Synthesis of zeolite/activated carbon composite material using custard apple shell for removal of heavy metal - Aqueous lead (II) and cadmium (II)

Abstract

Aim: A composite material was prepared containing zeolite (ZSM-5) and activated carbon (AC) that was prepared from custard apple shell powder. Materials and Methods: The process consisted of the following steps: Preparation of AC and subsequent steam assisted dry gel conversion of tetraethyl orthosilicate and sodium aluminate to ZSM-5 and ZSM-5 AC composite. Results: The resulting material exhibited a hierarchical pore structure with high surface area and porosity as characterized by X-ray diffraction and nitrogen adsorption. The addition of AC enhanced the surface area and adsorption percentage of lead (Pb2+) and cadmium (Cd2+) from aqueous solution and further from industrial effluents. The coordination of the alumina incorporated was analyzed using Al magic angle spinning nuclear magnetic resonance. ZSM-5/AC composite with high crystallinity was obtained which exhibited high adsorption rates when compared to ZSM-5, AC individually and their mechanical mixtures. Conclusions: As a significant application, the modified adsorbents with the composite materials were tried out on an industrial effluent to check the capability of the adsorbents in the removal of Pb2+ and Cd2+. It was observed that approximately 90% of the metal ions in question were removed by all the adsorbents tried out.