title: The role and fate of EDTA in ultrasound-enhanced zero-valent iron/air system.
abstract: 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 Fe(2+) and producing H(2)O(2) 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 Fe(2+); (2) enhancing H(2)O(2) 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(IV)O]EDTA) rather than OH was the dominant oxidant generated in the US/ZVI/air system that oxidized the EDTA even under the circumneutral condition.
authors: Nanyang Technological University, Singapore, Republic of Singapore. tzhou@ntu.edu.sg
authors: Tao
authors: T
authors: Zhou
authors: Teik-Thye
authors: TT
authors: Lim
authors: Yaozhong
authors: Y
authors: Li
authors: Xiaohua
authors: X
authors: Lu
authors: Fook-Sin
authors: FS
authors: Wong
mesh_terms: D000388:Air; D004492:Edetic Acid / Q000378:metabolism*; D004785:Environmental Pollutants / Q000378:metabolism*; D052918:Environmental Restoration and Remediation; D006861:Hydrogen Peroxide / Q000737:chemistry / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D013696:Temperature; D014465:Ultrasonics
chemical_list: D004785:Environmental Pollutants; C045076:Fenton's reagent; D004492:Edetic Acid; D006861:Hydrogen Peroxide; D007501:Iron