CeO2- and MnO2-Loaded Coal Gasification Coarse Slag Catalytic Ozonation for Degradation of Refractory Organics in Coal Chemical Wastewater

Efficient resource utilization of coal gasification coarse slag (CGCS) is critical for ecological sustainability and industrial economics. A low-cost, high-performance catalyst loaded with cerium-manganese oxide (CeO2–MnO2/CGCS) was prepared via an impregnation-hydrothermal synthesis. The catalytic ozonation activity of CeO2–MnO2/CGCS was evaluated based on the removal rate of chemical oxygen demand (COD) for both simulated and actual coal chemical wastewater. For simulated wastewater, the COD removal rates of phenol-, naphthalene-, and benzofuran-containing wastewater were 81.2%, 58.9% and 56.6%, respectively, with the existence of CeO2–MnO2/CGCS, and the COD removal rate of mixed simulated wastewater containing the above compounds reached 66.3%. When CeO2–MnO2/CGCS was applied to actual coal chemical wastewater, the COD decreased from 200 to 36.5 mg/L with a removal rate of 81.7%. In comparison, the COD removal rate using a commercial catalyst was 72.9%, indicating the potential industrial application of CeO2–MnO2/CGCS. Furthermore, it was demonstrated that hydroxyl radicals (·OH) are the key reactive substances in the degradation of organics by adding a free radical scavenger (5,5-dimethyl-1-pyrroline-N-oxide) into the catalytic ozonation degradation of phenol-containing wastewater. Meanwhile, the mechanism of catalytic ozonation degradation of organics in coal chemical wastewater using CeO2–MnO2/CGCS as the catalyst is also proposed.