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

¹Department of Chemistry, University of Allahabad, Allahabad 211 002, India

²Indian Institute of Technology Kanpur, Kanpur 208016, India

Adv. Mater. Lett., 2015, 6 (1), pp 19-26

DOI: 10.5185/amlett.2015.5603

Publication Date (Web): Dec 28, 2014

Copyright © IAAM-VBRI Press

E-mail: singhvandanasingh@rediffmail.com

Abstract

This study puts forward the synthesis of an excellent cadmium adsorbent having unprecedented high capacity (Q_max = 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^-1min^-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.

Keywords

Tetraethylorthrosilicate, Cassia grandis-graft-polyacrylamide, Cd(II) adsorbent.