Effective removal of lead ions using graphene oxide-MgO nanohybrid from aqueous solution: Isotherm, kinetic and thermodynamic modeling of adsorption

The graphene oxide (GO) and magnesium oxide (MgO) nanohybrid (GOMO) was prepared by simple precipitation method and has been successfully utilized for the removal of Pb(II) from the water. The synthesized GOMO nanohybrid was characterized by FTIR, XRD, SEM, EDX Raman, BET, and XPS analysis which indicated that GO was successfully decorated by MgO nanoparticles. The results of the adsorption experiments showed that the GOMO was an excellent adsorbent because of its high uptake capacity (190 mg/g) at a low dose (0.4 g/L) within 30 min of equilibrium time, 30 °C temperature, and 6.5 pH. The parameters affecting the adsorption i.e. pH, initial Pb(II) concentration, adsorbent dose, adsorption time, and temperature were optimized to achieve the maximum adsorption. The adsorption process was investigated by different diffusion models i.e. Mass transfer, Webber-Morris, and Boyd kinetic model which revealed that initially, the lead adsorption was governed by the external mass transfer which was followed by intraparticle diffusion. The experimental data fit well with the Langmuir, and D-R isotherm model which suggested the monolayered way of the adsorption and chemical nature of adsorption respectively. The evaluation of thermodynamic parameters (ΔG°, ΔH°, and ΔS°) from Van't Hoff equation indicated the spontaneous and endothermic nature of the adsorption.