title: Decolorization of azo dye by peroxymonosulfate activated by carbon nanotube: Radical versus non-radical mechanism.
abstract: Carbon nanotube (CNT) has been shown to effectively activate peroxymonosulfate (PMS) to remove contaminants, whereas controversial activation mechanisms (radical vs non-radical mechanism) were previously proposed. Here we report that radical-induced decolorization of acid orange 7 (AO7) dominated in the CNT activated PMS system, but non-radical mechanism was also involved at high Cl-concentration. CNT exhibited high activity in activating PMS to decolorize AO7. The decolorization rate of AO7 increased with increasing PMS dosages and CNT loadings, rising temperature and higher pH. Radical quenching and photoluminescence techniques confirmed the decolorization of AO7 in the CNT/PMS system was caused by the radical oxidation, which dominantly took place on the surface of CNT, rather than the bulk solution. The presence of Cl-exhibited a dual effect on AO7 decolorization. Low concentration of Cl-slightly inhibited AO7 decolorization, but further raising the concentration to above 0.1M significantly accelerated its decolorizaition. Cl-was confirmed to react with PMS to generate HClO, which effectively bleached AO7 through non-radical process rather than radical process. The decolorization of AO7 induced from the non-radical process exhibited different degradation products and less mineralization in comparison to that derived from radical process.
authors: School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215001, PR China.
authors: Jiabin
authors: J
authors: Chen
authors: School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215001, PR China.
authors: Liming
authors: L
authors: Zhang
authors: School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215001, PR China. Electronic address: huangtianyin111@163.com.
authors: Tianyin
authors: T
authors: Huang
authors: School of Chemistry and Materials Science, University of Science and Technology of China, Hefei 230026, PR China.
authors: Wenwei
authors: W
authors: Li
authors: School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215001, PR China.
authors: Ying
authors: Y
authors: Wang
authors: School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215001, PR China.
authors: Zhongming
authors: Z
authors: Wang
keywords: Azo dye; Carbon nanotube; Chloride; Mechanism; Peroxymonosulfate