The Sorption of Arsenic onto Activated Carbon Impregnated with Metallic Silver and Copper

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Abstract
The adsorption of arsenic species in aqueous solutions onto activated carbon with and without chemical impregnation has been studied. The ability of activated carbon to adsorb arsenic depends on the arsenic oxidation state, the pH of the water, and the activity of the metal used for the activated carbon impregnation. The results of the investigations have shown that physical adsorption is effective only for the arsenic(V) species in water. Activated carbon adsorbs arsenic(V) with a saturation adsorption capacity of 0.27 mmol/g. The chemisorption process is effective for both arsenic species. By impregnation of activated carbon by copper, the sorption process for the arsenic(III) species is significantly improved. The saturation adsorption capacity of the activated carbon impregnated by copper is 0.41 and 0.23 mmol/g for the arsenic(III) and arsenic(V) species, respectively. The pH values of the water are important for both sorption processes because of the change in the ionic forms of both arsenic species. The optimal pH range is between 4 and 9, which is a consequence of the apparent affinity between the carbon surface and arsenic species H3AsO3 and H2AsO4 − that are predominant at this pH in water. Equilibrium isotherm analyses were undertaken using Langmuir and Freundlich equations.