Desalination Efficiency Research Articles

Numerical modeling of ion transport and adsorption in porous media: A pore-scale study for capacitive deionization desalination

A pore-scale model is presented to simulate the dynamic ion transport and adsorption processes in porous electrodes used for capacitive deionization (CDI). The Stokes equation governing water flow is solved using the lattice Boltzmann method and Nernst-Planck equation describing ion transport is solved using the finite volume method. The ion adsorption process is considered at the surface of carbon electrodes. After validation against analytical solutions and published results, the model is used to study the coupled water flow, ion transport and adsorption in both two-dimensional and three-dimensional porous CDI electrodes at the pore scale. The effect of electrode microstructure, electrical potential and flow velocity on the adsorption processes is quantitatively investigated, and the relative importance of various parameters is determined. The presented model can be a powerful numerical tool to quantitatively analyze ion transport and adsorption in porous electrodes, and may provide useful information for the design and optimization of CDI electrodes and operating conditions for desired desalination efficiency, water throughput and cost.

Hybrid PSf/TNT-SO3H Ultrafiltration Membrane Fouling by Sodium Alginate: Effect of Permeation Flux on Fouling Resistance and Desalination Efficiency

The development of low fouling UF membranes with boosting water flux for implementations in water purifications is critical. Organic foulants and ionic strength are the main characteristics of surface water which affect the membrane performance for water generation and seawater desalination. Low fouling hybrid ultrafiltration membranes were fabricated from a combination of sulfonic acid functionalized titanium nanotubes (TNTs-SO3H) and polysulfone (PSf) by the nonsolvent-induced phase separation approach. The membrane fouling was explored utilizing a polysaccharide sodium alginate (SA) as a hydrophilic nature organic matter, and the impact of Na+ and Ca2+ ions on alginate membrane fouling were also addressed. The results showed that the membranes’ water permeability and natural organic matter fouling resistances were affected by the proportion of TNTs-SO3H in the membranes. The inclusion of TNTs-SO3H improves the water penetration fluxes (Jw1) and surface hydrophilicity of the manufactured membranes. In the UF of sodium alginate solution, the produced membrane comprising 5% TNTs-SO3H exhibits a higher penetration flux and rejection value than the other membranes. The introduction of Na+ and Ca2+ ions to the SA solution reduces the membrane fouling. Furthermore, the adsorption investigation of sodium alginate solutions at [Formula: see text] was lowered as the amount of TNTs-SO3H was increased. After ultrafiltration, the fouled membrane containing 5% TNTs-SO3H is readily removed, and recurrent antifouling experiments indicate a consistent and maximum filtration efficiency.

Electric field enhanced in situ silica nanoparticles grafted activated carbon cloth electrodes for capacitive deionization

Activated carbon clothes (ACCs) were modified by in situ deposition of silica nanoparticles (SiO2 NPs) to enhance the dielectric property of ACC surface and used as electrodes in the capacitive deionization (CDI) system. Four different concentrations of tetraethyl orthosilicate precursors were used as silica source and the effect of concentration on the CDI performance was investigated. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analysis revealed the presence of Si-O bonds on the ACC surface and Raman analysis confirmed the graphitic structure of the ACC was intact after grafting with SiO2 NPs. SiO2 NPs coated ACC electrodes revealed better desalination efficiency and average salt removal rate (ASRR) than pristine ACC. Specifically, ACC electrodes coated with 45 mM silica (SiO2-III) exhibited the highest specific capacitance of 97.4 ± 0.1F/g, average desalination efficiency of 70 % with ASRR of 0.075 ± 0.008 mg/cm2/min using 200 ppm NaCl. Moreover, CDI Ragone’s plot verified the highest desalination rate was achieved with 45 mM SiO2 coated ACC electrodes. Furthermore, different salt concentrations and applied potentials upon desalination performances were also investigated. Moreover, post characterization of used pristine ACC and SiO2-III electrodes exhibited the sign of substantial electrode oxidation for pristine ACC but less on SiO2 NPs coated ACC electrodes. SiO2 NPs decorated ACC electrodes were not only enhanced localized electric field around dielectric coating of SiO2 NPs but also prevented the surface oxidation of the electrodes.

The optimized flow-electrode capacitive deionization (FCDI) performance by ZIF-8 derived nanoporous carbon polyhedron

• Nanoporous carbon polyhedron (NCP) with high specific surface was prepared as flow-electrode. • A high salt removal rate of 20.98 μg cm −2 min −1 was obtained in FCDI system. • The increased NCP content can improve the desalination performance. • Desalination performance of NCP can keep stable even after long-time cycles. Flow-electrode capacitive deionization (FCDI) has developed as a promising technology to realize the highly efficient and low-energy-consumed desalination process. To deliver better desalination performance, the flow-electrode with high capacitance and low resistance is essential. As for the traditional AC flow-electrode, although it is low-cost and wide-applied, the relatively low capacitance and poor conductivity are the limitations for its further development. Here, we propose a novel flow-electrode material, nanoporous carbon polyhedron (NCP), which was prepared by ZIF-8 followed by carbonization and activation process and have a higher surface area and larger specific capacitance than AC. The desalination experiments showed that the current density of FCDI system based on NCP is about 2.5 times larger than that of AC, exhibiting a higher desalination rate of 20.98 μg cm −2 min −1 for NCP. Moreover, the desalination energy consumption and efficiency can keep relatively stable after the long-time continuous desalination cycling. This current research may be significant for the future promising application of high-performance FCDI system.

Carbon Based Electrode Materials and their Architectures for Capacitive Deionization

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 them is 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.

TiO2/CDs modified thin-film nanocomposite polyamide membrane for simultaneous enhancement of antifouling and chlorine-resistance performance

In this study, a titanium dioxide/carbon dots (TiO2/CDs) hydrophilic nanocomposite photocatalyst with different contents was embedded in the polyamide layer of reverse osmosis (RO) membrane via interfacial polymerization to increase desalination performance and antifouling properties. The modified membranes showed smoother surfaces with reduced contact angles, causing to improve membrane fouling resistance. TiO2/CDs nanocomposite, due to its photocatalytic activity, showed more flux recovery ratio (FRR) after irradiation of UV light during the washing process. The FRR was enhanced from 94.4 to 97.1% for 0.01 wt% TiO2/CDs RO membrane by UV irradiation. The hydrophilic functional groups with negative charge increased the desalination efficiency of the modified membranes (99.2% NaCl rejection for 0.01 wt% TiO2/CDs membrane). The membrane containing 0.01 wt% TiO2/CDs presented the highest pure water and NaCl solution flux of (59.6 and 54.6 L·m−2·h−1) at 15 bar, respectively. In addition, the used nanoparticles improved the chlorine resistance of the membranes. As a result, TiO2/CDs nanocomposite with little amounts could be applied as a suitable nanofiller to increase the permeability, antifouling properties, and chlorine resistance for RO membrane modification.

Enhanced desalination efficiency of flow-through capacitive deionization cell by mesh electrode with granular aerogel carbon in the removal of ions from synthetic and real samples

Abstract Flow-through capacitive deionization (FTCDI) is a traditional improved flow-by CDI cellular structure, used to remove ions from aqueous solutions. In this study, a new FTCDI was designed consisting of mesh electrodes (ME) containing ion-exchange membranes (IEM) and aerogel carbon granules with a specific surface area of 489 m2/g. All analyses and experiments performed showed that the new design can remove nitrate, phosphate, sodium, calcium, and chloride. Under optimal conditions, the new FTCDI system can remove 82.5, 49, 85, and 90% of sodium chloride, calcium chloride, nitrate, and phosphate with a maximum input concentration of 450 mg/L, 450 mg/L, 70 mg/L, and 3 mg/L, respectively. The efficiency of this system was also evaluated for real samples. Findings of the study showed that if the initial amount of turbidity is 12 NTU, total soluble solids (TDS) 1,700 mg/L, total hardness 540 mg/L, phosphate 0.09 mg/L, nitrate 28.8 mg/L, and electrical conductivity (EC) 3,480 μs/cm, the system can remove 25, 23.5, 33.3, 66.6, 54.4, and 39.1%, respectively.

Theoretically achievable efficiency of hydrate-based desalination and its significance for evaluating kinetic desalination performance of gaseous hydrate formers

Freshwater can be obtained through gas hydrate formation from saline water, which is called hydrate-based desalination (HBD). In this study, the thermodynamic and kinetic features of propane, R134a, R22, and R152a hydrates in the presence of NaCl were examined to determine the energy-efficient gaseous hydrate former. Structure I hydrate formers (R22 and R152) gave lower hydrate depression temperatures than structure II hydrate formers (propane and R134a) at a given salinity. The theoretically achievable salinity and water yield of HBD at each given thermodynamic condition were calculated using the Hu–Lee–Sum correlation. The theoretical HBD efficiency increased as the initial salinity decreased, the operating pressure decreased, and the initial subcooling temperature increased. At a fixed initial subcooling (2 K), R134a gave faster formation kinetics in the early stage, but R22 eventually offered highest hydrate conversion. At a fixed temperature (272 K), R152a showed fastest formation kinetics and highest HBD efficiency due to its milder hydrate equilibrium conditions. The overall results demonstrated that the thermodynamic stability and the intrinsic formation kinetics of gas hydrates significantly impact HBD efficiency and that the theoretical HBD efficiency can be the quantitative criterion for evaluating the kinetic performance and desalination capability of hydrate formers.

Sea water frozen crystalisation impacted by flow and heterogeneous nucleation: PFM-LBM coupled modeling, simulation and experiments

This study presents a novel phase field method (PFM) - lattice Boltzmann method (LBM) coupled model that describes the ice crystal growth in sea water freezing. Sea water frozen crystalisation impacted by flow and heterogeneous nucleation was numerically and experimentally investigated. The PFM-LBM model was established to conduct simulation. A microscope observation experimental system was built to conduct verification. The results show that flow of sea water effectively promotes the diffusion of discharged salt and the growth of ice crystals, and reduces the probability of dendrite closure. In the directional competitive growth of ice crystals, the salt content trapped in the ice crystals decreased by 17.4% at 0.025 m/s and 21.9% at 0.05 m/s, while the existence of heterogeneous particles resulted in a narrower the brine channel and higher ice crystal growth rate, of which the ice crystal area increased by 10.8% and the trapped salt content in the ice crystals decreased by 14.8%. The study provides both a methodology of numerically simulate sea ice crystallisation which includes the phase change, solute migration, heat transfer and flow, and a feasible controlling approach to improve desalination efficiency of sea water frozen crystallisation.

Analysis the Performance of Hydrophilic and Corrosion Resistant Coatings on the Distillation Desalination Tube in High Temperature Seawater

Distillation desalination can use solar energy and other renewable energy, it is one of the most potential technologies for desalination. However, distillation desalination system pervades problems such as low desalination efficiency and poor corrosion resistance. Based on our preliminary study (i.e., apply hydrophilic modification on the surface of distillation desalination tube can effectively improve desalination efficiency), this paper introduces a composite functional coating with the micro-arc oxidation (MAO) coatings sealed with hydrophilic organic coating-TiO2 hybrid sols (OT-MAO) by sol-gel process. Through contact angle measurement, scanning electron microscopy (SEM) and potentiodynamic polarization test to analyze and compare the performance of hydrophilicity and corrosion resistance of the MAO coatings and the OT-MAO composite coatings in high temperature seawater environment. The corrosion mechanism of the OT-MAO composite coatings was analyzed by electrochemical impedance spectroscopy (EIS). The results show that the OT-MAO composite coatings in high temperature seawater has much better hydrophilicity and corrosion resistance than the MAO coatings. This paper provides theoretical and technical reference for developing a new type of surface modified distillation desalination tube.

Novel strategy to enhance the desalination performance of flow-electrode capacitive deionization process via the assistance of electro-catalytic water splitting

• Porous nickel foam was used as the current collector in FCDI system. • Functionalized current collectors with enhanced water splitting activity were prepared. • Desalination performance of F-NFM-FCDI was enhanced via the assistance of electro-catalytic water splitting. • The enhanced desalination performance of F-NFM-FCDI was attributed to the increased ion concentration in flow-electrode. Flow-electrode capacitive deionization (FCDI) has gained lots of attention for the continuous operation, fast and scalable desalination process. However, the flow electrode slurry is poorly conductive and resulting in the high ions transport resistance, which restricts its desalination efficiency. In this work, a novel FCDI system was constructed by using the porous nickel foam (NFM) as the current collector, and its desalination performance was enhanced via the assistance of electro-catalytic water splitting. In detail, the functionalized current collectors (NFM-Co 3 O 4 with enhanced oxygen evolution activity and NFM-Co(OH) 2 with enhanced hydrogen evolution activity) were prepared through a two-step procedure of electrodeposition and subsequently anodic reaction/cathodic reaction. A desalination efficiency of 90.22% was obtained by the FCDI system adopted functionalized NFM (F-NFM-FCDI) after 100 min operation at applied voltage of 2.0 V, which was much higher than that of the FCDI system adopted bare NFM (NFM-FCDI, 65.37%). Moreover, F-NFM-FCDI system possessed higher charge efficiency (CE) of 81.24% and lower normalized energy consumption (NEC) of 237.54 J·mmol −1 under this condition. Mechanism analysis demonstrated that the enhancement on the desalination performance of F-NFM-FCDI system was attributed to the improved conductivity in flow-electrode chamber, which was due to the increase in the concentration of H + and OH – caused by the enhanced electro-catalytic water splitting reaction during charging. In summary, this work provided a novel and facile strategy to improve the desalination performance of FCDI system by coupling with electro-catalytic water splitting.

Evaluation of synergistic effects of coupling capacitive deionization (CDI) and UV oxidation processes for saline water treatment

In the present study, the synergistic effects of capacitive deionization (CDI) and ultraviolet (UV) based advanced oxidation process (AOP) have been investigated for the simultaneous removal of NaCl salt and humic acid (HA), by an organic contaminant approach. A specific CDI rod geometry setup was utilized to allow for direct UV irradiation on the electrodes’ surface during CDI experiments. The characteristics of the coated electrodes were examined by scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS). The results of desalination experiments showed that the maximum salt adsorption capacity (mSAC) and salt removal efficiency were 3.96 mg/g and 52.5%, respectively under constant operating conditions (i.e., an applied voltage of 1.2 V and an initial salt concentration of 20 mM). Also, experiments involving simultaneous removal of salt and organic contaminant, demonstrated that the presence of HA in water has little impact on the desalination efficiency. After combining CDI and AOP under constant operating conditions (i.e., an applied voltage of 1.2 V, UV irradiation with a fluence rate of 6.8 mW/cm2, and initial concentrations of 20 mM of salt and 10 ppm of HA), the HA removal efficiencies in the charge and discharge reservoirs were 76.0% and 75.4%, respectively after 200 min of experimental time.

Mechanism of Saline–Alkali land improvement using subsurface pipe and vertical well drainage measures and its response to agricultural soil ecosystem

Salinization is recognized as a threat to agricultural productivity and land resources in global arid desert regions. To date, field soil improvement schemes have met with minimal success to date. We aimed to improve saline–alkali soils by assessing the effects of combining subsurface pipe (Pa) and vertical well (Sa) drainage measures on agricultural soils ecosystem. In a five-year field experiment, soil was sampled 0.5 m, 5 m, 7.5 m horizontally away from the Pa, and 0.5 m, 30 m, 60 m horizontally away from the Sa. Findings indicate that the soil electrical conductivity (EC) decreased from 16 dS m−1 to 3 dS m−1 at a 0–80 cm depth, and the soil desalination efficiency was great at the 0–300 cm depths (≥ 32%) than at the 400–700 cm depths (−14%–74.7%). The combined Pa and Sa drainage measures significantly decreased the species richness and quantity of soil microbial communities, and their negative impact on observed species was irreversible within 1 year. The farther the horizontal sampling conducted from the Pa and Sa, the greater the structural similarity of the microbial community at the genus level, higher the catalase, acidic protease, and neutral phosphatase activities, and lower the alkaline phosphatase activity. The overall decrease in groundwater level from 2016 to 2020 was 5.7 m. The seed cotton yield increased by 3.2 t ha−1. The results suggest that the value of saline–alkali soil can be improved by combining Pa and Sa drainage measures. Our research provides guidance for further effective utilization of agricultural water and soil resources and the sustainable development of the soil ecosystem in arid desert areas.

Advancements in Solar Desalination of Seawater by Various Ti3C2 MXene Based Morphologies for Freshwater Generation: A Review

For a few years, we have been witnessing ubiquitous fresh and drinking water scarcity in various countries. To mitigate these problematic situations, many countries relied on non-conventional freshwater generation technologies through solar desalination of seawater. In this manner, we excel the ability of new class 2D Ti3C2 MXenes as a photothermal material (solar absorber) for freshwater generation via the solar desalination technique. In this review, the air–water interfacial interaction is highlighted for improving the evaporation efficiency. To provide the dependence of the desalination efficiency on the microstructure of the solar absorbers, we summarized various forms of 2D Ti3C2 MXenes (aerosol, films, foam, hydrogel, membrane, monolith and porous structure) and their characteristics. These microstructures prevailed ultrahigh photoconversion efficiency. In this aspect, we further explained key features such as light absorption, reflection, multiple internal reflection, hydrophilicity, lower thermal conduction, light-to-heat generation, and salt rejection for achieving efficient desalination output throughout the visible and broadband region. Specifically, we targeted to explore the self-floating and salt rejection nature of various state-of-the-art 2D Ti3C2 MXene structures. Further, we highlighted the long-term stability. Among the above morphologies, Ti3C2 MXene in the form of a membrane is believed to be a promising morphology which effectively desalinates seawater into freshwater. Finally, we highlighted the challenges and future perspectives, which can pave a potential path for advancing the sustainable solar desalination of seawater into freshwater.

A novel asymmetric CDI device for targeted removal of cation in water desalination

A novel asymmetric CDI device was home-made for the removal of cations from aqueous solution through the structural innovation in this experiment. The adsorbent materials were characterized by SEM and BET as well as performing CV curve tests. The results showed that the materials exhibited excellent performance（the Specific surface area is 321.14 m²/g） and the maximum specific capacitance of the adsorbent material can reach 60F/g at the 5mV/s. The optimal operating conditions of the asymmetric CDI device were obtained using an orthogonal test method analysis and response surface methodology (RSM): the best desalination efficiency of CDI was obtained at concentration is 455.82 mg/L, potential is 1.18 V and flow rate is 46.54 mL/min. After the analysis of first-order kinetic model，it can be obtained that the fastest adsorption efficiency for Ca2+, followed by Mg2+, and the slowest for Na+, and the CDI device had better adsorption effect on divalent cations. Simulation by Comsol software showed that the adsorption efficiency was better at high flow rate. In addition, the CDI device has good stability, and the mechanism of targeted cation removal and mass transfer process of the CDI were discussed in detail.

Recovery of Biologically Treated Textile Wastewater by Ozonation and Subsequent Bipolar Membrane Electrodialysis Process.

The Bipolar Membrane Electrodialysis process (BPMED) can produce valuable chemicals such as acid (HCl, H2SO4, etc.) and base (NaOH) from saline and brackish waters under the influence of an electrical field. In this study, BPMED was used to recover wastewater and salt in biologically treated textile wastewater (BTTWW). BPMED process, with and without pre-treatment (softening and ozonation), was evaluated under different operational conditions. Water quality parameters (color, remaining total organic carbon, hardness, etc.) in the acid, base and filtrated effluents of the BPMED process were evaluated for acid, base, and wastewater reuse purposes. Ozone oxidation decreased 90% of color and 37% of chemical oxygen demand (COD) in BTTWW. As a result, dye fouling on the anion exchange membrane of the BPMED process was reduced. Subsequently, over 90% desalination efficiency was achieved in a shorter period. Generated acid, base, and effluent wastewater of the BPMED process were found to be reusable in wet textile processes. Results indicated that pre-ozonation and subsequent BPMED membrane systems might be a promising solution in converging to a zero discharge approach in the textile industry.

The use of anti-scalants in gypsum scaling mitigation: Comparison with membrane surface modification and efficiency in combined reverse osmosis and membrane distillation

Membrane scaling is detrimental to the efficiency of membrane desalination. While both membrane surface modification and the addition of anti-scalants have been investigated as possible methods to minimize scale formation on membrane surfaces, the efficacies of these two strategies have not been compared in the literature. In this work, we first modified a commercial polyamide reverse osmosis (RO) membrane with four different polymers to create various surface functionalities and properties. Then the anti-scaling efficiencies of the modified membranes were evaluated and compared with the use of poly(acrylic) acid (PAA) as anti-scalant in a bench-scale RO system fed with gypsum supersaturated solutions. The modified membrane with the best performance displayed limited effectiveness in delaying gypsum scaling, whereas gypsum scaling was greatly retarded in the presence of PAA. In contrary to the passive effect of membrane surface modification on gypsum scaling, anti-scalants actively disrupt gypsum crystallization. Further, we applied membrane distillation (MD) to desalinate the concentrated brines generated from RO desalination with and without anti-scalants. We demonstrated that the residual PAA in the RO brines was highly effective to alleviate gypsum scaling in MD, greatly enhancing the total water recovery of the combined RO-MD system. Our results provide comparative insights on the efficiencies of different scaling mitigation strategies in membrane desalination, and demonstrate the promising potential of applying anti-scalants to achieve high water recovery.

Modern Use of Water Produced by Purification of Municipal Wastewater: A Case Study

All the urban areas of developed countries have hydric distribution grids and sewage systems for collecting municipal wastewater to treatment plants. In this way, the municipal wastewater is purified from human excreta and other minor contaminants while producing excess sludges and purified water. In arid and semi-arid areas of the world, the purified water can be used, before discharging, to enhance the energy efficiency of seawater desalination and solve the problems of marine pollution created by desalination plants. Over the past half-century, seawater desalination has gradually met demand in urbanized, oil-rich, arid areas. At the same time, technological evolution has made it possible to significantly increase the energy efficiency of the plants and reduce the unit cost of the produced water. However, for some years, these trends have flattened out. The purified water passes through the hybridized desalination plant and produces renewable osmotic energy before the final discharge in the sea to restart the descent behaviour. Current technological development of reverse osmosis (RO), pressure retarded osmosis (PRO) and very efficient energy recovery devices (ERDs) allows this. Furthermore, it is reasonable to predict that, in the short-medium term, a new generation of membranes specifically designed for improving the performance of the pressure retarded osmosis will be available. In such circumstances, the presently estimated 13-20% decrease of the specific energy consumption will improve up to more than 30%. With the hybrid plant, the salinity of the final discharged brine is like that of seawater, while the adverse effect of GHG emission will be significantly mitigated.

Predictive modelling for solar power-driven hybrid desalination system using artificial neural network regression with Adam optimization

Today artificial intelligence is a major utility technology that can help industry and research in many fields, including solar thermal energy for water desalination purposes. Hence, the main aim of the paper focus on utilizing an artificial intelligent regression model to predict the efficiency of water desalination, which depends on solar thermal energy. The contribution helps manufacturers and research determine the productivity of the designed desalination system in the beta environment before realizing the system. The used desalination system merges and hybrids in our experimental modelling solar still and air humidification and dehumidification. Regards the prediction of performance and productivity, a wide range of regression algorithms, including multilayer perceptron (MLP), decision trees (DT), and Bayesian ridge regression (BRR), were applied. Also, the MLP is optimized to enhance the prediction by employing the Adam optimization to propose OMLP. The OMLP is compared to regular MLP, DT, and BRR using a variety of evaluation metrics, including statistical measures, the goodness of fit, and regression accuracy. The OMLP achieves better performance of dependent variables; YHDH, YSS, Tswh,in, Tswh,o, Ta,H,in, Ta,H,o, and Φa,H,in using whole independent variables by RMSE ∈ [0.07171, 8.05636], Max Error ∈ [0.10108, 14.19858], and CRM ∈ [0.0202, 0.0329] and using top three correlated independent variables by MAE ∈ [0. 0514, 5.777], RMSE ∈ [0.07171, 7.0559], and CRM ∈ [0.0029, 0.0498].

Recent advanced self-propelling salt-blocking technologies for passive solar-driven interfacial evaporation desalination systems

Conventional active seawater evaporation technologies, that is, they include components with mechanical moving parts, generally involve large plants with high capital and operating costs. Recently, the passive solar-driven interfacial evaporation (PSDIE) with no active parts is considered as one of the most promising solar energy utilization and freshwater acquisition way. Especially in isolated and impoverished off-grid areas, passive desalination with economic feasibility and reliability has great application prospects. Based on the effective optical-thermal control of evaporator design and reasonable arrangement of deployment scheme, thermal localization in the vapor-liquid interface is conducive to reducing the heat dissipation into the bulk water and significantly improving the efficiency of desalination. Nonetheless, the Achilles’ heel of the technology, namely the existence of salt accumulation at the photothermal interface under the condition of high intensity work including concentrated brine water and intense solar irradiation, which inevitably reduces the availability of fresh water resources and the service life of the evaporator. Addressing this issue is of the utmost importance and arduous task to maintain uninterrupted passive evaporator operation. In this review, the outline of the state-of-the-art self-propelling salt-blocking strategies in PSDIE is mainly divided into three categories, i.e. mechanical removal, shielding effect, and force-driven fluid flow. Finally, the challenges and prospects of salt resistance in PSDIE are emphasized, providing a roadmap for the future development of solar evaporation technology. • General models and salt-blocking mechanisms of currently available solar evaporators are proposed. • Progress of three categories of self-propelling salt-blocking technologies are compared. • Future perspectives for practical passive solar-driven interfacial evaporation desalination systems are proposed.