The role and fate of EDTA in ultrasound-enhanced zero-valent iron/air system

详细信息    查看全文

• 作者：Tao Zhou ; Teik-Thye Lim ; Yaozhong Li ; Xiaohua Lu ; Fook-Sin Wong
• 关键词：EDTA ; Zero-valent iron ; Ultrasound ; Fenton-like ; Ferryl ; AOPs
• 刊名：Chemosphere
• 出版年：2010
• 出版时间：January 2010
• 年：2010
• 卷：78
• 期：5
• 页码：576-582
• 全文大小：512 K

文摘

In this study, factors such as ZVI loading, ultrasound (US) input power, reaction temperature and solution pH that could affect the EDTA degradation in the US-enhanced zero-valent iron/air (US/ZVI/air) system were investigated. In the system, EDTA also served as an agent for complexation with the dissolved Fe²⁺ and producing H₂O₂ that would trigger Fenton-like reaction and degrade the EDTA itself. US played a threefold role in enhancing the overall EDTA degradation rate through: (1) accelerating ZVI corrosion and production of Fe²⁺; (2) enhancing H₂O₂ production through overcoming the kinetic barrier of oxygen activation by iron-EDTA complex; (3) improving EDTA mineralization while reducing its harmful by-products. The EDTA degradation rate with the US/ZVI/air system was 7.8 times higher than the combined rates achieved with US/air and ZVI/air operated as individual systems, indicating a significant synergistic effect. A hypothetical scheme illustrating the role and fate of EDTA in the US/ZVI/air system is proposed, indicating a complex auto-oxidation process enhanced by the US. It is postulated that ferryl-EDTA complex ([Fe^IVO]EDTA) rather than OH was the dominant oxidant generated in the US/ZVI/air system that oxidized the EDTA even under the circumneutral condition.