Oxidation of Metal-EDTA Complexes by TiO2 Photocatalysis
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- 作者：Thomas H. Madden ; Abhaya K. Datye ; Melissa Fulton ; Michael R. Prairie ; Sabir A. Majumdar ; and Bertha M. Stange
- 刊名：Environmental Science & Technology
- 出版年：1997
- 出版时间：December 1997
- 年：1997
- 卷：31
- 期：12
- 页码：3475 - 3481
- 全文大小：179K
- 年卷期：v.31,no.12(December 1997)
- ISSN：1520-5851
文摘
Ethylenediaminetetraacetic acid (EDTA), a common industrialagent for complexing metal ions in water, frequentlyinhibitsconventional metals-removal technologies used in watertreatment. This study investigated the use of TiO2photocatalysis for the aqueous-phase oxidation of EDTA andseveral metal complexes of EDTA. Reactions wereperformedat 0.1 wt % loading of Degussa P-25 TiO2, asoluteconcentration of 0.8 mM and at a constant pH. Thedifferentmetal-EDTA complexes exhibited widely different photocatalytic oxidation rates under equivalent conditions of pH= 4 ± 0.1 in an aerobic system: Cu(II)-EDTA >Pb(II)-EDTA >> EDTA > Ni(II)-EDTA 
Cd(II)-EDTA Zn(II)-EDTA >>> Cr(III)-EDTA. Photoefficiency based ontheCu(II)-EDTA initial rate is nearly 60%. The rates oftotalorganic carbon (TOC) removal and formaldehyde generationduring photocatalytic EDTA oxidation indicate similaritiestoelectrochemical oxidations of EDTA. Several meanswereexplored to enhance the oxidation of Ni(II)-EDTA,whosebehavior was taken to represent that of the slowlyoxidizingcomplexes. Continuous addition of H2O2solution during thephotocatalytic treatment increased the oxidation rate forNi(II)-EDTA as did the presence of homogeneousCu2+.The presence of Cu2+ led to rapid ligand exchangetransformingthe Ni(II)-EDTA into Cu(II)-EDTA, which is easilyoxidized.
Cd(II)-EDTA Zn(II)-EDTA >>> Cr(III)-EDTA. Photoefficiency based ontheCu(II)-EDTA initial rate is nearly 60%. The rates oftotalorganic carbon (TOC) removal and formaldehyde generationduring photocatalytic EDTA oxidation indicate similaritiestoelectrochemical oxidations of EDTA. Several meanswereexplored to enhance the oxidation of Ni(II)-EDTA,whosebehavior was taken to represent that of the slowlyoxidizingcomplexes. Continuous addition of H2O2solution during thephotocatalytic treatment increased the oxidation rate forNi(II)-EDTA as did the presence of homogeneousCu2+.The presence of Cu2+ led to rapid ligand exchangetransformingthe Ni(II)-EDTA into Cu(II)-EDTA, which is easilyoxidized.