Investigation of ion adsorption properties of sulfobetaine gel and relationship with its swelling behavior

The adsorption of cations and anions in nitrate solutions on N,N-dimethyl(acrylamidopropyl)ammonium propane sulfonate (DMAAPS) gels prepared using various cross-linker and monomer concentrations was investigated. The influence of the temperature and nitrate concentration on the adsorption properties of the gel was evaluated, demonstrating simultaneous adsorption of cations and anions. The amount of Zn2+ adsorbed on the gel in Zn(NO3)2 solution increased as the cross-linker and monomer concentrations used in the gel preparation increased. For the gel prepared using a higher cross-linker or monomer concentration, elevation of the temperature did not induce any significant change in the amount of Zn2+ adsorbed on the gel. Furthermore, for the gel prepared using a lower cross-linker or monomer concentration, the amount of Zn2+ adsorbed on the gel decreased significantly as the temperature increased. In addition, an interesting correlation between the degree of swelling of the gel and the amount of Zn2+ adsorbed on the gel was found. As the degree of swelling decreased, the adsorption amount increased to eventually achieve a constant value.