Decrease in the organic content of refinery wastewater by photocatalytic Fenton oxidation using iron-doped zeolite: Catalyst preparation, characterization, and performance

Abstract

A Fe-exchanged zeolite photocatalyst was synthesized by applying an ion exchange method and used to examine the degradation of effluent from the petroleum industry. The exchanged zeolite catalyst was characterized by X-ray diffraction, X-ray fluorescence, Fourier-transform infrared spectroscopy, Naioatomic force microscopy, Brunauer-Emmett-Teller surface area, and Filed Emission Scanning Electron Microscopy-Energy Dispersive X-ray Spectrometer. Characterization of the catalyst confirmed its composition and phase but also showed a decrease in uniformity and crystallinity. The photocatalyst was tested under ultra-violet lamp irradiation for the removal of pollutants in wastewater from Iraqi petroleum refineries. Experiments were performed using a stirred batch reactor with an initial chemical oxygen demand of 492 mg/L. The exchanged zeolite was used as a catalyst and H2O2 was used as an oxidant. For synthetic wastewater, 99.84 % of organic pollutants were removed in 120 min. Chemical oxygen demand removal values were almost the same (85.29 and 81.67 %, respectively) for real wastewater obtained from the Dora Refinery and North Gas Company. Furthermore, the exchanged zeolite displayed excellent stability and low release of iron ions from the catalyst during the reaction (less than 11 mg/L). The catalyst was recycled five times with power consumption ranging from 691.18 to 826.96 kWh/kg COD.