Degradation of petroleum aromatic hydrocarbons using TiO2 nanopowder film.

The performance of a photo-reactor packed with titanium dioxide (TiO2) immobilized on glass beads, initiated by irradiation with natural and artificial ultraviolet (UV) sources, was evaluated in terms of the degradation efficiency of petroleum aromatic hydrocarbons. The effects of parameters such as pH, reaction time, hydrogen peroxide (H2O2) concentration and some ions were investigated. Additionally, the degradation of total organic carbon (TOC) and the formation of byproducts were studied. Photodegradation rates ofbenzene, toluene, ethylbenzene and xylenes (BTEX) by processes of UV/TiO2 and UV/TiO2/H2O2 were found to obey pseudo first-order kinetic models. Results indicated that the effect of pH value was negligible at the pH range of 5.5 to 8.5. TOC removal improved with addition of H2O2 demonstrating that a lack of hydrogen peroxide leads to incomplete mineralization. The effect of cations and anions on the photodegradation efficiencies of BTEX revealed that Mg2+ and Ca2+ caused the most deterioration in BTEX degradation efficiency. However S4O(2-) and CO3(2-) had the most salient inhibitory effects compared with other tested anions. The degradation efficiencies of both systems were investigated for the treatment of real polluted groundwater collected from the city of Tehran. Results showed that the degradation efficiencies of BTEX declined in the presence of inorganic and organic competitor species.