The effect of synthesis condition of the ability of swelling, adsorption, and desorption of zwitterionic sulfobetaine-based gel

This study explored the ion adsorption of heavy metals using a copolymer gel containing zwitterionic betaine N, N'-dimethyl(acrylamidopropyl)ammonium propane sulfonate (DMAAPS) as the ion adsorbent agent and N-isopropylacrylamide (NIPAM) as the thermosensitive agent. We investigated the effect of ion monomer concentration and type and of temperature on the adsorption, desorption, and swelling properties and their correlation. A free-radical polymerization reaction was performed to prepare the thermosensitive NIPAM-co-DMAAPS gel using accelerators such as N, N, N', N'-tetramethylethylenediamine, ammonium peroxydisulfate as the initiator, and N, N'-methylenebisacrylamide at a concentration of 10 mmol/L as the cross-linker. An analysis was then performed on the gel's adsorption, desorption, and reversible adsorption-desorption properties using atomic absorption spectrophotometry. The results showed that the swelling degree and adsorption values increased as the temperature decreased in the gel with NIPAM:DMAAPS ratios of 9:1 and 8:2. In contrast, in a 7:3 ratio, the swelling degree increased significantly, and the adsorption ability decreased as the temperature increased. The higher the temperature, the smaller the quantity of Zn²⁺ and Pb²⁺ ions adsorbed and desorbed. The results indicate that in nitrate solution, Pb²⁺ ions are more easily adsorbed than Zn²⁺ ions.