Radiation synthesis and application of a hydrogel based on acrylic acid and 2‐mercaptobenzimidazole

A hydrogel based on gamma‐radiation polymerization of acrylic acid (AAc) in the presence of 2‐mercaptobenzimidazole (MBI) and a crosslinking agent was prepared. The properties of this AAc/MBI hydrogel were characterized in terms of gel content, swelling in different solvents, structure morphology, and IR spectroscopy. Moreover, the thermal decomposition behavior of the prepared hydrogel was investigated by thermogravimetric analysis (TGA). The TGA thermograms were also used to determine the different kinetic parameters such as order of reaction and activation energy. The sorption of some divalent metal ions such as Cu2+, Pb2+, Cd2+, and Hg2+ by the AAc/MBI hydrogel also was studied. The results showed that the AAc/MBI hydrogel has a higher tendency to swell in water and polar solvents than in nonpolar solvents. The highest metal uptake by the hydrogel was found for Hg2+ and Cd2+, whereas the lowest was for Cu2+ and Pb2+ ions. The ratios between the distribution coefficients of the different metals [separation factors (SF)] indicate that the hydrogel has a high selectivity for Hg2+ over Cu2+ (SF = 10.923) and Pb2+ (SF = 19.110). However, the hydrogel prefers Hg2+ over Cd2+ (SF = 1.356) and showed a high selectivity for Cd2+ over Cu2+ (SF = 7.822) and Pb2+ (SF = 7.240).