Competitive removal of heavy metal ions by cellulose graft copolymers

Abstract

The effect of composition of graft chains of four types cellulose graft copolymers on the competitive removal of Pb2+, Cu2+, and Cd2+ ions from aqueous solution was investigated. The copolymers used were (1) cellulose-g-polyacrylic acid (cellulose-g-pAA) with grafting percentages of 7, 18, and 30%; (2) cellulose-g-p(AA-NMBA) prepared by grafting of AA onto cellulose in the presence of crosslinking agent of NN'-methylene bisacrylamide (NMBA); (3) cellulose-g-p(AA-AASO(3)H) prepared by grafting of a monomer mixture of acrylic acid (AA) and 2-acrylamido-2-methyl propane sulphonic acid (AASO(3)H) containing 10% (in mole) AASO(3)H; and (4) cellulose-g-pAASO(3)H obtained by grafting of AASO(3)H onto cellulose. The concentrations of ions which were kept constant at 4 mmol/L in an aqueous solution of pH 4.5 were equal. Metal ion removal capacities and removal percentages of the copolymers was determined. Metal ion removal capacity of cellulose-g-pAA did not change with the increase in grafting percentages of the copolymer and determined to be 0.27 mmol metal ion/g(copolymer). Although the metal removal rate of cellulose-g-p(AA-NMBA) copolymer was lower than that of cellulose-g-pAA, removal capacities of both copolymers were the same which was equal to 0.24 mmol metal ion/g(copolymer). Cellulose did not remove any ion under the same conditions. In addition, cellulose-g-pAASO(3)H removed practically no ion from the aqueous solution (0.02 mmol metal ion/g(copolymer)). The presence of AASO(3)H in the graft chains of cellulose-g-p(AA-AASO(3)H) created a synergistic effect with respect to metal removal and led to a slight increase in metal ion adsorption capability in comparison to that of cellulose-g-pAA. All types of cellulose copolymers were found to be selective for the removal of Pb2+ over Cu2+ and Cd2+. (C) 2003 Wiley Periodicals, Inc.