Removal and recovery of phosphate ions from aqueous solutions by amine functionalized epichlorohydrin-grafted cellulose

A novel cellulose grafted epichlorohydrin functionalized polyethylenimine (Cell-g-E/PEI) graft copolymer was synthesized using cellulose, epichlorohydrin and polyethylenimine in the presence of azetobis isobutyro nitrile (AIBN) as the initiator and N,N'-Methylene bisacrylamide (MBA) as the crosslinking agent. The graft copolymer. Cell-g-E/PEI was characterized using TGA/DTG, XRD, FTIR, and SEM-EDS to evaluate the structural and morphological characteristics of the graft copolymer. The effectiveness of the Cell-g-E/PEI, as adsorbent for the removal and recovery of phosphate ions from aqueous media was studied. The effects of pH, contact time, and initial sorbate concentration were studied to optimize the conditions for maximum adsorption. The adsorption process, which was pH dependent, shows maximum removal (>99.0%) at pH 4.5. Kinetic study showed that 180 min of contact at 100 mg/L could adsorb about 99.6% of phosphate onto Cell-g-E/PEI. A pseudo-second-order kinetic model described successfully the kinetics of sorption of phosphate. Adsorption equilibrium data were correlated with the Langmuir. Freundlich and Redlich-Peterson isotherm models. The best fit was obtained with Freundlich model. Desorption of phosphate was studied by using 0.1 M HCl. Adsorption/desorption for more than six cycles showed the possibility of repeated use of this graft copolymer for the removal and recovery of phosphate from aqueous solutions. (C) 2011 Elsevier B.V. All rights reserved.