Laboratory of Organic Chemistry, Wageningen University, Stippeneng 4, 6708 WE Wageningen, The Netherlands.
Environmental Technology, Wageningen University, Bornse Weilanden 9, 6708 WG Wageningen, The Netherlands.
ACS Appl Mater Interfaces. 2020 Aug 5;12(31):34746-34754. doi: 10.1021/acsami.0c05664. Epub 2020 Jul 15.
Capacitive deionization (CDI) is a desalination technique that can be applied for the separation of target ions from water streams. For instance, mono- and divalent cation selectivities were studied by other research groups in the context of water softening. Another focus is on removing Na from recirculated irrigation water (IW) in greenhouses, aiming to maintain nutrients. This is important as an excess of Na has toxic effects on plant growth by decreasing the uptake of other nutrients. In this study, we investigated the selective separation of sodium (Na) and magnesium (Mg) in MCDI using a polyelectrolyte multilayer (PEM) on a standard grade cation-exchange membrane (Neosepta, CMX). Alternating layers of poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS) were coated on a CMX membrane (CMX-PEM) using the layer-by-layer (LbL) technique. The layer formation was examined with X-ray photoelectron spectroscopy (XPS) and static water contact angle measurements (SWA) for each layer. For each membrane, i.e., the CMX-PEM membrane, CMX membrane, and for a special-grade cation-exchange membrane (Neosepta, CIMS), the Na/Mg selectivity was investigated by performing MCDI experiments, and selectivity values of 2.8 ± 0.2, 0.5 ± 0.04, and 0.4 ± 0.1 were found, respectively, over up to 40 cycles. These selectivity values indicate flexible switching from a Mg-selective membrane to a Na-selective membrane by straightforward modification with a PEM. We anticipate that our modular functionalization method may facilitate the further development of ion-selective membranes and electrodes.
电容去离子 (CDI) 是一种脱盐技术，可用于从水流中分离目标离子。例如，其他研究小组在水软化的背景下研究了单价和二价阳离子的选择性。另一个重点是去除温室中再循环灌溉水中的 Na，以维持养分。这一点很重要，因为过量的 Na 会通过减少其他养分的吸收对植物生长产生毒性作用。在这项研究中，我们使用标准等级阳离子交换膜 (Neosepta，CMX) 上的聚电解质多层 (PEM) 在 MCDI 中研究了 Na 和 Mg 的选择性分离。交替层的聚 (盐酸烯丙胺) (PAH) 和聚 (苯乙烯磺酸盐) (PSS) 使用层层 (LbL) 技术涂覆在 CMX 膜 (CMX-PEM) 上。使用 X 射线光电子能谱 (XPS) 和静态水接触角测量 (SWA) 对每一层的层形成进行了检查。对于每种膜，即 CMX-PEM 膜、CMX 膜和特殊等级阳离子交换膜 (Neosepta，CIMS)，通过进行 MCDI 实验研究了 Na/Mg 选择性，并且发现分别为 2.8±0.2、0.5±0.04 和 0.4±0.1 的选择性值，超过 40 个循环。这些选择性值表明，通过简单地用 PEM 修饰，可以灵活地从 Mg 选择性膜切换到 Na 选择性膜。我们预计我们的模块化功能化方法可能会促进离子选择性膜和电极的进一步发展。
