Noncompetitive Removal of Heavy Metal Ions from Aqueous Solutions by Poly[2-(acrylamido)-2-methyl-1-propanesulfonic acid-co-itaconic acid] Hydrogel

Noncompetitive removal of Pb2+, Cu2+, and Cd2+ ions from aqueous solutions by the copolymer of 2-(acrylamido)-2-methyl-1-propanesulfonic acid with itaconic acid and its homopolymer poly[2-(acrylamido)-2-methyl-1-propanesulfonic acid] was investigated. Both poly[2-(acrylamido)-2-methyl-1-propanesulfonic acid] and poly[2-(acrylamido)-2-methyl-1-propanesulfonic acid-co-itaconic acid] removed the maximum and same amounts (1.74 mmol Pb2+/g polymer) of Pb2+ ion among the ions investigated in this work. The equilibrium swelling values of poly[2-(acrylamido)-2-methyl-1-propanesulfonic acid] and poly[2-(acrylamido)-2-methyl-1-propanesulfonic acid-co-itaconic acid] showed that the swelling of the copolymer is dominated by its completely ionizable constituent 2-(acrylamido)-2-methyl-1-propanesulfonic acid. Although the incorporation of itaconic acid into poly[2-(acrylamido)-2-methyl-1-propane sulfonic acid] did not affect the removal rates of poly[2-(acrylamido)-2-methyl-1-propanesulfonic acid-co-itaconic acid] for Pb2+ and Cd2+ ions, it considerably enhanced the removal rates of the copolymer for the Cu2+ ion. The trends in the single-ion sorption of ions on poly[2-(acrylamido)-2-methyl-1-propanesulfonic acid] and poly[2-(acrylamido)-2-methyl-1-propanesulfonic acid-co-itaconic acid] followed the orders Pb2+ > Cd2+ > Cu2+ and Pb2+ > Cu2+ > Cd2+, respectively. Noncompetitive adsorption profiles of Pb2+, Cu2+, and Cd2+ ions on both polymers were demonstrated to fit the pseudo-second-order-type kinetics.