Abstract The uptake of molybdenum, present in aqueous cementitious environments in the form of the molybdate ion (MoO42-), by various cement hydration phases such as calcium-silicate-hydrates (C–S–H), monosulphate (AFm), ettringite (AFt), as well as hardened cement paste made from Ordinary Portland cement (OPC), was studied in batch-type sorption experiments under anoxic conditions. Uptake kinetics were generally fast, leading to sorption equilibrium in less than 30 days. In particular, a strong uptake of molybdate by AFm phases was observed as well as a distinct contribution of C–S–H phases to the molybdate retention in cementitious systems, the latter depending on the Ca/Si-ratio of the C–S–H and the alkali content in solution. In systems containing hydrogarnet, the neo-formation of a molybdate-bearing AFm phase was identified as an additional process contributing to molybdate retention. The findings have implications for selecting grouts for the immobilisation of radioactive waste streams containing Mo-93 and also enhance the data available on molybdate sorption and retention in cementitious systems.

中文翻译：

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钼在水泥体系中的吸收和保留

摘要 以钼酸盐离子 (MoO42-) 形式存在于水性胶结环境中的钼被各种水泥水化相如硅酸钙水合物 (C–S–H)、单硫酸盐 (AFm)、钙矾石 ( AFt)，以及由普通硅酸盐水泥 (OPC) 制成的硬化水泥浆，在缺氧条件下进行分批式吸附实验研究。吸收动力学通常很快，导致在不到 30 天的时间内达到吸附平衡。特别是，观察到 AFm 相对钼酸盐的强烈吸收以及 C–S–H 相对水泥体系中钼酸盐保留的明显贡献，后者取决于 C–S– H 和溶液中的碱含量。在含有水石榴石的系统中，含钼 AFm 相的新形成被确定为有助于保留钼酸盐的附加过程。这些发现对选择用于固定含有 Mo-93 的放射性废物流的灌浆具有重要意义，并且还增强了有关钼酸盐在水泥体系中吸附和保留的可用数据。