Flow-electrode Capacitive Deionization System Research Articles

Novel flow-electrode capacitive deionization system employing modified MOF-derived carbon electrodes for metal ion removal

Activated carbon (AC) as an electrode for capacitive deionization (CDI) is constrained by its low specific surface area and specific capacitance, leading to electrical double layer overlap (EDL). To address this issue, a flow electrode capacitive deionization system (MDC-FCDI) was developed, which used modified MOFs-derived carbon (MDC) as the electrode. The MDC electrode exhibited enhanced specific capacitance (145.78 F/g) and specific surface area (2458.44 m2/g). Compared to conventional FCDI, the MDC-FCDI system demonstrated a 35–39 % improvement in heavy metal removal efficiency from wastewater containing Pb2+, Cu2+, Cd2+, and Zn2+. The selectivity of MDC-FCDI for heavy metals exhibited a unique “two-step phenomenon” that differed from what was observed in conventional CDI systems. In the MDC-FCDI system, high-valent ions experienced stronger electric field forces and preferentially occupied active sites on the electrode surface prior to the adsorption of ions with lower valence. The selectivity of the MDC-FCDI system for heavy metal ions is determined by three factors in the following order of priority: ionic charge, hydration radius, and ion feed concentration. This study offers a practical approach for expanding the range of MDC-FCDI applications.

Optimization of the intermediate chamber improves desalination performance in flow electrode capacitive deionization (FCDI): A comparative study

Flow electrode capacitive deionization (FCDI), a novel ion removal technology, is influenced by various factors such as electrode material properties, fluid flow rate, and device structure. In the FCDI system, the intermediate chamber is the core element where ions migrate towards the cathode and anode to complete the adsorption process. In this study, we designed a hollow plastic plate with channels (PP) and a hollow graphite plate with channels (GP) as the intermediate chamber, compare and study with conventional plastic mesh (PM) chambers. CFD simulations revealed that the newly designed PP and GP chambers significantly reduced the hydraulic stagnation zone. The results of the desalination experiments revealed that the desalination efficiency of the GP-FCDI was 1.5 and 1.9 times higher than that of the PP-FCDI and PM-FCDI, respectively. At the same time, in situ potential measurement (ISPM) was used to monitor the voltage drop of each component in FCDI, thereby accurately calculated the proportion of energy consumption in the intermediate chamber. The results indicate that the energy consumption of the intermediate chamber of GP-FCDI was 54 % less than that of PM-FCDI. The current work will help us provide new insights for the design and optimization of FCDI systems.

A novel two-stage continuous capacitive deionization system with connected flow electrode and freestanding electrode

The desalination of seawater/wastewater utilizing flow-electrode capacitive deionization (FCDI) has received significant interest. However, challenges like the low electrical conductivity of flow electrode and excessive energy consumption have prevented the scaling up of desalination operations. To overcome these issues, this study introduces a new FCDI system termed the two-stage FCDI (TS-FCDI) system, in which desalination modules are equipped with freestanding and flow electrode. The TS-FCDI system offers a graded desalination module design that produces an average salt removal rate (ASRR) of 113 µg cm2·min−1. However, the TS-FCDI system requires substantially reduced infrastructure investment, device size, and energy expenses. Notably, the design allows for the simultaneous operation of freestanding and flow electrode and enables the transport of ions and charges in the electrode region. Experimental evidence from multiple device configurations (CDI, FCDI, and TS-FCDI) supports this claim. Notably, the TS-FCDI system shows about twice the desalination performance over FCDI, with approximately 50 h of single-cycle (SC) operation. This enhancement links the freestanding electrode with the flow electrode, enabling the device to be well-suited for practical applications. The continuous flow of electrode particles in contact with the freestanding electrode initiates secondary ion transport, merging two different types of electrodes to enhance the active space of the electrode, effectively improving ion adsorption performance. In summary, the results of this study indicate the potential of the TS-FCDI system as a suitable desalination technology for scaling up applications.

Flow electrode capacitive desalination of industrial RO reject.

Flow electrode capacitive deionization (FCDI) is a promising technology for efficiently treating industrial brine with high salt content. However, its desalination performance is currently limited by internal resistance. Achieving an effective FCDI system relies on active electrode materials with high conductivity. This study compares the desalination performances of the widely used flow electrode activated carbon (AC) with more conductive materials, reduced graphene oxide (rGO), and ZnO/rGO composite. Additionally, the lack of particle-to-particle contact in the flow electrode contributes to internal resistance and to address this, a cationic surface-active agent is introduced. This agent forms a stable dispersion, creating a space for enhanced mass loading of the active material. This modification enhances the conductive network and particle contact, reducing the diffusion path and promoting rapid ion transport. With a 5 wt% loading, ZnO/rGO achieved a 73% salt removal efficiency, surpassing AC at 63%. Furthermore, the surfactant-modified ZnO/rGO flow electrode with a 7 wt% loading demonstrated an 81% salt removal efficiency.

Energetic Comparison of Flow-Electrode Capacitive Deionization and Membrane Technology: Assessment on Applicability in Desalination Fields.

Flow-electrode capacitive deionization (FCDI) is a promising technology for sustainable water treatment. However, studies on the process have thus far been limited to lab-scale conditions and select fields of application. Such limitation is induced by several shortcomings, one of which is the absence of a comprehensive process model that accurately predicts the operational performance and the energy consumption of FCDI. In this study, a simulation model is newly proposed with initial validation based on experimental data and is then utilized to elucidate the performance and the specific energy consumption (SEC) of FCDI under multiple source water conditions ranging from near-groundwater to high salinity brine. Further, simulated pilot-scale FCDI system was compared with actual brackish water reverse osmosis (BWRO) and seawater reverse osmosis (SWRO) plant data with regard to SEC to determine the feasibility of FCDI as an alternative to the conventional membrane processes. Analysis showed that FCDI is competent for operation against brackish water solutions under all possible operational conditions with respect to the BWRO. Moreover, its distinction can be extended to the SWRO for seawater conditions through optimization of its total effective membrane area via scale-up. Accordingly, future directions for the advancement of FCDI was suggested to ultimately prompt the commercialization of the FCDI process.

Pine-derived porous carbon for efficient capacitive deionization and the role of its hierarchical pore structure

Capacitive deionization (CDI) is a low-energy, eco-friendly, and economically viable technology for seawater desalination. In the desalination process of CDI, the pore structure characteristics of electrode materials play a crucial role. In this study, the carbon materials with a hierarchical pore structure were prepared through high-temperature carbonization and KOH activation using pine powder as raw material. When the pine-derived porous carbon (PPC) was used as an electrode material, it was found that its specific capacitance is remarkably consistent with the specific surface area of the mesopores. This discovery provides guidance for further optimization and regulation of biomass-derived carbon electrode materials. The desalination performance of the PPC electrode was studied in detail by CDI and flow-electrode capacitive deionization (FCDI) devices. In NaCl solution with an initial concentration of 700 ppm, the equilibrium adsorption capacities in CDI and FCDI systems are 24.96 mg g−1 and 23.12 mg g−1, respectively. Particularly in FCDI tests, the average adsorption rate reaches 23.3 μg cm−2 min−1, and the desalination rate reaches 98.96 %. The PPC shows an excellent desalination performance, making it a promising efficient electrode material for electrochemical desalination.

Redox flow deionization using Prussian blue and functionalized ion exchange membrane for enhanced selective ion recovery

Flow electrode capacitive deionization (FCDI) is a newly developed water treatment technology that offers better performance than the original, solid electrode capacitive deionization (CDI). By eliminating the need for discharging process, FCDI provides much higher desalination capacity with a continuous desalination operation. Along with applications for salt removal, selective removal and recovery of specific ions are also prominent features of FCDI technology. Characteristics of electrodes and ion exchange membranes play a crucial role in controlling the selectivity of ions in an FCDI system. In this study, we demonstrated selective and continuous ion recovery by combining redox-active Prussian blue as flow electrodes and functionalized ion exchange membranes in FCDI configuration. Prussian blue selectively absorbs monovalent Na+ ions from Na+/Ca2+ mixtures through intercalation reaction, in which a smaller Stokes radius of Na+ ion is more favored to fit in the crystal lattice. Furthermore, such selectivity is much more enhanced through functionalization of a cation-exchange membrane (CEM) with polymer multilayers. A layer-by-layer method was used to deposit poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS) on the CEM. Results showed that polymer multilayers changed the CEM from divalent to monovalent ion-affinity due to different ion sizes and charge density. The combination of Prussian blue and functionalized CEM raised the selectivity for sodium around 17 times compared to a control system (0.2 to 3.35). We believe that our approach can provide insight into various areas including resource production, recovery, removal of toxic ions, and material recycling using an FCDI system.

Towards long-term operation of flow-electrode capacitive deionization (FCDI): Optimization of operating parameters and regeneration of flow-electrode

This study systematically optimized the key operating parameters and interpreted their effecting mechanisms in a flow-electrode capacitive deionization (FCDI) system. The optimal voltage, activated carbon electrode content, electrolyte concentration, feedwater flowrate, and electrode flowrate for desalinating low salinity feedwater (1.0 g L−1 NaCl) were determined to be 1.8 V, 2.0 wt%, 10.0 g L−1, 80 mL min−1, and 60 mL min−1, respectively. The variations of the above parameters can affect the system conductivity, the thickness and stability of the electric double layers, and/or the degree of concentration polarization, thereby influencing the desalination performance. Moreover, a sensitivity analysis identified the operating voltage as the dominant parameter with the most significant influence on the FCDI system. Subsequently, a long-term operation was carried out under single-pass mode. The results showed that the lab-scale FCDI system was able to constantly maintain the desalination efficiency of 1.0 g L−1 feedwater (NaCl) at 40–60 % for multiple operating cycles. Over 99.8 % of electrode material regeneration and desalination efficiency recovery was able to be obtained during a 60-h operation, demonstrating that the FCDI system showed strong stability and long-term operation potential.

Simultaneous removal of tetracycline and copper ions from wastewater by flow-electrode capacitive deionization

ABSTRACT To effectively solve the problem of tetracycline (TC) and Cu2+ contamination in wastewater, this study innovatively proposed a low-energy flow-electrode capacitive deionization (FCDI) technology to simultaneously remove TC and Cu2+ from wastewater. The removal efficiencies of TC and Cu2+ using FCDI was investigated under various voltages, electrode flow rates, influent flow rates, and electrode liquid concentrations. The results showed that the removal efficiency of TC and Cu2+ was 60.78% and 84.43%, respectively. The energy consumption for TC and Cu2+ removal was only 1.76 and 1.10 kWh kg−1, which was lower than other electrochemical systems. The ion removal performance of the FCDI system remained stable after six cycles of continuous operation. These findings demonstrated the promising potential of FCDI as an innovative technology for the simultaneous removal of TC and Cu2+, presenting a significant prospects for application in the water treatment field.

New insights into the performance analysis of flow-electrode capacitive deionization using ferri/ferrocyanide redox couples for continuous water desalination

Flow Electrode Capacitive Deionization (FCDI) is a promising technology that uses carbon materials as flow electrodes in aqueous conditions to enable continuous desalination. In this work, the parametric investigation of the FCDI cell was carried out for low and high surface area activated carbon. When 1 mM/1 mM ferri-/ferrocyanide redox couple in the 1 M NaCl supporting electrolyte containing the 5 wt% high surface area activated carbon and 0.5 wt% MWCNT is circulated as flow electrode at the flow rate of 8 mL/min in the electrode chamber and 0.1 mM NaCl feed water is circulated in single-pass mode at 8 mL/min, the FCDI system achieved a significant improvement in desalination performance up to 76.38 % of SRE, with a high average salt removal rate of 43.925 µg/cm2s @ 2 V, charge efficiency of 20.11 % and average energy consumption of 0.27 kWh/mol, through a thorough parametric investigation. When the FCDI cell was tested with tap water, the average salt removal rate, average energy consumption, and salt removal efficiency were calculated at 6.11 μg/cm2s, 2.46 kWh/mol, and 46.61 % respectively, resulting in the reduction of total dissolved solids of 600 mg/L at the inlet to 365 mg/L at the outlet. The combination of microporous high surface area carbon and ferro-ferri redox couple propelled the desalination performance in comparison with the macroporous low surface area carbon, maximizing the ion removal rate, which further reduced the energy consumption and operating voltage for the process.

Enhanced nitrate removal from groundwater using a conductive spacer in flow-electrode capacitive deionization

Flow-electrode capacitive deionization (FCDI) represents a promising approach for ion separation from aqueous solutions. However, the optimization of spacer, particularly for nitrate-contaminated groundwater systems, has often been overlooked. This research comprehensively investigates the influence of using a conductive (carbon cloth, CC) spacer on nitrate removal performance within FCDI system, comparing it to a non-conductive (nylon net, NN) spacer. In both CC and NN FCDI systems, it is unsurprisingly that nitrate removal efficiency improved notably with the increasing current density and hydraulic retention time (HRT). Interestingly, the specific energy consumption (SEC) for nitrate removal did not show obvious fluctuations when the current density and HRT varied in both systems. Under the auspiciously optimized process parameters, CC-FCDI attained a 20% superior nitrate removal efficiency relative to NN-FCDI, accompanied by a notably diminished SEC for CC-FCDI, registering at a mere 28% of NN-FCDI. This great improvement can be primarily attributed to the decrement in FCDI internal resistance after using conductive spacer, which further confirmed by electrochemical tests such as linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Upon prolonged continuous nitrate removal at the optimized conditions, the CC-FCDI system achieved a consistent 90% nitrate removal efficiency with a low SEC of 2.7–7.8 kWh/kg NO3-N, underscoring its steady performance. Overall, this study highlights the pivotal importance of careful spacer design and optimization in realizing energy-efficient groundwater treatment via FCDI.

Separation of nutrients and acetate from sewage sludge fermentation liquid in flow-electrode capacitive deionization system: Competitive mechanisms of ions and influence of activated carbon

Effective separation of volatile fatty acids (VFAs), ammonia (NH4+-N) and reactive phosphorous (RP) generated from anaerobic fermentation liquid is critically important for efficient resource recovery. Flow-electrode capacitive deionization (FCDI) is proven to be capable of efficient removal of ions, environmentally friendly and cost-effective in operation. The performances of FCDI system in the separation of NH4+-N, RP, and acetate and mechanism of pHs and activated carbon on their performances were investigated. Results showed that a pH of 5.0 promoted the removal of NH4+-N (53.1 %) and RP (39.5 %), and 72.0 % of acetate was retained in the solution, which revealed that removal of NH4+-N and RP, and retention of acetate were evidently affected by speciation of ions. Furthermore, the recovery of NH4+-N and RP was undermined by the adsorption of ions on activated carbon. This study provides a novel insight of ion selective mechanism during the operation of the FCDI system.

Selective chromium and copper recovery from wastewater using flow-electrode capacitance deionization: In-situ reduction mechanism regulating metal charging characteristics

Recovering valuable metal resources from industrial wastewater has environmental and economic significance. Flow-electrode capacitive deionization (FCDI) has been successfully used to remove salt and heavy metals. However, the use of this technology in heavy metal treatment has several limitations, including low selectivity, poor long-term stability, and production of low-quality metal products. In this study, a new strategy for recovering chromium (Cr) from wastewater was proposed using an in-situ reduction method. A liquid membrane chamber (LMC) was introduced into a classic three-chamber FCDI and an extraction solution containing Na2SO3 and NaCl was used to capture Cr in wastewater. During FCDI operation, the CrO42− ions entered the LMC were immediately reduced to Cr3+ and retained in the extraction solution. Completing anions (i.e., Cl−) in the extraction solution maintained the concentration of SO32− ions, and thereby reducing the consumption of reagents. The improved FCDI system exhibited satisfactory separation performance and high stability during semi-continuous operation. Freshwater, Cr, and copper were obtained in the separation chamber, LMC, and flow electrode chamber, respectively. The facile approach may open the doors for the separation and recovery of metal resources from water/wastewater with high scalability and universality.

Polyaniline-derived mesoporous carbon electrode for selective and efficient ammonium removal with in a flow-electrode capacitive deionization system

As an emerging technology for wastewater treatment, Flow-electrode Capacitive Deionization (FCDI) has the advantages of no pollution and low energy consumption. In this study, we obtained a mesoporous carbon named Polyaniline-Derived Mesoporous Carbon (PDMC) with remarkable specific surface area (2728 cm3·g−1) and high specific capacitance (126.63 F·g−1) by carbonizing polyaniline and treating the obtained carbon with KOH. In the FCDI system, we found that PDMC exhibited ammonium removal under the conditions of 1.2 V of voltage, feed water flow rate of 10 ml·min−1, and flow-electrode content of 5 wt%, at which time the average ammonium removal rate and removal efficiency could reach 40.95 mg·m−2·min−1 and 87.3%, respectively. In addition, we conducted continuous cycling experiments and found that the FCDI system could maintain relatively stable results after multiple operations. Finally, the ammonium removal effect and selectivity of PDMC were demonstrated in simulated municipal wastewater experiments. Our study identified a high-performance mesoporous material that can be used in the FCDI system with a simple synthesis method to achieve efficient ammonium removal. This work opens up a new path for ammonium removal by FCDI.

Enhanced salt removal performance using nickel hexacyanoferrate/carbon nanotubes as flow cathode in asymmetric flow electrode capacitive deionization

One of the most widely used CDI processes is flow electrode capacitive deionization (FCDI), which is preferred over conventional CDI with static electrode due to its continuous treatment of high-salt wastewater and ability to scale production. However, the discontinuous charge transport network in flow electrodes restricts the improvement of desalination performance. In this study, we prepared nickel hexacyanoferrate and carbon nanotubes composites (NiHCF@CNTs) by a simple ball-milling method and constructed an asymmetric FCDI (AFCDI) system using NiHCF@CNTs and AC as flow cathode and anode, respectively. Then the desalination performance of AFCDI was examined and compared with that of symmetric FCDI system using AC as both flow electrodes under different conditions. The stability was also investigated by a 20-cycle operation test. It was found that AFCDI system showed higher average salt removal rate and lower energy consumption compared with FCDI, owing to the enhancement of charge transport resulting from the couple of high specific capacitance of NiHCF and excellent electrical conductivity of CNTs. Moreover, AFCDI system has stable desalination performance in continuous operation. These results indicate that compositing Faradic materials and CNTs is an effective strategy for improving desalination performance of FCDI.

Enhancing charge transfer utilizing ternary composite slurry for high-efficient flow-electrode capacitive deionization

Weak contact between activated carbon (AC) particles results in a poor conductivity for the electrode slurry, which limits the improved desalination performance in flow-electrode capacitive deionization (FCDI). Based on the bridging and filling effects of nanoparticles, we report a ternary composite slurry with multi-dimensional sized carbon particles by introducing the carbon nanotubes (CNT) and carbon black (CB) into AC-based slurry, namely AC/(CB + CNT) slurry. Further enhanced electrical conductivity relative to conventional pure AC slurry. By comparison analysis, FCDI system with the ternary carbon composite slurry had a faster average salt removal rate (ASAR) of 1.89 μmol cm−2 min−1 under at 1.2 V in a feed salinity of 2.0 g L−1, which is 3.27 1.92 and 1.46 times that of pure AC, AC/CB and AC/CNT slurry. In long-term operation (1800 min, U = 1.6 V), the AC/(CB + CNT) slurry exhibited a stable ASAR of 4.41 μmol cm−2 min−1 and maintained a charging efficiency (CE) of around 96% and molar energy consumption (Em) of 0.043 kWh mol−1. Electrochemical analysis and computational fluid dynamics (CFD) simulation further confirms that AC/(CB + CNT) slurry enable system with a point-to-line-to-surface connection morphology, which generates a robust charge percolation network with diverse pathway and facilitates the charge transfer. In summary, this study developed a facile strategy for increasing the slurry conductivity to provide a feasible approach in efficient desalination application.

A novel four-chamber flow electrode capacitive deionization system for continuous recovery of heavy metal ions from wastewater

In view of the pollution of heavy metals to the environment and the importance for the industrial production, the removal and recovery of heavy metals from various water system is of great importance. In this study, a novel four-chamber flow electrode capacitive deionization (F-FCDI) process is constructed and successfully applied to the removal and recovery of heavy metal ions. Compared with conventional flow electrode capacitive deionization (FCDI) system, the F-FCDI system exhibits higher salt removal efficiency, faster salt removal rate, and lower energy consumption. The effect of different operating parameters on the removal efficiency of copper ions by F-FCDI system is studied, including the initial metal ions concentrations, the applied voltage, and the activated carbon content. The enrichment performance of the constructed F-FCDI system was evaluated under the optimal conditions (applied voltage 1.2 V, 5 wt% activated carbon content). 2000 mL Cu2+ solution with initial concentration 100 ppm was recycled in the F-FCDI system for 48 h and successfully enriched to 50 mL of concentrate solution. The enrichment factors reached 28.5 times, and the removal and enrichment of Cu2+ were realized synchronously. The removal efficiency of some other metal ions, like Ca2+, Mg2+, Pb2+, Cd2+, Co2+ was also evaluated. The removal efficiency can also reach more than 90% in F-FCDI system (initial concentrations 100 ppm). This study provides reference value for the removal and recovery of heavy metal ions in the future.

Selective and continuous ion recovery using flow electrode capacitive deionization with polymer multilayers functionalized ion exchange membrane

Flow electrode capacitive deionization (FCDI) is a newly developed salt removal technology that overcomes the limitations of conventional CDI by eliminating the need for a discharging process, thus achieving much higher desalination capacity and a continuous desalination operation. In this study, we aimed to achieve selective and continuous sodium recovery from Na+/Ca2+ mixtures through FCDI by utilizing polymer multilayer functionalized cation-exchange membranes (CEM). A layer-by-layer method was used to deposit polymer multilayers consisting of PAH (poly allylamine hydrochloride) and PSS (poly styrene sulfonate) on the CEM. Changes in the concentration of feed electrolyte, number of coated polymer layers, and type of outermost layer were investigated in terms of their effect on the selective ion separation. The functionalized CEM switches from a divalent ion affinity to a monovalent ion affinity due to their different ion sizes and charge densities. As the number of polymer layers increased, the selectivity of Na+/Ca2+ increased, reaching up to 3.26 from 0.16 for pristine CEM. We believe that our approach can provide insight into the selective recovery of valuable materials including lithium-ion battery recycling, the recovery of noble metals, and the separation of toxic ions using the FCDI system.

Process model for flow-electrode capacitive deionization for energy consumption estimation and system optimization

Flow-electrode capacitive deionization (FCDI) is a new technology for ion removal that delivers sustainable deionization performance. However, FCDI consumes relatively high amounts of energy compared with other conventional desalination technologies, which hinders the industrial application of FCDI. In this study, the energy consumption of each FCDI component was simulated using a steady-state FCDI model to investigate and optimize the main components of energy consumption. Overall, the established process model can be used for theoretical investigation and enhancing our fundamental understanding of the energy consumption of each FCDI component, and provides the design and optimization of FCDI systems. The results showed that the energy consumption of the flow electrodes dominated under most conditions. Changing the operating parameters could obviously affect energy consumption and the energy consumption structure. However, increasing the flow rate and activated carbon (AC) content of the flow-electrode could decrease the energy consumption of the electrode, and the energy consumed by the ion-exchange membranes (IEMs) and desalination chamber was the greatest. These two parts of energy consumption could not be significantly reduced by changing operational parameters. Thus, to further reduce the energy consumption, optimization of the FCDI equipment was carried out by adding titanium mesh to the flow electrodes and the desalination chamber of the FCDI cell. The results showed that the energy consumption of optimized FCDI decreased by 51.9% compared with the original FCDI. The long-term experiment using optimized FCDI showed good stability and repeatability.

Influence of ion exchange membrane arrangement on dual-channel flow electrode capacitive deionization: Theoretical analysis and experimentations

Flow electrode capacitive deionization (FCDI) has emerged as a viable technology for brackish water desalination. However, the mutual restriction between desalination rate and energy consumption is the current bottleneck hindering the widescale and practical application of FCDI. At this point, the relationship between the complex electrical double layer and electrodialysis mechanism is still unclear. Herein, we have constructed two kinds of dual-channel FCDI systems to investigate the influence of ion exchange membranes (IEMs) arrangement on desalination performance. The diffusion coefficient of chlorine is higher than that of sodium, resulting in the improved salt removal rate and current efficiency of dual-channel FCDI based on the NaCl electrolyte. In contrast, both systems performed identically using KCl as the majority salt in the feed stream due to the similar diffusion coefficients of both the cation and anion. The higher salt removal capability of dual-channel FCDI was achieved by (i) the thicker ion depletion layer of cation exchange membrane (CEM) enabling higher salt removal efficiency and (ii) the higher concentration of the ion enrichment layer accelerating the electro-adsorption of flow-electrodes. Both the numerical simulation and experimental results indicate that the composite mechanisms of dual-channel FCDI are beneficial to the excellent desalination performance and great energy efficiency.