Equilibrium and kinetic studies of the biosorption of heavy metal (cadmium) on Cassia siamea bark

Abstract

This study focuses on the possible use of Cassia siamea to remove Cd (II) ions from aqueous solutions. Batch equilibrium studies were carried out as a function of pH, initial metal concentration and contact time to determine the efficiency of biosorbent. The highest Cd (II) ions removal yield was achieved at pH 7.0. Adsorption capacity of Cd increased from 2.48 to 9.81 mg/g. The maximum monolayer biosorption capacity, Qo, of biosorbent material was found as 37.7mg/g. Among the two widely used isotherms, namely the Langmuir and Freundlich models, the equilibrium experimental data better fitted the Freundlich isotherm. Three kinetic models, namely pseudo-first order, pseudo second order and intra-particle diffusion were used to describe the kinetics of Cd(II) ion biosorption on Cassia siamea. Pseudo second order was the best of the three kinetic models to successfully describe the biosorption.