Synthesis of zeolite/activated carbon composite material for the removal of lead (II) and cadmium (II) ions

The present study reports the feasibility of synthesis of a new composite material containing zeolite (ZSM-5) and activated carbon that was prepared from custard apple shell powder. The process consisted of the following steps: preparation of activated carbon and subsequent steam assisted dry gel conversion of tetraethyl orthosilicate and sodium aluminate to ZSM-5 and ZSM-5 activated carbon composite. The resulting composite materials were characterized by X-ray diffraction, scanning electron microscope, and Brunauer-Emmett-Teller techniques. The co-ordination of the alumina incorporated was analyzed using Al magic angle spinning nuclear magnetic resonance. A comparative study among ZSM-5, ZSM-5 activated carbon composite, and mechanical mixture was executed toward sequestration of Pb2+ and Cd2+ ions from aqueous solution. The ZSM-5/activated carbon composite exhibited higher sequestration efficiency of lead (Pb2+) and cadmium (Cd2+) from aqueous solution and further from industrial effluents compared to other two sorbents. The ZSM-5/activated carbon composite exhibited selective adsorption toward Pb2+ ions compared to Cd2+ ions and other divalent metal ions.