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Influence of complex reagents on removal of chromium(VI) by zero-valent iron.
Chemosphere. 2008 Jun; 72(6):870-4.C

Abstract

The removal of Cr(VI) by zero-valent iron (Fe(0)) and the effect of three complex reagents, ethylenediaminetetraacetic acid (EDTA), NaF and 1,10-phenanthroline, on this reaction were investigated using batch reactors at pH values of 4, 5 and 6. The results indicate that the removal of Cr(VI) by Fe(0) is slow at pH 5.0 and that three complex reagents play different roles in the reaction. EDTA and NaF significantly enhance the reaction rate. The zero-order rate constants at pH 5.0 were 5.44 microM min(-1) in the presence of 4mM EDTA and 0.99 micrM min(-1) in the presence of 8 mM NaF, respectively, whereas that of control was only 0.33 micrM min(-1), even at pH=4.0. This enhancement is attributed to the formation of complex compounds between EDTA/NaF and reaction products, such as Cr(III) and Fe(III), which eliminate the precipitates of Cr(III), Fe(III) hydroxides and Cr(x)Fe(1-)(x)(OH)(3) and thus reduce surface passivation of Fe(0). In contrast, 1,10-phenanthroline, a complex reagent for Fe(II), dramatically decreases Cr(VI) reduction by Fe(0). At pH=4.0, the zero-order rate constant in the presence of 1mM of 1,10-phenanthroline was 0.02 micrM min(-1), decreasing by 99.7% and 93.9%, respectively, compared with the results in the presence and absence of EDTA. The results suggest that a pathway of the reduction of Cr(VI) to Cr(III) by Fe(0) may involve dissolution of Fe(0) to produce Fe(II), followed by reduction of Cr(VI) by Fe(II), rather than the direct reaction between Cr(VI) and Fe(0), in which Fe(0) transfers electrons to Cr(VI).

Authors+Show Affiliations

College of Sciences, Nanjing Agricultural University, Nanjing 210095, PR China.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

18486963

Citation

Zhou, H, et al. "Influence of Complex Reagents On Removal of chromium(VI) By Zero-valent Iron." Chemosphere, vol. 72, no. 6, 2008, pp. 870-4.
Zhou H, He Y, Lan Y, et al. Influence of complex reagents on removal of chromium(VI) by zero-valent iron. Chemosphere. 2008;72(6):870-4.
Zhou, H., He, Y., Lan, Y., Mao, J., & Chen, S. (2008). Influence of complex reagents on removal of chromium(VI) by zero-valent iron. Chemosphere, 72(6), 870-4. https://doi.org/10.1016/j.chemosphere.2008.04.010
Zhou H, et al. Influence of Complex Reagents On Removal of chromium(VI) By Zero-valent Iron. Chemosphere. 2008;72(6):870-4. PubMed PMID: 18486963.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Influence of complex reagents on removal of chromium(VI) by zero-valent iron. AU - Zhou,H, AU - He,Y, AU - Lan,Y, AU - Mao,J, AU - Chen,S, Y1 - 2008/05/19/ PY - 2007/10/08/received PY - 2008/04/01/revised PY - 2008/04/02/accepted PY - 2008/5/20/pubmed PY - 2008/8/30/medline PY - 2008/5/20/entrez SP - 870 EP - 4 JF - Chemosphere JO - Chemosphere VL - 72 IS - 6 N2 - The removal of Cr(VI) by zero-valent iron (Fe(0)) and the effect of three complex reagents, ethylenediaminetetraacetic acid (EDTA), NaF and 1,10-phenanthroline, on this reaction were investigated using batch reactors at pH values of 4, 5 and 6. The results indicate that the removal of Cr(VI) by Fe(0) is slow at pH 5.0 and that three complex reagents play different roles in the reaction. EDTA and NaF significantly enhance the reaction rate. The zero-order rate constants at pH 5.0 were 5.44 microM min(-1) in the presence of 4mM EDTA and 0.99 micrM min(-1) in the presence of 8 mM NaF, respectively, whereas that of control was only 0.33 micrM min(-1), even at pH=4.0. This enhancement is attributed to the formation of complex compounds between EDTA/NaF and reaction products, such as Cr(III) and Fe(III), which eliminate the precipitates of Cr(III), Fe(III) hydroxides and Cr(x)Fe(1-)(x)(OH)(3) and thus reduce surface passivation of Fe(0). In contrast, 1,10-phenanthroline, a complex reagent for Fe(II), dramatically decreases Cr(VI) reduction by Fe(0). At pH=4.0, the zero-order rate constant in the presence of 1mM of 1,10-phenanthroline was 0.02 micrM min(-1), decreasing by 99.7% and 93.9%, respectively, compared with the results in the presence and absence of EDTA. The results suggest that a pathway of the reduction of Cr(VI) to Cr(III) by Fe(0) may involve dissolution of Fe(0) to produce Fe(II), followed by reduction of Cr(VI) by Fe(II), rather than the direct reaction between Cr(VI) and Fe(0), in which Fe(0) transfers electrons to Cr(VI). SN - 0045-6535 UR - https://www.unboundmedicine.com/medline/citation/18486963/Influence_of_complex_reagents_on_removal_of_chromium_VI__by_zero_valent_iron_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0045-6535(08)00471-2 DB - PRIME DP - Unbound Medicine ER -