Competitive adsorption of Fe2+, Pb2+, and Zn2+ ions from multi-metal ion solution on ammonium oxalate modified kaolinite clay

Abstract

The competitive adsorption of Fe²⁺, Pb2⁺, and Zn²⁺ ions from mixed multi-metal aqueous solution on ammonium oxalate-modified kaolinite clay (AOK) was studied to determine the competitive influence of the metal ions on the adsorption of other metal ions. The kaolinite clay was modified by treating it with 0.2 M of ammonium oxalate solution at 50 ^oC. The adsorption of the metal ions was carried out using initial concentrations of 20, 35, and 50 mg L-1 in both the single and multi-metal ion solutions. The results revealed that at a low concentration of 20 mg L^-1, the adsorption capacity for the uptake of the metal ions on AOK is non-competitive. At higher adsorbate concentrations of 35 and 50 mg L^-1, the single to multi-metal ions equilibrium adsorption capacity ratio value obtained was less than 1. This indicated an antagonistic effect on competing for the adsorption site in the following order: Pb²⁺ (9.9 mg g^-1) > Fe²⁺ (3.85 mg g^-1) > Zn²⁺ (2.85 mg g^-1). The outcome revealed that ammonium oxalate-modified kaolinite is a potential adsorbent for remediation of multi-heavy metal-laden wastewater with preferentially higher affinity for Pb²⁺ ions than other metal ions.