Ecofriendly k-Carrageenan-Based Hydrogel with Strong Adsorption and Higher Abilities to Remove Crystal Violet from Aqueous Solution: Thermodynamic, Isotherm and Kinetic Investigation

A semi-natural composite of k-Carrageenan and zinc oxide as a natural bio-polymer was prepared using a free radical copolymerization method. The k-carrageenan grafted poly (acrylic acid-co-acrylamide)/ZnO hydrogel nanocomposite is prepared by using N, N-methylene bis-acrylamide (MBA) as a cross-linked, and potassium persulfate (KPS) as initiator, the prepared surface using for the removal of the cationic dye crystal violet (CV) as a model of textile dyes pollutant from aqueous solutions. The hydrogel nanocomposite was characterized using XRD, FTIR, FE-SEM, HRTEM, and BET, which established a successful synthesis of the nanocomposite. Results show the prepared nanocomposite had a high swelling percentage of 3450%. The best removal efficiency is 93.23% for 600 mg/L at the adsorbent doses of 0.06 g/100 ml at an equilibrium time of 60 min. The fitting of equilibrium data to the Freundlich isotherm model best represents the adsorption of CV dye onto nanocomposite with a maximum multilayer adsorption efficiency of 932.22 mg/g. The pseudo-first-order and pseudo-second-order, chemisorption, and intra-particle diffusion kinetic models were applied to test the experimental result, and the first-order kinetic exhibited the best fit for the kinetic studies. Thermodynamic parameters were calculated to confirm that the adsorption process was endothermic and spontaneous. Additionally, the results showed that the nanocomposite could be effectively recycled for six consecutive cycles, with high efficiency for removing CV dye. Therefore, the nanocomposite proves to be a cost-effective and environmentally friendly option for removing CV from water solutions.