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Chitosan nanosheets (NS) stabilized on poly (3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) was functionalized using Fe3O4 to capacitively remove chloride ions and toxic cadmium ions at optimized pH, concentration, and number of charging cycles. The synthesis procedure was investigated by Fourier transform infrared spectroscopy (FTIR), X-Ray Diffractometer (XRD), Transmission Electron Microscope (TEM), Scanning Electron Microscope – Energy Dispersive X-ray Spectroscopy (SEM-EDS), and Brunauer-Emmett-Teller (BET). The analyses confirms increase in surface area of the nanocomposite from 41 to 132 m2/g and a decrease in crystallinity from 75.3 to 66.9% after nanosheet formation. The highest sorption exchange capacity (SEC) for this work, 93% CdCO3 removal is achieved at 100 CDI cycles while 82% NaCl removal was achieved at 80 cycles. The SEC% increased with pH during Na ion deionization and decreased with pH during Cd removal. The works shows that chitosan is able to impart advanced structural properties to Fe3O4 and PEDOT and is able to reduce reverse migration of ions from electrodes to bulk solution, leading to higher SEC performance. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) are promising high‐performance capacitive deionization (CDI) materials. Strategies to optimize CDI performance of COFs focus largely on hybridization with conductive substrates, to improve their their intrinsically poor conductivity. A new structure‐function relationship between COFs and their substrates is proposed here based on substrate‐induced surface curvature. Graphene (zero‐curvature) and carbon nanotubes (CNT, curved) are selected as COF growthsubstrates to assess the effect of curvature engineering effect on CDI performance of TpPa‐SO3H‐COF. Ultrahigh ion (Na+) adsorption capacity (58.74 mg g−1) is achieved by CNT‐COF hybrid (cf. compared to graphene‐COF hybrid 34.20 mg g−1), demonstrating the significance of curvature engineering. Notably, the corresponding salt (NaCl) adsorption capacity of CNT‐COF hybrid reaches 149.25 mg g−1 in 1000 ppm at 1.2 V, representing state‐of‐the‐art CDI performance, and the highest value among organic CDI electrodes. X‐ray photoelectron spectroscopy and theoretical calculations subsequently reveal that substrate curvature can induce local strain, which regulates charge distribution within the COF skeleton, causing a lower binding energy state for Na+ adsorption. Electrochemical quartz crystal microbalance measurements revealed faster Na+ adsorption kinetics of CNT‐COF due to regulated charge distribution within COF skeleton induced by substrate curvature. This work gives new insight into design of COF materials based on curvature engineering. [ABSTRACT FROM AUTHOR]

Unraveling the fundamental mechanisms of sodium ion adsorption behavior is crucial for guiding the design of electrode materials and enhancing the performance of capacitive deionization systems. Herein, the optimization of sodium ion adsorption is systematically investigated through the robust d–d orbital interactions within zinc‐doped iron carbide, facilitated by a novel liquid nitrogen quenching treatment. Liquid nitrogen quenching treatment can enhance the coordination number, strengthen d–d orbital interactions, promote electron transfer, and shift the d‐band center of Fe closer to the Fermi level, thereby enhancing sodium ions adsorption energy. Consequently, the obtained electrode material achieves a superior gravimetric adsorption capacity of 121.1 mg g−1 and attractive cyclic durability. The adsorption capacity is highly competitive compared to the vast majority of related research works in the field of capacitive deionization. Furthermore, sodium ion adsorption/desorption mechanisms are substantiated through ex situ techniques, revealing dynamic atomic and electronic structure evolutions under operational conditions. This work demonstrates that optimizing sodium ion adsorption via robust d–d orbital modulation enabled by liquid nitrogen quenching treatment is an effective approach for developing efficient capacitive deionization electrode materials. [ABSTRACT FROM AUTHOR]

Water pollution by metals is increasing. An electrode material, copper hexacyanoferrate (CuHCF), for capacitive deionization (CDI) to remove Co2+ from wastewater was developed. The asymmetric electrode structure of the CDI overcomes the limitations of traditional activated carbon electrodes (low ion removal capacity, ion removal rate, and charge efficiency). The specific capacitance of the CuHCF electrode (216.7 F g−1) at 1 mV s−1 was higher than that of a traditional electrode (92.0 F g−1), and its deionization capacity was 156.85 mg g−1 in 50 mg L−1 aqueous Co2+ (charge efficiency = 68.4%). CuHCF is a high-performance electrode material for wastewater remediation. [ABSTRACT FROM AUTHOR]

The flake biochar electrode materials with fast ion transport function were prepared by KOH activation walnut shell used as raw material. The effects of carbonization temperature and KOH-to-biochar ratio were systematically evaluated using physicochemical characterization and electrochemical performance testing. The optimized walnut shell biochar (WSC800–2), produced at 800 °C with a KOH-to-biochar ration of 2:1, exhibited an exceptional specific surface area (2,287 m2 g−1), the highest porosity (0.824 cm3 g−1), and an excellent specific capacitance (369.51 F g−1, 10 mV s−1). Furthermore, in desalination experiments, WSC800–2 achieved a high salt adsorption capacity of 15.70 mg g−1 at 1.2 V, 500 mg l−1 NaCl solution. The electrode also exhibited outstanding cycling stability, retaining 97.0% of its performance after 10 adsorption/desorption cycles. These findings highlight the potential of walnut shell-derived biochar as an effective material for capacitive deionization and future desalination technologies. [ABSTRACT FROM AUTHOR]

Prussian blue analogues (PBAs) are a class of promising materials for capacitive deionization. However, the kinetic mismatch between their slow ion storage rate and the demand from short‐time desalination severely limits their desalination performance. Here, a group of structure‐tuneable Ni‐Mn PBAs have been developed by a combination strategy of surface‐protected chemical etching and Ostwald ripening to study their ion storage kinetics. Treating them as demos, the characterizations and investigations, e.g., in situ XRD in a three‐electrode system, dynamic impedance, finite element simulation, and DFT calculations etc., reveal that the slow ion diffusion caused by the severe agglomeration of the nanoparticles and the unsuitable lattice parameter controls the final desalination behavior. Therefore, the correspondingly optimized sample (HC‐t) possessing a microscale hollow structure, nanoscale shell thickness, and expanded lattice, displays a fast ion storage kinetics with the ratio of surface‐controlled current as high as 82% at a scan rate of 20 mV s−1. Consequently, it delivers an impressive desalination capacity of 120.8 mg g−1 (2.06 mmol g−1 Na+) with a fast average desalination rate of 0.25 mg g−1 s−1 (0.004 mmol g−1 s−1) at 1.2 V, competitive with those reported in the literature. Moreover, the elucidation of the structure‐performance correlation provides valuable insights for the development and design of next‐generation PBAs for capacitive deionization (CDI). [ABSTRACT FROM AUTHOR]

Exploring new carbon‐based electrode materials is quite necessary for enhancing capacitive deionization (CDI). Here, hollow mesoporous carbon spheres (HMCSs)/metal‐organic frameworks (MOFs) derived carbon materials (NC(M)/HMCSs and NC(M)@HMCSs) are successfully prepared by interface‐coating and space‐encapsulating design, respectively. The obtained NC(M)/HMCSs and NC(M)@HMCSs possess a hierarchical hollow nanoarchitecture with abundant nitrogen doping, high specific surface area, and abundant meso‐/microporous pores. These merits are conducive to rapid ion diffusion and charge transfer during the adsorption process. Compared to NC(M)/HMCSs, NC(M)@HMCSs exhibit superior electrochemical performance due to their better utilization of the internal space of hollow carbon, forming an interconnected 3D framework. In addition, the introduction of Ni ions is more conducive to the synergistic effect between ZIF(M)‐derived carbon and N‐doped carbon shell compared with other ions (Mn, Co, Cu ions). The resultant Ni‐1‐800‐based CDI device exhibits excellent salt adsorption capacity (SAC, 37.82 mg g−1) and good recyclability. This will provide a new direction for the MOF nanoparticle‐driven assembly strategy and the application of hierarchical hollow carbon nanoarchitecture to CDI. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) nonlayered metal compounds with porous structure show broad application prospects in electrochemistry‐related fields due to their abundant active sites, open ions/electrons diffusion channels, and faradaic reactions. However, scalable and universal synthesis of 2D porous compounds still remains challenging. Here, inspired by blowing gum, a metal‐organic gel (MOG) rapid redox transformation (MRRT) strategy is proposed for the mass production of a wide variety of 2D porous metal oxides. Adequate crosslinking degree of MOG precursor and its rapid redox with NO3− are critical for generating gas pressure from interior to exterior, thus blowing the MOG into 2D carbon nanosheets, which further act as self‐sacrifice template for formation of oxides with porous and ultrathin structure. The versatility of this strategy is demonstrated by the fabrication of 39 metal oxides, including 10 transition metal oxides, one II‐main group oxide, two III‐main group oxides, 22 perovskite oxides, four high‐entropy oxides. As an illustrative verification, the 2D transition metal oxides exhibit excellent capacitive deionization (CDI) performance. Moreover, the assembled CDI cell could act as desalting battery to supply electrical energy during electrode regeneration. This MRRT strategy offers opportunities for achieving universal synthesis of 2D porous oxides with nonlayered structures and studying their electrochemistry‐related applications. [ABSTRACT FROM AUTHOR]

Capacitive deionization techniques are of interest in water treatment technology due to their low cost, excellent efficiency, and environmental friendliness. Currently, metal–organic frameworks are highly impactful candidates for use as electrode materials in electrochemistry. It provides a large pore volume, good chemical stability, and a high specific surface area. Tuning metal–organic frameworks with carbon materials will have a good impact on electrode materials with increasing performance. This study shows a facile and effective strategy for arranging flow capacitive desalination technology for salt removal. The conducting network of Fe-MOF/CNTs provides rapid electron transport and offers a high diffusion length of ions. This material exhibited excellent desalination performance, with a high salt adsorption of 80.575 mg/g at 1.6 V at an initial NaCl concentration of 1000 mg/L. Overall, the facile method and fabrication strategy greatly advances water treatment applications. Highlights: Fe-MOF/CNT composites were obtained by a one-step hydrothermal process for improved CDI performance The strategy endowed the material with excellent porosity, and the presence of iron oxidation sites improved the overall conductivity of the electrode. • Fe-MOF/CNTs were used as flow electrodes for novel capacitive deionization • Fe-MOF/CNTs exhibited a high NaCl electrosorption capacity of 80.575 mg/g. Our strategy provides matching properties and an excellent combination of Fe-MOF and CNTs for improved CDI performance. [ABSTRACT FROM AUTHOR]

Capacitive deionization(CDI) is an emerging desalination method for removing charged ions dissolved in salt solution in recent years. It has attracted more and more attention due to its advantages of environmental friendliness, simple process, low energy consumption and low cost. The electrode material of CDI is the core of this technology. Metal-organic frameworks(MOFs) is a new type of CDI electrode material with large specific surface area, diverse structure and adjustable pore size. Firstly, CDI and MOFs were briefly introduced. Then, the research progress of seawater desalination based on MOFs material CDI was reviewed. It mainly focuses on four parts:MOFs derived carbon materials and modification, heteroatom doped MOFs derived carbon, MOFs derived carbon composites and MOFs composites. Finally, some shortcomings were put forward, and the future development direction was prospected. [ABSTRACT FROM AUTHOR]

This review comprehensively introduces and summarizes the roles of various pore structures and the research progress on different hierarchical porous carbon (HPC) materials used as capacitive deionization (CDI) electrodes・ The study also highlights the challenges faced by HPC as a CDI electrode material in practical applications, such as the limited development and utilization of environmentally friendly activators, the necessity for a deeper understanding of the structure-performance relationship between HPC and pseudocapacitive materials, and the lack of research on system design. Furthermore, it outlines the future development directions in the capacitive deionization field, offering valuable insights for researchers aiming to create environmentally friendly, low・carbon, and high-performance CDI electrode materials. [ABSTRACT FROM AUTHOR]

In this paper, a series of kelp-derived porous carbon (KPC) materials were prepared from kelp by using a pyrolysis-activation method, where KOH with a fixed ratio was applied as the activator under varying activation temperature. Eventually, the KPC-based capacitive deionization (CDI) system showed excellent desalination performance, and the desalination capacity of KPC with an activation temperature of 800 ​°C was highest, reaching 51.33 mg NaCl g−1 at 1.2 ​V. This work implies the trade-off effect of the activation temperature for the preparation and application of biomass-derived carbon materials, and provides some insights for carbon-based CDI materials. [ABSTRACT FROM AUTHOR]

Highlights: Steel tip arrays were used as current collectors to replace planar conductors. Optimal flow and electric fields reduced barriers for electron and ion transport. Desalination performance of flow-electrode capacitive deionization is enhanced by the tip-array current collectors. Low-electrode capacitive deionization (FCDI) is an emerging desalination technology with great potential for removal and/or recycling ions from a range of waters. However, it still suffers from inefficient charge transfer and ion transport kinetics due to weak turbulence and low electric intensity in flow electrodes, both restricted by the current collectors. Herein, a new tip-array current collector (designated as T-CC) was developed to replace the conventional planar current collectors, which intensifies both the charge transfer and ion transport significantly. The effects of tip arrays on flow and electric fields were studied by both computational simulations and electrochemical impedance spectroscopy, which revealed the reduction of ion transport barrier, charge transport barrier and internal resistance. With the voltage increased from 1.0 to 1.5 and 2.0 V, the T-CC-based FCDI system (T-FCDI) exhibited average salt removal rates (ASRR) of 0.18, 0.50, and 0.89 μmol cm−2 min−1, respectively, which are 1.82, 2.65, and 2.48 folds higher than that of the conventional serpentine current collectors, and 1.48, 1.67, and 1.49 folds higher than that of the planar current collectors. Meanwhile, with the solid content in flow electrodes increased from 1 to 5 wt%, the ASRR for T-FCDI increased from 0.29 to 0.50 μmol cm−2 min−1, which are 1.70 and 1.67 folds higher than that of the planar current collectors. Additionally, a salt removal efficiency of 99.89% was achieved with T-FCDI and the charge efficiency remained above 95% after 24 h of operation, thus showing its superior long-term stability. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have shown significant potential in hybrid capacitive deionization owing to their unique structure and adjustable pore size. However, their limited electronic conductivity and electrochemical stability hinder their practical application. In this study, we developed hierarchically structured Ni-MOF nanosheets interconnected by carbon nanotubes (Ni-MOF@CNT) through a one-pot hydrothermal reaction. By combining the porous structure of Ni-MOF with the synergistic effect of Ni2+ ions and CNTs, the Ni-MOF@CNT electrode with fast interfacial charge transfer demonstrates a high desalination capacity of 47.58 mg g–1 and excellent cycling stability. Additionally, the Ni-MOF@CNT electrode demonstrates a remarkable Li+ ion extraction capacity of 30.29 mg g–1. [ABSTRACT FROM AUTHOR]

The environmental toxicity caused by heavy metal ions is always taken seriously. Capacitive deionization (CDI), as an emerging and effective treatment method, is widely studied. Among them, the rational design and development of efficient electrodes based on high theoretical capacitance, high conductivity, and high stability have great prospects for CDI applications. In this study, a series of 2D titanium carbide oxide flakes (2D TCOs) are synthesized using a cation‐giving modulation strategy, and the interlayer spacing of materials is successfully controlled by confining cations (tetraalkylammonium hydroxides, TAAH) with different radii between layers. Interestingly, these TCOs exhibit widely varying electrochemical properties due to their different interlayer spacings. Among them, titanium carbide oxide flakes‐tetrapropylammonium hydroxide (TCOs‐TPAH) with the maximum interlayer spacing exhibits the best performance in sodium ion embedding and de‐embedding, with a capacity of 53.11 mg g−1. In addition, the capacitive removal efficiency of heavy metal ions (Fe3+, Cr3+, Cu2+, Cd2+, Co2+, Ni2+, and Pb2+) can reach over 97% within 2 h. This work presents a simple and creative strategy for the bottom‐up synthesis of oversized 2D nanomaterials, thus supporting the further development of high‐performance 2D materials in the fields of environmental and energy applications. [ABSTRACT FROM AUTHOR]

Copyright of Polymer Materials Science & Engineering is the property of Sichuan University, Polymer Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Zhejiang University (Science Edition) is the property of Journal of Zhejiang University (Science Edition) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Capacitive deionization is an efficient and cost-effective technology for ion removal from brackish water. Here, we demonstrate a sulfonatefunctionalized covalent organic framework as a novel faradaic cathode material for capacitive deionization applications. Due to its orderly arranged adsorption units in the covalent organic framework, the resulting covalent organic framework demonstrates a superior sodium cations removal capacity of 19.56 mg g-1 and a maximum desalination rate of 3.15 mg g-1 s-1 in a 500 ppm NaCl solution at 1.2 V. [ABSTRACT FROM AUTHOR]

Abstract Chitosan nanosheets (NS) stabilized on poly (3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) was functionalized using Fe3O4 to capacitively remove chloride ions and toxic cadmium ions at optimized pH, concentration, and number of charging cycles. The synthesis procedure was investigated by Fourier transform infrared spectroscopy (FTIR), X-Ray Diffractometer (XRD), Transmission Electron Microscope (TEM), Scanning Electron Microscope – Energy Dispersive X-ray Spectroscopy (SEM-EDS), and Brunauer-Emmett-Teller (BET). The analyses confirms increase in surface area of the nanocomposite from 41 to 132 m2/g and a decrease in crystallinity from 75.3 to 66.9% after nanosheet formation. The highest sorption exchange capacity (SEC) for this work, 93% CdCO3 removal is achieved at 100 CDI cycles while 82% NaCl removal was achieved at 80 cycles. The SEC% increased with pH during Na ion deionization and decreased with pH during Cd removal. The works shows that chitosan is able to impart advanced structural properties to Fe3O4 and PEDOT and is able to reduce reverse migration of ions from electrodes to bulk solution, leading to higher SEC performance.

Abstract Capacitive deionization techniques are of interest in water treatment technology due to their low cost, excellent efficiency, and environmental friendliness. Currently, metal–organic frameworks are highly impactful candidates for use as electrode materials in electrochemistry. It provides a large pore volume, good chemical stability, and a high specific surface area. Tuning metal–organic frameworks with carbon materials will have a good impact on electrode materials with increasing performance. This study shows a facile and effective strategy for arranging flow capacitive desalination technology for salt removal. The conducting network of Fe-MOF/CNTs provides rapid electron transport and offers a high diffusion length of ions. This material exhibited excellent desalination performance, with a high salt adsorption of 80.575 mg/g at 1.6 V at an initial NaCl concentration of 1000 mg/L. Overall, the facile method and fabrication strategy greatly advances water treatment applications.

Highlights Steel tip arrays were used as current collectors to replace planar conductors. Optimal flow and electric fields reduced barriers for electron and ion transport. Desalination performance of flow-electrode capacitive deionization is enhanced by the tip-array current collectors.

[Display omitted] Developing an eco-friendly and effective approach for preparing N, S co-doped hierarchical porous carbons (NSHPC) for capacitive deionization (CDI) is a huge task for desalination. Herein, NSHPC SKK with interconnected hierarchical pore structures, manufactured via self-activation/co-activation of sodium lignosulfonate (SLS) encapsulation using KNO 3 -KHCO 3 activators, inducing N, S co-doping. Different from NSHPC S and NSHPC SK , NSHPC SKK exhibits the highest specific surface area (S BET , 2264.67 m2/g) and a unique hierarchical pore structure (mesoporous volume/pore volume (V meso / V pore), 0.65). Small-angle X-ray scattering (SAXS) and scanning electron microscopy (SEM) both reveal the complex interconnected pore structure of NSHPC SKK. Regional Raman imaging conjugated with XPS reveals the presence of extensively distributed N, S co-doped defect structures, providing NSHPC SKK with excellent wettability and electrochemical performance. DFT calculations indicate that the N, S co-doping at the defect sites depicts excellent adsorption capability. Eventually, NSHPC SKK acquired an impressive salt adsorption capacity (SAC) of 20.5 mg/g and the highest average salt adsorption rate (ASAR) of 12.1 mg/g/min, indicating its superior desalting performance. In-situ Raman spectroscopy confirms NSHPC SKK 's rapid ion regeneration mechanism. The research introduces a span-new NSHPC synthesis strategy for fabricating advanced NSHPC with rapid desalination response for upgrading CDI desalination. [ABSTRACT FROM AUTHOR]

Objectives This study aims to introduce and evaluate the effectiveness of asymmetric membrane capacitive deionization (ACDI) in removing short-chain perfluoroalkyl substances (PFAS), specifically perfluorobutane sulfonic acid (PFBS), from aqueous solutions. This study offers important insights for the advancement of CDI technology in the sustainable treatment of industrial wastewater containing PFAS. Methods ACDI was employed by removing the anion exchange membrane from conventional membrane capacitive deionization system. The effect of key operational parameters such as voltage (0.5~1.2 V), initial concentration (50~500 mg/L), and flow rate (1~5 ml/min) on PFBS removal efficiency was systematically investigated. Additionally, PFBS removal performance in the presence of chloride ions was also investigated to determine competing ion effects. Results and Discussion The ACDI system significantly outperformed both CDI and MCDI, achieving a maximum deionization rate of 0.032 mg/g/s, compared to 0.012 mg/g/s for CDI and 0.01 mg/g/s for MCDI. Increasing the applied voltage from 0.5 V to 1.2 V enhanced the deionization rate, with the highest rate observed at 1.2 V. Higher initial PFBS concentrations also improved the deionization rate, increasing from 0.0009 mg/g/s at 50 mg/L to 0.032 mg/g/s at 500 mg/L. The optimal flow rate was found to be 2 ml/min, balancing ion contact time and throughput, resulting in the highest deionization rate. The presence of competing ions, such as chloride, reduced PFBS removal efficiency, as shown by the decrease in deionization rate when NaCl was added to the feed solution. Conclusion Overall, the ACDI system demonstrated superior deionization capacity and energy efficiency for PFBS removal, highlighting its potential as a sustainable and efficient technology for treating water contaminated with short-chain PFAS. Future research should address the challenges posed by competing ions in real-world wastewater to further optimize the ACDI system’s performance.

Capacitive deionization(CDI) is a new electrochemical nitrate removal technology, which has the advantages of simple structure and operation, low cost, low energy consumption and environmental friendliness. However, there are problems such as insufficient adsorption capacity, poor selectivity and limited desalting capacity. In view of the problems in CDI, scholars have carried out in-depth research on the structure optimization of CDI device and the modification of electrode materials. The research progress of CDI device structure optimization including membrane capacitance deion technology (MCDI), flow electrode capacitance deion technology (FCDI), capacitance-electrocatalytic coupling technology, etc was introduced. The research progress of electrode material modification was mainly introduced from the aspects of resin coating, surface modification, metal oxide/hydroxide doping, and structure regulation. The analysis showed that the CDI device structure optimization and electrode material modification improved the performance of the technology to remove nitrate and expanded the application range of the technology to remove nitrate, which made the CDI technology had a very broad application prospect in the removal of nitrate. Finally, some suggestions were proposed to provide reference for the further development of CDI from the aspects of improving the selectivity and removal rate, increasing the adsorption capacity of electrode, enhancing the sustainable utilization of electrode and practical application.

Abstract In this study, composite electrodes with metal–organic framework (MOF) for brackish water desalination via capacitive deionization (CDI) were developed. The electrodes contained activated carbon (AC), polyvinylidene fluoride (PVDF), and zinc-benzene tricarboxylic acid (Zn-BTC) MOF in varying proportions, improving their electrochemical performance. Among them, the E4 electrode with 6% Zn-BTC MOF exhibited the best performance in terms of CV and EIS analyses, with a specific capacity of 88 F g−1 and low ion charge transfer resistance of 4.9 Ω. The E4 electrode showed a 46.7% increase in specific capacitance compared to the E1 electrode, which did not include the MOF. Physicochemical analyses, including XRD, FTIR, FESEM, BET, EDS, elemental mapping, and contact angle measurements, verified the superior properties of the E4 electrode compared to E1, showcasing successful MOF synthesis, desirable pore size, elemental and particle-size distribution of materials, and the superior hydrophilicity enhancement. By evaluating salt removal capacity (SRC) in various setups using an initially 100.0 mg L−1 NaCl feed solution, the asymmetric arrangement of E1 and E4 electrodes outperformed symmetric arrangements, achieving a 21.1% increase in SRC to 6.3 mg g−1. This study demonstrates the potential of MOF-incorporated electrodes for efficient CDI desalination processes.

The use of graphene (GE) as a conductive additive for activated carbon (AC) electrode in capacitive deionization (CDI) has attracted much attention due to its high electrical conductivity. However, self-agglomeration by π–π interactions between individual GE sheets required the use of high content to ensure an efficient conductive network in the electrode, which limited its practical application. This work proposed an approach to reduce the GE content in the fabrication of biomass-based activated carbon electrode for CDI application. The stacking effect of GE sheets is inhibited when GE sheets functionalize with oxygen groups via acid treatment under ultrasonic condition. This helps to reduce GE content to less than 2 wt% in the fabrication of CDI electrodes. The electrode fabricated using 2 wt% treated GE (T-GE) achieved the superior capacitance of 54 F/g, twice that of the pristine AC. The desalination process using as-prepared electrodes was evaluated by batch-mode CDI system with the initial NaCl solution of 2000 ppm and 3000 ppm at various applied voltages. The AC/T-GE 2 % electrode showed excellent performance with a desalination capacity greater than 10 mg/g, and reached an adsorption rate of 1.93 mg/g.min in both solutions under an applied voltage 1.2 V. [ABSTRACT FROM AUTHOR]

MXenes is a new two-dimensional material which is gaining more attention in recent years for applications in catalysis, energy storage, and environmental remediation. In this study, MXene-Ti3C2 is synthesized from precursor MAX-Ti3AlC2 via etching method and then combined with coconutshell-derived activated carbon to provide a highly conductive and porous composite. The composite will be later employed as electrode materials in capacitive deionization for water desalination. The results have shown an increase in specific capacitance by 3.7 times in the composite (0.5 wt% MXene-Ti3C2) when compared with pure activated carbon. These promising results have proved the possibility to use MXenes-based composites for desalination and other treatment techniques for salted water. [ABSTRACT FROM AUTHOR]

Faradic-based capacitive deionization (FDI) has been widely acknowledged as one of the most promising desalination techniques to solve the freshwater crisis, yet was largely limited by heavily trailed development of its anode materials, which subsequently hindered its desalination performance in terms of both desalination capacity and stability. Herein, we developed a new type of anode material for FDI by coupling chloride-insertion FeOOH with carbon nanotubes (CNTs@FeOOH). The essence of this study lay in the composition of FeOOH with CNTs that could not only facilitate charge/electron transfer but also prevent structural aggregation. Consequently, the CNTs@FeOOH-based FDI system displays excellent desalination performance (desalination capacity: 50.36 mg g−1; desalination rate: 0.41 mg g−1 s−1) with robust long-term stability (13.86 % reduction over 80 cycles), which could motivate the future development of other highly-efficient desalination systems. • CNTs@FeOOH was integrated with anion-driven faradic capacitive deionization. • The aggregation between FeOOH was prevented by creating an interweaved 3D nanostructure. • CNTs@FeOOH FDI exhibited outstanding desalination performance. • CNTs@FeOOH was robust and exhibited long-term stability. [ABSTRACT FROM AUTHOR]

Although capacitive deionization (CDI) technology has been studied intensively for more than 20 years, its commercialization remains in the initial stage, which is partly caused by the insufficient knowledge exchange between academia and industry. This concept reviews multiple scaling‐up efforts in the CDI technology for treating real water streams, following a case‐by‐case fashion. While the cell architecture in pilot scales is limited to the membrane CDI, highlighting the necessary role of ion‐exchange components during scaling‐ups, different ways of electrode stacking, i. e. monopolar and bipolar, are available. The performance indicators of these CDI systems when treating real water streams are summarized to gain insights into industrial practices. Importantly, key discrepancies in cell components and performances between pilot‐scale and lab‐scale studies are emphasized. The main challenges in large‐scale CDI systems for industrial purposes are discussed, providing hints for a better integration of research and applications. [ABSTRACT FROM AUTHOR]

Prussian blue analogs (PBAs) are considered as one of the most potential electrode materials in capacitive deionization (CDI) due to their unique 3D framework structure. However, their practical applications suffer from low desalination capacity and poor cyclic stability. Here, an entropy engineering strategy is proposed that incorporates high‐entropy (HE) concept into PBAs to address the unfavorable multistage phase transitions during CDI desalination. By introducing five or more metals, which share N coordination site, high‐entropy hexacyanoferrate (HE‐HCF) is constructed, thereby increasing the configurational entropy of the system to above 1.5R and placing it into the high‐entropy category. As a result, the developed HE‐HCF demonstrates remarkable cycling performance, with a capacity retention rate of over 97% after undergoing 350 ultralong‐life cycles of adsorption/desorption. Additionally, it exhibits a high desalination capacity of 77.24 mg g−1 at 1.2 V. Structural characterization and theoretical calculation reveal that high configurational entropy not only helps to restrain phase transition and strengthen structural stability, but also optimizes Na+ ions diffusion path and energy barrier, accelerates reaction kinetics and thus improves performance. This research introduces a new approach for designing electrodes with high performance, low cost, and long‐lasting durability for capacitive deionization applications. [ABSTRACT FROM AUTHOR]

Silver (Ag) is deemed a promising anode material for capacitive deionization (CDI) due to its high theoretical capacity and efficient selectivity to Cl−. However, the strong volume change during the conversion reaction significantly undermines the cycling performance of the Ag electrode. Additionally, achieving well‐dispersed Ag in the active matrix is challenging, as Ag electrodes prepared by conventional thermal reduction tend to agglomerate. Herein, the organic linker confinement strategy is proposed, applying metal–organic framework (MOF) chemistry between Ag nodes and organic ligands to construct Ag‐based MOF. The uniform dispersion of Ag at the molecular level, confined in the organic matrix, efficiently enhances the utilization of active sites, and strengthens the interfacial stability of Ag. Consequently, the Ag‐MOF for the CDI anode exhibits an excellent Cl− removal capacity of 121.52 mg g−1 at 20 mA g−1 in 500 mg L−1 NaCl solution, and a high Ag utilization rate of 60.54%. After 100 cycles, a capacity retention of 96.93% is achieved. Furthermore, the Cl− capture mechanism of Ag‐MOF is elucidated through density functional theory (DFT) calculations, ex situ XRD, ex situ Raman and XPS. This ingenious electrode design can offer valuable insights for the development of high‐performance conversion electrodes for CDI applications. [ABSTRACT FROM AUTHOR]

Suffering from the susceptibility to decomposition, the potential electrochemical application of FeOCl has greatly been hindered. The rational design of the soft‐hard material interface can effectively address the challenge of stress concentration and thus decomposition that may occur in the electrodes during charging and discharging. Herein, interlayer structure manipulation of FeOCl/MXene using soft‐hard interface design method were conducted for electrochemical dechlorination. FeOCl was encapsulated in Ti3C2Tx MXene nanosheets by electrostatic self‐assembly layer by layer to form a soft‐hard mechanical hierarchical structure, in which Ti3C2Tx was used as flexible buffer layers to relieve the huge volume change of FeOCl during Cl− intercalation/deintercalation and constructed a conductive network for fast charge transfer. The CDI dechlorination system of FeOCl/Ti3C2Tx delivered outstanding Cl− adsorption capacity (158.47 ± 6.98 mg g−1), rate (6.07 ± 0.35 mg g−1 min−1), and stability (over 94.49 % in 30 cycles), and achieved considerable energy recovery (21.14 ± 0.25 %). The superior dechlorination performance was proved to originate from the Fe2+/Fe3+ topochemical transformation and the deformation constraint effect of Ti3C2Tx on FeOCl. Our interfacial design strategy enables a hard‐to‐soft integration capacity, which can serve as a universal technology for solving the traditional problem of electrode volume expansion. [ABSTRACT FROM AUTHOR]

The basic principles of hybrid capacitive deionization (HCDI) and its development history are introduced. From the analysis of the principle and current situation of HCDI, it is concluded that the key of the research of HCDI lies in the electrode material. Thus, the current research status of faradic electrode materials including transition metal oxides, poly anionic compounds, and prussian blue analogs is systematically reviewed. Based on the above analysis, it is suggested that the current research focus is still to im-prove the desalination ability and cycling stability of electrode materials. Finally, the further development direction of HCDI is proposed and suggested. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Excessive phosphorus discharge causes water eutrophication and disturbs the homeostasis of aquatic ecosystems. Capacitive deionization (CDI) has been proven to be a more energy-efficient and environmentally friendly technology for removing phosphorus. Raw carbon (Raw C) electrodes are widely used in CDI. However, the phosphorus removal capacity of most unmodified Raw C still needs to be enhanced. Therefore, the Fe, N-co-doped carbon prepared in this study was expected to further improve the phosphorus removal performance. Herein, the optimal electrode with 5% Fe (FeNC) had an approximately 2.7 times higher adsorption capacity than Raw C. At a low concentration (5 mg P/L), FeNC exhibited a high maximum removal capacity of 4.28 mg P/g. Under reversed voltage, the phosphorus was easily desorbed by deionized water. Ion competition studies showed that coexisting ions adversely affected phosphorus adsorption onto FeNC in the order SO42- > NO3- > Cl-. Furthermore, the energy consumption of FeNC was calculated to be as low as 0.0069 kWh/g P and 0.023 kWh/m3 water under 1.2 V. More importantly, phosphorus removal by FeNC during CDI was demonstrated in simulated natural water from the Jinjiang River (Chengdu, China). This study indicated that FeNC is expected to be a potential electrode for CDI dephosphorization. [ABSTRACT FROM AUTHOR]

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Capacitive deionization (CDI) is an emerging technique of seawater desalination technology with high efficiency and low energy consumption. Prussian blue (PB) is considered to be an excellent candidate for CDI intercalation electrode materials due to its spacious three-dimensional ion diffusion channels and available low-cost raw materials. However, the agglomerate tendency and inferior electronic conductivity of PB are the main factors which lead to lower capacity and poor cycling stability. Herein, a Prussian blue nanoparticle/carbon nanofiber (PB/CNF) composite material was synthesized by electrospinning and coprecipitation for capacitive deionization. The conductive CNFs bridged the PB nanoparticles with a size of ca. 50 nm to form a 3D conductive network structure, which can boost the diffusion kinetics of salt ions and electrons simultaneously in the PB/CNF electrode. The ion storage process by the combination of capacitance-controlled and diffusion-controlled behaviors allows the PB/CNF-5 composite to achieve a salt adsorption capacity (SAC) of 51.81 mg g–1 in a 500 mg L–1 NaCl solution at 1.4 V, and it has excellent cycle stability for 80 cycles. Remarkably, it also shows an excellent salt adsorption performance of 97.35 mg g–1 in a 3000 mg L–1 NaCl solution. Overall, the strategy of antiaggregation and enhanced electronic conductivity not only improved the desalination performance of PB nanoparticles but also provided a technical guideline for nanometer-sized materials and helped to facilitate better CDI electrode design. [ABSTRACT FROM AUTHOR]

The continuous population growth and drying up the freshwater reservoirs around the world are increasing the demand for fresh water. Therefore, there is an urgent need to explore newer technologies able to purify water on large scales for human usage. Capacitive deionization is one of the most promising approaches to generate fresh water by the removal of salt ions from brackish water. In this work, we prepared three different capacitive deionization electrodes using carbonized palm tree fronds (PFC). These PFC activation was achieved using CO2 at 900°C. To generate the deionization electrodes, PFC activated carbon was combined with either polyaniline (PANI), MnO2, or both (PFC‐PANI, PFC‐MnO2, and PFC‐MnO2‐PANI). The MnO2 and PANI provided additional functionality and enhanced electrical conductivity, which resulted in much higher Na+ and Cl− ions adsorption. The BET surface area of PFC‐MnO2‐PANI was estimated to be 208.56 m2/g, which is approximately three times that of PCF‐PANI and PFC‐MnO2 alone. The morphological analysis showed that the PANI and MnO2 nanorods were well dispersed throughout the PFC network. Although PANI and MnO2 is largely embedded inside the PFC network, some remnants are visible on the surface of the electrodes. The cyclic voltammetry (CV) curves showed capacitive behavior of all electrodes in which PFC‐MnO2‐PANI showed highest specific capacitance of 84 F/g, while the PFC‐MnO2 and PFC‐PANI showed 42 and 43 F/g, respectively. Owing to its enhanced functionality and CV characteristics, the PFC‐MnO2‐PANI showed maximum salt adsorption capacity of 10.5 mg/g in contrast to 3.72 and 5.64 mg/g for PFC‐MnO2 and PFC‐PANI, respectively. Moreover, the measured contact angle for PFC‐MnO2‐PANI was ~51°, which indicates the hydrophilic nature of electrode that improved ions adsorption. Practitioner Points: Date tree fronds were converted into mesopores carbon using CO2 as activation agent.Three composites were prepared with PANI, MnO2, and date palm fronds activated carbon (PFC‐MnO2, PFC‐MnO2‐PANI, and PFC‐PANI).Surface area, pore profile, surface morphology, electrochemical behavior, desalination performance, and hydrophilicity of all the electrodes were investigated.The PFC‐MnO2‐PANI showed maximum salt adsorption capacity of 10.5 mg/g in contrast to 3.72 and 5.64 mg/g for PFC‐MnO2 and PFC‐PANI, respectively. [ABSTRACT FROM AUTHOR]

Wood-based N, P co-doped graphene oxide modified foam (N, P-GCF) was prepared by liquefaction, resinization, foaming, carbonization and CO2 activation by liquefaction, resinization, foaming, carbonization and CO2 activation. The surface morphology, crystal structure, chemical properties and hydrophilic properties of N, P-GCF were analyzed by SEM, XRD, Raman, XPS and contact angle measuring instrument, and the effects of N, P-GCF on pore structure, electrochemical properties and capacitance deionization (CDI) were explored by changing the addition amount of NH4H2PO4. The results showed that after GOs modification and NH4H2PO4 doping, the pore size decreases and the disorder increases. N, P-GCF has a hierarchical pore structure. When the doping amount of NH4H2PO4 was 2 g, it had the highest specific surface area of 2684.11 m²/g, total pore volume of 1.42 cm³/g and mesoporosity of 49.45%, and the mass fractions of N and P were 2.48% and 3.46%, respectively. N elements mainly exist in the form of N-5, N-6 and N-X, and P elements are mainly P-C and P-N. Compared with CF, N, P-GCF2.0 has excellent wettability and mechanical properties. In the three-electrode system of 1 mol·L NaCl electrolyte, the specific capacitance of N, P-GCF2.0 is 256.48 F/g at a current density of 1 A/g, and the specific capacitance retention rate is 72.51% when the current density increases to 15 A/g. Under the initial NaCl solution of 500 mg/L and the working voltage of 1.2 V, N, P-GCF2.0 had the best desalination capacity (29.97 mg/g) and salt adsorption rate (1.84 mg/(g·min)), and the retention rate of desalination capacity was 90.12% after 10 cycles, indicating good cycling stability. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) has attracted significant attention as a water treatment technology owing to its low cost, high efficiency, and eco‐friendliness. However, the unsatisfactory desalination performance of traditional electrode materials hinders the development of CDI. Herein, 1T‐MoS2/C hybrid microspheres are successfully fabricated through confinement and phase engineering strategies. The confinement effect of porous hollow carbon microspheres reduces the overgrowth and agglomeration of MoS2 nanosheets, which is beneficial for exposing more active sites and enhancing stability. Meanwhile, the 1T phase MoS2 displays high intrinsic conductivity and large interlayer spacing, which is conducive to rapid insertion/extraction of Na+. Consequently, 1T‐MoS2/C hybrid becomes a prospect electrode material for CDI, which showcases outstanding desalination capacity (48.1 mg/g at 1.2 V), eminent desalination rate as well as exceptional stability. Moreover, the desalination mechanisms are clarified through various characterizations and density functional theory calculations. This study provides new perspectives on designing high‐performance MoS2‐based CDI electrode materials. [ABSTRACT FROM AUTHOR]

Abstract Exploring new carbon‐based electrode materials is quite necessary for enhancing capacitive deionization (CDI). Here, hollow mesoporous carbon spheres (HMCSs)/metal‐organic frameworks (MOFs) derived carbon materials (NC(M)/HMCSs and NC(M)@HMCSs) are successfully prepared by interface‐coating and space‐encapsulating design, respectively. The obtained NC(M)/HMCSs and NC(M)@HMCSs possess a hierarchical hollow nanoarchitecture with abundant nitrogen doping, high specific surface area, and abundant meso‐/microporous pores. These merits are conducive to rapid ion diffusion and charge transfer during the adsorption process. Compared to NC(M)/HMCSs, NC(M)@HMCSs exhibit superior electrochemical performance due to their better utilization of the internal space of hollow carbon, forming an interconnected 3D framework. In addition, the introduction of Ni ions is more conducive to the synergistic effect between ZIF(M)‐derived carbon and N‐doped carbon shell compared with other ions (Mn, Co, Cu ions). The resultant Ni‐1‐800‐based CDI device exhibits excellent salt adsorption capacity (SAC, 37.82 mg g−1) and good recyclability. This will provide a new direction for the MOF nanoparticle‐driven assembly strategy and the application of hierarchical hollow carbon nanoarchitecture to CDI.

Highlights Through facial basicity adjustment, kinetically favorable ZnxNi1-xO@CF electrode was formed with a high density hierarchical structure and three dimensional open pores. The optimal Zn-doping ratio in ZnxNi1-xO@CF has excellent sodium storage and desalination performance (128.9 mg g-1). The mechanism of Na+ intercalation process was studied by electrochemical quartz crystal microbalance with dissipation monitoring in situ test and the activation mechanism of redox-inert Zn-doping on electrode materials was reported.

Novel composite electrodes were developed for application in membrane capacitive deionization (MCDI). Activated carbon (AC) was dispersed in a solution of poly(vinyl alcohol) (PVA) mixed with polyacrylic acid (PAA) or poly dimethyl diallyl ammonium chloride (PDMDAAC), and cast onto the surface of an AC‐based modified graphite electrode, prepared by phase inversion, to form a composite membrane further cross‐linked with glutaraldehyde (GA). The effect of the cross‐linking on the chemical structure of the PVA‐based membranes was determined by attenuated total reflectance Fourier‐transform infrared (ATR‐FTIR) spectroscopy. Cyclic voltammetry was conducted to examine the specific capacitance of the composite electrodes. Desalination experiments were then performed with MCDI unit cells to study the effect of cross‐linking on the desalination efficiency. It was proved that after optimization, the synthesized composite electrodes exhibited one and a half times higher NaCl removal capacity and three times higher adsorption rate as compared to that of a conventional CDI cell using commercial ion exchange membranes (IEMs) with almost the same energy consumption. The enhanced desalination performance was attributed to the optimized properties of the selected polymers and the improved adhesion of IEMs to the electrodes. This research paves the way for the application of new materials in MCDI processes for improved water desalination. [ABSTRACT FROM AUTHOR]

With the continuous development of global industry and the increasing demand for lithium resources, recycling valuable lithium from industrial solid waste is necessary for sustainable development and environmental friendliness. Herein, we employed ion imprinting and capacitive deionization to prepare a new electrode material for lithium-ion selective recovery. The material morphology and structure were characterized using scanning electron microscopy, Fourier-transform infrared spectroscopy, and other characterization methods, and the adsorption mechanism and water clusters were correlated using the density functional theory. The electrode material exhibited a maximum adsorption capacity of 36.94 mg/g at a Li+ concentration of 600 mg/L. The selective separation factors for Na+, K+, Mg2+, and Al3+ in complex solution environments were 2.07, 9.82, 1.80, and 8.45, respectively. After undergoing five regeneration cycles, the material retained 91.81% of the initial Li+ adsorption capacity. Meanwhile, the electrochemical adsorption capacity for Li+ was more than twice the corresponding conventional physical adsorption capacity because electrochemical adsorption provides the energy needed for deprotonation, enabling exposure of the cavities of the crown ether molecules to enrich the active sites. The proposed environment-friendly separation approach offers excellent selectivity for Li+ recovery and addresses the growing demand for Li+ resources. [ABSTRACT FROM AUTHOR]

[Display omitted] • An efficient CuHCF/C electrode was prepared for Cu2+ removal by CDI. • CuHCF/C achieved high Cu2+ adsorption capacity of 134.47 mg g−1 at low applied voltage of 0.8 V. • CuHCF/C manifested excellent Cu2+ selectivity in multi-ion coexisting solution. • The mechanism of removing Cu2+ by Faradaic pseudocapacitance was explained. The efficient capture of copper ions (Cu2+) in wastewater has dual significance in pollution control and resource recovery. Prussian blue analog (PBA)-based pseudocapacitive materials with open frameworks and abundant metal sites have attracted considerable attention as capacitive deionization (CDI) electrodes for copper removal. In this study, the efficiency of copper hexacyanoferrate (CuHCF) as CDI electrode for Cu2+ treating was evaluated for the first time upon the successful synthesis of copper hexacyanoferrate/carbon sheet combination (CuHCF/C) by introducing carbon sheet as conductive substrate. CuHCF/C exhibited significant pseudocapacitance and high specific capacitance (52.92 F g−1) through the intercalation, deintercalation, and coupling of Cu+/Cu2+ and Fe2+/Fe3+ redox pairs. At 0.8 an applied voltage and CuSO 4 feed liquid concentration of 100 mg L−1, the salt adsorption capacity was 134.47 mg g−1 higher than those of most reported electrodes. Moreover, CuHCF/C demonstrated excellent Cu2+ selectivity in multi-ion coexisting solutions and in actual wastewater experiments. Density functional theory (DFT) calculations were employed to elucidate the mechanism. This study not only reveals the essence of Cu2+ deionization by PBAs pseudocapacitance with promising potential applications but also provides a new strategy for selecting efficient CDI electrodes for Cu2+ removal. [ABSTRACT FROM AUTHOR]