Photochemical treatment of benzene, toluene, ethylbenzene, and xylenes (BTEX) in aqueous solutions using advanced oxidation processes: Towards a cleaner production in the petroleum refining and petrochemical industries

Current environmental initiatives and global demands for cleaner practices are driving the petroleum refining and petrochemical industries to consider greener methods for the treatment of their industrial wastewater. The photochemical degradation of benzene, toluene, ethylbenzene, and xylenes (BTEX) in petrochemical wastewater by UV/H2O2 and VUV/H2O2, with the UV light spectra that are centered at 254 and 185 nm, respectively, was investigated. Total organic carbon (TOC), biochemical oxygen demand (BOD), and pH were measured for the characterization of the wastewater and overall removal rates of organic materials. It was observed that the recommended H2O2 concentration to degrade a TOC inlet concentration of 100 mg/L of BTEX was 250 mg/L and 300 mg/L for UV-185 and UV-254 nm, respectively. Under acidic conditions at pH 3, the UV-185/H2O2 removed 10% total TOC more than that of the UV-254/H2O2 process. At the recommended H2O2 concentration, 90% of BTEX mineralization occurred with UV-185/H2O2 under acidic conditions (pH 3) with the residence time of 6 h. It was observed that the BOD5/TOC of BTEX was decreased by increasing the residence time (within 140 min) in the photoreactor. The use of AOPs for the treatment of BTEX in aqueous solutions is recommended as post-treatment rather than a pretreatment method since the treated effluent by AOPs becomes less biodegradable.