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The prevalence of polyfluoroalkyls and perfluoroalkyls (PFAS) represents a significant challenge, and various treatment techniques have been employed with considerable success to eliminate PFAS from water, with the ultimate goal of ensuring safe disposal of wastewater. This paper first describes the most promising electrochemical oxidation (EO) technology and then analyses its basic principles. In addition, this paper reviews and discusses the current state of research and development in the field of electrode materials and electrochemical reactors. Furthermore, the influence of electrode materials and electrolyte types on the deterioration process is also investigated. The importance of electrode materials in ethylene oxide has been widely recognised, and therefore, the focus of current research is mainly on the development of innovative electrode materials, the design of superior electrode structures, and the improvement of efficient electrode preparation methods. In order to improve the degradation efficiency of PFOS in electrochemical systems, it is essential to study the oxidation mechanism of PFOS in the presence of ethylene oxide. Furthermore, the factors influencing the efficacy of PFAS treatment, including current density, energy consumption, initial concentration, and other parameters, are clearly delineated. In conclusion, this study offers a comprehensive overview of the potential for integrating EO technology with other water treatment technologies. The continuous development of electrode materials and the integration of other water treatment processes present a promising future for the widespread application of ethylene oxide technology. [ABSTRACT FROM AUTHOR]

In this study, the electrocoagulation (EC) treatment was used to minimize and separate pollutants from textile industrial wastewater (TIWW), including high color, chemical oxygen demand (COD), total organic carbon (TOC), and total dissolved solids (TDS). To enhance the EC treatment efficiency, a novel strategy has been followed in the study that involves thin‐film coating on 316 stainless steel (SS) electrodes with banana peel‐derived activated carbon (BPAC) by dip coating, spin coating, or spray coating. Among the different types of coating, thickness and contact angle measurements have elucidated that the spray coating of BPAC on SS electrode is the best tool with minimum thickness and contact angle. In this study, a bare SS electrode was used as the anode and a thin‐film spray‐coated BPAC on the SS electrode was used as the cathode. Moreover, optimization plays a key role in EC treatment process, where operating conditions such as a current density of 10 mA/cm2, contact time of 15 min, and a pH of 7 were fixed. As a result, the findings indicate comparatively high color removal of 98%, COD removal of 91%, TOC removal of 89.6%, and TDS removal of 68% are achieved with ease. Accordingly, in comparison with plain SS electrodes or dip‐ or spin‐coated BPAC on SS electrodes, spray‐coated BPAC on SS electrodes in EC treatment outperforms in removing high color, TOC, COD, and TDS. Overall, the study highlights the potential of EC treatment integrated with adsorption procedures for TIWW treatment. Particularly, the use of thin‐film spray‐coated BPAC on SS electrodes in the EC treatment process led to an effective and sustainable tool for treating and reuse of TIWW. It is due to its low operation and maintenance cost and studied in a short interval of time. Finally, the ultimate goal was firmly achieved in pilot‐scale studies by the safe discharge into the environment or reuse of treated textile wastewater. Thus, it is a promising alternative with an environmentally friendly footprint that could be easily implemented in any textile industry premises. Practitioner Points: Heavy metals, oils, facts, suspended solids, and other pollutants can be removed from industrial effluent by using electrocoagulation.The process is both cost‐effective and energy‐efficient, and it is easily integrated with other water treatment technologies.According to the findings of this study, minimum current density should be applied to BPAC–SS‐coated electrodes by DC power supplies to treat textile industry effluents at low operating costs.When compared with a plain SS electrode, the spray‐coated BPAC on SS electrode provides better performance in effluent treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Discussed MXene-based capacitive deionization (CDI) electrode optimization. • Presented forefront applications of MXene-based CDI across multiple fields. • Envisaged challenges and future directions for MXene-based CDI. MXene, hailed for its hydrophilicity, conductivity, and modifiable interlayer spacing, emerges as a frontrunner in capacitive deionization (CDI) electrode materials. Yet, pristine MXene grapples with suboptimal ion removal and stability. This review delves into inventive strategies to fortify MXene-based CDI electrodes, spotlighting their avant-garde applications in combatting ion pollution, reclaiming resources, softening water, and thwarting bacteria. Future prospects for MXene in CDI are also deliberated, aimed at igniting inspiration in the CDI arena. Some strategies proposed herein can be applied to other electrode materials in the CDI domain, thus fostering advancement across the entire spectrum of CDI electrode materials. [ABSTRACT FROM AUTHOR]

Faradic capacitive deionization (CDI) has emerged as an ideal candidate for developing effective water purification from low-concentration desalinated water. However, long-term desalination-stability CDI still faces the challenge in unstable electrode microstructure after hundreds of ion intercalations. Herein, ethylenediaminetetraacetic acid (EDTA)-modified Ti 3 C 2 T x (denoted as EDTA-Ti 3 C 2 T x) electrodes are proposed through intense chemical interactions without scarifying Ti 3 C 2 T x electronic conductivity, wherein the formed –COO-terminated bridge stabilizes Ti 3 C 2 T x interlayer spacing for strengthening long-term regeneration desalination. Simultaneously, abundant Na+ adsorption sites with highly hydrophilic surface in the binder-free high-conductivity EDTA-Ti 3 C 2 T x accelerated ion electro-sorption with efficient ion permeations. Importantly, in 500 mg L−1 NaCl solutions, EDTA-Ti 3 C 2 T x //activated carbon (AC) assembled CDI device delivered an extremely stable adsorption/desorption with salt adsorption-capacity (SAC) retention of 83 % after 500 cycles and a high desalination capacity of 51.0 mg g−1. In addition, the EDTA-Ti 3 C 2 T x presented without d -spacing changes after 100 cycle desalinations that was significantly different from structural collapse in Ti 3 C 2 T x. This study offers a new idea to overcome poor electrochemical desalination stability via organic molecules stabilized Ti 3 C 2 T x structure. [Display omitted] • The –COO-terminated bridge stabilizes Ti 3 C 2 T x interlayer spacing. • A high-conductivity binder-free EDTA-Ti 3 C 2 T x film electrode is proposed. • Abundant Na+ adsorption sites strengthen desalination capacity. • The EDTA-Ti 3 C 2 T x //AC CDI device exhibits an extremely stable SAC retention of 83 % after 500 cycles. [ABSTRACT FROM AUTHOR]

• Novel E-CDI with catalytic electrodes was developed for phosphonate degradation. • C-MCE with outstanding ORR performance improved the self-generation of H 2 O 2. • A-MCE provided an ideal platform for the reaction between ·OH and phosphonate. • E-CDI exhibited higher degradation efficiency and lower cost than traditional AOPs. Phosphonate is becoming a global interest and concern owing to its environment risk and potential value. Degradation of phosphonate into phosphate followed by the recovery is regarded as a promising strategy to control phosphonate pollution, relieve phosphorus crisis, and promote phosphorus cycle. Given these objectives, an anion-membrane-coated-electrode (A-MCE) doped with Fe-Co based carbon catalyst and cation-membrane-coated-electrode (C-MCE) doped with carbon-based catalyst were prepared as catalytic electrodes, and a novel electrocatalytic capacitive deionization (E-CDI) was developed. During charging process, phosphonate was enriched around A-MCE surface based on electrostatic attraction, ligand exchange, and hydrogen bond. Meanwhile, Fe2+ and Co2+ were self-oxidized into Fe3+ and Co3+, forming a complex with enriched phosphonate and enabling an intramolecular electron transfer process for phosphonate degradation. Additionally, benefiting from the stable dissolved oxygen and high oxygen reduction reaction activity of C-MCE, hydrogen peroxide accumulated in E-CDI (158 μM) and thus hydroxyl radicals (·OH) were generated by activation. E-CDI provided an ideal platform for the effective reaction between ·OH and phosphonate, avoiding the loss of ·OH and triggering selective degradation of most phosphonate. After charging for 70 min, approximately 89.9% of phosphonate was degraded into phosphate, and phosphate was subsequently adsorbed by A-MCE. Results also showed that phosphonate degradation was highly dependent on solution pH and voltage, and was insignificantly affected by electrolyte concentration. Compared to traditional advanced oxidation processes, E-CDI exhibited a higher degradation efficiency, lower cost, and less sensitive to co-existed ions in treating simulated wastewaters. Self-enhanced and selective degradation of phosphonate, and in-situ phosphate adsorption were simultaneously achieved for the first time by a E-CDI system, showing high promise in treating organic-containing saline wastewaters. [Display omitted] [ABSTRACT FROM AUTHOR]

A photoelectrochemical (PEC) oxidation and flow-electrode capacitive deionization (FCDI) dual system was explored for the effective treatment of brackish water. Two anodic electrodes with electrochemically self-doped TiO2 arrays (blue-mesh/ blue-plate TiO2 nanotube arrays (BM-TNA & BP-TNA)) were fabricated by annealing at 600 °C, and applied for the treatment of a water system. Specifically, the BM-TNA confirmed lower electrical resistance and superior performance under multiple light source (UV-A, -B, and -C). Furthermore, the system generated powerful oxidizing reactive oxygen species (ROS), which were assessed via degradation of eight organic pollutants: bisphenol-A, 4-chlorophenol, cimetidine, sulfamethoxazole, benzoic acid, phenol, nitrobenzene, and acetaminophen. Decomposition efficiency was stable throughout a wide range of pH, and durability of the BM-TNA electrode was demonstrated through long-term operation. Concurrently, optimization of the FCDI process via key operational parameters (electrode mass loading, and applied voltage) achieved superior desalination performance, and specific energy consumption (SEC). In particular, increased mass loading enhanced charge transportation through the formation of stable charge-percolation pathways, leading to improved solution conductance. Finally, the feasibility of the dual system (PEC-FCDI) was verified through complete degradation of the organic substrates and successful desalination of the brackish water. [ABSTRACT FROM AUTHOR]

[Display omitted] • The development history of capacitive deionization for defluorination is introduced. • Recent advances of electrode materials have been classified and reviewed. • Defluorination mechanisms have been summarized. • Challenges for engineering applications are presented. • Future perspectives on defluorination by capacitive deionization are provided. The combined need for advanced treatment of fluoridated water and low-energy technologies has inspired researchers to develop more efficient and green methods of fluoride removal. Capacitive deionization (CDI), a novel water treatment technology, has garnered significant attention in the defluorination field due to its exceptional ion selectivity. Recent decades, CDI has achieved remarkable advancements in electrode materials, F− storage mechanisms, and the potential for engineering applications in the realm of F− removal. However, there has been a lack of reviews that highlight design strategies for electrode materials in terms of fluoride ion properties in water and provide insights into key factors for designing CDI structures with excellent performance and promise for scale applications. Herein, starting from the background of fluorine pollution in surface water, and the selective removal of fluorine heavily relies on the crucial role played by electrode materials. Accordingly, all kinds of defluorinated electrode materials are reviewed. Secondly, the defluorination mechanism is summarized especially the distinctions among these processes. Additionally, the challenges existing in the promotion of CDI defluorination to large-scale applications are firstly analyzed in depth. Finally, future research opportunities and prospects by CDI for defluorination are proposed. In summary, CDI shows great potential for removing fluoride ions from water, offering a fresh approach to sustainable water resource management and environmental protection. [ABSTRACT FROM AUTHOR]

[Display omitted] • Defective MoS 2 electrode exhibited highly efficient and selective lead(II) adsorption. • Removal efficiency at initial concentration from 1 to 100 mg/L can reach ∼ 100 % • Adsorption capacity and removal efficiency were enhanced almost 8 folds after applying voltage. • Introduction of defects strengthened chemicalsorption and electrosorption. • A complete lead(II) desorption and reusability of electrodes can be achieved. Developing method for efficient lead(II) removal from aqueous solutions over a wide concentration range is urgent but challenging. In this work, defective molybdenum disulfide (MoS 2) was served as electrode coating to capture lead(II) over a wide range from aqueous solution via chemisorption and electrosorption coupling (CEC) process. The distinct adsorption behaviors of lead(II) on defective MoS 2 electrode were theoretically and experimentally investigated. In a wide concentration range (1 ∼ 100 mg/L), the removal efficiency of lead(II) from aqueous solutions can be close to ∼ 100 %. Adsorption capacities for lead(II) removal at initial concentration of 8.37 and 18.71 mg/L were 64.99 and 159.98 mg/g, respectively. After applying voltage, adsorption capacity and removal efficiency were enhanced almost 8 folds due to strengthened migration of ions, electrostatic interaction and electric double layer. Besides, lead(II) was completely desorbed from defective MoS 2 electrode within 60 min, and defective MoS 2 electrode by CEC process maintained excellent regeneration ability even after 10 cycles. Defective MoS 2 electrode has shown superior properties for lead(II) removal, such as (i) great specific capacitance and (ii) low charge transfer resistance toward the enhanced adsorption capacity and diffusion for lead(II) in the electrical double layer, compared with MoS 2. Extensive computations and characterizations of defective MoS 2 -lead(II) interaction demonstrated that the active unsaturated S sites were indispensable for lead(II) adsorption, which was beneficial for chemisorption. Based on the strong interaction with lead(II), defective MoS 2 electrode showed high-selectivity lead(II) adsorption with co-existence metal ions. Overall, defective MoS 2 as electrode coating by CEC has a great potential for the practical application in removing heavy metal ions from aquatic environment. [ABSTRACT FROM AUTHOR]

Efficient recovery of valuable resources from wastewater has emerged as a critical challenge in the era of carbon neutral society. Capacitive deionization (CDI) has been employed in electrochemical lithium recovery (ELR) processes based on selective Li+ intercalation to LiMn 2 O 4 (LMO). We herein propose a four-step constant voltage operation (forward/zero/reverse/zero) of bifunctional hybrid CDI to produce deionized water as well as Li+-rich concentrate within a cycle. Especially, selective Li+ enrichment was possible without influent replacement since adsorption of competing ions and liberation of Li+ could occur simultaneously. This unique performance was enabled by composite electrodes on capacitive activated carbon cloth (ACC) impregnated with redox-active materials; LMO@ACC and Ag@ACC. Together with material characterization and electroanalysis on the composite electrodes, deionization (step 1; forward voltage) and Li+ enrichment (step 3; reverse voltage) by assembled LMO@ACC//Ag@ACC cell were evaluated by single pass experiments with binary NaCl and LiCl solution (10 mM each). Besides, a multi-stage operation with internal recycle confirmed long-term stability and continuous increase of Li purity for practical implementation. The advanced bifunctional CDI (ELR coupled with water treatment) paved a way to advance the resource recycle from wastewater. [Display omitted] • Hybrid CDI electrodes were fabricated by impregnating LMO and Ag on ACC. • Four-step constant voltage operation with composite electrodes enabled selective desorption. • Bifunctional CDI-ELR system produced deionized water and Li+-rich brine within a cycle. • Extended electrochemical Li+ recovery was stable under variable feed compositions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Scaling up preparation of modified catalysts by direct calcination in air. • Both defects and oxygen-containing groups contribute to performance enhancement. • Electro-Fenton for high pollutant removal kinetics in a wide pH range. • Industrializable case of 30 g catalyst synthesis theoretically for 5.4 m2 electrode. • Lab-scale demonstration for wastewater treatment with capacity of 7.2 L/h. Electro-Fenton (EF) regarded as a green substitution to traditional homogeneous Fenton, produces highly oxidizing OH through in-situ H 2 O 2 electrosynthesis and electrochemical Fe2+ regeneration. One of obstacles that hinders translation of bench-scale EF performance to water treatment practices is the difficulty of scaling up catalyst/electrode preparation in low cost while producing high performance. Here we report scalable preparation of modified carbon catalysts for high-efficiency EF by directly calcinating commercial carbonaceous materials in air. The EF with modified carbon cathode shows high kinetics of 0.296–0.569 min−1 for levofloxacin removal in much wider pH range of 3.0–6.6 using less Fe dosage compared with homogeneous Fenton. This EF system can reduce chemical oxygen demand (COD) of coking wastewater from 312.0 to 99.5 mg L−1 to satisfy wastewater discharge standard in China while consuming low electricity of 1.8–4.9 kWh kg−1 COD−1. We demonstrated the scalability of this EF process by scaling up preparative throughput of catalyst (30 g that can be processed into electrodes with total working areas of 54000 cm2), enlarging electrode size (230 cm−2) and reactor volume with wastewater treatment capacity of 7.2 L/h. This scalability demonstration of EF technology shows the promising potential of achieving low-cost advanced wastewater treatment. [ABSTRACT FROM AUTHOR]

Pollution of water and limited availability of freshwater are the major environmental issues faced globally in the present era. Capacitive deionization, a potential water treatment technique based on electrochemistry, has gained huge recognition in the last decade owing to the facile ions' expulsion from sewage water, along with the benefits of being eco-friendly, reduced cost, decreased consumption of energy, and effortless renewal of electrode. Similarly, electrosorption emerged as a replacement technique to traditional adsorption techniques because of the generation of compound electrodes with flexible surface features, porous in nature, certainty, and the capability to execute electrochemical reactions. Extensive advancement has been witnessed in both capacitive deionization and electrosorption with their various electrodes. The scientific developments are assisted with distinct applications of these techniques. Thus, the current review paper has provided an elaborate description of the capacitive deionization and electrosorption methods with various electrode materials, highlighting polymer, membrane, and bio electrodes. The review paper has also delivered detailed explanations for the treatment of waste water which includes desalination, and expulsion of heavy metals and organic compounds, individually for capacitive deionization and electrosorption techniques. This review paper would be of great benefit in nurturing these technologies to evolve into a challenging alternative to get along with other water treatment problems. [Display omitted] • The versatile applications of capacitive deionization and electrosorption are discussed extensively. • Principles and mechanisms for both capacitive deionization and electrosorption are explained in detail. • Various electrode materials, along with bio electrodes, are given special emphasis. • The operational parameters for the effective functioning of capacitive deionization and electrosorption are detailed. • Challenges and future directions for empirical applications of capacitive deionization and electrosorption are explored. [ABSTRACT FROM AUTHOR]

[Display omitted] • Survey on biowaste material derived activated carbon (BMDAC) electrodes in CDI. • Applications of BMDAC electrodes for removal of pollutant ions are explained. • Systematic tabulation on BMDAC electrodes performance and parameters is presented. Capacitive deionization (CDI) is water desalination process used to remove pollutant ions and water purification. In present review contains current status biowaste material derived activated carbon (BMDAC) electrodes for pollutant ion removal using CDI. This review systematically present the fundamental about CDI, application of CDI, discusses the numerous BMDAC material, comparative tabulation on current status removal of pollutants ion using BMDAC electrodes by CDI and a future scope in present area. [ABSTRACT FROM AUTHOR]

[Display omitted] • The preparation process of the CDI electrode is simplified. • Laser-induced graphene (LIG) can be directly used as a CDI electrode. • LIG electrode is modified by one-step electrodeposition of Co 4 S 3. • The LIG6/Co 4 S 3 -15 presents a high adsorption capacity of 2702.79 mg g−1. • UO 2 2+ adsorption is attributed to the synergistic action of EDLs and pseudocapacitance. It has been proved that capacitive deionization (CDI) technology possesses a significant potential for uranium capture. However, the CDI performance has been limited by the complex preparation process of the electrodes and the poor adhesion between electrode materials and collectors. Here we combine the laser-induced graphene (LIG) and the electrodeposition to develop the LIG/cobalt sulfide (LIG/Co 4 S 3) electrodes with good adsorption performance. The obtained LIG6/Co 4 S 3 -15 electrode has both electrical double layers (EDLs) and pseudocapacitance properties, with a specific capacitance of 24.27 F g−1, which is 1.82 times higher than that of LIG6 (13.36 F g−1). The LIG6/Co 4 S 3 -15 electrode exhibited a high adsorption capacity of 2702.79 mg g−1. The advantages of this electrode preparation method are mainly attributed to the synergistic effect of the following aspects: (i) simplified graphene preparation by avoiding wet chemistry and post-treatment steps; (ii) simplified tedious electrode preparation such as electrode slurry distribution and sheet coating; (iii) the three-dimensional structure of LIG provides not only the conductive network but also the site for Co 4 S 3 nanosheet growth, thus avoiding nanosheet aggregation. The abundant pore structure of the conductive graphene substrate and the layered structure of the Co 4 S 3 nanosheets enable the LIG6/Co 4 S 3 -15 electrode with fast charge/ion transport, high hydrophilicity and superior pseudocapacitance, allowing uranyl (UO 2 2+) to be firstly electrosorbed, then physicochemically adsorbed, and finally electrocatalytically reduced/deposited onto the electrode. This study will offer a simple and environmentally friendly method for the synthesis of electrodes and provide a reference for the design of efficient electroadsorption materials. [ABSTRACT FROM AUTHOR]

The recently developed techniques for desalination and wastewater treatment are costly and unsustainable. Therefore, a cost-effective and sustainable approach is essential to achieve desalination through wastewater treatment. Capacitive deionization (CDI), an electrochemical desalination technology, has been developed as a novel water treatment technology with great potential. The electrode material is one of the key factors that promotes the development of CDI technology and broadens the scope of CDI applications. Biochar-based electrode materials have attracted increasing attention from researchers because of their advantages, such as environmentally friendly, economical, and renewable properties. This paper reviews the methods for preparing biochar-based electrode materials and elaborates on the mechanism of CDI ion storage. We then summarize the applications of CDI technology in water treatment, analyze the mechanism of pollutant removal and resource recovery, and discuss the applicability of different CDI configurations, including hybrid CDI systems. In addition, the paper notes that environmentally friendly green activators that facilitate the development of pore structure should be developed more often to avoid the adverse environmental impact. The development of ion-selective electrode materials should be enhanced and it is necessary to comprehensively assess the impact of heteroatoms on selective ion removal and CDI performance. Electrooxidation of organic pollutants should be further promoted to achieve organic degradation by extending to redox reactions. [Display omitted] • Activation, templating, heteroatom doping and metal oxide loading have been shown to be effective means of improving the electrochemical properties of biocarbon-based materials. • The ion storage mechanism of CDI involves EDL ion storage and Faraday pseudocapacitance storage. • The applicability of CDI technology in the field of water treatment has been proven. • Electrooxidation of organic pollutants should be further promoted to achieve simultaneous organic degradation by extending to redox reactions. [ABSTRACT FROM AUTHOR]

The unequal distribution of the water resources warrants a search for more energy efficient water treatment technologies. In this regard, capacitive deionization (CDI) could play a leading role particularly in the case of brackish water desalination. In this work, inexpensive materials that are commercially available were investigated for being used as electrodes in CDI. After physical and electrochemical evaluation, activated carbon (AC) demonstrated superior performance compared to the different fabrics tested. Hereafter, a factorial design of experiments was used to investigate the effect of cell potential, mass of AC ( m AC ), carbon black, and interparticle porosity on ion removal, charge efficiency and energy consumption. The results showed that neither carbon black nor macroporosity had a single effect on electrode performance. An interaction effect of macroporosity and m AC was found to be beneficial in terms of ion electrosorption for thick electrodes. An additional evaluation concerning the role of electrode thickness revealed that an increase in thickness translated into an increase in the total salt removed and a reduction in ion removal per mass of electrode. In addition, while electrosorption kinetics were found to be independent of the AC thickness, slow desorption kinetics were detected for the thicker electrodes. [ABSTRACT FROM AUTHOR]

• La-doping HAP (La-HAP) was synthesized by hydrothermal method in the presence of LaCl 3. • LaHAP/3D-rGO composites with various ratios were obtained by simple ultrasonic mixing. • 50LaHAP/3D-rGO possesses good conductivity and high hydrophilicity. • 50LaHAP/3D-rGO delivers F− adsorption of 1132 μmol g−1 with high selectivity by CDI. • The selective removal of F- in actual high-fluorine groundwater is achieved. Excessive fluoride in water is severely hazardous to environment and human health. It is of great significance to exploit effective methods for defluoridation from water. In this paper, lanthanum-doped hydroxyapatite modified three-dimensional reduced graphene oxide (LaHAP/3D-rGO) was successfully synthesized with LaHAP uniformly distributed on the 3D network. Electrochemical characterization demonstrates the improvement of the conductivity and ion diffusion rate after doping appropriate amount of LaHAP. With LaHAP/3D-rGO as positive electrode (activated carbon as negative electrode), the corresponding capacitive deionization (CDI) system is successfully applied for the selective adsorption of fluoride. With the appropriate LaHAP/3D-rGO ratio (50%), the obtained LaHAP/3D-rGO electrode achieves the optimal F− adsorption amount of 1132 μmol g−1. The corresponding CDI cell shows excellent selectivity and high cycle stability for adsorption of fluoride. When applied to the fluoride removal in the fluoride-containing groundwater through a 3-cell CDI stack, the electrode attains the high F− removal rate of 90.5%, with the effluent concentration down to 0.32 mg L−1, much lower than the permissible limit of World Health Organization. This LaHAP/3D-rGO based CDI system is much promising for water purification of the high F− groundwater. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Optimization for ultrasound-assisted fabrication of PVF/CNT electrodes was performed. • Ultrasonic treatment enhanced the stability of fabricated PVF/CNT electrodes. • Ultrasound had a pronounced effect on the surface morphology of PVF/CNT electrodes. • The Box–Behnken experimental design was applied to determine optimum active surface sites. • The efficiency of formate adsorption was improved by optimizing experimental conditions. The selective separation of ions is a major technological challenge having far-ranging impacts from product separation in electrochemical production of base chemicals from CO 2 to water purification. In recent years, ion-selective electrochemical systems leveraging redox-materials emerged as an attractive platform based on their reversibility and remarkable ion selectivity. In the present study, we present an ultrasound-intensified fabrication process for polyvinyl ferrocene (PVF)–functionalized electrodes in a carbon nanotube (CNT) matrix for selective electro-adsorption of formate ions. To this end, a response surface methodology involving the Box–Behnken design with three effective independent variables, namely, PVF to CNT ratio, sonication duration, and ultrasonic amplitude was applied to reach the maximum formate adsorption efficiency. The fabricated electrodes were characterized using cyclic voltammetry, X-ray diffraction, Raman spectroscopy, and scanning electron microscopy (SEM). SEM images revealed that an optimized ultrasonic amplitude and sonication time provided remarkable improvements in electrode morphology. Through a sedimentation study, we qualitatively demonstrate that the main optimized conditions improved PVF/CNT dispersion stability, consequently providing the highest number of active surface sites for adsorption and the highest adsorption efficiency. The highest percentage of active electrode surface sites and the maximum adsorption efficiency were 97.8 and 90.7% respectively at a PVF/CNT ratio of 3, ultrasonication time of one hour, and 50% ultrasonic amplitude. [ABSTRACT FROM AUTHOR]

The selective capacitive removal (SCR) of toxic but valued lead ions (Pb2+) from dilute wastewater is challenging for water purification since valueless and nontoxic alkali metal ions (like Na+) often dominate typical metal-containing industrial effluents. Herein, novel devices were assembled based on the half-wave rectified alternating current electrochemical (HWACE) method, and a self-support chitosan-modified carbon felt (Chitosan/ CF) electrode was constructed to boost the SCR of (Pb2+) from dilute wastewater. The characterization results of the Chitosan/CF electrodes indicated robust mechanical stability, good hydrophilia, and highly capacitive properties owing to the presence of abundant surface functional groups (-NH 2 , –OH). The assembled devices exhibited high extract performances under various conditions. Nearly complete removal of Pb2+ was achieved in a binary solution containing 50 ppm Pb2+ and 100 ppm Na+ at power supply parameters of the voltage of 5 V, frequency of 600 Hz, and flow rate of 8 mL/min within 24 h with a maximum removal efficiency reaching ∼99.4% and barely changed the concentration of Na+. Here, the fast growth of lead dendrites on the electrode surface was readily visible with naked eyes after 6 h. The characterization data of the Chitosan/CF electrode after HWACE extraction showed the presence of metallic lead (Pb0), suggesting further electroreduction of Pb2+ into neutral particles after adsorption on the electrode surface. The mechanism taking place at the cathode during the whole HWACE extraction process can best be described by Pb2+ reduction as the dominant process in early-stage and layered double hydroxide (LDH) precipitation at the late stage. The neutralized lead particles alleviated the Coulombic repulsion for sequent Pb2+ transformation, instantaneously leading to a nucleation mechanism for the continuous revival of lead particles. As a result, a rather high capacity >2500 mg/g was recorded, outperforming traditional SCR methods. Therefore, the constructed devices provided a new promising way for SCR of Pb2+ from typical metal-containing wastewater. In addition, the suggested process can be scalable and integrable with dilute wastewater treatment or full resource recovery sewage treatment plant. [Display omitted] [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is a kind of emerging desalination technology. The development of electrode materials with a high desalination rate and long life, which can be used in seawater/brine water desalination and the reduction of salty wastewater, is a research hotspot in the aspect of global water treatment. In this study, N-doped porous carbon was combined with activated carbon fibers by a green coating method to successfully prepared CDI electrode (NPC@ACF). The microstructure and electrode performance of NPC@ACF were characterized by different techniques. The specific surface area of NPC@ACF tested by BET was 1098 m2 g−1. The electrochemical performance of this material was studied, showing that the NPC@ACF electrode possesses a high specific capacitance of 268.90 F g−1. At the voltage of 1.2 V, the electrosorption capacity is 14.63 mg g−1, and the CDI desalination efficiency was increased by 39% and 63% compared with that of pure ACF or NPC, respectively. The NPC@ACF material has good recyclability showing a desalination efficiency retention rate of 27% after 50 cycles. With its recyclability, stability, and enhanced electrochemical characteristics, the NPC@ACF electrode has been proved to be an excellent electrode for CDI applications. [Display omitted] • A novel N-doped porous carbon and activated carbon fiber composites is designed. • Higher desalination efficiency is achieved in novel composites (NPC@ACF). • NPC@ACF has good electrochemical stability and recycling. • NPC@ACF has excellent desalination performance compared with reported values. [ABSTRACT FROM AUTHOR]

Abstract: Membrane-free electrodeionization (MFEDI) has been tested successfully for high purity water production in our previous work. However, in order to prevent the constant backward migration of cationic or anionic ions, to achieve equally effective regeneration for both the cationic and anionic resins, and to get neutral concentrate, the electrodes had to be reversed during regeneration. This not only complicated the regeneration process, but also decreased the water recovery and the electrode lifetime. In this work, we improved the resin layer structure and investigated the regeneration performance of MFEDI without electrode polarity reversal. A total of 30 operational cycles were examined. Effective regeneration was achieved. The effluent conductivity was 0.055–0.060μS/cm only; the average pH value of the concentrate was 7.2; the water recovery was 90%; and the energy consumption was 0.71kWh/m3 water. [Copyright &y& Elsevier]

A self-supported MoS 2 /CoS 2 @TiO 2 nanotube (TNT) hybrid electrode was fabricated by an in-situ hydrothermal process-assisted growth strategy, which achieved a significantly high gravimetric Na+ adsorption capacity and excellent regeneration performance. It also demonstrated amazing removal efficiencies close to 90% for various heavy metal ions (i.e., Fe3+, Cr3+, Cd2+, Pb2+, Cu2+ and Ni2+), revealing its great potential for wastewater purification. [Display omitted] • A self-supported MoS 2 /CoS 2 @TNT hybrid electrode was constructed. • The electrode achieved a gravimetric Na+ adsorption capacity of 44.22 mg g−1. • The electrode exhibited excellent regeneration performance and removal rates. • The electrode also realized removal efficiencies up to 90% for heavy metal ions. Recently, the rational design and construction of graphene-like layered transition-metal disulfides (TMDs) with chemical and physical superiorities to act as capacitive desalination (CDI) electrodes for water purification have attracted increasing interest worldwide. Herein, an advanced self-supported MoS 2 /CoS 2 @TiO 2 nanotube (TNT) hybrid electrode was grown on a TNT scaffold by a hydrothermal process-assisted in-situ growth strategy, and an asymmetric CDI cell was constructed with the as-fabricated MoS 2 /CoS 2 @TNT and commercial AC electrodes as cathode and anode, respectively. Benefiting from the effective structural feature (i.e., fully open nanosheet-assembled flowers and hierarchical pore alignment) and synergy effect of metal-like CoS 2 , state-of-the-art MoS 2 and TNTs with an efficient charge "superhighway", the MoS 2 /CoS 2 @TNT electrode achieved a significantly high gravimetric Na+ adsorption capacity of 44.22 mg g−1 in a 600 mg L−1 NaCl solution at 1.2 V. Moreover, the hybrid electrode possessed excellent regeneration performance with a capacity retention of nearly 100% even after 20 cycles. Most notably, such electrode also demonstrated amazing removal efficiencies close to 90% for various heavy metal ions (i.e., Fe3+, Cr3+, Cd2+, Pb2+, Cu2+ and Ni2+), revealing its great potential for wastewater purification. [ABSTRACT FROM AUTHOR]

Membrane capacitive deionization (MCDI) is a promising technology for desalination with the potential of lowering energy consumption and treatment cost. In this paper, batch mode experiments were carried out to evaluate the charge efficiency of the MCDI process. Specifically, charge efficiency is a very functional tool to examine the double layer structure inside of porous electrode. The results show that the charge efficiency in MCDI is a function of both cell voltage and solution conductivity. Specifically, it was found that the charge efficiency was proportional to cell voltage while inversely to solution conductivity. The maximum charge efficiency (0.55) in MCDI was far less than one, indicating the high transient resistivity between membrane and carbon electrodes. [ABSTRACT FROM AUTHOR]

Metal–organic-frameworks (MOFs) are emerging materials used in the environmental electrochemistry community for Faradaic and non-Faradaic water remediation technologies. It has been concluded that MOF-based materials show improvement in performance compared to traditional (non-)faradaic materials. In particular, this review outlines MOF synthesis and their application in the fields of electron- and photoelectron-Fenton degradation reactions, photoelectrocatalytic degradations, and capacitive deionization physical separations. This work overviews the main electrode materials used for the different environmental remediation processes, discusses the main performance enhancements achieved via the utilization of MOFs compared to traditional materials, and provides perspective and insights for the further development of the utilization of MOF-derived materials in electrified water treatment. [ABSTRACT FROM AUTHOR]

Here we report on a research effort towards full cell potential utilization during the elimination of organic pollutants under environmentally relevant conditions. Meropenem was selected as a representative recalcitrant antibiotic and a newly-developed Co and Bi co-doped TiO 2 nanotube array (Co/Bi/TiO 2 NTA) electrode was employed as both anode and cathode. While electrochemical reduction of Meropenem appeared to be much more energy efficient (0.042 kWh/m3) than electrochemical oxidation (0.813 kWh/m3) in synthetic electrolyte, the degradation was significantly inhibited in environmental matrices (secondary effluent/SE and RO concentrate) due to the competition and/or inhibition effects of other species present in the matrices as well as electrode fouling. Calcium carbonate and magnesium oxide were identified to be main mineral foulants. The elimination of Meropenem was then examined in coupled treatment schemes (e.g. sequential and simultaneous), taking advantages of the "self-regeneration" characteristic of TiO 2 NTA based electrodes through cathodic polarization. While a simultaneous oxidation & reduction with regular polarity switching seems to be a preferred treatment scheme especially for challenging matrices such as RO concentrate, the bipolar stability of the nanostructured electrode may limit the electrode lifetime. A hybrid electrolysis system coupling anodic oxidation of organic pollutants and cathodic hydrogen generation as a renewable energy source was also tested in a flow-through reactor, where consistent and steady treatment performance was demonstrated for a period of 3 days. We think the results obtained from this study have underlined the importance of matrix characteristics on the design and selection of electrochemical treatment processes. It also provides insights into future development of coupled anodic and cathodic processes for water purification. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Floriform WO 3 /C electrode were developed for electrosorption of U(VI) from water. • The charge/discharge process of WO 3 /C primarily belongs to capacitive controlled behavior. • WO 3 /C electrodes achieve a maximum U(VI) electrosorption capacity of 449.9 mg g−1 at 1.2 V. • Electrosorption of U(VI) is credited to synergistic effect of EDLs and pseudocapacitance from WO 3 /C. Decontamination and recovery of uranium(VI) [U(VI)] from radioactive wastewater is vital to sustainable nuclear power production and reclamation of radioactive waste. As a promising technology of water treatment, capacitive deionization for adsorption of U(VI) started to attract attention. Herein, for the first time, a floriform WO 3 /C composite was developed as a pseudocapacitive electrode material for electrosorption of U(VI) from water. The as-prepared WO 3 /C composite was constructed from dozens of 2D nanosheets with a thin amorphous carbon layer, resulting in uniform flower-like particles with hierarchical nanostructure and superior open pore network. The charge/discharge process of WO 3 /C was demonstrated as prominent capacitive controlled behavior by quantization of capacitance contributions. As a result, the WO 3 /C electrodes achieved a maximum U(VI) electrosorption capacity of 449.9 mg g−1 at 1.2 V and good cycling stability after consecutive adsorption-desorption, which is superior to the conventional physical adsorption processes. The superior CDI performance of the WO 3 /C electrode is credited to the synergistic effect of EDLs and pseudocapacitance based on the combination of WO 3 and carbon layer with hierarchical nanostructure. Overall, the facile preparation strategy, the superior electrosorption performances, and the high cycling stability, endow the floriform WO 3 /C electrodes to be a promising electrode material for electrosorption of U(VI) from wastewater. [ABSTRACT FROM AUTHOR]

Hierarchical porous carbon (HPC) was fabricated from rice husk biochar for electrosorption of ions in various water and wastewater treatment processes. • HPC was prepared from rice husk biochar using the hard template method. • The HPC was used as an electrode material in CDI. • The HPC had the preferred porous structures for capacitive electrosorption. • Hierarchical porous structure is a key to enhancing electrosorption performance. • HPC has great potential in the removal of inorganic ions. Hierarchical porous carbon (HPC) as an eco-friendly electrode material was fabricated from rice husk biochar using the hard template method for electrosorption of ions. The porous structure in HPC materials can be controlled by different activation times to optimize the material physicochemical and electrochemical properties. The HPC sample achieved a high specific surface area (1839 m2 g−1), large pore volume (1.21 cm3 g−1) and 58% mesopore to total pore volume ratio. The HPC electrode exhibited excellent electrochemical properties with a high specific capacitance of 120.5 F g−1 at 5 mV s−1 in a 1 M NaCl solution as well as good reversibility for capacitive charge storage. The large ion-accessible specific surface area, interconnected pore structure among micropores and mesopores, and large mesoporosity of the HPC electrode played crucial roles in the enhancement of the electrosorption performance. The HPC electrode exhibited a high electrosorption capacity of 8.11 mg g−1 and mean deionization rate of 0.92 mg g−1 min−1 for 20 mM NaCl in single-pass capacitive deionization. The associated charge efficiency and energy consumption were 48.1% and 0.064 kWh mol−1, respectively, indicating a low energy requirement of water desalination. Furthermore, the HPC electrode showed good regeneration ability in consecutive cycles for the removal of inorganic pollutants, i.e., NH 4 +, Mg2+ and Cu2+, with electrosorption capacities of 1.54, 1.53 and 0.52 mg g−1, respectively. Consequently, HPC from tailored activated rice husk biochar can provide a new opportunity to achieve high-performance electrosorption in various water and wastewater treatment processes. [ABSTRACT FROM AUTHOR]

Given the global impact of the water crisis, capacitive deionization (CDI) has attracted significant research interest as a promising water treatment technology. Recently, Multi-Channel Membrane CDI (MC-MCDI) has successfully been utilized to enhance the ion removal capacity by separating the electrode channels (side channels) from the feed stream (feed channel) to optimize the system's environment for the electrodes to perform desalination. However, one obstacle to MC-MCDI is the relatively complicated cell structure required to stack multiple units-cells. As such, the implementation of this process is limited to industrial applications. Therefore, the objectives of this study are to investigate an alternative approach and its associated parameters to expand the desalination capacity of MC-MCDI system by integrating porous carbon electrode stacks at the side channels. The MC-MCDI system with 4 pairs of carbon electrode stacks removed ~5.4 mg of NaCl and maintained the energy consumption (24 kT) and the charge efficiency close to unity. This result represents a threefold increase in the amount of ions removed, compared to a system with a single pair of carbon electrodes (~1.8 mg of NaCl). Moreover, by conducting several operation parameter studies, the MC-MCDI system with 4 pairs of porous carbon electrode stacks could be optimized at a high concentration of the supporting electrolyte (~500 mM NaCl), a faster flow rate of the feed channels, and a thinner feed channel thickness (3 mm) with high stability. In this respect, our study could advance new opportunities for the development of MC-MCDI in real-life CDI applications. Unlabelled Image • A novel strategy to expand the desalination capacity of MC-MCDI was proposed. • The desalination performance of MC-MCDI was successfully improved. • Electrode stacks led to a remarkable improvement of the desalination capacity. • Various parameters of MC-MCDI with highly stacked electrodes were examined. • This strategy opens opportunities to MC-MCDI in real CDI application. [ABSTRACT FROM AUTHOR]

Inability to remove biologically toxic and persistent contaminants is a critical issue in traditional water treatment processes. In this study, a novel 3D macroporous RuO 2 (3D-RuO 2) electrode with uniform and interconnected cavities has been fabricated via templated electrodeposition approach for treatment of persistent pyrazole. The physicochemical properties of the electrodes are characterized by means of SEM, BET, XRD, LSV and CV measurements. The results show that structural features of the 3D-RuO 2 play important roles in the electrocatalysis performance. Thanks to the abundant crystal defect sites, 3D-RuO 2 electrode possesses more mesopores within the skeleton, resulting in 17.9 and 2.2 times larger specific surface area compared to traditional flat thermal-deposited (TF-RuO 2) and electrodeposited RuO 2 (EF-RuO 2) respectively. At a current density of 5 mA cm−2, the pyrazole removal rate on 3D-RuO 2 is 1.7 times and 1.3 times that of TF-RuO 2 and EF-RuO 2. The energy consumption for 50% of pyrazole removal on 3D-RuO 2 is 0.05 kWh g−1pyrazole, much lower than that of TF-RuO 2 (0.11 kWh g−1pyrazole) and EF-RuO 2 (0.075 kWh g−1pyrazole). The improved removal performance of 3D-RuO 2 electrode is attributed to its strong electro-adsorption capacity (270.3 μg cm−2), leading to enhanced mass transfer of pollutants to the electrode surface. The mass transfer coefficient (κ m) is estimated as 2.4 × 10−6 m s−1 for 3D-RuO 2 , which is 3.9 and 2.3 times as much as that of TF-RuO 2 and EF-RuO 2. Finally, contribution of different electron transfer approaches to pyrazole degradation under anodic polarization was investigated by ROS scavenging experiments. Image 1 • The 3D porous RuO 2 electrode was prepared via templated electro-deposition method. • 3D RuO 2 is efficient for electrochemical the treatment of pyrazole effluent. • Roles of different degradation mechanisms of pyrazole on RuO 2 were studied. [ABSTRACT FROM AUTHOR]

Membrane capacitive deionization is considered as a promising technology for water treatment with their high efficiency, low capital cost, and environmental friendliness. However, the complex fabrication process of membrane capacitive deionization electrodes mainly hinders its viability in large‐scale applications. In this study, a facile and general method to prepare free‐standing electrodes for membrane capacitive deionization with an excellent electrosorption performance is presented. Electrospun nanofibers enclosing zinc‐based nanoparticles are fabricated as the templates. After pyrolysis, the nitrogen‐doped carbon nanofiber hybrids with high conductivity and a high surface area can be obtained readily. The carbon electrode material is able to achieve a salt adsorption capacity of 43.3 mg g−1 at 1.4 V in 1000 mg L−1 NaCl aqueous solution. Overall, the carbon nanofiber hybrids electrode prepared by electrospinning and pyrolysis shows a great potential in membrane capacitive deionization for industrial applications. A facial synthesis method to fabricate free‐standing electrodes for high‐performance membrane capacitive deionization is presented. Metal–organic framework nanoparticles are incorporated with electrospun nanofibers, which deliver high surface area and good electrical conductivity. The as‐prepared carbon nanofiber hybrid electrodes exhibit an enhanced salt adsorption capacity of 43.3 mg g−1 and a stable long‐term performance over 32 cycles. [ABSTRACT FROM AUTHOR]