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Adsorption of mb onto xmcm
The document presents a final year project report on the adsorption of methylene blue (MB) onto xanthogenated-modified chitosan microbeads (XMCM), highlighting the significance of reducing dye pollution in water bodies. It discusses the methodology, results, and characterizations of XMCM's adsorption capabilities, confirming its potential as an effective alternative adsorbent, particularly under optimal conditions of pH 4 and specific dosage and temperature settings. The study indicates that XMCM adheres well to the Langmuir adsorption isotherm model, suggesting a maximum adsorption capacity of 21.62 mg g-1 for MB.
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Adsorption of mb onto xmcm
- 1. ADSORPTION OF METHYLENEBLUE ONTO XANTHOGENATED-MODIFIED CHITOSAN MICROBEADS SITI NADZIFAH BINTI GHAZALI BACHELOR OF SCIENCE (Hons.) CHEMISTRY FACULTY OF APPLIED SCIENCES UNIVERSITI TEKNOLOGI MARA JULY 2013
- 2. ADSORPTION OF METHYLENEBLUE ONTO XANTHOGENATED-MODIFIED CHITOSAN MICROBEADS SITI NADZIFAH BINTI GHAZALI Final Year Project Report Submitted in Partial Fulfillment of the Requirements for the Degree of Bachelor of Science (Hons.) Chemistry In the Faculty of Applied Sciences Universiti Teknologi MARA JULY 2013
- 3. ii This Final YearProject Report entitled Xanthogenated- was submitted by Siti Nadzifah Binti Ghazali, in partial fulfillment of the requirements for Degree of Bachelor of Science (Hons.) Chemistry, in the Faculty of Applied Science, and was approved by ___________________________________ Zurhana Binti Mat Hussin Supervisor B. Sc. (Hons.) Chemistry Faculty of Applied Sciences Universiti Teknologi MARA 26400 Jengka Pahang _______________________________ Sarah Laila Binti Mat Jan Project Coordinator B. Sc. (Hons.) Chemistry Faculty of Applied Sciences Universiti Teknologi MARA 26400 Jengka Pahang _______________________________ Prof. Madya Mohd Supi Bin Musa Ketua Pusat Pengajian (KPP) Faculty of Applied Sciences Universiti Teknologi MARA 26400 Jengka Pahang Date:_________________
- 4. iii ACKNOWLEDGEMENT ALHAMDULILLAH, my deepestgratitude to the Almighty for His Blessings upon completion of this thesis. My sincere and profound appreciation to my dear supervisor, Madam Zurhana Mat Hussin, Lecturer in the Faculty of Applied Sciences and Miss Sarah Laila binti Mat Jan, the BSc.(Hons.) Chemistry Project Coordinator at MARA University of Technology (UiTM) for their guidance throughout my research, for providing required facilities and supporting this research work to be successfully completed within the proposed timeframe. I am thankful to Prof. Madya Dr Megat Ahmad Kamal Bin Megat Hanafiah as the RMU Coordinator, Mr Haslizaidi Bin Zakaria as Chemistry Programme Coordinator and Prof. Madya Mohd Supi bin Musa, Ketua Pusat Pengajian (KPP), School of Applied Science UiTM Jengka, for providing me the opportunity to utilise every facilities available to make this research a reality. The motivation, assistance and recommendations received from all staff in the UiTM Chemistry Department and all other faculty members including non-teaching staff who are involved directly or indirectly in this research are truly beyond my evaluation. Million thanks to my parents and family members whose selfless, whose always with me through hard and rough moments, whose supporting me in every phase of life until I reach to this level. Finally, I would like to thank everyone who has helped me directly or indirectly during the completion and success of this thesis. Any personnel missed in this acknowledgement are also thanked. Siti Nadzifah Binti Ghazali
- 5. iv TABLE OF CONTENTS Page ACKNOWLEDGEMENTSiii TABLE OF CONTENTS iv LIST OF TABLES vi LIST OF FIGURES vii LIST OF ABBREVIATIONS viii ABSTRACT ix ABSTRAK x CHAPTER 1 INTRODUCTION 1.1 Background and Problem Statement 1 1.2 Significance of the study 4 1.3 Objectives of the study 8 CHAPTER 2 LITERATURE REVIEW 2.1 Water Pollution 9 2.2 Dye Pollution 11 2.2.1 Methylene blue 13 2.3 Chitosan 16 2.3.1 Modified chitosan 18 2.4 Xanthogenate 21 CHAPTER 3 METHODOLOGY 3.1 Materials and Instruments 23 3.2 Research Methodology 25 3.3 Preparation of XMCM 25 3.4 Characterization of XMCM 26 3.4.1 FTIR 26 3.4.2 pHslurry 26 3.4.3 pHzpc 27 3.5 Batch Mode Study 27 3.5.1 Effect of Adsorbent Dosage 27 3.5.2 Effect of Initial pH 28 3.5.3 Isotherm study 28 CHAPTER 4 RESULT AND DISSCUSSION 4.1 Introduction 29 4.2 Adsorbent Characterizations 29 4.2.1 pHslurry 29 4.2.2 pHzpc 29 4.2.3 FTIR 30 4.3 Batch Mode Study 34 4.3.1 Effect of Adsorbent Dosage 34
- 6. v 4.3.2 Effect ofInitial pH 35 4.4 Adsorption Isotherm 37 4.4.1 Langmuir Isotherm 39 4.4.2 Freundlich Isotherm 41 CHAPTER 5 CONCLUSION AND RECOMMENDATIONS 5.1 Adsorption of methylene blue 44 5.2 Recommendations 45 CITED REFERENCES 47 CURRICULUM VITAE 51
- 7. iv LIST OF TABLES TableCaption Page 4.1 The Langmuir equation 39 4.2 The Freundlich equation 41 4.3 Summary Isotherm Model data 43
- 8. v LIST OF FIGURES FigureCaption Page 2.1 Molecular structure of methylene blue 13 2.2 Molecular structure of chitosan 16 3.1 4.1 Flow chart of research methodology pHzpc plot of XMCM 25 30 4.2 FTIR spectra of Chitosan before and after treatment 33 4.3 FTIR spectra of XMCM before and after MB loaded 33 4.4 Effect of adsorbent dosage on adsorption of MB onto XMCM 35 4.5 Effect of initial pH on adsorption of MB onto XMCM 37 4.6 General adsorption isotherm plot of MB onto XMCM 39 4.7 Langmuir isotherm 41 4.8 Freundlich isotherm 43
- 9. viii LIST OF ABBREVIATIONS cm-1 :per centimeter CTS : Chitosan H20 : Water Km : Kilometer M : Mole MB : Methylene Blue Mg : Magnesium mg : Milligram mg g-1 : Milligram per gram mg L-1 : Milligram per liter mL : Milliliter g : Gram Na : Sodium nm : Nanometer OH : Hydroxyl Pb : Lead Cu : Copper Zn : Zinc pHslurry : pH aqueous slurry pHzpc : pH zero point charge XMCM : Xanthogenated-Modified Chitosan Microbeads µm : Micrometer : Degree Celsius
- 10. ix ABSTRACT ADSORPTION OF METHYLENEBLUE ONTO XANTHOGENATED- MODIFIED CHITOSAN MICROBEADS Methylene Blue (MB) is thiazine dyes that widely use to color product in many industry such as textile, printing, leather, cosmetic and paper. Xanthogenated-Modified Chitosan Microbeads (XMCM) is use to observe the new alternative adsorbent in removing MB from water body through adsorption process. The interactions between MB and functional group in XMCM were confirmed by Fourier Transform Infrared (FT-IR). Several parameters that influence adsorption ability such as the effect of adsorbent dosage of XMCM and the effect of initial pH of MB aqueous solution were studied. This study were done at optimum condition which is at pH 4 of initial pH of MB solution, 0.01 g of initial XMCM dosage, 6 hours stirring time and temperature of (30 ± 2 ). The adsorption data fit well Langmuir model more than Freundlich model. Based on Langmuir model, the maximum monolayer adsorption capacity of MB was 21.62 mg g-1 which indicated that XMCM can be a new alternative adsorbent for removing MB.
- 11. x ABSTRAK PENJERAPAN METILEN BIRUKEATAS MIKROMANIK TERUBAHSUAI XANTOGENATED Metilen Biru (MB) adalah pewarna yang selalu digunakan untuk mewarna produk daripada pelbagai industri seperti industri pembuatan pakaian, pencetakan, kulit, kosmetik dan penghasilan kertas. Xanthogenated-Modified Chitosan Microbeads (XMCM) diperkenalkan sebagai agen alternatif penjerap baru dalam proses menjerap kandungan MB yang terkandung di dalam air. Fourier Transform Infrared (FT-IR) digunakan untuk mengenalpasti interaksi antara MB dengan kumpulan berfungsi yang terkandung dalam XMCM. Beberapa parameter yang mempengaruhi keupayaan penjerapan seperti kuantiti XMCM dan pH awal larutan MB telah dikaji melalui eksperiment ini. Kajian ini dilakukan pada keadaan optimum iaitu pada pH 4 untuk pH awal larutan MB, 0.01 g berat awal XMCM, 6 jam waktu pengacauan dan pada suhu (30 ± 2 ). Data yang terhasil lebih menepati model Langmuir berbanding model Freundlich. Berdasarkan model Langmuir, nilai penjerapan maksima MB adalah 21.62 mg g-1 . Kajian ini membuktikan XMCM boleh menjadi agen alternatif penjerapan baru untuk menyingkirkan MB.
- 12. 1 CHAPTER 1 INTRODUCTION 1.1 Backgroundand problem statement Water is vital for the entire aspects of life and also an important feature that defines our planet. Deprived water quality due to poor wastewater management is a crisis faced by every country in the world. This crisis affects directly and indirectly to our biological diversity, disturbing the entire ecosystem that act as our life support system. There are many factors affecting the aforementioned crisis and a major among many contributors is the industrial pollution (Corcoran et al., 2010). Colored (dye) pollution is highlighted as one of the common leading hazards due to its characteristics that give harmful effects on human and the nature (Wang et al., 2011). Dye pollution in industrial waste are from textile, leather, food processing, cosmetics and dye manufacturing industries, with textile known as the leading contributor (Rafatullah et al., 2010). In textile industry itself, there are a few types of dye pollutant such as reactive, direct, acid, and basic dyes (Vargas et al., 2011).
- 13. 2 The most commoneffluent found in textile industry is called methylene blue (MB) which is classified as a basic dyestuff and widely used for dyeing cotton, silk and wool (Rafatullah et al., 2010). Even though, MB is not classified as hazardous as pollutant as heavy metal, but the chronic exposure of excessive amount of this chemical can lead to adverse effect to human health and microorganisms. Instant contact via inhalation of MB can lead to breathing difficulties, while direct contact with MB may lead to permanent eye injuries, burning sensations, excessive sweating, mental confusion, cyanosis, convulsions, tachycardia and methemoglobinemia disease (Cazetta et al., 2011; Hameed and Ahmad, 2009). The toxicity and carcinogenic characteristics of MB also influence the ecological system by contaminated water with dyes inhibitory to aquatic life (Vargas et al., 2011). There are a variety of method were used in terms of treating wastewater due to industrial discharge of dye pollution, which is adsorption, membrane separation, oxidation and ozonation, coagulation and flocculation, as well as electro-coagulation. However, adsorption has been found to be the most favorable technique due to its potential technique to remove dye. Adsorption of dyes was found to be effective and economical compared to the use of other conversational techniques (Wang et al., 2011). Methylene Blue is a dye which currently use in many industries. Due to excessive discharge of this compound into water body, many cases related to its biodegradability have been reported to have negative impact on the natural water source (Weng et al., 2009). It is significant to the industries involved
- 14. 3 with the useof this compound to understand and effectively participate in the process of discharging this chemical to the most safely and hazard-free in our Eco-system. Generally, there are a couple of common ways to discharge methylene blue have been studied and developed in these past three decades such as a physical-chemical technique destroying the color groups, chemical oxidation including homogeneous and heterogeneous photocatalytic oxidation and a bio- degradation process mineralizing the colorless organic intermediate (Kamari et al., 2009). Adsorption is the most favorable technique to remove MB and other dyes from wastewater due to its effectiveness in removing various types of dye without producing chemical sludge (Zhu et al., 2012). Activated carbon was introduced in the past as the most effective adsorbent to remove coloring materials because of its large surface area and functional groups on its structure that makes adsorption possible in high capacity (Vargas et al., 2011). However, activated carbon requires high operating cost (Weng et al., 2009). Alternatively, chitosan was proposed as the new alternative adsorbents used to improve water conditions before it is discharged into water body.
- 15. 4 1.2 Significance ofthe study Each year, the world faces with the critical issues involving management of two million tons waste components from industrial, domestic and agricultural discharge that goes into the global water channels (Corcoran et al., 2010). This phenomenon has been reported to affect more than 1.8 million of children age 5 and below worldwide. Diseases spread by water expose and cause significant increase to vulnerable threats in the aforementioned population that a death occurs in every 20 seconds (Steiner and Tibaijuka, 2010). Current literature by Corcoran et al. (2010) and Deng et al. (2011) acknowledged dye traces in industrial wastewater as one of the commonest components that contributes to water pollution. The threat to this pollution is derived from the most common effluent found in textile industry called methylene blue (MB), which was classified as a basic dyestuff and widely used for dyeing cotton, silk and wool (Rafatullah et al., 2010). The literature suggests adsorption as the most preferred method to remove MB and other pollutants due to its effectiveness and unique chemical structure (Wan Ngah and Hanafiah, 2008; Zhu et al., 2012). Studies proven that adsorption is the most practical approach to treating wastewater with chitosan because this method is reliable, safe and cost-effective compared to other conventional techniques such as chemical precipitation, ion exchange, membrane filtration, solvent extraction, reverse osmosis, membrane coagulation, chemical oxidation and reduction, and electrolytic method (Rafatullah et al., 2010). These conventional techniques have limited ability to
- 16. 5 remove pollutant completely,non-practical, produces toxic sludge, sometimes required another disposal technique and might add to unnecessary cost projection (Wan Ngah and Hanafiah, 2008; Zhu et al., 2012). It is known that treating wastewater with dye traces is a challenging task because its molecules are intractable, tough over aerobic digestion and steady when matched with oxidizing properties (Crini and Badot, 2008). Treating wastewater containing low concentration of dye molecules is another challenge faced by some industries (Crini and Badot, 2008). Common methods found useful in removing dye molecules were reported not only have poor performance in favor to the economic point of view, but also would be theoretically complicated to be conducted. These have caused the removal methods on a massive scale were not applied extensively by related industries (Crini and Badot, 2008). In the actual wastewater management, there is more than one process that required to satisfy the process of dye removal within a reasonable costs involvement. Therefore, newly developed water treatment methods suggesting efficiency with practicality in utilization for huge scale manufacturing lines would be highly necessary (Crini and Badot, 2008). This would match to the current trend of eco-friendly industrial productions. Previous research has proven that removing of dye particles through adsorption process during water conservation could be cost effective (Wan Ngah et al., 2011). However, there is still a gap to be filled in finding an adsorbent that is reasonably priced, yet comes with higher efficiency profile as the main solution in water treatment. Two most important efficiencies that are
- 17. 6 relevant to theprofile would be i) the amount or dosage of the adsorbent use per unit of the untreated water, and ii) its disposal residues. General focus of adsorbent is on biosorbents like biomass and biopolymers, which are natural and can easily be found in massive quantities (Crini and Badot, 2008). Chitosan has captured highlights as a natural amino polymer which was reported as one of the more preferable and common methods in removing dye pollutants from the water body (Crini and Badot, 2008). Its fundamental characteristics of being naturally produced in its nature and its remarkable chelating ability that allows pollutants to bind during the adsorption and water rehabilitation process (Crini and Badot, 2008). Previous literature also suggests greater potential for chitosan is possible when used in wastewater treatment which could be achieved through some structure modifications (Wan Ngah et al., 2011; Zhu et al., 2012). It was revealed in the recent years that chitosan is pH sensitive; hence, modifying the process of its physical or chemical property would allow better adsorbing capability, which is s et al., 2011). The literature also suggests that the use of modified chitosan beads could be more cost-effective in treating wastewater (Zhu et al., 2012). Therefore, it is important to researcher to investigate whether Xanthogenate-Modified Chitosan Microbeads (XMCM) would be feasible as an option to wastewater treatment.
- 18. 7 This paper demonstratesthat XMCM can be used in treating wastewater due to MB pollution. This study was focused on three main stages which are modification of chitosan microbeads with xanthogenate, characterization of the adsorbent, batch mode study and isotherm study. The adsorbent were characterized by using FTIR, pHslurry and pHzpc analysis. Whereas, in the batch mode study, several parameters that influence the adsorption capacity are determined by adsorption experiment which is the effect of adsorbent dosage and the effect of initial pH. For isotherm study, the data were analyzed using two common isotherm models which are Langmuir and Freundlich to investigate the adsorption process. More practical and cheaper solutions could be developed to give an alternative to other dye removal technique in wastewater management. The emerging alternatives to wastewater treatment could vastly encourage SMIs (small and medium sized industries) to participate actively in treating industrial discharge during productions and saves the marine ecology. Through this study, 1. The feasibility of XMCM to remove MB in wastewater would be revealed. 2. The chemical process and uptake rate of XMCM against MB will be assessed and compared to other adsorbents. This will provide knowledge of the best chitosan-based adsorbent available in treating polluted wastewater.
- 19. 8 1.3 Objectives ofStudy The intention of this research is to investigate the adsorption capacity of MB onto XMCM. The specific objectives of this project include to:- 1. To characterize Xanthogenate-Modified Chitosan Microbeads by FTIR, pHslurry and pHzpc. 2. To determine the effect of important physicochemical parameters such as adsorbent dosage and pH that can affect adsorption efficiency of methylene blue. 3. To determine the isotherm study based on isotherm model (Langmuir and Freundlich model).
- 20. 9 CHAPTER 2 LITERATURE REVIEW 2.1Water pollution Water pollution is a critical issue faced by the global population as it causes higher death prevalence more than the total of people killed in wars (Steiner and Tibaijuka, 2010). Illnesses due to contaminated water affects more than km square of marine ecosystems involving food chain are badly affected (Lange and Jiddawi, 2009). These impacts are all due to poor management of wastewater, especially in developing countries where untreated water discharged directly into the mainstreams, thus adding significant risks to the fragile marine lives (UN Water, 2008). Without proper wastewater management and serious actions taken to reduce risks associated to water pollution, the world larger ecosystem would be at stake as the general population is increasing each year (UN Habitat, 2009). To cope greater advantage to human population because water is our main living component, while marine lives are part of our food and nutritional sources (Corcoran et al., 2010). A recent document concerning water preservation suggested wastewater treatment and sanitation is a new business with profitability between 300% to
- 21. 10 3400% depending onthe area and technology used for the treatment (Steiner and Tibaijuka, 2010). Despite overcoming this issue as part of global responsibility, treating wastewater was found to be a win-win business phenomenon. This could be achieved when the governing bodies may be able to offer better public health to the local population, protect vulnerable marine habitat and natural resources, as well as offering benefits to consumers using intelligent and cost-effective solution. Since wastewater management is a continuous concern in every country in the world, long-term business relations (Steiner and Tibaijuka, 2010). The responsibility of discharging industrial wastewater properly into the mainstreams lies on the shoulder of industrial corporates (Steiner and Tibaijuka, 2010). Meeting the criteria set to fulfill acceptable standards and dealing with the costs associated to the discharge process are among the duties (Steiner and Tibaijuka, 2010). Although good system comes at high expenses, improved technology and methods in treating waste water would be a great investment over a long term production in the industry. Prevention of industrial waste from spreading into the mainstreams and the utilization of closed water system are two main approaches central to cost effective wastewater treatment (Steiner and Tibaijuka, 2010). By treating the wastewater onsite, industries may have better access to cleaner water supply, thus minimize the production costs. This, when seen from the general economic point of view would means that consumers may enjoy huge discounts when production costs is reduced (Steiner and Tibaijuka, 2010).
- 22. 11 2.2 Dye Pollution Thepresences of dye pollutant in water body not only affect the aesthetic nature but also interferes the sunlight transmission into water which will reduce the photosynthesis activities (Han et al., 2011). Therefore, it is important to remove dye pollutant completely from wastewater. There are several types of dyes pollution that can be classified based on their properties and usage with are acid dyes, basic (cationic) dyes, direct (anionic) dyes and reactive dyes (Gupta and Suhas, 2009). Acid dyes are soluble in water, which is generally contained azo (including premetallized), nitroso, nitro, xanthene, azine, triphenylmethane and anthraquinone group. These dyes have been widely used as coloring agents for food, cosmetic, silk, wool, nylon, and ink-jet printing. Basic dyes are also water soluble dyes. It is known as cationic dyes because it generates colored cations in solution. These dyes can be classified as acridine, oxazine, thiazine, hemicyanine, cyanine, triarylmetahe and diazahemicyanine. These dyes are generally used for dyeing modified nylons, paper, polyacrylonitrile. Cationic dye also has been used medicine sector. The other water soluble dyes are direct (anionic) dyes. The principal chemical classes of these anionic dyes are poly-azo with some oxazines, phthalocyanines and stilbenes. These dyes broadly used for paper, rayon and cotton but not widely used for dyeing nylon. Reactive dyes have a simple chemical structure and a narrower adsorption bands were obtained on absorption spectra. These dyes are better than direct dyes due to it bright color than direct dyes. Its contain chromphoric groups which are azo, oxazine, formazan, phthalocyanine, triarylmethane and
- 23. 12 anthraquinone. They formcovalent bond with the fiber. They are widely used for dyeing cotton but not broadly used for dyeing nylon and wool (Gupta and Suhas, 2009). Rafatullah et al. (2010) estimated that more than 100 000 commercially available dyes with over 7 x 105 were generated by many industries to color their product. It is important to remove the present of dyes from water body because some dyes highly visible and undesirable even in very small amounts (less than 1 ppm) of it in wastewater. In addition, most obvious indicator for water pollution is color since any color change in water body can be detected directly with naked eyes. According to Crini and Badot (2008), it is difficult to remove a low concentration of dyes contain in wastewater. Dyes especially azo dyes are recalcitrant molecules, stable to oxidizing agent and resistant to aerobic digestion. The low biodegradability and inert properties of dyes make it very difficult to remove from wastewater. In treating wastewater affected by dye pollution, adsorption is a preferable method to remove MB and other pollutants because of its effectiveness (Wan Ngah et al., 2008; Zhu, et al., 2012). This technique has been used in many fields including but not limited to environment, oil and gas, and medicine in order to remove heavy metal, dyes, storage and oil spillage control (Auta and Hameed, 2011). Adsorption process has proven to be more reliable, safe and easy operation and less investment in terms of initial of cost development compared to other conventional techniques such as chemical precipitation, ion exchange, membrane filtration, solvent extraction, reverse osmosis, membrane
- 24. 13 coagulation, chemical oxidationand reduction, and electrolytic method (Rafatullah et al., 2010). These conventional techniques have limited ability to remove pollutant completely, non-practical, produces toxic sludge, sometimes required another disposal technique and might add to unnecessary cost projection (Wan Ngah et al., 2008; Zhu, et al., 2012). 2.2.1 Methylene Blue Methylene blue or Basic Blue 9 chemistry is described by the International Union of Pure and Applied Chemistry (IUPAC) as 3,7-bis(Dimethylamino)- phenazathionium chloride tetramethylthionine chloride with a chemical formula of C16H18ClN3S. It is a thiazine (cationic) dyes that having 319.85 g/mol molecular weight (Vargas et al., 2011; et al., 2012). MB appears as an odorless solid at a room temperature. It is a dark green powder and yields a blue solution when dissolved in water. It has strong adsorption characteristic onto solid with 668 nm maximum absorption wavelength (Hameed and El-Khaiary, 2008). The structure of MB is an aromatic organic compounds (Nasuha et al., 2010) as shown in Figure 2.1. Figure 2.1 Molecular structure of methylene blue Activated carbon are porous materials that have been reported by recent literature as the most effective adsorbent to remove heavy metal and dyes pollution due to its fast adsorption kinetic, high adsorbing capability and also having a high surface area (reach up to 3000 m2 g-1 ) (Cazetta et al., 2011; N H3C CH3 S N N CH3 CH3 +
- 25. 14 Nasuha et al.,2010). However it is relatively expensive due to its processes. The cost to produce activated carbon would increase accordingly with the quality of that adsorbent (Rehman et al., 2012). In recent years, removal of methylene blue using biomass and biopolymer has become alternative adsorbent to remove dyes pollution including MB dyes. Many researchers developed a new effective low cost adsorbent that comes from agricultural waste or natural materials in order to remove dye pollution (Hameed and Ahmad, 2009). Several low-cost approaches were found beneficial in removing methylene blue from wastewater, inter alia; modified ball clay (100 mg g-1 ), sugar extracted spent rice biomass (8.13 mg g-1 ), garlic peel (82.64, 123.45 and 142.86 mg g-1 ) , sugar beet pulp (714.29 mg g-1 ) and lotus leaf (8.13 mg g-1 ) (Auta et al., 2012; Rehman et al., 2012; Hameed and Ahmad, 2009; et al., 2012; Han et al., 2011). et al. (2012) reported the use of sugar beet pulp in order to remove methylene blue from aqueous solutions is the one of the most effective agro- indusrial solid waste adsorbent. Even though this adsorbent used do not undergo any physical or chemical treatment but it shows high adsorption capacity which is 714.29 mg g-1 . The high ability of this adsorbent to remove MB is due to the present of strongly bind cations in solutions which is pectin substances and carboxyl functions of galacturonic. Sugar beet pulp mainly consists of 65-80% polysaccharides, 30% pectin, 40% cellulose and 30% hemicellulose which indicates the present of carboxylate group .The author revealed that this adsorbent was found fit well the Langmuir models which
- 26. 15 indicate that themonolayers adsorption occurs. Scanning Electron Micrograph analysis also showed that the surface of adsorbent before after adsorption is different. It was found that this study was carried out at pH 8 of initial pH of MB aqueous solution and at 25 of optimum temperature condition. It was noticed that the adsorption of MB onto sugar beep increase with the increasing of the initial concentration and initial pH of MB aqueous solution. According to Auta et al. (2012), acid treatment increased adsorption capacity of clay onto MB (cationic dyes) due increasing of pore size and surface area. Acid react with a various type of cations and form chlorates and sulfates which can be eliminated easily. However, regarding to Deng et al. (2011) study, it was found that adsorbent porous structure not the only influenced the adsorption capacity of the adsorbent. There are various type of functional group on adsorbent surface that contribute to binding contaminants in adsorption process, inter alia; hydroxyl, sulphydryl, sulphonate, carboxyl and carbonyl groups. Surface of chemical structure also determined the adsorption capacity of MB onto the adsorbent. Nasuha et al. (2011) reported that NaOH treatment onto rejected tea increase pores of NaOH-modified rejected tea surface. The author also stated that the FTIR spectra of NaOH-modified rejected tea at 3112 cm-1 show the intense and broad absorption peaks indicate the present of hydroxyl group on the adsorbent surface which enhanced the MB binding capacity. MB dyes are proven mostly bind at OH groups by referring to the change in adsorption spectra of NaOH-modified rejected tea. There are another type of adsorbent
- 27. 16 can be usedin other to remove methylene blue from aqueous solution which is biopolymer chitosan. 2.3 Chitosan Chitosan is widely used as an adsorbent in adsorption process due to its ability to remove dyes and heavy metal ions even at low concentration (Wan Ngah and Hanafiah, 2008). The presence of high amine and hydroxyl groups in chitosan chain makes chitosan to have strong chelating ability (Kannamba et al., 2010; Zhu et al., 2012). The cationization of amino groups in chitosan makes the chitosan adsorb anionic dyes strongly by electrostatic attraction in acidic media (Wan Ngah et al., 2011). This adsorbent is a natural biopolymer that formed from deacetylation of chitin which comes from seafood cells such as crabs and prawns (Wan Ngah et al., 2011). It also known as an ideal natural support for enzyme immobilization due to its hydrophilicity, biodegrablility, biocompatibility, non-toxic and adsorption properties characteristic (Wan Ngah et al., 2011). In addition, they are cheaper and effective as alternatives to activated carbon due to the highly cost of activated carbons (Wan Ngah and Hanafiah, 2008). Figure 1.2 Molecular structure of chitosan Although chitosan alone has been proven effective in adsorption dyes and heavy metal but the formation of chitosan as a gel or solvent is depending on O O OH O NH2
- 28. 17 the pH valuesof the environment due to the characteristic of chitosan that is sensitive to pH (Wan Ngah et al., 2011). This means that its chemical property is not strong enough to absorb MB in different wastewater environment. Hence, its performance could still be improvised (Wan Ngah et al., 2011). There are several methods to modify chitosan have been developed by a researcher which is either physical or chemical modification. It is due to the solubility of chitosan in dilute mineral and organic acid. From the previous research by Wan Ngah et al. (2004) shows that chitosan is soluble in 5% (v/v) acetic acid but insoluble in 0.10 M NaOH and distilled water. However, the treated chitosan beads with cross-linking agent shows that chitosan are insoluble in that three medium solution. Cross-linking agent has been applied to improve the solubility of chitosan to become insoluble in acid solution and to increase its mechanical properties for better function against MB (Wan Ngah et al., 2011). There are several reagent that have been selected as a possible cross-linking agents, inter alia; glutaraldehyde, 1,1,3,3- tetramethoxypropane, epichlorohydrin, chloromethyloxirane, glycerolpolyglycidylether, ethyleneglycoldiglycidylether, and tri- polyphosphate (Kannamba et al., 2010). Previous research by Zhu et al. (2012) noticed that cross-linking agents reduces the adsorption capacity of chitosan. Hence, there is still a gap to which method is the best among many chitosan-based adsorption properties and chemical process to be used in regards to treat wastewater with MB.
- 29. 18 2.3.1 Modified Chitosan Accordingto Liu et al. (2010), Chitosan are not effective to remove cationic dyes unless undergo some modification. Recent literature found that there are a various type of modified chitosan were effective in removing methylene blue from wastewater, inter alia; chitosan-g-poly acrylic acid (1873 mg g-1 ) and chitosan-g-poly (acrylic acid)/attapulgite composite (1848 mg g-1 ), chitosan-g- poly (acrylic acid)/ vermiculite hydrogel (1685.56 mg g-1 ), cross-linked succinyl chitosan (298.02 mg g-1 ), chitosan-poly(acrylic acid) (1.03 and 3.59 mmol g-1 ), and magnetic chitosan/graphene oxide (180.83 mg g-1 ) (Wang et al., 2011; Liu et al., 2010; Huang et al., 2011; Guo and Wilson, 2012; Fan et al., 2012) Wang et al. (2011) reveal that the adsorption of methylene blue by using chitosan-g-poly acrylic acid and chitosan-g-poly (acrylic acid)/attapulgite composite show higher adsorption capacity. The adsorption behavior of both chitosan fits pseudo-second-order equation and the Langmuir model. They also reveal that the adsorption rate of both modified chitosan were fast. In the initial 15 min, about 90% of MB was removed. This study was conducted at optimum condition which is at pH 5 of initial MB solution and at 30 . It was noticed that the adsorption of methylene blue onto both modified chitosan sharply increase with the increasing of initial pH of MB solution from pH 2 to pH 5 and increase continuously from pH 5 to pH 9. At the higher pH, -COOH groups that present in acrylate were dissociated and form COO- . Hence, generates electrostatic repulsion forces among the adjacent ionized group due the increasing of the number of fixed ionized groups.
- 30. 19 Wang et al.(2011) also reveal that there is a relationship between temperature and adsorption capability. The capacity of adsorption increased with increase of the temperature exposed, noticeably during the first 10 °C changes from 30 °C to 40 °C. However, the performance significantly reduced when the temperature shifted from 40°C to 60°C. It was described that the increase to transpire. Conversely, when the dye molecules increased in size with composition; hence, decrease its capacity to adsorb further. This means that with increased exposure to extreme heat, the chitosan solution would not preform effectively. However, it was also noticed that the adsorption capacity decrease with the increasing of attapulgite content from 20% to 30%. There are lots of OH groups on the attapulgite surface. Attapulgite react with acrylic acid and act as crosslinking points in the network. Hence, higher crosslinking point will decrease the polymer chain elasticity and leads to decreasing of adsorption capacity. Through this study, the author adding 30% attapulgite into modified chitosan after considerable thought the cost of attapulgite is cheaper than acrylic acid and chitosan. In addition, the adsorption capacity of 30% attapulgite content in modified chitosan decreased lesser that the modified chitosan than contain 2% attapulgite.
- 31. 20 Liu et al.2010 also used acrylic acid in modification of chitosan-g-poly (acrylic acid)/ vermiculite hydrogel. Hydrogel have some ionic functional group that can adsorb Methylene blue (cationic dyes) from aqueous solutions, inter alia; sulfonic acid, hydroxyl, amine and carboxylic acid groups. Hydrogel able to adsorb and retain water and solute molecule because it is has higher porous network structures and water content which allow solute to diffuse through hydrogel structure. A modification of chitosan using magnetic fluid with graphene was performed by Fan et al. (2012). The study was conducted to improve the ability of natural cationic polysaccharide for the purpose of methylene blue (cationic dyes) removal from aqueous solutions. It was found in through the study that the application of magnetic fluids as a coating (layer) on the chitosan before the chitosan was exposed to MB did help adsorption functions to be extended. This technique allows dosage of the adsorbents to be minimized, while adsorption of methylene blue in aqueous form is optimized. During the process of chitosan modification in this study, graphene was oxidized and transformed into functional graphene oxide with the existence of oxygen. The extended surface widening was found not only benefits the mechanical strength of the stable chitosan, but also extended the capability of the modified chitosan in adsorption of MB in the water body.
- 32. 21 2.3 Xanthogenate Previous studyby using xanthogenate modification method into a plant base to form cellulose xanthogente derived from Eichornia Species has been done by Deng et al., 2012; Zhou et al., 2009 and Tan et al., 2008. The principle of preparing cellulose xanthogenate has been clarified by Tan et al. (2008) is shown in the following reaction: Cell- -ONa + H2O CS2 + Cell- -OCS2Na 2Cell-OCS2Na + Mg2+ -OCS2)2Mg + 2Na+ The purpose of chitosan modification with xanthate (NaOH + CS2) is to improve the potential of adsorption capacity of adsorbent onto adsorbate. Xanthate group have been chosen due to the presence of sulfur atoms. Sulfur groups are well known as having a greatly strong affinity for the most heavy metal and dyes. In addition, the metal-sulfur is really stable even in basic condition (Chauhan and Sankararamakrishnan, 2008). Based on Zhu et al. (2012) previous study, It was proven that magnetic chitosan that undergo chemical modification by using xanthate shows the higher adsorption capacity of Pb(II), Cu(II) and Zn(II) compared to unmodified magnetic chitosan. Modification of chitosan with xanthate group has been used previously on modified magnetic chitosan (Chen and Wang, 2012; Zhu et al., 2012), chitosan-GLA (Chauhan and Sankararamakrishnan,
- 33. 22 2008) and chitosanepichloroydrin (Kannamba et al., 2010) to enhance the adsorption performance under acidic solutions. Zhou et al. (2011), state that sulphur and magnesium content in xanthogenates increase the adsorption capacities of xanthogenates on Cu2+ . The exchange of copper with magnesium also increases the adsorption of copper. FTIR spectra show that alkali treatment decrease of absorbance intensity bands of O-H stretching, C=O stretching and C-O symmetric stretching. It is proven that alkali treatment removed hemicelluloses and lignin from the raw plant materials. However, new functional group which is O-CS-C and C=S was introduced by cellulose xanthogenate. Aforementioned, Sulfur groups having a greatly strong affinity for the most heavy metal and dyes. Tan et al. (2008) also stated that adsorption capacity cellulose xanthogente derived from Eichhornia Species was higher than other plant materials. It was noticed that, adsorption of copper ions increase with the increasing of pH and also by different anions. However it is not affected by sodium ions. Through their study, solution that containing shows the highest adsorption capacity of Cu2+ but lowest in the solutions that containing proves that adsorption of Cu2+ obviously was influenced by anions. However, adsorption capacity of Cu2+ in four solutions of different initiative Na+ concentration was almost the same which indicates that adsorption of Cu2+ not affected by sodium ion.
- 34. 23 CHAPTER 3 METHODOLOGY 3.1 Materialsand Instruments All reagent used were analytical grade chemicals, and distilled water was used throughout this study. 1000 ppm MB stock solution was prepared by dissolving 0.1357 g of MB in 100 mL distilled water. Initial pH of MB was adjusted by using 0.1 M NaOH and 0.1 M NaCl solutions. pH meter (Cyberscan 500) with a combined pH electrode (EUTECH Instrument) was used for pH measurement. MB concentration was determined using UV-Vis spectroscopy (Shimadzu, Model UV 1601, Japan) at 664 nm of absorbance wavelength. The lists of chemicals used are: 1. Acetic acid (CH3COOH) 2. Buffer solutions (pH 4 and 7) - Merck 3. Carbon disulfide (CS2) 4. Chitosan flakes 5. Hydrochloric acid (HCl) Lab Scan Analytical Sciences 6. Magnesium sulfate (MgSO4) 7. Methylene blue
- 35. 24 8. Sodium chloride(NaCl) 9. Sodium hydroxide (NaOH) - SYSTERM The lists of instruments used are: 1. Analytical balance Denver Instrument CO., AA- 160 2. Grinder 3. Sieve 4. pH electrode EUTECH Instrument 5. pH meter Cyberscan 500 6. Water-bath shaker with control temperature-SW22 (Julabo) 7. Fourier Transform Infrared spectroscopy (FTIR) PerkinElmer, 1600 Model 8. UV- Vis spectrometer-Shimadzu, Model UV 1601, Japan
- 36. 25 3.2 Research Methodology Theflow diagram of the adsorption studies of MB onto XMCM is shown below: Figure 3.1 Flow chart of research methodology 3.3 Preparation of Xanthogenated Modified Chitosan Microbeads (XMCM) Modifications of chitosan were performed by modifying the methods used by (Kannamba et al., 2010; Wan Ngah et al., 2013; Zhou et al., 2011). 2.0 g chitosan powder was soaked in 75 mL of 5% (v/v) acetic acid and was stirred for 3 hours to make sure the chitosan completely dissolved. The dissolved adsorbent was neutralized by dropping the adsorbent gel into 500 mL of 0.5 M NaOH solution under continuous stirring. White beads were left for 3 hours under continuous stirring. The beads were washed with distilled water for Sample Treatment Characterization FTIR pHslurry pHzpc Batch Mode Study Dosage pH Isotherm
- 37. 26 several times toremove the excess NaOH. The modified chitosan microbeads were treated with 100 mL of 14% NaOH solution and were stirred for 2 hours. Then, 1 mL of carbon disulphide (CS2) was added into the solution continuously and was stirred for 2 hours. Next, 10 mL of 0.42 M MgSO4 was added into the mixture and was stirred for another 1 hour. The Xanthogenate Modified Chitosan Microbeads (XMCM) were filtered and rinsed with distilled water. Lastly, the resulting beads were air-dried and sieved to obtain adsorbent size of < 212 µm. 3.4 Characterization of XMCM 3.4.1 FTIR The Infrared Spectra of adsorbent were obtained by using a Fourier Transform Infrared Spectrometer (PerkinElmer, 1600 Model). 0.1 g of XMCM was added into 10 mg/L MB solution and was stirred for 24 hours. After the stirring process completed, the solution was filtered. The adsorbents after adsorption was air dried and the effect of chemical treatments was determined by comparing any shift of band before and after adsorption. The functional groups present in chitosan flake, XMCM before and after adsorption with methylene blue were confirmed by using FTIR-ATR by scanning the samples at 400-4000 cm-1 with the resolution of 4 cm-1 . 3.4.2 pHslurry pHslurry was used to identify the acidity or an alkalinity of adsorbent using pH meter. The initial pH of distilled water was checked by using pH meter. After that, 0.1 g of adsorbent was added into 100 mL distilled water and the mixture
- 38. 27 was stirred for24 hours. After the stirring process completed, the pH of the solution was recalibrated by using pH meter. 3.4.3 pHzpc The pH of zero point charges (pHzpc) of the adsorbent was determined by modified addition method described by Ngah and Fatinathan (2010). NaCl solution was transferred into a series of conical flask. The initial pH (pHi) of 50 mL of 0.01 M NaCl in each conical flask was adjusted to a value between 3 to 9 by adding 0.1 M HCl or 0.1 M NaOH. 0.1 g adsorbent was added to each conical flask and the mixture was stirred for 24 hours. After the stirring process had completed, the solution was filtered and the final pH (pHf) of the solution was measured. The acidity or alkalinity of the adsorbent was i - pHf). 3.5 Batch Mode Study The optimum adsorbent dosage and pH for adsorption of methylene blue on xanthogenate-modified chitosan microbeads was determined through effect of adsorbent dosage and pH of adsorbate. In the isotherm study, the concentration of each pH and adsorbent dosage were fixed at optimum conditions. This study was done at 30 ± 2 . 3.5.1 Effect of Adsorbent Dosage The optimum dosage was determined by adding various doses of XMCM into 50 mL of 10 mg L-1 of MB. The pH of MB was fixed at pH 6. The adsorbent dosages used were 0.01 g, 0.02 g, 0.03 g, 0.5 g and 0.1 g. The mixture was
- 39. 28 stirred at 120rpm stirring rate for 6 hours. After the process was completed, the solution was centrifuged at 3000 rpm for 5 min. The solution was analyzed by using UV-Vis Spectrometer. The optimum adsorbent dosage of the XMCM was determined by plotting adsorption capacity (qe) against adsorbent dosage. 3.5.2 Effect of Initial pH The optimum pH for methylene blue adsorption on Xanthogente-Modified Chitosan Microbeads was determined by adding 0.01 g of XMCM into 50 mL of 10 mg L-1 of MB. The pH of adsorbate was adjusted from pH 3 to 9 by adding 0.1 M HCl and 0.1 M NaOH. The mixture was stirred for 6 hour at 120 rpm. After the adsorption process had completed, the solution was centrifuged at 3000 rpm for 5 minutes and then it was analyzed by using UV-Vis spectrophotometer. The optimum pH of the adsorbate was determined by plotting adsorption capacity (qe) against pH. 3.5.3 Isotherm Study For the isotherm study, the concentration of adsorbate was varied ranging from 10 to 100 mg L-1 . Each of the adsorbate was adjusted to pH 4. A mass of 0.01 g XMCM was added into each of solution. All solutions were stirred at 120 rpm for 6 hours. This study was done at 30 . After the stirring process had completed, the solution was centrifuged at 3000 rpm for 5 minutes and then analyzed by using UV-Vis spectrophotometer. The data obtained from this study was analyzed by using isotherm models which is Langmuir.
- 40. 29 CHAPTER 4 RESULTS ANDDISCUSSION 4.1 Introduction This chapter presents and discusses the result of experiment that had been carried out as described in chapter 3. 4.2 Adsorbent characterization Characterization of an adsorbent is an important analysis for understanding the behavior or the mechanism of MB removal on the surface of XMCM. XMCM was characterized by using pHslurry, pHzpc and FTIR analysis. 4.2.1 pHslurry pH aqueous slurry is used to confirm either the adsorbent was acidic or basic (Kamal et al., 2010). pHslurry obtained from this study was 9.91,which indicate the adsorbent was basic. 4.2.2 pHzpc pHzpc is used to show the tendency of a surface of adsorbent to become either positively or negatively charged (Kamal et al., 2010). Figure 4.1 show the value of pHzpc was 9.80 which indicate that XMCM was basic adsorbent.
- 41. 30 Kamal et al.(2010) stated that when the pH of adsorbate is greater than pHzpc, the surface of adsorbent will carry negative charge and vice versa. Hence, cationic dye adsorption study is more effective if the initial pH of adsorbate is higher than pHzpc value. In this study, pHzpc value was found to be near to the pH of aqueous slurry (pHslurry), which matched the previous finding that the pHzpc could be taken as equivalent to pHslurry (Kamal et al., 2010) Figure 4.1 pH zpc plot of XMCM 4.2.3 FTIR Fourier Transform Infrared (FT-IR) spectra are used to confirm the interactions between MB and functional group in XMCM. The FTIR spectrum of chitosan before and after treatment and XMCM before and after MB loaded shown in Figure 4.2 and Figure 4.3 indicates the presence of various type of functional group. Based on the chitosan spectrum, a broad -8 -7 -6 -5 -4 -3 -2 -1 0 1 0 2 4 6 8 10 12 pHi-pHf pH
- 42. 31 peak at 3272cm-1 corresponds to the presence of R-OH (hydroxyl group) and -NH2 (amine group). Kamari et al. (2009) stated that the broad and strong peak ranging from 3200 cm-1 to 3600 cm-1 indicates the overlapping of R-OH (hydroxyl group) and -NH2 (amine group) stretching vibrations. The peak that appeared at 2874.92 cm-1 can be assigned to symmetric -CH2 stretching vibration. The NH2 group was observed at peak 1744 cm-1 . Peak located at 1636 and 1560 cm-1 represent the deformation of amine which similar to peak (around 1650 cm-1 ) that observed by Kamari et al. (2009). The appearance sharp adsorption peak at 1453 cm-1 indicates present of NH2 (primary amine group). The bands that observed at 1375 and 1321 cm-1 can be attributed to the deformation of -CH3 and C-N stretching which similar to peak that observed by Wan Ngah et al. (2008). Peak located at 1298, 1229 and 1147 cm-1 can be assigned as C-O-C asymmetrical stretching vibration. It has been reported that, the C-O-C asymmetrical stretching vibration spectra are displayed around 1262 (Kamari et al., 2009), 1153 (Zhu et al., 2012) and 1115 cm-1 (Azlan et al., 2009). Peak observed at 1033 cm-1 shows the presence C-O-C symmetrical stretching vi According to recent literature, peak observed around 1076 - 1030 (Azlan et al., 2009) and 1026 cm-1 (Zhue et al., 2012) can be assigned as C-O-C symmetrical stretching vibration.
- 43. 32 After modification processwith xanthogenated, several changes in XMCM spectra were observed. Peak that observed at 3455 and 3187 cm-1 indicate the OH in Mg (OH)2 which is due to side reaction during the magnesium substitution process after CS2 sulfonation results in Mg(OH)2 percipitation (Deang et al., 2012). A new peak appear at 1654 cm-1 indicate the present of imine bond (C=N). NH2 peak of chitosan was found to be shifting slightly to the right (1445 cm-1 ) and increase the intensity due to modification treatment of xanthogenated. The high intense of new adsorption peak at 1429 cm-1 confirms the existence of C=S group. Figure 4.3 shows the spectrum of XMCM before and after adsorption with Methylene Blue. Based on the observation, there are new peak appear at 1546 cm-1 after adsorption process which prove that a chemical interaction was occur. This conclusion was proven with the studies done by Ngah et al. (2006), they concluded that no new peak was observed after adsorption process proves that a chemical interaction between positive and negatively charge do not occur through their study. The reduction of intensities of peak that observed at 1464 and 1370 cm-1 which also shift more to the left compared to peak 1445 (N-H group in amine) and 1429 cm-1 ( C=S group) before adsorption process indicated that nitrogen and sulfur atoms are the adsorption sites for MB on XMCM. Therefore, the main functional groups that participate in adsorption process of onto XMCM were hydroxyl, amino and sulfur.
- 44. 33 Figure 4.2 FTIRspectra of Chitosan before and after treatment Figure 4.3 FTIR spectra of XMCM before and after MB loaded. 4000 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 650 cm-1 CHITOSAN XMCM 3273 2875 1744 1637 1560 1453 1375 1229 1147 1033 896 739 707 3187 1730 1654 1429 1225 1145 1035 865 848 739 706 4000 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 650 cm-1 XMCM XMCM- MB 3190 1746 1546 1370 1228 1144 706 2934 3566 1638 1464 1038 891 739 3187 1730 1654 1445 1429 1225 1145 1034 865 848 739 706 3451 2941
- 45. 34 4.3 Batch modestudy Batch mode study is used to determine the optimum condition for adsorption of MB onto XMCM. 4.3.1 Effect of Adsorbent Dosage The relationship between adsorption of MB with adsorbent dosage of XMCM in Figure 4.4 shows that the percent removal of MB increased with the increasing of absorbent dosage. The surface area will be directly proportional to the mass of adsorbent in the solution as the particle size range used in this study was constant. However, the increase in mass of XMCM presented a decrease in adsorption capacity values of MB onto XMCM. According to Özer et al. (2007), the increase in the adsorption of MB with the adsorbent dosage can be associated with the increase of surface area and the sorption sites. The decreases of the effective surface area explained the reduction in adsorption capacity. The adsorbent dosage of 0.01 g was selected to be an optimum dosage for further adsorption study due to the highest value of adsorption capacity.
- 46. 35 Figure 4.4 Effectof adsorbent dosage on adsorption of MB onto XMCM 4.3.2 Effect of initial pH pH of initial solution plays an important role in the adsorption process due to hydroxyl and hydrogen ion will be adsorbed easily. Initial pH of the solution also affects the adsorption of other ions (Han et al., 2011). Therefore, the adsorption of MB dye was studied at different pH. This study was performed at pH 3 to 7. According to Crini and Badot (2008), pH 3 to 6 is an optimum range for dye adsorption onto adsorbent. The accumulation of competitor ions below this range would limits the adsorption capacity of MB onto XMCM. Figure 2.5 shows that the initial pH solution from pH 3 to pH 4 increased drastically from 2.24 to 6.83 mg g-1 due to the reaction of cationic dye with negative charge adsorbent surface. According to Han et al. (2011), acidic condition of MB solution produces more H+ ions in the system. Adsorbent surface attract positive charge by adsorb H+ ions. Hence, the competition and 0 10 0 20 40 0.00 0.02 0.04 0.06 0.08 0.10 0.12 qe(mgg-1) Removal(%) Dosage (g) Removal (%) qe (mg/g)
- 47. 36 electrostatic repulsion betweenMB and H+ ions for the adsorption site prevent the adsorption of MB ions onto XMCM surface. The number of negatively charged surface sites on the adsorbent increase as pH solution increase. Hence, the electrostatic attraction increases the adsorption of cationic dye molecules. However, this does not explain the adsorption capacity of MB after pH 4 that decreases continuously from pH 5 until pH 7. Based on the equations below, it shows there might be another ion exchange mode of adsorption. 1) CTS- -ONa+ + H2O CS2 + Cell-ONa+ -OCS2Na+ CTS-OCS2Na+ + Mg2+ CTS-OCS2)2Mg2+ + 2Na+ (CTS-OCS2)2Mg2+ + 2MB+ (CTS-OCS2MB+ ) + Mg2+ 2) CTS-NH2 + MB+ -NH2MB+ Therefore, it is proven that electrostatic mechanism was not the only reason for adsorption of MB occurs onto XMCM. Equation was modified by referring equation given by Tan et al. (2008) and Chauhan et al. (2008). According to Han et al. (2011), chemical reaction between the dye molecules and adsorbent also affects the adsorption capacity. Therefore, the experiment was carried out at pH 4 because the adsorption capacity of XMCM decreased at the pH higher than pH 4.
- 48. 37 Figure 4.5 Effectof initial pH on adsorption of MB onto XMCM 4.4 Adsorption Isotherm Isotherm study was done to show the relationship between amount adsorbed per unit weight of adsorbent (known in this equation: qe mg g-1 ) and the adsorbate in higher concentration (Ce mg L-1 ) under stable conditions when set at a specified temperature. According to Crini and Badot (2008), adsorption equilibrium is well established at the state where adsorbed dyes on the adsorbent are equivalent to the amount of adsorbent being desorbed. Here, the concentration in both phase are constant in equilibrium. The information about surface properties, adsorption mechanisms and affinity of an adsorbent towards adsorbate ions can be obtained from adsorption isotherm (Kamal et al. 2010). The adsorption isotherm plot of adsorption of MB onto XMCM shown in Figure 4.6 clearly shows that adsorption capacity 0 1 2 3 4 5 6 7 8 2 3 4 5 6 7 8 qe(mg/g) pH
- 49. 38 in Giles classificationsystem was obtained from this study indicates that chemical adsorption and reflects have relatively high affinity or strong adsorbate and adsorbent interactions (Kamal et al., 2010). According to Kamal et al. (2010), the isotherm plot shape provides information regarding the interaction between adsorbate with adsorbent. A steeper slope curve observed at lower initial concentration of MB (< 20 mg L- 1 ) which indicate that XMCM had sufficient number of adsorption site to adsorb MB ions at lower concentrations. However the slope curve start to plateau at the higher concentration (> 20 mg L-1 ) which indicate that adsorption sites would be saturated due to the ratio of the number of MB ions to the number of adsorption sites increased. Langmuir and Freundlich models are the most common use of isotherm models. Isotherm models were applied to understand the interaction between adsorbent and adsorbate.
- 50. 39 Figure 4.6 Generaladsorption isotherm plot of MB onto XMCM (adsorbentweight: 0.01 g, pH: 4, volume: 50 mL, shaking speed: 120 rpm, temperature: 30 ± 2 , initial MB concentration: 10 -70 mg L-1 , equilibrium time: 6 hours) 4.4.1 Langmuir Isotherm According to Crini and Badot (2008), Langmuir model was found to be the most appropriate to describe the adsorption process of dye on chitosan in recent study. The Langmuir equation as shown in Table 4.1 was used to describe MB adsorption onto XMCM. Table 4.1 The Langmuir equation non-linear form linear form Where is the amount of MB adsorbed at equilibrium (mg g-1 ), is the theoretical maximum adsorption capacity per unit weight adsorbent (mg g-1 ). is the Langmuir adsorption constant related to the affinity of binding sites (L 0 5 10 15 20 25 0 10 20 30 40 50 60 70 qe,mg/g Ce, mg/L
- 51. 40 mg-1 ) and ameasure of the energy of adsorption, and is the equilibrium MB concentration (mg L-1 ). Figure 4.7 shows the Langmuir plotting against gives a straight line of intercept and slope respectively equal to and . Langmuir model suggested the monolayer coverage of the MB on the XMCM surface (Kamari et al., 2009). A similar adsorption isotherm was also found in the adsorption studies of MB onto a various type chitosan carried out by (Liu et al., 2010; Fan et al., 2012; Huang et al., 2011; Wang et al., 2011). The maximum adsorption capacity of MB onto XMCM was 21.62 mg g-1 with 0.9885 of correlation coefficient (R2 ). The R2 value demonstrated that XMCM is a favourable adsorbent. (Kamari et al., 2009) stated that based on the separation factor on isotherm shape, the adsorption of dye on chitosan are favorable if the correlation coefficient (R2 ) value in the range 0 to 1.
- 52. 41 Figure 4.7 Langmuirisotherm 4.4.2 Freundlich Isotherm Freundlich model was developed from the assumption that the adsorption spots are scattered exponentially with reverence to the adsorption temperature. This model also assumes that the stronger adsorption site are occupied first and the increasing of degree site occupation degree will leads the decreasing the binding strength. The model as shown in Figure 4.8 explained multilayer adsorption between equilibrium of the liquid with solid phase capacity (heterogeneous surface). Table 4.2 shows the non-linear and linear equation of Freundlich. Table 4.2 The Freundlich equation non-linear form linear form y = 0.0463x + 0.3503 R² = 0.9885 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0.000 10.000 20.000 30.000 40.000 50.000 60.000 70.000 Ce/qe Ce (mgL-1)
- 53. 42 Where and areFreundlich constant that represents adsorption capacity (mg g-1 ) and adsorption intensity (unit less). This Freundlich constant value and can be obtained by plotting a linear Freundlich plot of versus . Where and are related to intercept and slope, respectively. The summary of the maximum adsorption capacity, adsorption intensity, and correlation coefficient value obtained from this study is shown in Table 4.3. The maximum adsorption capacity obtained was 1.59 mg g-1 . value obtained was 1.23 which is greater than 1. (Fan et al. 2012) stated that if Freundlich constant value is greater than 1 indicate that it is a cooperative adsorption; otherwise, it indicate a normal Langmuir isotherm. However, value (0.9351) obtained from Figure 4.8 indicate that the adsorption of MB onto XMCM does not follow the Freundlich isotherm. It is because the value obtained does not correlate well compared to the Langmuir correlation coefficient value.
- 54. 43 Figure 4.8 Freundlichisotherm Table 4.3 Summary of Isotherm Model data Langmuir Freundlich (mg g-1 ) (L mg-1 ) R2 KF n R2 21.62 0.13 0.9885 1.15 1.29 0.9351 y = 0.7738x + 0.0621 R² = 0.9351 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 0.00 0.50 1.00 1.50 2.00 logqe log Ce
- 55. 44 CHAPTER 5 CONCLUSION ANDRECOMMENDATIONS 5.1 Adsorption of Methylene Blue The study was conducted to explore the feasibility of Xanthogenate-Modified Chitosan Microbeads (XMCM) in adsorbing Methylene Blue (MB) that exists in wastewater. The feasibility of XMCM use in treating wastewater was assessed based on XMCM characterization, its effects on MB adsorption that are due to the XMCM volume used during the experiment, its initial pH value, adsorption isotherm, as well as Langmuir and Freundlich isotherm. The chemical process and uptake rate of XMCM against MB was assessed and compared to other adsorbents was conducted to determine whether XMCM could be the best chitosan-based adsorbent available in treating polluted wastewater. The aims and objectives of this study have been achieved in practice, where another alternative adsorbent has been developed and tested onto MB from wastewater (aqueous solution). The modified technique is known as Xanthogenate-Modified Chitosan Microbeads (XMCM) found to match the Langmuir model by having 21.62 mg g-1 of adsorption capacity. However, this figure indicates that XMCM has minimal effect on MB adsorption.
- 56. 45 Through the experiment,it was proven that the preparation and modification of XMCM involved a significant amount of time; hence indirectly affect the final outcome of the experiment. Due to long process of XMCM modification, certain variables such as OH group from the modified chitosan has been reported lost from the formulation. This has great impact on the functional onto XMCM was found at pH 4 for of initial MB aqueous solution pH, and at 0.01 g of the amount of adsorbent dosage. Although the previous literature signifies chitosan as the low-cost adsorbent and effective when modified and tested with MB inter alia; chitosan-g-poly acrylic acid (1873 mg g-1 ) and chitosan-g-poly (acrylic acid)/attapulgite composite (1848 mg g-1 ), chitosan-g-poly (acrylic acid)/ vermiculite hydrogel (1685.56 mg g-1 ), cross-linked succinyl chitosan (298.02 mg g-1 ), chitosan- poly(acrylic acid) (1.03 and 3.59 mmol g-1 ), and magnetic chitosan/graphene oxide (180.83 mg g-1 ) (Wang et al., 2011; Liu et al., 2010; Huang et al., 2011; Guo et al., 2012; Fan et al., 2012), the XMCM results in this study indicate that the modified form of chitosan has underperform itself and incapable to adsorb MB as expected in the theory. 5.2 Recommendations The outcome shows that there is very little benefit gained with the use of XMCM on MB in this study. Based on the outcome of this research, there are two probabilities that could be tested in the future, they are:
- 57. 46 i) whether thereis a method to be utilized in preserving the OH group while chitosan modification takes place, or ii) use of other chemical during the process of chitosan modification. It also suggested that XMCM be used as an adsorbent to anionic dyes in future study since it is known that XMCM is a cationic adsorbent. It also suggested to modified chitosan with xanthate and hydrogel in order to introduce sulfur atoms and also some ionic functional group (in hydrogel) that can adsorb Methylene blue (cationic dyes) from aqueous solutions, inter alia; sulfonic acid, hydroxyl, amine and carboxylic acid groups. In addition, Hydrogel able to adsorb and retain water and solute molecule because it is has high porous structures and water content which allow solute to diffuse through hydrogel structure. Wastewater treatment would still be a field critical enough to be urged for serious attention and action worldwide. The findings of each studies related to adsorption of MB is still not clear to determine the most appropriate model to be used for wastewater treatment in industries related to dye pollution. in managing wastewater cycles effectively, for marine lives to be saved and global water streams to be preserved.
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