Ion exchange and adsorption of some heavy metals in a modified coconut coir cation exchanger

Potentiometric titration experiments were carried out to determine the relative ability of sodium and different heavy metal cations in replacing protons from ionogenic sites of a modified coconut coir cation exchanger. The relative preference for the cations follow the sequence: Na << Ca(II)< Mn(II)< Ni(II) < Cu (II)< Pb(II). This preferential series was confirmed by determining the concentrations of the divalent cations and sodium which were adsorbed by the material during the titration process. Adsorption isotherms at pH 4 and pH 6 were obtained to determine the Langmuir adsorption constants for the heavy metal cations. The adsorbent material adsorbed high amounts of Pb(II), Cu(II) and Ni(II) (in decreasing order) from solutions whose concentrations were comparable to those of wastewaters. Our results show that the modified coconut coir cation exchanger has good potential as an adsorbent of heavy metals in industrial wastewaters. Copyright (C) 1996 IAWQ. Published by Elsevier Science Ltd.