Binding of heavy metal ions by formaldehyde‐polymerized peanut skins

Peanut skin, when treated with formaldehyde to polymerize tannins, is a highly efficient substrate for removal of many heavy metal ions from aqueous waste solutions. The ions Ag 1+ , Cd 2+ , Cr 6+ , Cu 2+ , Hg 2+ , Ni 2+ , Pb 2+ , Zn 2+ , as well as Ca 2+ and Mg 2+ , were contacted with formaldehyde‐treated peanut skin. Quantitative removal could be achieved with Ag 1+ , Cd 2+ , Cu 2+ , Hg 2+ , Pb 2+ , and Zn 2+ . Capacity of the substrate for ions was promising for Pb 2+ (2.1 meq/g substrate), Cu 2+ (3.0 meq/g), and Cd 2+ (1.3 meq/g). Sorption from a solution containing Cd 2+ , Cu 2+ , Hg 2+ , Ni 2+ , Pb 2+ , Zn 2+ , on a packed column of formaldehyde‐treated peanut skin indicated that Hg 2+ , Pb 2+ , and Cu 2+ were rapidly and completely bound to the packing, while Cd 2+ , Ni 2+ , and Zn 2+ were poorly bound until the preferred ions had been removed from solution.