Photocatalytic oxidative degradation of hydrocarbon pollutants in refinery wastewater using TiO2 as catalyst.

This study reports the photocatalytic oxidative degradation of hydrocarbon pollutants present in refinery wastewater under UV light using Fe2 O3 , MnO2 , TiO2 , and ZnO as catalysts. Among the catalysts, TiO2 exhibited the highest photocatalytic degradation activity, that is, 92, 98.8, 91.5, and 93% conversion for benzene, toluene, phenol, and naphthalene, respectively, in the model refinery wastewater under the optimum reaction conditions of pH 3, 30°C, 90-min reaction time, and 100 mg/L catalyst dose. The photocatalytic degradation of a real refinery wastewater sample containing 69.23% aliphatics, 25.36% aromatics, 3.2% oxygenates, and 2.21% naphthenic hydrocarbons under the optimum conditions revealed a net decrease in chemical oxygen demand (93.2%), that is, from 970 mg/L to 65 mg/L. GC-MS analysis of the reaction products confirmed that using UV/TiO2 system, complete photodegradation of the parent hydrocarbons occurred, but some oxygenated byproducts were also observed. This study provides useful reference information for the treatment of wastewater from oil refineries to cope with the increasing environmental issues. PRACTITIONER POINTS: Benzene, toluene, phenol and naphthalene were successfully degraded by UV/TiO2 system, under 30°C, 1 hr, pH 3 and 100 mg catalyst. Photocatalytic oxidation of Refinery wastewater (Attock Oil refinery, Pakistan), UV/ TiO2 system resulted in 93.92% COD removal. GC-MS analysis shows complete removal of parent hydrocarbons from refinery wastewater, leaving only traces of oxygenated hydrocarbons as oxidation byproducts.