Uptake of trivalent chromium ions from aqueous solutions using kaolinite

The sorption of Cr(III) from aqueous solutions on kaolinite has been studied by a batch technique. We have investigated how solution pH, ionic strength and temperature affect this process. The adsorbed amount of chromium ions on kaolinite has increased with increasing pH and temperature when it has decreased with increasing ionic strength. The sorption of Cr(III) on kaolinite is endothermic process in nature. Sorption data have been interpreted in terms of Freundlich and Langmuir equations. The adsorption isotherm was measured experimentally at different conditions, and the experimental data were correlated reasonably well by the adsorption isotherm of the Langmuir, and the isotherm parameters (qm and K) have been calculated as well. The enthalpy change for chromium adsorption has been estimated as 7.0 kJ mol−1. The order of enthalpy of adsorption corresponds to a physical reaction.