Zwitterionic betaine polymers are promising adsorbents for the removal of heavy metal ions from industrial effluents. Although the presence of both negative and positively charged groups imparts them the ability to simultaneously remove cations and anions, intra- and/or inter-chain interactions can significantly reduce their adsorption efficiencies. Therefore, in this study, novel gels based on crosslinked co-polymers of thermosensitive N-isopropylacrylamide (NIPAAM) and zwitterionic sulfobetaine N,N-dimethylacrylamido propyl ammonium propane sulfonate (DMAAPS) were synthesized, characterized, and evaluated for ion removal. Fourier-transform infrared (FTIR) and proton nuclear magnetic resonance (1H NMR) analyses confirmed the success of the co-polymerization of NIPAAM and DMAAPS to form poly(NIPAAM-co-DMAAPS). The phase transition temperature of the co-polymer increased with increasing DMAAPS content in the co-polymer, indicating temperature-dependent amphiphilic behavior, as evidenced by contact angle measurements. The ion adsorption analyses of the poly(NIPAAM-co-DMAAPS) gels indicated that co-polymerization increased the molecular distance and weakened the interaction between the DMAAPS-charged groups (SO3− and N+), thereby increasing the ion adsorption. The results confirmed that, with a low concentration of DMAAPS in the co-polymer gels (~10%), the maximum amount of Cr3+ ions adsorbed onto the gel was ~58.49% of the sulfonate content in the gel.

Industrial development has caused the metal concentration in the environment to increase. This is a serious issue considering that heavy metals are stable and cannot naturally decompose. Therefore, wastewater should be processed before being disposed to the environment. Several technologies have been developed for removing heavy metal content in industrial liquid wastes. The adsorption method using solid adsorbent is a simple and effective method for separating heavy metal ions from electroplating wastes since they are eco-friendly and efficient. However, they produce secondary wastes and require high operational costs. The blending of cationic gel NIPAM-co-Chitosan and anionic gel NIPAM-co-Acrylic Acid is a potential candidate as a new alternative adsorbent. By this method, the secondary wastes can be eliminated, adsorbed ions simultaneously, and adsorb-desorb ions reversibly. NIPAM-co-Chi and NIPAM-co-Acrylic Acid are synthesized from a polymerization reaction using N, N, N’, N’-tetramethylethylenediamine (TEMED) and sodium sulfite as accelerators, ammonium peroxodisulfate (APS) as an initiator, and N, N’-methylene bisacrylamide (MBAA) as a cross-linker. The gel was synthesized in a three-neck round flask for 6 hours. The product crush gel was then used for the adsorption and swelling degree test. The swelling degree test was performed by measuring the swelling gel volume before and after being soaked for 24 hours in target solutions. The gel obtained from the adsorption test was separated from the solution to be analyzed with Atomic Absorption Spectrophotometry (AAS). Based on the FTIR analysis of NIPAM-co-Chi and NIPAM-co-Acrylic Acid gels, there is no peak indicating the presence of vinyl C=C bonds. It can be concluded that the gel copolymer synthesis that was carried out was successful. The optimum results were obtained from the swelling degree analysis on electroplating waste at a concentration of 8:2.