Refractory organic compounds in coal chemical wastewater treatment by catalytic ozonation using Mn-Cu-Ce/Al₂O₃

A composite Mn-Cu-Ce tri-metal oxide supported on γ-Al₂O₃ (Mn-Cu-Ce/Al₂O₃) catalyst was prepared by an impregnation-calcination method and investigated in the catalytic ozonation treatment of real coal chemical wastewater (CCW). The catalyst was characterized by XRD, SEM, TEM, XRF, BET, and XPS techniques. The results showed that Mn, Cu, and Ce metal oxides were evenly distributed on the Al₂O₃ surface and the catalyst maintained a large surface area and a high pore volume compared with the pristine Al₂O₃. The synergy between Mn, Cu, and Ce oxides greatly enriched the catalytic active sites and enhanced the ozonation performance. The catalytic ozonation process with Mn-Cu-Ce/Al₂O₃ increased the removal rate of total organic carbon (TOC) by 31.6% compared with ozonation alone. The ketones, aromatic compounds, phenols, and nitrogen-containing heterocyclic compounds in CCW have been effectively degraded and mineralized by Mn-Cu-Ce/Al₂O₃ catalytic ozonation process, and its biodegradability has also been significantly improved. The experimental results of ∙OH scavengers revealed that the mechanism of Mn-Cu-Ce/Al₂O₃ catalytic ozonation was to promote the generation of ∙OH radicals. The catalytic activity of Mn-Cu-Ce/Al₂O₃ was only a slight decrease in six consecutive catalytic ozonation treatments, showing good stability. Therefore, Mn-Cu-Ce/Al₂O₃ can be used as a candidate catalyst for the advanced treatment of refractory organic wastewaters upon catalytic ozonation.