Reductive Sequestration of Pertechnetate (99TcO4鈥?/sup>) by Nano Zerovalent Iron (nZVI) Transformed by Abiotic Sulfide
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- 作者：Dimin Fan ; Roberto P. Anitori ; Bradley M. Tebo ; Paul G. Tratnyek ; Juan S. Lezama Pacheco ; Ravi K. Kukkadapu ; Mark H. Engelhard ; Mark E. Bowden ; Libor Kovarik ; Bruce W. Arey
- 刊名：Environmental Science & Technology (ES&T)
- 出版年：2013
- 出版时间：May 21, 2013
- 年：2013
- 卷：47
- 期：10
- 页码：5302-5310
- 全文大小：520K
- 年卷期：v.47,no.10(May 21, 2013)
- ISSN：1520-5851
文摘
Under anoxic conditions, soluble pertechnetate (99TcO4鈥?/sup>) can be reduced to less soluble TcO2路nH2O, but the oxide is highly susceptible to reoxidation. Here we investigate an alternative strategy for remediation of Tc-contaminated groundwater whereby sequestration as Tc sulfide is favored by sulfidic conditions stimulated by nano zerovalent iron (nZVI). nZVI was pre-exposed to increasing concentrations of sulfide in simulated Hanford groundwater for 24 h to mimic the onset of aquifer biotic sulfate reduction. Solid-phase characterizations of the sulfidated nZVI confirmed the formation of nanocrystalline FeS phases, but higher S/Fe ratios (>0.112) did not result in the formation of significantly more FeS. The kinetics of Tc sequestration by these materials showed faster Tc removal rates with increasing S/Fe between 0 and 0.056, but decreasing Tc removal rates with S/Fe > 0.224. The more favorable Tc removal kinetics at low S/Fe could be due to a higher affinity of TcO4鈥?/sup> for FeS than iron oxides, and electron microscopy confirmed that the majority of the Tc was associated with FeS phases. The inhibition of Tc removal at high S/Fe appears to have been caused by excess HS鈥?/sup>. X-ray absorption spectroscopy revealed that as S/Fe increased, the pathway for Tc(IV) formation shifted from TcO2路nH2O to Tc sulfide phases. The most substantial change of Tc speciation occurred at low S/Fe, coinciding with the rapid increase in Tc removal rate. This agreement further confirms the importance of FeS in Tc sequestration.
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