title: Sequestration of chelated copper by structural Fe(II): Reductive decomplexation and transformation of Cu(II)-EDTA.
abstract: Chelated coppers, such as Cu(II)-EDTA, are characteristically refractory and difficult to break down because of their high stability and solubility. Cu(II)-EDTA sequestration by structural Fe(II) (Fe(II)) was investigated intensively in this study. Up to 101.21mgCu(II)/gFe(II) was obtained by Fe(II) in chelated copper sequestration under near neutral pH condition (pH 7.70). The mechanism of Cu(II)-EDTA sequestration by Fe(II) was concluded as follows: 3Cu(II)-EDTA+7Fe(II)+9H2O → Cu(0)↓+ Cu2O↓(the major product)+2Fe2O3·H2O↓+3Fe(II)-EDTA +14H(+) Novel results strongly indicate that Cu(II) reductive transformation induced by surface Fe(II) was mainly responsible for chelated copper sequestration. Cu(0) generation was initially facilitated, and subsequent reduction of Cu(II) into Cu(I) was closely combined with the gradual increase of ORP (Oxidation-Reduction Potential). Cu-containing products were inherently stable, but Cu2O would be reoxidized to Cu(II) with extra-aeration, resulting in the release of copper, which was beneficial to Cu reclamation. Concentration diminution of Cu(II)-EDTA within the electric double layer and competitive adsorption were responsible for the negative effects of Ca(2+), Mg(2+). By generating vivianite, PO4(3-) was found to decrease surface Fe(II) content. This study is among the first ones to identify the indispensible role of reductive decomplexation in chelated copper sequestration. Given the high feasibility and reactivity, Fe(II) may provide a potential alternative in chelated metals pollution controlling.
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, School of Environmental Science & Engineering, Tongji University, Shanghai 200092, PR China.
authors.forename: Hongping
authors.initials: H
authors.lastname: He
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, School of Environmental Science & Engineering, Tongji University, Shanghai 200092, PR China. Electronic address: wudeli@tongji.edu.cn.
authors.forename: Deli
authors.initials: D
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, School of Environmental Science & Engineering, Tongji University, Shanghai 200092, PR China.
authors.forename: Linghui
authors.initials: L
authors.lastname: Zhao
authors.affiliation: School of Civil and Environmental Engineering, Georgia Institute of Technology, GA 30332, United States.
authors.forename: Cong
authors.initials: C
authors.lastname: Luo
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, School of Environmental Science & Engineering, Tongji University, Shanghai 200092, PR China.
authors.forename: Chaomeng
authors.initials: C
authors.lastname: Dai
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, School of Environmental Science & Engineering, Tongji University, Shanghai 200092, PR China.
authors.forename: Yalei
authors.initials: Y
authors.lastname: Zhang
keywords: Chelated copper; Decomplexation; Reduction; Sequestration; Structural Fe(II)