Abstract Wet chemistry and spectroscopic investigations were conducted to study Fe(III) uptake by calcium silicate hydrate (C–S–H) at different Ca/Si ratios. Wet chemistry experiments were carried out by using a 55Fe radiotracer while 29Si NMR and XAS spectroscopy were performed on C–S–H phases loaded with different Fe(III) concentrations. Sorption kinetics experiments indicate that equilibrium was attained within 30 days. Over the studied concentration range, Fe(III) sorption was linear, irrespective of the difference in pH of the suspension and the Ca/Si of C–S–H. In addition, Fe(III) sorption on C–S–H phases was significantly stronger than Al(III) sorption. The total Fe(III) uptake by C–S–H phases, however, was limited by the lower solubility of Fe(OH)3 compared to Al(OH)3; up to 1 mol Fe/kg C–S–H (molar Fe(III)/Si ≈ 0.001) could be taken up. 29Si NMR and EXAFS data suggest Fe(III) uptake in octahedral coordination into the interlayer of the C–S–H phases with Ca/Si ratios 1.2 and 1.5. However, such an uptake mechanism appears unlikely in the case of the C–S–H phase with Ca/Si 0.8 because structural parameters of Fe(III) deduced from EXAFS are different.

中文翻译：

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Fe(III) 被硅酸钙水合物吸收

摘要 进行了湿化学和光谱研究，以研究不同 Ca/Si 比例下硅酸钙水合物 (C-S-H) 对 Fe(III) 的吸收。湿化学实验是使用 55Fe 放射性示踪剂进行的，而 29Si NMR 和 XAS 光谱是在负载不同 Fe(III) 浓度的 C-S-H 相上进行的。吸附动力学实验表明在 30 天内达到平衡。在研究的浓度范围内，Fe(III) 吸附是线性的，与悬浮液的 pH 值和 C-S-H 的 Ca/Si 的差异无关。此外，C-S-H 相上的 Fe(III) 吸附明显强于 Al(III) 吸附。然而，C-S-H 相对 Fe(III) 的总吸收受限于 Fe(OH)3 与 Al(OH)3 相比较低的溶解度；可以吸收高达 1 mol Fe/kg C–S–H（摩尔 Fe(III)/Si ≈ 0.001）。29Si NMR 和 EXAFS 数据表明 Fe(III) 以八面体配位方式吸收到 Ca/Si 比为 1.2 和 1.5 的 C-S-H 相的夹层中。然而，在 Ca/Si 为 0.8 的 C-S-H 相的情况下，这种吸收机制似乎不太可能，因为从 EXAFS 推导出的 Fe(III) 的结构参数不同。