Anion-/cationic compounds enhance the dispersion of flow electrodes to obtain high capacitive deionization performance

Abstract

Flow electrode capacitive deionization (FCDI) possesses continuous desalination capability by using a flowable electrode instead of a fixed electrode, which greatly increases the desalination capacity. However, the poor conductivity of the flow electrode slurry and the high blocking risk of the flow channel limit the larger scale FCDI in deionization. Herein, we report a flow electrode by introducing anion-/cationic compounds as conductive and dispersing agents into activated carbon (AC). A small amount of anion/cationic compounds formed electrostatic repulsion force, which improved the utilization rate and dosage of AC and reduced the co-ion effect in electrode slurry. Through investigation, we found that 20 wt% AC with anion-/cationic compounds (0.13 wt% polyetherimide and 0.25 wt% sulfosuccinic) had a higher salt ion removal rate (2.35 to 5.97 mmol/(m2·s)) and current efficiency (96.23%) than AC alone (0.82 mmol/(m2·s)) at 1.0 V in 0.59–5.06 g/L NaCl solution, which was also higher than that in previous studies. Meanwhile, electrochemical and physical characterization analyses further revealed that polymers can effectively improve the conductivity of the electrode solution and stabilize the pH change of the electrode slurry during the charging process. Ultimately, all effects work together to achieve an efficient desalination system.