Graduate Institute of Environmental Engineering, National Taiwan University, No. 1, Sec. 4. Roosevelt Rd., Taipei, 10617, Taiwan.
Graduate Institute of Environmental Engineering, National Taiwan University, No. 1, Sec. 4. Roosevelt Rd., Taipei, 10617, Taiwan; Water Innovation, Low Carbon and Environmental Sustainability Research Center, National Taiwan University, Taipei, 10617, Taiwan.
Chemosphere. 2021 Jul;274:129762. doi: 10.1016/j.chemosphere.2021.129762. Epub 2021 Jan 26.
The main objective of the study is to explore the removal characteristics of Cu and Zn ions in activated carbon-based capacitive deionization (CDI). In this work, CDI experiments were performed to remove divalent ions (e.g., Cu, Zn, and Ca) from single- and multicomponent aqueous solutions. As evidenced, divalent heavy metals could be successfully removed by charging the CDI cell at 1.2 V. Notably, the preferential removal of Cu ions over Zn and Ca ions was observed in the charging step. The removal capacities for Cu, Zn, and Ca ions in a competitive environment were 29.6, 19.6, and 13.8 μmol/g, respectively. In contrast, the regeneration efficiencies for the removal of Cu and Zn were much lower than that of Ca, suggesting the occurrence of irreversible Faradaic reactions on the cathode. X-ray photoelectron spectroscopy analysis demonstrated that Cu ions were reduced to Cu(I) and Zn ions were transformed to ZnO/Zn(OH) on the cathode. Therefore, there were two major mechanisms for the removal of divalent heavy metal ions: capacitive electrosorption and cathodic electrodeposition. Specifically, the reduction potential played a crucial role in determining the removal characteristics. When regarding divalent cations with similar hydrated sizes, the divalent cation with a higher reduction potential tended to be separated by cathodic electrodeposition rather than double-layer charging, indicating the high removal selectivity of activated carbon-based CDI. This paper constitutes a significant contribution to promoting the application of CDI for contaminant sequestration.
本研究的主要目的是探讨基于活性炭的电容去离子（CDI）中 Cu 和 Zn 离子的去除特性。在这项工作中，进行了 CDI 实验以从单组分和多组分水溶液中去除二价离子（例如 Cu、Zn 和 Ca）。结果表明，通过在 1.2 V 下对 CDI 单元充电，可以成功去除二价重金属。值得注意的是，在充电步骤中观察到 Cu 离子优先于 Zn 和 Ca 离子被去除。在竞争环境中，Cu、Zn 和 Ca 离子的去除容量分别为 29.6、19.6 和 13.8 μmol/g。相比之下，Cu 和 Zn 的再生效率远低于 Ca，表明在阴极上发生了不可逆的法拉第反应。X 射线光电子能谱分析表明，Cu 离子被还原为 Cu(I)，Zn 离子被转化为 ZnO/Zn(OH)。因此，去除二价重金属离子有两种主要机制：电容静电吸附和阴极电沉积。具体来说，还原电位在确定去除特性方面起着关键作用。当涉及具有相似水合尺寸的二价阳离子时，具有较高还原电位的二价阳离子更倾向于通过阴极电沉积而不是双层充电来分离，这表明基于活性炭的 CDI 具有较高的去除选择性。本文为促进 CDI 在污染物捕获中的应用做出了重要贡献。
