Degradation efficiencies of azo dye Acid Orange 7 by the interaction of heat, UV and anions with common oxidants: Persulfate, peroxymonosulfate and hydrogen peroxide

Abstract

In this paper, the degradation of azo dye Acid Orange 7 (AO7) by three common peroxides (persulfate (PS), peroxymonosulfate (PMS) or hydrogen peroxide (H 2O 2)) under various activation conditions, i.e., heat (25–80 °C), UV light (254 nm), or anions (SO 4 2−, NO 3 −, CO 3 2−, HCO 3 −, HPO 4 2−, and Cl −), was investigated. The order of AO7 degradation efficiencies by heat activation is PS ≫ PMS > H 2O 2. PS oxidation activated by heat (>50 °C) is an effective degradation technology, while PMS and H 2O 2 are hardly activated. When assisted by UV, peroxides could all be activated and degrade AO7 quickly. The order is PS > H 2O 2 > PMS. We activated peroxides, for the first time, by using some anions and compared the subsequently degradation efficiencies of AO7. It was found that PMS could be activated by some anions, but PS and H 2O 2 cannot. The activation efficiencies of PMS by SO 4 2− and NO 3 − are negligible, whereas remarkable by HCO 3 −, HPO 4 2−, Cl − and CO 3 2−. For HCO 3 −, HPO 4 2− and Cl −, the activation efficiencies become higher with the increase of anion concentration. For CO 3 2−, however, the activation efficiency is higher at lower concentration.