DYES ADSORPTION ON SALAK PEEL BASED ACTIVATED CARBON: OPTIMIZATION,
EQUILIBRIUM, KINETIC AND THERMODYNAMIC STUDIES
NUR IZZATUL AKMAL MOHD ZAKI
UNIVERSITI SAINS MALAYSIA
2015
DYES ADSORPTION ON SALAK PEEL BASED ACTIVATED CARBON:
OPTIMIZATION, EQUILIBRIUM, KINETIC AND THERMODYNAMIC STUDIES
by
NUR IZZATUL AKMAL MOHD ZAKI
Thesis submitted in fulfillment of the requirements for the degree of
Master of Science
October 2015
ii
ACKNOWLEDGEMENT
First and foremost, I would like to convey my sincere gratitude to my supervisor, Associate Professor Dr. Mohd Azmier Ahmad for his precious encouragement, guidance and generous support throughout this work. I would also like to extend my thanks to Associate Professor Dr. Suffian Yusoff for his support.
I would like to extend my gratitude towards all the MSc and PhD students for their kindness cooperation and helping hands in guiding me carrying out the lab experiment. They are willing to sacrifice their time in guiding and helping me throughout the experiment besides sharing their valuable knowledge.
Apart from that, I would also like to thank all SCE staffs for their kindness cooperation and helping hands. Indeed, their willingness in sharing ideas, knowledge and skills are deeply appreciated.
I would like to express deepest thankful to financial support by MYBRAIN, Knowledge Transfer Programme Grant and USM Waste Management Cluster Grant.
I would also like to extend my appreciation to my parent, my husband, Mr. Shahrul Hafez and my daughter, Ayesha Humaira for their unending support and love.
Once again, I would like to thank all the people, including those whom I might have missed out and my friends who have helped me directly or indirectly.
Their contributions are very much appreciated. Thank you very much.
Nur Izzatul Akmal Mohd Zaki October 2015
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TABLE OF CONTENTS
Page
ACKNOWLEDGEMENT ii
TABLE OF CONTENTS iii
LIST OF TABLES vii
LIST OF FIGURES ix
LIST OF PLATES xi
LIST OF SYMBOL xii
LIST OF ABBREVIATIONS xiii
ABSTRAK xiv
ABSTRACT xv
CHAPTER ONE: INTRODUCTION 1
1.1 Textile industries and dye effluent 1
1.2 Treatment of industrial dye effluent 1
1.3 Problem statement 2
1.4 Scope of Study 3
1.5 Research objectives 4
1.6 Organization of thesis 4
CHAPTER TWO: LITERATURE REVIEW
2.1 Dyes 6
2.2 Adsorption 7
2.3 Activated carbon 9
iv
2.4 AC precursor 10
2.5 Salak peel based activated carbon (SPAC) 11
2.6 Adsorption isotherms 11
2.6.1 Langmuir isotherm 12
2.6.2 Freundlich isotherm 13
2.6.3 Temkin isotherm 14
2.7 Adsorption kinetics 15
2.7.1 Pseudo-first-order model 15
2.6.2 Pseudo-second-order model 16
2.8 2.9
Adsorption thermodynamic Design of experiment (DoE)
2.9.1 Response surface methodology (RSM) 2.9.2 Central composite design (CCD) 2.9.3 Analysis of data
17 19 19 20 23
CHAPTER THREE: MATERIALS AND METHODS
3.1 Materials 25
3.2 Equipment and instrumentation 26
3.2.1 Preparation of SPAC 26
3.2.2 Characterization system 28
3.2.3 Dyes concentration 29
3.2.4 Batch adsorption system 29
3.3 3.4
Experiment design for preparation of SPAC Experimental procedures
30 32
3.4.1 Preparation of SPAC 32
v
3.4.2 Preparation of stock and dye solutions 33
3.4.3 Sample analysis 33
3.4.4 Batch equilibrium, kinetics and thermodynamics studies 34 3.4.4(a) Effect of initial dye concentration and contact
time
35
3.4.4(b) Effect of solution temperature 36 3.5 Experimental activities
CHAPTER FOUR: RESULTS AND DISCUSSIONS 4.1 Experimental design
4.1.1 MG removal of SPAC 4.1.2 RBBR removal of SPAC 4.1.3 SPAC yield
4.1.4 Optimization of operating parameters
36
37 42 43 44 46
4.2 Characterization of SPAC 47
4.2.1 Surface area and pore characteristics 47
4.2.2 Surface morphology 48
4.2.3 Proximate analysis 49
4.3 Batch adsorption studies of MG and RBBR on SPAC 49
4.3.1 Batch equilibrium studies 49
4.3.1(a) Effect of initial dye concentration and contact time
49
4.3.1(b) Effect of solution temperature 52
4.3.2 Adsorption isotherms 53
vi
4.3.3 Batch kinetics studies 56
4.3.4 Adsorption thermodynamics studies 59
CHAPTER FIVE: CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusions 61
5.2 Recommendations 62
REFERENCES 63
APPENDICES
vii
LIST OF TABLES
Page Table 2.1 Classification of dyes based on applications 6 Table 2.2 Pollutants from dyeing processing operations (Babu et
al., 2007).
7
Table 2.3 Advantages and limitations of dyes removal methods (Crini, 2006)
8
Table 2.4
Table 2.5
Comparison of adsorption capacities of AC prepared from agrowastes
Central composite designs (Tobias and Trutna, 2006)
10
22 Table 3.1 Properties of MG (Sigma-Aldrich, 2012) 25 Table 3.2 Properties of RBBR (Sigma-Aldrich, 2012) 26 Table 3.3 Independent variables and their coded levels for the
CCD
31
Table 3.4 Experimental design matrixes 31
Table 4.1 Experimental design matrix for preparation of SPAC 38
Table 4.2 ANOVA for MG removal by SPAC 40
Table 4.3 ANOVA for RBBR removal by SPAC 41
Table 4.4 ANOVA for SPAC yield 41
Table 4.5 Model validation for MG and RBBR removal 46
Table 4.6 Model validation for SPAC yield 47
Table 4.7 Surface area and pore characteristic of the samples 47
Table 4.8 Proximate analysis of the samples 49
Table 4.9 Isotherms parameters for MG dyes adsorption at 30°C 56
viii Table 4.10
Table 4.11 Table 4.12 Table 4.13
Isotherms parameters for RBBR dyes adsorption at 30°C Kinetic parameters for MG dyes adsorption at 30°C Kinetic parameters for RBBR dyes adsorption at 30°C Thermodynamic parameters for MG and RBBR dyes adsorption
56 56 57 60
ix
LIST OF FIGURES
Page Figure 2.1 Three type of central composite design (Halim, 2008) 21 Figure 3.1
Figure 3.2
Schematic diagram of the experimental setup Schematic flow diagrams of experimental activities
27 36 Figure 4.1 Three-dimensional response surface plot of MG
removal by (a) effect of activation temperature and time, IR = 2.00; (b) effect of activation time and IR, temperature = 700°C of SPAC
42
Figure 4.2 Three-dimensional response surface plot of RBBR removal by (a) effect of activation temperature and time, IR = 2.00; (b) effect of activation temperature and IR, t = 2h of SPAC
43
Figure 4.3 Three-dimensional response surface plot of SPAC yield (a) effect of activation temperature and time, IR = 2.00;
(b) effect of activation temperature and IR, time = 2h
45
Figure 4.4 SEM micrograph of SPAC (magnification: 10k x) 48 Figure 4.5 Dyes adsorption uptake versus adsorption time at
various initial concentration at 30°C for (a) MG and (b) RBBR
50
Figure 4.6 Dyes adsorption uptake versus initial concentration at different temperatures for (a) MG and (b) RBBR.
52
Figure 4.7 MG dye adsorption onto SPAC at 30oC, 45oC and 60oC for (a) Langmuir; (b) Freundlich and (c) Temkin
54
x
Figure 4.8 RBBR dye adsorption onto SPAC at 30oC, 45oC and 60oC for (a) Langmuir; (b) Freundlich and (c) Temkin
55
Figure 4.9 Linearized plots of (a) pseudo-first-order and (b) pseudo-second-order models at 30oC for MG dye solution
57
Figure 4.10
Figure 4.11
Linearized plots of (a) pseudo-first-order and (b) pseudo-second-order models at 30oC for RBBR dye solution
Plot of lnk2 versus 1/T for (a) MG; and (b) RBBR dyes adsorption
58
60
xi
LIST OF PLATES
Page
Plate 3.1 Stainless steel vertical furnace 27
Plate 3.2 UV-visible spectrometer (UV-1800 Shimadzu, Japan) 29
Plate 3.3 Water-bath shaker 30
xii
LIST OF SYMBOL
Symbol Unit
A Arrhenius factor -
BT Constant for Temkin equation -
C Boundary layer -
Ce Equilibrium concentration of adsorbate mg/L
Co Highest initial adsorbate concentration mg/L
Ct Dye concentration at time, t mg/L
E Mean free energy J/mol
Ea Arrhenius activation energy of adsorption kJ/mol k1 Adsorption rate constant for the pseudo-first-order
kinetic
1/min
k2 Adsorption rate constant for the pseudo-second-order g/mg.min kdiff Intraparticle diffusion rate constant mg/g.min1/2
KF Freundlich isotherm constant mg/g (L/mg)1/n
KL Rate of adsorption for Langmuir isotherm L/mg
M Mass of adsorbent G
nF Constant for Freundlich isotherm -
qe Amount of adsorbate adsorbed at equilibrium mg/g qm Adsorption capacity of Langmuir isotherm mg/g qt Amount of adsorbate adsorbed at time, t mg/g
R Universal gas constant 8.314 J/mol K
R2 Correlation coefficient -
RL Separation factor -
T Time Min
T Absolute temperature K
V Solution volume L
ΔH° Changes in standard enthalpy kJ/mol
ΔS° Changes in standard entropy kJ/mol
ΔG° Changes in standard Gibbs free energy kJ/mol
Λ Wavelength Nm
xiii
LIST OF ABBREVIATIONS AC Activated carbon
ANOVA Analysis of variance BET
CCD CO2
Brunauer-Emmett-Teller Central composite design Carbon dioxide
FTIR Fourier Transform Infrared
IUPAC International Union of Pure and Applied Chemistry MG
N2
Malachite green Nitrogen gas RBBR
SEM STA
Remazol Brilliant Blue R Surface morphology
Simultaneous thermal analyzer
SP Salak peel
SPAC Salak peel based activated carbon rpm Rotation per minute
SEM UV
Scanning electron microscopy Ultraviolet
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PENJERAPAN PENCELUP OLEH KARBON TERAKTIF BERASASKAN KULIT BUAH SALAK: KAJIAN PENGOPTIMUMAN, KESEIMBANGAN,
KINETIK DAN TERMODINAMIK
ABSTRAK
Penjerapan pewarna malacit hijau (MH) dan remazol berkilau biru R (RBBR) telah diuji secara kelompok dengan menggunakan karbon teraktif berasaskan kulit buah salak (KTKBS). Kulit buah salak telah melalui proses pengaktifan fizikimia yang melibatkan enap jerap kalium hidroksida (KOH) dan penggasan karbon dioksida (CO2). Semasa proses penyediaan KTKBS, keadaan optimum telah diperoleh daripada kaedah sambutan permukaan (KSP). Keadaan optimum tersebut adalah suhu pengaktifan, masa pengaktifan dan nisbah KOH:arang, masing-masing pada 792°C, 1 jam dan 3:1 yang menghasilkan penyingkiran MH 81.74%, penyingkiran RBBR 63.97% dan hasilan KTKBS sebanyak 32.45%. KTKBS yang optimum mempunyai luas permukaan (968.32 m2/g), isi padu liang (0.503 cm3/g) dan karbon tetap (79.3%) yang tinggi. Liang KTKBS tergolong dalam kategori mesoliang dengan purata diameter liang 4.41 nm. Kesan kepekatan awal pewarna (100-500 mg/L), masa sentuhan (0–24 jam) dan suhu larutan (30-60oC) turut telah dinilai. Didapati bahawa model Langmuir adalah paling berpadanan untuk kedua-dua data garis sesuhu MH dan RBBR. Manakala, untuk analisa kinetik, didapati bahawa model pseudo-tertib-kedua dan pseudo-tertib-pertama adalah masing-masing paling sesuai digunakan untuk menentukan mekanisma penjerapan MH dan RBBR.
Penjerapan MH dan RBBR yang diuji ke atas KTKBS adalah secara endotermik.
xv
DYES ADSORPTION ON SALAK PEEL BASED ACTIVATED CARBON:
OPTIMIZATION, EQUILIBRIUM, KINETIC AND THERMODYNAMIC STUDIES
ABSTRACT
The adsorption of malachite green (MG) and remazol brilliant blue R (RBBR) dyes onto salak peel activated carbon (SPAC) were investigated in a batch process.
Salak peel undergoes physiochemical activation process which involves potassium hydroxide (KOH) impregnation and carbon dioxide (CO2) gasification. During the preparation of SPAC, the optimum preparation conditions were obtained from response surface methodology (RSM). The optimum conditions are activation temperature, activation time and KOH:char impregnation ratio (IR) with 792°C and 1 hours and 3:1 respectively, which has resulted in 81.74% MG removal, 63.97%
RBBR removal and 32.45% SPAC yield. Optimized SPAC has high of surface area (968.32m2/g), pore volume (0.503 cm3/g) and fixed carbon content (79.3%). The pore of SPAC was mesoporous type with average pore diameter of 4.41 nm. The effect of initial dye concentration (100-500 mg/L), contact time (0–24 hours) and solution temperature (30-60oC) were also evaluated through. The obtained equilibrium data for both dyes were best fitted by Langmuir model. Meanwhile, the kinetics data were best represented by the pseudo second-order model for MG and pseudo-first-order model for RBBR. The adsorption process of MG and RBBR onto SPAC were endothermic in nature.
1
CHAPTER ONE INTRODUCTION
1.1 Textile industries and dye effluent
There are 10,000 different dyes available in the market and the production of these dyestuffs has reach up to 700,000 tonnes per year worldwide (Ahmad and Rahman, 2010). In Malaysia, textiles industry is one of the contributors to the country’s economic development. Basic dye and reactive dye types are the most being produced in order to meet up with the growing demands textile industries (Bello et al., 2011). However, due to their highly complicated structures and difficulties in bio-degradable, their elimination from wastewater is undesirable. Yet, a very small amount of these dyes are highly visible and toxic to aquatic environment. These dyes reflect sunlight from entering the water which then interfere with the growth of bacteria and hinder photosynthesis in aquatic plant. Also, the degradation products from the textile dyes are also often carcinogenic and harmful to flora and fauna (Bouasla et al., 2010).
1.2 Treatment of industrial dye effluent
The removal of dyes from industrial effluent via an economical way is still remains as an important issue for many countries. Generally, the dyes removal treatments can be categorized into: (i) physical (coagulation and flocculation, membrane filtration and adsorption), (ii) chemical (chlorination, ozonation and electrochemical), and (iii) biological (fungal decolonization) methods. Although the chemical and biological methods are effective in removing dyes, their requirements in specialized equipment, high energy intensive and formation of large amount of by-
2
products causing them unfavorable to be utilized in long term application (Yahya et al., 2008).
Adsorption process as an alternative way is still one of the best wastewater treatment method in term of its efficiency and the possibility of using adsorbents for wide range of different type of dyes. In addition, its potential in regeneration, recovery and recycling of the adsorbent, made it recognized as one of the effective and well-established techniques (Onal, 2006). Activated carbon (AC) is porous carbon materials, possesses high surface area (>500m2/g), adsorption capacity and adsorption capability for gas to liquid phase application. It has been widely used for dyes wastewater treatment as it did not require any additional pre-treatment before its application (Bangash and Manaf, 2005). However, its expensive price in market due to the price of coal as precursor has limited its commercial application. For this reason, growing interest in searching low cost, renewable and readily available materials as precursor has been carried out particularly from agriculture wastes such as palm kernels, cassava peel, bagasse, jute fiber, palm-tree cobs, olive stones, date pits and fruit stones (Kumar et al., 2010). In this work, an attempt was made in using salak peel for the production of AC.
1.3 Problem statement
The discharge of colored dyes in wastewater from various industries such as textile and dyeing, pulp and paper and food processing industries have currently gained attention from different parties especially in industrialized countries. Direct discharge of them has cause pollution to the water bodies. Dyes are easily detectable as they are inherently highly visible with low concentration of 0.005 mg/l (Ofomaja, 2008). This has captured the attention of the public and the authorities. Moreover,
3
most of the dyes present in the textile wastewater are difficult to be removed as they are stable towards light, oxidizing agents and resistance towards aerobic digestion.
Most of them are mutagenic, carcinogenic and possess great threat to human kidneys, liver, brain, central nervous system and reproductive system. Consequently, it is crucial to ensure that the quality of the wastewater discharged is able to meet the requirements enforced in the environment legislation.
Meanwhile, adsorption has been recognized as an excellent dyes removal technique especially in terms of efficiency and simplicity of design. Unfortunately, owing to the expensive price of commercial coal based AC, its applications in dyes removal from wastewater is limited. Therefore, this studied was conducted to find out other alternatives precursor from agricultural waste which is cheap for preparing AC. Concerning to this, an attempt was made to use salak peel waste as precursor.
The salak peel based AC (SPAC) prepared was then tested it performance for adsorption of malachite green (MG) and remazol brilliant blue R (RBBR) from aqueous solution.
1.4 Scope of Study
In this work, the salak peel was utilized to prepare AC for MG and RBBR dyes removal. The preparation of SPAC was done via physiochemical method which applies impregnation of KOH to improvise the adsorptive characteristic of the AC.
The optimizations of the operating parameters of activation temperature, activation time and impregnation ratio (IR) were done using response surface methodology (RSM) method. RSM generates the design of experiment and the responses for every experimental run were analyzed to obtain optimum operating conditions for preparation of SPAC for dyes removal as well as SPAC yield.
4
The optimized SPAC was latter characterized in terms of surface area, surface morphology, proximate content and surface chemistry by using surface area analyzer, SEM, STA and FTIR respectively. The precursor and char samples were also included for comparison purposes.
The optimized SPAC were then used in equilibrium, kinetic and thermodynamic studies to investigate the adsorption behavior of each dye (MG and RBBR) onto SPAC. In order to carry out the analysis, batch adsorption study were done by examined the effect of adsorbate initial concentration (25-300 mg/L), contact time (0-24 hour), solution temperature (30-60°C) and solution pH (2-12) for adsorption of dyes onto SPAC prepared.
1.5 Research objectives
The main objectives of this study are:
(i) To optimize the SPAC preparation conditions (activation temperature, activation time and impregnation ratio) by using response surface methodology.
(ii) To study the effect of malachite green (MG) and remazol brilliant blue R (RBBR) adsorption onto SPAC in batch process under different initial dye concentrations, contact time and solution temperature.
(iii) To evaluate the adsorption isotherms, kinetics and thermodynamic properties of MG and RBBR adsorption onto SPAC.
1.6 Organization of thesis
This thesis consists of five main chapters and each chapter contributes to the sequence of this study. The content of the chapters are summarized as follows:
5
Chapter 1 introduces the usage of dyes in textile industries, problem statement, research objectives and organization of thesis.
Chapter 2 discusses the literature review of this study. An insight into dyes, discussion on adsorption process, activated carbon and raw material used in preparing activated carbon are elaborated. Moreover, the isotherm models, kinetic models and thermodynamic parameters determination are included as well.
Chapter 3 covers the experiment materials and the details of methodology. It discuss on the description of equipment and materials used, batch adsorption experiment, experimental procedure and description of factors affecting the adsorption process.
Chapter 4 refers to the experimental results and discussions of the data obtained. Further elaboration on the effect of different factors on batch system adsorption, the results on equilibrium, kinetic and thermodynamic properties are provided in this chapter.
Chapter 5 concludes all the findings obtained in this study.
Recommendations are also included as well.
6
CHAPTER TWO LITERATURE REVIEW
2.1 Dyes
Dye is a colored, ionizing and aromatic organic compound that shows affinity towards substrate to which it is being applied. It is extensively used to give color to textiles, paper and leather. Usually, dyes applied in an aqueous solution and mordant is required to act as an agent in order to have better affinity on the substrate (Bouasla et al., 2010). Most of the natural dyes are derived from plant such as roots, berries, bark, leaves and woods. Synthetic dyes are replacing natural dyes in textile industry as they offered a vast range of new colors and better properties to the substrate.
Synthetic dyes that are commonly used in textile industry can be categorized as basic dyes and reactive dyes. The classification of dyes based on applications are summarized in Table 2.1.
Table 2.1 Classification of dyes based on applications (Karim et al., 2015) Dye class Method of application Types of fibres
Basic Applied from acidic dye baths Paper, polyester and inks Reactive Dye reacts with fibre to bind dye
covalently under influence of heat
Cotton, wool, silk and nylon
A large volume of wastewater is produced from different steps in the dyeing and finishing processes. This wastewater is often rich in color and contains residues of dyes and chemicals, such as complex components, aerosols, high COD and BOD concentrations, and hard-degradation materials. For example in a cotton mill, there
7
are various steps involved in the processing textile in which each step discharge of some amount of pollutants as shown in Table 2.2.
Table 2.2 Pollutants from dyeing processing operations (Babu et al., 2007).
Process Compounds
Desizing Sizes, enzymes, starch, waxes, ammonia
Scouring Disinfectants and insecticides residues, NaOH, surfactants, soaps, fats, waxes, pectin, oils, sizes, anti-static agents, spent solvents, enzymes
Bleaching H2O2, AOX, sodium silicate or organic stabiliser, high pH Mercerizing High pH, NaOH
Dyeing Metals, salts, surfactants, organic processing assistants, sulphide, acidity/alkalinity, formaldehyde
Printing Urea, solvents, metals
Finishing Resins, waxes, acetate, stearate, spent solvents, softeners
In addition, the effluents produced from the textile industry contain ammonia, alkali salts, toxic solids, heavy metals and large amounts of pigments. Due to the complex aromatic molecular structures of dyes, it makes them inert and difficult to be degradable when discharged into the waste stream (Bello et al., 2011). Yet, the accumulation of dyes may lead to the formation of toxic by-products which caused harmful to both the environment and human. Therefore, in recent years, there have been great concerns to treat dye wastewater particularly by using adsorption technique.
2.2 Adsorption
In the past few decades, many techniques have been developed to find an economic and efficient way to treat textile industrial effluent. These technologies
8
usually consist of physical, chemical and biological treatment. Table 2.3 simplified the advantages and limitations of dyes removal practiced in industry.
Table 2.3 Advantages and limitations of dyes removal methods (Crini, 2006)
Methods Advantages Limitations
Physical treatment Adsorption Effective in removing a
wide variety of dyes
High capital costs Membrane
Filtration
Good permeate qualities High pressure and limited lifetime of membrane before fouling occurs Ion exchange No adsorbent loss due to the
capability of regeneration
Not applicable for wide range of dyes and high operating costs Chemical treatment
Coagulation/
precipitation
Simple and economically feasible
High sludge production leading to waste disposal problems
Oxidation Rapid and efficient High operating cost and require the use of chemical
Ozonation Able to produce
biodegradable products
Short half-life (20 minutes) Photocatalysis Mild operating condition Effective for small capacity
operation Sodium
Hypochloride
Effective in attacking amino group of dye with Cl+ ion
Require the use of chlorine (Cl) and formation of aromatic amine
Biological treatment Anaerobic Produce biogas that can be
reused in power generation
Formation of hydrogen sulphite Biomass Low operating cost, non-
toxic effect on microorganisms
Slow process and performance depends on pH
Biosorbent Economically attractive, high selectivity
Require chemical modification
Adsorption is a process that occurs when liquid accumulates on the surface of an adsorbent, forming a molecular or atomic film (adsorbate). More precisely, it occurs at the interfacial layers, the surface of the adsorbent and the adsorption space (whereby enrichment of adsorptive occurs). Adsorption can be classified into