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) was 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 produced 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.