 25 30 35

Ab

s

As concentration (μg/L)

Figure C.3: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(III) at pH=9 and pH=8 with PS membrane.

76

Table C.8: Results of the analyses for the feed samples for the experiment of 30

µg/L As(III) at pH=9 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1128 0.1122 0.1129 0.1126 22.1 24.0

60 0.1124 0.1131 0.1123 0.1126 22.1 24.0

120 0.1125 0.1145 0.1155 0.1142 22.4 24.3

180 0.1178 0.1167 0.1152 0.1166 22.9 24.8

240 0.1189 0.1191 0.1174 0.1185 23.2 25.2

Table C.9: Results of the analyses for the permeate samples for the experiment of 30

µg/L As(III) at pH=9 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.0726 0.0739 0.0728 0.0731 14.3 15.6

120 0.0758 0.0729 0.0739 0.0742 14.5 15.8

180 0.0739 0.0753 0.0789 0.0760 14.9 16.2

240 0.0739 0.0772 0.0824 0.0778 15.3 16.6

77

Table C.10: Results of the analyses for the feed samples for the experiment of 30

µg/L As(III) at pH=8 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1198 0.1259 0.1276 0.1244 24.4 26.5

60 0.1278 0.1295 0.1254 0.1276 25.0 27.2

120 0.1234 0.1282 0.1290 0.1269 24.9 27.0

180 0.1298 0.1270 0.1230 0.1266 24.8 27.0

240 0.1263 0.1260 0.1319 0.1281 25.1 27.3

Table C.11: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(III) at pH=8 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.1160 0.1151 0.1111 0.1141 22.4 24.3

120 0.1140 0.1108 0.1155 0.1134 22.2 24.2

180 0.1162 0.1109 0.1128 0.1133 22.2 24.1

240 0.1098 0.1165 0.1184 0.1149 22.5 24.5

78

Table C.12: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(III) at pH=7 with PS membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Calculated

concentration

(μg/L)

5 0.0287 0.0279 0.0272 0.0279 5.2

10 0.0534 0.0529 0.0541 0.0535 9.9

20 0.1124 0.1131 0.1165 0.1140 21.1

25 0.1411 0.1391 0.1525 0.1442 26.7

30 0.1647 0.1646 0.1623 0.1639 30.3

40 0.2112 0.2097 0.2087 0.2099 38.9

y = 0.0054xR² = 0.9956

0

0.05

0.1

0.15

0.2

0.25

0 10 20 30 40 50

Ab

s

As concentration (μg/L)

Figure C.4: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(III) at pH=7 with PS membrane.

79

Table C.13: Results of the analyses for the feed samples for the experiment of 30

µg/L As(III) at pH=7 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentratio

n values

(µg/L)

0 0.1672 0.1659 0.1634 0.1655 30.6 33.3

60 0.1637 0.166 0.1685 0.1661 30.8 33.4

120 0.1598 0.1678 0.1692 0.1656 30.7 33.3

180 0.1676 0.1629 0.1692 0.1666 30.8 33.5

240 0.1634 0.1614 0.1679 0.1642 30.4 33.1

Table C.14: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(III) at pH=7 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentrati

on values

(µg/L)

Actual

concentration

values (µg/L)

60 0.1562 0.1574 0.1563 0.1566 29.0 31.5

120 0.1563 0.159 0.1529 0.1561 28.9 31.4

180 0.1562 0.1572 0.1531 0.1555 28.8 31.3

240 0.1509 0.1504 0.159 0.1534 28.4 30.9

80

Table C.15: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(III) at pH=6 with PS membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0354 0.0398 0.0319 0.0357 5.1

10 0.0659 0.0608 0.0613 0.0627 9.0

20 0.1498 0.1466 0.1462 0.1475 21.1

25 0.1733 0.1691 0.1722 0.1715 24.5

30 0.2109 0.2117 0.2098 0.2108 30.1

40 0.2740 0.2771 0.2813 0.2775 39.6

y = 0.007xR² = 0.9979

0

0.05

0.1

0.15

0.2

0.25

0.3

0 10 20 30 40 50

Ab

s

As concentration (μg/L)

Figure C.5: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(III) at pH=6 with PS membrane.

81

Table C.16: Results of the analyses for the feed samples for the experiment of 30

µg/L As(III) at pH=6 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1818 0.1799 0.1794 0.1804 25.8 28.0

60 0.1833 0.1836 0.1863 0.1844 26.3 28.6

120 0.1836 0.1826 0.1859 0.1840 26.3 28.6

180 0.1829 0.1831 0.1892 0.1851 26.4 28.7

240 0.1823 0.1821 0.1879 0.1841 26.3 28.6

Table C.17: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(III) at pH=6 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.1802 0.1749 0.1736 0.1762 25.2 27.4

120 0.1753 0.1783 0.1782 0.1773 25.3 27.5

180 0.1792 0.1724 0.1792 0.1769 25.3 27.5

240 0.1754 0.1746 0.1789 0.1763 25.2 27.4

82

C. 4 Analysis results for As(V) experiments conducted with PS

membrane

Table C.18: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=11 with PS membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0445 0.0404 0.0441 0.0430 6.1

10 0.0719 0.0689 0.0729 0.0712 10.0

20 0.1494 0.1507 0.1534 0.1512 21.3

25 0.1798 0.1729 0.172 0.1749 24.6

30 0.2091 0.2182 0.2172 0.2148 30.3

40 0.2796 0.2823 0.287 0.2830 39.9

y = 0.0071xR² = 0.9976

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 10 20 30 40 50

Ab

s

As concentration (μg/L)

Figure C.6: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=11 with PS membrane.

83

Table C.19: Results of the analyses for the feed samples for the experiment of 30

µg/L As(V) at pH=11 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1970 0.1998 0.2085 0.2018 28.4 31.6

60 0.2092 0.2083 0.2073 0.2083 29.3 32.6

120 0.2025 0.2055 0.2167 0.2082 29.3 32.6

180 0.2108 0.2102 0.2127 0.2112 29.8 33.1

240 0.2102 0.2117 0.2119 0.2113 29.8 33.1

Table C.20: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(V) at pH=11 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.0211 0.0232 0.0235 0.0226 3.2 3.5

120 0.0213 0.0218 0.0232 0.0221 3.1 3.5

180 0.0209 0.0211 0.0232 0.0217 3.1 3.4

240 0.0206 0.0209 0.0218 0.0211 3.0 3.3

84

Table C.21: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=10 and pH=9 with PS membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0289 0.0284 0.0314 0.0296 4.5

10 0.0594 0.0582 0.0592 0.0589 9.1

20 0.1382 0.1405 0.1427 0.1405 21.6

25 0.1712 0.1743 0.1688 0.1714 26.4

30 0.1996 0.1991 0.2024 0.2004 30.8

41 0.2563 0.257 0.2583 0.2572 39.6

y = 0.0065xR² = 0.9937

0

0.05

0.1

0.15

0.2

0.25

0.3

0 10 20 30 40 50

Ab

s

As concentration (μg/L)

Figure C.7: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=10 and pH=9 with PS membrane.

85

Table C.22: Results of the analyses for the feed samples for the experiment of 30

µg/L As(V) at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1829 0.1892 0.1866 0.1862 28.7 31.8

60 0.1818 0.1853 0.192 0.1864 28.7 31.9

120 0.1972 0.1972 0.1988 0.1977 30.4 33.8

180 0.1952 0.1943 0.1992 0.1962 30.2 33.5

240 0.1992 0.2018 0.2049 0.2020 31.1 34.5

Table C.23: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(V) at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.0109 0.0101 0.0096 0.0102 1.6 1.7

120 0.0106 0.0109 0.0099 0.0105 1.6 1.8

180 0.0104 0.0104 0.0114 0.0107 1.7 1.8

240 0.0096 0.0095 0.0099 0.0097 1.5 1.7

86

Table C.24: Results of the analyses for the feed samples for the experiment of 30

µg/L As(V) at pH=9 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1729 0.1792 0.1866 0.1796 27.6 30.7

60 0.1768 0.1817 0.1843 0.1809 27.8 30.9

120 0.1866 0.1876 0.1823 0.1855 28.5 31.7

180 0.1945 0.1958 0.2081 0.1995 30.7 34.1

240 0.2035 0.2006 0.1984 0.2008 30.9 34.3

Table C.25: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(V) at pH=9 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.0165 0.0151 0.0159 0.0158 2.4 2.7

120 0.0166 0.0156 0.0153 0.0158 2.4 2.7

180 0.0159 0.0151 0.0163 0.0158 2.4 2.7

240 0.0173 0.0189 0.0165 0.0176 2.7 3.0

87

Table C.26: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=8 and pH=7 with PS membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0318 0.0323 0.0304 0.0315 5.4

10 0.0567 0.0532 0.0567 0.0555 9.6

20 0.1139 0.1132 0.1135 0.1135 19.6

25 0.1476 0.1498 0.1506 0.1493 25.7

30 0.1707 0.1728 0.1729 0.1721 29.7

40 0.2311 0.2305 0.2235 0.2284 39.4

y = 0.0058xR² = 0.9988

0

0.05

0.1

0.15

0.2

0.25

0 10 20 30 40 50

Ab

s

As concentration (µg/L)

Figure C.8: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=8 and pH=7 with PS membrane.

88

Table C.27: Results of the analyses for the feed samples for the experiment of 30

µg/L As(V) at pH=8 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1678 0.1659 0.1692 0.1676 28.9 32.1

60 0.1686 0.1712 0.1674 0.1691 29.1 32.4

120 0.1682 0.1666 0.1719 0.1689 29.1 32.4

180 0.1698 0.1678 0.1769 0.1715 29.6 32.9

240 0.1763 0.1764 0.177 0.1766 30.4 33.8

Table C.28: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(V) at pH=8 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.0401 0.04 0.0438 0.0413 7.1 7.9

120 0.0421 0.0427 0.0429 0.0426 7.3 8.2

180 0.0431 0.0412 0.0451 0.0431 7.4 8.3

240 0.0428 0.0437 0.0448 0.0438 7.5 8.4

89

Table C.29: Results of the analyses for the feed samples for the experiment of 30

µg/L As(V) at pH=7 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1453 0.1422 0.1462 0.1446 24.9 27.7

60 0.1460 0.1418 0.146 0.1446 24.9 27.7

120 0.1498 0.1477 0.1472 0.1482 25.6 28.4

180 0.1431 0.1427 0.1545 0.1468 25.3 28.1

240 0.1573 0.1511 0.1545 0.1543 26.6 29.6

Table C.30: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(V) at pH=7 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.0612 0.0613 0.0622 0.0616 10.6 11.8

120 0.0621 0.0657 0.0649 0.0642 11.1 12.3

180 0.0631 0.0628 0.0653 0.0637 11.0 12.2

240 0.0676 0.0665 0.0655 0.0665 11.47 12.7

90

Table C.31: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=6 with PS membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0336 0.0359 0.0369 0.0355 5.9

10 0.065 0.0653 0.0667 0.0657 10.9

20 0.1229 0.1298 0.1284 0.1270 21.2

25 0.1456 0.1482 0.1472 0.1470 24.5

30 0.1732 0.1728 0.1693 0.1718 28.6

40 0.2309 0.2387 0.2452 0.2383 39.7

y = 0.006xR² = 0.992

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0 5 10 15 20 25 30 35

Ab

s

As concentration (μg/L)

Figure C.9: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=6 with PS membrane.

91

Table C.32: Results of the analyses for the feed samples for the experiment of 30

µg/L As(V) at pH=6 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1562 0.1563 0.1502 0.1542 25.7 28.6

60 0.1521 0.1534 0.1531 0.1529 25.5 28.3

120 0.1567 0.1582 0.1532 0.1560 26.0 28.9

180 0.1539 0.1576 0.1649 0.1588 26.5 29.4

240 0.1523 0.1583 0.1668 0.1591 26.5 29.5

Table C.33: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(V) at pH=6 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.0753 0.0713 0.0758 0.0741 12.4 13.7

120 0.0763 0.0738 0.0741 0.0747 12.5 13.8

180 0.0739 0.0763 0.0777 0.0760 12.7 14.1

240 0.0743 0.0761 0.0778 0.0761 12.7 14.1

92

C.5 Analysis Results of the Experiments conducted with different

As(V) concentrations with PS membrane

Dilution of feed and permeate samples collected from ultrafiltration experiments

were needed to read more accurate absorbance values in HG-AAS. Dilution ratios for

high concentrations of arsenic were listed below:

For 100 µg/L, dilution ratio: 1:2;

For 500 µg/L, dilution ratio: 1:10;

For 1000 µg/L, dilution ratio: 1:25;

For 10000 µg/L, dilution ratio: 1:250.

Table C.34: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=10 with PS membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0266 0.0289 0.0279 0.0278 5.9

10 0.0492 0.0446 0.0455 0.0464 9.9

20 0.0973 0.0958 0.0958 0.0963 20.5

25 0.1171 0.1166 0.1187 0.1175 25.0

30 0.1432 0.1433 0.1469 0.1445 30.7

40 0.1879 0.1858 0.1874 0.1870 39.8

93

y = 0.0047xR² = 0.9988

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

0 10 20 30 40 50

Ab

s

As concentration (μg/L)

Figure C.10: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=10 with PS membrane.

Table C.35: Results of the analyses for the feed samples for the experiment of 30

µg/L As(V) at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1229 0.1392 0.1366 0.1329 28.3 31.4

60 0.1276 0.1461 0.1313 0.1350 28.7 31.9

120 0.1373 0.1324 0.1454 0.1384 29.4 32.7

180 0.1467 0.1393 0.1348 0.1403 29.8 33.2

240 0.1391 0.1394 0.1574 0.1453 30.9 34.3

94

Table C.36: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(V) at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.0073 0.0077 0.0061 0.0070 1.5 1.7

120 0.0067 0.0073 0.0089 0.0076 1.6 1.8

180 0.0062 0.0076 0.0082 0.0073 1.6 1.7

240 0.0078 0.0082 0.0078 0.0079 1.7 1.9

Table C.37: Calibration Data for analyses of feed and permeate samples for the

experiment of 100 µg/L As(V) at pH=10 with PS membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0272 0.0266 0.0252 0.0263 4.9

10 0.0502 0.0598 0.0528 0.0543 10.0

20 0.1098 0.1025 0.1023 0.1049 19.4

30 0.1529 0.1509 0.1572 0.1537 28.5

40 0.2173 0.2156 0.2202 0.2177 40.3

50 0.2715 0.2739 0.2724 0.2726 50.5

95

y = 0.0054xR² = 0.9986

0

0.05

0.1

0.15

0.2

0.25

0.3

0 10 20 30 40 50 60

Ab

s

As concentration (μg/L)

Figure C.11: Calibration curve for analyses of feed and permeate samples for the

experiment of 100 µg/L As(V) at pH=10 with PS membrane.

Table C.38: Results of the analyses for the feed samples for the experiment of 100

µg/L As(V) at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.2625 0.2730 0.2840 0.2732 50.6 101.2

60 0.2666 0.289 0.2694 0.2750 50.9 101.9

120 0.2824 0.2704 0.2861 0.2796 51.8 103.6

180 0.2816 0.2783 0.2967 0.2855 52.9 105.8

240 0.2778 0.3013 0.2932 0.2908 53.8 107.7

96

Table C.39: Results of the analyses for the permeate samples for the experiment of

100 µg/L As(V) at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.0156 0.0159 0.0168 0.0161 3.0 6.0

120 0.0169 0.0166 0.0154 0.0163 3.0 6.0

180 0.0163 0.0162 0.0157 0.0161 3.0 6.0

240 0.0163 0.0162 0.0178 0.0168 3.1 6.2

Table C.40: Calibration Data for analyses of feed and permeate samples for the

experiment of 500 µg/L, 1000 µg/L and 10000 µg/L of As(V) at pH=10 with PS

membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0323 0.0328 0.0385 0.0345 4.9

10 0.0878 0.0929 0.0552 0.0786 11.1

20 0.1596 0.1577 0.1527 0.1567 22.1

40 0.3046 0.3077 0.3040 0.3054 43.0

50 0.3449 0.3566 0.3597 0.3537 49.8

60 0.4117 0.4102 0.4144 0.4121 58.0

97

y = 0.0071xR² = 0.9944

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0 10 20 30 40 50 60 70

Ab

s

As concentration (μg/L)

Figure C.12: Calibration curve for analyses of feed and permeate samples for the

experiment of 500 µg/L, 1000 µg/L and 10000 µg/L of As(V) at pH=10 with PS

membrane.

Table C.41: Results of the analyses for the feed samples for the experiment of 500

µg/L As(V) at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.3580 0.3810 0.3570 0.3653 51.5 514.6

60 0.3610 0.3636 0.3748 0.3665 51.6 516.2

120 0.3670 0.3632 0.3895 0.3732 52.6 525.7

180 0.3826 0.3836 0.3835 0.3832 54.0 539.8

240 0.3879 0.3925 0.4012 0.3939 55.5 554.7

98

Table C.42: Results of the analyses for the permeate samples for the experiment of

500 µg/L As(V) at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.0226 0.0233 0.0232 0.0230 3.2 32.4

120 0.0216 0.0239 0.0242 0.0232 3.3 32.7

180 0.0238 0.0247 0.0252 0.0246 3.5 34.6

240 0.0216 0.0245 0.0269 0.0243 3.4 34.3

Table C.43: Results of the analyses for the feed samples for the experiment of 1000

µg/L As(V) at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.3158 0.3181 0.3257 0.3199 45.1 1126.3

60 0.3192 0.3196 0.3274 0.3221 45.4 1134.0

120 0.3167 0.3232 0.3395 0.3265 46.0 1149.5

180 0.3364 0.3404 0.3306 0.3358 47.3 1182.4

240 0.3379 0.3425 0.3412 0.3405 48.0 1199.1

99

Table C.44: Results of the analyses for the permeate samples for the experiment of

1000 µg/L As(V) at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.0265 0.0289 0.0263 0.0272 3.8 95.9

120 0.0282 0.0265 0.0273 0.0273 3.8 96.2

180 0.0249 0.0288 0.0280 0.0272 3.8 95.9

240 0.0276 0.0295 0.0289 0.0287 4.0 100.9

Table C.45: Results of the analyses for the feed samples for the experiment of 10000

µg/L As(V) at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.2958 0.2881 0.2957 0.2932 41.3 10323.9

60 0.2962 0.2845 0.2916 0.2908 41.0 10238.3

120 0.2967 0.2832 0.3095 0.2965 41.8 10439.0

180 0.3034 0.3139 0.3032 0.3068 43.2 10804.0

240 0.3079 0.3025 0.3212 0.3105 43.7 10934.3

100

Table C.46: Results of the analyses for the permeate samples for the experiment of

10000 µg/L As(V) at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.0265 0.0278 0.0261 0.0268 3.8 943.7

120 0.0276 0.0276 0.0289 0.0280 3.9 987.1

180 0.0268 0.0287 0.0282 0.0279 3.9 982.4

240 0.0276 0.0295 0.0289 0.0287 4.0 1009.4

C.6 Analysis Results of the As(V) Experiments conducted with the

presence of different anions with PS membrane

Table C.47: Calibration Data for analyses of feed and permeate samples for the

experiment of 2.15x10-7

M As(V) and 3.125x10-4

M SO42-

at pH=10 with PS

membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0331 0.0325 0.0341 0.0332 4.5

10 0.0786 0.0715 0.0691 0.0731 9.9

20 0.1596 0.1526 0.1599 0.1574 21.3

25 0.1712 0.1743 0.1688 0.1714 23.2

30 0.2108 0.2211 0.2145 0.2155 29.1

40 0.3117 0.3001 0.2946 0.3021 40.8

101

y = 0.0074xR² = 0.9947

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 10 20 30 40 50

Ab

s

As concentration (μg/L)

Figure C.13: Calibration curve for analyses of feed and permeate samples for the

experiment of 2.15x10-7

M As(V) and 3.125x10-4

M SO42-

at pH=10 with PS

membrane.

Table C.48: Results of the analyses for the feed samples for the experiment of

2.15x10-7

M As(V) and 3.125x10-4

M SO42-

at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1829 0.1892 0.1866 0.1862 25.2 28.0

60 0.1876 0.1861 0.1813 0.1850 25.0 27.8

120 0.2073 0.1924 0.1954 0.1984 26.8 29.8

180 0.2067 0.2093 0.2048 0.2069 28.0 31.1

240 0.2091 0.2094 0.2074 0.2086 28.2 31.3

102

Table C.49: Results of the analyses for the permeate samples for the experiment of

2.15x10-7

M As(V) and 3.125x10-4

M SO42-

at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.0253 0.0257 0.0261 0.0257 3.5 3.9

120 0.0277 0.0293 0.0289 0.0286 3.9 4.3

180 0.0292 0.0296 0.0282 0.0290 3.9 4.4

240 0.0298 0.0282 0.0308 0.0296 4.0 4.4

Table C.50: Calibration Data for analyses of feed and permeate samples for the

experiment of 2.15x10-7

M As(V) and 3.125x10-4

M HPO42-

at pH=10 with PS

membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0435 0.0433 0.0407 0.0425 5.2

10 0.0867 0.0870 0.0838 0.0858 10.6

20 0.1704 0.1700 0.1709 0.1704 21.0

25 0.2045 0.2027 0.2098 0.2057 25.4

30 0.2451 0.2475 0.2542 0.2489 30.7

40 0.3119 0.3163 0.3147 0.3143 38.8

103

y = 0.0081xR² = 0.997

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 10 20 30 40 50

Ab

s

As concentration (μg/L)

Figure C.14: Calibration curve for analyses of feed and permeate samples for the

experiment of 2.15x10-7

M As(V) and 3.125x10-4

M HPO42-

at pH=10 with PS

membrane.

Table C.51: Results of the analyses for the feed samples for the experiment of

2.15x10-7

M As(V) and 3.125x10-4

M HPO42-

at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.2298 0.2283 0.2172 0.2251 27.8 30.9

60 0.2290 0.2293 0.2301 0.2295 28.3 31.5

120 0.2429 0.2456 0.2423 0.2436 30.1 33.4

180 0.2471 0.2522 0.2584 0.2526 31.2 34.6

240 0.2459 0.2447 0.2574 0.2493 30.8 34.2

104

Table C.52: Results of the analyses for the permeate samples for the experiment of

2.15x10-7

M As(V) and 3.125x10-4

M HPO42-

at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.0250 0.0257 0.0274 0.0260 3.2 3.6

120 0.0265 0.0257 0.0262 0.0261 3.2 3.6

180 0.0265 0.0265 0.0275 0.0268 3.3 3.7

240 0.0271 0.0295 0.0313 0.0293 3.6 4.0

Table C.53: Calibration Data for analyses of feed and permeate samples for the

experiment of 2.15x10-7

M As(V) and 3.125x10-4

M NO3-

at pH=10 with PS

membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0391 0.0409 0.0381 0.0394 6.6

10 0.0741 0.0663 0.0698 0.0701 11.7

20 0.1311 0.1322 0.1256 0.1296 21.6

30 0.1731 0.1772 0.1703 0.1735 28.9

40 0.2439 0.2308 0.2369 0.2372 39.5

105

y = 0.006xR² = 0.9916

0

0.05

0.1

0.15

0.2

0.25

0.3

0 10 20 30 40 50

Ab

s

As concentration (µg/L)

Figure C.15: Calibration curve for analyses of feed and permeate samples for the

experiment of 2.15x10-7

M As(V) and 3.125x10-4

M NO3-

at pH=10 with PS

membrane.

Table C.54: Results of the analyses for the feed samples for the experiment of

2.15x10-7

M As(V) and 3.125x10-4

M NO3- at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1777 0.1691 0.1704 0.1724 28.7 31.9

60 0.1709 0.1711 0.1721 0.1714 28.6 31.7

120 0.1717 0.1715 0.1642 0.1691 28.2 31.3

180 0.1658 0.1678 0.1708 0.1681 28.0 31.1

240 0.1702 0.1787 0.1783 0.1757 29.3 32.5

106

Table C.55: Results of the analyses for the permeate samples for the experiment of

2.15x10-7

M As(V) and 3.125x10-4

M NO3- at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.0154 0.0166 0.0176 0.0165 2.8 3.1

120 0.0165 0.0169 0.0197 0.0177 3.0 3.3

180 0.0174 0.0181 0.0175 0.0177 2.9 3.3

240 0.0157 0.0155 0.0199 0.0170 2.8 3.2

Table C.56: Calibration Data for analyses of feed and permeate samples for the

experiment of 2.15x10-7

M As(V) and 4.840x10-4

M NO3-

at pH=10 with PS

membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0451 0.0409 0.0501 0.0454 5.4

10 0.0940 0.0973 0.0873 0.0929 11.1

20 0.1818 0.1842 0.1908 0.1856 22.1

25 0.2112 0.2143 0.2188 0.2148 25.6

30 0.2556 0.2486 0.2534 0.2525 30.1

40 0.3117 0.3136 0.3307 0.3187 37.9

107

y = 0.0084xR² = 0.9911

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 10 20 30 40 50

Ab

s

As concentration (μg/L)

Figure C.16: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) and 4.840x10-4

M NO3- at pH=10 with PS membrane.

Table C.57: Results of the analyses for the feed samples for the experiment of

2.15x10-7

M As(V) and 4.840x10-4

M NO3- at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.2377 0.2391 0.2404 0.2391 28.5 31.6

60 0.2369 0.2305 0.2458 0.2377 28.3 31.4

120 0.2486 0.2408 0.2448 0.2447 29.1 32.4

180 0.2454 0.2554 0.2496 0.2501 29.8 33.1

240 0.2502 0.2687 0.2583 0.2591 30.8 34.3

108

Table C.58: Results of the analyses for the permeate samples for the experiment of

2.15x10-7

M As(V) and 4.840x10-4

M NO3- at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.0354 0.0366 0.0376 0.0365 4.3 4.8

120 0.0365 0.0369 0.0397 0.0377 4.5 5.0

180 0.0374 0.0391 0.0375 0.0380 4.5 5.0

240 0.0447 0.0405 0.0399 0.0417 5.0 5.5

Table C.59: Calibration Data for analyses of feed and permeate samples for the

experiment of 2.15x10-7

M As(V) and 3.125x10-4

M Cl-

at pH=10 with PS

membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0317 0.029 0.0371 0.0326 5.6

10 0.0463 0.0497 0.0521 0.0494 8.5

20 0.1209 0.1222 0.1225 0.1219 21.0

30 0.1707 0.1665 0.174 0.1704 29.4

40 0.2248 0.228 0.2369 0.2299 39.6

109

y = 0.0058xR² = 0.9966

0

0.05

0.1

0.15

0.2

0.25

0 10 20 30 40 50

Ab

s

As concentration (µg/L)

Figure C.17: Calibration curve for analyses of feed and permeate samples for the

experiment of 2.15x10-7

M As(V) and 3.125x10-4

M Cl- at pH=10 with PS membrane.

Table C.60: Results of the analyses for the feed samples for the experiment of

2.15x10-7

M As(V) and 3.125x10-4

M Cl- at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1672 0.1629 0.1692 0.1664 28.7 31.9

60 0.1679 0.1628 0.1629 0.1645 28.4 31.5

120 0.159 0.1638 0.1698 0.1642 28.3 31.5

180 0.1616 0.1611 0.162 0.1616 27.9 31.0

240 0.1702 0.1787 0.1783 0.1757 30.3 33.7

110

Table C.61: Results of the analyses for the permeate samples for the experiment of

2.15x10-7

M As(V) and 3.125x10-4

M Cl- at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.0144 0.0154 0.0156 0.0151 2.6 2.9

120 0.0155 0.0159 0.0157 0.0157 2.7 3.0

180 0.0164 0.0151 0.0152 0.0156 2.7 3.0

240 0.0162 0.0167 0.0169 0.0166 2.9 3.2

Table C.62: Calibration Data for analyses of feed and permeate samples for the

experiment of 2.15x10-7

M As(V) and 8.450x10-4

Cl- at pH=10 with PS membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0501 0.0494 0.0504 0.0500 5.9

10 0.0901 0.0957 0.0942 0.0933 11.0

20 0.1769 0.1870 0.1844 0.1828 21.5

25 0.2138 0.2143 0.2098 0.2126 25.0

30 0.2354 0.2481 0.2486 0.2440 28.7

40 0.3338 0.3255 0.3487 0.3360 39.5

111

y = 0.0085xR² = 0.995

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 10 20 30 40 50

Ab

s

As concentration (μg/L)

Figure C.18: Calibration curve for analyses of feed and permeate samples for the

experiment of 2.15x10-7

M As(V) and 8.450x10-4

Cl- at pH=10 with PS membrane.

Table C.63: Results of the analyses for the feed samples for the experiment of

2.15x10-7

M As(V) and 8.450x10-4

Cl- at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.2191 0.2271 0.2238 0.2233 26.3 29.2

60 0.2204 0.2293 0.227 0.2256 26.5 29.5

120 0.2257 0.2310 0.226 0.2276 26.8 29.7

180 0.2335 0.2333 0.2345 0.2338 27.5 30.6

240 0.2442 0.2509 0.2284 0.2412 28.4 31.5

112

Table C.64: Results of the analyses for the permeate samples for the experiment of

2.15x10-7

M As(V) and 8.450x10-4

Cl- at pH=10 with PS membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.0283 0.0286 0.0296 0.0288 3.4 3.8

120 0.0303 0.0289 0.0297 0.0296 3.5 3.9

180 0.0299 0.0322 0.0319 0.0313 3.7 4.1

240 0.0320 0.0304 0.0292 0.0305 3.6 4.0

C.7 Analysis results for As(V) experiments conducted with PES

membrane

Table C.65: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=10 with PES membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0392 0.0385 0.0415 0.0397 4.8

10 0.0823 0.0831 0.0881 0.0845 10.3

20 0.1561 0.162 0.1566 0.1582 19.3

25 0.2034 0.2117 0.2186 0.2112 25.8

30 0.2504 0.2481 0.2411 0.2465 30.1

35 0.2826 0.2828 0.291 0.2855 34.8

113

y = 0.0082xR² = 0.9988

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 5 10 15 20 25 30 35 40

Ab

s

As concentration (μg/L)

Figure C.19: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=10 with PES membrane.

Table C.66: Results of the analyses for the feed samples for the experiment of 30

µg/L As(V) at pH=10 with PES membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.2235 0.2291 0.2324 0.2283 27.8 30.9

60 0.2379 0.2377 0.2318 0.2358 28.8 32.0

120 0.2386 0.2412 0.2409 0.2402 29.3 32.6

180 0.2472 0.2414 0.2497 0.2461 30.0 33.3

240 0.2401 0.2532 0.2461 0.2465 30.1 33.4

114

Table C.67: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(V) at pH=10 with PES membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.1119 0.0921 0.0927 0.0989 12.1 13.4

120 0.1021 0.099 0.0961 0.0991 12.1 13.4

180 0.1091 0.0921 0.1034 0.1015 12.4 13.8

240 0.1031 0.0912 0.1103 0.1015 12.4 13.8

Table C.68: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=9 with PES membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0403 0.0415 0.0435 0.0418 5.0

10 0.0898 0.0891 0.0921 0.0903 10.9

20 0.1681 0.1741 0.1766 0.1729 20.8

25 0.2051 0.2149 0.216 0.2120 25.5

30 0.241 0.2411 0.2461 0.2427 29.2

35 0.2919 0.2807 0.2978 0.2901 35.0

115

y = 0.0083xR² = 0.9978

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 5 10 15 20 25 30 35 40

Ab

s

As concentration (μg/L)

Figure C.20: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=9 with PES membrane.

Table C.69: Results of the analyses for the feed samples for the experiment of 30

µg/L As(V) at pH=9 with PES membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.2302 0.2375 0.224 0.2306 27.8 30.9

60 0.2279 0.2277 0.2285 0.2280 27.5 30.5

120 0.2396 0.2364 0.2328 0.2363 28.5 31.6

180 0.2329 0.2344 0.2397 0.2357 28.4 31.5

240 0.2371 0.2314 0.2486 0.2390 28.8 32.0

116

Table C.70: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(V) at pH=9 with PES membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.1037 0.1039 0.1095 0.1057 12.7 14.1

120 0.1023 0.1092 0.1123 0.1079 13.0 14.4

180 0.1082 0.1109 0.1082 0.1091 13.1 14.6

240 0.1098 0.1128 0.1092 0.1106 13.3 14.8

Table C.71: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=8 with PES membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0385 0.0402 0.0437 0.0408 4.7

10 0.0919 0.092 0.093 0.0923 10.6

20 0.1664 0.1801 0.1804 0.1756 20.2

25 0.2131 0.2124 0.2107 0.2121 24.4

30 0.2726 0.2664 0.2678 0.2689 30.9

35 0.2947 0.3009 0.3135 0.3030 34.8

117

y = 0.0087xR² = 0.9984

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 5 10 15 20 25 30 35 40

Ab

s

As concentration (μg/L)

Figure C.21: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=8 with PES membrane.

Table C.72: Results of the analyses for the feed samples for the experiment of 30

µg/L As(V) at pH=8 with PES membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.2436 0.2376 0.2342 0.2385 27.4 30.5

60 0.2299 0.246 0.2361 0.2373 27.3 30.3

120 0.2258 0.2451 0.2323 0.2344 26.9 29.9

180 0.2311 0.2478 0.2404 0.2398 27.6 30.6

240 0.2588 0.2462 0.2413 0.2488 28.6 31.8

118

Table C.73: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(V) at pH=8 with PES membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.1329 0.1279 0.1365 0.1324 15.2 16.9

120 0.1382 0.122 0.1308 0.1303 15.0 16.6

180 0.1302 0.1384 0.1359 0.1348 15.5 17.2

240 0.1329 0.1479 0.1365 0.1391 16.0 17.8

Table C.74: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=7 with PES membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0409 0.0411 0.0423 0.0414 4.8

10 0.0923 0.0889 0.0873 0.0895 10.4

20 0.1541 0.162 0.1728 0.1630 18.9

25 0.2109 0.2182 0.2179 0.2157 25.1

30 0.2629 0.2638 0.26489 0.2639 30.7

35 0.3021 0.3012 0.2918 0.2984 34.7

119

y = 0.0086xR² = 0.9982

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 5 10 15 20 25 30 35 40

Ab

s

As concentration (μg/L)

Figure C.22: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=7 with PES membrane.

Table C.75: Results of the analyses for the feed samples for the experiment of 30

µg/L As(V) at pH=7 with PES membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.2536 0.2376 0.2482 0.2465 28.7 31.8

60 0.2499 0.2546 0.2461 0.2502 29.1 32.3

120 0.2458 0.2521 0.2681 0.2553 29.7 33.0

180 0.2511 0.2529 0.2621 0.2554 29.7 33.0

240 0.2624 0.2642 0.2613 0.2626 30.5 33.9

120

Table C.76: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(V) at pH=7 with PES membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

60 0.1535 0.1539 0.1628 0.1567 18.2 20.2

120 0.1526 0.1602 0.1648 0.1592 18.5 20.6

180 0.1649 0.1604 0.1559 0.1604 18.7 20.7

240 0.1628 0.1609 0.1665 0.1634 19.0 21.1

C.8 Analysis results for As(III) experiments conducted with RC

membrane

Table C.77: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(III) at pH=10 with RC membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.021 0.02345 0.0221 0.0222 5.3

10 0.0463 0.0427 0.0451 0.0447 10.6

20 0.0879 0.0911 0.0921 0.0904 21.5

25 0.1039 0.1051 0.1072 0.1054 25.1

30 0.1287 0.1279 0.1277 0.1281 30.5

35 0.1427 0.1454 0.1404 0.1428 34.0

121

y = 0.0042xR² = 0.9962

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0 10 20 30 40

Ab

s

As concentration (μg/L)

Figure C.23: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(III) at pH=10 with RC membrane.

Table C.78: Result of the analysis for the feed sample for the experiment of 30 µg/L

As(III) at pH=10 with RC membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1175 0.1198 0.1280 0.1218 29.0 31.5

Table C.79: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(III) at pH=10 with RC membrane.

Sample

No.

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

1 0.0823 0.0831 0.0809 0.0821 19.5 21.2

2 0.0812 0.0815 0.0803 0.0810 19.3 21.0

3 0.0814 0.0826 0.0818 0.0819 19.5 21.2

4 0.0814 0.081 0.0827 0.0817 19.5 21.1

122

Table C.80: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(III) at pH=9 with RC membrane.

Concentration

of standard

solution

(μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0244 0.0255 0.0262 0.0254 4.2

10 0.0542 0.0593 0.0624 0.0586 9.8

20 0.1254 0.1285 0.1255 0.1265 21.1

25 0.1514 0.1506 0.1583 0.1534 25.6

30 0.1824 0.1867 0.1814 0.1835 30.6

35 0.2028 0.2052 0.2043 0.2041 34.0

y = 0.006xR² = 0.9968

0

0.05

0.1

0.15

0.2

0.25

0 5 10 15 20 25 30 35 40

Ab

s

As concentration (μg/L)

Figure C.24: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(III) at pH=9 with RC membrane.

123

Table C.81: Results of the analysis for the feed sample for the experiment of 30

µg/L As(III) at pH=9 with RC membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1802 0.1887 0.1908 0.1866 31.1 33.8

Table C.82: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(III) at pH=9 with RC membrane.

Sample

No.

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

1 0.1311 0.1388 0.1304 0.1334 22.2 24.2

2 0.1336 0.1358 0.1344 0.1346 22.4 24.4

3 0.1327 0.1343 0.1387 0.1352 22.5 24.5

4 0.1341 0.1339 0.1331 0.1337 22.3 24.2

Table C.83: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(III) at pH=8 and pH=7 with RC membrane.

Concentration

of standard

solution (μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0304 0.0275 0.0263 0.0281 4.8

10 0.0593 0.0575 0.0602 0.0590 10.0

20 0.1156 0.1171 0.1253 0.1193 20.2

25 0.1438 0.1418 0.1574 0.1477 25.0

30 0.1735 0.172 0.1719 0.1725 29.2

35 0.2121 0.2062 0.2047 0.2077 35.2

124

y = 0.0059xR² = 0.9993

0

0.05

0.1

0.15

0.2

0.25

0 5 10 15 20 25 30 35 40

Ab

s

As concentration (μg/L)

Figure C.25: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(III) at pH=8 and pH=7 with RC membrane.

Table C.84: Result of the analysis for the feed sample for the experiment of 30 µg/L

As(III) at pH=8 with RC membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Diluted

concentratio

n values

(µg/L)

Actual

concentration

values (µg/L)

0 0.1635 0.1614 0.1678 0.1642 27.8 30.3

Table C.85: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(III) at pH=8 with RC membrane.

Sample

No.

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

1 0.1475 0.1483 0.148 0.1479 25.1 27.3

2 0.1430 0.1469 0.1516 0.1472 24.9 27.1

3 0.1479 0.1416 0.1508 0.1468 24.9 27.0

4 0.1383 0.1477 0.1536 0.1465 24.8 27.0

125

Table C.86: Result of the analysis for the feed sample for the experiment of 30 µg/L

As(III) at pH=7 with RC membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1655 0.1535 0.1569 0.1586 26.9 29.2

Table C.87: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(III) at pH=7 with RC membrane.

Sample

No.

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

1 0.1557 0.1509 0.1579 0.1548 26.2 28.5

2 0.1516 0.154 0.1633 0.1563 26.5 28.8

3 0.1571 0.1537 0.1541 0.1550 26.3 28.5

4 0.1543 0.1521 0.1598 0.1554 26.3 28.6

126

C.9 Analysis results for As(V) experiments conducted with RC

membrane

Table C.88: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=10 with RC membrane.

Concentration

of standard

solution (μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.031 0.034 0.035 0.0333 5.1

11 0.0786 0.0727 0.0722 0.0745 11.3

20 0.1312 0.136 0.1421 0.1364 20.7

25 0.1729 0.1702 0.1757 0.1729 26.2

30 0.1848 0.1875 0.1864 0.1862 28.2

35 0.2359 0.2256 0.2272 0.2296 34.8

y = 0.0066xR² = 0.9948

0

0.05

0.1

0.15

0.2

0.25

0 5 10 15 20 25 30 35 40

Ab

s

As concentration (μg/L)

Figure C.26: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=10 with RC membrane.

127

Table C.89: Result of the analysis for the feed sample for the experiment of 30 µg/L

As(V) at pH=10 with RC membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1643 0.1633 0.1687 0.1654 25.1 27.9

Table C.90: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(V) at pH=10 with RC membrane.

Sample

No.

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

1 0.0371 0.0365 0.0364 0.0367 5.6 6.2

2 0.0357 0.0368 0.0371 0.0365 5.5 6.2

3 0.0374 0.0356 0.0364 0.0365 5.5 6.1

4 0.0385 0.0365 0.0373 0.0374 5.7 6.3

Table C.91: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=9 with RC membrane.

Concentration

of standard

solution (μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0225 0.0237 0.0239 0.0234 5.0

10 0.0471 0.0486 0.0483 0.0480 10.2

20 0.0999 0.0975 0.0992 0.0989 21.0

25 0.1254 0.1217 0.1235 0.1235 26.3

30 0.1409 0.1341 0.1355 0.1368 29.1

35 0.1546 0.159 0.1574 0.1570 33.4

128

y = 0.0047xR² = 0.9941

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0 5 10 15 20 25 30 35 40

Ab

s

As concentration (μg/L)

Figure C.27: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=9 with RC membrane.

Table C.92: Result of the analysis for the feed sample for the experiment of 30 µg/L

As(V) at pH=9 with RC membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1106 0.1104 0.1171 0.1127 24.0 26.6

Table C.93: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(V) at pH=9 with RC membrane.

Sample

No.

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

1 0.0262 0.0261 0.0263 0.0262 5.6 6.2

2 0.0268 0.0278 0.0261 0.0269 5.7 6.4

3 0.0261 0.0272 0.0277 0.0270 5.7 6.4

4 0.0267 0.0279 0.0269 0.0272 5.8 6.4

129

Table C.94: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=8 with RC membrane.

Concentration

of standard

solution (μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0318 0.0327 0.033 0.0325 4.9

10 0.0639 0.0603 0.0649 0.0630 9.6

20 0.1347 0.1439 0.1357 0.1381 20.9

25 0.1699 0.1721 0.1701 0.1707 25.9

30 0.1919 0.194 0.1951 0.1937 29.3

35 0.2215 0.2261 0.2341 0.2272 34.4

y = 0.0066xR² = 0.9975

0

0.05

0.1

0.15

0.2

0.25

0 5 10 15 20 25 30 35 40

Ab

s

As concentration (μg/L)

Figure C.28: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=8 with RC membrane.

130

Table C.95: Result of the analysis for the feed sample for the experiment of 30 µg/L

As(V) at pH=8 with RC membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1523 0.1688 0.1551 0.1587 24.1 26.7

Table C.96: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(V) at pH=8 with RC membrane.

Sample

No.

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

1 0.0394 0.0394 0.0385 0.0391 5.9 6.6

2 0.0382 0.0398 0.0394 0.0391 5.9 6.6

3 0.0386 0.0395 0.0407 0.0396 6.0 6.7

4 0.0397 0.0402 0.0411 0.0403 6.1 6.8

Table C.97: Calibration Data for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=7 with RC membrane.

Concentration

of standard

solution (μg/L)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average of

abs read

values

Calculated

concentration

(μg/L)

5 0.0319 0.0327 0.0347 0.0331 5.0

10 0.0584 0.0563 0.0605 0.0584 8.8

20 0.1346 0.1363 0.1334 0.1348 20.4

25 0.1644 0.1629 0.1611 0.1628 24.7

30 0.1993 0.1999 0.1937 0.1976 29.9

35 0.2270 0.2296 0.2303 0.2290 34.7

131

y = 0.0066xR² = 0.9985

0

0.05

0.1

0.15

0.2

0.25

0 5 10 15 20 25 30 35 40

Ab

s

As concentration (μg/L)

Figure C.29: Calibration curve for analyses of feed and permeate samples for the

experiment of 30 µg/L As(V) at pH=7 with RC membrane.

Table C.98: Result of the analysis for the feed sample for the experiment of 30 µg/L

As(V) at pH=7 with RC membrane.

Time

(min)

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

0 0.1634 0.1608 0.1695 0.1646 24.9 27.7

Table C.99: Results of the analyses for the permeate samples for the experiment of

30 µg/L As(V) at pH=7 with RC membrane.

Sample

No.

Abs read

value 1

Abs read

value 2

Abs read

value 3

Average

of abs

read

values

Diluted

concentration

values (µg/L)

Actual

concentration

values (µg/L)

1 0.0547 0.0549 0.0545 0.0547 8.3 9.2

2 0.0543 0.0552 0.0543 0.0546 8.3 9.2

3 0.0554 0.0567 0.0557 0.0559 8.5 9.4

4 0.0557 0.0545 0.0561 0.0554 8.4 9.3