Retention of heavy metal ions on comb-type hydrogels based on acrylic acid and 4-vinylpyridine, synthesized by gamma radiation

• Radiation Processing was an easy way to synthesize the new studied systems.
• The best removal efficiency of Zn(II) was found in net(PP-g-AAc)-g-4VP.
• Experimental data were analyzed using isotherm and kinetic models even in ppm.
• The new polymer architectures considerably improve the retention of heavy ions.

Two novel comb-type hydrogels based on pH-sensitive monomers (acrylic acid (AAc) and 4-vinylpyridine (4VP)) were synthesized by gamma radiation. The systems were as follows: a) comb-type hydrogels of an AAc network followed by grafting of 4VP ((net-PAAc)-g-4VP) and b) comb-type hydrogels of an AAc network grafted onto polypropylene (PP) followed by grafting of 4VP (net-(PP-g-AAc)-g-4VP). The equilibrium isotherms and kinetics were evaluated for copper and zinc ions in aqueous solutions. The Zn(II) retention obtained was 480 mg g−1 and 1086 mg g−1 for (net-PAAc)-g-4VP and net-(PP-g-AAc)-g-4VP, respectively. At concentrations as low as ppm, retention efficiencies of approximately 90% were achieved for Cu(II) on (net-PAAc)-g-4VP and for Zn(II) on net-(PP-g-AAc)-g-4VP. Desorption of the hydrogels was also studied, and the results indicated that they can be used repeatedly in aqueous solutions. For both systems, the adsorption of Cu(II) and Zn(II) obeyed the Freundlich model, indicating heterogeneous sorption, and the retention process occurred by chemisorption. The sorption process follows a pseudo-second-order model.