A comparison on adsorption and Biodegradation abilities Between activated carbon fiber (acf) and granular activated Carbon (gac)

In terms of drinking water purification and wastewater reclamation technologies, adsorption and biodegradation have attracted attention due to their treatment efficie[r]

VIETNAM NATIONAL UNIVERSITY, HANOI

VIETNAM JAPAN UNIVERSITY

VIETNAM NATIONAL UNIVERSITY, HANOI

VIETNAM JAPAN UNIVERSITY

ACKNOWLEDGEMENT

During the period of conducting the thesis, I have received a lot of valuable guidance and support that helped me to complete and attain new knowledge and wonderful experiences With all my respect and gratitude, I would like to express my sincere appreciation to:

I would like to express my deep gratitude to my supervisors, Dr Tran Thi Viet Ha and Prof Ikuro Kasuga for their kindly support and great advices went throughout

my period of carring out my thesis Their encouragement and scientific knowledge have inspired me and helped me a lot in improving research and completing my Master thesis

I would like to express my very great appreciation to Dr Sato Keisuke for his valuable support in sharing chemical and apparatus

I would like to thank Ms Iftita Rahmatika, for her continuous assistance and encouragement, who always helped and supported my experiments in Tokyo, Japan

I wish to thank Ms Ngoc for her assistance in doing experiment of bacteria abundance in Vietnam

I would like to extend my thanks to the technicians of the MEE laboratory (Ms Huong) for her help in offering me the resources in running the progress of my research

My special thanks approve to all teachers and professors in MEE program for the arrangments and supports for everything that was needed for my research activity

I wish to thank Japan International Cooperation Agency (JICA), VNU Vietnam Japan University (VJU) and The University of Tokyo (UoT) for giving me international studying environment

Finally, thanks go out to all my friends and my family for their continuous assistance and encouragement

TABLE OF CONTENTS

ACKNOWLEDGEMENT i

LIST OF TABLES iv

LIST OF FIGURES v

LIST OF ABBREVIATIONS vii

INTRODUCTION 1

Background 1

Objectives 3

Thesis structure 3

CHAPTER 1 LITERATURE REVIEW 5

1.1 Applications of ACF to environmental protection 5

1.1.1 Application of ACF to water/wastewater 5

1.1.2 Application of ACF to removal of contaminants from air 6

1.2 Application of GAC to environmental protection 7

1.2.1 Applications of GAC to Drinking Water Treatment 7

1.2.2 Applications of GAC to Wastewater Treatment 12

1.3 Methyl orange (MO) 17

1.4 Ammonia 18

CHAPTER 2 MATERIAL AND METHODS 21

2.1 Material 21

2.2 Material characterization 21

2.2.1 SEM (scanning electron microscopy) and Energy Dispersive X-ray spectroscopy (EDX) 21

2.2.2 BET ((Brunauner - Emmett - Teller) 22

2.2.3 pHpzc 24

2.3 Adsorption abilily evaluation 24

2.3.1 Batch adsorption study of MO onto ACF/GAC 24

2.3.2 Column adsorption study of MO onto ACF/GAC 27

2.4 Biological study of B-ACF/B-GAC 29

2.4.1 B-ACF/B-GAC fabrications 29

2.4.2 Bacteria abundance associated with B-ACF/B-GAC 30

2.4.3 Nitrification Potential Test 32

CHAPTER 3 RESULTS AND DISCUSSIONS 34

3.1 Characteristics of ACF and GAC 34

3.1.1 SEM and EDX 34

3.1.2 BET area 36

3.1.3 pHpzc 37

3.2 A comparison of adsorption ability between ACF and GAC 38

3.2.1 Batch experiment 38

3.2.2 Column experiment 47

3.3 A comparison of biodegradation ability between B-ACF and B-GAC 49

3.3.1 Bateria Abundance 49

3.3.2 Nitrification potential test 50

CONCLUSION AND RECOMMENDATION 54

REFERENCE 56

LIST OF TABLES

Table 1.1 Methyl orange properties 17 Table 3.1 The element present in materials 35 Table 3.2 The BET result of ACF and GAC 36 Table 3.3 Kinetic parameters by linear regression method for MO adsorption onto

ACF/GAC (pH= 7, MO concentration= 20 mg/L, Volume of MO= 100mL, amount

of adsorbent= 0.65g, contacting time= 3 hours, temperature= 20 0C) 39

Table 3.4 Adsorption isotherm summarize of MO adsorption onto ACF/GAC (Ci =

50÷500 mg/L) adsorbent dose = 6.5 g/L, shaking speed = 120 rpm, contacting time =

Table 3.7 Adsorption summary of nitrite, nitrate, and ammonia onto ACF/GAC (V

= 100mL, shaking speed = 120 rpm, temperature 20 0C) 51

LIST OF FIGURES

Figure 1.1.The first version of Mu¨lheim process operated in Styrum-West, Dohne,

and Kettwig Water Worksư 8

Figure 1.2 The treatment flow chart of the Leiden full-scale and pilot scale plants 9 Figure 1.3 The treatment scheme of reclaimation plant in Windhoek, Namibia 12

Figure 1.5 Chemical structure of MO 17

Figure 1.6 Removal methodologies of organic dyes, as well as MO 18

Figure 2.1 Calibration curve of methyl orange 25

Figure 2.2 ACF/GAC column system for MO adsorption 28

Figure 2.3 The procedure of total cell counts by flow cytometer 30

Figure 2.4 Schematic of the three main components of a flow cytometer 31

Figure 2.5 Petri dish 32

Figure 3.1 SEM images of ACF 34

Figure 3.2 SEM images of GAC 35

Figure 3.3 Adsorption and desorption isotherms of N2 onto ACF and GAC 37

Figure 3.4 pHpzc of GAC and ACF was carried out with solution NaNO3 0.1N in pH range of 2–11 37

Figure 3.5 Linear forms of adsorption kinetic of MO onto ACF/GAC (a) Pseudo- first order (b) Pseudo- second order (pH= 7, Ci= 20 mg/L, adsorbent dose= 6.5 g/L, shaking speed= 120 rpm, contact time= 3 hours, temperature= 20 0C) 38

Figure 3.6 Adsorption isotherm of MO onto ACF/GAC (pH= 7, Ci= 50÷500 mg/L, adsorbent dose= 6.5 g/L, shaking speed= 120 rpm, contact time= 3 hours, temperature= 303K, 313K, 323K) 41

Figure 3.7 The plot of ln(𝐾𝑑) versus 1/T 42

Figure 3.8 (a) Effect of initial MO concentration on the adsorption of MO by ACF/GAC (adsorbent dose= 650 mg/100 mL, temperature= 30oC, contacting time= 3 hours, and pH= 7); (b) Effect of adsorbent dosages on the adsorption of MO by ACF/GAC (MO concentration= 20mg/L, Solution volume= 100 mL, temperature= 30oC, contacting time =3 hours, and pH = 7) 44

Figure 3.9 Linear forms of Pseudo- second order adsorption kinetic of MO onto ACF/GAC, correspondent with pH (pH= 3, 5, 7, 9, 11; Ci = 20 mg/L, adsorbent dose= 6.5 g/L, shaking speed= 120 rpm, contacting time= 3 hours, temperature= 20 0C) 46

Figure 3.10 The breakthrough curve of ACF and GAC 48

Figure 3.11 Area breakthrough curve of ACF and GAC 48

Figure 3.12 Linear forms of column adsorption of ACF/GAC following Thomas model 49

Figure 3.13 Attached bacteria abundance in ACF/GAC biofilms (a) FCM method in

Japan (b) cultivation on R2A agar in Vietnam 50

Figure 3.14 (a) Nitrification potential test on B-ACF with West Lake water (

Vietnam); (b) Linear forms of the first order reaction of ammonia reduction on ACF with West Lake water 51

B-Figure 3.15 The gap of amount of nitrite, nitrate, or ammonia between day 0 and

day 1 of B-ACF and B-GAC with West Lake water, Vietnam 52

Figure 3.16 The ammonia oxidation capacity ( 200 mL artificial ammonium solution

1mg N-NH4+/L, contacting time: 5 days) 52

LIST OF ABBREVIATIONS

1,2-DCA 1,2-dichloroethane

ABS Acrylonitrile Butadiene Styrene

ACF Activated Carbon Fiber

AOA Ammonia Oxidizing Archaea

AOC Assimilable Organic Carbon

AOX Adsorbable Organic Xenobiotics (Halogens)

BAC Biological Activated Carbon (mostly used for GAC)

BDOC Biodegradable Dissolved Organic Carbon

BTEX Benzene, Toluene, Ethylbenzene, Xylene

BTX Benzene, Toluene, P-Xylene

B-ACF Biological Activated Carbon Fiber (ACF combined biofilm) B-GAC Biological Granular Activated Carbon (GAC combined biofilm) CMF-S Submerged Microfiltration Technology

COD Chemical Oxigen Demand

DOC Dissolved Organic Carbon

EBCT Empty-Bed Contact Time

EDCs Endocrine-Disrupting Compounds

EDX Energy Dispersive X-ray spectroscopy

GAC Granular Activated Carbon

GAC-FBR GAC-based Fluidized-Bed Reactors

GAC-UASB Upflow Anaerobic Sludge Blanket

HPC Heterotrophic Plate Count

PPCPs Pharmaceutical and Personal Care Products

pzc The point of zero charge

SEM Scanning Electron Microscopy

INTRODUCTION

Background

Recently, many types of carbon materials have been developed and they are widely used for environmental protection such as water/wastewater treatment and removal

of contaminants from air

They are divided into three major groups including (i) conventional carbon, (ii) newly developed carbons, and (iii) natural diamond (Hassani and Khataee, 2017; Michio Inagaki et al., 2013)

Activated carbon fiber (ACF), which is belong to the newly developed carbon group,

has two aspects of activated carbon and carbon fiber ACF is commercialy produced

by heating organic precusors in an oxidizing atmosphere (Lee et al., 2014), and it is

frequently in the form of cloth, felt, and non-woven Granular activated carbon

(GAC) which is belong to the conventional carbon group, is commonly in the form

of crushed granules of coals or shell GAC used in water treatment plants today is produced mostly from various kinds of natural coal It is able to be prepared by granulation of pulverized powders using binders such as coal tar pitch The dimension

of GAC particles ranges from 0.2 to 5 mm (Suzuki, 1990)

In terms of drinking water purification and wastewater reclamation technologies, adsorption and biodegradation have attracted attention due to their treatment efficiency and cost-effectiveness, on which, activated carbon, especially GAC, is commonly used as a kind of adsorbent and a bacteria carrier (Jin et al., 2013; Rattier

et al., 2012) while the potential of ACF in this field has been rarely explored

In order to assess the potential of ACF in water/wastewater treatment applications, a comparison of adsorption and biodegradation abilities between ACF and GAC was conducted

Adsorption is a crucial phenomenon in most natural physical, biological, and

chemical processes Adsorption can take place between two phases, such as gas-solid,

or liquid-solid interfaces The solid/adsorbing phase is the adsorbent, and subtances adsorbed at the surface of adsorbent is the adsorbate (Hattori et al., 2013)

Biodegradation can be described as the breakdown of organic/inorganic compounds

resulting from organisms such as bacteria and fungi (Dungani et al., 2018)

In this study, methyl orange (MO), an azo organic dye, was used to evaluate the

adsorption performance of ACF and GAC Organic dyes are widely used in many different industries such as sewing, leather, cosmetics, paper, and pharmaceuticals

In 2003, dyes were produced more than 7× 10! tonnes Among those, azo dyes are mostly utilized due to the synthesis is easier and more cost-effective than that of natural dyes (Pearce et al., 2003) According to data from the Vietnamese General Department of Customs in 2018, the group of textiles and garments is the second-largest export group with a value of $ 30.49 billion in 2018 increasing 16.7% compared to 2017 (VnEconomy, 2018) It means that a large amount of wastewater containing dyes, especially synthetic organic dyes, has been discharged Those dyes are extreamly harmful to the environment because they can cause physiological disturbances of aquatic organisms due to the consumption of dyes through the food chain (Karthikeyan et al., 2006) In addition, almost azo dyes are toxic, carcinogenic, and mutagenic (Pinheiro et al., 2004) such as causing bladder cancer in humans and changing chromosomes in mammalian cells (Medvedev et al., 1988; Percy et al., 1989) Also, they impart colour to the water, leading to aesthetic issues (Akpan and Hameed, 2009; Van Der Zee and Villaverde, 2005)

Regarding the biodegradation evaluation, bacteria abundance of ACF and GAC, and

nitritrification test were carried out Nitrification is a biological process of ammonia

oxidation and nitrite oxidation, of which, oxidation of ammonia by nitrifiers is concerned as an important and rate-limiting stage (Ward, 2006; You et al., 2009)

Ammonia is mainly in the form of ammonium in raw water, which reduces the effect

of chlorination and takes action as a precursor of trichloramine leading to an unpleasant odor and taste to drinking water (Huang, 2008) Hence, controlling ammonia is an important requirement in advanced drinking water purification process and wastewater reclaimation for the potable purpose in developed countries

Objectives

In order to evaluate the potential of ACF for water/wastewater treatment applications,

a comparison of adsorption and biodegradation abilities between ACF and GAC were

carried out The main objectives of this study are

• Comparing the adsorption performance of ACF and GAC, using MO as target

pollutant

• Comparing biodegradation ability including micro organism carrying capacity

and nitrification of B-ACF and B-GAC

Thesis structure

This thesis includes 4 chapters

Chapter 1 is literature review The purpose of this chapter is to demonstrate an

overview of ACF and GAC applications, especially applications to environmental

protection In addition, MO and ammonia are introducted

Chapter 2 is materials and methods Its purpose is to introduce materials and describe

the methods of conducting experiments and data evaluation

Chapter 3 shows results and discussions on 3 issues including material

characterization, adsorption ability evaluation, and biological study Material

characterization part is to point out a material's structure and properties The second

part shows a comparision of the MO adsorption performance between GAC and ACF

in batch and column experiments Adsorption kinetic, adsorption isotherm,

adsorption thermodynamic and several impact factors were shown Finally, a

comparison of biodegradation between B-ACF and B-GAC including bacteria

abundance and ammonia oxidation is discussed

Chapter 4 is to sum up the achievement of the thesis and recommendation

A COMPARISON ON ADSORPTION AND BIODEGRADATION ABILITIES BETWEEN ACTIVATED CARBON FIBER (ACF) AND

GRANULAR ACTIVATED CARBON (GAC)

CHAPTER 3 RESULTS AND DISCUSSIONS

3.1 Characteristics of ACF and GAC

3.2 A comparison of adsorption ability between ACF and GAC

3.2.1 Batch experiment

3.2.2 Column experiment

3.3 A comparison of biodegradation ability between B-ACF and B-GAC

3.3.1 Bateria Abundance

3.3.2 Nitrification potential test

CONCLUSION AND RECOMMENDATION

INTRODUCTION

CHAPTER 1

LITERATURE REVIEW

CHAPTER 2 MATERIALS AND METHODS

CHAPTER 1 LITERATURE REVIEW

1.1 Applications of ACF to environmental protection

ACF has been applied as an adsorbents for gas phase and liquid phase adsorption to remove contaminants from water/wastewater and from air

1.1.1 Applications of ACF to water/wastewater

ACF was frequently used as adsorbents to remove contaminants from water and wastewater The adsorption ability of commercial ACF was verified in several pulished studies For example, adsorption efficiency of diuron (667± 9 mg/g), ammitrole (51±4 mg/g) (López-Ramón et al., 2007), dibenzothiophene (270mg/g) (Kumagai et al., 2010), fluroxypur (807±10 mg/g) (Pastrana-Martínez et al., 2009) using ACF were reported A pesticides adsorption onto ACF with high surface area

of 2500 m2/g was also studied It was showed that the adsorption process fitted well with the Langmuir and Freundlich isotherm models (Ayranci and Hoda, 2005) In other study, ACF prepared from coconut shell and then activated with several chemicals was used to remove trivalent chromium Cr (III) from tannery wastewater The adsorption of Cr (III) on ACF followed pseudo-second order kinetic model and Langmuir isotherm model (Mohan et al., 2006)

Additionally, ACF with high electrical conductivity is possible for electroadsorption

or electrochemical degradation and photoelectro-Fenton applications in removal of contaminants from water/wastewater It was reported that removal of phenol using electroadsorption on ACF was increased between 0.2 and 2.3 mmol/g by applying a bias potential from 0 to 700 mV after 10 hours contacting time (Han et al., 2006) The electrochemical adsorption and desorption of acid orange 7 on ACF was conducted using 30.0 mg ACF in 1 mmol/L acid orange 7 solution at the polarized potential of 0, 200, 400, and 600 mV (Han et al., 2008) It showed the highest performance of acid orange 7 removal at the polarization potential of 600 mV Besides, the ACF were regenerated if a potential of -5 V was applied

ACF used as an electrode for the electrochemical degradation of amaranth under galvanostatic conditions showed higher removal performance compared

to electrooxidation (Fan et al., 2006) It indicated that ACF was better than graphite

as the role of a cathode for the electro-Fenton degradation of the azo dye cationic red X-GRL (Lei et al., 2010)

Furthermore, ACF combined with photocatalyst was used for removal of pollutants from water/wastewater For instance, TiO2/ACF composite prepared using epoxy demonstrated higher removal performance of methylene blue than that for fresh commercial TiO2 (Yuan et al., 2005) An electrochemical degradation of methylene blue onto TiO2/ACF composites also showed higher removal efficiency as compared

to TiO2 (Oh and Chen, 2008) TiO2 loaded ACF in a pulsed discharge reactor showed higher MO removal efficiency (98.2%) than that of ACF/ TiO2 alone (61.3%) or pulsed discharge alone (63.0%) ZOCF, another composite of ZnO and carbon fiber, with an electrochemical deposition method displayed a high adsorption performance (245.07 mg/g) for removal of Pb (II) metal from water (Zhang et al., 2010)

Moreover, many researchs verified a good performance of modified ACF in adsorption For instance, Mn/ACF displayed 36.53 mg/g adsorption capacity of arsenic As (V) (Sun et al., 2013) HNO3/ACF showed adsorption performance of aniline (244.2 mg/g), phenol (164.8 mg/g) and pyridine (145.8 mg/g) (Li et al., 2010) ACF prepared from commercial acrylic textile fibers and modified with powdered sulfur or H2S gas was showed a high capacity (290-710 mg/g) of mercury adsorption from aqueous solutions (Nabais et al., 2006) ACF coated with silver became

an antibacteria material which could against Staphylococcus aureus and Escherichia

coli (Oya et al., 1993)

1.1.2 Applications of ACF to removal of contaminants from air

Beside application on water/wastewater treatment, ACF was also used for air pollutants treatment The potential of ACFs in this field has been studied for removal

of SO2 (Daley et al., 1997; Kisamori et al., 1994), removal of NO and NO2 (Mochida

et al., 1997) in air environment The efficiency of pitch-based ACFs was also evaluated for the removal of SOx and NOx (Mochida et al., 2000) Pitch-based ACF, which was prepared by heat treatment in nitrogen at temperatures ranging between

600 0C and 900 0C, showed the highest reduction of SOx in the presence of water at

25 0C The reduction of NOx from the atmosphere to N2 was obtained by using based ACF with a mixture of the TiO2 and urea ACF with impregnation and

pitch-precipitation with an aqueous solution of metal salts was successful for the catalytic conversion of NO into N2 (Olsson et al., 2008; Ouzzine et al., 2008; Peña et al., 2004) Further, volatile organic compounds (VOCs) are air pollutants and generated from industrial and domestic activities It is considered as an crucial contributor to the indoor air quality reduction They consits of toxic compounds such as aromatics and aliphatics VOCs causes negative impacts on human health such as eye and throat irritation, damage to the liver, and central nervous system disorders Recently, ACF has been explored (Cal et al., 1996; Huang et al., 2002; Yu and Chou, 2000) ACF also displayed high adsorption of benzene (4 mmol/g) and toluene (6 mmol/g) at low concentration (200 ppmv) (Lillo-Ródenas et al., 2011)

Futhermore, nonwoven fabrics have been ultilised to adsorb sound and noise aramid paper attached to nonwoven fabric showed a higher sound absorption capacity compared to glass wool (Kosuge, 2005) The polyester and polypropylene nonwoven selvages recycled were applied to sound adsorption (Lou et al., 2005)

Para-1.2 Applications of GAC to environmental protection

This part focused on applications of GAC and BAC (GAC associated with biofilm)

to water and wastewater treatment GAC adsorption is widely applied to reduce the concentration of trace organics compounds for drinking water treatment, treatment of wastewater, and landfill leachates If GAC receives water containing microorganisms,

it is possible for bacteria to develop on GAC, leading to biofilm formation ozonation

or advanced oxidation processes is commonly applied for the removal of pollutants These techniques enhance the effect of biodegradation development in water/wastewater

1.2.1 Applications of GAC to Drinking Water Treatment

In order to remove organic compounds such as DOC (Dissolved Organic Carbon), taste and odor, pesticides, and the adsorbable halogenated organics, the oxidation process followed by BAC filtration has been widely applied for both surface water and groundwater treatments for the drinking purpose

1.2.1.1 The treatment of surface water sources

An example of GAC application to potable water treatment from surface water is Mu¨lheim plant in Germany (Bundermann, 2006) At begining, it was an original biofiltration process developed mainly for the removal of DOC It showed an effective reduction in organic, inorganic, and microbiological parameters including DOC, turbidity, ammonia, nitrite, nitrate, HPC (Heterotrophic Plate Count),

coliforms, E coli, parasites, and pesticides from Ruhr river’s water The first version

of the Mu¨lheim process was shown in Figure 1.1 The second version which was modified from the first version of Mu¨lheim process was applied at the Styrum East Water Works The Ruhr river water first passed through slow sand filtration and artificial groundwater recharge Then, the water was undergone ozonation, biological double layer, and BAC filtration Finally, UV-light and NaOH were used for disinfection and deacidification the water, respectively

Figure 1.1.The first version of Mu¨lheim process operated in Styrum-West, Dohne,

and Kettwig Water Worksư (Bundermann, 2006) Another example could be mentioned is the Leiden plant in Amsterdam, Netherlands

A two-stage BAC filtration was used for the reduction of specific organics including AOX (Adsorbable Organic Xenobiotics), DOC, pesticides, and micropollutants from Rhine river water (Bonné et al., 2002) The flow chart of the treatment was shown in Figure 1.2 Initially, GAC of the full-scale plant needed to be reactivated frequency

18 months, according to the removal performances of those organics To evaluate the remaining removal ability and the breakthrough profile of carbon filters,a pilot system receiving pretreated water was conducted in parallel to the full-scale plant In

this pilot test, GAC was not reactivated during 4 years of operation Although carbon reactivation was not applied, the filter effluent still reached standards (DOC < 2 μg /L; AOX < 5 μg /L) After 4 years of operation with 2 μg /L of initial concentration,

no pesticide breakthrough was seen in the BAC filtration Among tested pesticides, atrazine showed the most consistent reduction Moreover, it was observed that a running period of 3 years between two reactivations is obtainable with no negative effect on the finished water Another results showed that after 2 year operation, the average value of DOC concentration would rise from 1 mg/L up to 1.2 mg/L After 4 years of operation, the AOC concentration would be equal to or lower than 10 μg C/L after BAC filtration If slow sand filtration was set up, AOC could be reduced to less than 10–5 μg C/L

Figure 1.2 The treatment flow chart of the Leiden full-scale and pilot scale plants

(Bonné et al., 2002) The plants with capacities between 240,000 and 800,000 m3/day in the Suburbs of Paris, France also used the combination of BAC filters and an ozonation system for river waters treatment (Servais et al., 2002) The treatment scheme of these plants consists of flocculation and settling, rapid sand filtration, ozonation, BAC filtration, and final disinfection using chlorine In the ozonated water, the DOC and BDOC concentrations were from 1.74–2.29 mg/L and 0.40–0.48 mg/L, respectively BAC

filtration reduced the BDOC content by 0.19–0.27 mg/L It was also concluded that GAC should be regenerated after several working years to remain the adsorption function of organic matter

In several countries, such as the Netherlands and Switzerland, potable water is treated without chlorine disinfection, which can cause bacteria to the re-growth problem if degradable organic matter enters to the water distribution system Thus, the limitation

of degradable organic matter in finished water is necessary An example for such case

is the treatment plant at Weesperkarspel, Netherlands (Van Der Helm et al., 2009) Before water (seepage water of the Bethune polder, sometimes mixed with Amsterdam-Rhine Canal) is transported to Weesperkarspel plant, it is undergone the pretreatment in Loenderveen including coagulation and sedimentation, self-purification in a lakewater reservoir and rapid sand filtration At Weesperkarspel plant, the first unit is ozonation to break down complex organic matter aiming at rising the biodegradability of NOM BAC filtration is the next step to remove NOM and organic micropollutants Finally, slow sand filtration is applied for the removal

of suspended solids and nutrients This process acted as a second barrier in the treatment against pathogens and especially remove persistent pathogens with low susceptibility to ozone The water in this treatment plant contained mainly humic substances (70% of the total DOC) It is mainly reduced by coagulation (30%) and

by BAC filtration (42%), implying that biodegradation is the main part (Baghoth et al., 2009) Low-molecular-weight (LMW) acids are not found in the raw water, but these compounds can be formed by ozonation They were greatly reduced by softening, BAC filtration, and SS filtration

Drinking water treatment plants (Bendigo, Castlemaine, and Kyneton) in Victoria, Australia, used microfiltration, ozone, and BAC filtration The plant in Bendigo with

a capacity of 126 Milion L/day applied submerged microfiltration technology S), the Kyneton plant with 8 Milion L/day, and Castlemaine plant with 18 Milion L/day utilized conventional CMF designs (Veolia Water Australia Pty Limited 2010) The raw water from reservoirs was screened After that, it is dosed with lime and carbon dioxide to stabilize the water to prevent corrosion Then, coagulation is introduced to remove particulates, metal, and color Microfiltration is applied to

(CMF-remove particulates down to 0.2 mm and to ensure the reduction of Cryptosporidium and Giardia contamination Ozonation followed by BAC filtration was utilized to aim

at removing taste and odor compounds and blue-green algae toxins, leading to quality stable water For pH control and corrosion protection, adding lime to water

high-is carried out The final step high-is dhigh-isinfection with chlorination in order to guarantee the quality of finished water for distribution

1.2.1.2 The treatment of ground water sources

The adsorption and biodegradation by GAC are also utilized for groundwater treatment GAC-based fluidized-bed reactors (GAC-FBR) are usually applied in aerobic or anoxic conditions for the treatment of groundwaters which are polluted with petroleum hydrocarbons and pentachlorophenol, respectively (Sutton and Mishra, 1994)

Longhorn Army Ammunition Plant in Texas used a full-scale GAC-FBR to treat the groundwater polluted with high concentrations of perchlorate ranging from 11,000 to 23,000 μg/L with a flow rate of 274 m3/day (Polk et al., 2001) In this case, perchlorate was reduced to chloride under anoxic conditions with an electron donor

of acetic acid Perchlorate concentration after being treated by full-scale GAC-FBR was less than 4 μg/L (Polk et al., 2002)

Another example is plant in Rancho Cordova It applied two full-scale GAC-FBR reactors for treatment of groundwater with a capacity of 3,240 m3/day Perchlorate concentrations was declined from 6–7 mg/L to 4–40 μg/L in the presence of methanol

as the electron acceptor (Greene and Pitre, 1999)

BAC reactors were also applied for the removal of various chlorinated organics from groundwater (Stucki and Thüer, 1994) At first, two full-scale abiotic GAC reactors were used for the treatment of 240–360 m3/day groundwater polluted with 20 mg/L 1,2-dichloroethane (1,2-DCA) The effluent treated by GAC obtained a concentration

of 1,2-DCA less than 10 mg/L which is the required standard After that, these reactors were changed to BAC reactors by incubation with microorganisms that are able to mineralize 1,2-DCA Appropriate conditions were provided by adding nutrients and hydrogen peroxide to reactors Hydrogen peroxide acted as an oxygen

source to avoid stripping of 1,2-DCA The effluent treated by BAC has also achieved the required limit of 1,2-DCA However, the service life BAC was expanded more than 40-fold compared to abiotic GAC reactors

1.2.2 Applications of GAC to Wastewater Treatment

GAC adsorption is usually used in tertiary treatment of municipal and industrial wastewater and landfill leachates with the main target of removing trace organics compounds from secondary effluents

1.2.2.1 Reclamation of wastewater for potable uses

The reclamation of domestic wastewater for the drinking purpose is a resolution for

the water scarcity in arid regions In 2002, a reclamation plant with a capacity of

21,000 m3/day was built in Windhoek, Namibia (Menge, 2010) The treatment scheme containing BAC and GAC units is shown in Figure 1.3 In this case, COD and DOC was not decreased by ozonation unit but UV254 reduced 36%, implying that ozonation could degrade large aromatic compounds, but total mineralization was not reached The combination of BAC and GAC units decreased COD to 10 mg/L in total

Figure 1.3 The treatment scheme of reclamation plant in Windhoek, Namibia

(Menge, 2010)

1.2.2.2 Reclamation of wastewaters for nonpotable uses

Continuous-flow laboratory-scale BAC columns were applied for the secondary effluent treatment of Pasakoy Advanced Wastewater Treatment Plant in Istanbul, Turkey (Kalkan et al., 2011) During the first 83 days of operation, 65–81% of DOC was removed by BAC filters After breakthrough was obtained, DOC removal performance declined to 38–46% by biodegradation Nitrification and denitrification were also 52–54% of total nitrogen removal In order to reuse the treated water, it is recommended that BAC followed by disinfection should be set up at the full-scale domestic wastewater treatment plants

In a pilot test in China, in order to achieve the standards of water reuse for various purposes from secondary domestic effluent, ozonation followed by BAC was carried out in the Beishiqiao wastewater purification center of Xi’an municipality (Wang et al., 2002) Ozonation removed only 12% of the initial TOC Moreover, ozonation oxidized nonbiodegradable substances, leading to an increase in the ratio of biodegradable DOC (BDOC) to total DOC (from 0.28 to 0.6) It supported BAC to increase an additional 35% removal of COD BAC filtration reduced COD in the secondary effluent from 20 mg/L to 5 mg/L

The South Caboolture Water Reclamation Plant in Queensland, Australia with a capacity of 10,000 m3/day was contructed to reduce river pollution and reuse water for nonpotable uses In fact, the water after treatment met standards for drinking purposes (van Leeuwen et al., 2003) The treatment scheme included biological denitrification, preozonation, coagulation/flocculation, dissolved air flotation/sand filtration, ozonation, and BAC filtration Preozonation played an important role in converting refractory organic compounds into biodegradable organic compounds, which could increase the service life of activated carbon Four open gravity BAC beds were designed as a depth of 2.2 m, an empty-bed contact time (EBCT) of 18 min and a total bed surface area of 13 m2 After being treated 36% in BAC filters, value of mean COD from the effluent achieved about 12.8 mg/L

Furthermore, BAC filters could be applied for recycling or reuse of industrial wastewaters For example, BAC systems were assessed to recycle and reuse in five textile factories in Iraq (Abud et al., 2006) The treated water from the factories was

to recycle 80% and reuse 20% for secondary uses BAC filters could reduce 63–87%

of COD content and exceeding 80% of color

In another study, BAC filtration for removal of organic micropollutants (MPs) from secondary effluent of municipal water for recycling was investigated in terms of adsorption and biodegradation (Rattier et al., 2012) BAC showed good results for removal of dissolved organic carbon (40%) and MPs (60–95%) Further, adsorption and biodegradation of 20 compounds were evaluated by inhibiting the biomass with azide GAC could adsorb 88 ± 5% removal of these compounds with no influence of

azide BAC could remove 72 ± 15%, but the efficiency decreased to 59 ± 20% after azide addition

1.2.2.3 Treatment of sewage for reuse in agriculture

A wastewater treatment plant was constructed in Australia for a population of 11,000 aim at reuse in a dairy farm (Boake, 2005) The flow diagram of the treatment plant was shown in Figure 1.4 The major idea in this design is reduction of pesticides and endocrine-disrupting compounds (EDCs) concentrations before reuse of treated water First, the BioDenipho (biological process) followed by sand filtration process was to remove organic carbon, biological nitrogen and phosphorus from raw sewage After that, advanced treatment including ozonation, BAC filtration, microfiltration, and disinfection was carried out Ozonation played a role in the reduction of COD and organic nitrogen remaining after biological treatment BAC filtration is used to degrade the compounds that were more enable to biological removal after ozonation

Figure 1.4 The treatment scheme of Gerroa sewage treatment plant for water reuse

(Boake, 2005)

1.2.2.4 Treatment of petrochemical wastewater

A moving bed BAC reactor associated with ozonation was used to treat petrochemical industrial wastewater containing acrylonitrile butadiene styrene (ABS) (Lin et al., 2001) It showed that COD removal performance ranged from 70% to 95%, and the service life of the BAC bed was significantly longer than the GAC bed In another research, Granular Activated Carbon-Fluidized-Bed Reactor (GAC-FBR) system which was applied for oilfield wastewater treatment demonstrated that removal efficiencies were 99% for BTEX (Benzene, Toluene, Ethylbenzene, Xylene), 74% for COD, 94% for total volatile hydrocarbons (TVH), 94% for oil at initial COD, BTEX, TVH, and oil concentrations of 588, 17.7, 64, and 72 mg/L, respectively (Allen, 2008)

1.2.2.5 Treatment of textile wastewaters

BAC reactor dominated by the bacteria Pseudomonas putida was applied to color

removal of a simulated aqueous discharge from a carpet printing plant comprising a mixture of acid dye (Walker and Weatherley, 1999) GAC and artificial foundry sand set up in an up-flow biological aerated filter were used for secondary textile wastewater treatment (Liu et al., 2008) GAC-UASB (upflow anaerobic sludge blanket) employed for the wastewater treatment of a carpet dyeing factory with COD (9000 mg/L) and BOD5 (1500 mg/L) showed nearly 80% efficiency (Kuai et al., 1998)

1.2.2.6 Treatment of various toxic contaminants

Aim at limiting volatile organic compounds (VOCs), the most common adsorbent is GAC (VanOsdell et al., 1996) In addition, GAC associated with biofilm was employed BAC system of a pilot-scale GAC-FBR removed more than 99% of total BTEX without releasing these volatile compounds to the atmosphere (Hickey et al., 1990) The GAC-FBR (fluidized bet reactor) system showed significantly higher removal efficiency of BTX (benzene, toluene, p-xylene) compared to nonactivated carbon FBR (Zhao et al., 1997) An aerobic BAC reactor degraded 5 mg/L 1,2-dichloroethane (1,2-DCA) with removal efficiency of 95%, while 1,2-DCA was not efficiently adsorbed on activated carbon Besides, GAC with biological activation

developed the service life of GAC from 20 days to 170 days (Stucki and Thüer, 1994)

Nitrophenols are used in the production of dyes, phytochemicals, pesticides, wood preservatives, explosives, and leather treatment Textile and pesticide manufacturing release large wastewater containing nitrophenols like m-nitrophenol (MNP) and p-nitrophenol (PNP) which are toxic to human and animals The BAC using bacteria

of Pseudomonas putida was able to remove almost completely 100 mg/L MNP and

150 mg/L PNP after nearly 16h (Escobar et al., 2008)

GAC was supplemented to an activated sludge reactor to enhance the removal performance of organic micropollutants from Pharmaceutical and Personal Care Products (PPCPs) (Serrano et al., 2010)

In lab scale, BAC could remove nearly 97% of DOC from a secondary sewage effluent (Xing et al., 2008) However, secondary effluents also contain specific pollutants such as dibutyl phthalate, bis (2-ethylhexyl) phthalate, 4-bromo-3-chloroaniline and other phenol derivatives which are not able to be removed by the conventional activated sludge process By pretreatment with TiO2/UV/O3, several aromatic compounds including 2,4-dichloro-benzenamine, 4-bromo-3-chloroaniline, and 3,5-dimethoxyacetophenone disappeared, while some easily biodegradable compounds consisting of 1,3-cyclohexanediamine, 9-octadecenamide, tert-butyldimethylsilanol, and phenol were formed (Li et al., 2005), which could be greatly removed by subsequent BAC system

100 mg/L of 3-chlorobenzoate, thioglycolic acid or a combination of both were removed 95% by GAC-SBR/BAC-SBR (Jaar and Wilderer, 1992) It also showed higher removal performance compared to the GAC continuous-flow operation system

An expanded-bed anaerobic BAC reactor was applied to treat an industrial wastewater containing 1,1,1-trichloroethane (TCA), acetic acid and phenol (Suidan

et al, 1991) The reactor showed a good removal performance with exceeding 99.4 %

of TAC at 20–430 mg/L concentration, more than 93 % of acetic acid and 99 % of phenol at high concentration

Cyanide (CN), usually in the form of metal complexes and harmful to humans, is often found in wastewater from various industries such as metal finishing, mining, coke plants, petroleum refining, explosives manufacture, pesticide production, and

so on A study showed GAC dominated Pseudomonas fluorescence was utilized for

the removal of ferrocyanide, a complex of cyanide (Dash et al., 2008) GAC in this reactor is not only an adsorbent to adsorb cyanide, but also a carrier of bacteria to biodegrade cyanide The combination of adsorption and biodegradation showed cyanide removal efficiency ranged from 70 to 99% for cyanide concentrations of 50–

300 mg/L It demonstrated a higher removal performance than biodegradation (69.3–96.4%) and adsorption (50.2–85.6%) worked separately

Hydrogen sulfide (H2S) is a main odorous contaminant in sewage air High H2S removal performance (97–99.9%) was obtained by GAC with immobilizing

bacterium Thiomonas sp (Koe, L and Tong, 2005) Also, GAC dominated by

sulfide-oxidizing bacteria showed at the removal exceeded 98% with an input H2S concentration of 200–4000 mg/L (Rattanapan et al., 2009)

1.3 Methyl orange (MO)

MO has an azo bond (R-N=N-R) that is resistant to breakdown in environment and stable in acidic and alkaline conditions The characteristic and chemical structure of

MO were shown in Table 1.1 and Figure 1.6, respectively (Pubchem, n.d.)

Figure 1.5 Chemical structure of MO (Pubchem, n.d.)

Table 1.1 Methyl orange properties (Pubchem, n.d.)

Methyl orange Formula C14H14N3NaO3S

Applications Detecting microorganisms; treating dermatological

diseases, vaginal affections; dental materials; wound dressing materials

Liquid crystals, thin films, sensors, sol-gel matrix, waveguides, host-guest chemistry, display device,

corrosion inhibitor, glass coatings, paints, wound dressing materials, pharmaceuticals, dental materials, measuring nucleic acid

Figure 1.6 Removal methodologies of organic dyes, as well as MO (Fernández et

al., 2010)

Figure 1.6 demonstrated the general methodologies for the removal of organic dyes,

as well as MO (Fernández et al., 2010) Among of many methods, adsorption is usually used in removal of dye compound because it is easy and cheap to conduct

1.4 Ammonia

Ammonia is mainly in the form of ammonium in raw water It could cause negative

effects on environments and human health

For example, it is able to cause lung edema, nervous system dysfunction, acidosis, and kidney damage for animals if they expose the amount of LD50 of 350–750 mg/kg

of body weight through oral intake or a single dose of 200–500 mg/kg of body weight The human could be disturbed the glucose tolerance and reduced the tissue

sensitivity to insulin if he/she exposes a dose of more than 100 mg NH4Cl/(kg body weight.day) with a pathway of oral intake (WHO/SDE/WSH/03.04/01, 1996)

In addition, ammonia is one of the factors hindering the water treatment technology such as reducing the effect of chlorination, reducing the effectiveness of disinfection

in water due to chlorine forming mono-chloramine as a secondary antiseptic (Huang, 2008) The reactions between chlorine and ammonia/ammonium forming various chloramines that reduce significantly the disinfecting ability are represented as follows:

NH3 + HOCl ⇋NH2Cl + H2O

NH2Cl+ HOCl ⇋NHCl2 + H2O NHCl2 + HOCl ⇋NCl3 + H2O Besides, ammonia along with trace elements in the water is "food" for bacteria to grow that affects water quality after treatment such as make water cloudy and sediment in the pipe system (Huang, 2008; P.Q.Nhân, 2008) Polluted lakes, in which algal blooms are abundant, the concentration of ammonia is measured in the range of 0.18–2.0 mg NH3-N/L (Yang et al., 2010)

In Vietnam, according to Department of Water Resources Management, groundwater has been increasingly polluted with ammonia (Phạm Quý Nhân, 2008) In another study, it showed that ammonia is a factor causing supplied water pollution The average ammonia‘s concentration of water to in supplying pipes connecting to householes is 10.96 mg NH3-N/L much higher than 0.3 mg NH3-N/L, acceptable amount of ammonia according to QCVN 01-1:2018/BYT-National technical regulation on Domestic Water Quality in Vietnam (Bộ Y Tế, 2018; Lê Anh Trung, Đồng Kim Loan, 2016)

Ammonia was almost completely removed by nitrification which contains two processes including ammonia oxidation and nitrite oxidation according to the following stoichiometry equations:

NH3 + 1.5 O2 → NO2- + H+ + H2O

NO2- + 0.5 O2 → NO3-

Recently, it has been known that ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA) are concerned as the dominant microorganism and play the key role in the ammonia oxidation process (Ferrera and Sánchez, 2016; Schleper and Nicol, 2010) Thus, to enhance nitrification, it is important to provide good conditions for the growth of these microorganisms Several impact factors including ammonia content, temperature, organic loading, oxygen, and pH must be considered (Yin et al., 2018)

Several papers pointed out the ability of GAC in ammonia oxidation and bacteria abundance on GAC, especially AOA (ammonia oxidizing archaea) (Kasuga et al., 2010; Niu et al., 2013) Further, a study was carried out to evaluate the removal efficiency of nitrification correspondent with temperature in pilot-scale test and full-scale plant (Andersson et al., 2001) The ammonia concentration of influent water ranged from 0.020 to 0.120 mg NH4-N/L and 0.4 mg NH4-N/L in full-scale operation and pilot-scale test, respectively At tempererture higher than 10oC, ammonia removal ranged between 40% and 90% in pilot filters, but exceeded 90% in full-scale filters At temperatures ranging from 4 to 10 0C, ammonia removal varied from 10 %

to 40% of for pilot tests packed with open-superstructure GAC and superstructure GAC In full-scale filters, ammonia removal exceeded 90% with open-superstructure GAC, but it was nearly 45% with closed-superstructure GAC At temperatures below 4 0C, the removal performance was below 30% for both the pilot and full-scale The study also demonstrated that the attachment and detachment of nitrifiers play the key role in nitrification

closed-From literature, GAC has been commonly used for drinking water purification and wastewater reclamation technologies in full scale while ACF has been rarely explored

Therefore, in order to evaluate the potential of ACF in water/wastewater treatment applications, a comparison of adsorption and biodegradation abilities between ACF and GAC was conducted For adsorption test, methyl orange was selected as target pollutants and ammonia was chosen for nitrification potential test

CHAPTER 2 MATERIAL AND METHODS

In this technique, a fine probe of electrons with energies of up to 40 keV is concentrated on a sample and scanned along a parallel line Various signals released

by the action of incident electrons are collected to form an image or to analyze sample surfaces These are mainly secondary electrons, with energies of a few tens of eV, high-energy electrons backscattered from the primary beam and characteristic X-rays Lens aberrations and source brightness affect the resolution in SEM In order to improve the SEM resolution, there are two main ideas including declining the lens aberrations, or rising the source brightness The aberrations could be decreased by enhancing lens design, and by improving electro-optical correcting devices However, in recent years, the development of high brightness sources has played a key role in the improvement in SEM resolution (Bogner et al., 2007)

In this study, SEM images of ACF and GAC were measured with Real 3D system Keyence VE 8800 and JSM-7500FA JEOL

The ACF/GAC samples were dried and coated with metal (Pt) with Magnetron Sputter MSP-1S before being subjected to the Real 3D system Keyence VE 8800 By JSM-7500FA JEOL, we could obtain high-resolution and high-magnification images

of ACF/GAC specimens without coating In parallel, the energy dispersive X-ray spectroscopy was utilized to identify the presence of atom and ratio of C/O in ACF/GAC

2.2.2 BET (Brunauner - Emmett - Teller)

In 1938, the first paper of the BET theory was published by Stephen Brunauer, Paul Hugh Emmett, and Edward Teller (Brunauer et al., 1938) Its purpose is to describe the physical adsorption of gas molecules on a solid surface Then, it used as a basis for a measurement of the specific surface area of a material

In the BET instrument, the specific surface area and pore size of a solid specimen were determined by the physical adsorption of an inert gas such as argon, krypton, or nitrogen forming a monomolecular layer attaching on the sample's surface (Barron, 2020; Hwang and Barron, 2011)

There are many BET analysis apparatus such as Micromeritics, Quantachrome, and Porous Materials, Inc In this research, 0.5 g of dried ACF/GAC was subjected to BET equipment which is Quantachchrome TouchwinTM version 1.22 - NOVA touch 4LX with adsorbate of nitrogen The regents or chemicals for equipment include liquid nitrogen, helium gas (99.9% pure), nitrogen gas (99.99% pure) The instrument consits of vacuum system (10-4 Torr), heating apparatus, pressure gauge, sample holder (bulb) of known volume, precise laboratory balance

Before analysis, the sample was cleaned and dried and should be de-gassed for at least 1 hour This could be conducted by attaching the tube (sample holder tube) to a vacuum pump with heating (100–110 °C) to generate water vapor, or usually carried out with the BET instrument

When the sample was ready, the analysis was carried out by the BET instrument The samples were immersed in liquid nitrogen while the instrument conducts the gas nitrogen adsorption During the test, the instrument introduced pure nitrogen gas into the tube and recorded the pressure (P/Po)

After that, BET surface area could be calculated by the host computer connected its system to as equation 2.1 and 2.2

1𝑉(-𝑃"

of adsorbate gas in equilibrium with the surface at 77.4 K in pascals Vm is the volume

of gas adsorbed at STP to produce an apparent monolayer on the sample surface, in milliliters C is a dimensionless constant that is related to the enthalpy of adsorption

of the adsorbate gas on the powder sample

N is Avogadro constant (6.022 × 1023 mol-1)

a is the effective cross-sectional area of one adsorbate molecule, in square metres (0.162 nm2 for nitrogen and 0.195 nm2 for krypton)

22400 is the volume occupied by 1 mole of the adsorbate gas at STP allowing for minor departures from the ideal, in milliliters

m is mass of the sample

The value of Vm is calculated with a linear form of equation 3.1 by ploting between

# range 0.05 to 0.3 The data are considered acceptable if the correlation coefficient, r,

of the linear regression is not less than 0.99; that is, r2 is not less than 0.99 Then, the specific surface area calculated from the value of Vm by Equation 2.2

2.2.3 pHpzc

The point of zero charge (pHpzc) is used to evaluate the surface charge of adsorbents

which vary according to pHpzc (Zhao et al., 2016) It is commonly used to examine

the surface science of materials It plays important role in determining how easily a material could adsorb potentially harmful ions (Bakatula et al., 2018; Zalac and Kallay, 1992) It also has various applications in the technology of colloids such as flotation of minerals

pHpzc values of GAC and ACF and GAC was carried out with 100 mL solution NaNO3 0.1N with pH range of 2–11, material amount of 0.5g, and shaking speed of

120 rpm in 24 hours pHi were values of NaNO3 0.1N before adding materials pHf

were values of NaNO3 0.1N after 24 hours adding materials The graphs of pHpzc were plotted with pHi and the differences of pHf and pHi (pHf - pHi )

Values of pH were adjusted with HNO3 0.1N and NaOH 0.1N pH was measured by

pH meter (Mettler Toledo Seven-compact) pH-meter was calibrated with NBS buffers before every measurement

2.3 Adsorption abilily evaluation

2.3.1 Batch adsorption study of MO onto ACF/GAC

Adsoprtion abilities of ACF and GAC for an aqueous solution of MO (MO,

C14H14N3NaO3S) were tested The effects of different temperatures, pH, and adsorbent doses on adsorption capacity of MO were investigated The stock solution was made by dissolving MO in double distilled water Concentration of MO was identified by measureing absorbance at 464nm of a UV/Vis spectrophotometer (UV–Visible spectrophotometer, Unico S-2150, USA) All adsorption experiments were carried out in triplicate, and the mean values were used in data analysis Calibration curves of MO were obtained by preparing dilution series of MO (0, 1.0, 3.0, 4.0, 5.0, 8.0 mg MO/L) as figure 2.1

Figure 2.1 Calibration curve of methyl orange

Kinetic experiments were performed by shaking 100 ml of 20 mg/L MO solution with 0.65 g of ACF/GAC at 120 rpm at 20 °C The experiment was conducted for 3 hours until the equilibrium condition was obtained when no further decline in the MO concentration was found Two milliliters of the sample was collected regularly over time

Adsorption isotherm and adsorption thermodynamic were also evaluated From that, effect of temperature was also assessed It was carried out by shaking 100 ml MO with initial MO concentrations ranging of 10-500 mg/L at 30, 40 and 50 °C, pH=7 in

3 hours

Effect of initial MO concentration

The initially tested concentrations of MO were evaluated 50, 100, 150, 250 and 500 mg/L at 30 °C at pH 7 Dosage of ACF/GAC was fixed at 0.65 g

Effect of ACF/GAC dosage

The effect of ACF/GAC dosage was investigated by changing the dosage from 0.1g

to 1g at 20 °C at pH 7 The initial MO concentration was 20 mg/L

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

C (mg/L)

sodium hydroxide (0.1 N) pH of the dye solution was measured by pH meter (Mettler Toledo Seven-compact) pH-meter was calibrated with NBS buffers before every measurement

Data Evaluation

The amount of MO adsorbed onto the ACF/GAC at equilibrium, 𝑞. (mg/g), was

calculated by the following equation:

𝑞/ =𝑉 ∗ (𝐶"− 𝐶/)

𝑤

(Equation 2.5)

where 𝐶/ (mg/L) is the concentrations of the MO at time t

To predict the mechanism of adsorption of MO onto GAC/ACF, several kinetic models including pseudo-first order, pseudo-second order, and intraparticle diffusion models were applied The linear forms of the these models equation are given as follows:

Pseudo-first order (ho y.s, 2004):

𝑙𝑛(𝑞. − 𝑞/) = −𝑘%𝑡 + 𝑙𝑛𝑞. (Equation 2.6) Pseudo-second order (Ho, 2006):

𝑞. and 𝑞/(mg/g) are the adsorption capacities at equilibrium and at a time t, respectively, and 𝑘% (𝑚𝑖𝑛*%) and 𝑘0 (g/mg.min) are the rate constants of pseudo-first order adsorption and the pseudo-second, respectively

Moreover, Freundlich and Langmuir isotherm models were applied to analyze the experimental data

The linear form of the Freundlich isotherm equation is given as follows:

The linear form of the Langmuir isotherm equation is given as follows:

of adsorbate for adsorbent Furthermore, to indicate the favorable adsorptive uptake

of adsorbent, the dimensionless equilibrium parameter was calculated as follows:

2.3.2 Column adsorption study of MO onto ACF/GAC

The column with an inner diameter of 3 cm and a height of 30 cm (Vcolume is about

210 mL), and made from acrylic plastic was used With the same column’s volume,

37 g of ACF or 105 g of GAC was needed to fill it up The porosity of ACF and GAC column systems were estimated as 70.59% and 41.81%, respectively It was