Role of heteroatoms in activated carbon for removal of hexavalent chromium from wastewaters.

Heteroatoms are elements including sulfur, nitrogen, oxygen and hydrogen which are found on the surface of activated carbons. This study investigated the surface modification arising from heteroatoms bonding to carbon aromatic rings within the activated carbon and their corresponding influence on the chromium adsorption process. Activated carbons were prepared from bagasse by physical. Chromium removal capacities of these activated carbons by adsorption and reduction were determined. Models which related the chromium adsorption and reduction capacities of activated carbons to carbon acidity and heteroatom site concentrations were established using multi-variable linear regression method. It was found the individual heteroatoms contributed separately to the basicity of the carbon which in turn determined the mechanism by which chromium was removed from solution. The surface areas of the carbons were also observed to influence the adsorption and reduction of chromium. These understandings provide the fundamental method of optimising chromium removal through suitable control of carbon surface chemistry and textural properties.