Adsorption of mercury, lead and cadmium ions on modified activated carbons

Steam-activated and zinc chloride-activated carbons were prepared from rice husks. These carbons were modified by treatment with different concentrations of sulphuric acid. The adsorption of Hg2+, Pb2+ and Cd2+ ions from aqueous solution at 298 K on to these carbons has been investigated. The effect of pH on the adsorption capacity has also been studied. The adsorption isotherms obtained were of the Langmuir type, the application of the Langmuir equation allowing the determination of the adsorption capacities. The chemistry of the carbon surface is a prominent factor which determines the removal capacity for these metal ions. In contrast, the extent of the surface is not a controlling factor in this regard.