Abstract Reverse osmosis (RO), nanofiltration (NF), and ion exchange (IX) membranes are becoming increasingly important in water treatment, waste recovery, industrial product purification, renewable energy generation, and energy storage. While all three types of membranes are charged, dense polymers, each has historically been characterized using different methods relevant to their respective applications. This bifurcated characterization approach has obscured similarities among dense membranes that could potentially be exploited to advance membrane development. For example, we recently showed that the water and salt transport properties of commercial IX membranes, which are not frequently reported, are generally on the same order of magnitude as those of other desalination polymers. These findings beg the question whether IX membrane polymers might offer any advantages over RO/NF membranes for pressure-driven desalination, and invite further comparisons among the two different classes of membrane polymers (e.g., IX and RO/NF membranes). In this study, we used the solution-diffusion model as a common framework to compare the permeability, partition and diffusion coefficients, water permeance, and salt rejection of twenty commercial IX membranes with those of the active layers of commercial RO/NF membranes and other membrane polymers. Our analysis shows that the characteristics of all membranes fall within similar ranges, despite differences in intended use (e.g. pressure-driven vs. electric field-driven separations). Thus, the low water permeance of IX membranes compared to RO/NF membranes can be explained primarily by differences in thickness rather than permeability. We also show that IX membranes have excellent water/salt partitioning selectivity, while RO/NF active layers have superior diffusion selectivity, and discuss the implications of this comparison for ongoing membrane research.

中文翻译：

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用于海水淡化和能源应用的离子交换膜、反渗透膜和纳滤膜的水和盐传输特性的比较

摘要 反渗透 (RO)、纳滤 (NF) 和离子交换 (IX) 膜在水处理、废物回收、工业产品净化、可再生能源发电和储能中变得越来越重要。虽然所有三种类型的膜都是带电的、致密的聚合物，但历史上每一种都使用与其各自应用相关的不同方法进行表征。这种分叉的表征方法掩盖了致密膜之间的相似性，这些相似性可能被用来促进膜的发展。例如，我们最近表明，商业 IX 膜的水和盐传输特性（不常被报道）通常与其他脱盐聚合物处于同一数量级。这些发现回避了 IX 膜聚合物在压力驱动脱盐方面是否比 RO/NF 膜更具优势的问题，并邀请对两种不同类型的膜聚合物（例如 IX 和 RO/NF 膜）进行进一步比较。在本研究中，我们使用溶液扩散模型作为通用框架来比较 20 种商用 IX 膜与商用 RO/NF 膜和其他活性层的渗透性、分配和扩散系数、透水性和盐截留率。膜聚合物。我们的分析表明，尽管预期用途不同（例如压力驱动分离与电场驱动分离），所有膜的特性都在相似的范围内。因此，与 RO/NF 膜相比，IX 膜的低水渗透性主要是由厚度而不是渗透性的差异来解释的。我们还表明 IX 膜具有出色的水/盐分配选择性，而 RO/NF 活性层具有出色的扩散选择性，并讨论了这种比较对正在进行的膜研究的影响。