Green magnetic clay nanocomposite based on graphene oxide nanosheet as a synthetic low-cost adsorbent for oil droplets removal from produced water

A green magnetic nanocomposite based on kaolin clay and two-dimension graphene oxide (Fe3O4@ GO@Ka) was prepared using natural, economic, and available raw materials for oil removal from produced water. The preparation was carried out through a two-step hydrothermal carbonization method followed by a modified co-precipitation method in the presence of a kaolin clay matrix. Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, Brunauer–Emmett–Teller, and vibrating-sample magnetometer, were used to characterize Fe3O4@GO@Ka. The batch experiments results revealed that the oil removal efficiency reached its maximum with contact time = 60.0 min, pH = 7.0, initial oil concentration = 25.0 mg/L, the composite quantity = 5.0 mg, and T = 35°C. Theoretical models were applied to examine and assess the adsorption kinetics and isotherm. The adsorption kinetic was found to follow the pseudo-second-order, implying that the emulsified oil adsorption mechanism is chemisorption. The isothermal results closely matched the Freundlich isotherm model, meaning that the adsorption occurs in multilayers on a heterogeneous surface. Thermodynamic studies indicated that the adsorption process was spontaneous and endothermic. The prepared nano-composite was regenerated using ethanol and reused four times without a significant decrease in its oil removal efficiency. These results indicated that Fe3O4@GO@Ka could be a promising, eco-friendly adsorbent for removing emulsified oil droplets.