Treatment of soil washing wastewater via adsorption of lead and zinc using graphene oxide.

In the present work, graphene oxide (GO) was synthesized via the modified Hummers method and utilized in treating real soil washing wastewater via adsorptive removal of lead (Pb) and zinc (Zn). Characterization analysis of GO was performed using X-ray diffraction, Brunauer-Emmett-Teller method, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and zeta potential analysis. The Van't Hoff, Eyring, and Arrhenius equations were applied to determine the activation and thermodynamic parameters namely activation energy (Ea), standard Gibbs energy change (ΔG°), standard enthalpy change (ΔH°), standard entropy change (ΔS°), change in activation Gibbs energy (ΔG#), change in activation enthalpy (ΔH#), and change in activation entropy (ΔS#). Based on the high coefficient of determination values (0.8882 ≥ R2 ≥ 0.9094) and low values of SSE (0.0292 ≤ SSE ≤ 0.0511) and ARE (0.8014 ≤ ARE ≤ 0.8822), equilibrium data agreed well with the Freundlich isotherm. The maximum adsorption capacity for Pb(II) and Zn(II) was determined to be 11.57 and 4.65 mg/g, respectively. Kinetic studies revealed that pseudo-second-order equation fitted well with the experimental data, which indicates that chemisorption is the rate-determining step of the adsorption system. Results have shown the possibility of GO as a potential adsorbent material in the treatment of soil washing wastewater.