Water Desalination Technique Research Articles

The Effect of Hydrogen as a Coolant on the Characteristics of Humidification-Dehumidification Desalination Systems

The air humidification-dehumidification (HDH) technique for water desalination can be useful in many water production applications. Researchers from all around the world have examined various implementations of this technology to improve it. The present research investigates the effect of three dehumidifier coolants on the system. These coolants include water, helium, and hydrogen. The impact of these coolants on the parameters of the humidification-dehumidification desalination system will be discussed. The investigation’s parameters are tested at various mass ratios, air flow rates, and air outlet heaters. The results show that when hydrogen is employed as a dehumidifier coolant, the gained output ratio (GOR) achieves its peak of 6.37 in the considered mass ratio range of 2.1 to 3. On the other hand, when hydrogen is utilized as a dehumidifier coolant, the system produces the maximum entropy, with the dehumidifier contributing the most. When the mass ratio changes from 2 to 3, the average entropy generation for the system using hydrogen in the dehumidifier increases by 3.8 and 2.9 times, respectively, compared to the average entropy generation for the system using water and helium. However, when hydrogen is used as a dehumidifier coolant, safety concerns must be addressed, as well as the size and cost of heat exchangers in comparison to water.

Fabrication of PVDF membranes via VIPS-NIPS technique for water desalination: Effect of preparation condition

The operating cost of the desalination process can be decreased by using the membrane distillation (MD) process due to very low operating pressure and mild operating temperature. Attempts to find the proper membrane for application in MD attract the attention of many researchers. In this paper, PVDF powder was employed for assembling membranes via the VIPS method for operating in air-gap membrane distillation (AGMD). The influence of the ethanol concentration in the coagulation bath and VIPS time was studied. PVDF membrane characteristics were analyzed via pore size distribution, volumetric porosity, thickness, scanning electron microscope (SEM), measuring water contact angle, water flux, and salt rejection. A nodular structure was found for the membranes resulting from delayed demixing and solid-liquid phase separation. Moreover, the results indicated a larger membrane pore size was formed and the hydrophobicity was improved. The hydrophobicity and pore size are two important factors for membrane distillation that can affect and enhance membrane permeability. Moreover, studying the influence of nanoparticles showed that SiO2 nanoparticles are more effective than TiO2. The highest water contact angle was obtained when SiO2 nanoparticles were sprayed on the surface resulting in higher permeability and salt rejection in AGMD. The AGMD experiments' results showed that the membrane permeability increased from 0.3 to 2.41 L/m2.h, and salt rejection over 99.5 % was obtained.

Water desalination, and energy consumption applications of 2D nano materials: hexagonal boron nitride, graphenes, and quantum dots

Abstract In this article, we explore the role of nanotechnology in addressing water scarcity through water desalination. The scope of nanotechnology in water treatment is discussed, emphasizing the potential of 2D nanomaterials such as hexagonal boron nitride (h-BN), graphene, and quantum dots in revolutionizing desalination technologies. Various water desalination techniques, including membrane distillation (MD), solar-powered multi-stage flash distillation (MSF), and multi-effect distillation (MED), are analyzed in the context of nanomaterial applications. The review highlights the energy-intensive nature of conventional water treatment methods and underscores nanomaterials’ potential to enhance efficiency and sustainability in water desalination processes. Challenges facing desalination, such as scalability and environmental impact, are acknowledged, setting the stage for future research directions.

Impact of chloride salts on TBAB/Methane and TBAB/Carbon dioxide semiclathrate hydrates: Application to desalination

As water consumption increases due to industrialization and global population growth, climate change and urbanization exacerbate the limited available freshwater resources. To counter the challenge water desalination has been used to provide potable water that is ready for human consumption. However, most of the existing water desalination techniques have persistent drawbacks despite decades of development. Thus, a need for efficient and sustainable techniques is urgent. One of the emerging water desalination techniques is hydrate-based desalination. While clathrate has been a nuisance in the oil and gas industry, it has been investigated in several applications including water desalination. This work investigates thermodynamic effectiveness of two hydrate formers in the presence of chloride salts. Methane or carbon dioxide with Tetra n‑butyl ammonium bromide have been used as formers. While the presence of salts depresses the pressure effect on semiclathrate equilibrium on the tested range, it does not have a clear effect at low TBAB concentration. Thus, based on this study using a low concentration of TBAB (20 wt%) with low to moderate pressure of carbon dioxide would yield the most favorable thermodynamic conditions for hydrate-based desalination.

Polyaniline/activated carbon composite based flowing electrodes for highly efficient water desalination with single-cycle operational mode

Flow-electrode capacitive deionization (FCDI) is a promising technique for water desalination and has received considerable attention. The desalination efficiency of FCDI is significantly influenced by the flowing electrode material. Therefore, it is necessary to develop highly efficient flowing electrode materials to obtain excellent desalination capability. Polyaniline (PANI) is regarded as a promising pseudocapacitive material with high conductivity and desirable hydrophilicity. Herein, in order to improve the stability of PANI, a rod-like polyaniline loaded on activated carbon (AC) was prepared by a simple in-situ polymerization to obtain the PAC composite for FCDI electrode. The composite successfully combined the characteristics of AC and polyaniline. The desalination performance of PAC composite for FCDI single-cycle mode was explored, and the mechanism was ascribed to the synergy between electric-double layer capacitance of AC and pseudocapacitance of PANI. The PAC-9 composite with the best electrochemical performance achieved a salt removal efficiency of 94.3 % and an average salt removal rate of 0.963 μmol cm−2 min−1 at 1.2 V. In addition, the PAC-9 composite did not decay after 12 h of long-term operation, showing that the composite is a promising active material for water desalination.

One-step fabrication of soot particle-embedded fibrous membranes for solar distillation using candle burning-assisted electrospinning

Solar distillation, a promising technique for water purification and desalination, requires photothermal materials to efficiently convert solar energy into heat. In this study, a novel method is proposed wherein fresh carbonaceous (soot) particles, as a photothermal material, are embedded into electrospun fibrous membranes by burning candles (to produce soot) and electrospinning of polymer material simultaneously. The proposed method can produce several types of membranes with various particle positions (interior or exterior) in the polymer fiber. The particle positions were adjusted by changing the introduction points of particles using a polymer jet. Polymer fibers with diameters of several hundred nanometers were fabricated. Experiments revealed that the soot particle position did not influence the photothermal conversion performance of the membranes. The fabricated membrane could improve the heat localization up to 194.5% and exhibited water distillation and desalination rates as high as 1.60 and 1.55 kg m−2h−1, respectively, under 1-sun solar light irradiation. The proposed method opens a new route for the functionalization of polymer membranes.

Boosted brackish water desalination and water softening by facilely designed MnO2/hierarchical porous carbon as capacitive deionization electrode

Capacitive deionization (CDI) is a promising technique for brackish water desalination. However, its salt electrosorption capacity is insufficient for practical application yet, and little information is available on hardness ion (Mg2+, Ca2+) removal in CDI. Herein, hierarchical porous carbon (HPC) was prepared from low-cost and renewable microalgae via a simple one-pot approach, and both MnO2/HPC and polyaniline/HPC (PANI/HPC) composites were then synthesized using a facile, one-step hydrothermal method. Compared with the MnO2 electrode, the MnO2/HPC electrode presented an improved hydrophilicity, higher specific capacitance, and lower electrode resistance. The electrodes exhibited pseudocapacitive behaviors, and the maximum salt electrosorption capacities of MnO2/HPC-PANI/HPC CDI cell was up to 0.65 mmol g−1 NaCl, 0.71 mmol g−1 MgCl2, and 0.76 mmol g−1 CaCl2, respectively, which were comparable and even higher than those of the previously reported CDI cells. Additionally, the MnO2/HPC electrode presented a selectivity order of Ca2+ ≥ Mg2+ > Na+, and the divalent cation selectivity was found to be attributed to their stronger binding strength in the cavity of MnO2. Multiscale simulations further reveal that the MnO2/HPC electrodes with the unique luminal configuration of MnO2 and HPC as supportive framework could offer a great intercalation selectivity of the divalent cations and exhibit a great promise in hardness ion removal.

Desalination of produced water via CO2 + C3H8 hydrate formation

Recent years have seen increased interest in gas hydrate production as a viable saline water desalination technique. Produced water is the liquid that is extracted from oil and gas fields and is typically salty. The management of produced water is a significant aspect of the petroleum industry because of its potential to serve as a source of fresh water for oil-producing nations with limited access to clean water, growing environmental concerns, and the strict laws governing the discharge of produced water into the environment. In this study, the effect of mixed gas (CO2 + C3H8 (70:30)) hydrate formation in treating produced water and kinetic studies on induction time, moles of gas consumed, rate, water recovery, and water-to-hydrate conversion were experimentally investigated. An aqueous solution with the same ion concentrations was prepared and experiments were performed at 275.15 K/277.15 K, 2.0 MPa, and 450 rpm. The findings unveiled that with an increase in salinity, the water recovery decreased showing the hindering effect of salts on mixed hydrate formation by reducing the solubility of mixed gas due to the strong electrostatic force of attraction between salt ions and water. A maximum of 67.3% water recovery was observed in 2.8 wt% produced water solution at 275.15 K, 2.0 MPa, and 450 rpm. Furthermore, the induction time increased by 52.64% in treating 2.8 wt% and a decrease in moles of gas consumed, water recovery, and water-to-hydrate conversion by 6.99%, 2.08%, and 9.69% compared to the deionized water system at 275.15 K. A removal efficiency of 47%-63% is achieved by using CO2 + C3H8 and the sequence of metal cation removal is in the order K+ > Na+ > Mg2+ > Ca2+ and anions SO42− > Cl− at 275.15 K. The results also showed that with a rise in the experimental temperature to 277.15 K the removal efficiency increased though the amount of hydrate formed is less. This study illustrates that the formation of mixed gas (CO2 + C3H8) hydrate can be used for treating produced water based on the water recovery, removal efficiency, electrical conductivity, and total dissolved solids results with lower energy consumption.

Modeling the Phase Transition in Hydrophobic Weak Polyelectrolyte Gels under Compression.

One of the emerging water desalination techniques relies on the compression of a polyelectrolyte gel. The pressures needed reach tens of bars, which are too high for many applications, damage the gel and prevent its reuse. Here, we study the process by means of coarse-grained simulations of hydrophobic weak polyelectrolyte gels and show that the necessary pressures can be lowered to only a few bars. We show that the dependence of applied pressure on the gel density contains a plateau indicating a phase separation. The phase separation was also confirmed by an analytical mean-field theory. The results of our study show that changes in the pH or salinity can induce the phase transition in the gel. We also found that ionization of the gel enhances its ion capacity, whereas increasing the gel hydrophobicity lowers the pressure required for gel compression. Therefore, combining both strategies enables the optimization of polyelectrolyte gel compression for water desalination purposes.

Poly-p-phenylene as a novel pseudocapacitive anode or cathode material for hybrid capacitive deionization

Hybrid capacitive deionization (HCDI), which consists of one Faradaic and one carbon electrode, has recently developed as a high-efficiency and environmentally friendly water desalination technique. The advancement of HCDI, however, is hampered by a scarcity of high quality Faradaic materials. Here we demonstrated that conducting poly-p-phenylene (PPP) with a coplanar molecular structure of the extended Π-conjugated skeleton can be used as a reversible electrode material to capture either cations (Na+, K+, Ca2+) or anions (Cl−, F−, NO3−, and SO42−) from various salt solutions. This is benefited from its broad potential window and n−/p-doping characteristics. The desalination performance of PPP was evaluated systematically with the constructed HCDI cells in different electrolytes, which can deliver excellent salt adsorption capacity, charge efficiency, and long-term cycling stability. Further, based on complex capacitance analysis, the kinetic features and mechanism for the ion insertion-adsorption processes were further elucidated, which offers both a new perspective for understanding the salt removal performance of PPP and a practical method for investigating other pseudocapacitive intercalation materials.

Carbon Material-Based Flow-Electrode Capacitive Deionization for Continuous Water Desalination

Flow-electrode capacitive deionization (FCDI) offers an electrochemical, energy-efficient technique for water desalination. In this work, we report the study of carbon-based FCDI, which consists of one desalination chamber and one salination chamber and applies a carbon nanomaterials-based flow electrode that circulates between the cell anode and cathode, to achieve a fast, continuous desalination process. Five different carbon nanomaterials were used for preparing the flow electrode and were studied for the desalination performance, with properties including average salt removal rate (ASRR), salt removal efficiency (SRE), energy consumption (EC) and charge efficiency (CE) being quantitatively determined for comparation. Different FCDI parameters, including carbon concentration and flow rate of the flow electrode and cell voltage, were investigated to examine the influences on the desalination. Long-term operation of the carbon-based FCDI was evaluated using the optimal results found in the conditions of 1.5 M concentration, 1.5 V cell voltage, and 20 mL min−1 flow rate of electrode and water streams. The results showed an ASRR of 63.7 µg cm−2 min−1, EC of 162 kJ mol−1, and CE of 89.3%. The research findings validate a good efficiency of this new carbon-based FCDI technology in continuous water desalination and suggest its good potential for real, long-term application.

Machine learning modelling of a membrane capacitive deionization (MCDI) system for prediction of long-term system performance and optimization of process control parameters in remote brackish water desalination

Membrane Capacitive Deionization (MCDI) is a promising electrochemical technique for water desalination. Previous studies have confirrmed the effectiveness of MCDI in removing contaminants from brackish groundwaters, especially in remote areas where electricity is scarce. However, as with other water treatment technologies, performance deterioration of the MCDI system still occurs, hindering the stability of long-term operation. Herein, a machine learning (ML) modelling framework and various ML models were developed to (i) investigate the performance deterioration due particularly to insufficient charging/discharging of the electrode caused by accumulation of ions and electrode scaling and (ii) optimise MCDI operating parameters such that the impacts of these deleterious effects on unit performance were minimized. The ML models developed in this work exhibited a prediction accuracy of cycle time with average mean absolute percentage error (MAPE) values of 16.82% and 16.09% after 30-fold cross validation for Random Forest (RF) and Multilayer Perceptron (MLP) models respectively. The pre-trained ML model predicted different declining trends of water production for two different operating conditions and provided corresponding recommendations on frequencies of chemical cleaning. A case study on the adjustment of operating parameters using the results suggested by the optimization ML model was conducted. The model validation results showed that the overall water production and water recovery of the system using the cycle-based optimized process control parameters (SCN 1) exceeds the MCDI system performance under three fixed parameter settings that were used at each stage of SCN 1 by 1.78% to 4.48% and 2.95% to 9.46%, respectively. Permutation-based and Shapley additive explanation (SHAP) coefficients were also employed for variable importance (VIMP) analysis to uncover the “black-box” nature of the ML models and to better understand the various features’ contributions to overall MCDI system performance.

Analysis of Boron Removal By Capacitive Deionization

Climate change and water overextraction are some of the reasons for a growing global water stress, with seawater desalination being the leading solution worldwide. The state-of-the-art technology for seawater desalination is reverse osmosis (RO), utilizing mechanical pressure to push seawater through membranes, leaving the dissolved species in the brine. However, boron, which is considered toxic in high concentrations, is poorly removed by RO. This is because under normal conditions boron is present as boric acid, a small neutrally-charged compound. The most common technique to overcome this problem includes multiple RO stages combined with chemical dosage of the effluent, ensuring boron is present as borate, a charged species, present in high pH conditions.Capacitive deionization (CDI) is an emerging membraneless technique for water treatment and desalination, based on electrosorption of salt ions into microporous electrodes. Large internally-generated pH gradients develop during CDI operation, and thus CDI can potentially remove boron without chemically adjusting the feed pH. Here, we present a novel theoretical framework predicting the adsorption of boron in micropores, while considering pH-dependent chemical surface groups in the micropores, ion transport in the macropores, and local electrolyte pH. Moreover, we account for association and dissociation reactions of boron-consisting compounds in the electrolyte[1].We analyzed the effects electrodes order have on pH dynamics, where panels a. and b. in the attached figure present spatiotemporal plots of the pH for the case where cathode is placed upstream (panel a., cat-an) and the anode placed upstream (panel b., an-cat). This analysis shows that higher pH in the anode are expected for the an-cat configuration, counter to common-wisdom in the field. Panel c. follows this trend, by presenting the removed boron as a function of scaled flow velocity for both configurations. The results show, both experimentally and theoretically, that an-cat configuration should be preferred. Similarly, we found that an optimum charging voltage exists, even without accounting for parasitic reactions. Moreover, we found that also the discharging voltage significantly affects boron removal. Overall, CDI is a promising technology for boron removal, but a deep theoretical understanding of the problem is crucial towards future optimization.

Anti-biofouling photothermal film for solar steam generation based on oxygen defects rich and haloperoxidase mimic active V6O13

As a promising sea water desalination technique, solar evaporation has attracted massive attention. But in solar steam generation system, the photothermal film often becomes invalid because of bio-fouling. Haloperoxidase is an ideal choice to reverse this situation, which can catalyze conversion from Br- to HBrO and prevent adhesion of microorganism directly. Herein, oxygen defect rich V6O13 with high photothermal conversion efficiency and haloperoxidase mimic activity is synthesized. As confirmed by Density Function Theory calculations, oxygen defect can strengthen adsorption of V6O13 towards H2O2 and Br-, which enhances haloperoxidase mimic activity greatly. Oxygen defect rich V6O13 also exhibits excellent photothermal conversion property. A photothermal film is fabricated from oxygen defect rich V6O13 and polyacrylonitrile with electrospinning technique. Under 1 ​kW ​m−2, its evaporation rate reaches 1.25 ​kg ​m−2 ​h−1 with efficiency of 85.3%. The concentrations of Na+, K+, Ca2+ and Mg2+ have satisfied the standard of drinking water. More importantly, haloperoxidase mimic activity endows the film perfect anti-biofouling ability and suitable for long time water evaporation in marine environment. It can be expected photothermal film with anti-biofouling ability will exhibits a promising prospect in seawater desalination and sewage treatment.

Recent progress in materials and architectures for capacitive deionization: A comprehensive review.

Capacitive deionization is an emerging and rapidly developing electrochemical technique for water desalination across the globe with exponential growth in publications. There are various architectures and materials being explored to obtain utmost electrosorption performance. The symmetric architectures consist of the same material on both electrodes, while asymmetric architectures have electrodes loaded with different materials. Asymmetric architectures possess higher electrosorption performance as compared with that of symmetric architectures owing to the inclusion of either faradaic materials, redox-active electrolytes, or ion specific pre-intercalation material. With the materials perspective, faradaic materials have higher electrosorption performance than carbon-based materials owing to the occurrence of faradaic reactions for electrosorption. Moreover, the architecture and material may be tailored in order to obtain desired selectivity of the target component and heavy metal present in feed water. In this review, we describe recent developments in architectures and materials for capacitive deionization and summarize the characteristics and salt removal performances. Further, we discuss recently reported architectures and materials for the removal of heavy metals and radioactive materials. The factors that affect the electrosorption performance including the synthesis procedure for electrode materials, incorporation of additives, operational modes, and organic foulants are further illustrated. This review concludes with several perspectives to provide directions for further development in the subject of capacitive deionization. PRACTITIONER POINTS: Capacitive deionization (CDI) is a rapidly developing electrochemical water desalination technique with exponential growth in publications. Faradaic materials have higher salt removal capacity (SAC) because of reversible redox reactions or ion-intercalation processes. Combination of CDI with other techniques exhibits improved selectivity and removal of heavy metals. Operational parameters and materials properties affect SAC. In future, comprehensive experimentation is needed to have better understanding of the performance of CDI architectures and materials.

Particle size distribution influence on capacitive deionization: Insights for electrode preparation

As freshwater shortage has become a global issue, water desalination technique is of great importance to meet the increasing demand for freshwater resources of human beings. Capacitive deionization (CDI) has attracted significant attention in the current desalination technology portfolio. This is because of the use of low-cost electrode materials and the promise of high energy efficiency when including the energy recovery process. CDI, which has its advantage for applying low ionic strength by using various materials, has been explored to improve the system's performance. However, very few have addressed the importance of proper parameter designs, especially the electrodes. In our work, the same activated carbon of different average particle sizes has been studied by applying different desalination parameters (flow rate, holding time, salt concentrations). Our data show that larger particles limit intraparticle ion transportation because of the increased diffusion path length. We also see that a higher packing density, often favored by smaller particles or distribution of particle sizes, is detrimental to interparticle ion transportation. Our work addressed the importance of proper electrode and desalination parameter design for higher desalination performances.

Synthesis and Characterization of Activated Carbon Co-Mixed Electrospun Titanium Oxide Nanofibers as Flow Electrode in Capacitive Deionization.

Flow capacitive deionization is a water desalination technique that uses liquid carbon-based electrodes to recover fresh water from brackish or seawater. This is a potential second-generation water desalination process, however it is limited by parameters such as feed electrode conductivity, interfacial resistance, viscosity, and so on. In this study, titanium oxide nanofibers (TiO2NF) were manufactured using an electrospinning process and then blended with commercial activated carbon (AC) to create a well distributed flow electrode in this study. Field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and energy dispersive X-ray (EDX) were used to characterize the morphology, crystal structure, and chemical moieties of the as-synthesized composites. Notably, the flow electrode containing 1 wt.% TiO2NF (ACTiO2NF 1 wt.%) had the highest capacitance and the best salt removal rate (0.033 mg/min·cm2) of all the composites. The improvement in cell performance at this ratio indicates that the nanofibers are uniformly distributed over the electrode’s surface, preventing electrode passivation, and nanofiber agglomeration, which could impede ion flow to the electrode’s pores. This research suggests that the physical mixture could be used as a flow electrode in capacitive deionization.

Direct contact membrane distillation (DCMD) process for simulated brackish water treatment: An especial emphasis on impacts of antiscalants

Membrane distillation (MD) has been considered as a promising technique for brackish water desalination, while the membrane fouling issue, especially the membrane scaling, have been the main obstacle for the widespread application of MD system. Antiscalant, as an economical tool for scaling control, has been widely applied to other membrane separation processes, like RO and UF. Therefore, three types of typical antiscalants, including PBTCA, DTPMPA, and HPMA, were applied in this work to investigate their anti-scaling performances during the MD desalination of brackish water. Additionally, the impacts of antiscalants on fouling layer development as well as the desalination efficiency of MD system were also deeply researched in this study. Compared to DTPMPA, PBTCA and HPMA performed better scaling inhibition in MD system, resulting in remarkable mitigation of flux decline. With the usage of PBTCA, these mineral substances were largely distributed in feed solutions with the dissolved state, partly facilitating the biofilm formation. Differently, these salts mainly existed in the form of distorted slags with the presence of HPMA, and the biofilm development was notably retarded by the deposited slags. These loose slags could be easily removed from the MD membrane by increasing the feed flow velocity, thus it can be summarized that HPMA was more suitable for the long-period MD desalination of brackish water. The application of DTPMPA should be strictly restricted in MD desalination units considering the risk of pore wetting.

In situ potential measurement in a flow-electrode CDI for energy consumption estimation and system optimization

Flow electrode capacitive deionization (FCDI) is a promising electrochemical technique for brackish water desalination; however, there are challenges in estimating the distribution of resistance and energy consumption inside a FCDI system, which hinders the optimization of the rate-limiting compartment. In this study, energy consumption of each FCDI component (e.g., flow electrodes, membranes and desalination chamber) was firstly described by using in situ potential measurement (ISPM). Results of this study showed that the energy consumption (EC) of the flow electrodes dominated under most conditions. While an increase in the carbon black content in the flow electrodes could improve the energy efficiency of the electrode component, consideration should be given to the contribution of ion exchange membranes (IEMs) and the desalination chamber to the EC. Based on the above analysis, system optimization was carried out by introducing IEMs with relatively low resistance and/or packing the desalination chamber with titanium meshes. Results showed that the voltage-driven desalination capability was increased by 39.3% with the EC reduced by 17.5% compared to the control, which overcame the tradeoff between the kinetic and energetic efficiencies. Overall, the present work facilitates our understanding of the potential drops across an FCDI system and provides insight to the optimization of system design and operation.

Quaternary Ammonium-Based Ionosilica Hydrogels as Draw Solutes in Forward Osmosis.

In the last few years, forward osmosis (FO) has attracted increasing interest as a sustainable technique for water desalination and wastewater treatment. However, FO remains as an immature process principally due to the lack of efficient and easily recyclable draw solutes. In this work, we report that ionosilica hydrogels based on quaternary ammonium halide ionosilica are efficient draw solutes in FO. Fluidic ionosilica hydrogels were obtained via hydrolysis-polycondensation reactions of a trisilylated quaternary ammonium precursor in slightly acidic water/ethanol solvent mixtures. The liquid-to-gel transition of the precursor and the kinetics of the formation of hydrogels were monitored by liquid NMR measurements. The formed hydrogels were shown to generate osmotic pressure up to 10.0 atm, indicating the potential of these hydrogels as efficient draw solutes in FO. Our results suggest that iodide anions are the osmotically active species in the system. Regeneration of the hydrogels via ultrafiltration (UF) was successfully achieved, allowing the development of a closed FO-UF process. However, the osmotic performances of the ionosilica hydrogels irreversibly decreased along the successive FO-UF cycles, probably due to anion exchange processes.