Synthesis of a new nanocomposite with the core TiO2/hydrogel: Brilliant green dye adsorption, isotherms, kinetics, and DFT studies

New SA-g-P(AAc-co-MA)/TiO2 nanocomposite was synthesized using the free radical graft copolymerization technique. The synthesized nanocomposite was characterized using FTIR, FE-SEM, XRD, TEM, TGA, and BET techniques. It was then utilized as an adsorbent for removing the Brilliant green (BG) dye from an aqueous solution. The effect of different factors like the initial concentration of the BG dye, pH of the solution, and temperature have been studied. The experimental results were analyzed via the isotherm Freundlich and Langmuir adsorption models. To have deep insight into the adsorption mechanism, the density functional theory (DFT) method was used. According to the analyses, the equilibrium results fitted completely with Freundlich isotherm; thus, the pseudo-first-order and pseudo-second-order kinetics and intra-particle diffusion models were utilized to determine the adsorption kinetic result. The optimal conditions for the studied parameters which revealed the highest adsorption were: T = 30 °C, pH = 3, ΔGo = −6.87 kJ.mol−1, ΔHo = 15.788 kJ.mol−1, and ΔSo = 93.92 J.mol−1.K−1. The kinetics adsorption was consistent with the pseudo-second-order kinetic model, and the above-mentioned thermo-dynamics variables, ΔGo, ΔHo, and ΔSo, suggested that the adsorption of Brilliant green dye on synthesized nanocomposite was spontaneous and endothermic.