College of Chemical Engineering, State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing, 211816, People's Republic of China.
Environ Sci Pollut Res Int. 2022 Jun;29(29):44794-44805. doi: 10.1007/s11356-022-19002-7. Epub 2022 Feb 9.
Calcium and magnesium ions usually exist in natural water. When Cd is removed from water by adsorption, it will be inhibited by these two ions. Titanate nanotubes (TNTs) have an effective adsorption capacity for Cd due to extraordinary ion exchange property. However, TNTs also adsorb Ca and Mg in water. In this study, carbon-modified TNT (TNT/C) and TNT/C further treated with acid (TNT/HC) were synthesized by hydrothermal synthesis. The transmission electron microscope (TEM) images show that TNT/C or TNT/HC still keep nanotube morphology. The experimental results show the order of adsorption amount to Cd is TNT (171.56 mg/g) > TNT/C (166 mg/g) > TNT/HC (159.88 mg/g) when there is no Ca or Mg. But when there is 0.1 M Ca or Mg in the water, the order of Cd adsorption capacity becomes TNT/HC (44.28, 49.04 mg/g) > TNT/C (58.84, 69.32 mg/g) > TNT (65.52, 70.6 mg/g). It indicates that the surface carbon modification can alleviate the hindrance of Ca or Mg to Cd removal. This is because the carbon on the surface of TNT captured part of Ca or Mg; it made more Cd be successfully absorbed by TNT through ion exchange. This mechanism was confirmed by the X-ray photoelectron spectroscopy (XPS) spectra analysis. The results of this paper can provide ideas for the adsorption and removal of Cd in water in the presence of Ca or Mg.
钙和镁离子通常存在于天然水中。当 Cd 通过吸附从水中去除时，它会受到这两种离子的抑制。由于具有非凡的离子交换特性，钛酸盐纳米管（TNTs）对 Cd 具有有效的吸附能力。然而，TNTs 也会吸附水中的 Ca 和 Mg。在这项研究中，通过水热合成合成了碳改性 TNT（TNT/C）和进一步用酸处理的 TNT/C（TNT/HC）。透射电子显微镜（TEM）图像表明，TNT/C 或 TNT/HC 仍保持纳米管形态。实验结果表明，当没有 Ca 或 Mg 时，Cd 吸附量的顺序为 TNT（171.56mg/g）>TNT/C（166mg/g）>TNT/HC（159.88mg/g）。但是，当水中有 0.1M Ca 或 Mg 时，Cd 吸附量的顺序变为 TNT/HC（44.28、49.04mg/g）>TNT/C（58.84、69.32mg/g）>TNT（65.52、70.6mg/g）。这表明表面碳改性可以减轻 Ca 或 Mg 对 Cd 去除的阻碍。这是因为 TNT 表面的碳捕获了部分 Ca 或 Mg，通过离子交换使更多的 Cd 被 TNT 成功吸收。X 射线光电子能谱（XPS）谱分析证实了这一机制。本文的研究结果可为 Ca 或 Mg 存在下水相中 Cd 的吸附和去除提供思路。
