ISSN 2995-9246
International Journal of Chemistry | Vol. 1, No. 2, February 2010 | pp. 9–17
DOI: 10.46882/2010/IJC/000002
Article Type: Original Research Paper
Title: Thermodynamic and Kinetic Studies on the Adsorption of Lead(II) Ions from Aqueous Solutions Using Modified Rice Husk Biochar
Names of Authors: Samuel T. Adebayo¹, Elena P. Vasilyeva²
Authors’ Affiliations:
¹Department of Industrial Chemistry, University of Ibadan, Ibadan, Nigeria
²Department of Environmental Chemistry, Saint Petersburg State University, Saint Petersburg, Russia
Abstract: Heavy metal contamination of water resources poses severe threats to ecological and human health. This study evaluates the efficacy of chemically modified rice husk biochar (MRHB), treated with 0.5 M phosphoric acid, for the removal of toxic Lead(II) [Pb²⁺] ions from synthetic wastewater. Batch adsorption experiments were conducted to optimize variables such as contact time, pH, temperature, and adsorbent dosage. The maximum adsorption capacity of MRHB for Pb²⁺ was determined to be 48.52 mg/g at an optimum pH of 5.5, which represents a three-fold increase compared to unmodified biochar. Equilibrium data were analyzed using Langmuir and Freundlich isotherm models. The data fitted best to the Langmuir model (R² = 0.994), indicating monolayer adsorption on a homogenous surface. Kinetic studies revealed that the adsorption process strictly followed the pseudo-second-order kinetic model, suggesting chemisorption as the rate-limiting step. Thermodynamic parameters, including Gibbs free energy change (Delta G°), enthalpy change (Delta H°), and entropy change (Delta S°), were calculated. The negative values of Delta G° (-4.23 to -6.81 kJ/mol) and positive value of Delta H° (+12.45 kJ/mol) confirmed that the adsorption process was spontaneous and endothermic in nature. Desorption studies using 0.1 M HCl showed a recovery rate of 89.6% of adsorbed Pb²⁺, indicating excellent regenerability.
Keywords: Biochar, Rice husk, Adsorption, Lead removal, Wastewater treatment, Kinetics, Isotherms
Manuscript Timeline: Received: November 05, 2009; Revised: December 14, 2009; Accepted: January 08, 2010; Published: February 04, 2010