Adsorption of chromium by natural and industrial materials

This paper analyses the thermodynamic aspects of ions adsorption on a granular activated carbon and a char derived from a South African applied to the removal of chromium from aqueous solution. Experiments have been carried out at ambient temperature, by varying pH and salinity levels. Redox reactions occurring between the superficial functional groups and the hexavalent chromium ions lead to the formation of trivalent chromium. Experimental results show that the activated carbon has a higher selectivity for chromate species while the char tends to adsorb trivalent chromium cations preferentially. Eventually the Langmuir model has been used for the interpretation of experimental results.