Removal of Lead, Zinc and Nickel Using Sodium Bentonite Activated Clay

Abstract

Bentonite collected from Zaghouan (Middle East Tunisia) was reacted with boiling 3M HCl solution at 0.5, 2, 4 and during 6 h. The structural change was studied, cation exchange capacity (CEC) decreased with the increase of the time treatment while specific surface area increase and it's maximum value was attained by the sample treated at 4 h. The chemical and structural characteristics of the purified natural and modified clays were determined. The amount of iron, aluminum and magnesium compounds decreased in the modified clay. Use of purified and modified bentonite clay by HCl (3M) for the removal of some heavy metals (Zn, Pb, Ni) from aqueous solutions has been investigated. They are the most impurities of industrials effluents. The uptake capacity of the modified clay for nickel, zinc and lead did significantly decrease with increase of the time treatment. The sorption process is reflected by Langmuir and Freundlich-type isotherm. The order of the removal capacity is Pb²⁺ > Zn²⁺ > Ni²⁺ for both natural and treated sorbents. Equilibrium modeling of the adsorption showed that the adsorption of these three metals was fitted to a Freundlich isotherm in all cases.