Saline Water Desalination Research Articles

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.

Unlocking desalination’s potential: Harnessing MXene composite for sustainable desalination

Amidst freshwater scarcity, desalination is an effective solution, elevating pure water to a paramount commodity. Researchers actively pursue cost-effective alternatives to traditional desalination methods, with solar steam-based technologies now-a-days. Herein we report the synthesis of hierarchical photothermal absorber consisting of Ti3C2Tx decorated polypropylene fiber (PPF) composite and further used for solar desalination applications. Ensuring system stability amidst temperature fluctuations, pH variations, and mechanical stresses is pivotal for optimal desalination and wastewater treatment performance. Seamless integration of components is imperative to achieve this. Structurally, the Ti3C2Tx MXene@PPF composite evaporator showcases impressive metrics, such as high evaporation rate of 4.63 kg m-2h−1 along with a remarkable solar-evaporation efficiency of 93.48 % when tested under 1 sun illumination. Moreover, the composite absorber exhibits good mechanical stability, exceptional chemical stability even under harsh conditions (such as acid and alkali environments), outstanding salt tolerance and maintained a consistent evaporation rate over extended durations. Also, the absorber achieves good mechanical properties. These findings underscore the Ti3C2Tx MXene@PPF composite evaporator’s potential as a groundbreaking material for solar steam generation, offering high efficiency and cost-effectiveness. Beyond saline water desalination, its salt-preserving attributes and filtration capabilities position it as a promising alternative for wastewater treatment. This study presents an innovative and scalable solar water purification system applicable to a diverse range of water contaminants and manufacture in a cost-effective way.

Process intensification in the direct contact membrane distillation (DCMD) desalination by patterning membrane surface: A CFD study

In this research, the impact of pattern geometry on the intensification of the performance of surface patterned membranes for saline water desalination by direct contact membrane distillation (DCMD) is investigated by computational fluid dynamics (CFD) simulation. The Comsol Multiphysics software was applied to solve the governing transport equations for heat, momentum, and mass transfer. The result of the model was validated by the published experimental data, and the maximum deviation was less than 10%. The target was to maximize the permeate flux by altering surface pattern geometry and dimensions. Based on the previous studies, a prism pattern was chosen in this work, and the influences of pattern type (3 types), pattern dimension (25-150 µm valley depth), and the distance between the valleys (0-400 µm) were studied on the temperature polarization coefficient (TPC) and DCMD permeate flux. The results showed that the pattern with a valley depth of 25 µm and a distance between the valleys of 300 µm had the best performance in DCMD operation. In this situation and feed temperature of 80°C, a TPC of 0.78 and a water flux of 49.3 kg/m2.h were attained. The characteristics of flow close to the patterned membrane surface were also investigated, and it was observed that there are weak shear stresses in the lower zone of the valleys, while stronger shear stresses are created in the upper regions that are responsible for improving the TPC and water flux in the patterned membranes.

De novo Cu-MOF@CNS nanocomposite coated on a cotton fibrils framework for sustainable solar-driven desalination.

Environmental researchers are extremely concerned about addressing the declining availability of drinking water, which is a critical issue in many nations. Solar-driven desalination is an emerging and pioneering renewable approach to reduce potable water scarcity that is suitable for remote locations, developing countries, and disaster zones as it does not require additional energy supply. However, there are still issues with the scalable preparation of photothermal materials, such as achieving low cost and widening the assortment of useful applications. Conventional carbon- and metal-based absorbers are intricate and fragile, which make them difficult to install and transport in places with minimal infrastructure. Thus, a universal process for creating adaptable solar evaporators is sorely required. Herein, we have come up with a holistic approach using a solar absorber (GJ-01(Cal)) derived from a Cu-MOF (HKUST-1) and carbon nanosheets (CNSs) for generating potable water from saline water using solar radiation. The as-synthesized material provides high-performance photothermal water evaporation when illuminated under solar irradiation at the air-water interface. Moreover, its porous structure, high photothermal conversion efficiency, rapid water flow, and heat insulation make it appropriate for saline water desalination. CNS play a pivotal role in improving the photothermal features of the solar absorber (GJ-01(Cal)) in terms of conjugation to promote Cu(0) species and pyrrolic nitrogen (P-N) amplification and thereby enrich the p-type nature of the absorber's triphasic configuration. With these photothermal factors, the localised surface plasmon resonance (LSPR) of electrons increases and achieves high solar spectrum absorption. The GJ-01(Cal) was further coated on porous cotton fibrils (CF) that regulate photothermal interfacial evaporation (PTIE) by allowing water transportation via capillary action. This assemblage of the nanocomposite on CF efficiently evaporates water at a higher surface temperature of ∼47 °C under one solar illumination, achieving 4.23 kg m-2 h-1 of evaporation flux and 96.5% light-to-heat conversion efficiency. Interestingly, the GJ-01(Cal) coated over CF can be recycled at least 10 times. Additionally, it offers scalable production for higher photothermal efficiency with a flexible substrate as a solar evaporator and is beneficial for society paving new horizons towards a sustainable environment.

Effective design of sustainable energy productivity based on the experimental investigation of the humidification-dehumidification-desalination system using hybrid optimization

Reliable and cost-effective industrial-based sustainable desalination technologies are crucial for efficient and effective desalination of saline water. Seawater desalination emerges as a vital treatment, with humidification-dehumidification identified as a promising technology due to its simple, low-maintenance design and compatibility with renewable energy sources. The present work was developed using a large-scale experimental test rig based on the performance of a humidification-dehumidification system operated by the heat pump. As such, the study presents an advanced approach for optimizing humidification-dehumidification desalination systems using hybrid machine learning optimization techniques. The effectiveness of a neuro-fuzzy model, a decision algorithm based on a boosted tree, and a simple averaging ensemble in enhancing the performance of humidification-dehumidification systems were investigated. Experimental data includes cold water flowrate (L/min), hot water flowrate (L/min), inlet air temperature (°C), inlet cold water temperature (°C), inlet hot water temperature (°C), and inlet air relative humidity (%) as input variables combination and freshwater productivity (L/h), recovery ratio (%) as target variables. Several statistical indicators were used to evaluate the models’ prediction skills; similarly, a 2-dimensional Taylor diagram and error-radial plot were also utilized. In the calibration phase, boosted tree models slightly outperform neuro-fuzzy models, particularly for recovery ratio, demonstrating high accuracy and low bias. However, all models exhibit robust predictive accuracy in the verification phase, especially for recovery ratio, emphasizing their potential in generalizing to unseen data. The result indicated that the boosted tree outperformed others with Nash–Sutcliffe Efficiency = 94 % and 88 % for recovery ratio and freshwater productivity, respectively. The simple averaging ensemble shows marginal improvement with 95 % accuracy for the recovery ratio. Integrating hybrid artificial intelligence optimization with humidification-dehumidification desalination systems marks a transformative step in addressing freshwater shortages. By utilizing cutting-edge machine learning techniques, we achieve a more efficient, accurate, and reliable prediction of desalination performance.

Single modular flow-electrode capacitive deionization using modified Prussian blue analogues as cation intercalation electrode for continuous water desalination.

Ion back-diffusion hinders the practical application of conventional flow-electrode capacitive deionization (FCDI) under long-term operational conditions. To address this challenge, the present study integrated cation intercalation deionization (CID) with FCDI. A novel PFCDI-CID system was developed by utilizing a modified Prussian blue analogues owing to their enhanced rheological and electrochemical properties. The PFCDI-CID system achieved a high charge efficiency of 89.77% and an energy-normalized removal salt of 0.69 mol kJ-1 in single-cycle (SC) mode with the flow electrodes mass fraction of 2% and a desalinized water chamber-to-concentrated saline water chamber ratio of 2:1. Furthermore, under continuous operation for 12 h in SC mode, the PFCDI-CID system maintained stable desalination performance within the first 2 h. Over an extended duration, the average charge efficiency of the PFCDI-CID system was maintained at 88.44%, with an average energy-normalized removal salt of 0.65 mol kJ-1. The mechanism revealed that the desalination process involving the Prussian blue analogues primarily involves Na+ intercalation, accompanied by a small amount of electro-sorption process. This system exhibits the characteristics of conventional FCDI while enabling desalination and concentration of simulated saline water during brine discharge, thereby mitigating the impact of ion back-diffusion and broadening the application scope of FCDI.

Model-based zero liquid discharge desalination for land-locked arid/semi-arid regions in India

The arid and semiarid regions usually are water-stressed. The available natural groundwater resources in these areas are, at times, saline and unfit for potable use. Desalination of saline water is a possible solution in such cases. However, discharge of concentrated brine is an issue, particularly in land-locked areas. In this regard, a case study has been presented for brackish water desalination in Western Rajasthan, India. As this is a land-locked desert area, zero liquid discharge (ZLD) desalination has been considered, offering a practical and sustainable solution. This study presents a novel approach to the model-based ZLD hybrid desalination system consisting of reverse osmosis and multi-effect distillation (RO-MED) systems producing drinking quality water and common salt. The simultaneous production of common salt has the potential to bring down the cost of drinking water produced by the system. A system design has been carried out for a real case based on the raw water analysis of groundwater in Western Rajasthan. Our hybrid (RO-MED-ZLD) model results indicate that RO reduced TDS from 4419 mg/l to 22 mg/l with a 67 % recovery rate. The proposed ZLD method recovers 93 % of salt crystals from MED brine solutions, potentially reaching 99 % with adjustments.

Design and fabrication of porous three‐dimensional Ag-doped reduced graphene oxide (3D Ag@rGO) composite for interfacial solar desalination

Solar-driven interfacial desalination technology has shown great promise in tackling the urgent global water scarcity crisis due to its ability to localize heat and its high solar-to-thermal energy conversion efficiency. For the realization of sustainable saline water desalination, the exploration of novel photothermal materials with higher water vapor generation and photothermal conversion efficiency is indispensable. In the current study, a novel 3D interconnected monolithic Ag-doped rGO network was synthesized for efficient photothermal application. The Ultraviolet–Visible-Near Infrared (UV–Vis-NIR) and FTIR analyses demonstrated that the controlled hydrothermal reduction of GO enabled the restoration of the conjugated sp2 bonded carbon network and the subsequent electrical and thermal conductivity through a significant reduction of oxygen-containing functional groups while maintaining the hydrophilicity of the composite photothermal material. In the solar simulated interfacial desalination study conducted using 3.5 wt.% saline water, the average surface temperatures of the 3D material increased from 27.1 to 54.7 °C in an hour, achieving an average net dark-excluded evaporation rate of 1.40 kg m−2 h−1 and a photothermal conversion efficiency of ~ 97.54% under 1 sun solar irradiance. In the outdoor real-world application test carried out, the surface temperature of the 3D solar evaporator reached up to 60 °C and achieved a net water evaporation rate of 1.50 kg m−2 h−1 under actual solar irradiation. The 3D interwoven porous hierarchical evaporator displayed no salt precipitation over the 54-h period monitored, demonstrating the promising salt rejection and real-world application potential for efficient desalination of saline water.

Basil seed hydrogel incorporated activated carbon as a Capable, Bio-Based, and Cost-Effective interfacial solar steam generator

Utilization of solar energy for desalination and purification of seawater opens up a state-of-the-art way to meet the water needs all around the world specially in coastal cities. Herein, the eco-friendly, low cost and bio-based basil seed (BS) hydrogel is combined with activated carbon (AC) to synthesize activated carbon merged with basil seed hydrogel (AC-BS) composite material. Due to the photothermal property of the AC, the AC-BS composite was used to design an interfacial solar steam generator (ISSG) for water purification. The AC absorbs the sunlight and converts it to the required heat needed for water evaporation and the superhydrophilic BS hydrogel supplies water to the surface causing the high salt rejection ability of the system, in addition, it decreases the required energy for evaporation. The AC-BS is characterized using characterization methods such as EDX and FESEM. The two-dimensional (2D) AC-BS system containing a cotton fiber used to transfer water from the bulk to the surface, a layer of styrofoam as a heat insulator and AC-BS on the surface shows evaporation rate of 1.93 kg m−2h−1. The three-dimensional (3D) AC-BS, designed to solve the solar irradiation angle fluctuation problem during a day and seasons, shows an evaporation rate of 2.70 kg m−2h−1 and an efficiency of about 91 % under 1 sun illumination. The ability of the AC-BS system for saline water desalination and waste water-contaminated dyes as a pollutant treatment is highly acceptable. The AC-BS ISSG can be studied and used on large scales to provide fresh water from saline water.

Chemical grafting of hydrophobic functional groups on polyvinylidene fluoride side chain for vacuum membrane distillation applications

Membrane distillation has emerged as a promising technique for treating high-saline water. However, the process suffers from drawbacks such as wettability and fouling due to insufficient hydrophobicity of the membrane material. A practical approach for preparing hydrophobic membranes should involve improving surface roughness and chemistry manipulation. Herein, we explored chemical grafting of different functional groups viz. 1-(4-vinyl benzyl)azepane, N-(4-vinyl benzyl)decan-1-amine and 3-(triethoxysilyl)-N-(4-vinyl benzyl) propane-1-amine on polyvinylidene fluoride side chain to improve the hydrophobic characteristics and vacuum distillation performance (permeate flux and salt rejection). The successful grafting of hydrophobic functional groups on the polyvinylidene fluoride side chain was confirmed by spectral analysis such as 1H nuclear magnetic resonance, Attenuated total reflectance-Fourier transformation infrared spectroscopy, and X-ray photoelectron spectroscopy. The synthesised membranes were further characterised using morphology techniques (scanning electron microscopy, atomic force microscopy) for hydrophobicity (water contact angle, liquid entry pressure) and thermal and mechanical stability. The desalination performance of membranes was assessed by varying feed concentration (2–8 % NaCl) and feed temperature (30–75 °C). The 3-aminopropyltriethoxysilane grafted vinyl benzyl polyvinylidene fluoride membrane exhibited the highest flux (20.35 L m−2 h−1), salt rejection (99.99 %) at 4 % NaCl feed concentration and 60 °C feed temperature attributed to a well-arranged large number of pores and its hydrophobicity. The 3-aminopropyltriethoxysilane grafted membrane exhibited the highest anti-fouling characteristic. Further, high flux and salt rejection of the synthesised membranes for vacuum membrane distillation operation were compared to membranes reported in the literature, demonstrating its potential for high saline water desalination.

A Development in Solar Desalination System with Flashing of Solar Heated Water

Solar still was successfully used for the desalination of saline water in many arid and oceanic regions of the world. But the yield of solar still was found very low and fluctuating. The new develop system with the flashing of solarheated water is found possible during the study of flashing of hot water in many thermal processes used during the chemical and pharmaceutical processes. A compact and effective desalination system using solar energy had designed during the research work from the design reviews collected from flashing hot water devices used in many thermal processes. The compact flash chamber and flash steam condenser are critical components developed for the novel desalination system using locally available materials during the research work. In present experimental work a flash chamber is designed for flashing of solar heated water. Experimental work shows that by increasing the mass flow rate of water from 0.01 kg/sec to 0.02 kg/sec the distillate output of water could be increased with higher temperature of water. It shows that around 38% of higher distillate output in water could be achieved with development of new system.

Development of a unique integrated bioreactor for simultaneous desalination and bioenergy and biohydrogen production

In the wastewater treatment challenge, it is really essential to develop integrated systems in reducing greenhouse gases, producing green energy and achieving sustainable development. In this regard, an integrated electro-biomembrane reactor was developed and performed in this study for simultaneous biohydrogen (bioH2) production from energetic poplar leaves using dark fermentation (DF) process, conventional H2 production, bioenergy production in the DF process, and saline water desalination in a single system. The results of this study showed that pH was the main controlling parameter in bioH2 production, and the superior production of 40.2 mL/g-biomass was obtained at a pH of 5.5. The maximum current and power density values were 2861.7 mW/m2 and 2819.4 mA/m2 at pH 5.5 under improved conditions. Furthermore, the maximum conventional H2 production was found to be 1341.6 mL using 2 M of KOH solution. Overall, the results further proved that the proposed integrated system can be a sustainable and promising process for industrial applications, considering its high desalination, energy production, and conventional and biological H2 production efficiencies.

Advancing electrodialysis with dually cross-linked PVDF-based anion exchange membranes having semi-interpenetrating networks

Electrically-driven membrane technology plays a crucial role in water treatment and purification, finding applications in various fields like saline water and wastewater desalination, saline concentration and wastewater recycling. The content of this study is based on dually cross-linking and hot-pressing on a PVDF blend, to fabricate a kind of anion exchange membranes (AEMs) having semi-interpenetrating network and thus improve the defect of the traditional heterogeneous AEMs. The research explores the impact of vinyl imidazole (VIM) and dimethylaminoethyl methacrylate (DMAEMA) monomers, primarily or dually cross-linking, and optimizes the membrane properties through a hot-pressing process. Under these optimized conditions, the resulting membranes exhibit robust mechanical properties and outstanding desalination capabilities, achieving an area resistance of 2.56 Ω cm2 (comparable to standard homogeneous membranes), a desalination rate of 97.26% (outperforming the Neosepta AMX: 76.90%), and a salt limiting concentration of 3.1 M (surpassing the heterogeneous AEM and Neosepta AMX). Notably, this synthesis method is characterized by its cheap raw material and low energy consumption. This research offers valuable insights for the advancement and large-scale implementation of anion exchange membrane desalination.

Recent Advancement in Solar‐Driven Interfacial Steam Generation for Desalination: A State‐of‐the‐Art Review

Solar energy is one of the most efficient origins of energy for a wide range of environmentally beneficial purposes. Water desalination by steam generation with the help of solar energy is not only an economical and straightforward approach, but it also utilizes free energy sources to solve the problem of increasing freshwater scarcity. Solar water evaporation is an essential component of the low‐energy method for generating fresh water, which is required for economic development and human health. Freshwater productivity determines how effectively the system captures incoming solar energy and transforms it into usable heat. Effective water distillation has recently gained a lot of attention. The photothermal conversion process is built on the performance of the evaporator. This review thoroughly examines the most recent developments in photothermal materials, structure design, and engineering strategies, including design principles for highly efficient photothermal conversion, thermal management, water transport phenomena, salt rejection behavior, and improved evaporation rate. The prospective applications of this technique in saline water desalination, waste water purification, and energy generation are highlighted. Furthermore, the most recent scientific advancements are utilized to demonstrate the potential, prospects, and challenges of solar‐driven evaporation in energy conversion.

Enhancing capacitive deionization for water desalination: the role of activated carbon in contaminant removal

The desalination of saline water is of great importance in water-stressed areas.

Biodegradation of human faecal sludge for photosynthetic bioelectricity generation and seawater desalination in a microbial desalination cell

ABSTRACT Inaccessibility and expensiveness of vital infrastructures are the main problems in some urban and rural areas to supply fresh water, sustainable energy, and wastewater treatment. An effective solution is the integration of several systems in an environmentally friendly technology of the photosynthetic microbial desalination cell (PMDC). The aim of this study is to assess the process characterisation of an algae-based PMDC, which was loaded with a high-strength mixture of human feces and urine (HFS). The PMDC was also able to efficiently remove COD and total nitrogen of HFS by 50% and 94%, respectively. The maximum power density, voltage, and desalination efficiency of 362.5 mW/m², 175.2 mV, and 60% were accomplished. Adequate parameter adjustment led to a remarkable maximum of 2.25 g/L.d in the ion removal rate. In addition, an energy balance was governed showing that zero or positive net energy in PMDC is feasible by replacing the main energy consumers. Based on the results, this type of MDC had a high efficiency for simultaneous saline water desalination and HFS treatment, which makes it attractive for further studies of upscaling and its application in remote areas.

Tailored PVDF membrane with coordinated interfacial nano/micro-structure for enhanced membrane distillation

Membrane distillation (MD) has attracted growing attention as a sustainable green membrane process technology for seawater and high saline water desalination, yet seriously challenged by the potential membrane wetting and fouling. Herein, a controllable approach to fabricate tailor-made MD membranes was proposed via combining in-situ growth of SiO2 nanoparticles with membrane surface activation and low surface energy substances. SiO2 nanoparticles distributed uniformly on the membrane surface and combined with the intrinsic microstructure of the membrane, a hybrid macro/micro-structure was constructed, further endowing the membrane with superhydrophobicity. The modified membranes exhibited excellent wetting-resistance properties and over 99.9 % salt rejection during vacuum membrane distillation (VMD) process. The surface wetting and anti-nucleation theory special for MD membranes was uncovered. This theory and VMD experiments synchronously indicated that the hybrid macro/micro structure with optimized nanoparticle size rendered the resulting fabricated membranes enhanced permeate flux and anti-fouling properties. The optimal L-F-3 membrane achieved high flux (16.08 kg/(m2·h)) under feed temperature of 60 °C with a water contact angle of 150° and LEP (liquid entry pressure) of 2.9 bar. Finally, the modified membranes possessed the enlarged effective evaporative surface and intensified the nucleation barrier as well as the interfacial nanoscale turbulent flow without potential scaling.

Comparison of the cumulative exergy demand of phase change and reverse osmosis desalination plants with environmental impacts approach

In the scope of the current study, an investigation into the cumulative exergy demand index was conducted for freshwater production across multiple distillation technologies. These technologies encompassed Waterfall Cascading Distillation with Linear Parabolic Solar Concentrator (WCDLPC), Distillation with Linear Parabolic Concentrator and Vacuum Pump (DLPCVP), Distillation with Stand-Alone Point-Focus Parabolic Solar Concentrator (DSPPC), Reverse Osmosis with Non-renewable Energy (RONRE), and Reverse Osmosis with Solar Renewable Energy (ROSRE).The functional unit was established as the production of one ton of freshwater using various desalination technologies. The Outcomes of the analysis pertaining to the cumulative exergy demand in diverse saline water desalination technologies revealed notable findings. Specifically, in the Reverse Osmosis Desalination System with the Conventional System as well as in other desalination technologies (ROSR, WCDLP, DLPCVP and DSPPC), the electricity factor and the photovoltaic panel factor respectively exhibited the most substantial contributions to the cumulative exergy demand. Remarkably, it was observed that the RONRE technology exhibited the highest cumulative exergy demand, reaching 107.04 MJ, while the ROSRE technology demonstrated the lowest demand at 5.98 MJ. Furthermore, the integration of renewable solar energy in lieu of non-renewable electricity within the reverse osmosis technology exhibited a remarkable reduction in cumulative exergy demand, achieving a reduction of 17.90 times. Similarly, the substitution of the waterfall cascade system with a vacuum system in the WCDLPC technology resulted in a 2.69 times reduction in cumulative exergy demand.

Comprehensive energy, exergy, and economic analyses of a geothermal and flue gas-based dual-source power, hydrogen, and freshwater trigeneration system

Designing a ploy-generation system to produce various products is an effective method to improve the common power plant’s performance. Hence, the current investigation proposes a green poly-generation system driven by geothermal and flue gas. The proposed scheme consists of an organic Rankine cycle, proton exchange membrane electrolyzer, saline water desalination unit, and Allam cycle to produce power, hydrogen, and freshwater. The produced oxygen in the electrolyzer feeds the Allam cycle to perform an oxyfuel process to achieve zero CO2 emission. Per the 4E analysis, the system produces 27,720 kW net power, 931 kmol/h hydrogen, and 616.7 kmol/h freshwater. In this way, the energy and exergy efficiencies are obtained at about 16.87% and 51.65%. The total exergy destruction rate is estimated at about 78,926 kW, in which the organic Rankine cycle and its vapor generator have the highest portions among the different parts and equipment by about 69% and 18.87%. The sensitivity analysis indicates that by the CO2 recycle ratio of 60%, the highest energy and exergy efficiencies reach 19.3% and 54.33%. Furthermore, the unit cost of hydrogen and electricity productions are 0.07$/kWh and 7.24 $/GJ, which is a considerable reduction compared to similar methods.

Development of a high flux Janus PVDF membrane for oily saline water desalination by membrane distillation via PDA-TEOS-APTES surface modification

Membrane distillation (MD) is a promising approach for water desalination. However, in practice, this process is hindered by poor water flux and severe membrane fouling. In this study, a series of Janus membranes were designed for the desalination of oily saline water via direct contact membrane distillation (DCMD). Janus membranes were fabricated by a simple and facile method, direct deposition of dopamine (DA), tetraethylorthosilicate (TEOS), and aminopropyltriethoxysilane (APTES) on one side of the polyvinylidene fluoride (PVDF) membrane, which was modified by hydrophobic SiO2 nanoparticles. In brief, one side of the optimum Janus membrane was strongly hydrophobic (WCA: 149.7 ± 1°) while another side exhibited in air hydrophilicity (WA: 36.3 ± 1.2°) and underwater superoleophobicity. Additionally, the optimum Janus membrane experienced a remarkable enhancement in water flux, reaching an impressive value of 52.6 kg/m2h, (69.2 % increment compared to the pristine PVDF). Notably, the optimal Janus membrane demonstrated long-term stability and significant resistance toward oil fouling during the DCMD desalination of oily saline water while preserving its rejection and high vapor flux. The applied strategies may offer a fresh perspective on membrane design with efficient performance for MD by a facile method.