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Item A Study of the adsorption of oxalic acid on carbonized tea waste prepared under different heat treatment conditions(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Kumara, K. A. S. S.; Prashantha, M. A. B.; Jayaweera, C.D.Carbonized materials are produced by various types of carbon precursors using chemical as well as physical methods. In this study, spent tea leaves, a waste and easily available low cost material, was used as the raw material for the preparation of carbonized material. The objective was to produce carbonaceous material from tea waste by application of heat and investigate the adsorption equilibrium, isothermal and kinetic studies of adsorption of oxalic acid on the carbonized tea waste. Carbonization was carried out at 350 °C for 30 min and 45 min to produce two types of carbonized tea waste. The adsorption isotherms of Langmuir, Freundlich, Temkin, and Dubnin-Radushkevich (D-R) and kinetic models; pseudo first order, pseudo second order, intra particle diffusion, liquid film diffusion, and Elovich models were used to study the behavior and characteristics of oxalic acid adsorption to the carbonized tea waste. All the studies were carried out at five different temperatures 30 ºC, 40 ºC, 50 ºC, 60 ºC, and 70 ºC. The best fit for the Langmuir isotherm suggests that the adsorption of oxalic acid onto carbonized tea waste is a monolayer adsorption process for a homogeneous surface. The maximum adsorption capacities were obtained using Langmuir isotherm. The 45 min Carbonized tea waste showed the maximum adsorption capacity of 107.5 mg g-1 at 40 ºC. The maximum adsorption capacity for 30 min carbonized tea waste is 95.2 mg g-1 at 70 ºC. The pseudo second order kinetic model well fitted with the adsorption process, having correlation coefficient values of 0.9989 and 0.9663 for 30 min carbonized tea waste and 45 min carbonized tea waste respectively suggesting that the chemisorption mechanism is predominant. The results also revealed that the adsorption of oxalic acid onto carbonized tea waste is feasible and spontaneous. However, at 350 °C, when the carbonization time was increased from 30 min to 45 min the process changed from endothermic to exothermic with declined randomness. The presence of functional groups hydroxyl, carboxyl, carbonyl and amine in the carbonized tea waste was confirmed by FTIR studies. The surface characteristics such as the roughness, presence of micropores and mesopores as revealed by SEM-Eds technique may cause a favourable adsorption. In spite of the required high carbonization temperature and time heat treated carbonized tea waste points out to have adsorption characteristics similar to commercially available activated carbon according to this studyItem Investigation of fluoride adsorption capacity of characterized graphene oxide based super sand(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Perera, R. T.; Pathirannehe, P. N. S.; Weerasooriya, R.; Kumarasinghe, A. R.; Liyanage, J. A.Sand is conventionally used in water treatment plants to control water turbidity. This research work was aimed for improving its performance using a chemical modification to remove other water contaminants as well. Thus improved substrate was designated as “Super Sand”. Super sand has proven to be a better adsorbent for the removal of fluoride from water. Fluoride is an essential constituent for human health and toxicity of the fluoride depends on the concentration of the fluoride in the drinking water source. The fluoride adsorption capacity of characterized super sand was determined. Graphene Oxide (GO) was synthesized using the modified Hummers method and then GO was coated with purified sand for the generation of super sand. Single GO coated super sand and multiple GO coated super sand were synthesized for the investigation of fluoride adsorption capacity. GO and super sand were characterized using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectrometry (EDXAS), Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD) analysis and surface titration. Surface titration curve depicted that surface charge of super sand vary with pH value of the medium. Between pH 4 to 7 it has a total positive charge and above pH 7 it has a total negative charge. In order to determine the fluoride adsorption process, isotherm studies were done for both single coated and multiple coated super sand. According to the isotherm studies, single coated super sand has the maximum fluoride adsorption capacity at 2 mg/L fluoride concentration and multiple coated one has maximum fluoride adsorption capacity at 3 mg/L fluoride concentration. Further optimization studies were also performed and finally it was proved that fluoride adsorption by the super sand follows the Langmuir isotherm model. Further, FTIR analysis of super sand and fluoride adsorbed super sand at different pH mediums depicted that adsorption process is a chemisorption process. However, FTIR peak patterns depend on the pH of the medium. Hence, it can be concluded that surface modified super sand is suitable for the fluoride removal from the fluoride contaminated drinking water.Item A study on sorption of Cd(II) onto chitosan derivatives.(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Samaranayaka, K. A. S.; Rajapakse, C. S. K.Pollution of water sources, specially drinking water sources, is becoming a serious problem in the world today. Unlike organic pollutants, heavy metals are non-biodegradable and even trace amounts of some of the heavy metals such as cadmium is highly toxic and may cause deleterious health effects in humans. In recent years the search for efficient, readily available and more affordable adsorbents that have high metal-binding capacities for the removal of toxic heavy metals in drinking water has intensified and in this research, chemically modified chitosan [cross-linked chitosan beads (CLCB) and physically modified chitosan] and chitosan coated activated carbon (CCAC) were prepared and their sorption properties for Cd(II) uptake were studied. Chitosan derivative CLCB was prepared using glycerol diglycidyl ether as the cross linking agent and composite bio-adsorbent CCAC has been prepared by coating chitosan onto commercially available activated carbon to improve their mechanical strength and metal adsorption ability compared to that of unmodified chitosan. The modified adsorbents were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The equilibrium data were evaluated using Langmuir, and Freundlich isotherms and adsorption equilibrium data of Cd(II) adsorption onto CLCB and CCAC at 30 0C were correlated with the Langmuir isotherm model. The maximum monolayer adsorption capacity; Langmuir constant, qo obtained for adsorption of Cd(II) onto CLCB and CCAC were 79.4 μg/g and 84.0 μg/g, respectively, which were significantly higher than the values for the adsorption of Cd(II) onto unmodified chitosan. The kinetic data were fitted with the pseudo second order model for initial Cd(II) concentrations of 50 μg/L. The findings from this research indicate that the CLCB and CCAC have enhanced Cd(II) sorption abilities compared to that of unmodified chitosan. Therefore, the modified chitosan derivatives could be used as efficient bio-adsorbents to remove Cd(II) from polluted drinking water.