Enhancing the Total Salt Adsorption Capacity and Monovalent Ion Selectivity in Capacitive Deionization Using a Dual-Layer Membrane Coating Electrode

Abstract

Capacitive deionization (CDI) is highly attractive for seawater desalination, while the trade-off between total salt adsorption capacity (SAC) and monovalent ion selectivity is a big challenge for current electrodes, especially facing solution containing organics. Herein, a simple approach was used to prepare a novel dual-layer membrane coating electrode (D-MCE) by depositing ion exchange polymers onto activated carbon fiber (ACF) to overcome this issue. Performances of the ACF, singlelayer MCE, anion exchange membrane ACF, and D-MCE were investigated. Compared to ACF, the single-layer MCE showed an increased total SAC from 435.7 to 593.0 μmol/g with a reduced Cl − /SO 4 2− selectivity from 0.9 to 0.4. The introduction of the membrane increased total SAC to 524.3 μmol/g and decreased Cl − /SO 4 2− selectivity to 0.7. The D-MCE exhibited an improved total SAC to 679.5 μmol/g by inhibiting the co-ion repulsion and Faradaic reaction. Meanwhile, the D-MCE enabled fast Cl − diffusion and presented a high selectivity (3.8). After 50 cycles, the D-MCE exhibited an almost unchanged total SAC and selectivity even in the presence of organics. The narrowed pores and negative outermost layer endowed the D-MCE with an outstanding anti-fouling behavior, which well explained its stable performance. These findings confirmed the high potential of the D-MCE in addressing the trade-off and provided valuable insights into the design of the CDI electrode for desalination.

Bipolar Membrane Capacitive Deionization for pH-Assisted Ionic Separations

“…The salt adsorption capacity (SAC) of ion (copper or sodium cations in the experiments for selective removal of copper from brine mixtures or chloride or itaconate anions in the experiments for selective removal of itaconate anions from fermentation broth) is calculated as V f = volume of feed solution (L) and m = mass of electrode (g).…”

Aryl ether-free polymer electrolytes for electrochemical and energy devices

“…In research focusing on the selective removal of heavy metal ions [701][702][703][704] or minerals, [705][706][707][708][709][710][711] AEPs are employed in processes like MCDI or adsorption. In the MCDI process, the membrane traps co-ions into intraparticle pores, enhancing the accumulation of counterions in macropores.…”