In the arid west, the freshwater supply of many communities is limited, leading to increased interest in tapping brackish water resources. Although reverse osmosis is the most common technology to upgrade saline waters, there is also interest in developing and improving alternative technologies. Here we focus on membrane capacitive deionization (MCDI), which has attracted broad attention as a portable and energy-efficient desalination technology. In this study, a fully coupled two-dimensional MCDI process model capable of capturing transient ion transport and adsorption behaviors was developed to explore the function of the ion-exchange membrane (IEM) and detect MCDI influencing factors via sensitivity analysis. The IEM enhanced desalination by improving the counter-ions’ flux and increased adsorption in electrodes by encouraging retention of ions in electrode macropores. An optimized cycle time was proposed with maximal salt removal efficiency. The usage of the IEM, high applied voltage, and low flow rate were discovered to enhance this maximal salt removal efficiency. IEM properties including water uptake volume fraction, membrane thickness, and fixed charge density had a marginal impact on cycle time and salt removal efficiency within certain limits, while increasing cell length and electrode thickness and decreasing channel thickness and dispersivity significantly improved overall performance.

中文翻译：

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通过全耦合二维过程模型探索离子交换膜在膜电容去离子中的作用

在干旱的西部，许多社区的淡水供应有限，导致人们对挖掘咸淡水资源的兴趣增加。尽管反渗透是升级盐水的最常用技术，但也有兴趣开发和改进替代技术。在这里，我们将重点放在膜电容去离子（MCDI）上，它作为一种便携式且节能的脱盐技术受到了广泛的关注。在这项研究中，开发了一种能够捕获瞬态离子传输和吸附行为的全耦合二维MCDI过程模型，以探索离子交换膜（IEM）的功能并通过敏感性分析检测MCDI影响因素。IEM通过改善抗衡离子的通量来增强淡化效果，并通过鼓励离子保留在电极大孔中来增加电极中的吸附。提出了具有最大除盐效率的最佳循环时间。发现IEM的使用，高施加电压和低流速可增强这种最大的除盐效率。IEM特性（包括吸水量分数，膜厚度和固定电荷密度）在一定范围内对循环时间和除盐效率有边际影响，而增加电池长度和电极厚度以及减小通道厚度和分散性可显着改善整体性能。发现低流速可以提高这种最大的除盐效率。IEM特性（包括吸水量分数，膜厚度和固定电荷密度）在一定范围内对循环时间和除盐效率有边际影响，而增加电池长度和电极厚度以及减小通道厚度和分散性可显着改善整体性能。发现低流速可以提高这种最大的除盐效率。IEM特性（包括吸水量分数，膜厚度和固定电荷密度）在一定范围内对循环时间和除盐效率有边际影响，而增加电池长度和电极厚度以及减小通道厚度和分散性可显着改善整体性能。