Selenite reduction in Boom clay: Effect of FeS₂, clay minerals and dissolved organic matter

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• 作者：Bruggeman ; C. ; Maes ; A. ; Vancluysen ; J. ; Vandemussele ; P.
• 关键词：Selenium ; Boom clay ; Reduction ; Kinetics ; Organic matter ; Pyrite
• 刊名：Environmental Pollution
• 出版年：2005
• 期刊代码：28_02697491
• 类别：env
• 出版时间：September, 2005
• 卷：137
• 期：2
• 页码：209-221
• 文件大小：299 K

摘要

Several experiments were set up to study Se speciation and solubility in the reducing Boom clay environment, starting from oxidized Se species which were added in oversaturation with respect to the thermodynamic solubility of reduced Se solid phases. Upon introduction of SeO₃²⁻ to FeS₂-containing samples, adsorption of SeO₃²⁻ occurred at the FeS₂ surface, and led to a reduction and precipitation of a Se⁰ solid phase with a solubility of 3×10⁻⁹ M (after 60 days). In the presence of humic substances, an association of Se with these humic substances was observed and the 3×10⁻⁹ M solubility limit was not reached in the same time delay. Upon introduction of SeO₃²⁻ to Boom clay suspensions (equilibration up to 9 months), the initial adsorption of SeO₃²⁻ on the solid phase was increased with respect to systems containing only FeS₂, due to the presence of (illite) clay minerals. This competing adsorption process, and the presence of humic substances, again decreased the kinetics of reduction with respect to FeS₂ samples. Also, an association of Se with Boom clay humic substances was observed, and amounted up to 10⁻⁷ M in some samples after 9 months equilibration.