Precise manipulation of the charge percolation networks of flow-electrode capacitive deionization using a pulsed magnetic field

Abstract

Magnetic field is a simple and powerful means that enables controlled the transport of electrode particles in flow electrode capacitive deionization (FCDI). However, the magnetic particles are easily stripped from hybrid suspension electrodes and the precise manipulation of the charge percolation network remains challenging. In this study, a programmable magnetic field was introduced into the FCDI system to enhance the desalination performance and operational stability of magnetic FCDI, with core-shell magnetic carbon (MC) used as an alternative electrode additive. The results showed that the pulsed magnetic field (PMF) was more effective in enhancing the average salt removal rate (ASRR) compared to the constant magnetic field (CMF), with 51.6% and 67.7% enhancement, respectively, compared to the magnetic field-free condition. The outstanding advantage of the PMF lies in the enhancement in the trapping and mediating effects in the switching magnetic field, which keeps the concentration of the electrode particles near the current collector at a high level and greatly facilitates electron transport. In long-term operation (20,000 cycles), the pulsed magnetic FCDI achieved a stable desalinating rate of 0.4–0.68 μmol min–1 cm–2 and a charge efficiency of >96%. In brief, our study introduces a new approach for the precise manipulation of charge percolation networks of the suspension electrodes and provides insight into the charging mechanism of the magnetic FCDI.