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Solar-Chemical Treatment of Groundwater Contaminated with Petroleum at Gas Station Sites: Ex Situ Remediation Using Solar/TiO2 Photocatalysis and Solar Photo-Fenton

Groundwater samples contaminated by BTEX (benzene, toluene, ethylbenzene, xylene isomers and TPHs (total petroleum hydrocarbons) were treated with advanced oxidation processes (AOPs), such as TiO2 photocatalysis and Fe2+/H2O2 exposed to solar light (37°N and 128°E) with an average intensity of 1.7 mW/cm2 at 365 nm. These AOP processes showed feasibility in the treatment of groundwater contaminated with BTEX, TPH and TOC (Total Organic Carbon). Outdoor field tests showed that the degradation efficiency of each contaminant was higher in the Fe2+/H2O2 system without solar light compared to the TiO2/solar light and H2O2/solar light systems. However, the TiO2/solar light and the Fe2+/H2O2/solar light systems showed significantly enhanced efficiencies in the degradation of BTEX, TPH and TOC with the additional use of H2O2. Near complete degradation of BTEX and TPH was observed within 2 and 4 hrs, respectively, however, that of TOC was slower. Without pretreatment of the groundwater, fouling of the TiO2, due to the ionic species present, was observed within 1 hr of operation, which resulted in the inhibition of further BTEX, TPH and TOC destruction. The degradation rate of n-alkanes with carbon numbers ranging from C10 to C15 was relatively greater than that of n-alknaes with carbon numbers ranging from C16 to C20. From this work, the AOP process (Fe2+/H2O2/solar light and TiO2/H2O2/solar light) illuminated with solar light was identified as an effective ex situ technique in the remediation of groundwater contaminated with petroleum.