Fractionation of Selenium during Selenate Reduction by Granular Zerovalent Iron

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• 作者：Heather K. Shrimpton ; David W. Blowes ; Carol J. Ptacek
• 刊名：Environmental Science & Technology
• 出版年：2015
• 出版时间：October 6, 2015
• 年：2015
• 卷：49
• 期：19
• 页码：11688-11696
• 全文大小：474K
• ISSN：1520-5851

文摘

Batch experiments were conducted using granular zerovalent iron (G-ZVI) with either ultrapure water or CaCO₃ saturated simulated groundwater to assess the extent of Se isotope fractionation in solution under the anaerobic conditions characteristic of many aquifers. G-ZVI is a common remediation material in permeable reactive barriers (PRB) to treat Se-contaminated groundwater, and stable isotopes are a potential tool for assessing removal mechanisms. The solution composition, speciation of Se, and Se isotope ratios were determined during both sets of experiments. Dissolved Se concentrations decreased from 10 to <2 mg L^鈥? after 3 d in the CaCO₃ system and below 0.4 mg L^鈥? after 2 d in the ultrapure water system. XANES analysis of the solid phase showed spectra consistent with the formation of Se(IV), Fe₂(SeO₃)₃, FeSe, FeSe₂, and Se(0) on the G-ZVI. Selenium isotope ratio measurements in solution in the CaCO₃ and ultrapure water experiments showed enrichment of 未^82/76Se values from 鈭?.94 卤 0.07鈥?and 鈭?.93 卤 0.20鈥?to maximum values of 6.85 卤 0.52鈥?and 5.68 卤 0.20鈥?over 72 and 36 h, respectively. The effective fractionations associated with the reduction of Se(VI) were 4.3鈥?within the CaCO₃ saturated water and 3.0鈥?in ultrapure water.