Cost-effective synthesis of magnetic graphene oxide nanocomposite from waste battery for the removal of arsenic from aqueous solutions: Adsorption mechanism with DFT calculation

Abstract

In this study, magnetic graphene oxide (MGO-Fe₃O₄) nanocomposite was prepared by co-precipitating of FeCl₃.6H₂O and FeCl₂.4H₂O on waste battery-derived graphene oxide and used as an adsorbent for the efficient removal of As(III) from aqueous solutions. The prepared nanocomposite was characterized by Fourier transformed infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, zeta potential, and a vibrating sample magnetometer. These characterizations revealed that spare like Fe₃O₄ nanoparticles (10.5 nm) were decorated on graphene oxide nanosheets and showed excellent saturation magnetization (89.73 emu/g). The adsorption of As(III) by MGO-Fe₃O₄ was optimized by analyzing various parameters. Experiments showed that 98 % of As(III) was removed at neutral pH in a just 20 min, even though the adsorbent dose was only 0.14 g/L. The adsorption kinetic and isotherm were best fitted with the pseudo-second order kinetic and Frendlich isotherm model. The maximum adsorption capacity (q_max) was found to be 50.2 mg/g at room temperature. Thermodynamic studies showed that the As(III) adsorption process was spontaneous and exothermic in nature. The enhanced adsorption capacity and magnetic properties of MGO-Fe₃O₄ are crucial in the drinking water treatment process due to the easy magnetic separation of MGO-Fe₃O₄ from aqueous solution after the adsorption process. Density Functional Theory (DFT) was also used to investigate the interaction between MGO-Fe₃O₄ and As(III), which further suggested that MGO-Fe₃O₄ and As(III) mostly interact with each other through surface complexation and hydrogen bonding.