Optimization of swelling and mechanical behavior of novel pH-sensitive terpolymer biocomposite hydrogel based on activated carbon for removal brilliant blue dye from aqueous solution

In this study, biodegradable terpolymeric composite hydrogel was developed having swello-mechanical properties. The terpolymer biocomposite hydrogel Poly(CMC-co-AM-co-ITA)/AC was prepared by free radical co-polymerization of Carboxymethyl Cellulose (CMC), Itaconic acid (Doondani in Water 14: 3411, 2022), and acrylamide(AM) using potassium persulfate (KPS) as initiator and N, N-methylene bis-acrylamide(MBA) as cross-linker of the reaction. The synthesized Poly(CMC-co-AM-co-ITA)/AC terpolymer biocomposite was characterized by (FTIR), (FESEM), (HRTEM), (XRD), (TGA) and (BET), was used for the adsorptive removal of Brilliant blue (Norouzi in Mater Chem Phys 305 127918, 2023) dye from aqueous solution. There have been many attempts for the usage of hydrogels to removal dye because of their pH-responsive swelling behavior, thus dynamic swelling behavior of terpolymer biocomposite was investigated to determine the mechanism of water transport through these hydrogels. The exponential relation of the Fickian diffusion law describes the Fickian or non-Fickian behavior of swelling polymer networks. The Percent Swelling % of terpolymer biocomposite were studied at natural pH in tap water and distilled water, the swelling % of the terpolymer was 2100% in tap water and 3900% in distilled water at pH 7. The swelling % and adsorption efficiency increased with the increase in pH solution. Freundlich isotherm model and pseudo-second-order kinetic models were found to be best in fitting the isotherm and kinetics data. The Gibbs free energy, enthalpy, and entropy of adsorption showed that the adsorption was spontaneous, endothermic, and entropy-increasing process. The maximum capacity of adsorption for BB dye was 1565.611 mg/g and almost 100% removal efficiency within 1 h adsorption time at pH 7 and 25°C. The interaction mechanism between the adsorbate and the biocomposite surface involved main interactions, such as electrostatic interaction, π-π interactions and hydrogen bonding. The terpolymer biocomposite was successfully regenerated utilizing hydrochloric acid with more than 80% removal efficiency after the sixth cycle.