Sorption potential of rice husk for the removal of 2,4-dichlorophenol from aqueous solutions: Kinetic and thermodynamic investigations This work is dedicated to our late Prof. Dr. A.W.K. Khanzada, who is not present among us physically, but spiritually he will always remain among us

• Published in: Journal of hazardous materials 2006-01, Vol.128 (1), p.44-52
• Main Authors: Akhtar, Mubeena, Bhanger, MI, Iqbal, Shahid, Hasany, SMoosa
• Format: Article
• Language: English
• Subjects: Oryza sativa
• ISSN: 0304-3894
• DOI: 10.1016/j.jhazmat.2005.07.025

The sorption potential of chemically and thermally treated rice husk (RHT) for the removal of 2,4-dichlorophenol (DCP) from aqueous solutions has been investigated. Sorption of DCP by rice husk was observed over a wide pH range of 1-10. The effect of contact time between liquid and solid phases, sorbent dose, pH, concentration of sorbate and temperature on the sorption of DCP onto rice husk has been studied. The pore area and average pore diameter of RHT by BET method are calculated to be 17 +/- 0.6 m super(2) g super(-1) and 51.3 +/- 1.5 nm, respectively. Maximum sorption (98 +/- 1.2%) was achieved for RHT from 6.1 x 10 super(-5) mol dm super(-3) of sorbate solution using 0.1 g of rice husk for 10 min agitation time at pH 6 and 303 K, which is comparable to activated carbon commercial (ACC) 96.6 +/- 1.2%, but significantly higher than chemically treated rice husk (RHCT) 65 +/- 1.6% and rice husk untreated (RHUT) 41 +/- 2.3%. The sorption data obtained at optimized conditions was subjected to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. Sorption intensity 1/n (0.31 +/- 0.01) and sorption capacity multilayer C sub(m) (12.0 +/- 1.6 mmol g super(-1)) have been evaluated using Freundlich sorption isotherm, whereas the values of sorption capacity monolayer Q (0.96 +/- 0.03 mmol g super(-1)) and binding energy, b, (4.5 +/- 1.0) x 10 super(4) dm super(3) mol super(-1) have been estimated by Langmuir isotherm. The Langmuir constant, b, was also used to calculate the dimensionless factor, R sub(L), in the concentration range (0.6-6.1) x 10 super(- 4) mol dm super(-3), suggesting greater sorption at low concentration. D-R sorption isotherm was employed to calculate sorption capacity X sub(m) (2.5 +/- 0.07 mmolg super(-1)) and sorption energy E (14.7 +/- 0.13 kJ mol super(-1)). Lagergren and Morris-Weber equations were employed to study kinetics of sorption process using 0.2 g of RHT, 25 cm super(3) of 0.61 x 10 super(-4) mol dm super(-3) sorbate concentration at pH 6, giving values of first-order rate constant, k, and rate constant of intraparticle transport, R sub(id), (0.48 +/- 0.04 min super(-1) and 6.8 +/- 0.8 nmolg super(-1) min super(-1/2), respectively) at 0.61 x 10 super(-4) mol dm super(-3) solution concentration of DCP, 0.1 g RHT, pH 6 and 2-10 min of agitation time. For thermodynamic studies, sorption potential was examined over temperature range 283-323 K by employing 6.1 x 10 super(-4) mol dm super(-3) solution concentration of DCP, 0.