Process modeling and kinetic evaluation of petroleum refinery wastewater treatment in a photocatalytic reactor using TiO2 nanoparticles

The photocatalytic oxidation and mineralization of petroleum refinery wastewater in aqueous catalyst suspensions of titanium dioxide (TiO2), Degussa P25 (80% anatase, 20% rutile), were carried out in a batch circulating photocatalytic reactor. The experiments were conducted based on a central composite design (CCD) and analyzed using response surface methodology (RSM). In order to analyze the process, four significant variables viz. pH (2–10), catalyst concentration (0–200 mg/l), temperature (22.5–52.5 °C), and reaction time (30–150 min) and TCOD removal as the process response were studied. From the data derived from the factorial design, the ANOVA analysis revealed that the first-order effects of reaction time, pH, temperature and catalyst concentration and second-order effect of pH, catalyst concentration and temperature produce the main effect on TCOD removal efficiency. A maximum reduction in TCOD of more than 83% was achieved at the optimum conditions (pH of 4, catalyst concentration of 100 mg/l, temperature of 45 °C and reaction time of 120 min). The reaction kinetics showed that reactive activation energy for TCOD conversion was calculated to be 19.34 kJ/mol.