Leong Zhi Yi, Yang Hui Ying
Pillar of Engineering Product Development (EPD), Singapore University of Technology and Design, 8 Somapah Road, Singapore 487372.
ACS Omega. 2020 Jan 28;5(5):2097-2106. doi: 10.1021/acsomega.9b02330. eCollection 2020 Feb 11.
Water softening is a relatively untapped area of research in capacitive deionization (CDI). In this work, we demonstrate how an asymmetric combination of oxidized and aminated carbon can be used for selective removal of divalent cations for water softening. We first show how higher electrosorption performances can be achieved in single-salt experiments involving NaCl, KCl, MgCl, and CaCl before proceeding to multi-salt experiments using different combinations of the four salts. The salt combinations are chosen to investigate one of the three factors: (1) ionic mass, (2) ionic charge, or (3) concentration. We show how divalent selectivity can be achieved due to high local electrostatic attraction between negatively charged oxygen moieties and divalent cations. Additionally, an ion-exchange process between the oxidized carbon surface and cations can result in lower pH values, which prevent the precipitation of scale-forming ions.
水软化是电容去离子化（CDI）中一个相对未被充分研究的领域。在这项工作中，我们展示了氧化碳和胺化碳的不对称组合如何用于选择性去除二价阳离子以实现水软化。我们首先展示了在涉及氯化钠、氯化钾、氯化镁和氯化钙的单盐实验中如何实现更高的电吸附性能，然后再进行使用这四种盐的不同组合的多盐实验。选择盐组合是为了研究以下三个因素之一：（1）离子质量，（2）离子电荷，或（3）浓度。我们展示了由于带负电荷的氧部分与二价阳离子之间的高局部静电吸引力如何实现二价选择性。此外，氧化碳表面与阳离子之间的离子交换过程会导致pH值降低，从而防止结垢离子沉淀。
