Elsevier

Pedosphere

Volume 17, Issue 3, June 2007, Pages 318-323
Pedosphere

Catalysis of Manganese(II) on Chromium(VI) Reduction by Citrate1

https://doi.org/10.1016/S1002-0160(07)60038-1Get rights and content

Abstract

The catalysis of manganese(II) (Mn2+) on chromium(VI) (Cr6+) reduction by citrate was studied through batch experiments with the concentration of citrate greatly in excess of Cr6+ at 25°C and in pH ranges of 4.0 to 5.0. Results showed that at pH 4.5 within 22 h direct reduction of Cr6+ by citrate was not observed, but for the same time when Mn2+ (50 to 200 μmol L−1) was added, nearly all Cr6+ was reduced, with the higher initial Mn2+ concentration having faster Cr6+ reduction. In the initial stage of the reaction, the Cr6+ reduction could be described with a pseudo-first-order kinetics equation. In the later stage of the reaction, plots of Inc(Cr6+) versus t, where c(Cr6+) is the Cr6+ concentration in the reaction and t is the reaction time, deviated from the initial linear trend. The deviations suggested that the pseudo-first-order kinetics did not apply to the whole experimental period and that some reaction intermediates could have greatly accelerated Cr6+ reduction by citrate. The catalysis of the intermediates increased with the reaction time and gradually reached stability. Then, the plot of Inc(Cr6+) versus t in the presence of Mn2+ was linear again, with the rate constant increasing by 102 times compared with the absence of Mn2+. Complexation between Mn2+ and citrate was likely a prerequisite for the catalysis of Mn2+ on the reaction. Additional experiments showed that introducing ethylenediaminetetraacetic acid (EDTA) into the reaction system strongly suppressed the catalysis of Mn2+.

References (27)

  • B. Deng et al.

    Surface-catalyzed chromium(VI) reduction: Reactivity comparisons of different organic reductants and different oxide surfaces

    Environ. Sci. Technol

    (1996)
  • L.E. Eary et al.

    Chromate removal from aqueous wastes by reduction with ferrous ion

    Environ. Sci. Technol

    (1988)
  • L.E. Eary et al.

    Kinetics of chromate reduction by ferrous ions derived from hematite and biotite at 25°C

    Am. J. Sci

    (1989)
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    Project supported by the National Natural Science Foundation of China (No. 40671089).

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