Adsorption characteristics of wheat bran towards heavy metal cations

Different-metal complexing ligands carrying synthetic and natural adsorbents have been reported in the literature for heavy metals removal. We have developed a new approach to obtain relatively high adsorption capacity utilizing wheat bran as a natural metal adsorbent. Adsorption equilibrium was achieved in about 10 min for all studied cations. The adsorption capacities are 93 mg/g for Cr(III), 70 mg/g for Hg(II), 62 mg/g for Pb(II), 21 mg/g for Cd(II), 15 mg/g for Cu(II) and 12 mg/g for Ni(II). The obtained results are an indication of higher specificity of the wheat bran for heavy metal cations compared with sodium and potassium ions. More than 82% of studied cations, except Ni(II), were removed from aqueous solution in single step. Matrix effect was not observed in most real samples in adsorption of cations by the studied sorbent. In this study no attempts were done in order to determine a mechanism for cations removal by the wheat bran, but it seems that complex mechanisms including ion exchange, complexation and size exclusion are possible. (C) 2003 Elsevier B.V. All rights reserved.