Ozonation catalyzed by iron- and/or manganese-supported granular activated carbons for the treatment of phenol

摘要

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 (TEA) 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 Fe~(2+)-Fe~(3+) and Mn~(2+)-Mn~(3+)-Mn~(4+) redox cycles, resulting in higher catalytic activity. However, the Fe-Mn/GAC surface was shown to undergo galvanic corrosion between Fe_3O_4 and MnO_2, decreasing the catalytic activity. In addition, catalytic ozonation was used to treat secondary petrochemical effluent. The results demonstrated that the Mn/GAC/O_3 system significantly improved the quality of phenol-containing wastewater in terms of its COD, TOC, NH_4~+-N, water color, and ecotoxicity. This study gives a better understanding of the phenol treatment by catalytic ozonation using Fe and/or Mn/GAC.