Degradation of Orange II in ferrous activated peroxymonosulfate system: Efficiency, situ EPR spin trapping and degradation pathway study
The degradation of Orange II (Org II) by ferrous activated peroxymonosulfate (PMS) was inspected. The maximum degradation efficiency of 62.3% in 90 min occurred at 0.286 mM [PMS] 0 , corresponding to 1:1 molar ratio of Fe 2+ : PMS. Results show that poor recovery of Fe 2+ accounts for poor degradation in the slow stage. The species of reactive radicals were determined through indirect way by quenching agents, as well as directly by in situ EPR spin trapping tests. Results indicated that hydroxyl radicals instead of sulfate radicals were responsible for Org II degradation. The removal of Org II degradation would increase to 93.3% in 90 min as reaction temperature increased to 60 °C. The activation energy for PMS and Fe 2+ /PMS alone was calculated to be 77.2 kJ/mol and 34.7 kJ/mol, respectively. The removal efficiency of total organic carbon (TOC) was 11.0% and 43.8% when [Fe 2+ ] 0 :[PMS] 0 :[Org II] 0 was 5:5:1 and 34:34:1, respectively. The main degradation products of Org II in system were supposed to be heterocyclic compounds containing a five-atom ring. Results demonstrated that Fe 2+ /PMS technology is promising technology for water pollution.
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