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Unformatted text preview: AND 2,4 DICHLOROPHENOL ONTO CHEMICALLY- AND THERMALLY-MODIFIED RICE HUSKS: EQUILIBRIUM, THERMODYNAMIC AND KINETIC STUDIES Siok-Moi Khor, Chye-Eng Seng, Poh-Eng Lim and Amat-Ngilmi Ahmad Sujari School of Chemical Sciences, Universiti Sains Malaysia, 11800 Pulau Pinang, Malaysia E-mail: ksmoi2810@yahoo.com The objectives of this research are (i) to study the sorption of 4 -chlorophenol (4CP) and 2,4dichlorophenol (2,4-DCP) onto powdered activated carbon (PAC) and chemically - and thermallymodified rice husk (ARH), (ii) to determine the thermodynamic parameters and to ascertain appropriate adsorption equilibrium models for both of these non -volatile xenobiotic organic compounds at different temperatures and (iii) to develop or modify a kinetic model based on the kinetic studies. The ARH was prepared by reacting the sieved raw rice husk (<250 μm) with 0.1 M HNO 3 for 1 h. followed by soaking in methanol for 4 h and then carbonizing for 1 h at 300 °C. Equilibrium adsorption studies were conducted by varying the operational parameters such as initial pH, contact time, adsorbent dosage and initial concentrations of 4CP and 2,4-DCP. The equilibrium adsorption data were fitted to the Langmuir, Freundlich, and Redlich-Peterson models to describe mathematically the sorption equilibrium and to obtain the isotherm constants. The linearized Langmuir and non -linearized Redlich-Peterson models were found best fitted to the experimental data for 4CP and 2,4 -DCP. From the Langmuir model, the adsorption capacities of PAC and ARH were found to be 285.17 and 56 .50 mg/g for 4CP, respectively, and 384.62 and 94.33 mg/g for 2,4-DCP, respectively. Kinetic models were used to fit the experimental data obtained in the sorption kinetic studies involving different initial adsorbate concentrations and at selected temperatures. The thermodynamic quantities of the adsorption process, ΔG°, ΔH°, and ΔS°, were determined at selected temperatures. 90 3rd ICYC 2010 Universiti Sains Malaysia ENV...
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