Interaction of metals with humic acid isolated from oxidized coal

The sorption behaviour of divalent cations M+ (Cu, Pb and Zn) and trivalent cations M3+ (Fe, Al) with humic acid isolated from oxidized coal (Hazro,SE Anatolia,Turkey) was followed in aqueous solution. Coal humic acid and metal ion interaction was investigated with special emphasis on the effects of pH, metal ion concentration and humic acid concentration. It has been found that the interaction of humic acid with metal ions in solution increases with pH, decreases with metal ion concentration and increases with humic acid concentration. The differences in sorption ability of particular metal ions on oxidized coal-derived humic acid are Fe> Pb> Cu> Al> Zn and Fe> Pb> Al> Cu> Zn at pH 2.5 and 3.5, respectively, while they are Fe=Pb=Cu=Al> Zn at both pH 4.5 and 5.5. The interaction of some trivalent (Fe, Al) and divalent(Cu, Pb, Zn) metal ions with humic acid prepared from coal was also studied using FTiR spectroscopy. This has proven helpful with respect to metal binding to understand better the potential sites of binding within the humic acid. Infrared spectroscopy showed the participation of cOOH and OH groups in binding to the metal ions.