Laboratory for Waste Management, Paul Scherrer Institute, Villigen PSI, Switzerland.
Laboratory for Waste Management, Paul Scherrer Institute, Villigen PSI, Switzerland.
Chemosphere. 2020 Jul;250:126230. doi: 10.1016/j.chemosphere.2020.126230. Epub 2020 Feb 20.
The Swiss disposal concept foresees that carbon-14 (C) is predominantly released from irradiated steel disposed of in a cement-based repository for low- and intermediate-level radioactive waste. To predict how C migrates in the cementitious environment of the repository near field and subsequently in the host rock, knowledge about the carbon speciation during anoxic steel corrosion in alkaline conditions is therefore essential. To this end, batch-type corrosion experiments with carbon-containing zero-valent iron (ZVI) powders subject to oxidative pre-treatments were carried out in NaOH solution at pH 11 and 12.5. Alkanes and alkenes (C-C) were identified in the gas phase and produced on the iron surface by a Fischer-Tropsch type mechanism. The kind of oxidative pre-treatment has an effect on the production rate of hydrocarbons (HCs). In the liquid phase, carboxylic acids were identified and produced during the oxidative pre-treatment of the ZVI powders. They are released instantaneously from the oxide layer upon contact with the alkaline solution. The kind of oxidative treatment and the exposure time to oxic conditions directly influence the amount of carboxylic acids accommodated in the oxide layer.
瑞士的处置概念预计碳-14（C）主要是从低放和中放废物水泥基处置库中处置的辐照钢中释放出来的。为了预测 C 在近场处置库的水泥质环境中的迁移情况，以及随后在宿主岩石中的迁移情况，因此必须了解在缺氧条件下碱性条件下钢腐蚀过程中的碳形态。为此，在 pH 值为 11 和 12.5 的 NaOH 溶液中，进行了含碳零价铁（ZVI）粉末的分批式腐蚀实验，并进行了氧化预处理。烷烃和烯烃（C-C）在气相中被鉴定出来，并通过费托型机制在铁表面上生成。氧化预处理的种类对碳氢化合物（HCs）的生成速率有影响。在液相中，羧酸被鉴定出来，并在 ZVI 粉末的氧化预处理过程中生成。它们在与碱性溶液接触时立即从氧化物层中释放出来。氧化处理的种类和暴露于含氧条件下的时间直接影响氧化物层中容纳的羧酸的量。
