Iron- and/or manganese-supported catalysts on granular activated carbons (Fe and/or Mn/GACs) were prepared, and their catalytic activities were evaluated by using them to treat phenol and secondary petrochemical effluent via ozonation. The presence of Fe and/or Mn/GACs significantly improved the degradation and degree of phenol mineralization. Changes in dissolved ozone concentrations and the effects of carbonate and tert-butyl alcohol (TBA) indicated that the prepared catalyst enhanced the decomposition of ozone into hydroxyl radicals (·OH), which was determined to be a key factor in catalyzing the ozonation of phenol. Typical intermediate products were identified by GC-MS and HPLC analysis, and a possible degradation pathway of phenol via catalytic ozonation was proposed. The results of XPS, CV, and other experimental data indicated that introducing Fe and/or Mn increased the rate of ozone decomposition into ·OH, and also enhanced the interfacial electron transfer by Fe2+-Fe3+ and Mn2+-Mn3+-Mn4+ redox cycles, resulting in higher catalytic activity. However, the Fe-Mn/GAC surface was shown to undergo galvanic corrosion between Fe3O4 and MnO2, decreasing the catalytic activity. In addition, catalytic ozonation was used to treat secondary petrochemical effluent. The results demonstrated that the Mn/GAC/O3 system significantly improved the quality of phenol-containing wastewater in terms of its COD, TOC, NH4+-N, water color, and ecotoxicity. This study gives a better understanding of the phenol treatment by catalytic ozonation using Fe and/or Mn/GAC.
Keywords: Catalytic ozonation; Galvanic corrosion; Phenol mineralization; Redox cycle; Secondary petrochemical effluent.