ISSN: 2410-9649 Babarinde and Onyiaocha / Chemistry International 2(1) (2016) 37-46 iscientic.org. 37 www.bosaljournals/chemint/ editorci@bosaljournals.com Article type: Research article Article history: Received July 2015 Accepted August 2015 January 2016 Issue Keywords: Groundnut shell Pb(II) Cd(II) Zn(II) Biosorption Isotherm Kinetics Thermodynamics The equilibrium, kinetics, and thermodynamics of the biosorption of Pb(II), Cd(II) and Zn(II) onto groundnut (Arachis hypogaea) shell were investigated under various physicochemical parameters. Optimisation studies were carried out using batch biosorption studies. The extent of the metal ion biosorption increased with increase in solution pH, initial metal ion concentration, dosage of biosorbent and contact time but decreased with the temperature of the system. The biosorption of each of the metal ions was found to be pH-dependent. Kinetic study showed that the metal ions biosorption process followed the pseudo-second-order kinetic model. The sorption of each metal ion was analysed with Freundlich and Langmuir isotherm models, in each case, the equilibrium data were better represented by Freundlich isotherm model. Thermodynamically, parameters such as standard Gibbs free energy (∆G˚), standard enthalpy (∆H˚), standard entropy (∆S˚) and the activation energy ( A) were calculated. The biosorption of each metal ion was spontaneous and the order of spontaneity of the biosorption process being Cd(II) > Zn(II) > Pb(II). Similarly, change in entropy was observed for each and the order of disorder is Cd(II) > Zn(II) > Pb(II). © 2016 International Scientific Organization: All rights reserved. Capsule Summary: Groundnut shell was investigated for the sorption of Pb(II), Cd(II) and Zn(II), process variables were optimized, sorption data was subjected to kinetic and isotherm models and thermodynamic studies were also performed. Results showed that groundnut shell has high efficiency in the sorption of Pb(II), Cd(II) and Zn(II) and could possibly be used for treating wastewater containing these metal ions. Cite This Article As: Adesola Babarinde and Gloria Ogonna Onyiaocha. 2016. Equilibrium sorption of divalent metal ions onto groundnut (Arachis hypogaea) shell: kinetics, isotherm and thermodynamics. Chemistry International 2(1) 37-46 INTRODUCTION Heavy metal pollution in aquatic environment has become a source of great concern. In natural aquatic ecosystems, metals occur in low concentrations but in recent times, the occurrence of metals in excess of natural loads has become a problem of increasing concern. This situation has arisen as a result of industrialization and urbanization (Hanan et al., 2010). The increased industrialization results in the release of varied types and amounts of industrial wastes into the environment. These industrial wastes consist of several classes of pollutants including heavy metals. Apart from industrial activities, other sources of heavy metals into the environment include untreated domestic effluents, agricultural wastes, discharge from sewage treatment works, urban storm-water run-off, leaching of metals from garbage and solid wastes dump (Bilal et al., 2014; Iqbal et al., 2013; Iqbal and Bhatti, 2014, 2015; Iqbal and Khera, 2015; Iqbal Chemistry International 2(1) (2016) 37-46 Equilibrium sorption of divalent metal ions onto groundnut (Arachis hypogaea) shell: kinetics, isotherm and thermodynamics Adesola Babarinde 1 and Gloria Ogonna Onyiaocha 2 1 Department of Chemical Sciences, Olabisi Onabanjo University, Ago- Iwoye, Nigeria 2 Applied Science Laboratory, Federal College of Fisheries and Marine Technology, Lagos, Nigeria *Corresponding author’s E. mail: adesola.babarinde@oouagoiwoye.edu.ng , solababarinde@yahoo.com , Tel: +234-8037232934 ARTICLE INFO A B S T R A C T