Cassia Grandis Seed Gum-graft-poly(acrylamide)-silica Hybrid: An Excellent Cadmium (II) Adsorbent

Abstract

This study puts forward the synthesis of an excellent cadmium adsorbent having unprecedented high capacity (Qmax = 5000 mg g -1 ) to capture cadmium ions from synthetic cadmium solution. To synthesize the adsorbent (A700), base catalyzed polymerization of tetra ethylorthosilicate (TEOS) was conducted under the sacrificial templation effect of poly(acrylamide) grafted Cassia grandis seed gum (CG) while using H2O, TEOS and EtOH in 8:1:1: ratio (v/v). The CG inspired adsorbent was characterized by FTIR, XRD and SEM, both before and after cadmium adsorption. The adsorption parameters for the synthesized adsorbent were optimized by performing the batch adsorption studies under different pH, initial cadmium concentration, adsorbent dose, and contact time. The adsorption showed pseudo second order kinetics with a rate constant of 1.55 x 10 -4 g mg -1 min -1 at 450 mg mL -1 Cd(II) concentration. The thermodynamic study showed that the adsorption is endothermic and spontaneous. The adsorbent could be successfully reused for three cycles. The present adsorbent is not only very efficient in cadmium uptake; it is greener than the contemporary porous silica adsorbents derived through templation of pure synthetic polymers or surfactants. Moreover the source polysaccharide used for its synthesis is abundant and cheap. This hybrid can utilized as versatile and sustainable adsorbent for cadmium recovery from industrial wastes. Copyright © 2015 VBRI Press.