Salt Adsorption Research Articles

Assessment of simultaneous removal of salt and dye by utilizing capacitive deionization and UV-electro oxidation hybrid process in saline wastewater treatment

In this research, the goal was simultaneous elimination of salt (NaCl) and dye (C·I Acid Orange 7 or AO7) through integration of capacitive deionization (CDI) technique with UV-based electrochemical advanced oxidation process (UV-EAOP). To optimize salt adsorption capacity (SAC) of MnO2 electrode, Taguchi's experimental design methodology was employed to fine-tune synthesis parameters, including bath temperature, current density, and precursor concentrations. BiOCl was synthesized and implemented as an anode to bolster AOP's effectiveness. Several experiments were conducted to analyze the effects of applying the combined AOP and CDI. The findings revealed that parameter optimization improved SAC, and the application of UV irradiation decreased electrode's SAC. Furthermore, it was observed that AO7 could enhance SAC while lowering salt adsorption rate (SAR). More importantly, the combined application of CDI and AOP resulted in superior pollutant removal efficiency and improved SAC, despite reduced SAR. Finally, color was entirely eliminated after 90 min, and the generated species were recognized by GC–MS. Additionally, a possible pathway for AO7 degradation was suggested based on the generated species.

Porous N, P co-doping Ti3C2Tx MXene for high-performance capacitive deionization

The emerging energy-saving and environmentally friendly capacitive deionization (CDI) technology has attracted more and more attention. However, it remains a great challenge to develop CDI electrode materials with excellent comprehensive properties. Herein, the porous N, P co-doping Ti3C2Tx MXene (N, P-Ti3C2Tx) was prepared successfully by combining simple flocculation with an annealing process. Benefitting from the synergistic effect of the combination of porous structure and co-doping of N and P heteroatoms, the N, P-Ti3C2Tx exhibits substantial specific surface area, which provides more surface bounding active sites for electrochemical reactions, thus assisting to boost the CDI performance. As a result, the N, P-Ti3C2Tx exhibited an admirable salt (Na+) adsorption capacity of 53.3 mg g−1 and exceptional recycling property. Impressively, the N, P-Ti3C2Tx also exhibited superior desalination performance of Pb2+, characterized by an exceptionally high desalination capacity of up to 168.2 mg g−1 at 1.2 V, and the corresponding desalination rate reached 0.047 mg g−1 s−1. Additionally, the deionization mechanism involved was elucidated through a series of characterizations. This work will furnish an effective avenue for the innovative design of MXene-based electrode materials toward high-performance CDI.

Fluoride removal using membrane capacitive deionization: The role of pH-dependent dissolved inorganic carbon

Defluorination technology is crucial for ensuring safe and accessible water. The application of capacitive deionization (CDI) technology faces challenges due to competitive adsorption of fluoride ions within complex natural fluoride-rich brackish water matrices, which often contain high levels of dissolved inorganic carbon (DIC) species (mainly HCO3– and CO32–). These DIC species are pH-dependent, playing a significant role in the selective removal of fluoride by the CDI process. Thus, there is a knowledge gap in understanding the effects of membranes in membrane capacitive deionization (MCDI) on fluoride removal. In this study, we examined the key operating parameters in CDI and MCDI, including applied constant voltages and different types of anion-exchange membranes (AEMs), on the desalination performance in F- and dissolved inorganic carbon water matrices. The application of AEMs significantly improved the salt adsorption capacity (SAC) for both F- and DIC species, and reduced energy consumption. However, it simultaneously resulted in a notable decrease in F- selectivity as membranes control mass transfer. Higher applied voltages enhance the SAC performance for F- and DIC species, but also induce more severe Faradaic reactions, leading to increased energy consumption and lower energy efficiency. Additionally, ion species and pH changes during CDI and MCDI processes are interrelated, indicating that stability tests of CDI electrodes in batch mode are not reliable when using the same testing solution repeatedly. The diverse valence states of ions in the solution impact pH variations under different voltages in the CDI/MCDI process. These findings provide valuable insights into the development of water purification and desalination technology, particularly for the application and further advancement of selective fluoride removal by the CDI process.

Synergistic chemical traction and pre-intercalation strategies enable high-quality MnO2 composites for efficient ammonium capture

The δ-MnO2 exhibits an ideal capacitive deionization (CDI) electrode for the efficient removal of ammonium ions (NH4+), owing to its unique layered structure that facilitates effective insertion and extraction of ions. However, MnO2 is constrained by self-aggregation, inadequate electrical conductivity, and sluggish reaction kinetics in practical applications, leading to subpar ammonium removal performance. Here, the polyaniline (PANI) intercalated MnO2 and carbon nanotubes (CNTs) composites (P/M-C-X) were synthesized by a straightforward and swift one-step inorganic/organic interface reaction using the chemical traction effect of aniline. The synergistic effect of the increased layer spacing and the introduced oxygen vacancy after PANI intercalated and the 1D/2D conductive interconnect structure constructed by CNTs can effectively improve the electrical conductivity, promote ions/electrons diffusion, and enhance the charge reaction kinetics. As results, P/M-C-50 exhibits excellent NH4+ removal performance, including the maximum salt adsorption capacity (SAC) (160.0 mg g−1), ultra-high salt adsorption rate (SAR) (1.07 mg g−1 s−1), and good cyclic stability. Furthermore, the comprehension of NH4+ storage mechanism has been enhanced through structural characterization, electrochemical analysis, and theoretical calculation. This study shows that P/M-C-50 has broad potential as a CDI ammonium removal electrode, and lays a solid foundation for the effective recovery and reuse of ammonium resources.

Irrigation Water Salinity Affects Solute Transport and Its Potential Factors Influencing Salt Distribution in Unsaturated Homogenous Red Soil

As a promising alternative water source to alleviate irrigation water scarcity in red soil regions in southern China, low-quality water could enhance regional water resource utilization and promote sustainable agriculture. However, its soluble salt and ions could affect soil solute distribution and transport, potentially hindering crop growth. Undoubtedly, it is necessary to understand the mechanism of solute transport in red soil under low-quality water irrigation with different water salinity levels. Therefore, a one-dimensional vertical water infiltration experiment and a solute breakthrough experiment were conducted to evaluate the solute transport (soluble salt, Na+, and Cl−) in unsaturated and saturated homogenous red soil at different salinity levels [1 (S1), 2 (S2), 3 (S3), 5 (S5), and 10 (S10) g/L] when irrigated with simulated low-quality water using analytical-grade NaCl. Moreover, the potential factors affecting salt distribution in unsaturated red soil were determined. The findings indicate positive linear relationships between accumulations of three solutes and irrigation water salinity. Generally, the depth of maximum solute concentration increased with the increase in irrigation water salinity. Soluble salt, Na+, and Cl− exhibited early breakthrough and trailing in red soil, but higher irrigation water salinity could reduce PV and retardation. A mobile and immobile water model (MIM) showed that convection was dominant in solute transport in red soil under low-quality water irrigation. D decreased as a power function with increasing irrigation water salinity, while v and R decreased linearly. Furthermore, the red soil can adsorb Cl− resulting from its special charge characteristics under low-quality water irrigation, which may be the main source of salt adsorption. Additionally, v > soil pH > βsalt primarily influenced salt distribution in the 0–40 cm soil profile. This study can provide insights into solute transport in red soil under low-quality water irrigation, facilitating soil fertility and structure, as well as low-quality water irrigation strategy optimization.

KOH Activated Walnut Shell Biochar Electrode of Capacitive Deionization and Its Desalination Performance

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

Upcycling Waste Polyethylene Terephthalate to Produce Nitrogen-Doped Porous Carbon for Enhanced Capacitive Deionization

Porous carbon with a high surface area and controllable pore size is needed for energy storage. It is still a significant challenge to produce porous carbon in an economical way. Nitrogen-doped porous carbon (N-PC) was prepared through carbonization of a mixture of waste PET-derived metal–organic frameworks (MOFs) and ammonium. The obtained N-PC exhibits a large surface area and controlled pore size. When utilized as an electrode material for supercapacitors, the N-PC exhibits a specific capacitance of 224 F g−1, significantly surpassing that of commercial activated carbon (AC), which has a capacitance of 111 F g−1. In the subsequent capacitive deionization (CDI) tests, the N-PC demonstrated a maximum salt adsorption capacity of 19.9 mg g−1 at 1.2 V in a NaCl electrolyte (0.5 g L−1), and the salt adsorption capacity increased to 24.7 mg g−1 at 1.4 V. The N-PC electrode also exhibited superior regeneration. The present work not only presents a potential approach to develop cost-effective electrodes for seawater purification but also paves the way for recycling of waste plastics into high value-added products.

Capacitive deionization and electrochemical performance of a hierarchical porous electrodes enabled by nitrogen and phosphorus doped CNTs and removable NaCl template

Capacitive Deionization (CDI) is an electrochemical desalination technique based on the electrical double layer, which accumulate salts from the water stream; however, achieving higher salt adsorption for low-concentration salt is hindered due to several obstacles, such as low adsorption capacity and slow kinetics on the electrode surface. In this study, we reported a novel electrode fabrication method designed to enhance the hydrophilicity of the electrode material and activate hierarchical porosity, making a more accessible adsorption surface area. This modification enables more than 210 % improvement in salt adsorption capacity, achieving 17.5 mg g-1 in a single pass process with good stability in an 850 mg/L NaCl solution at 1.2 V, surpassing most reported carbon-based electrodes under similar operating conditions. Electrode formulation consists of Nitrogen (N) and Phosphorus (P) doped hierarchical carbon nanotubes (CNTs) network blended with additional NaCl as a green and removable template to reach higher levels of porosity. The electrochemical sorption behavior of the sample was characterized over a voltage range of –0.5 to 0.7 V. Furthermore, the electrode materials were characterized utilizing various characterization methods, including Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Raman Spectroscopy, Fourier Transformed Infrared (FTIR), X-ray Photoelectron Spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) to explore the correlation between microstructure, morphology, and properties. Our finding reveals that not only N and P can affect adsorption, but also the novel cathode preparation method, which employs a removable NaCl templated hierarchical porous electrode, has a profound effect on the electrochemical and CDI results. This finding will open a new perspective in designing electrodes for all electrochemical systems.

Tailoring iron MOF/carbon nanotube composites as flow electrodes for high-performance capacitive deionization

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

Efficiently removal the lanthanides using electroreduction diffusion method/high-temperature adsorption technique

The consumption of electricity and the price of molten salt are key factors that limit the pyroprocessing of nuclear fuel. This paper proposes a strategy to reduce costs associated with pyroprocessing of spent fuel by combining electrolytic refining and molecular sieve adsorption for fission product removal and radioactive waste salt recovery. Firstly, we investigated the electrochemical process of ytterbium on a gallium film electrode in LiCl-KCl using various methods, calculating its kinetic parameters at different temperatures. Potentiostatic electrolysis experiments were conducted at 773 K, resulting in the formation of Ga-Yb alloy as the electrodeposited product with a ytterbium removal rate reaching 93.78 %. Then, we studied the adsorption behavior and mechanism of ytterbium through electrorefining combined with molecular sieve adsorption. Experimental results showed that the extraction rate achieved more than 99.99 %, significantly reducing electrolysis costs while increasing target nuclide removal rates. Finally, we investigated the molten salt adsorption mechanism using molecular sieves, identifying chemical ion exchange as the primary mechanism based on recalibration using pseudo-first-order, pseudo-second-order, and Weber-Morris kinetic models. In conclusion, combining electrodeposition and high-temperature adsorption provides an effective approach for recovering and utilizing waste salt in pyroprocessing.

Defect-rich N, S Co-doped porous carbon with hierarchical channel network for ultrafast capacitive deionization

Developing an eco-friendly and effective approach for preparing N, S co-doped hierarchical porous carbons (NSHPC) for capacitive deionization (CDI) is a huge task for desalination. Herein, NSHPCSKK with interconnected hierarchical pore structures, manufactured via self-activation/co-activation of sodium lignosulfonate (SLS) encapsulation using KNO3-KHCO3 activators, inducing N, S co-doping. Different from NSHPCS and NSHPCSK, NSHPCSKK exhibits the highest specific surface area (SBET, 2264.67 m2/g) and a unique hierarchical pore structure (mesoporous volume/pore volume (Vmeso/ Vpore), 0.65). Small-angle X-ray scattering (SAXS) and scanning electron microscopy (SEM) both reveal the complex interconnected pore structure of NSHPCSKK. Regional Raman imaging conjugated with XPS reveals the presence of extensively distributed N, S co-doped defect structures, providing NSHPCSKK with excellent wettability and electrochemical performance. DFT calculations indicate that the N, S co-doping at the defect sites depicts excellent adsorption capability. Eventually, NSHPCSKK acquired an impressive salt adsorption capacity (SAC) of 20.5 mg/g and the highest average salt adsorption rate (ASAR) of 12.1 mg/g/min, indicating its superior desalting performance. In-situ Raman spectroscopy confirms NSHPCSKK’s rapid ion regeneration mechanism. The research introduces a span-new NSHPC synthesis strategy for fabricating advanced NSHPC with rapid desalination response for upgrading CDI desalination.

Cork activated carbon as a new sustainable electrode for electrochemical desalination: Customized surface chemistry for improved performance

Capacitive deionization (CDI) desalination has proven to be a promising solution to combat water scarcity, standing out for its efficiency and low energy consumption. In this study we investigated the feasibility and sustainability of using recycled cork stoppers as carbon electrodes for CDI. The cork stoppers underwent carbonization at three different temperatures (500, 700 °C, and 900 °C) and then activation with Potassium hydroxide (KOH) at 850 °C. The as-obtained electrodes (ECAC) demonstrated salt adsorption capacities (SAC) comparable to other biowaste carbon electrodes. The potential of zero charge (EPZC) values of the electrodes reflected the influence of synthesis conditions on their surface properties. Considering the EPZC, symmetric configuration, in which both electrodes (cathode (-) || (+) anode) were made of the same material (ECAC(-)||(+)ECAC), and asymmetric electrodes, using different materials (ECAC(-)||(+)YP80-F) were investigated. The use of asymmetric electrodes proved to be mandatory to obtain high charging efficiency and desalination capacity. It was found that the EPZC determines the correct electrode configuration to prevent the deleterious effect of co-ions repulsion. Herein, we used the carbonization temperature as a new strategy to tune the EPZC in order to obtain electrodes with the desired surface properties for application in CDI, thus avoiding the usual laborious and costly chemical-based approaches. Regarding the desalination performance, asymmetry combined with the appropriate cell potential was optimized to obtain charging efficiencies close to 100 % and maximum SAC, thus resulting in minimized specific energy consumption. This study not only confirms the efficacy of cork stoppers as electrodes for CDI but also promotes the use of recycled materials, contributing to a circular economy and environmental impact mitigation.

Formation of interior hollow nanocubes derived from cobalt-based metal-organic frameworks via one-step etching for efficient battery desalination

Battery desalination (BD) offers a sustainable solution for simultaneous energy storage and desalination, addressing the global need for clean water access. However, current BD technologies require improvements in salt removal capacity, charge efficiency and energy consumption to become practical. In this study, we present a BD system utilizing interior hollow nanocubes derived from a cobalt-based zeolitic imidazolate framework (Co-TA HC) as the cathode and silver nanoparticle on reduced graphene oxide (Ag@rGO) as the anode. The regular and hollow nanocubes, with enhanced specific surface area and abundant redox active sites, are prepared via a simple one-step mild tannic acid (TA) etching process, holding great promise for scalable manufacturing. The unique structure of the Co-TA HC significantly shortens the diffusion length of the Na+ and enhances the sodium intercalation kinetics, as indicated by the galvanostatic intermittent titration technique. The optimal pairing of the Co-TA HC and Ag@rGO enables the full discharge with voltage window of 0–1.4 V in the BD system, achieving high volumetric salt adsorption capacity (SAC) of 102.3 mg cm−3 and gravimetric SAC of 143.2 mg g−1 with a current density of 100 mA g−1. This suggests that the practical application of BD systems is a tangible possibility and paves the way for scaling-up emerging desalination technologies.

The novel α-TiO2@g-C3N4 heterostructure for ultra rapid ionic pumping and effective capacitive deionization

Anatase titanium dioxide (α-TiO2) has been widely identified as an efficient electrode material for capacitive deionization (CDI). However, this material usually suffers from limited exposure of active sites, poor electrical conductivity and significant obstacles in ion movement due to its tendency to severely aggregate during its preparation. A novel approach to fabricate α-TiO2@g-C3N4 composite materials was proposed in this work. In detail, the 2D material g-C3N4 serves as a high-speed electron-conducting scaffold, allowing uniform loading of nanoscale α-TiO2 and exposing abundant active sites. Furthermore, g-C3N4 facilitates electron transport to nanoscale α-TiO2, enhancing charge transfer and activating previously underutilized electrochemical centers. As a result, α-TiO2@g-C3N4 composites were synthesized for the first time. Through these improvements, the prepared α-TiO2@g-C3N4 exhibits excellent desalination performance, with a high degree of efficiency in water purification. It shows an improved salt adsorption capacity (SAC) of 50.4 mg g-1 and a salt adsorption rate (SAR) of 2.7 mg g-1 min−1 in a 1.2 V, 1 mm electrode spacing, and 500 mg L-1 NaCl solution. This outstanding CDI performance surpasses most recently reported electrode materials. More importantly, this electrode showed remarkable removal efficiencies for various heavy metal ions (Ni2+, Cr3+, Cu2+, Pb2+, Fe3+ and Cd2+), indicating its significant potential for wastewater purification. The superior CDI performance of the α-TiO2@g-C3N4 composite material endows it with practical application in future.

Multi-metal-doped transition metal compounds for high-performance asymmetric capacitive deionization

To address the limited ion adsorption capacity of carbon-based capacitive deionization (CDI) which primarily relies on double-layer mechanism, recent efforts have focused on the rational design and development of efficient Faradaic materials for CDI applications. In this study, we synthesized and applied Co- and Mn-doped transition metal compounds (Cu₂O@MCF) as the electrodes for asymmetric CDI using a simple hydrothermal method. The synthesized electrodes were analyzed using various characterization techniques, to confirm the successful doping and structural integrity. Electrochemical performance assessments revealed significant improvements in ion-capture capacity and overall desalination efficiency. Specifically, the optimized asymmetric CDI cell configuration, consisting of Cu₂O@MCF(Cl) as an anode and Cu₂O@MCF(Na) as a cathode, led to a significant increase in salt adsorption capacity (27.42 mg/g) over conventional symmetric carbon electrode (11.22 mg/g), an increase of over 2.4 times. Furthermore, the synthesized electrodes demonstrated effective phosphate ion removal, highlighting their potential applicability in wastewater treatment. The findings suggest that multi-metal doping significantly enhances electrode performance by synergistically combining electric double-layer capacitance and pseudocapacitance effects, due to their unique morphological and electrochemical properties. These results contribute to sustainable water treatment and resource recovery efforts, showcasing the effectiveness of the materials in improving CDI performance and opening new avenues for their application in environmental cleanup and resource management.

Adsorption of bile salts onto crystalline ritonavir particles under simulated gastrointestinal conditions

The formation of a biomolecular corona on nanoparticles in blood is a well-known phenomenon influencing in vivo performance. Analogous phenomena in other biological fluids, such as the formation of a gastrointestinal (GI) corona, remain under-investigated. The ingestion of medicines leads to the generation of drug particles in the GI fluids. Consequently, an understanding of the behavior of drug particles in the gut requires determination of the adsorption of bile components onto these drug particles. This work aims to elucidate the factors affecting adsorption of bile salts onto ritonavir (RTV) particles. Crystalline RTV particles were incubated with non-micellar or micellar bile salts and bile salt depletion from solution was measured using HPLC and small angle X-ray scattering (SAXS). HPLC results show that bile salts adsorb onto RTV particles, with greater adsorption observed for more hydrophobic bile salts, following the order sodium glycodeoxycholate (SGDC)>sodium taurodeoxycholate (STDC)>sodium glycochenodeoxycholate SGCDC>sodium glycocholate (SGC)>sodium taurocholate (STC). Increasing the ionic strength of the solution led to increased adsorption of STDC, where buffer containing 300 mM NaCl resulted in greater adsorption than 150 mM NaCl. Additionally, micellar bile salts showed greater affinity for RTV particles than unimeric bile salts. In contrast, the extent of bile salt depletion was unaltered by addition of phospholipid to form mixed micelles. SAXS analysis of mixed micelles after incubation with RTV particles confirms depletion of bile salt from the supernatant, evidenced by reduced intensity of the micellar scattering feature. In conclusion, this study investigated factors influencing bile salt adsorption onto drug particles, highlighting the need to consider adsorption of bile components in forming the GI-corona.

Insights on CDI parametric controls and dependencies using gloabal sensitivity analysis

Capacitive deionization (CDI) emerges as a promising desalination technology due to its high energy efficiency and potential for energy recovery. Its performance improvement and application extension highly require understanding how variations in multiple input parameters, as well as their interactions, lead to variations in output, which is not straightforward in the complex system of CDI. In this work we use the extended Fourier amplitude sensitivity test (eFAST) method to conduct a global sensitivity analysis (GSA) in order to examine the effects of several parameters, including material properties, operating conditions, and ionic properties, on the energy consumption and salt removal efficiency of CDIs. The research reveals that high capacitance and efficient mass transfer are crucial for CDI advancement, with a trade-off between desalination rate and energy efficiency. The interplay between input parameters is revealed by factorial design and GSA, which show that no single parameter alone determines salt adsorption capacity but that feedwater salt concentration and current density are important when considering both individual and coupled effects. The study suggests that the specific application and feedwater characteristics should be taken into consideration when deciding between the CC and CV modes of desalination. While CC mode excels in water production and energy efficiency for high salinity feedwater pretreatment, CV mode is better at treating low salinity waterr. The comprehensive parametric analysis provides valuable insights into optimizing CDI design and operating conditions to balance desalination capacity and energy efficiency.

High-capacity and high-stability capacitive desalination with dual redox-active MnCo2S4/g-C3N4 heterojunction electrode

Capacitive deionization (CDI) utilizing dual redox-active electrodes has shown significant promise in desalinating low-concentration brackish waters, which is crucial for addressing global freshwater shortages. However, improvements in salt adsorption capacity and long-term operational stability are still required. In this study, we introduce, for the first time, a binary metal sulfide MnCo2S4/g-C3N4 (MCS-CN) heterojunction as a CDI electrode. The innovative integration of dual redox-active centers and heterojunction structures in the MCS-CN composite electrodes underscores their potential for achieving both high capacity and stability in capacitive desalination applications. The microscopic morphology, crystal structure, pore structure, and surface valence properties of the MCS-CN heterojunction composite materials were extensively characterized using various analytical techniques. In-situ X-ray diffraction, refined ex-situ X-ray photoelectron spectroscopy, three-electrode electrochemical analysis, and theoretical calculations were employed to elucidate the electrosorption and desorption mechanisms of sodium ions with the MCS-CN electrodes and to clarify the enhanced desalination performance of the binary metal sulfide-based heterojunction structure. As a result, the optimal MCS-CN-40 electrode exhibited the highest salt removal capacity of 71.64 mg g−1 and maintained stable desalination performance over 100 cycles in a 500 mg L−1 NaCl solution. This innovative approach provides a noval perspective for developing heterojunction electrodes with high redox activity and efficient desalination performance.

Biomimetic mineralization synthesis of tricobalt tetraoxide/nitrogen doped carbon skeleton for enhanced capacitive deionization

Developing novel capacitive deionization (CDI) electrode materials with high salt adsorption capacity and adsorption rate is essential for desalination applications, however, encountering significant challenges. Herein, a facile and energy economical biomimetic mineralization method is proposed to construct the tricobalt tetraoxide/nitrogen doped carbon (Co3O4/NC) heterostructure. Benefiting from the mild biomimetic mineralization process, small Co3O4 nanoparticles grow uniformly on interconnected multi-branched NC skeleton. The as-obtained Co3O4/NC heterostructure exhibits a salt adsorption capacity of 44.5 mg g−1, adsorption rate of 7.9 mg g−1 min−1, and 91.3 % of capacity retention after 60 cycles at 1.2 V in 500 mg L−1 salt solution. These performances overwhelm the bare Co3O4 (24.6 mg g−1, 3.5 mg g−1 min−1, 65.7 %), indicating superior desalination performances of the Co3O4/NC heterostructure. This study gives an insight into the biomimetic mineralization method and provides one promising candidate of CDI electrode.

Innovative dual-mode device integrating capacitive desalination and solar vapor generation for high-efficiency seawater desalination

Solar-driven interface evaporation with high solar-to-steam conversion efficiency has shown great potential in seawater desalination. However, due to the influence of latent heat and condensation efficiency, the water yield from solar-driven interface evaporation remains insufficient, posing a significant challenge that requires resolution. In this work, we designed a dual-mode high-flux seawater desalination device that combines solar-driven interface evaporation and capacitive desalination. By utilizing coupled desalination materials exhibiting both photothermal conversion and capacitance activity, the device demonstrated photothermal evaporation rates of 1.41 and 0.97 kg m−2 h−1 for condensate water yield under one-sun irradiation. Additionally, the device exhibited a salt adsorption capacity of up to 48 mg g−1 and a salt adsorption rate of 2.1 mg g−1 min−1. In addition, the salt adsorption capacity increased by approximately 32% under one-sun irradiation. Furthermore, photo-enhanced capacitive desalination performance was explored through numerical simulations and theoretical calculations. Theoretical calculations and characterizations confirmed that the defect energy levels formed by the introduction of sulfur vacancies can effectively widen the light absorption range, improve photothermal conversion performance, and stimulate more photoelectrons to participate in capacitive desalination. Concurrently, the electron distribution state of molybdenum disulfide with sulfur vacancies and surface defect sites contributes to ion/electron transport at the solid-liquid interface. This work provides a novel pathway for integrating solar vapor generation with other low-energy desalination technologies.