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Competitive TcO4–, IO3–, and CrO42– Incorporation into Ettringite
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2020-12-28 , DOI: 10.1021/acs.est.0c06707 Elizabeth C. Gillispie 1 , Sebastian T. Mergelsberg 2 , Tamas Varga 3 , Samuel M. Webb 4 , Nancy M. Avalos 1 , Michelle M. V. Snyder 1 , Agathe Bourchy 1 , R. Matthew Asmussen 1 , Sarah A. Saslow 1
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2020-12-28 , DOI: 10.1021/acs.est.0c06707 Elizabeth C. Gillispie 1 , Sebastian T. Mergelsberg 2 , Tamas Varga 3 , Samuel M. Webb 4 , Nancy M. Avalos 1 , Michelle M. V. Snyder 1 , Agathe Bourchy 1 , R. Matthew Asmussen 1 , Sarah A. Saslow 1
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Ettringite is a naturally occurring mineral found in cementitious matrices that is known for its ability to incorporate environmentally mobile oxyanion contaminants. To better assess this immobilization mechanism for contaminants within cementitious waste forms intended for nuclear waste storage, this work explores how mixed oxyanion contaminants compete for ettringite incorporation and influence the evolving mineralogy. Ettringite was precipitated in the presence of TcO4–, IO3–, and/or CrO42–, known contaminants of concern to nuclear waste treatment, over pre-determined precipitation periods. Solution analyses quantified contaminant removal, and the collected solid was characterized using bulk and microprobe X-ray diffraction coupled with pair distribution function and microprobe X-ray fluorescence analyses. Results suggest that ≥96% IO3– is removed from solution, regardless of ettringite precipitation time or the presence of TcO4– or CrO42–. However, TcO4– removal remained <20%, was not significantly improved with longer ettringite precipitation times, and decreased to zero in the presence of IO3–. When IO3– is co-mingled with CrO42–, calcite and gypsum are formed as secondary mineral phases, which allows for oxyanion partitioning, e.g., IO3– incorporation into ettringite, and CrO42– incorporation into calcite. Results from this work exemplify the importance of competitive immobilization when assessing waste form performance and environmental risk of contaminant release.
中文翻译：
竞争性TcO 4 –，IO 3 –和CrO 4 2–掺入钙矾石
钙矾石是在水泥基体中发现的天然矿物，以其掺入环境可移动的氧阴离子污染物的能力而闻名。为了更好地评估用于核废料储存的水泥废料形式中污染物的固定化机制，这项工作探索了混合的含氧阴离子污染物如何竞争钙矾石的掺入并影响不断发展的矿物学。在TcO 4 –，IO 3 –和/或CrO 4 2–的存在下，钙矾石沉淀。在预定的降水期内，是核废料处理关注的已知污染物。溶液分析可定量去除污染物，并使用体积和微探针X射线衍射以及对分布函数和微探针X射线荧光分析对收集的固体进行表征。结果表明，无论钙矾石沉淀时间或TcO 4 –或CrO 4 2 –的存在，从溶液中去除的IO 3 - ≥96％。然而，TCO 4 -去除保持<20％，未显著较长钙矾石沉淀倍改善，并且在IO的存在减少到零3 - 。当IO 3–与CrO 4 2–混合在一起，形成方解石和石膏作为次生矿物相，从而允许氧阴离子分配，例如IO 3 –掺入钙矾石中，而CrO 4 2–掺入方解石中。这项工作的结果证明，在评估废物的性能和污染物释放的环境风险时，固定竞争的重要性。
更新日期：2021-01-19
中文翻译：
竞争性TcO 4 –，IO 3 –和CrO 4 2–掺入钙矾石
钙矾石是在水泥基体中发现的天然矿物，以其掺入环境可移动的氧阴离子污染物的能力而闻名。为了更好地评估用于核废料储存的水泥废料形式中污染物的固定化机制，这项工作探索了混合的含氧阴离子污染物如何竞争钙矾石的掺入并影响不断发展的矿物学。在TcO 4 –，IO 3 –和/或CrO 4 2–的存在下，钙矾石沉淀。在预定的降水期内，是核废料处理关注的已知污染物。溶液分析可定量去除污染物，并使用体积和微探针X射线衍射以及对分布函数和微探针X射线荧光分析对收集的固体进行表征。结果表明，无论钙矾石沉淀时间或TcO 4 –或CrO 4 2 –的存在，从溶液中去除的IO 3 - ≥96％。然而，TCO 4 -去除保持<20％，未显著较长钙矾石沉淀倍改善，并且在IO的存在减少到零3 - 。当IO 3–与CrO 4 2–混合在一起，形成方解石和石膏作为次生矿物相，从而允许氧阴离子分配，例如IO 3 –掺入钙矾石中，而CrO 4 2–掺入方解石中。这项工作的结果证明，在评估废物的性能和污染物释放的环境风险时，固定竞争的重要性。
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