Removal of chromium (VI) ions from aqueous solutions by using Turkish montmorillonite clay: effect of activation and modification

This study provides information on the Cr(VI) adsorption potential of Turkish (Mihalıççık region) montmorillonite clay as an abundant, cost-effective and untried material. Batch adsorption trials of chromium were performed to investigate the effects of pH, contact time, and initial metal ion concentration. The adsorption was solution pH dependent and the maximum adsorption was observed at a solution pH of 1.0. Adsorption equilibrium was established in 7 h. Langmuir, Freundlich and Dubinin–Radushkevich isotherm models were used to evaluate the equilibrium data at 20°C and regression coefficients were derived. Adsorption kinetics was analyzed using the firstorder and the pseudo-second-order kinetic models. Also, the effects of activation and modification on the adsorption capacity of clay were investigated under optimum conditions. Adsorption capacity of modified clay with hexadecyltrimethylammonium bromide was higher than that of acid and heat treated ones.