Persulfate reactivity enhanced by Fe₂O₃-MnO and CaO-Fe₂O₃-MnO composite: Identification of composite and degradation of CCl₄ at various levels of pH

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• 作者：Si-Hyun Do ; Yong-Jae Kwon ; Su-Jin Bang ; Sung-Ho Kong ; ^{shkong@hanyang.ac.kr}
• 关键词：Persulfate activation ; Fe2O3&ndash ; MnO composite ; CaO&ndash ; Fe2O3&ndash ; MnO composite ; Maghemite ; Superoxide anion ; pH
• 刊名：Chemical Engineering Journal
• 出版年：2013
• 出版时间：1 April, 2013
• 年：2013
• 卷：221
• 期：Complete
• 页码：72-80
• 全文大小：648 K

文摘

The reactivity of persulfate (PS) was investigated when novel synthesized composites were used as activators. First, two types of composites were prepared by the mixing of an FeSO₄ solution into a MnO-suspended solution with the addition of either NaOH (i.e. Composite I) or Ca(OH)₂ (i.e. Composite II). SEM?EDS indicated that Fe and Mn were detected on Composite I while Fe and Ca were detected on Composite II. XPS analyses indicated that the crystalline form on the surface of Composite I was identified as maghemite (¦Ã-Fe₂O₃), not jacobsite (MnFe₂O₄). On the other hand, the surface of Composite II was predominantly covered by lime (CaO) and maghemite. Based on these results, Composite I and Composite II were represented as Fe₂O₃-MnO and CaO-Fe₂O₃-MnO, respectively. BET surface area of MnO, Fe₂O₃-MnO, and CaO-Fe₂O₃-MnO were 0.4, 56, and 102 m² g^?1, and PZC of them were measured as 7.1, 8.2, and 12.2, respectively. The greater BET surface area and the higher PZC was due to CaO. Investigating the role of the composite as activator, PS/composite systems at various pH levels (i.e. 3, 7, 9 and 12) were applied for degradation of carbon tetrachloride (CT). The PS/Fe₂O₃-MnO system degraded CT effectively at pH 7 and 9, while PS/CaO-Fe₂O₃-MnO system showed effective degradation at pH 9 and 12. The optimum pH conditions in each PS/composite system implied that PS activation to produce reductant was possibly related to the surface charge of the composite. A mechanism to produce reductant, superoxide anion, from the PS/composite system was limitedly proposed.