Anionic dye uptake via composite using chitosan-polyacrylamide hydrogel as matrix containing TiO2 nanoparticles; comprehensive adsorption studies

In the present study, TiO2 nanoparticles dispersed in chitosan grafted polyacrylamide matrix (TiO2-PAM-CS) was synthesized using in situ technique, and applied for the uptake of Sirius yellow K-CF dye from aqueous solution. The synthesized nano-composite was characterized by FE-SEM, TEM, XRD and FT-IR analysis. The effect of significant parameters such as pH, dose, time and temperature in batch adsorption experiments were investigated. The adsorption process was pH dependent and the optimum value of pH was obtained 2 with 96.81% dye removal at 40 °C. The equilibrium data were compatible well with the Langmuir isotherm having qm value of 1000 mg/g. The Dubinin-Radushkevich (D-R) isotherm and thermodynamic studies prove that the adsorption is physical, endothermic and spontaneous. Kinetic study also verifies that pseudo second order kinetic model is the predominant model. The interactions between amin groups of polyacrylamide-chitosan (PAM–CS) composite in from of NH3+ and molecules of anionic dye via hydrogen bond formation (Dye-NH3+), also electrostatic interactions between Ti+4 available in PAM-CS composite and anionic dye (free energy of 1.66 kJ/mol calculated from D-R model) govern the adsorption mechanism. The reusability test showe that TiO2-PAM-CS composite can be renewed easily with HCl solution as an efficient adsorbent for practical wastewater treatment.