The competitive heavy metal removal by hydroxyethyl cellulose-g-poly(acrylic acid) copolymer and its sodium salt: The effect of copper content on the adsorption capacity

Abstract

Crosslinked hydroxyethyl cellulose-g-poly(acrylic acid) (HEC-g-pAA) graft copolymer was prepared by grafting of acrylic acid (AA) onto hydroxyethyl cellulose (HEC) using [Ce(NH4)2(NO3)6]/HNO3 initiator system in the presence of poly(ethyleneglycol diacrylate) (PEGDA) crosslinking agent in 1:1 (v/v) mixture of methanol and water at 30 °C. Carboxyl content of copolymer was determined by neutralization of –COOH groups with NaOH solution and sodium salt of copolymer (HEC-g-pAANa) was swelled in distilled water in order to determine the equilibrium swelling value of copolymer. Both dry HEC-g-pAA and swollen HEC-g-pAANa copolymers were used in the heavy metal ion removal from three different aqueous ion solutions as follows: a binary ion solution with equal molar contents of Pb2+and Cd2+, a triple ion solution with equal molar contents of Pb2+, Cu2+ and Cd2+, and a triple ion solution with twice Cu2+molar contents of Pb2+and Cd2+. Higher removal values on swollen HEC-g-pAANa were observed in comparison to those on dry polymer. The presence of Cu2+decreased the adsorption values for Pb2+ and Cd2+ ions on both types of HEC copolymer. However, with further increase in Cu2+ content both dry and swollen copolymers became apparently selective to Cu2+ removal and Cu2+ removal values exceeded the sum of adsorption values for Pb2+ and Cd2+. Maximum metal ion removal capacities were 1.79 and 0.85 mmol Me2+/gpolymer on swollen HEC-g-pAANa and dry HEC-g-pAA, respectively.