As(III), As(V), Hg, and Pb Removal by Fe-Oxide Impregnated Activated Carbon

The removal of As(III), As(V), Hg(II), and Pb(II) by virgin and Fe(III) impregnated activated carbons (FeAC) was investigated. Iron-oxide impregnation increased the pHzpc of the carbon from 7.5 to about 8.2-8.7 but did not alter the surface area or the pore volume. The amount of acid or base needed to reach a given pH increased following impregnation, indicating that the FeAC was more active than its nonimpregnated counterpart. Metal removal was a function of pH with removal increasing with pH for Hg(II) and Pb(II) and decreasing with pH for As(V). As(III) removal was not a strong function of pH below pH = 5, increased to a maximum at pH (approximate)7, then decreased with increasing pH. As(III) and As(V) removals were about one and two orders of magnitude higher, respectively, for the FeAC compared with the nonimpregnated carbon, while Hg(II) and Pb(II) removals were only slightly higher. Feimpregnation appears to be most effective for the anionic contaminants.