Engineering TiO2 supported CTAB modified bentonite for treatment of refinery wastewater through simultaneous photocatalytic oxidation and adsorption

Abstract

This study reports the removal of hydrocarbon pollutants from petroleum refinery wastewater by simultaneous photo-catalytic oxidation and adsorption using TiO2 loaded on Cetyl-trimethyl Ammonium bromide modified Bentonite clay (TiO2/CTAB-Bt). The synthesized CTAB-Bt and hybrid TiO2/CTAB-Bt were characterized by XRD, SEM, EDX, and FTIR techniques. The adsorption efficiency of CTAB-Bt was investigated using model refinery wastewater containing phenol, benzene, toluene, and naphthalene (100 ppm each). Under the optimum conditions of 0.8 g/100 mL CTAB-Bt adsorbent dosage, 40 °C, and 120 min contact time, maximum adsorption of hydrocarbons (94%) was attained. The adsorption followed pseudo-first-order kinetics and best fitted with the Langmuir isotherm model. Enthalpy (ΔH°), Gibbs free energy (ΔG°) and entropy (ΔS°) data of the system revealed that the adsorption process was endothermic, spontaneous and feasible. Through simultaneous photocatalytic oxidation under UV light irradiation and adsorption using TiO2/CTAB-Bt, the maximum removal (93%) of hydrocarbons from the model wastewater was achieved under milder conditions of 1100 mg/500 mL of TiO2/CTAB-Bt, 30 °C temperature and 60 min contact time. In the case of real refinery wastewater, CTAB-Bt realized 92% decrease in the COD via adsorption at 40 °C in 120 min, while simultaneous photocatalytic oxidation and adsorption achieved 94% decrease in COD at 30 °C in 60 min. The reaction products of photocatalytic oxidation of refinery wastewater were analyzed by GC–MS analysis. This study reports a new and interesting strategy of photocatalytic oxidation and adsorption for the remediation of hydrocarbon pollutants from refinery wastewater using CTAB-Bt.