Cerón Maira R, Aydin Fikret, Hawks Steven A, Oyarzun Diego I, Loeb Colin K, Deinhart Amanda, Zhan Cheng, Pham Tuan Anh, Stadermann Michael, Campbell Patrick G
Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, United States.
ACS Appl Mater Interfaces. 2020 Sep 23;12(38):42644-42652. doi: 10.1021/acsami.0c07903. Epub 2020 Sep 15.
Capacitive deionization (CDI) is a promising water desalination technology that is applicable to the treatment of low-salinity brackish waters and the selective removal of ionic contaminants. In this work, we show that by making a small change in the synthetic procedure of hierarchical carbon aerogel monolith (HCAM) electrodes, we can adjust the pore-size distribution and tailor the selectivity, effectively switching between selective adsorption of calcium or sodium ions. Ion selectivity was measured for a mixture of 5 mM NaCl and 2.5 mM CaCl. For the low activated flow-through CDI (fteCDI) cell, we observed extremely high sodium selectivity over calcium ( ≫ 10, no Ca adsorbed) at all of the applied potentials, while for the highly activated fteCDI cell, we observed a selectivity value of 6.6 ± 0.8 at 0.6 V for calcium over sodium that decreased to 2.2 ± 0.03 at 1.2 V. Molecular dynamics simulations indicated that the loss in Ca selectivity over Na at high applied voltages could be due to a competition between ion-pore electrostatic interactions and volume exclusion ("crowding") effects. Interestingly, we also find with these simulations that the relative sizes of the ions change due to changes in hydration at a higher voltage.
电容去离子化（CDI）是一种很有前景的水脱盐技术，适用于处理低盐度微咸水和选择性去除离子污染物。在这项工作中，我们表明，通过对分级碳气凝胶整体电极（HCAM）的合成过程进行微小改变，我们可以调整孔径分布并定制选择性，从而在钙离子或钠离子的选择性吸附之间有效切换。对5 mM NaCl和2.5 mM CaCl₂的混合物进行了离子选择性测量。对于低活化流通式CDI（fteCDI）电池，我们在所有施加电位下都观察到对钠的选择性极高，超过钙（≫10，无钙吸附），而对于高活化fteCDI电池，我们观察到在0.6 V时钙对钠的选择性值为6.6±0.8，在1.2 V时降至2.2±0.03。分子动力学模拟表明，在高施加电压下钙对钠的选择性损失可能是由于离子 - 孔静电相互作用和体积排斥（“拥挤”）效应之间的竞争。有趣的是，我们还通过这些模拟发现，由于在较高电压下水合作用的变化，离子的相对尺寸会发生变化。
