Asymmetric hydration structure around calcium ion restricted in micropores fabricated in activated carbons
Asymmetric hydration structure around calcium ion restricted in micropores fabricated in activated carbons
复制标题
限制在活性炭微孔中的钙离子周围的不对称水合结构
DOI：
10.1088/0953-8984/28/46/464003
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Yasushige Kuroda
中科院分区：
文献类型：
--
作者：
Takahiro Ohkubo;Tomoko Kusudo;Yasushige Kuroda
采用吸附等温线和Ca K边X射线吸收精细结构（XAFS）谱研究了Ca（NO3）2水溶液在不同平均孔径（0.6 3和1.1nm）活性炭微孔中的吸附相和水合结构.窄孔活性炭的单位体积吸附Ca2+的密度高于宽孔活性炭，而窄孔活性炭的单位质量吸附量是大孔活性炭的一半。另一方面，XAFS谱中双电子（KM I）和1s→ 3d激发带的变化表明，微孔中Ca2+的结构参数与本体水溶液的结构参数基本一致，但微孔中Ca2+周围的水化团簇发生了畸变.与单价离子如Rb+的水合结构相反，其通常在AC中小于1 nm的微孔中呈现脱水结构，本研究清楚地解释了实验揭示的限制在1 nm左右的碳微孔中的水化Ca2+的非球对称结构，其中任何从Ca2+周围的第一水化壳层的脱水现象无法观察到。
The adsorbed phase and hydration structure of an aqueous solution of Ca (NO 3) 2 restricted in micropores fabricated in activated carbons (ACs) having different average pore widths (0.63 and 1.1 nm) were investigated with the analysis of adsorption isotherms and x-ray absorption fine structure (XAFS) spectra on Ca K-edge. The adsorbed density of Ca 2+ per unit micropore volume in the narrower pore was higher than in the wider pore, while the adsorbed amount per unit mass of carbon with the narrower pore was half of the amount of ACs with the larger pore. On the other hand, variations in the bands assigned to double-electron (KM I) and 1s→ 3d excitations in XAFS spectra demonstrate the formation of a distorted hydration cluster around Ca 2+ in the micropore, although the structural parameters of hydrated Ca 2+ in the micropores were almost consistent with the bulk aqueous solution, as revealed by the analysis of extended XAFS (EXAFS) spectra. In contrast to the hydration structure of monovalent ions such as Rb+, which generally presents a dehydrated structure in smaller than 1 nm micropores in ACs, the present study clearly explains that the non-spherically-symmetric structure of hydrated Ca 2+ restricted in carbon micropores whose sizes are around 1 nm is experimentally revealed where any dehydration phenomena from the first hydration shell around Ca 2+ could not be observed.