Untreated and silver impregnated groundnut husk carbon were tested for the removal of chromium(VI) [153]. Approximately, 97% of hexavalent chromium was removed at pH 3 within 5 h. It was found that adsorbents chemically modified with an oxidizing agent demonstrated better chromium(VI) removal as compared to untreated adsorbents in terms of their adsorption rate. It was concluded that groundnut husk carbon oxidized with silver treatment has higher chromium(VI) adsorption capacity. Activated carbon prepared from peanut shell (PAC) was used for the removal of Pb2+ from aqueous solution [154]. The impacts of the Pb2+ adsorption capacities on the acid-modified carbons oxidized with HNO3 were also investigated. A comparative study with commercial granular activated carbon (GAC) showed that PAC was 10.3 times more efficient compared to GAC based on Langmuir maximum adsorption capacity. Further analysis results by the Langmuir equation showed that HNO3 [20% (by mass)] modified PAC has larger adsorption capacity for Pb2+ from aqueous solution (ca. 35.5 mg/g). The adsorption capacity enhancement ascribed to pore widening, increased cation-exchange capacity by oxygen groups, and the promoted hydrophilicity of the carbon surface.