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Membrane Capacitive Deionization with Constant Current vs Constant Voltage Charging: Which Is Better?
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2018-03-22 00:00:00 , DOI: 10.1021/acs.est.7b06064
Li Wang 1 , Shihong Lin 1, 2
Affiliation  

Membrane capacitive deionization (MCDI) can be typically operated with constant voltage (CV) or constant current (CC) mode in the charging stage. While a series of previous studies have compared both charging modes to identify the better operating mode, neither their performance evaluation protocols were consistent, nor did their conclusions unanimously converge. This study presents a new framework to evaluate and compare MCDI performance, considering the kinetic efficiency, the energetic efficiency, and the intrinsic trade-off between the two. A key prerequisite for making rational comparison of performance between MCDI operations is that the operations being compared should all result in the same target adsorption. With this key prerequisite and the new evaluation framework based on the trade-off curve between kinetic and energetic efficiencies, our experimental assessment and theoretical analysis suggest that whether CC or CV charging is more efficient is strongly dependent on the target adsorption and, to a less extent, on the kinetic rate of charging. However, the advantage in energy or kinetic efficiency of one charging mode over that of the other is relatively small in all cases. Our study also reveals that, for a given MCDI system, there exist regimes of target adsorptions and kinetic rates that can only be achieved by either CC or CV charging, or even regimes that can be achieved by neither charging mode. In summary, this study revises our current understanding regarding the comparison of the two typical charging modes in MCDI, and introduces a new framework for comparing the performance of different MCDI and CDI operations.

中文翻译:

恒定电流与恒定电压充电的膜电容去离子:哪个更好?

膜电容去离子(MCDI)通常可以在充电阶段以恒定电压(CV)或恒定电流(CC)模式运行。虽然之前的一系列研究比较了两种充电模式以识别更好的运行模式,但它们的性能评估协议均不一致,其结论也未取得一致。这项研究提出了一个评估和比较MCDI性能的新框架,其中考虑了动力学效率,能量效率以及两者之间的内在取舍。对MCDI操作之间的性能进行合理比较的关键前提是要比较的操作都应导致相同的目标吸附。有了这个关键的先决条件和基于动能之间的权衡曲线的新评估框架,我们的实验评估和理论分析表明,CC充电或CV充电是否更有效,在很大程度上取决于目标吸附,而在较小程度上取决于充电的动力学速率。然而,在所有情况下,一种充电模式在能量或动能效率方面优于另一种充电模式的优势相对较小。我们的研究还表明,对于给定的MCDI系统,存在仅通过CC或CV充电才能实现的目标吸附和动力学速率方案,甚至无法通过两种充电方式实现的方案。总而言之,本研究修订了我们目前对MCDI中两种典型计费模式比较的理解,并引入了一个新的框架来比较不同MCDI和CDI操作的性能。
更新日期:2018-03-22
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