Selective Degradation of Orange II with the Cobalt(II)–Bicarbonate–Hydrogen Peroxide System

Abstract

A simple and efficient approach to orange II (AOII) degradation using Co2+–HCO3– system as the catalyst and H2O2 as the oxidant under mild reaction conditions was reported. Complete decolorization of 50 μM AOII was observed with 5 μM Co2+ ions and 4 mM H2O2 in 10 mM NaHCO3 aqueous solution after 10 min, which was much faster that that of Fenton reagent with 50 μM Fe2+ ions. Some intermediate products such as carboxylic acids were detected by electrospray ionization-ion trap mass spectrometry and ion chromatography. In the presence of other pollutants such as methylene blue, sulforhodamine B, and a significant amount of anions including Cl–, CO32–, SO42–, NO3–, HPO42–, and CH3COO–, AOII was still rapidly degraded. The results of photoluminescence probing technology, electron spin resonance spin-trapping technology, and radical trap experiments indicated that the tightly associated hydroxyl radicals with the cobalt complex were the reactive species for AOII degradation.