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摘要
Polysulfide has drawn much attention in recent years for remediation of Cr(Ⅵ)-contaminated soil and groundwater systems, due to its stability and persistent reduction ability. The kinetics (order of reaction, reaction rate constant) of the redox reaction between polysulfide and Cr(Ⅵ) were studied. The impact of representative soil minerals (montmorillonite, kaolin, SiO2, Al2O3 and TiO2), humic acid and dissolved oxygen on the reaction kinetics was also investigated. Experimental results showed that, under the anaerobic condition, the rate of this redox reaction can be expressed as r =-d[Cr(Ⅵ)]/dt=kobs [Cr(Ⅵ)]1.1[Sx 2-]0.8[H+]1.3, with the apparent kinetic constant kobs being (3.6±3.5)×1021L2.2?(mol2.2?min)-1. Further experiments indicated that, at 25℃ and pH 9.5, the tested minerals did not show significant impact on the reaction kinetics, while humic acid and dissolved oxygen were found to inhibit the rate of chromate reduction by polysulfide.
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