Abstract
Capacitive deionization (CDI) has gained a lot of attention as a promising water desalination technology. Among several CDI architectures, multichannel membrane CDI (MC-MCDI) has recently emerged as one of the most innovative systems to enhance the ion removal capacity. The principal feature of MC-MCDI is the independently controllable electrode channels, providing a favorable environment for the electrodes and enhancing the desalination performance. Furthermore, MC-MCDI has been studied in various operational modes, such as concentration gradient, reverse voltage discharging for semi-continuous process, and increase of mass transfer. Furthermore, the system configuration of MC-MCDI has been benchmarked for the extension of the operation voltage and sustainable desalination. Given the increasing interest in MC-MCDI, a comprehensive review is necessary to provide recent research efforts and prospects for further development of MC-MCDI. Therefore, this review actively addresses the major principle and operational features of MC-MCDI along with conventional CDI for a better understanding of the MC-MCDI system. In addition, the innovative applications of MC-MCDI and their notable improvements are also discussed. Finally, this review briefly mentions the major challenges of MC-MCDI as well as proposes future research directions for further development of MC-MCDI as scientific and industrial desalination technologies.
Highlights
Capacitive deionization (CDI) has drawn increasing interest in water desalination, wastewater treatment, and resource recovery [1,2,3,4]
Measured conductivities, ν is the volumetric flow rate (L/min), MNaCl is the molecular weight of NaCl where C0 and Ct are the initial and effluent concentrations which were converted from the measured conductivities, ν is the volumetric flow rate (L/min), MNaCl is the molecular weight of NaCl (g/mol), m is the total mass of the carbon electrodes (g), mwk is the total mass of the working electrodes (g), and t is the operation time for the charging step or the total desalination cycle(s)
FCDI has overcome several limitations seen in the static-electrode CDI, it is hindered by various obstacles, including relatively high energy consumption associated with the regeneration of the charged carbon particles, agglomeration of the carbon slurry, and extremely low conductivity of the flow electrodes [1]
Summary
Capacitive deionization (CDI) has drawn increasing interest in water desalination, wastewater treatment, and resource recovery [1,2,3,4]. Over the last few decades, CDI has become remarkably advanced with various types of electrodes including capacitive electrodes with carbonaceous materials (i.e., activated carbon, carbon aerogel, carbon nanotubes, and graphene) [11,12,13,14,15] and faradaic electrodes with battery and battery-like materials (i.e., sodium manganese oxide, molybdenum disulfide, Mxene, silver/silver chloride, and Prussian blue analogs) [16,17,18,19,20] These electrode materials have led to novel systematic developments. Several theoretical studies discovered that the desalination performance of CDI was directly related to a correlation of the pore size distribution and the ion removal capacity [31] All of these theoretical investigations provide one of the most important criteria for choosing an appropriate material and for considering the synthetic method of electrodes in CDI. The major challenges and future research direction for further development of MC-MCDI are discussed
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