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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]

[Display omitted] The utilization of Na 2 MnSiO 4 as a Faraday electrode in hybrid capacitive deionization (HCDI) is investigated to achieve efficient desalination. The Na 2 MnSiO 4 /C (NMSO) materials were fabricated via a simple sol–gel method, in which the synthesis process was modulated by adjusting the volume ratio of ethanol to water. When maintaining the volume ratio of water to ethanol at 3:1, the resultant NMSO-3/1 exhibited expected salt adsorption capacity of 31.06 mg g−1 and salt adsorption rate of 20.43 mg g−1 min−1. This distinguished desalination performance was mainly attributed to its inherent multiple redox pairs, as well as the integration of ethanol, which enhanced both specific capacitance and hydrophilicity of the material. This study opens a new perspective for the development of highly efficient materials in HCDI. [ABSTRACT FROM AUTHOR]

Many studies have shown that capacitance deionization (CDI) has great potential in salt‐water treatment, one of the issues of great concern in many countries, especially Vietnam. The electrode material in CDI is one of the essential factors contributing to the desalination efficiency of this technology, so it is of research interest. In this study, TiO2 and TiO2/carbon nanotubes (CNTs) were synthesized from the sol‐gel process and utilized as an electrode for desalination. The composite materials were intensively characterized by X‐ray diffraction, Raman spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, Brunauer–Emmett–Teller and thermal analysis. The electrochemical properties were investigated using electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge/discharge. The fabricated TiO2/CNTs nanocomposite electrode consisting of 1% CNTs (electrode T1) exhibited remarkable capacitance, conductivity, and durability; thus, it was employed as an electrode for desalination. With this electrode T1, the maximum salt adsorption capacity of 17.5 mg g−1, together with the highest charge efficiency of 90%, was achieved. Therefore, TiO2/CNTs can be considered a suitable electrode candidate for CDI technology. [ABSTRACT FROM AUTHOR]

A low-waste combined technology for water softening, desalination, and deionization is proposed. The low-waste nature of the method is achieved through H-cationization of water using carboxylic polyacrylic ion exchange resin, followed by its deionization via reverse osmosis. If the requirements for desalinated water are high, such as when purified liquid is used for feeding supercritical pressure once-through boilers (SPB), it is additionally treated using ion exchange. The preconcentrate from reverse osmosis is processed through electrodialysis or electrolysis to yield acidic and alkaline solutions. These solutions are then used in conjunction with spent regeneration solutions from deep deionization ion exchange filters to regenerate the filter containing carboxylic polyacrylic ion exchange resin. The paper outlines the advantages of carboxylic cation exchange resins compared to sulfonated cation exchangers. A two-chamber H+,Na+-cation exchange filter operation circuit is proposed. Recirculation of the acidic portion of the spent regeneration solution from the BC storage reservoir through the H+Na+-cation exchange filter is planned to maximize the recovery of the cation exchange resin's working capacity. The specifics of regenerating carboxylic cation exchange resin with acid solution in a fluidized bed mode are presented. The acidic solution storage tank should be constructed as a reservoir with a conical bottom and a cylindrical upper part. Such tank design enables its use as a gypsum particle crystallizer and settler. This circuit of separate water H+,Na+-cationization with a decarbonizer significantly expands technological capabilities. Intermediate water decarbonization decreases the alkalinity of the Na+-cation exchange filter effluent, thereby hindering the hydrolysis of the salt form of the cation exchanger. Water obtained through magnesium ionization is advisable to be directed into the softened water stream. To prevent an increase in liquid pressure drop across the filter and a sharp decrease in filtration rate, it is proposed to pass the alkaline regeneration solution from bottom to top. [ABSTRACT FROM AUTHOR]

Freshwater resources are limited; thus, different technologies for desalination of brackish and seawater have been developed. Capacitive deionization (CDI) is one of the most promising desalination technologies owing to its low cost, simplicity, nonmoving parts, and low energy consumption. However, its energy consumption significantly increases with desalination of high-salinity water. In this regard, a good understanding of the effects of different process parameters on CDI energy consumption is crucial for further performance improvement. Therefore, the surface response methodology (RSM) was adopted to systematically study the effects of applying voltage, Stern layer capacity, volume and concentration of feed water, and volume of micropores on energy consumption and desalination time. The results showed that the Stern layer capacity and volume of micropores reduced desalination time by approximately 25% without significant changes in energy consumption. With the design of an improved electrode (improving the micropore structure for ion adsorption), the desalination time (Cycle) was reduced and a slight reduction in energy consumption was achieved. It can be claimed that any improvement in the physical (porosity) and electrical properties of the electrodes, results in an important increase in the performance of the CDI system. [ABSTRACT FROM AUTHOR]

This study uses electrochemical technology to simultaneously remove salt and degrade organic pollutants to achieve green and efficient treatment of high-salt organic wastewater. In this study, graphene oxide (GO), which has excellent conductivity, chemical stability, and catalytic adsorption performance, was selected to prepare a composite electrode, aiming to explore its performance and evaluate its possibility of being used for the degradation of high-salt phenol wastewater treatment. The samples were characterized using SEM, FTIR, and other techniques. The electrochemical performance of the samples was analyzed using an electrochemical workstation, and their practical application performance was explored through simulated wastewater experiments. Experimental results confirmed that among the three electrodes prepared, the CFGE exhibited the lowest system energy consumption and the highest current efficiency, measuring 235.81 kWh/kgCOD and 12.66 % respectively. The HGE electrode is second only to it, with 269.39 kWh/kgCOD and 11.08 % respectively. The SCGE electrode has the worst performance, which is 344.83 kWh/kgCOD and 8.66 % respectively. The Yst of the three electrodes are 0.4083 mg/L-min, 0.3817 mg/L⋅min, and 0.29 mg/L⋅min respectively. This study provides new research ideas and solutions for the efficient treatment of high-salt organic wastewater. [ABSTRACT FROM AUTHOR]

The increasing scarcity of fresh water due to rapid population growth and the establishment of new industries every single day has motivated researchers to use efficient technologies for the removal of dissolved salts from water. Various methods of salt removal and wastewater treatment have been established in last decades; however, membrane capacitive deionization has gained much attention due to its low energy consumption and low process costs in water treatment applications. The progress of membrane capacitive deionization for desalination and water treatments is systematically presented in this review. This review includes significant input on the membrane capacitive deionization progress, the current status of membrane capacitive deionization in the removal of salts and different pollutants, and a comparative discussion on various membranes and electrodes used in membrane capacitive deionization reported so far. It also highlights a summary and future scope in the area of membrane capacitive deionization. Based on the literature available and a review of the membrane capacitive deionization process, it could be a more effective and promising process for desalination and water purification. [ABSTRACT FROM AUTHOR]

[Display omitted] • Flexible free-standing hierarchical SnS 2 @NC hybrid electrode was fabricated. • The hollow structure alleviates volume expansion and facilitates ion diffusion. • A high electrosorption capacity and a rapid salt adsorption rate were achieved. • Work function-driven interfacial electron transfer accelerates reaction kinetics. Constructing pseudocapacitive electrodes with high specific capacities is indispensable for increasing the large-scale application of capacitive deionization (CDI). However, the insufficient CDI rate and cycling performance of pseudocapacitive-based electrodes have led to a decline in their use due to the corresponding volumetric expansion and contraction that occurs during long-term CDI processes. Herein, hierarchical porous SnS 2 nanoflakes are encapsulated inside an N -doped carbon (NC) matrix to achieve efficient CDI. Benefiting from the synergistic properties of the pseudocapacitive SnS 2 nanoflakes and few-layered N -doped carbon, the heterogeneous interface simultaneously provides more available vigorous sites and demonstrates rapid charge-transfer kinetics, resulting in a superior desalination capability (49.86 mg g−1 at 1.2 V), rapid desalination rate (1.66 mg g−1 min−1) and better cyclic stability. Computational research reveals a work function-induced surface charge redistribution of the SnS 2 @NC heterojunction, which can lead to an auspicious surface electronic structure that reduces the adsorption energy to improve the diffusion kinetics toward sodium adsorption. This work contributes to providing a thoughtful understanding of the interface engineering between transition metal dichalcogenides and NC to construct high-performance CDI electrode materials for further industrialization. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is an emerging electrochemical‐based adsorption system that has a high capability for the water reclamation with future potential towards an energy‐efficient and cost‐effective technique for industrial implementations. However, the higher cost of electrodes and poor performance limit its scale‐up, and there is a need to focus on a cost‐effective electrode towards economic impacts. Among the various waste resources, plastic sources would be the better precursor for carbonization as the plastic‐derived carbon possess enhanced surface properties and high electrochemical stability. Further, the carbonization of plastic products towards electrode minimizes greenhouse gas emissions, maintains environmental sustainability and achieves a dual benefit of circular economy with water reclamation. This paper highlights the overview of CDI, the significance of electrodes in CDI for electrosorption studies, various synthetic routes of plastic‐derived carbon, and its properties that help the researchers to focus on zero waste discharge‐based CDI process. [ABSTRACT FROM AUTHOR]

The desalination of seawater is one of the most established techniques in the world. In the middle of the 20th century using water evaporation systems, later with reverse osmosis membranes and nowadays the possibility of capacitive deionization membranes. Capacitive deionization is an emerging technology that makes it possible to obtain drinking water with an efficiency of 95%. This technology is in the development stage and consists of porous activated carbon electrodes, which have great potential for saving energy in the water desalination process, and which can be used for desalination process, using an innovative technology called capacitive deionization. A prototype has been designed and can operate with constant current charging and discharging. Adequate precision has been achieved, as can be seen in the results obtained. A philosophy of using free software with opensource code has been followed, such as: the Arduino and Processing Programming Editors; as well as the Arduino Nano Board, the analog-to-digital converter and the Adafruit digital-to-analog converter. Moreover, a low-cost system has been developed. A robust and versatile system has been designed for water treatment, and a flexible system has been obtained for the specifications established as it is shown in the results section. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is proposed as a thermodynamically effective desalination method for treating non‐potable water with a low‐salt concentrator to address the growing need for clean drinking water. MXenes, 2D transition metal carbides derived from Mn+1AXn (n = 1, 2, 3, or 4) bulk phases, are an intriguing class of crystalline materials with unique physicochemical properties. However, a significant challenge for their practical use is the degradation and phase transition experienced by MXene flakes when exposed to aqueous conditions. Several strategies for improving MXene stability are proposed, including combining it with porous materials such as carbon and metal–organic frameworks (MOFs). In addition to ZIFs, antioxidants with amine functional groups are used to stabilize MXene. Additionally, amine‐functionalized MXenes exhibit improved resistance to oxidation caused by water, enabling them to maintain their dispersity in aqueous solutions at room temperature. The produced A‐ZIF@MXene electrode represents high desalination performance with the highest salt adsorption capacity up to 80.3 mg g−1 in 1000 mg L−1 The NaCl solution reserve more than 99% of its initial capacity in 50 cycles to the synergism of its surface amine groups, high hydrophilicity, and distinctive hierarchical porous structure. [ABSTRACT FROM AUTHOR]

The scarcity of freshwater has attracted the attention of countries around the world. Capacitive deionization (CDI) is a burgeoning green desalination technology with low price and high efficiency. The properties of the CDI electrodes directly affect the deionization efficiency. It is a hot spot of CDI technology research to develop electrode materials with higher adsorption capacity, better sustainability and lower cost. On this purpose, porous carbon materials derived from corncobs, cornstalks and waste cigarette butts have been firstly used as electrodes for CDI desalination in this paper. Eight derived materials have been successfully prepared through carbonization and activation. The morphology characteristics and electrochemical performance of the materials have been examined. Their desalination performance has been investigated. The results show corncobs activated at 800°C (CBC-800) have the best properties with a specific surface area of 1,201.9 m²·g-1 and pore size of 1.7268 nm. The CBC-800 electrode also possesses a high specific capacitance of 141.4 F·g-1 and low inner resistance. The salt adsorption capacity is 19.2 mg·g-1 and the charge efficiency is 60.3% in a 3,000 mg·L-1 NaCl solution at 1.2 V. CBC-800 is expected to be an efficient electrode material for CDI applications. [ABSTRACT FROM AUTHOR]

The Microbial Desalination Cell is a novel method for desalinating water that also generates energy via substrate oxidation. The MDC comprises three chambers: the anode chamber, the desalination chamber, and the cathode chamber. The fundamental problem with the technology is that it generates very little power during the oxygen reduction reaction (ORR). One solution to this issue is to use a highly active cathode catalyst, which effectively increases the ORR rate. Neodymium-doped ZnO nanoparticles were produced and employed as a cathode catalyst in the three-chambered MDC1 to improve performance. Zn1−xNdxO nanocrystalline samples containing x = 0.0, 0.03, 0.6, and 0.10 were synthesized efficiently through the cost-efficient sol-gel method. Transmission electron microscopy (TEM) and X-ray diffraction techniques revealed the nanocrystalline nature and the phase purity of the Zn1−xNdxO samples. The structural properties of ZnO nanostructured materials were elucidated by Rietveld refinement of the XRD patterns, which showed displacement of Zn and O ions and revealed changes in the electron density around the Zn-O bond with Nd substitution. The local features of light emission from Zn1−xNdxO samples have been studied with photoluminescence. The UV and green-yellow emissions originate from the exciton transition and the transition between the Nd3+ deep level, oxygen vacancy and interstitial oxygen. The results were compared to MDC-2, which did not have a catalyst on the cathode. Both MDCs were tested using a saline water solution containing 15 g/L of NaCl to measure their desalination performance. The better reduction kinetics was confirmed by cyclic voltammetry of the MDC-1 cathode. MDC-1 had a higher desalination efficiency (77.02% ± 2.0%) due to the presence of an Nd-doped ZnO catalyst than MDC-2 (59.3% ± 8.3%). MDC-1's maximum power density of 3.65 W/m3 was 2.78 times greater than MDC-2's (0.78 W/m3). Furthermore, the coulombic efficiency of MDC-1 was found to be (8.8 ± 0.3%), which was much higher than that of MDC-2 (4.56 ± 0.2%). As a result, the Nd-doped ZnO-based catalyst developed in this study can potentially improve ORR in MDC cathodes, enabling them to generate more power. [ABSTRACT FROM AUTHOR]

Environmental protection associated with renewable energy is among the most critical challenges for translational ion‐capture based on capacitive storage of ions in electrical double layers at the interface of electrode and electrolyte. Electric double‐layer capacitance with charge induction and faradaic pseudo‐capacitance with charge transfer classifies the capacitance of the electrochemical interface. The electrochemical interface in most energy technologies involves porous and pseudocapacitive redox materials that offer varying degrees of electrolyte confinement. In this review, we discuss the factors affecting water desalination, such as the effect of nanopores for ion capture, the ion sieving effect, the effect of hydration energy, and hydration radius in the carbon sub‐nanometer pore. Moreover, the surface phenomena of electrodes, including carbon corrosion, and the potential of zero charge to control the oxidation of carbon electrodes are explained along with protection mechanisms. The various capacitive deionization (CDI) operations and the corresponding electrochemical cell technologies are briefly introduced, including the significance of double‐layer charging materials with faradaic intercalation, which suffer less from co‐ion expulsion. Finally, we revisit the effects of various nanoarchitectures and the construction of capacitive deionization electrodes for clean water technology. [ABSTRACT FROM AUTHOR]

MXene has drawn widespread attention as a potential material for electrode use in capacitive deionization (CDI). However, the applications of MXene are limited by its property of low electrical capacity. Herein, a MnO2/MXene composite was firstly evaluated in a capacitive deionization system, in which the MnO2 acts as intercalation-type pseudocapacitive electrodes to enhance the electrical capacity, and MXene provides an electron conduction highway network that improves the charge transfer of the MnO2. The result showed that the low-crystallinity MnO2 with irregular particles was well-distributed on the surface of the MXene. The desalination capacity of 30.5 mg·g−1 is achieved at a voltage window of 1.2 V, which was higher than that of the reported pure MXene and MnO2. The electrical double-layer (EDL) capacitive and the diffusion-controlled processes are the main charge storage mechanisms, and the EDL contribution provides 50.3% to the total capacitance. This result suggests a promising direction for further applying a MnO2/MXene composite in CDI. [ABSTRACT FROM AUTHOR]

This work presents an electrical double layer (EDL) model for capacitive deionization (CDI) by intercorrelating the salt adsorption, the electrode voltage, and the surface charge density. The counterion condensation is considered a crucial contribution to salt adsorption because of the high surface charge density in the charged micropores. The counterions condense when the surface charge density exceeds a critical value, which is predicted by the counterion condensation theory. The EDL model accurately correlates the NaCl salt adsorption and electrode voltage with various surface charge densities and well predicts the salt adsorption in a wide range of external salt concentrations. The EDL model reproduces the non‐monotonic relationship between the salt adsorption and the specific surface area observed in experiments and provides an explanation from the modeling perspective. Exhibiting superior accuracy and predictability for salt adsorption, the EDL model could serve as an enabling tool contributing to the development of CDI processes. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is a promising desalination technology based on electrosorption on the surfaces of microporous electrodes. However, low total dissolved solids (TDS) in the water restricts its efficacy. In this work, we develop the theory of capacitive spacers (CS) in CDI. The investigations reveal a mechanism that we call ohmic charging; that is, the resistive losses in the spacer region drive adsorption in the CS. As a consequence, the obtained results show that such spacers can improve desalination efficiency, especially at ion‐starved conditions. The spacers also enhance the charging rate of the electrodes because the overall resistance is lower when the current can pass the spacer material instead of the solution, through the adsorption of anions on one side and cations on the other. Going deeper, the investigations reveal a major challenge; the spacer naturally discharges on the same timescale as the electrode charging timescale. However, only the fast timescale matters with low ionic content solutions, and under these conditions the CS are found to be superior. Put together, CS can make a significant difference, especially when the ion concentration is low or the cycle times are short. [ABSTRACT FROM AUTHOR]

In this study, carbon aerogels (CAs) were synthesized by the sol-gel method, using environmentally friendly glucose as a precursor, and then they were further activated with potassium hydroxide (KOH) to obtain activated carbon aerogels (ACAs). After the activation, the electrochemical performance of the ACAs was significantly improved, and the specific capacitance increased from 19.70 F·g−1 to 111.89 F·g−1. Moreover, the ACAs showed a stronger hydrophilicity with the contact angle of 118.54° compared with CAs (69.31°). When used as an electrode for capacitive deionization (CDI), the ACAs had not only a better diffuse electric double layer behavior, but also a lower charge transfer resistance and intrinsic resistance. Thus, the ACA electrode had a faster CDI desalination rate and a higher desalination capacity. The unit adsorption capacity is three times larger than that of the CA electrode. In the desalination experiment of 100 mg·L−1 sodium chloride (NaCl) solution using a CDI device based on the ACA electrode, the optimal electrode spacing was 2 mm, the voltage was 1.4 V, and the flow rate was 30 mL·min−1. When the NaCl concentration was 500 mg·L−1, the unit adsorption capacity of the ACA electrode reached 26.12 mg·g−1, much higher than that which has been reported in many literatures. The desalination process followed the Langmuir model, and the electro-sorption of the NaCl was a single layer adsorption process. In addition, the ACA electrode exhibited a good regeneration performance and cycle stability. [ABSTRACT FROM AUTHOR]

• Nitrogen-doped porous carbon with controlled pore structure and wettability was synthesized. • The nitrogen-rich feature of carbon material enables both electrical conductivity and surface wettability. • SMS-AC realizes large adsorption capacity of 8.38 mg/g and high charge efficiency of 90.66 % Nitrogen-doped porous carbon with controlled pore structure and wettability was synthesized using spent mushroom substrate (SMS) via physical activation process. The nitrogen-rich feature of precursor enables the carbon material to possess both electrical conductivity and surface wettability, creating an effective conducting network in flow electrodes. These materials have been proven to be highly efficient for deionization due to their ability of maintaining surface wettability and electrical conductivity. Our results show that the SMS-1.5 sample has a high adsorption capacity of 8.38 mg/g, which is 1.8 times greater than the commercial YP-50. The corresponding charge efficiency was up to 90.66 % after being exposed to 1.6 g/L NaCl feed solution for 120 min in flow electrode capacitive deionization device. This study highlights the significance of the inherent nitrogen element in biomass for the synergistic promotion of electrical conductivity and surface wettability, providing a strategy for designing porous carbons with excellent desalination performance. [ABSTRACT FROM AUTHOR]

• A balanced discussion on the technological requirements of NASICONs. • Comparison of cost of NASICON and carbon-based materials. • The performances of NASICON materials. • The methods to enhance the performance of NASICON materials. • NASICON materials for sodium ion battery can be applied in CDI. The world is suffering from water shortage and the hope relies on the desalination of salty water. Several technologies are available for desalination such as reverse osmosis and electrodialysis. However, the application of these technologies in desalination is limited by the higher energy consumption, high investment and maintenance costs. Capacitive deionization (CDI), an up-coming technology at an infant stage is able to supplement the dwindling freshwater resources and provide water to the population. The performance of CDI is directly affected by the electrode materials. Since its inception carbon has been the principal electrode materials for CDI technology. However, low salt removal capacity due to inaccessibility of nanopores and ejection of co-ions hinder the application of carbon materials. Battery materials have been developed as an alternative to accompany carbon materials. Specifically, sodium superionic conductor (NASICON) materials have been used in brackish water desalination by CDI due to having the diffusion channels forming a three dimensional open structure and availability at low cost. However, the NASICON materials have not yet applied in the desalination of water with high salinity such as sea water. This paper reviews the present status of NASICON materials as CDI electrode materials and fairly compares it with carbon materials. It further compares the cost of NASICON and carbon materials, highlights the possibility of NASICON to desalinate high ionic strength solutions such as seawater. Moreover, the paper, discuss the methods which can be used to enhance the salt removal capacity of NASICON materials and provide examples of NASICON materials in the field of energy storage that can be borrowed and used in CDI. From the analysis of this work, NASICON materials are great companion of the carbon materials, are cost effective and are promising for the desalination of sea water. [ABSTRACT FROM AUTHOR]

This study focused on removing salts and nutrients (nitrogen and phosphorus) from tertiary treated urban wastewater by capacitive deionization. The performance of a pilot-scale radial capacitive deionizer subjected to varying feed flow rates during the purification stage and constant flow rates during the reject stage was evaluated. This operational strategy aimed to maximize the water recovery rates of the system, with electrical adjustments being made proportionally to the water recovery rate. Lower hydraulic loads resulted in the radial capacitive deionizer removing more ions from the sewage, albeit with higher specific energy consumption. Optimal operational conditions reduced conductivity by 92.8 %, with a specific energy consumption of 2.17 kWhm−3. Significant removals of ammonium, nitrite, nitrate, and orthophosphate ions were observed, with average specie reductions of up to 84, 91.4, 100, and 60.5 %, respectively. Higher rates of treated water recovery resulted in lower ion removal reduction and energy consumption. The limiting step of the process referred to ion desorption, requiring the correct adjustment of the time lapse, flow rate, and applied electrical voltage to ensure the efficiency of the subsequent purification stage. A loss of efficiency was observed when the process was run continuously, thus emphasizing the strategic significance of capacitor rinsing during the rejection phase across multiple subsequent treatment cycles. • Significant removals of NH 4 +, NO 2 −, NO 3 −, and PO 4 3− from the effluent were observed. • The lower the hydraulic loads, the higher the removing rates of ions from the sewage. • The best ions removals were achieved with the higher specific energy consumption. • The limiting step of the process was the ion desorption during capacitor rinsing. [ABSTRACT FROM AUTHOR]

[Display omitted] • A comprehensive review to highlight the application of 3D faradic materials in CDI field is presented. • The desalination performances of non-3D faradic electrodes and 3D faradic electrodes are systematically compared. • The perspective of 3D faradic materials is discussed to provide guidelines for future CDI development. To address the water scarcity issue, capacitive deionization (CDI) as a burgeoning desalination technology for removing different ions from sea and wastewater have been intensively explored. However, the low salt adsorption capacity and poor cycling stability of widely used carbon materials are difficult to fulfill the demand of practical CDI application, while the non-three-dimensional (non-3D) faradic electrode materials manifest the drawbacks of low specific capacitance and dissolution loss of metal ions, which severely limit their CDI application. Notably, three-dimensional (3D) faradic materials usually possess higher desalination capacity and better cycling stability than carbon materials and non-3D faradic materials, due to their wide ion diffusion channels and versatile structure, which are highly promising for achieving practical CDI application. However, few review papers have specifically focused on the limitations and advantages of 3D faradic materials in CDI field. In this review, a comprehensive insight into 3D faradic materials in terms of the solutions of limitations and corresponding desalination performance (via comparing with the desalination performance of non-3D faradic materials) is provided and the development prospect of 3D faradic materials is also expounded. [ABSTRACT FROM AUTHOR]

This research project aims at investigating the performance of hydroponic nutrient solutions as draw solutions for desalination using the fertilizer drawn forward osmosis (FDFO) process. Six different lettuce and leafy greens hydroponic nutrient stock solutions were prepared according to the literature and used in this study and tested on a bench-scale forward osmosis unit as draw solutions for the process. The feed solution for the process was deionized water mixed with NaCl in different concentrations, to represent different salinities of brackish groundwater. The draw efficiency of each solution was measured based on water flux, specific reverse solute flux, water recovery, and salt rejection. It was concluded that of the six tested nutrient solutions, the "Resh Florida, California" solution is the recommended solution to be used as draw solution for fertilizer drawn forward osmosis, due to its high performance in terms of water recovery (15.75%), flux (11 L/m2/h), salt rejection (92%), and SRSF (highest recorded SRSF for a specific ion (SO42−) was 7.3 g/L), as well as its low cost, relative to the other highly performing draw solution "Chekli" ($1.07/L vs. $3.73/L). [ABSTRACT FROM AUTHOR]

In the present study, zinc ion‐exchanged zeolite Y (ZnY) was incorporated as a dispersed phase into polyphenylsulfone (PPSU) polymer matrix to prepare PPSU/ZnY porous mixed matrix membranes (MMMs) with enhanced separation properties. Various MMMs with different ZnY contents (0, 0.25, 0.5, 0.75, 1, 1.5, and 3 wt.%) were fabricated using phase inversion method. The morphologies of prepared membranes were characterized by using scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis. Fourier transform infrared (FTIR) and X‐ray diffraction (XRD) were used to investigate the chemical structures and microstructural properties, respectively. Differential scanning calorimetry (DSC) analysis and tensile test were done to investigate thermomechanical properties of the membranes. Density and dynamic viscosity of membrane casting solutions as well as porosity, mean pore size, contact angle and water content of the prepared membranes were determined to investigate how these parameters affect the morphology of the membranes. Finally, separation performance of the membrane samples was investigated by determining water flux, salt (CuSO4) rejection, and anti‐fouling properties. SEM results showed an increase in top layer pore volumes with the incorporation of ZnY nanoparticles, which offer a higher water flux. AFM images indicated the higher surface roughness for an MMM compared to the pure PPSU membrane. FTIR spectroscopy confirmed the presence of all PPSU and ZnY functional groups in the MMM and showed no existence of chemical bonds at the polymer‐particle interface. XRD patterns exhibited a decrease in the degree of crystallinity by addition ZnY nanoparticles into PPSU matrix. DSC and tensile tests confirmed the XRD analysis and show lower Tg and tensile stress for an MMM compared to the pure PPSU membrane. Porosity measurements showed that the membrane porosity improved by decreasing the polymer concentration in the casting solutions and by incorporation of ZnY nanoparticles. The contact angle measurement indicated that the values decrease upon loading of ZnY nanoparticles. Finally, an enhanced pure water flux of 4.315 L m−2 h−1 bar−1 and a salt rejection of 75%, respectively as compared to 3.591 L m−2 h−1 bar−1 and 81% for pure PPSU membrane, were observed for the MMM with 1 wt.% of ZnY filler. [ABSTRACT FROM AUTHOR]

Flow-electrode capacitive deionization (FCDI) represents an innovative, chemically-free, and environmentally-friendly approach for desalination. However, the long-standing challenge of constrained electronic and ionic transport within its flow-electrode has impacted overall desalination performance. In this study, we explore novel concepts and advancements in capacitive deionization by utilizing hierarchical porous carbon (HPC) flow electrodes. By employing widely available sodium carboxymethyl cellulose as a carbon precursor and NaCl as an activator, we have successfully synthesized a carbon-based particle electrode featuring a hierarchical porous structure. The HPC electrode was further optimized through precise adjustments to its pore structure. The optimized electrode exhibited excellent dispersion, viscosity, and remarkable specific capacitance of 283.96 F g−1. Under optimal conditions of a 10% mass loading and an applied voltage of 1.2 V, the electrode demonstrated an average salt removal rate of 82.11 μg cm−2 min−1, a charge efficiency of 101.44%, and an energy consumption of 9.32 × 10−3 kWh mol−1. Furthermore, we investigated the optimal operating parameters for the FCDI device equipped with the HPC flow electrode. Impressively, the HPC flow electrode achieved a salt removal efficiency exceeding 80% over five cycles, maintaining an average salt removal rate of 54.00 μg cm−2 min−1 during 12 h of continuous operation. Detailed textural analysis and electrochemical characterizations revealed that the superior desalination performance is attributed to the hierarchical porous structure of the electrode. This unique structure significantly enhances both electronic and ionic transport within the FCDI system. Our study underscores the critical role of hierarchical porous carbon flow electrodes in capacitive deionization, paving the way for novel strategies to optimize ion and electron transport. • Novel hierarchical porous carbon (HPC) electrodes were used in FCDI. • Structural advantage of HPCs in electronic and ionic transport was investigated. • ASRR, CE and E m of HPCs reached 82.11 μg cm−2 min−1, 101.44% and 9.32 × 10−3 kWh mol−1, respectively. • HPC flow-electrodes had good stability and durability in desalination process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Asymmetric membrane CDI (ACDI) is proposed for the removal of short-chain PFAS. • Deionization performance of ACDI for short-chain PFAS was better than MCDI. • Good deionization capacity (28.75 mg/g) & energy consumption (0.46 Wh/g) were achieved. • Even in the presence of competing ions, removal of short-chain PFAS was observed. Concerns have been raised over the persistence and potential health risks of perfluoroalkyl substances (PFAS). PFAS pose significant challenges in water treatment owing to their chemical stability and the difficulty of treating them with conventional purification methods. Although traditional water treatment methods for contaminant removal have been explored, their effectiveness against PFAS remains limited. This gap in knowledge highlights the need for innovative approaches. This study introduces asymmetric membrane capacitive deionization (ACDI) as a novel method for short-chain PFAS removal to address the shortcomings of existing techniques. ACDI refers to a configuration in which an anion exchange membrane is removed from a conventional membrane capacitive deionization with both a cation exchange membrane and an anion exchange membrane. Among the PFAS, perfluorobutanesulfonic acid (PFBS), which is known to be difficult to remove because of its short chain, has been the focus. The ACDI system demonstrated superior deionization capacity (28.75 mg/g) and energy efficiency (energy consumption of 0.46 Wh/g) compared to conventional CDI and membrane CDI systems. In addition, the effects of key operating parameters, such as voltage (0.5 ∼ 1.2 V), initial concentration (50 ∼ 500 mg/L), and flow rate (1 ∼ 5 mL/min), on the PFBS removal were systematically investigated and superior at 1.2 V, 500 mg/L, and 2 mL/min. This study suggests the need for further exploration of real-world applications considering the presence of competing ions in wastewater. This study provides valuable insights into advancing CDI technology for the sustainable treatment of industrial wastewater containing PFAS. [ABSTRACT FROM AUTHOR]

Tetracyclines are among the most widely used antibiotics, and the saline organic wastewater generated during their production has caused serious environmental problems. Thus, it is imperative to develop effective methods for treating this antibiotic wastewater. In this study, we examined the structural characteristics and electrochemical performance of nitrogen-doped carbon materials and assessed the effects of nitrogen doping on the performance of a peroxymonosulfate (PMS)-coupled membrane capacitive deionization (MCDI) system for removing tetracycline (TC) and salt. Having optimized the carbonization temperature and system operating parameters, we observed that in response to an increase in carbonization temperature, there was an increase in the abundance of surface functional groups in the material, which promoted the ion migration capacity of the electrode and PMS activation sites. In addition, we observed that nitrogen doping can alter the electrical properties of carbon materials, provide a larger number of adsorption sites, and enhance the interactions between carbon structures and salt ions, thereby improving material properties. Under optimal operating conditions, the salt adsorption and tetracycline removal rates reached 30.2 % and 61.8 %, respectively. Our findings in this study provide a feasible method for the treatment of saline tetracycline wastewater. [Display omitted] • MCDI coupled PMS treatment system for TC wastewater were constructed firstly. • Preparation of electrode materials by simple doping urea as a nitrogen precursor. • The couple system effectively remove TC (61.8 %) and ions (30.2 %), simultaneously. • The operation mechanism of the system has been fully analyzed. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is an electrochemical desalination technology that removes ions from brackish water through electrosorption within charged porous electrodes. Brackish waters contain ions that may form precipitates on the electrodes (e.g., Ca2+, Mg2+, CO 3 2−), especially in response to localized pH increases common at cathodes. Here we study the formation of calcium carbonate (CaCO 3(s)) on the cathode and its effect on Na+ removal using defined solution chemistries. We found that CaCO 3(s) formed during the charging phase at the cathode, but not the anode. Local precipitation was likely due to the in situ basic pH caused by the reduction of dissolved oxygen at the cathode. The deposition of solids reduced Na+ adsorption capacity by 67 % (0.94 ± 0.08 mg/g-C) compared to a control where no Ca2+ and HCO 3 − were present. We attributed this reduction primarily to the ∼30 % decrease in micropores available for electrosorption. These interior pores were blocked by non-porous CaCO 3 crystals. Cathodes with precipitation had reduced capacitance and increased resistance. The deposition of non-conductive crystals hindered the transfer of charge and restricted the movement of ions from the bulk solution toward the electrode surface and also through the pores' structure. Since precipitation was found to be detrimental to salt removal, future research is needed to reduce scaling and/or strategies to regenerate the electrosorption capacity of electrodes. For other applications, such as water softening, research to improve precipitation might be desired. [Display omitted] • Calcium carbonate precipitated on the cathode in flow-through capacitive deionization • Precipitation reduced sodium adsorption capacity by almost 70 % • Cathode micropore volume decreased by 30 % after precipitation • Precipitation was associated with an increase in resistance and decrease in capacitance [ABSTRACT FROM AUTHOR]

As water scarcity intensifies, the quest for developing sophisticated electrode materials with adjustable configurations, complex structures, and developed desalination performance garners important interest. Prussian Blue (PB) and its analogs (PBAs), owing to their cost-effectiveness, uncomplicated synthesis, innate open framework, and modifiable composition, have elicited considerable recognition. Herein, the paper provides a comprehensive overview and analysis of the advances made in capacitive deionization electrodes based on PB and PBAs. It commences by detailing the synthesis techniques, post-treatment processes, and derivatives of standard PBs and PBAs. Subsequent sections propose strategies to minimize auxiliary reactions in electrochemical processes, encompassing structural design, protective coatings, substitution, and the confinement effect. Subsequently, emphasis is placed on structures that have potential as electrode materials in applications such as desalination, heavy metal removal, resource recovery, and water softening. A summary of current achievements in the field is provided, alongside a critique of prevailing limitations and emergent challenges. As advancements in electrode materials continue to unfold, it aims to stimulate innovative ideas for utilizing PB and PBAs in environmental research, thereby catalyzing additional investigation into the desalination area. [Display omitted] • The preparation methods of advanced PB/PBAs electrode are discussed in depth. • The versatile applications of PB/PBAs electrode are discussed extensively. • The future orientation development of PB/PBAs in CDI is provided. [ABSTRACT FROM AUTHOR]

The effective desalination and purification devices for seawater/ brackish water treatment are crucial in sustainable progress. Techniques that render high salt removal efficiency and water purification ability at low applied potentials play a central role in sustainable water supplies. One of themis capacitive deionization (CDI) which has drawn significant consideration as a promising deionization technology since the last decade. Desalination efficiency profoundly depends on the utilized electrode material. The most widely used CDI electrodes are carbons due to their cost effectiveness and good stability. However, to acquire high electrosorption capacity, extensive researches are reported with modified carbon materials. CDI cell architectures are equally important for practical high salt removal performance. This review focuses on carbon materials in CDI along with other emerging trends in diverse carbon types, e.g., carbon nanotubes and their composites. Various architectures reported in the literature to improve desalination efficiency are also included here. [ABSTRACT FROM AUTHOR]

Capacitive deionisation (CDI) of saltwater, with the advantages of low energy consumption and being environmentally friendly, has been considered a potential solution to the scarcity of fresh water from sea, contaminated or waste waters. In the present work, Ag@C core-shell nanoparticle dispersed rGO (Ag@C/rGO) electrodes were synthesised and used for the CDI of saltwater. To better understand the formation mechanism of the Ag@C core-shell nanoparticles, temperature-programmed carbonisation of the Ag+-β-cyclodextrin complexes was studied by in situ synchrotron small-angle X-ray scattering spectroscopy. At 573 K, the core Ag metal forms Ag@C core-shell nanoparticles with the highest probability nanosizes of 40-80 nm. In the 4-cycle flow-by CDI (once through) experiments using the Ag@C/GO electrodes, high electrosorption efficiencies (25.0-44.9%) were obtained. Each CDI cycle involving electrosorption at 1.2 V and regeneration at 0 V for 1 h was highly reversible. In addition, the disinfection efficiency of the Ag@C/rGO electrodes, contributed by both silver and rGO, was very high (>97%). This study shows that the easily synthesised Ag@C/rGO core-shell carbon-based electrodes are feasible for simultaneous deionisation and disinfection of saltwater as a potential source of drinking water. [ABSTRACT FROM AUTHOR]

Water is the most abundant liquid on Earth, but only 2.5% of worldwide water are fresh. It is impossible to ignore the importance of water in almost every process on Earth, from the smallest bacteria life to the formation of the continents. Today, efforts for the desalination of seawater and brackish water are critical to produce drinking water. In recent years, a novel material: hydrogel, was considered in desalination processes. Interesting hydrogel applications were proposed for forward osmosis desalination, solar still, electrodialysis, and capacitive desalination. Simple and inexpensive desalination ways for drinking water production are needed. Hydrogel compounds are one of the leading options in such issue. The use of the hydrogel-based solar steam generator could produce drinkable water cheaper than other water desalination processes. The hydrogel classification is based on physical structure, ion charge, synthesis methods, particle size, chemical, and physical bonding, and mechanical properties. Therefore, this review summarizes the recent research progresses in the use of hydrogels for desalination and purified water production. [ABSTRACT FROM AUTHOR]

A combination of biomass-derived activated carbon and nano-carbonaceous materials has been considered as a sustainable approach to developing the highly electro-adsorptive electrode for desalination by capacitive deionization (CDI) technology. These composites can propose many enormous advantages such as non-toxicity, eco-friendly, high conductivity, and scalability. This work aimed to fabricate the composite coconut-shell-derived activated carbon/carbon nanotubes electrode with low CNTs content (1 wt%) for desalination. The nitrogen adsorption/desorption demonstrates the decrease of surface area of AC/CNTs-1% composite as compared to AC-pristine due to the blocking of micropores of AC. The SEM images evidenced good connection between CNTs and AC particles, where the fibrils of CNTs were featured as the electrical bridges to improve the electron transfer between the AC particles in the electrode structure. Comparison of the CDI performance of AC/CNTs-1% composite electrode in two regimes (batch mode and single-pass mode) in Ragone plot showed that the single-pass mode provided the essential factors of salt absorption capacity and average salt adsorption rate which shifted toward much upper and right regions, indicating the superior desalination performance. At the operation of 1.2 V, the batch mode and single-pass mode can deliver the salt absorption capacity of 10.93 mg g−1 and 11.97 mg g−1, respectively. The durability test of our CDI system in single-pass mode showed a stable performance on 100 cycles with the energy consumption of 0.284 kWh m−3 which is suitable for large-scale CDI applications using the renewable energy sources. [ABSTRACT FROM AUTHOR]

Shock electrodialysis is a recently developed electrochemical water treatment method that shows promise for water deionization and ionic separations. Although simple models and scaling laws have been proposed, a predictive theory has not yet emerged to fit experimental data and enable system design. Here, we extend and analyze existing "leaky membrane" models for the canonical case of a steady shock in crossflow, as in recent experimental prototypes. Two‐dimensional numerical solutions are compared with analytical boundary‐layer approximations and experimental data. The boundary‐layer theory accurately reproduces the simulation results for desalination, and both models predict the data collapse of the desalination factor with dimensionless current, scaled to the incoming convective flux of cations. The numerical simulation also predicts the water recovery increase with current. Nevertheless, neither approach can quantitatively fit the transition from normal to over‐limiting current, which suggests gaps in our understanding of extreme electrokinetic phenomena in porous media. [ABSTRACT FROM AUTHOR]

Desalination of saline water was carried out by capacitive deionization (capDI) method. Pseudocapacitive materials (CoFe2O4/Fe2O3) were coated on the carbon cloth as capDI electrode for three different reaction time (6, 9 and 12 h). Synthesized capDI electrodes were characterized using SEM, XRD, Raman and XPS. The desalination was tested by batch method to study the desalination performance of the synthesized electrode. The results showed that 89% and 30 % of desalination efficiency at 200 and 500 mg/L (1500 μS/cm initial conductivity), respectively for 6 h reaction time sample. The adsorption of inorganic ions from the saline water on 6 h sample was found to be about 30 mg/g at an initial concentration of 500 mg/L. The kinetic analysis indicated that the electrosorption of NaCl on capDI electrodes followed pseudo‐first order kinetics model. Overall, the developed pseudocapacitive capDI electrode was able to desalinate NaCl by capacitive deionization method under experimental condition. [ABSTRACT FROM AUTHOR]

• Cost-effective PDMS/CNTs@melamine solar evaporators were developed. • The evaporators showed good evaporation performance for saline water. • The evaporators exhibited excellent salt-resistance during long-term continuous solar desalination. • The evaporators may find applications in solar desalination and sewage treatment. Solar driven interfacial evaporation has received extensive attention as a very promising desalination technique to solve the fresh water shortage crisis. However, salt-fouling and poor stability during long-term solar desalination seriously hinder applications of solar evaporators. In addition, most of the reported evaporators rely on expensive materials and complex preparation processes. Here, we report facile preparation of polydimethylsiloxane/carbon nanotubes (PDMS/CNTs) modified melamine solar evaporators for efficient steam generation and desalination. The elastic solar evaporators feature (i) macroporous network with rough skeleton owing to phase separation of PDMS, high solar absorbance (99%) and excellent photothermal performance, low thermal conductivity (0.032 W m−1 K−1), and (iii) unique wettability (hydrophobic upper surface and hydrophilic lower part). Consequently, the evaporators have an evaporation rate of 1.44 kg m−2 h−1 and a solar-to-vapor conversion efficiency of 84% for solar evaporation of deionized water under 1 sun illumination. Interestingly, the evaporators show similar solar evaporation performance for saline water compared to deionized water. Moreover, the evaporators show excellent salt-resistance and stability during long-term continuous solar desalination owing to rapid water replenishment in the evaporators. The evaporators may find practical applications in solar desalination because of the merits of the evaporators and the simple preparation method. [ABSTRACT FROM AUTHOR]

Rapid population and economic growth cause severe anthropogenic emissions, which lead to many water pollutions. As a result, the demand for potable water is increasing dramatically in the last decades. Various logical solutions and sustainable developments, such as converting seawater into freshwater, have been explored. Several methods have been employed in water desalination, such as pressure-driven membranes, capacitive deionization, and adsorption desalination. Still, the limitations of the present technologies are low water productivity and quality. Therefore, it is essential to perform further research to design materials and methods with higher salt rejection property and large flux capacity. Recent study and development have pointed out an advanced material called metal-organic frameworks (MOFs) with fascinating chemical and physical properties. Researchers and engineers have been studying MOFs for their potential application in water desalination. This review is aimed to stimulate future research related to the utilization of MOFs for seawater desalination, particularly in the desalination membrane development. Recent advances from the MOF in water desalination are given, starting with outlining various studies of membrane-modified MOF, followed by the application of MOF in desalination technology. Finally, the explanation of the concept of increasing desalination performance by MOF to fill the knowledge gap. [ABSTRACT FROM AUTHOR]

Certain challenges exist in forward osmosis (FO) separation technique that has to be studied yet such as a selection of a proper draw solution (DS) to supply the required driving force for separation. In this work, the performance of molasses DS in terms of water flux (Jw) was evaluated using a commercial FO membrane. Deionized water (DIW), an oilfield brackish wastewater (BWW) and seawater (SW) were used as three different feed solutions (FS). Effects of molasses concentration (CDS) and solutions cross-flow velocities on Jw were investigated. The results indicated that the relationship between Jw and CDS is non-linear that may be attributed to internal concentration polarization in the membrane support layer. Jw was improved slightly by increasing the FS velocity and enhanced moderately by increasing the DS velocity from 6 to 11.5 cm/s. Fluxes of 16.7, 13.3 and 7.5 LMH were obtained during 30 min against the feeds of DIW, BWW and SW, respectively. After 12 h, the osmotic pressure of molasses is reduced from an initial value of 79.8 bar to 54.5, 62.8 and 66.3 bar for the FSs, respectively. Reverse solute flux is increased by decreasing Jw and is more significant at values lower than 10.67 LMH for DIW feed. Based on the results, Molasses has a good performance ratio in comparison to other fertilizers and diluted molasses can potentially be used for fertigation purposes. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is an emerging desalination technology for effective removal of ionic species from aqueous solutions. Compared to conventional CDI, which is based on carbon electrodes and struggles with high salinity streams due to a limited salt removal capacity by ion electrosorption and excessive co‐ion expulsion, the emerging Faradaic electrodes provide unique opportunities to upgrade the CDI performance, i.e., achieving much higher salt removal capacities and energy‐efficient desalination for high salinity streams, due to the Faradaic reaction for ion capture. This article presents a comprehensive overview on the current developments of Faradaic electrode materials for CDI. Here, the fundamentals of Faradaic electrode‐based CDI are first introduced in detail, including novel CDI cell architectures, key CDI performance metrics, ion capture mechanisms, and the design principles of Faradaic electrode materials. Three main categories of Faradaic electrode materials are summarized and discussed regarding their crystal structure, physicochemical characteristics, and desalination performance. In particular, the ion capture mechanisms in Faradaic electrode materials are highlighted to obtain a better understanding of the CDI process. Moreover, novel tailored applications, including selective ion removal and contaminant removal, are specifically introduced. Finally, the remaining challenges and research directions are also outlined to provide guidelines for future research. [ABSTRACT FROM AUTHOR]

Literature reporting temperature and desorption mode as factors of capacitive deionization (CDI) process for water desalination is rare. This study explored the impacts of four water temperatures (15°C, 25°C, 35°C, and 45°C), three salt concentrations (350, 1260, and 3100 mg/L), and three desorption modes (potential removal, short circuit, and polarity reversal) on performance of a 'closed-loop' CDI system. Results showed that a higher temperature promoted adsorption and desorption rates but impaired adsorption capacity. Polarity reversal could greatly expedite the desorption process compared to short circuit and potential removal. A promotional impact of concentration on CDI desalination could be explained by the formation of electrical double layers. The research also noted the earlier occurrence of re-adsorption at higher temperatures during polarity-reversal desorption. Strategies of increasing water temperature on short adsorption cycles and using an adjustable combination mode of polarity reversal and short circuit for desorption are implied for improving desalination efficiency and water recovery of CDI systems. [ABSTRACT FROM AUTHOR]

Pure uncoated magnetic nanoparticles (MNPs) were synthesized and studied as a potential draw solution (DS) in forward osmosis (FO) desalination process. Saturation magnetization was found to be 3.79 emu/g and the formation of Fe3O4 MNPs was confirmed by Fourier transform infrared and X-ray diffraction spectra. The osmotic potential of Fe3O4 MNPs was evaluated using a bench-scale crossflow FO unit. The feed solution (FS) of deionized water and NaCl solutions of different salinities (0.5, 1, and 2 g% NaCl) were evaluated. The water flux was found to decrease with the increase in water salinity of the FS by 62%, 78%, and 87% for the 2.5 g% MNPs, respectively. Furthermore, the Fe3O4 MNPs concentration (2.5 and 5 g%) was found to have a substantial impact on water flux with a three-fold increase in the pure water flux for the higher concentration. Results confirmed that the concentration of both FS (NaCl) and DS (MNPs) have a considerable effect on the produced pure water flux. This research demonstrated that the proposed uncoated Fe3O4 MNPs can be used as a potential draw solution for water desalination. [ABSTRACT FROM AUTHOR]

Here, a pH neutral aqueous organic redox flow battery (AORFB) consisting of three electrolytes channels (i.e., an anolyte channel, a catholyte channel, and a central salt water channel) to achieve integrated energy storage and desalination is reported. Employing a low cost, chemically stable methyl viologen (MV) anolyte, and sodium ferrocyanide catholyte, this desalination AORFB is capable of desalinating simulated seawater (0.56 m NaCl) down to 0.023 m salt concentration at an energy cost of 2.4 W h L−1 of fresh water—competitive with current reverse osmosis technologies. Simultaneously, the cell delivers stored energy at 79.7% efficiency with a cell voltage of 0.85 V. Furthermore, the cell is also capable of higher current operation up to 15 mA cm−2, providing 4.55 mL of fresh water per hour. Combining energy storage and water desalination into such a bifunctional device offers the opportunity to address two growing global issues from one hardware installation. [ABSTRACT FROM AUTHOR]

Investigations into the parameters of a CDI desalinator operating according to a two-step demineralization scheme have been conducted. The process of desalination has been analyzed in conjunction with electrophysical measurements. Various capabilities of postproduction tuning of demineralizer regimes have been demonstrated: recuperation of part of the energy of the dischargeable CDI cell to a chargeable one, reduction in the discharge period due to the application of reverse polarity voltage pulses, and rise in the efficiency by organizing the procedure of taking account of the actual voltage on working electrodes inside the CDI cell. The potential for raising the output of the desalinator has been indicated. [ABSTRACT FROM AUTHOR]

• A modified configuration for the energy-efficient adsorption desalination method was proposed. • Internal heat recovery achieved within the proposed multi-cycle system. • Considerable amounts of cooling production with two temperature levels were delivered. • 20 % rise in SDWP was observed in comparison to a single-cycle configuration. • Full sensitivity analyses of the system parameters were carried out. Due to the drawbacks of conventional methods of desalination, the adsorption desalination system has been introduced as a replacement with several advantages such as capability of using low-grade waste heat, low cost, and production of cooling as its second output. The aim of the paper is to provide a conceptual theoretical framework based on new advanced adsorption desalination and cooling system configured of double-cycle multi-bed dual-evaporator with internal heat recovery. As an innovative approach, the cycles are coupled through integrated equipment, working as a condenser for one of the cycles and a high-pressure evaporator for the other one. System performance is investigated in terms of specific daily water production (SDWP), low and high-pressure cooling capacities (SCPLP and SCPHP), and overall conversion ratio (OCR). It is shown that not only SDWP of the proposed configuration increases by 20% in comparison to the single-cycle multi-bed dual evaporator system, but also it is capable of producing considerable amounts of two grades of cooling water. The proposed configuration with 9.6 m3 of SDWP along with 24 and 25 Rton/ton of high and low-grade cooling capacities could be a suitable alternative to conventional configurations of adsorption desalination. Furthermore, a full sensitivity analysis is carried out by manipulating several system parameters, and the system performance is evaluated. [ABSTRACT FROM AUTHOR]

A new practical application of the unique sorption abilities of Diatomaceous Earth (DE) or diatomite, a widely accessible and promising natural mineral, has been studied. By analyzing aqueous extracts of natural diatomite, it was shown that DE probably contains various inorganic salts, which are released into the solution in the form of ions, such as Cl-, SO4 2-, Na+, Ca2+, Mg2+, K+ and, apparently, others. Diatomite was able to exchange these ions with the environment, exhibiting the properties of a natural ion exchanger. Studying the kinetics of ion release from diatomite showed that the ion desorption process continues for 4-5 h until the surrounding solution is saturated with ions, after which it is dynamically balanced by the sorption process. In order to significantly reduce the ionic content of diatomite, DE samples were processed in a technologically simple and environmentally friendly way. Thus, as a result of deionization, the content of ions released from diatomite significantly decreases. Deionized diatomite was applied to study the adsorption of sodium and chloride ions from aqueous solutions. The maximum adsorption was 50.2 mg/g, and the maximum degree of extraction, corresponding to the concentration range of 5?100 mg/l, was 53.9%. The observed effect was also applicable for increasing the resistance of plants to salt stress, improving the germination and growth of wheat samples. The developed method can be used in the manufacturing of filters for water desalination, both drinking and technological; in ecology; in agriculture to reduce salt stress of plants, as well as for the restoration of lands contaminated by salt. [ABSTRACT FROM AUTHOR]

In this work, the interactions between simple carbon nanotubes (CNTs) and doped carbon nanotubes (DCNTs; with sulfur, boron, aluminum, silicon, phosphorus, or nitrogen) as good adsorbents with various ions such as Fe2 +, Na +, Ca2 +, Mg2 +, Cl−, CO32−, SO42−, and NO3− were fully considered through density functional theory (DFT), natural bond orbital (NBO), quantum theory of atoms in molecules (QTAIM) calculations. The adsorption energies (Ead) demonstrated that these ions could be adsorbed on the surface of the CNTs and DCNTs via the exothermic process, especially in the gas phase. QTAIM analysis confirmed that there are non-covalent interactions between these ions and CNT or DCNTs. The calculated energies illustrated that Si-CNTs and B-CNTs have the highest Ead values in the gas and solvent phase, respectively. Moreover, CNTs had the least Ead values in both phases and the best ion with the minimum Ead value in both phases is iron. Finally, population analyses were performed to obtain the reactivity parameters, molecular properties, bonding structural, and density of states (DOS) plots of all structures. [ABSTRACT FROM AUTHOR]

Membrane capacitive deionization (MCDI) is a modification of capacitive deionization (CDI) using ion-exchange membranes (IEM) in front of the electrodes. Electrode properties, especially the specific surface area, are known to be strongly related with desalination performance in CDI, but the effects of other properties in MCDI are not fully understood. The objective of this study was to investigate the effect of hydrophilicity in activated carbon electrodes on desalination performance in MCDI. Two types of activated carbon (P60 and YS-2) whose specific surface areas were similar were used as electrode materials, but they had different hydrophilicity (i.e., P60 was originally hydrophobic and YS-2 was relatively hydrophilic due to its nitrogen-containing surface chemistry). These hydrophilic electrodes (either the electrode itself or modified with polydopamine (PDA)) led to an increase in the salt adsorption capacity (SAC) in MCDI because they facilitated the access of both ions and water molecules into the electrode pores. In particular, the SAC of the P60 electrode displayed a large increase to almost reach that of the YS-2 electrode due to the improved hydrophilicity with PDA modification and the insignificant effects of PDA modification on an already hydrophilic YS-2 electrode. Additionally, PDA-modified IEM in MCDI reduced the SAC as a result of the additional insulating PDA layer with little changes in hydrophilicity. [ABSTRACT FROM AUTHOR]

• The UCDI system synchronously removes foulants and salt from wastewater. • The UCDI system possesses enhanced antifouling performance. • The UCDI system achieved a 100% removal of foulants via electro-catalytic oxidation. • The foulants hinder the electrosorption of Na+- and K+-based ion pairs. The crises of water scarcity and energy shortage evoked a desire for compact and energy-efficient water treatment technologies. The present study proposed a novel integrated ultrafiltration–capacitive-deionization (UCDI) process, which achieved a simultaneous removal of organic matter and inorganic salts from wastewater. The organic matter was removed through size exclusion (by the ultrafiltration component) and/or electro-catalytic oxidation, while the inorganic salts were retained via electrosorption by the CDI component. Systematic experiments were conducted to investigate the UCDI behavior. Consequently, the UCDI process achieved an enhanced antifouling performance in both the ultrafiltration and CDI aspects. Besides, the organic matter facilitated the removal of Ca2+- and Mg2+-based ion pairs probably via complexation interaction, but hindered the electrosorption of Na+- and K+-based ion pairs due to site competition. During the desalination, the UCDI system could achieve an up to 100% removal of foulants through electro-catalytic oxidation, suggesting promising applications in various areas. [ABSTRACT FROM AUTHOR]