Department of Environmental Technology, Wageningen University, Wageningen, The Netherlands.
J Colloid Interface Sci. 2011 Aug 1;360(1):239-48. doi: 10.1016/j.jcis.2011.04.049. Epub 2011 Apr 24.
Membrane capacitive deionization (MCDI) is a technology for water desalination based on applying an electrical field between two oppositely placed porous electrodes. Ions are removed from the water flowing through a channel in between the electrodes and are stored inside the electrodes. Ion-exchange membranes are placed in front of the electrodes allowing for counterion transfer from the channel into the electrode, while retaining the coions inside the electrode structure. We set up an extended theory for MCDI which includes in the description for the porous electrodes not only the electrostatic double layers (EDLs) formed inside the porous (carbon) particles, but also incorporates the role of the transport pathways in the electrode, i.e., the interparticle pore space. Because in MCDI the coions are inhibited from leaving the electrode region, the interparticle porosity becomes available as a reservoir to store salt, thereby increasing the total salt storage capacity of the porous electrode. A second advantage of MCDI is that during ion desorption (ion release) the voltage can be reversed. In that case the interparticle porosity can be depleted of counterions, thereby increasing the salt uptake capacity and rate in the next cycle. In this work, we compare both experimentally and theoretically adsorption/desorption cycles of MCDI for desorption at zero voltage as well as for reversed voltage, and compare with results for CDI. To describe the EDL-structure a novel modified Donnan model is proposed valid for small pores relative to the Debye length.
膜电容去离子（MCDI）是一种基于在两个相对放置的多孔电极之间施加电场的海水淡化技术。离子从流过电极之间通道的水中被去除，并储存在电极内部。离子交换膜放置在电极前面，允许反离子从通道转移到电极中，同时将共离子保留在电极结构内部。我们建立了一个扩展的 MCDI 理论，该理论在多孔电极的描述中不仅包括在多孔（碳）颗粒内部形成的静电双电层（EDL），还包括电极中传输途径的作用，即颗粒间的孔隙空间。因为在 MCDI 中，共离子被抑制离开电极区域，所以颗粒间的孔隙率可以作为储存盐的储库，从而增加多孔电极的总盐储存容量。MCDI 的第二个优点是，在离子解吸（离子释放）期间可以反转电压。在这种情况下，颗粒间的孔隙率可以耗尽反离子，从而增加下一个循环的盐吸收容量和速率。在这项工作中，我们从实验和理论上比较了 MCDI 在零电压和反向电压下的吸附/解吸循环，并与 CDI 的结果进行了比较。为了描述 EDL 结构，提出了一种新的改进的唐南模型，该模型在相对于德拜长度的小孔中有效。
