Adsorptive Removal of Pb (II) by Using Graphene Oxide-Impregnated Calcium Alginate Hydrogel Beads

The adsorption performance of graphene oxide-impregnated calcium alginate hydrogel beads (GAB), successfully generated from laboratory-synthesized graphene oxide, was investigated in removing Pb (II) from the aqueous solution. The impact of parameters, such as initial pH, GAB dose, temperature, contact time, and salt concentration on Pb (II) adsorption was studied across wide ranges. The pseudo-second-order kinetic model (R-2 > 0.98) and Langmuir adsorption isotherm (R-2 > 0.99) were found suitable for best curve fitting of kinetic and thermodynamic analyses, respectively. GAB exhibited a maximum adsorption capacity of 138.88 mg/g at pH 6.5 and 298 K. The effective mass transfer diffusivity and external mass transfer coefficient of Pb (II) diffusing in GAB were ascertained utilizing the unreacted shrinking core model. Fourier Transform Infrared Spectroscopy (FTIR) indicated that the oxygen-containing groups of the surface of the bead composite acted as active sites for Pb (II) adsorption. Based on the thermodynamic parameters, it was determined that the adsorption process for GAB was endothermic (Delta H = 208.35 kJ/mol) and spontaneous (Delta G = - 8.42 kJ/mol at 298 K).