Kinetics of sorptive removal of chromium(VI) from aqueous solutions by calcined Mg–Al–CO3 hydrotalcite

The sorptive removal of hexavalent chromium from aqueous solutions by calcined Mg–Al–CO3 hydrotalcite was investigated in a batch mode. The influence of agitation speed, solution pH, initial chromium concentration, sorbent concentration and temperature has been tested in kinetic runs. Three kinetic models have been evaluated to fit the experimental data: the pseudofirst order, the modified-second order and the Elovich equation. It was shown that the first-order model could best describe the sorption kinetics. A Freundlich isotherm was used to fit equilibrium experiments. Hydrotalcite presents a sorption capacity of approximately 120 mg Cr/g, under the investigated experimental conditions. The calculated activation energy for process studied was around 40 kJ/mol.