HETEROGENEOUS CO3O4-MGO COMPOSITE CATALYSTS FOR OXIDATIVE DEGRADATION OF ACID ORANGE 7 IN WATER BY SULFATE RADICALS BASED ADVANCED OXIDATION TECHNOLOGY
Vanina V. Ivanova, Stoyanka G. Christoskova, Silviya M. Trankova, Maria K. Stoyanova
Pages: 316-329 Published: 28 May 2015
Views: 2,599 Downloads: 769
Abstract: A series of Co3O4–MgO nanocomposite oxides were prepared by a conventional reverse co-precipitation method and post-calcination and tested as heterogeneous catalysts for activation of Oxone for degradation of azo dye Acid Orange 7 (AO7) in aqueous solution. The as-prepared catalysts demonstrated to be very efficient for heterogeneous decomposition of oxidant producing sulfate radicals for the oxidation of AO7 in solution. Typically, 50 mg/L of AO7 could be completely degraded by the combination of 0.10 g/L of 40% Co3O4–MgO and 0.25 g/L of PMS within 12 min at 20 oC. The composite catalysts exhibited much higher catalytic activity than bare Co3O4 under similar conditions. Hence, it is suggested that the presence of Mg increased the content of surface hydroxyl oxygen, thus favoring the formation of Co(II)–OH complexes, which are vital for heterogeneous activation of Oxone. Kinetic studies confirmed that AO7 degradation catalyzed by Co3O4–MgO catalysts followed the first order kinetics model. The effects of several parameters such as catalyst and oxidant concentration, pH, and solution ionic strength on the AO7 degradation efficiency were assessed. Scavenging effect was examined by using ethanol and tert-butyl alcohol which indicated that sulfate radicals were the dominating reactive species responsible for the degradation process.