Separation of Cr(VI) From Aqueous Solutions by Natural Bentonite: Equilibrium Study

Abstract

Removing hexavalent chromium from contaminated wastewater is very important because of toxicity to living organisms. Chromium is carcinogenic and mutagenic in very low concentration values (sub-ppm). The ability of the natural mineral (bentonite) for adsorption of hexavalent chromium, Cr(VI), from aqueous solutions was investigated. The influence of different physical and physicochemical parameters (pH, amount of adsorbent, adsorbate initial concentration) was examined. For characterization of adsorbent, classical chemical analysis thermogravimetric analysis (DTA/TGA), XRD analysis, FTIR-analysis and determination of specific surface area by BET were performed. For quantitative monitoring of the dynamics of studied system for the presence of Cr(VI) ions in model solutions, the AAS and UV/Vis analysis were used. The obtained experimental results were used for modeling of the equilibrium of the process through the application of software package MATLAB/Curve Fitting Toolbox., Following adsorption isotherms: Langmuir, Freundlich, Langmuir-Freundlich and Redlich-Peterson, are applied for analyzing the equilibrium of adsorbtion system Cr(VI) ions – bentonite.