Catalytic ozonation of quinoline using nano-MgO: Efficacy, pathways, mechanisms and its application to real biologically pretreated coal gasification wastewater

- Nano-MgO was successfully prepared by homogeneous precipitation method.
- Nano-MgO exhibited high catalytic activity for quinoline removal in ozonation process.
- Nine intermediates were identified and the degradation pathway was proposed.
- Nano-MgO can facilitate ozone decomposition and act via a hydroxyl radical mechanism.
- Catalytic ozonation pretreatment improved the biodegradability of biologically pretreated coal gasification wastewater.

Nano-MgO was prepared by homogeneous precipitation method and applied for the degradation of quinoline. The characterization of the catalyst was determined by X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), Transmission Electron Microscope (TEM) and Energy Dispersive Spectrometer (EDS). The results showed that the presence of nano-MgO significantly improved the degradation and mineralization of quinoline. Nine intermediates were identified by liquid chromatograph-tandem mass spectrometer (LC-MS/MS), gas chromatograph and mass spectrometry (GC-MS) and ion chromatograph (IC) analysis. And a possible degradation pathway of quinoline in catalytic ozonation was proposed. The change of dissolved ozone concentration and the effect of tert butyl alcohol (TBA) and phosphate indicated that the prepared catalyst could enhance ozone decomposition into hydroxyl radicals, which was considered to be mainly responsible for the pollutants removal. In addition, catalytic ozonation pretreatment was applied for the treatment of biologically pretreated coal gasification wastewater. The results demonstrated that catalytic ozonation pre-treatment improved the biodegradability of wastewater containing quinoline in terms of BOD5/COD (B/C), toxicity and resazurin dehydrogenase activity (DHA), indicating the potential of catalytic ozonation integrated with biosystem for this type of wastewater. This study would assist in obtaining a better understanding of the application of catalytic ozonation pre-treatment in biologically pretreated coal gasification wastewater.

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