Desalination Research Articles

Structure-performance relationship in tailored poly(amide-sulfone) membranes for desalination

Poly(amide-sulfone)s were considered the missing link for water desalination membranes, owing to their exceptional properties resulting from the synergism effects of two amide and sulfone structures. To achieve this, a sulfone-based diamine was first synthesized by reacting 4,4′-dichlorodiphenyl sulfone with 3-aminophenol. Subsequently, alternative copolymers of poly(amide-sulfone) were prepared via polycondensation reactions of the synthesized diamine monomer and various diacid chlorides including adipoyl dichloride, isophthaloyl dichloride, and terephthaloyl dichloride. The chemical structures were approved using Fourier transform infrared spectroscopy and hydrogen nuclear magnetic resonance spectroscopy. Porous membranes of the polymers as substrates were prepared by solution casting and phase-inversion method. To form thin film composite membranes, a thin polyamide layer was created through interfacial polymerization on the top surface of prepared substrates using m-phenylenediamine and trimesoyl chloride. After characterization, the performance of all membranes was assessed by evaluating pure water flux, NaCl rejection, and flux recovery ratio using a cross-flow filtration system. The impact of the amide group within the poly(amide-sulfone) substrate structure on thin-film efficiency was explored. Results, revealed that the structure significantly influenced membrane performance. Specifically, the highest pure water flux was 549.50 L.m−2.h−1. Also, NaCl rejection of 98.27 % and flux recovery ratio of 94.21 % were observed among them at pressure of 10 bar. This study provided valuable insights for developing novel poly(amide-sulfone) membranes tailored for desalination applications.

Performance Enhancement in Air Gap Membrane Distillation Using Heat Recovery Configurations

Experimental investigations were conducted on an air gap membrane distillation (AGMD) unit to evaluate the impact of heat recovery on system performance. The study utilized a steady-state heat source in conjunction with a spiral air gap membrane module for water desalination. The process was implemented using two configurations aimed to minimize heat loss enhancing productivity, gain output ratio (GOR), and thermal efficiency. The experiments involved feedwater with salt concentrations ranging from 10,000 to 30,000 ppm. The measurements were recorded for inlet and outlet temperatures of the heat source, water productivity, and thermal efficiency at various coolant and water feed flow rates. These configurations effectively addressed critical technical challenges in thermal AGMD systems by optimizing heat recovery. The incorporation of heat recovery resulted in a significant increase in water productivity by 37.07% compared to systems without heat recovery while maintaining the same initial heat input. The heat recovery in series (HRSS) and parallel (HRPS) configurations resulted in power consumption reductions of approximately 29.7% and 23.1%, respectively compared to the conventional configuration (CC) at a flow rate of 12 L/min. The levelized cost of water (LCOW) for the AGMD system was comprehensively evaluated and found to be $ 7.71 per cubic meter. This figure reflected the total cost of water production over the system's operational lifespan including capital expenditures, operating and maintenance costs, and energy consumption. The calculated LCOW provides a clear indicator of the system's economic viability, demonstrating the cost required to produce each cubic meter of water through the AGMD.

Employing binary/ternary organic blends in integrated HP-assisted HDH desalination systems

The global demand for potable water is rising, prompting the development of various energy systems for distilled water production. However, the significance of utilizing multicomponent working fluids in these systems has been largely overlooked. This study presents three HDH-based distillation units powered by two conventional heat pump cycles, namely, the simple and vapor injection heat pumps (first and second models) and an innovative heat pump cycle with an ejector expander (third model). The significance of the research lies in its pioneering investigation of utilizing two- and three-component mixtures in heat pump-based desalination units, which has not been previously explored. The study's primary aim is to determine whether using multicomponent working fluids instead of pure fluids or introducing structural modifications can more effectively enhance the performance of heat pump-based distillation units. The proposed models are simulated using EES and MATLAB software, with the study focusing on energetic, exergetic, exergoeconomic, and heat exchanger modeling to evaluate the feasibility of the configurations. The findings revealed that the structural modifications in the third scenario using R134a resulted in the highest GOR, with improvements of 44 % and 26.03 %, respectively, compared to the other scenarios. However, utilizing binary blend R22/R142b with different compositions improved the GOR of the first to three scenarios by 41.26 %, 29.06 %, and 11.87 %, respectively. Furthermore, in this case, the unit cost of distilled water for the first, second, and third scenarios increased by 12.87 %, 14.32 %, and 12.70 %, respectively. Finally, the first scenario has the highest NPV of 4.40 M$ and the shortest PP of 8.13 years. Therefore, utilizing the blend in a simple heat pump proves to be more efficient and cost-effective than implementing structural modifications.

Исследование работы термической опреснительной установки с контактным испарителем и компрессией паровоздушной смеси

One of the global issues of our time is the shortage of freshwater resources. Desalination of marine and brackish waters is a promising solution to this problem. The most common desalination technologies are thermal (distillation) and baromembrane (reverse osmosis and nanofiltration) processes. When designing demineralization stations with reverse osmosis units, it is necessary to consider a number of limitations associated with higher requirements for pretreatment of water entering the unit. The use of thermal desalination plants makes it possible to obtain fresh water of higher quality, and less stringent requirements are imposed on the preliminary preparation of water for this type of unit. However, during the operation of desalination plants of this type, scale forms on the heating surfaces, which negatively affects the efficiency of the unit. Scale is formed less intensively in the units with contact vapors, since in this case the evaporation process occurs in volume. Thus, the development of thermal scheme of such unit and the study of their operation is relevant. The tasks have been solved using the methods of experimental studies of heat and mass transfer processes, mathematical processing of experimental data, and balance calculations of power plants. A thermal scheme of a thermal desalination plant with a contact evaporator with compression of a vapor-air mixture has been developed. Thermal and material balance has been compiled, on the basis of which energy costs have been determined to obtain m3 of fresh water. The authors have proved the determining influence of the temperature of desalinated water in the bubbling zone on the productivity of desalination plants with a contact evaporator. An amendment has been obtained that allows the initial salinity of water and brine to be considered when calculating the operating cycle of the unit. As a result of the analysis of the results obtained, it is found that an increase in the water temperature in the bubbling zone allows us to increase the productivity of the unit, and an increase of the drying temperature of the vapor-air mixture leads to a decrease of the energy consumption of the desalination plant. The introduction of an amendment considering the salinity of the source water and brine makes it possible to increase the accuracy of calculating air humidification up to 15 %.

Analysis of Battery Charging Using 100 Wp Solar Cells as Power Supply for Water Desalination Equipment

Analysis of Battery Charging Using 100 Wp Solar Cells as Power Supply for Water Desalination Equipment

Bead-Free PSF/PVP Blend Membrane as Potential Material for Water Desalination

We herein report successful fabrication of bead-free PSF/PVP blend membrane using electrospinning technique.

Evaluation of Modified Conventional Still Distiller Using Coupled External Passive Condenser: An Experimental Study

Solar radiation plays an important part in the desalination of saline water owing to its abundance in areas with potable water shortage and it also occupies a paramount place in green energy generation due to its simplicity of application. Still distiller is viewed by researchers as a suitable source of potable water because of low cost of fabrication, easy operation and zero emission technology. Studies by researchers are geared towards exploring new models to improve the productivity of solar stills and enhance its production rate is ongoing. The main aspiration of this work is to experiment the consequence of introducing a passive condenser to a modified conventional solar still to enhance its productivity yield. It was observed that the modified passive still distiller coupled with the external condenser gave about 11.85% higher production yield in comparison with the modified conventional still distiller. Daily and accumulated distillate yield for the still distillers have been studied and analyzed. The result of the findings revealed that sawdust padding around the still distillers is recommended to maximize productivity leading to efficient water distillation in regions where that require still distiller usage. This recommendation has been seen to produce the desired result in accessing to potable water within areas where water scarcity prevails. This is suggested to contribute effectively bearing the cost ineffective water desalination technique.

A Theoretical Model for the Hydraulic Permeability of Clayey Sediments Considering the Impact of Pore Fluid Chemistry

The chemistry of the pore fluid within clayey sediments frequently changes in various processes. However, the impacts of pore fluid chemistry have not been well included in the hydraulic permeability model, and the physical bases behind the salinity sensitivity of the hydraulic permeability remains elusive. In this study, a theoretical model for the hydraulic permeability of clayey sediments is proposed, and impacts of the pore fluid chemistry are quantitatively considered by introducing electrokinetic flow theory. Available experimental data were used to verify the theoretical model, and the verified model was further applied as a sensitivity analysis tool to explore more deeply how hydraulic permeability depends on pore fluid chemistry under different conditions. Coupling effects of pore water desalination and the effective stress enhancement on the hydraulic permeability of marine sediments surrounding a depressurization wellbore during hydrate production are discussed. Results and discussion show that the hydraulic permeability reduction is significant only when the electric double layer thickness is comparable to the characteristic pore size, and the reduction becomes more obvious when the ion mobility of the saline solution is smaller and the surface dielectric potential of clay minerals is lower. During gas hydrate production in the ocean, the salinity sensitivity of the hydraulic permeability could become either stronger and weaker, depending on whether the original characteristic pore size of marine sediments is relatively large or small.

Advancing Sustainable Seawater Desalination in the Persian Gulf: Opportunities and Challenges under the Kuwait Convention 1978

Seawater desalination has emerged as a viable solution, notably utilized by many Persian Gulf littoral countries facing severe water shortages and aiming to achieve the targets of the sustainable development goal 6 regarding ensuring availability and sustainable management of water and sanitation for all. However, desalination comes with costs and can adversely impact marine ecosystems. Conserving and sustainably using oceans, seas, and marine resources is one of the sustainable development goals (Goal 14), and unmanaged use of desalination plants in the Persian Gulf Coasts can threaten this goal. Therefore, moving towards a sustainable process of seawater desalination in this region requires the promotion of cooperation, including through the effective implementation of existing multilateral environmental agreements (MEAs). Based on this, the main question of this paper is: what are the opportunities and challenges of the Kuwait Convention (1978) in advancing sustainable seawater desalination in Persian Gulf? The results of descriptive and analytical studies based on library resources in this research indicate that the provisions concerning the prevention, control and combating of land-based pollution, as well as requirements for environmental impact assessments, are the most significant opportunities provided by this instrument. However, the lack of direct obligations regarding the management of seawater desalination and non-existence of effective compliance mechanisms are the challenges of this convention. To address these challenges, adopting a seawater desalination management guideline under ROPME, promoting international cooperation, sharing experiences and knowledge related to innovative technologies and empowering compliance mechanisms under this convention are the essential recommendations for the effective implementation of the Kuwait Convention towards sustainable seawater desalination in the region.

Performance simulation of solar-driven absorption heat pump-membrane distillation system for combined desalination brine concentration with feed recirculation and cooling applications

Desalination is the primary choice for securing freshwater provision in water-stressed regions and reduces the gap between rising demand and dwindling natural freshwater resources. However, global desalination plants are dominated by fossil fuel-driven desalination technologies with a 40–50 % recovery ratio. Hence, it is critical to decarbonize desalination and address brine effluent ecological concerns. In this paper, a solar-powered absorption heat pump (AHP)-membrane distillation (MD) system concept was proposed and analysed for small-scale RO plant brine reject management and space cooling applications. The MD subsystem is based on commercial MD modules with batch feed recirculation to reach saturation (from 70 to 260 g/kg salinity). The MD system's heating and cooling consumptions are supplied by the AHP (6.54 MWh and 13.47 MWh, respectively, for a complete batch cycle). The AHP is designed to supply hot water at 85 °C with 701.63 kW heating capacity and co-produced chilled water at 16 °C with a cooling capacity of 857.86 kW, about 67 % is utilized to cool down the brine reject to feed temperature. The thermal and exergy COPs were 1.273 and 0.40 at a driving heat of 135 °C. The solar-powered AHP-MD system is useful for sustainable desalination deployment besides space cooling applications.

Zwitterion Modification in Desalination Membrane for Rejecting Salt and Salt Ions in Brackish Water – A Mini Review

ABSTRACTDesalination membrane using zwitterion modification provides a significant opportunity to enhance excellent properties for rejecting salt and salt ions. The outstanding properties are designed by positive and negative charges attached to the membrane surface, including water permeability, salt permeability, fouling, and hydrophilicity of the membrane surface. The hydrophilic membrane, which is mentioned as one of the types of desalination membrane, presents the ability to repel salt and salt ions and pass the water. The modification of hydrophilic membranes is also affected by several factors, including water permeability, salt permeability, fouling of membrane surfaces, crossflow velocity, transmembrane pressure, and temperature. Regarding membrane modification, zwitterion has been applied for several ranges, such as the hemodialysis process, live cell imaging, antibacterial surfaces, and wound dressing. However, using a zwitterion modification membrane for desalinating water containing salt content, including brackish water, has yet to be developed. In addition, literature reviews related to polymer membranes for brackish water desalination have never been comprehensively documented. Thus, this review article addresses the zwitterion modification for desalination membranes, which can reject salt and salt ions in brackish water. Furthermore, the mechanism of zwitterion modification for desalination membranes has been presented. Finally, the challenge of zwitterion modification for desalination membranes has been evaluated to inspire insight for future studies.

Life After Death: Re‐Purposing End‐of‐Life Supercapacitors for Electrochemical Water Desalination

AbstractThis study explores the potential of re‐purposing end‐of‐life commercial supercapacitors as electrochemical desalination cells, aligning with circular economy principles. A commercial 500‐Farad supercapacitor was disassembled, and its carbon electrodes underwent various degrees of modification. The most straightforward modification involved NaOH‐etching of the aluminum current collector to produce free‐standing carbon films. More advanced modifications included CO2 activation and binder‐added wet processing of the electrodes. When evaluated as electrodes for electrochemical desalination via capacitive deionization of low‐salinity (20 mM) NaCl solutions, the minimally modified NaOH‐etched carbon electrodes achieved an average desalination capacity of 5.8 mg g−1 and a charge efficiency of 80 %. In contrast, the CO2‐activated, wet‐processed electrodes demonstrated an improved desalination capacity of 7.9 mg g−1 and a charge efficiency above 90 % with stable performance over 20 cycles. These findings highlight the feasibility and effectiveness of recycling supercapacitors for sustainable water desalination applications, offering a promising avenue for resource recovery and re‐purposing in pursuing environmental sustainability.

Visible-light-activated Fe2O3–TiO2 nanoparticles enhance biofouling resistance of polyethersulfone ultrafiltration membranes against marine algae Chlorella vulgaris

This study investigated the modification of polyethersulfone (PES) ultrafiltration membranes with TiO2 and Fe2O3–TiO2 nanoparticles to enhance their hydrophilicity and biofouling resistance against the marine microalgae Chlorella vulgaris. It is a common freshwater and marine microalga that readily forms biofilms on membrane surfaces, leading to significant flux decline and increased operational costs in ultrafiltration processes. The microalgae cells and their extracellular polymeric substances (EPS) adhere to the membrane surface, creating a dense fouling layer that impedes water permeation. The modified membranes were characterized using contact angle measurements, scanning electron microscopy, and pure water flux/resistance tests. Short-term ultrafiltration experiments evaluated the membranes’ antifouling performance by measuring flux decline, flux recovery ratio, and relative flux reduction during C. vulgaris filtration. The TiO2 membrane showed improved hydrophilicity and antifouling over the pristine PES membrane, while the Fe2O3–TiO2 nanocomposite membrane exhibited the best performance. It reduced the water contact angle and showed only a 5% relative flux reduction compared to 60% for the pristine membrane. SEM images confirmed reduced microalgal deposition on the nanocomposite surface. Long-term tests with microalgal cells under dark and visible light conditions in saline water further assessed the membranes’ biofouling resistance. The Fe2O3–TiO2 membrane maintained 59 L/m2 h water flux under visible light after immersion in the microalgal solution, outperforming the pristine (38 L/m2 h) and TiO2 (52 L/m2 h) membranes. This superior antifouling was attributed to photocatalytic generation of reactive oxygen species inhibiting microalgal adhesion. This study demonstrates a promising strategy for mitigating biofouling in membrane-based water treatment and desalination processes.

Low-Energy Desalination Techniques, Development of Capacitive Deionization Systems, and Utilization of Activated Carbon

Water desalination technology has emerged as a critical area of research, particularly with the advent of more cost-effective alternatives to conventional methods, such as reverse osmosis and thermal evaporation. Given the vital importance of water for life and the scarcity of potable water for agriculture and livestock—especially in the Kingdom of Saudi Arabia—the capacitive deionization (CDI) method for removing salt from water has been highlighted as the most economical choice compared to other techniques. CDI applies a voltage difference across two porous electrodes to extract salt ions from saline water. This study will investigate water desalination using CDI, utilizing a compact DC power source under 5 volts and a standard current of 2 amperes. We will convert waste materials like sunflower seeds, peanut shells, and rice husks into activated carbon through carbonization and chemical activation to improve its pore structure. Critical parameters for desalination, including voltage, flow rate, and total dissolved solids (TDS) concentration, have been established. The initial TDS levels are set at 2000, 1500, 1000, and 500 ppm, with flow rates of 38.2, 16.8, and 9.5 mL/min across the different voltage settings of 2.5, 2, and 1.5 volts, applicable to both direct and inverse desalination methods. The efficiency at TDS concentrations of 2000, 1500, and 1000 ppm remains between 18% and 20% for up to 8 min. Our results indicate that the desalination process operates effectively at a TDS level of 750 ppm, achieving a maximum efficiency of 45% at a flow rate of 9.5 mL/min. At voltages of 2.5 V, 2 V, and 1.5 V, efficiencies at 3 min are attained with a constant flow rate of 9.5 mL/min and a TDS of 500 ppm, with the maximum desalination efficiency reaching 56%.

The Israeli Water Policy and Its Challenges During Times of Emergency

In a time of growing climate crisis, and despite the global warming trend, Israeli citizens routinely enjoy a regular constant supply of clean fresh water thanks to local desalination plants. Establishment of the desalination plants has become a model of water management for many countries in an era of growing climate crisis. At the same time, Israel’s water sector is faced with challenges and threats related to earthquakes, various states of warfare, and security confrontations. In such times of emergency, Israel’s water sector is particularly vulnerable to disruptions of the water infrastructure and its adequate operation by both contamination of the water sources and damage to the desalination plants. This study examines the challenges of the Israeli water sector that require it to contend with these emergency situations in an era of reliance on desalination plants. The research findings lead to the conclusion that public policy on managing the water sector, manifested in the development and establishment of water desalination plants, has resolved Israel’s water crisis, put an end to its dependency on the amount of precipitation and on natural water sources, and allowed for an increase in water production to match the rise in consumption. Nonetheless, as successful as this public policy may be, it does not consider the possibility of extreme scenarios and does not develop the entire range of steps necessary to confront them, and thus it undermines the ability of the Israeli water sector to provide its citizens with water in times of emergency.

Gypsum Binder With Increased Water Resistance Derived From Membrane Water Desalination Waste

ABSTRACTA method has been developed for separating a mixture of calcium, magnesium and sodium sulfates obtained through the interaction of sulfuric acid and waste from the water purification process generated by using membrane filters. The primary goal of this method is to extract gypsum and produce gypsum‐based binders. Patterns were identified regarding how various types, ratio and quantities of additives: blast furnace slag, granite screenings, portland cement, electric steel smelting slag affect the water‐gypsum ratio, strength properties, and water resistance of high‐strength gypsum binders. It was found that adding a single‐component additive specifically to enhance water resistance does not significantly impact these properties. Complex additives have been developed based on Portland cement, granulated blast furnace slag, electric furnace slag, expanded clay dust, and granite screenings of various fractions. These additives are designed to maximize the water resistance of high‐strength gypsum binder based on synthetic calcium sulfate dihydrate. As a result, the water resistance coefficient increased from 0.45 to 0.52. Additionally, a technological block diagram of the process has been proposed.

The Water–Energy Nexus in 26 European Countries: A Review from a Hydrogeological Perspective

The significance of the interconnection between water and energy, known as the water–energy (WE) nexus, is highly regarded in scientific publications. This study used a narrative review method to analyze the existing WE nexus studies performed before 2024 in 26 European countries. The aim of this study is to provide a comprehensive analysis of the existing WE nexus to identify research gaps and to report a conceptual overview of energy consumption related to groundwater use phases, ranging from the tapping to distribution. This information is valuable as a guideline for any future estimates in this field. The results indicate that the WE nexus in 26 European countries comprises a variety of topics, including the water supply system, wastewater treatment, hydropower, desalination, and biofuel production. Most of the focus has been on fossil fuel production, while water supply and desalination were considered rarely. Italy and Portugal had the largest WE nexus. It is highlighted that there have been no studies on the WE nexus focusing on the groundwater supply system that consider the conceptual hydrological model or hydrodynamic processes. In this work, a view of these aspects was provided by taking into account different hydrogeological and hydraulic scenarios that may affect the amount of energy required for groundwater exploitation. Most scientific publications have focused on quantitative analysis. In the future, it will be necessary for WE nexus models to place a greater emphasis on governance and the implications of the WE nexus approach.

Enhanced desalination performance of flow capacitive deionization with the addition of conductive polymer in redox couples and activated carbon

Freshwater scarcity is a critical global issue and desalination of brackish water and seawater technologies are regarded as effective solution to mitigate the increasing severity of water shortage. Flow-electrode capacitive deionization (FCDI) is an emerging electrochemical desalination technology capable of continuous deionization behavior. However, reducing energy consumption and enhancing desalination rate are now markedly needed for its advancement. Herein, we propose a FCDI system with energy consumption as low as 88.08 kJ mol−1 and a desalting rate of 1.75 μg cm−2 s−1. This is achieved by using flow electrodes containing 0.03125 wt% conductive polymer, 5 wt% activated carbon/carbon black and 80 mM/80 mM ferricyanide/ferrocyanide at a current density 3 mA cm−2 (3.36 mA current for a 1.12 cm2 active area). We further investigate the effects of polymer content, redox pair content, salt content and current densities on desalination performance. Seawater with a conductivity of 52.78 mS cm−1 was successfully desalinated to 0.50 mS cm−1 in continuous process. This research provides a promising approach to enhance FCDI system by achieving a low energy consumption and high salt removal rate, representing a significant advancement in continuous electrochemical desalination technology.

High‐efficiency solar selective absorber: Using the high‐entropy nitride MoTaTiCrN nanoceramics as a perspective strategy

AbstractHigh‐entropy materials have sparked significant interest in varied applications, particularly in solar‐thermal technologies such as solar‐driven desalination and concentrating solar power (CSP) systems. In this context, high‐entropy nitrides, as novel solar selective absorbers (SSAs) materials, play a crucial role in these applications, demonstrating excellent spectral selectivity and strong thermal and chemical stability at high temperatures and in harsh environments. However, the underlying sunlight absorption mechanisms, atomic‐level structures, and programmatic design route of these SSAs still need further investigation. Herein, a high‐entropy alloy (MoTaTiCr) target was used to construct gradient high‐entropy nitride films via magnetron sputtering in the nitrogen atmosphere. The atomic‐level microstructure study revealed the crystal structure characteristics in the MoTaTiCrN layer. Computer simulations and density functional theory calculations aided in the design and understanding of the possible solar absorption mechanisms. The as‐deposited SSA exhibited impressive optical properties (α = 95.2%; ε = 6.8%) and demonstrated excellent thermal robustness, maintaining performance after long‐term annealing at 600°C for 300 h. Its photothermal conversion efficiency reached 87.9% at 600°C under 100 suns. As a proof‐of‐concept demonstration, the SSA, used in a solar‐powered photothermal desalination unit, showed a high evaporation efficiency since the excellent optical performance as well as the thermal management.

Utilising Artificial Intelligence to Predict Membrane Behaviour in Water Purification and Desalination

Water scarcity is a critical global issue, necessitating efficient water purification and desalination methods. Membrane separation methods are environmentally friendly and consume less energy, making them more economical compared to other desalination and purification methods. This survey explores the application of artificial intelligence (AI) to predict membrane behaviour in water purification and desalination processes. Various AI platforms, including machine learning (ML) and artificial neural networks (ANNs), were utilised to model water flux, predict fouling behaviour, simulate micropollutant dynamics and optimise operational parameters. Specifically, models such as convolutional neural networks (CNNs), recurrent neural networks (RNNs) and support vector machines (SVMs) have demonstrated superior predictive capabilities in these applications. This review studies recent advancements, emphasising the superior predictive capabilities of AI models compared to traditional methods. Key findings include the development of AI models for various membrane separation techniques and the integration of AI concepts such as ML and ANNs to simulate membrane fouling, water flux and micropollutant behaviour, aiming to enhance wastewater treatment and optimise treatment and desalination processes. In conclusion, this review summarised the applications of AI in predicting the behaviour of membranes as well as their strengths, weaknesses and future directions of AI in membranes for water purification and desalination processes.