Novel Cross-Linked Polyphosphonate for the Removal of Pb2+ and Cu2+ from Aqueous Solution

A novel cross linked polyzwitterionic acid (CPZA) was synthesized via cyclopolymerization of diallylaminomethylphosphonic acid (90 mol %) and 1,1,4,4-tetraallylpiperazinium dichloride (10 mol %), a cross linker, with sulfur dioxide in the presence of azoisobutyronitrile (AIBN) in dimethylsulfoxide (DMSO) at 65 degrees C. CPZA, upon treatment with NaOH, was converted into a cross linked anionic polyelectrolyte (CAPE). The experimental data for the adsorption of Pb2+ and Cu2+ on CAPE fitted the Lagergren second order kinetic model as well as Langmuir and Freundlich isotherm models. The adsorption capacity of Pb2+ was higher than that of Cu2+, and the rate of adsorption of both metals was found to be almost equal. The maximum adsorption capacity of Pb2+ and Cu2+ were determined to be 2.76 and 2.22 mmol g(-1), respectively. The adsorption process was spontaneous and endothermic in nature with negative and positive values for Delta G and Delta H, respectively. The relatively low activation energies of 25.5 and 27.1 kJ/mol for Pb2+ and Cu2+, respectively, indicated the adsorption as a favorable process. The excellent adsorption and very good desorption efficiency implied the efficacy of the resin in removing as well as recovering the metal ions from aqueous solution. An efficient synthetic access to the resin would enable its use in the treatment of contaminated wastewater.