Thermosensitive and chitosan of crab (Portunus pelagicus) shells gel based adsorbent for reversible adsorption-desorption of several toxic metal ions

Indonesia experiences environmental pollution because of wastewater treatment problems. Such occurrence is affected by the heavy metal waste produced by the electroplating industry, one of them is ferrous and nickel. Thus, heavy metal waste needs to be regenerated through a method by using zwitterionic betaine gel. However, this method has weakness in the form of intra-intrachain associations which occurs and becomes the obstacle for the ionic group's ions adsorption ability by the charge group interaction. The purpose of this research was to increase the adsorption ability of the gel by removing the intra-intrachain copolymers association through conducting a synthesis of both the anionic gel N-isopropyl acrylamide (NIPAM) copolymerized with acrylic acid (NIPAM-co-acrylic acid) and cationic gel (NIPAM-co-chitosan), separately. The synthesis of the gels was conducted through a polymerization reaction using accelerator in the form of N, N, N', N'-tetramethylethylenediamine (TEMED), an initiator ammonium peroxodisulfate (APS) and a cross-linker in the form of N, N'-methylenebisacrylamide (MBAA). In this research, the metal ions adsorption by pH-thermosensitive gel was conducted in various pH and weight balance between NIPAM-co- anionic and NIPAM-co-cationic gel provided. The effects of the temperature and the conditions provided in the gel preparation were also investigated, including the effect of monomer concentration on the metal ions adsorption on the gel. The gel adsorption behavior is discussed by considering the swelling degree of the gel as well as the transition temperature of poly(NIPAM-co-chitosan) and poly(NIPAM-co-acrylic acid). According to the results of FTIR analysis, the vinyl group peak of the copolymer gel decreased compared with that of its constituent monomers, thus the copolymers synthesis was successful. Meanwhile, based on the swelling degree test using the electroplating waste solution, the higher the solution's temperature, the lower the gel's swelling degree. In addition, the higher synthesis temperature also caused the occurrence of gel porous. The adsorption ability of the gels that have positive and negative charge groups synthesized separately is better than zwitterionic gels. The gel can adsorb more heavy metal ions at higher adsorption temperatures.