Synthesis, characterization and applications of itaconic acid-chitosan based hydrogels

In this study, chitosan-based itaconic acid (IA)-acrylamide (AAm)-N-t-butyl acrylamide (N-t-BAAm) semi-IPN hydrogels were synthesized. Ammonium persulfate was used as an initiator and methylene bisacrylamide as the crosslinker in the synthesis carried out by solution polymerization technique. The swelling behavior of the synthesized hydrogels and the parameters affecting the swelling capacity (temperature, molar ratios of the monomers used, chitosan, different pH environments and crosslinker concentrations) were investigated. The studies showed that the swelling capacity of the hydrogel decreased as the temperature increased and the synthesized hydrogel was a negative temperature sensitive gel. The swelling rate and capacity of the hydrogel increased as the pH increased. The swelling kinetics and diffusion kinetics of the hydrogels were also performed. Diffusion studies using Fick's law of diffusion revealed that the diffusion exponent (n) for all gels had values in the range of 0.5 < n < 1.0. Based on this, it can be concluded that all synthesized gels exhibited non-Fick-type (disordered) diffusion. The synthesized hydrogels were used for the adsorption of methylene blue and crystal violet dyes. Adsorption studies revealed that the Langmuir isotherm was more suitable for both dyes. The effects of pH and temperature on adsorption were also investigated. It was observed that while the adsorption capacity decreased as the temperature increased, the capacity increased as the pH increased. It was also determined that the hydrogels' adsorption capacity for methylene blue was higher than their adsorption capacity for crystal violet. Key Words: Itaconic Acid, Chitosan, Acrylamide, Hydrogel, Adsorption, Methylene Blue.