Radiation grafting of 4-vinylpyridine onto PP-g-AAc hydrogel films, and its copper (II) complexes

Complete text of publication follows. A new polymeric system consisting of a comb type copolymer of 4VP onto PAAc hydrogel, grafted onto PP film net-(PP-g-AAc)-g-4VP, was synthesized by gamma radiation in three consecutive steps. This polymeric system has better mechanical properties that the studied hydrogels, pH sensitivity and the ability to form complex with transition metal ions. The synthesized system has chelating ability with transition metal ions due to its structure containing nitrogen and oxygen atoms. In this work we present the swelling behavior of the supported comb-type hydrogel and its complexes with copper (II) ions in acidic aqueous medium. These systems were studied by IR, UVVis and EPR spectroscopy. Two critical pH values were found for net-(PP-g-AAc)-g-4VP at 4.5 and 7.2. Adsorption capacity of Cu(II) ions by the system is 40 mg/g dry polymer, the capacity increases with the increase of pH. The FTIR spectrum of the supported comb-type hydrogel-copper (II) complex shows the appearance of carboxilate groups due to the ion exchange reaction between the supported comb-type hydrogel and Cu(II) ions. The results suggest pH dependence and a coordination mechanism through carboxylate groups of acrylic acid and the nitrogen atom of the pyridine groups of the supported comb-type hydrogel is propose. The chelating ability and pH-responsive behavior of synthesized system make it an attractive material for possible applications in adsorption, enrichment and separation processes from low level wastewater. The authors are grateful to PAPIIT-UNAM, IN200108; CONACyT and Posgrado de Ingenieria, Facultad de Quimica, for support and to S. Castillo, F. Garcia and B. Leal from the ICN-UNAM, for technical assistance.