Adsorption of Hexavalent Chromium from Aqueous Solution by Pumice: Equilibrium and Kinetic Study

Abstract

Chromium released into the environment primarily as a result of industrial activity such as leather and electroplating manufacturing process. This heavy metal has caused serious contaminations of water and soils with significant environmental and occupational concerns. Conventional methods of chromium removal are expensive especially for developing countries. This study investigates the use of pumice as a low cost and biosorbent material. Sorption of hexavalent Chromium (Cr (VI) onto pumice were carried out in batch at room temperatures, with parameters of initial chromium concentrations, and contact time being investigated. Removal of hexavalent chromium increased by increasing contact time, and reduced with increasing initial chromium concentration. Kinetic studies were conducted using the Pseudo-first-order and Pseudo-second- order models, while equilibrium data were fitted using Langmuir and Freundlich isotherm models. Fittings of obtained data onto kinetic models show that the pseudo-second –order kinetic model (R2=0.999) best describes the kinetic sorption of chromium ions onto pumice. Results also showed that Langmuir (R2=0.999) and Freundlich (R2=0.999) model agrees very well with experimental data. The RL and n values has proved the favorability of hexavalent chromium adsorption onto pumice