Preliminary evaluation of polymeric Fe- and Al-modified clays as adsorbents for heavy metal removal in water treatment

This paper assesses the potential of modified montmorillonite clays as low-cost adsorbents/ion-exchangers for the removal of trace level heavy metals (Cd, Cu, Ni, Pb and Zn) from potable water. Modification of the montmorillonites resulted in the exchange of the interlayer calcium ions for the polymeric species. One unmodified montmorillonite and three polymeric Fe- and Al-modified montmorillonites have been evaluated with respect to their selectivity and uptake performance. All of the clays are selective for Pb and Cu adsorption from aqueous solutions at the mildly acidic pH range in which the experiments were performed (pH 5.5-6). Polymeric iron- and polymeric Al/Fe-modified clays had comparatively great affinities for all the metals studied, whilst the original and polymeric Al modified clays had relatively lower affinities. Only the uptake of Pb and Cu could be correlated with physical properties such as clay surface area. The metal selectivity could be correlated to the type of intercalated polymeric Fe and Al species of the modified clays. (C) 2002 Society of Chemical Industry.