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Nanoporous membranes offer significant advantages in direct contact membrane distillation applications due to their high flux and strong resistance to wetting. This study employs molecular dynamics simulations to explore the performance of membrane distillation in a single nanopore, mainly focusing on wetting behavior, liquid entry pressure, and membrane flux variations across different concentrations and types of salt solutions. The findings indicate that increasing the NaCl concentration enhances the wetting of membrane pores, thereby decreasing the entry pressure of the solution. However, at the same salt concentration, the differences in wetting and liquid entry pressure among various salts, including CaCl2, KCl, NaCl, and LiCl, are minimal. The presence of hydrated ions significantly reduces membrane flux. As the concentration of NaCl solutions increases, the number of hydrated ions rises, thereby lowering the membrane flux of the salt solution. Furthermore, the type of salt has a pronounced effect on the structure of hydrated ions. Solutions with Ca2+ and Li+ exhibit the smallest first-layer radius of hydrated ions. Under the same salt concentration, KCl solutions demonstrate the highest membrane distillation flux, while CaCl2 solutions show the lowest flux. [ABSTRACT FROM AUTHOR]

The study presents an innovative solar-assisted dual-tank direct contact membrane distillation (DCMD) system designed to enhance the operational stability and efficiency of solar-powered desalination. The proposed system integrates a dual thermal storage tank configuration, allowing for continuous operation by alternating between two tanks that store pre-heated water, thereby mitigating the impact of solar energy fluctuations. The dynamic modeling approach used in this study predicts the system's performance under varying solar conditions, focusing on key parameters such as permeate flux, evaporation efficiency, and specific thermal energy consumption. The simulation results show that the system achieves an average permeate flux of 14.4 L/h m² and a thermal efficiency of 53.3 % at a hot water temperature of 60 °C, with a corresponding average specific thermal energy consumption of 1567 kWh/m³. These findings highlight a substantial improvement in both thermal efficiency and water production compared to conventional single-tank systems.The dual-tank DCMD system is particularly suited for deployment in remote or arid regions where stable and efficient freshwater production is critical. This research provides a comprehensive analysis of a novel solar-assisted desalination technology, contributing to the advancement of sustainable water resources management by providing a reliable and scalable solution that can maintain high operational efficiency even in remote areas with variable solar conditions.

There are several uses for electrospun nanofiber membranes because of their unique properties. Electrospinning, under suitable conditions, has allowed for the successful fabrication of nanofibrous membranes. This research, a dual-layer membrane was prepared and applied in a direct contact membrane distillation (DCMD) system. Polyacrylonitrile (PAN) based electrospun nanofibers comprised the initial (base) layer. Hydrophobic electrospun nanofi- bers made from polymethyl methacrylate (PMMA) comprised the second (top) layer. The analysis was carried out using contact angle measurements and scanning electron microscopy (SEM) for the morphology and wetting of a series of two-layer nanofiber membranes that were made with different percentages of PAN: PMMA. The study examined how the permeate flux was affected by changes in feed concentration, feed temperature, and feed flow rate. and optimized within a logical framework. These included feed inlet temperatures between 35 and 55 °C, salt concentrations between 70,000 and 210,000 ppm, and rates of supply flow of 0.2, 0.4, and 0.6 L/min. DCMD findings for the (25 PAN:75PMMA) membrane displayed that the amount of salt it rejected was better than 99.356% with flux 51.872 kg/m2.h and a penetrate through conductivity lower down 334 µs/cm when performed under optimally supplied conditions (i.e., 70 g/L; 0.6 L/min; and 55 °C). [ABSTRACT FROM AUTHOR]

In this numerical study, the performance of ceramic-based mullite hollow fiber (HF) membranes in a direct contact membrane distillation (DCMD) process was evaluated. Three types of membranes were tested: (i) hydrophobic membrane C8-HFM, (ii) rod-like omniphobic membrane (C8-RL/TiO2), and (iii) flower-like omniphobic membrane (C8-FL/TiO2). The CFD model was developed and validated with experimental results, which were performed over a 500 min period. The initial mass flux of C8-HFM was 30% and 9% higher than that of C8-FL/TiO2 and C8-RL/TiO2, respectively. However, the flower-like omniphobic membrane C8-FL/TiO2 had the lowest drop in flux, around 11%, while the rod-like omniphobic membrane C8-RL/TiO2 had a 15% reduction, both better than the 23% reduction in the hydrophobic membrane C8-HFM over the 500 min. The study also analyzed the impact of fouling by examining the variation in mass transfer coefficient (MTC) over time. The results indicated that the ceramic-based mullite HF membranes with TiO2 flowers and rods demonstrated a high resistance to fouling compared to C8-HFM. The modified membranes could find applications in the desalination and handling of seawater samples containing organic contaminants. The CFD model’s versatility can be utilized beyond the current investigation’s scope, offering a valuable tool for efficient membrane development solutions, particularly for challenges such as the presence of organic contaminants in seawater.

Membrane desalination (MD) is an efficient process for desalinating saltwater, combining the uniqueness of both thermal and separation distillation configurations. In this context, the optimization strategies and sizing methodologies are developed from the balance of the system’s energy demand. Therefore, robust prediction modeling of the thermodynamic behavior and freshwater production is crucial for the optimal design of MD systems. This study presents a new advanced machine-learning model to obtain the permeate flux of a tubular direct contact membrane distillation unit. The model was established by optimizing a long-short-term memory (LSTM) model by an election-based optimization algorithm (EBOA). The model inputs were the temperatures of permeate and the feed flow, and the rate and salinity of the feed flow. The optimized model was compared with other optimized LSTM models by sine–cosine optimization algorithm (SCA), artificial ecosystem optimizer (AEO), and grey wolf optimization algorithm (GWO). All models were trained, tested, and evaluated using different accuracy measures. LSTM-EBOA outperformed other models in predicting the permeate flux based on different accuracy measures. LSTM-EBOA had the highest coefficient of determination of 0.998 and 0.988 and the lowest root mean square error of 1.272 and 4.180 for training and test, respectively. It can be recommended that this paper provide a useful pathway for sizing parameters selection and predicting the performance of MD systems that makes an optimally designed model for predicting the freshwater production rates without costly experiments.

In this numerical study, the performance of ceramic-based mullite hollow fiber (HF) membranes in a direct contact membrane distillation (DCMD) process was evaluated. Three types of membranes were tested: (i) hydrophobic membrane C8-HFM, (ii) rod-like omniphobic membrane (C8-RL/TiO2), and (iii) flower-like omniphobic membrane (C8-FL/TiO2). The CFD model was developed and validated with experimental results, which were performed over a 500 min period. The initial mass flux of C8-HFM was 30% and 9% higher than that of C8-FL/TiO2 and C8-RL/TiO2, respectively. However, the flower-like omniphobic membrane C8-FL/TiO2 had the lowest drop in flux, around 11%, while the rod-like omniphobic membrane C8-RL/TiO2 had a 15% reduction, both better than the 23% reduction in the hydrophobic membrane C8-HFM over the 500 min. The study also analyzed the impact of fouling by examining the variation in mass transfer coefficient (MTC) over time. The results indicated that the ceramic-based mullite HF membranes with TiO2 flowers and rods demonstrated a high resistance to fouling compared to C8-HFM. The modified membranes could find applications in the desalination and handling of seawater samples containing organic contaminants. The CFD model's versatility can be utilized beyond the current investigation's scope, offering a valuable tool for efficient membrane development solutions, particularly for challenges such as the presence of organic contaminants in seawater. [ABSTRACT FROM AUTHOR]

Energy drives the growth, transformation, and economic development of every nation. The vitality of human existence and progress hinges on the accessibility of both energy and water resources. As freshwater resources are diminishing, therefore, desalination needs have increased. In solar membrane distillation systems, the key challenge is maintaining the intake water temperature in the membrane distillation system with fluctuating solar radiation intensity which affects the distillate water quantity and quality. The objective of this study is to enhance and optimize a mathematical model for analyzing a cutting-edge solar-integrated PV/T-DCMD system. In this innovative integration, the direct contact membrane distillation intake water temperature is derived from the photovoltaic thermal output. The integration of direct contact membrane distillation with photovoltaic thermal systems represents a cost-effective and technologically advantageous concept. As the water temperature increases, there is a notable improvement in the evaporation efficiency of PV/T-DCMD systems, with an increase from 35.08% to 42.01%. Additionally, there is a reduction in specific thermal energy consumption, decreasing from 1,192 to 1,386 kWh/m³ as a consequence of the elevated feed water temperature. [ABSTRACT FROM AUTHOR]

Introduction: Membrane distillation (MD) is a promising technique for desalination, capable of utilizing low-grade heat. However, MD faces some challenges such as temperature polarization. To overcome these issues, direct solar MD with localized heating (LHMD) has emerged as a cost-effective and efficient solution by leveraging solar energy. Methods: This study focuses on process optimization of LHMD using computational fluid dynamics (CFD) modeling. CFD simulation was applied to investigate the fluid behavior, heat transfer, and mass transfer within the system. Several key factors, including module geometry, process configuration, solar irradiation, feed flow rate, and feed temperature are investigated. Results: The effects of these parameters on the distillate production rate, thermal behavior, and energy efficiency, are evaluated for optimization. At the optimal conditions, 1m2 membrane in a module with a length of 50 cm and a channel height of 1.5mm under a counter-current flow generates 12 L drinking water per day, which meets the basic drinking water demands for 6 people. Over 70% gain output ratio can be achieved when the feed temperature is more than 20°C, the feed velocity is 1-1.5 mm/s, and the feed salinity is less than 1000 mol·mâ?'3. This setup can also produce 6 L of distilled water per day when a water with a salinity six times higher than seawater if the feed velocity is sufficiently low. Discussions: The main feature of the localized heating is the reverse temperature polarization on the feed side, leading to the increase in energy efficiency and the ease of scale-up. [ABSTRACT FROM AUTHOR]

Membrane desalination (MD) is an efficient process for desalinating saltwater, combining the uniqueness of both thermal and separation distillation configurations. In this context, the optimization strategies and sizing methodologies are developed from the balance of the system's energy demand. Therefore, robust prediction modeling of the thermodynamic behavior and freshwater production is crucial for the optimal design of MD systems. This study presents a new advanced machine-learning model to obtain the permeate flux of a tubular direct contact membrane distillation unit. The model was established by optimizing a long-short-term memory (LSTM) model by an election-based optimization algorithm (EBOA). The model inputs were the temperatures of permeate and the feed flow, and the rate and salinity of the feed flow. The optimized model was compared with other optimized LSTM models by sine–cosine optimization algorithm (SCA), artificial ecosystem optimizer (AEO), and grey wolf optimization algorithm (GWO). All models were trained, tested, and evaluated using different accuracy measures. LSTM-EBOA outperformed other models in predicting the permeate flux based on different accuracy measures. LSTM-EBOA had the highest coefficient of determination of 0.998 and 0.988 and the lowest root mean square error of 1.272 and 4.180 for training and test, respectively. It can be recommended that this paper provide a useful pathway for sizing parameters selection and predicting the performance of MD systems that makes an optimally designed model for predicting the freshwater production rates without costly experiments. [ABSTRACT FROM AUTHOR]

Nanoporous membranes offer significant advantages in direct contact membrane distillation applications due to their high flux and strong resistance to wetting. This study employs molecular dynamics simulations to explore the performance of membrane distillation in a single nanopore, mainly focusing on wetting behavior, liquid entry pressure, and membrane flux variations across different concentrations and types of salt solutions. The findings indicate that increasing the NaCl concentration enhances the wetting of membrane pores, thereby decreasing the entry pressure of the solution. However, at the same salt concentration, the differences in wetting and liquid entry pressure among various salts, including CaCl2, KCl, NaCl, and LiCl, are minimal. The presence of hydrated ions significantly reduces membrane flux. As the concentration of NaCl solutions increases, the number of hydrated ions rises, thereby lowering the membrane flux of the salt solution. Furthermore, the type of salt has a pronounced effect on the structure of hydrated ions. Solutions with Ca2+ and Li+ exhibit the smallest first-layer radius of hydrated ions. Under the same salt concentration, KCl solutions demonstrate the highest membrane distillation flux, while CaCl2 solutions show the lowest flux.

Energy drives the growth, transformation, and economic development of every nation. The vitality of human existence and progress hinges on the accessibility of both energy and water resources. As freshwater resources are diminishing, therefore, desalination needs have increased. In solar membrane distillation systems, the key challenge is maintaining the intake water temperature in the membrane distillation system with fluctuating solar radiation intensity which affects the distillate water quantity and quality. The objective of this study is to enhance and optimize a mathematical model for analyzing a cutting-edge solar-integrated PV/T-DCMD system. In this innovative integration, the direct contact membrane distillation intake water temperature is derived from the photovoltaic thermal output. The integration of direct contact membrane distillation with photovoltaic thermal systems represents a cost-effective and technologically advantageous concept. As the water temperature increases, there is a notable improvement in the evaporation efficiency of PV/T-DCMD systems, with an increase from 35.08% to 42.01%. Additionally, there is a reduction in specific thermal energy consumption, decreasing from 1,192 to 1,386 kWh/m3 as a consequence of the elevated feed water temperature.

Membrane distillation (MD) is a technology that is emerging as a viable alternative to traditional desalination techniques. This study assessed the feasibility of using the direct contact membrane distillation (DCMD) configuration of MD to desalinate saline water of different concentrations. We considered the feed supply of Arabian Gulf seawater (AGS) sand oil field-produced water and used polypropylene (PP) and polyvinylidene fluoride (PVDF) membranes to consider their performance under different operating conditions, such as channel depth, flow rate, temperature, feed concentration, etc. Their performance was evaluated by determining the water flux relative to the volume of salt rejection. The results showed that the permeate flux increased to 32.4 from 10.1 L/m²·h when the temperature was raised from 45°C to 75°C. Additionally, the permeate flux decreased to13.6 from 27.3 L/m²·h and the reduction in flux was around fifty percent when the concentration of sodium chloride (NaCl) in the feed solution was increased to 26% from 0%. The experimental results obtained using oil field-produced water were highly encouraging. The permeate flux was 11.5 and 12.5 L/m²·h at 80°C and 85°C, respectively. The results indicated the enormous potential of DCMD to treat hypersaline oil field-produced water, with an overall rejection of salts reaching above 99%. In comparison, PP membranes had a higher salt rejection rate but lower water flux, while PVDF membranes had a lower salt rejection rate but higher water flux. This paper presents, for the first time, the results of a laboratory-scale study conducted in the State of Kuwait to treat AGS and oil-produced water using DCMD technology under Kuwait's prevailing conditions. This study's findings will lay the groundwork for conducting pilot-scale studies on AGS and oil-produced water not only in the Middle East region but globally. [ABSTRACT FROM AUTHOR]

Innovative self-supported flat-sheet polyvinylidene fluoride (PVDF) membranes were developed incorporating amphiphilic I-quartet Artificial Water Channels (AWCs) and applied for membrane distillation (MD) and Dyes Ultrafiltration (UF). The presence of AWCs was aimed to increase the amount of water within hydrophobic PVDF pores increasing water permeability and preserving high selectivity and consequently to improve the MD and dyes UF performances. We explored novel strategies in which water channels structures contribute to water cluster stabilization and the increase of water (vapors or liquid) within hydrophobic pore structures. With this novel strategy in mind, three PVDF polymer grades with different molecular weights as well as the variation of their mass concentration as well as of AWCs were studied to shed in light their influence on the water permeability using a dead-end filtration setting. An enhanced water permeability of 75.3 L.m-2.h-1.bar-1 was attained for the PVDF-AWC hybrid membrane prepared using 16 wt% PVDF (530,000 g/mol) and 0.05 wt% AWCs when compared with a reference membrane with a water permeability of 30.6 L.m-2.h-1.bar-1. The MD performances of both membranes were assessed using a 35 g/L NaCl aqueous solution to yield a salt rejection of 95.3% and 85.2%, respectively. Furthermore, both the reference and the PVDF-AWC membranes showed improved separation performance in terms of rejection efficiency and dye permeability for binary dyes mixture as compared to single dyes. Among all the tested membranes, while methylene blue was completely removed in both cases, the 14 wt% PVDF membrane incorporating 0.075 wt% AWC showed a methyl orange rejection efficiency of up to 99.8% compared to 98.4% for its reference membrane. This hybrid membrane also displayed an almost doubled filtered dye feed permeability of 84 L.m-2.h-1.bar-1, compared to 40 L.m-2.h-1.bar-1 for its 14 wt% PVDF reference membrane. [ABSTRACT FROM AUTHOR]

Unlike steam turbines, electricity production in gas turbines is inherently independent of freshwater consumption. However, the thermal efficiency of gas turbines decreases as the temperature of input air increases. As a result, many methods of cooling the inlet air require the use of fresh water. Moreover, when it comes to humid gas turbine technology, the practice of injecting steam or humid air into the turbine to improve its thermal efficiency and output power consumes a substantial amount of freshwater. Therefore, reducing the use of fresh water to enhance the output power and thermal efficiency of gas turbines can be a necessary option, especially in hot and dry regions. Alternatively, considering the significant amounts of waste heat in gas turbines, one solution to reduce fresh water consumption is to connect them to thermal desalination units. However, conventional thermal desalination is only practical for seawater desalination in coastal areas. Therefore, this study explores the possibility of linking a direct contact membrane distillation (DCMD) unit to a Steam-injected gas turbine (STIG), which can use high salinity water sources like reverse osmosis (RO) brine in inland regions. The freshwater generated by the DCMD is used to chill the input air to the compressor and produce steam injected within the turbine. Simulation results show that this connection can raise the net output power by [9 to 17.2] MW and thermal efficiency by [3.3 to 15.6] % for compressor pressure ratios between [5 to 30], when compared to a simple gas turbine.

[Display omitted] • Neural networks have a great capability for modeling solar-driven DCMD systems. • Permeate flux, efficiency, and GOR were predicted using MLP and LSTM models. • K-fold cross-validation method was used for accurate hyper-parameter tuning. • MLP outperformed the LSTM model for dynamic modeling of the solar DCMD systems. • Models' accuracy for GOR enhanced significantly with increasing the data samples. Accurate modeling of solar-driven direct contact membrane distillation systems (DCMD) can enhance the commercialization of these promising systems. However, the existing dynamic mathematical models for predicting the performance of these systems are complex and computationally expensive. This is due to the intermittent nature of solar energy and complex heat/mass transfer of different components of solar-driven DCMD systems (solar collectors, MD modules and storage tanks). This study applies a machine learning-based approach to model the dynamic nature of a solar-driven DCMD system for the first time. A small-scale rig was designed and fabricated to experimentally assess the performance of the system over 20 days. The predictive capabilities of two neural network models: multilayer perceptron (MLP) and long short-term memory (LSTM) were then comprehensively examined to predict the permeate flux, efficiency and gain-output-ratio (GOR). The results showed that both models can efficiently predict the dynamic performance of solar-driven DCMD systems, where MLP outperformed the LSTM model overall, especially in the prediction of efficiency. Additionally, it was indicated that the accuracy of the models for the prediction of GOR can be significantly improved by increasing the size of the dataset. [ABSTRACT FROM AUTHOR]

Through experiments, the effect of membrane material selection and operating conditions on permeate fluxes in direct contact membrane distillation (DCMD) desalination was investigated. The experiment used a plate and frame membrane module, and with nine different hydrophobic porous membranes, a comparative analysis of the desalination performance of 3 wt% NaCl solution was performed. The results of this experiment were compared to find out the effect of different materials, pore sizes and membrane thicknesses on the permeate flux under same operating conditions. Further, a three-factor, three-level orthogonal experiment was designed. The effects of hot-side temperature, hot-side inlet flow and cold-side inlet flow on the permeate flux of PTFE membranes with a pore size of 0.22 μm were investigated when the temperature on the cold side was set at 20 °C. The results showed that in the DCMD experiments, both PTFE and PVDF membranes performed well, and that hot-side inlet temperatures and cold-side inlet flow rates had significant effects on the permeate flux. [ABSTRACT FROM AUTHOR]

A novel polyethersulfone (PES) membrane was prepared for desalination and treating saline feed solution containing humic acid in membrane distillation. PES has been selected to fabricate specialized membranes for direct contact membrane distillation, and membrane structure and characteristics have been controlled by dope solution composition and exposure time to water vapor during the phase inversion step. Since PES membranes are vulnerable to wetting, surface modification for hydrophobicity has been applied by a novel method inspired by lotus. This method uses a layer‐by‐layer surface modification of polydopamine, silver nanoparticles, and 1‐dodecanethiol to create adhesion, hierarchical roughness, and hydrophobicity. In dopamine polymerization, an oxidant has been added to improve the quality and speed of the process. Membranes were successfully fabricated and modified; the best‐case membrane with 30% triethylene glycol content and 30 s exposure time to water vapor showed outstanding results with 12.57 kg/h.m2 mass flux and 99.7% salt rejection in desalination also showed good results in treating saline feed containing humic acid with 10.02 kg/h.m2 flux and 99.71% rejection. The fabricated hydrophobic membrane's long‐term results showed promising and stable performance for commercial applications. [ABSTRACT FROM AUTHOR]

Membrane distillation (MD) assisted by heat pump exhibits a favorable energy performance in water production, but it consumes huge precious electricity. In this work, a nanofluid filtered concentrating photovoltaic/thermal (CPV/T) technology is proposed to integrate with heat pump membrane distillation (HPMD) system for electricity/water cogeneration. Solar energy cascade utilization is considered in the system where electricity generated by CPV/T powers heat pump for MD heat recovery, and the collected thermal energy is used to heat seawater. A comprehensive study is carried out by establishing models of the receiver, direct contact membrane distillation (DCMD) and heat pump to investigate the performance of the nanofluid filtered solar membrane distillation system using heat pump. Results show that the seawater of 350.3 K is fed to the DCMD module while the electrical efficiency is above 12.2%. MD parametric analysis and equivalent specific thermal energy consumption (eSTEC) optimization are performed. We found that HPMD operates at the lowest eSTEC of 607.8 kWh·m−3 at heating temperature of 338 K and feed flow rate of 0.04 kg s−1. An overall system efficiency of 61% is obtained, and the comparison of permeate flux and energy consumption demonstrates advantages of the proposed system over other hybrid MD technologies. [ABSTRACT FROM AUTHOR]

Membrane distillation is a new desalination process that uses low-grade heat to produce clean water. Membrane distillation (MD), in contrast to energy conversion with reverse osmosis, uses the excess heat produced by the Brayton cycle for desalination processes without the need for great energy. The Brayton cycle of sCO2 is viewed as a viable key motivator of the integrated power system, heating, and cooling, with the potential to boost efficacy. Because of its compact construction and great efficiency, in recent decades, it has been used forseveral heat sources. In this study, a literature study was conducted related to membrane distillation with a direct-contact process and a closed Brayton cycle of supercritical CO2 for the cogeneration of water.

Direct contact membrane distillation (DCMD) is an emerging technology gaining attraction in seawater desalination and concentration of aqueous solutions. In this study, a facile surface modification strategy using hydrophobic ZIF-8 and a fluoroalkylsilane (FAS) was employed to improve the performance of commercial PVDF and PVDF/PTFE blend membranes. The PVDF/PTFE membrane modified using 10 wt./vol % hydrophobic ZIF-8 and 1 H, 1 H, 2 H, 2 H-perfluorooctyltriethoxysilane (PFOTES) exhibited the highest water contact angle (121 ± 4.7°), improved surface roughness (51.6 ± 1.4 nm), most significant vapor flux (17.6 ± 2 L/m2h), and salt rejection of 99.98% with 10,000 ppm NaCl synthetic feed solution at the optimum operating conditions. The surface-engineered membranes exhibited excellent anti-fouling (360 minutes) and anti-wetting performance (240 minutes) when challenged with saline feed solution containing 50 ppm sodium alginate solution and 0.1 mM sodium dodecyl sulfate, respectively. The surface engineered membranes produced permeate of uniform quality for>10 h and could recover~31% water during actual seawater desalination (10 h). Moreover, these membranes could concentrate propylene glycol by a factor of 1.24 within 6 h and retain>80% of it. This facile surface modification strategy holds an excellent potential to be further explored for commercial applications. [ABSTRACT FROM AUTHOR]

Membrane Distillation (MD) is an emerging separation technology that has gained considerable interest in wastewater treatment. In this work, surface-modified poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) electrospun nanofibrous membranes were investigated for their potential to recover water from emulsified wastewater in direct contact membrane distillation (DCMD) mode. The modified electrospun membranes displayed a water contact angle of 130.5 ± 2° and water flux of 4.67 LMH with 99.9% rejection even when challenged with a 25000 ppm NaCl solution. However, membrane fouling and subsequent loss of permeate quality were observed within 120 minutes when emulsified wastewater (oil: surfactant-1:10 and 1000 ppm NaCl) was used as feed. Low-pressure nanofiltration (6 bar) was reported as a pre-treatment technology with thin-film nanocomposite (TFN) membranes incorporating Nickel-Aluminum Layered Double Hydroxide (Ni-Al LDH) nanoparticle on the polyamide layer. The TFN membranes were extensively characterized, and membrane N2 (0.01 wt.% Ni-Al LDH) exhibited a pure water permeance of 2.21 LMH/bar, 68% NaCl rejection, and 97% oil rejection. The integrated NF-MD process proved to be a robust technology and could remove 100% NaCl and 98.2% TOC for up to 300 minutes of operation. The proposed integrated technology holds the further potential to be investigated further. [ABSTRACT FROM AUTHOR]

Hydrophobic nano‐fumed silica (NFS) was incorporated in polyvinylidene fluoride (PVDF) hollow fiber (HF) membrane for improving direct contact membrane distillation (DCMD) performance. The NFS/PVDF mixed matrix hollow fiber membrane was fabricated by the phase inversion process. The potential effects of increasing the percentage of NFS additive (0–6 wt.%) in the dope solution on the hollow fiber membrane characteristics such as viscosity, membrane morphology, porosity, hydrophobicity, Fourier transformed infrared spectroscopy, and permeability were investigated. The performance outcomes showed that the dope solution incorporated with 1.5 wt.% NFS exhibited the most promising HF membrane for membrane distillation (MD). The optimal HF membrane demonstrated the highest flux through shorter and narrower finger‐like structure formation and targeted high porosity. The addition of NFS particle content in the dope solutions enhanced the hydrophobicity of the fabricated membranes while slightly decreasing the porosity due to increasing the viscosity of the dope solution. With a steady flux of 9.25 kg/m2 h compared with the neat membrane at 70°C/20°C of feed/permeate temperatures, 8 h operation, and above 99.9% salt rejection, this PVDF/NFS mixed matrix hollow fiber membrane could be of excellent potential and sustainability in desalination process through DCMD. [ABSTRACT FROM AUTHOR]

Biofouling in membrane distillation (MD) has several repercussions, including reduced efficiency of the MD process and limiting membrane life. Additionally, the evaluation of MD biofouling using treated effluents from wastewater treatment plants remains an unexplored area. Thus, biofouling formation and development in a long term MD process (15 days) using treated effluent from a wastewater treatment plant was explored in this study. The results revealed that flux decline occurred in four phases: i) initial decline (0–1 d), ii) gradual decline (1–5 d), iii) progressive decline (5–10 d), and iv) rapid decline (10–15 d). Liquid Chromatography-Organic Carbon Detection (LC-OCD) analysis demonstrated that the treated effluent contained humic-like substances, which deposited on the membrane surface in phase 1. Whereas biopolymers development on the membrane surface in phase 2 and 3 was linked to biofouling. Microbial community analysis revealed that the initial colonisers were predominantly thermophilic bacteria, which were different from the microbial community of the treated effluent. The biofilm-forming bacteria included Schlegelella , Meiothermus , and Vulcaniibacterium. These microorganisms proliferate and release excessive extracellular polymeric substances (EPS), leading to the development of mature biofilm on membrane surface. This helped in the deposition of organics and inorganics from the bulk feed, which led to microbial community succession in phase 4 with the emergence of the Kallotenue genus. The results suggested that organic substances and microbial communities on membrane surface at different stages in a long-term MD process had a significant influence on MD performance for high-quality wastewater reuse. • Flux decline occurred in four phases: initial decline, gradual decline, progressive decline, and rapid decline. • Conditioning film on MD membrane played a major role in biofouling development. • The biofilm-forming bacteria proliferate and released extracellular polymeric substances (EPS). • Microbial community succession occurred in 15-day membrane sample with dense foulant layer. [ABSTRACT FROM AUTHOR]

• Integrates MSR and PWR with DCMD, MSFD, and RO desalination technologies. • Hybrid systems enable load following and desalination when grid demand changes between 90 and 340 MW. • MSR hybrids generate up to 60% more water compared to PWR hybrids. • MSR-RO hybrid system has the lowest levelized cost of water at 1.13 USD/ m 3 • MSR-RO hybrid system reduce C O 2 emissions by 682,000 tons annually. Nuclear hybrid energy systems (NHES) have the potential to provide dependable and emission-free electricity to the grid while also increasing the flexibility and reliability of the electrical grid. Molten salt reactor (MSR) technology can provide consistent, carbon-free electricity while also increasing efficiency, security, and sustainability and reducing nuclear waste. This study investigates the integration of Molten Salt Reactors (MSR) and conventional Pressurized Water Reactors (PWR) with desalination technologies: Direct Contact Membrane Distillation (DCMD), Multi-Stage Flash Distillation (MSFD), and Reverse Osmosis (RO). Dynamic first-principles models were developed and tested using real grid data from the New York Independent System Operator. The results demonstrate that nuclear power is capable of flexibly responding to changing grid demand while simultaneously producing clean water, particularly during periods of low electricity demand. The MSR-RO system was found to be the most efficient in electricity generation and water production, and all hybrid systems reduced CO2 emissions by 356,000 to 682,000 tons annually. Economic analysis reveals that nuclear desalination technologies are cost-competitive with conventional systems, especially when paired with RO. These findings confirm the technical feasibility and environmental benefits of nuclear hybrid systems for sustainable electricity and water production. [ABSTRACT FROM AUTHOR]

Membrane scaling is a non-negligible problem for membrane distillation (MD) in the treatment of high-salinity wastewater (e.g., calcium sulfate and calcium carbonate). In this study, fullerene (C60) was adhered to a polyvinylidene fluoride (PVDF) membrane using a polydimethylsiloxane (PDMS) solution to create a micro-nano structure, fabricating the C60/PDMS-PVDF membrane. This membrane was then re-immersed in a PDMS solution to further reinforce the C60 nanoparticles on the surface, forming the PDMS/C60/PDMS-PVDF membrane. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize the membrane surface morphology. Fourier transform infrared (FT-IR) was used to explore the membrane chemical composition. Liquid entry pressure (LEP) and water contact angle (WCA) measurements were employed to assess the membrane wettability. The results showed that C60-modification created the micro-nano structure on the membrane surface. The WCA of the PVDF membrane was 112.7 ± 2.4°, with a sliding angle far greater than 90°, whereas the PDMS/C60/PDMS-PVDF membrane exhibited a WCA of 147.9 ± 3.2° and a sliding angle of 6.3°. Compared to the virgin PVDF membrane, the LEP value of the PDMS/C60/PDMS-PVDF membrane increased from 68.4 ± 2.7 kPa to 87.2 ± 3.3 kPa. In direct contact membrane distillation (DCMD), a CaSO 4 solution (2 g/L) was used to test the membrane performance. After 48 hours of operation, the flux of the PDMS/C60/PDMS-PVDF membrane remained at approximately 3.57 kg/(m2·h), and the salt rejection rate was over 99.96 %. This could be attributed to the C60 modification forming a micro-nano structure on the membrane surface, which trapped an air layer. This air layer could reduce the contact area between the crystal and the membrane, decrease nucleation probability, and shorten the residence time of liquid on the membrane surface. Additionally, the PDMS/C60/PDMS-PVDF membrane exhibited superior stability during the ultrasonic destruction experiment due to the encapsulation of PDMS. In summary, a novel hydrophobic membrane with a micro-nano structure was fabricated through C60 modification, offering superior anti-scaling properties and stability in treating high-salinity wastewater. [Display omitted] • C60 modified PVDF membrane showed excellent anti-scaling performance. • C60 encapsulation by PDMS in case of C60 detachment. • C60 modified PVDF membrane had stable performance when treating CaSO 4 solution. [ABSTRACT FROM AUTHOR]

Hydrophobic metakaolin-based flat sheet membrane was developed via phase inversion and sintering technique and modified through 1H,1H,2H,2H-perfluorooctyltriethoxysilane grafting agents. The prepared membrane was characterized by different techniques such as XRD, FTIR, SEM, contact angle, porosity, and mechanical strength. Their results indicated that the wettability, structural, and mechanical properties of the prepared membrane confirm the suitability of the material for membrane distillation (MD) application. The prepared metakaolin-based flat sheet membrane acquired hydrophobic properties after surface modification with the water contact angle values of 113.2° to 143.3°. Afterward, the membrane performance was tested for different sodium chloride aqueous solutions (synthetic seawater) and various operating parameters (feed temperature, feed flow rate) using direct contact membrane distillation (DCMD). Based on the findings, the prepared membrane at metakaolin loading of 45 wt.% and sintered at 1,300 °C was achieved the best performance with >95% salt rejection and permeate flux of 6.58 ± 0.3 L/m2 · h at feed temperature of 80 °C, feed concentration of 35 g/L, and feed flow rate of 60 L/h. It can be concluded that further optimization of membrane porosity, mechanical, and surface properties is required to maximize the permeate flux and salt rejection. HIGHLIGHTS The flat sheet ceramic membrane was synthesized for DCMD.; The sintering process was a much more influential factor in the membrane shrinkage.; The flat sheet ceramic membrane was successfully grafted with PFAS molecules.; Effect of operating variable on the permeate flux and salt rejection.; It was found that the feed temperature was the most significant operating variable affecting the performance of the DCMD.;

Abstract Membrane distillation (MD), as a hybrid desalination technology with super-hydrophobic characteristics, has been emerging in the recent year. In this contest, the outstanding features of carbon-based nanomaterials have promising potential to contribute to the MD process evolution. This work presented an endeavor to impart the super-hydrophobic features of powder activated carbon (PAC) into poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membranes for DCMD applications. The FTIR indicates that the CNM was successfully coated onto the PVDF-HFP membrane which leading to higher contact angle values (from 83° to 124°, porosity (45% 86.9%) and water distillate flux at each increment in the PAC loading weigh. The novel coated membranes with 30 mg CNM led to an enhancement of the permeate flux (higher fluxes were obtained at higher CNMs loading) presented fluxes around 77 L/m2.h and exhibited a high salt rejection (> 99.9%) in most cases.

Desalinization of seawater can be achieved by membrane distillation techniques (MD). In MD, the membranes should be resistant to fouling, robust for extended operating time, and preferably provide a superhydrophobic surface. In this work, we report the preparation and characterization of a robust and superhydrophobic polyvinylidene fluoride membrane containing fluoroalkyl-capped CuONPs (CuONPs@CF) in the inner and fluorinated capped silicon oxide nanoparticles (SiO2NPs@CF) on its surface. SiO2NPs@CF with a mean diameter of 225 ± 20 nm were prepared by the sol method using 1H,1H,2H,2H-perfluorodecyltriethoxysilane as a capping agent. Surface modification of the membrane was carried out by spraying SiO2NPs@CF (5% wt.) dispersed in a mixture of dimethyl formamide (DMF) and ethanol (EtOH) at different DMF/EtOH % v/v ratios (0, 5, 10, 20, and 50). While ethanol dispersed the nanoparticles in the spraying solution, DMF dissolved the PVDF on the surface and retained the sprayed nanoparticles. According to SEM micrographs and water contact angle measurements, the best results were achieved by depositing the nanoparticles at 10% v/v of DMF/EtOH. Under these conditions, a SiO2NPs covered surface was observed with a water contact angle of 168.5°. The water contact angle was retained after the sonication of the membrane, indicating that the modification was successfully achieved. The membrane with SiO2NPs@CF showed a flux of 14.3 kg(m2·h)−1, 3.4 times higher than the unmodified version. The method presented herein avoids the complicated modification procedure offered by chemical step modification and, due to its simplicity, could be scalable to a commercial membrane. [ABSTRACT FROM AUTHOR]

Hydrophobic membranes prepared using Poly (tetrafluoroethylene) (PTFE) along with Poly (1,4-phenylene ether ether-sulfone) and zinc oxide nanoparticle was used in membrane distillation. To examine seawater purification, prepared polymeric membranes were evaluated, tested, and used in a lab-scale direct contact membrane distillation arrangement. These membranes which are synthesized using the electrospinning method have good mechanical and thermal stability. To understand prepared membranes’ desalination performance, the physicochemical properties of the seawater were analyzed before and after membrane distillation. The salt rejection remained at 99% and the highest energy efficiency of the system observed is 67.3%. [ABSTRACT FROM AUTHOR]

Through experiments, the effect of membrane material selection and operating conditions on permeate fluxes in direct contact membrane distillation (DCMD) desalination was investigated. The experiment used a plate and frame membrane module, and with nine different hydrophobic porous membranes, a comparative analysis of the desalination performance of 3 wt% NaCl solution was performed. The results of this experiment were compared to find out the effect of different materials, pore sizes and membrane thicknesses on the permeate flux under same operating conditions. Further, a three-factor, three-level orthogonal experiment was designed. The effects of hot-side temperature, hot-side inlet flow and cold-side inlet flow on the permeate flux of PTFE membranes with a pore size of 0.22 μm were investigated when the temperature on the cold side was set at 20 °C. The results showed that in the DCMD experiments, both PTFE and PVDF membranes performed well, and that hot-side inlet temperatures and cold-side inlet flow rates had significant effects on the permeate flux.

HFP-co-PVDF/N6 hydrophobic/hydrophilic dual-layer membrane was used to study desalination with direct contact membrane distillation (DCMD). A one-dimensional (1-D) model was proposed to predict the flux and thermal efficiency. Heat and mass transfer equations were solved numerically for the combined hydrophilic and hydrophobic layers. The membrane characteristics of the hydrophobic layer were considered for the calculation of the mass transfer coefficients, while the hydrophilic layer was ignored since it was assumed to be filled with water. However, the hydrophilic layer was taken into account during the calculations of conductive heat transfer. Therefore, the equations are different, compared to single-layer hydrophobic membranes. It was found that with the same hydrophobic membrane characteristics, the single-layer membranes performed with better flux and thermal efficiency than the dual-layer membranes. Furthermore, the improvement of flux and thermal efficiency by an addition of the hydrophilic layer has not been observed experimentally, and it is suggested that the improved performance for dual-layer membranes reported previously is due to improved permeability by using thinner and more porous hydrophobic layers that can be mechanically reinforced by the hydrophilic layer. The validation of the model was conducted by comparing the experimental results for single- and dual-layer membranes with the modelling results. The predicted flux and thermal efficiency by the modelling were within 10% error to the experimental results. HIGHLIGHTS Mathematical models for predicting the flux and energy efficiency of dual-layer membranes.; Experimental results have been used to validate the models.; It is found that the thickness of the hydrophilic layer has a large effect on the flux and thermal efficiency.;

In water-gap membrane distillation (WGMD), natural convection within the water gap significantly impacts performance and thermal efficiency. Previous studies have used empirical or modified empirical correlation models to predict the Nusselt number within the water gap, investigating how natural convection affects WGMD performance and thermal efficiency. However, these models are specific to certain operating conditions, limiting their application in developing a comprehensive numerical model for the WGMD process. To address this limitation, we developed a numerical model by integrating a two-dimensional natural convection model within the water gap. Experimental investigations were conducted across a wide range of feed temperatures and water gap sizes to assess the influence of key operating parameters on performance. To validate the effectiveness of the proposed numerical model, the experimental results were compared with those from the proposed model and with results from numerical models used in previous studies. The proposed numerical model demonstrated a maximum deviation of 8.5 % from the measured data, whereas the numerical models used in previous studies exhibited deviations of 22.9 %. In addition, the flow characteristics within the water gap were analyzed through isotherms and streamlines, and the improved thermal efficiency of WGMD compared to direct contact membrane distillation (DCMD) was explored. [Display omitted] • A numerical model of the WGMD integrating a 2D natural convection model was developed. • Using the empirical Nusselt number correlation leads to large deviations from the measured data. • The proposed model showed a maximum deviation of 8.5 % compared with the measured data. • Permeate flux and performance ratio remains stable above water gap size of 8 mm. • Flow characteristics within water gap were analyzed using isotherms and streamlines. [ABSTRACT FROM AUTHOR]

Membrane distillation (MD) can treat high-salinity brine. However, the system's efficiency is hindered by obstacles, including salt scaling and temperature polarization. When properly implemented, surface patterns can improve the mass and heat transfer in the boundary layer, which leads to higher MD efficiency. In this work, the performance of direct contact membrane distillation (DCMD) using Sharklet-patterned poly (vinylidene fluoride) (PVDF) membranes is investigated. Both non-patterned and patterned PVDF membranes are prepared by lithographically templated thermally induced phase separation (lt -TIPS) process with optimized conditions. Sharklet patterns on the membranes improve the DCMD performance: up to 17 % higher water flux and 35 % increased brine-side heat transfer coefficient. The scaling resistance of the membranes during DCMD is tested by both saturated CaSO 4 solution and hypersaline NaCl solutions. Patterned PVDF membranes show an average of 30 % higher water flux and up to 45 % lessened flux decline over time compared with non-patterned membranes when treating high-concentration brines. Post-mortem analysis reveals that Sharklet-patterned membranes display less salt-scaling on surfaces with smaller-sized CaSO 4 and NaCl crystals, maintain a relatively cleaner surface, and exhibit better retention of hydrophobicity. [Display omitted] • Sharklet-patterned PVDF membranes were fabricated with patterning fidelity up to 80 %. • The effects of Sharklet patterns on DCMD performances were quantified. • The Sharklet improves flux by 17 % and brine-side heat transfer coefficient by 35 %. • The Sharklet improves membranes' robustness when treating hypersaline feeds. [ABSTRACT FROM AUTHOR]

• High vapor flux UHMWPE composite membranes were prepared by TIPS method. • Membranes prepared by 9.0 million molecular weight of UHMWPE have higher vapor flux. • TA-APTES nanospheres can co-deposit on UHMWPE membranes surface robustly. • TA-APTES nanospheres have abundant secondary reaction sites for fluorination. • Membranes have a high separation efficiency (99.98%) for high salinity anionic dyeing wastewater. Commercial flat sheet membranes have relatively low flux in membrane distillation. Here, a ultra-high molecular weight polyethylene (UHMWPE) composite membrane with high flux was prepared via thermally induced phase separation (TIPS) method for direct contact membrane distillation (DCMD). The UHMWPE membrane has low tortuosity (spherical structure) and low thickness to decrease the vapor mass transfer resistance. In addition, UHMWPE/decalin gel membrane washed in hot decalin (85℃) in order to increase the permeate flux, and the optimum membrane has the highest flux of 43.51 kg/(m2·h). In order to increase the anti-wetting properties of UHMWPE membranes, Tannic acid (TA) − 3-aminopropyltriethoxysilane (APTES) coating composed of abundant nanospheres is co-deposited on the surface of UHMWPE membrane to increase surface roughness. The subsequent fluorination process can decrease the surface energy and improve the anti-surfactant property. The optimum modified membrane has a water contact angle of 152.5°, and the permeate flux is 31.04 kg/(m2·h). Moreover, the membrane has high rejection (99.98 %) and high water recovery (82.87 %) over 60 h testing for high salinity anionic dyeing wastewater. [ABSTRACT FROM AUTHOR]

In direct contact membrane distillation (DCMD), heat and mass transfers occur through the porous membrane. Any model developed for the DCMD process should therefore be able to describe the mass transport mechanism through the membrane, the temperature and concentration effects on the surface of the membrane, the permeate flux, and the selectivity of the membrane. In the present study, we developed a predictive mathematical model based on a counter flow heat exchanger analogy for the DCMD process. Two methods were used to analyze the water permeate flux across one hydrophobic membrane layer, namely the log mean temperature difference (LMTD) and the effectiveness-NTU methods. The set of equations was derived in a manner analogous to that employed for heat exchanger systems. The obtained results showed that the permeate flux increases by a factor of approximately 220% when increasing the log mean temperature difference by a factor of 80% or increasing the number of transfer units by a factor of 3%. A good level of agreement between this theoretical model and the experimental data at various feed temperatures confirmed that the model accurately predicts the permeate flux values for the DCMD process.

• Hybrid system was studied numerically to produce freshwater and electricity. • Four different configurations were studied to reduce the temperature of the solar cell. • L-shape configuration has better cooling performance in cooling the HCPV system. • A simulation for a full solar module (21 cells) was performed. • The hybrid system can produce up to 540 W with permeate flux of 72.96 kg/m2.day. The rising demand for electricity and fresh water in remote regions has sparked a quest for innovative and sustainable solutions. This study delves into cooling a module with multi-junction high concentrator PV cells by integrating a heat exchanger and a direct contact membrane distillation unit (DCMD). The goal is to investigate the synergy between electricity and freshwater generation through numerical simulations. Among the four cooling configurations tested−straight rectangular and square microchannels, U-shape, and L-shape, the L-shape design proved the most effective, requiring minimal pumping power while yielding the highest electrical power generation compared to others. Consequently, the L-shape configuration was selected to cool a solar module housing 21 solar cells. Different coolant flow rates and solar concentration ratios (CRs) were examined. A mathematical model was developed to analyze the DCMD process, factoring in various bulk feed temperatures and feed water rates. Findings from the hybrid system indicated that operating at CRs below 250 was impractical due to low coolant water outlet temperatures. However, at a CR of 750, the optimal operating range ranged from 250 g/min to 450 g/min, resulting in a peak electrical power of 417.66 W and maximum permeate mass flux of 47.1 kg/m2.day. At a CR of 1000, the system achieved a maximum electrical output of 540 W with a permeate mass flux of 72.96 kg/m2.day. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to develop a general predictive mathematical model of direct contact membrane distillation (DCMD) for flat sheet module. This model, based on fundamental equations of mass and heat transfer, aims to predict the water permeate flux across the membrane and to investigate the influence of membrane characteristics such as its thickness, its length, the pore size and porosity, on the performance of DCMD process. All physical parameters implemented in the mathematical model have been estimated using appropriate temperature correlations. Obtained results revealed that doubling the thickness of the membrane decreases the permeate flux by an amount of 43% and increasing the membrane porosity by 20% yields an increase of the permeate flux by 40%. However, pore size as well as membrane length variations show no sensitive effect on permeate flux. A good agreement between this theoretical model and experimental data was observed for various feed temperatures. This suggests that this tool could be utilized efficiently to predict permeate flux values for DCMD process. [ABSTRACT FROM AUTHOR]

The present study dealt with the generation of freshwater through the direct contact membrane distillation (DCMD) technique, powered by an evacuated tube solar collector (ETSC). The major objective of the present work was to determine the optimum conditions of fluid flow rate and temperature for maximum freshwater productivity across both the feed and permeate sides of the membrane module. A flat hydrophobic membrane composed of polyvinylidene fluoride (PVDF) coated with Teflon was utilized for the DCMD process. The rate of freshwater production was examined with the variation in the feed/permeate flow rates (from 3 to 7 LPM) and feed temperature (from 45 °C to 75 °C) for a constant permeate-side temperature of 30 °C. The experimental results indicated that a maximum freshwater productivity of 45.18 kg/m2h was achievable from the proposed system during its operation with a high solar heated inlet feed temperature of 75 °C and mass flow rates of 7 LPM across both sides of the membrane. Further, a detailed assessment of the performance parameters indicated that the present solar-powered DCMD system exhibited a maximum evaporative efficiency of about 80% and temperature polarization coefficient (TPC) of 0.62 respectively. [ABSTRACT FROM AUTHOR]

A non-toxic and environmentally safe diluent, acetyl tributyl citrate, was employed to prepare poly (vinylidene fluoride)-co-hexafluoropropylene membranes via thermally induced phase separation. Effects of the polymer concentration on the phase diagram, membrane morphology, hydrophobicity, pore size, porosity and mechanical properties (tensile stress and elongation at break) were investigated. The results showed that the pore size and porosity tended to decrease with increasing polymer concentration, whereas the contact angle, liquid entry pressure and mechanical properties showed the opposite trend. In direct contact membrane distillation operation with 3.5 wt-% sodium chloride solution as the feed solution, the prepared membranes performed high salt rejection (> 99.9%). Furthermore, the prepared membranes retained excellent performance in long-term stability tests regarding the permeate flux and salt rejection. [ABSTRACT FROM AUTHOR]

This paper discusses the response surface methodology (RSM) study on a recent direct contact membrane distillation (DCMD) system. The DCMD system is reviewed due to its myriad attention on desalination process, especially on water treatment of high salinity and reclamation of industrial process water. The fundamental of DCMD, as well as the mass and heat transfer principles for modelling the system, are firstly explained and compared with previous studies. Then, the researcher highlighted the parameters involved in the modelling of DCMD process, such as feed temperature, velocity, and concentration, simultaneously with common membrane properties in mass and heat transfer models. The correlation of these frequently studied parameters with the conventional model was included and summarised. Subsequently, RSM was performed for the model development of the DCMD system, which included common design matrix applications, such as Box–Behnken, central composite design, and full factorial design. Finally, this work reviews the most recent application for the DCMD modelling of the model, comparing its experimental number runs, independent input number, model levels, and accuracy for optimising the DCMD process using RSM. [ABSTRACT FROM AUTHOR]

Membrane distillation (MD) is a standalone process to generate fresh water and is especially attractive when low-grade waste heat or renewable thermal energy is available. Surface wetting hinders the commercialization of Membrane distillation (MD) technology by deteriorating the permeate quality, thermal efficiency, and transmembrane flux. There is still a lack of understanding on how and to what extent the partially wetted membranes affect the performance of direct contact MD (DCMD) systems. It is of great importance to optimize the operating conditions under such conditions. The DCMD performance was addressed in the literature by considering non-wetted or fully wetted membranes. This study for the first time proposes a computational model to investigate the effect of membrane surface wetting ratio (R = Lwet/Ltotal) on the transmembrane (J) and thermal efficiency (η) of a DCMD module. Parametric and sensitivity analyses were performed to display the effect of system parameters (feed temperature, feed velocity, permeate temperature, permeate velocity, membrane thickness, and membrane surface wetting ratio) on the Key Performance Indicators (KPIs) of the DCMD module. The obtained results indicate that the permeate side temperature has more effect (more than twice) on KPIs in wetted membranes (∼30% and ∼15% rise in J and η) compared to the non-wetted ones (∼15% and ∼5% enhancement in J and η), and the negative effect of membrane surface wetting could be minimized by adjusting the permeate side operational conditions. The effect of membrane wetting ratio on the performance of the DCMD module in thin membranes (≤0.2 mm) and thick membranes (≥0.25 mm) strongly depends on the permeate and feed temperatures. The parametric and sensitivity analysis performed in this study will be beneficial to optimizing the operational conditions of MD systems for maximizing their performance and could serve as valuable guidelines in the development of efficient water desalination systems.

Membrane distillation (MD), as a hybrid desalination technology with super-hydrophobic characteristics, has been emerging in the recent year. In this contest, the outstanding features of carbon-based nanomaterials have promising potential to contribute to the MD process evolution. This work presented an endeavor to impart the super-hydrophobic features of powder activated carbon (PAC) into poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membranes for DCMD applications. The FTIR indicates that the CNM was successfully coated onto the PVDF-HFP membrane which leading to higher contact angle values (from 83° to 124°, porosity (45% 86.9%) and water distillate flux at each increment in the PAC loading weigh. The novel coated membranes with 30 mg CNM led to an enhancement of the permeate flux (higher fluxes were obtained at higher CNMs loading) presented fluxes around 77 L/m2.h and exhibited a high salt rejection (> 99.9%) in most cases. [ABSTRACT FROM AUTHOR]

Microporous membrane with a hydrophobic surface, high porosity, and narrow pore size distribution is the ideal membrane distillation (MD) membrane. The electrospun membranes for MD are a new type and effective way to seawater desalination. Herein, a novel polyvinylidene fluoride (PVDF)/tetrabutylammonium chloride (TBAC) electrospun nanofiber membrane (ENMs) fabricated apply to for direct contact membrane distillation (DCMD). Combine with the spinning condition, the characteristic and content of TBAC significant effect on the multimorphology structure of nanofiber. Therefore, the porous structure and morphology of PVDF/TBAC ENMs can be well‐designed by optimizing relative humidity and TBAC concentration in spinning process, three different structure nanofiber membranes are obtained. Lab‐scale setup is used to test membrane separation performance. The result indicates that the ultrafine ENMs with 0.025 mol L−1 TBAC presented a steady water flux of about 20.6 L m−2 h−1 and a high‐efficiency salt rejection rate of over 99%. PVDF/TBAC ENMs are expected to provide a solution for development of efficient water treatment membrane. [ABSTRACT FROM AUTHOR]

[Display omitted] • A low cost Mullite was utilized in fabrication of ceramic hollow fibre membrane. • Surface modification with fluoralkylsilane agent (FAS) was applied. • Modified membrane has a contact angle value of 139°. • Excellent performance of 99.99 % NaCl removal was achieved. A low-cost hydrophobic mullite hollow fibre membrane (Hy-MHFM) fabricated via phase inversion/sintering technique followed by fluoroalkyl silane (FAS) grafting is presented in this study. The prepared CHFMs were characterized before and after the grafting step using different characterization techniques. The pore size of the CHFM surface was also determined using ImageJ software. The desalination performance of the grafted membrane was evaluated in direct contact membrane distillation (DCMD) using synthetic seawater of varying salt concentrations for 2 h at various feedwater temperatures. The outcome of the evaluations showed declines in the permeate flux of the membrane at increasing feed concentration, as well as increased flux with increased feed temperature. The long-term stability of the membrane was achieved at time 20 h, feed temperature 60 °C, and permeate temperature 10 °C, the membrane achieved a salt rejection performance of about 99.99 % and a water flux value of 22.51 kg/ m2 h. [ABSTRACT FROM AUTHOR]