High Water Flux Research Articles

Construction of Loose Positively Charged NF Membrane by Layer-by-Layer Grafting of Polyphenol and Polyethyleneimine on the PES/Fe Substrate for Dye/Salt Separation.

The effective separation of dyes and inorganic salts is highly desirable for recycling inorganic salts and water resource in printing and dyeing wastewater treatment. In this work, tannic acid (TA) and polyethyleneimine (PEI) were grafted on the PES/Fe ultrafiltration membrane via the coordination assembly and Michael addition strategy to fabricated a loose nanofiltration membrane (LNM). The effect of PEI concentration on membrane morphologies and properties was systematically investigated. The membrane surface becomes more hydrophilic and transforms into positive charge after the PEI grafting. The optimized PES/Fe-TA-PEI membrane possesses high pure water flux (124.6 L·m−2·h−1) and excellent dye rejections (98.5%, 99.8%, 98.4%, and 86.4% for Congo red, Eriochrome black T, Alcian blue 8GX, and Bromophenol blue, respectively) under 2 bar operation pressure. Meanwhile, the LNM showed a high Alcian blue 8GX rejection (>98.4%) and low NaCl rejection (<5.3%) for the dye/salt mixed solutions separation. Moreover, the PES/Fe-TA-PEI LNM exhibited good antifouling performance and long-term performance stability. These results reveal that such LNM shows great potential for effective fractionation of dyes and salts and recycling of textile wastewater.

Design of firm-pore superhydrophobic fibrous membrane for advancing the durability of membrane distillation

Electrospun fibrous distillation membrane (EFDM), owing to its low mass transfer resistance for relatively high-water flux, has attracted significant attention to the treatment of high salinity wastewater with membrane distillation. However, a significant challenge in using EFDM for desalination of high-salinity wastewaters is pore wetting induced by scaling. Herein, we designed a firm-pore superhydrophobic fibrous membrane via a facile and scalable electrospinning in combination with dip-coating methods, which displayed a high-water flux of about 28.5 L/m2·h (ΔT = 40 °C) and unexpected durability (>312 h) in the long-term running of direct contact membrane distillation. Significantly, we also systematically investigate the effect of surface wettability and pore structure on the durability of EFDM. The experiments and simulations demonstrate that the formation of firm-pore among the EFDM has a substantial influence on the membrane durability when desalinating high salinity wastewaters, owing to the avoidance of pore deformation influenced by the feedwaters turbulent on the EFDM surface. Meanwhile, the superhydrophobic surface also helps reducing the contact area between the crystals and the salts to further improve the membrane durability. The theory simulation may provide new insight into designing novel structured fibrous membrane to improve the fibrous membrane stability in MD.

Hydrophilic PVDF membrane with versatile surface functions fabricated via cellulose molecular coating

Hydrophilic PVDF membrane was fabricated in single step via cellulose molecular coating prepared by homogeneous solution of cellulose oligomer synthesized by enzyme catalysis (EC)/Trifluoroacetic acid (TFA). Both smooth and rough coatings can be prepared by regulating the aggregative structure of cellulose molecular coatings. The chemical structures of the cellulose and its coating were confirmed by 1H Nuclear Magnetic Resonance Spectroscopy (1H NMR) and Fourier Transform Infrared Spectroscopy (FTIR). The aggregation structure of the cellulose coating was characterized by wide-angle X-ray diffraction (WAXD). X-ray Photoelectron Spectroscopy (XPS) studies unveiled the strong binding of cellulose molecular to PVDF membranes at the interface. Scanning Electron Microscopy (SEM) morphologies show that the cellulose molecules were uniformly coated on the surface and cross section of the membranes. Water contact angle measurement suggested that cellulose molecular coating possessed high hydrophilicity and wetting rate, giving the PVDF membranes high water flux and excellent anti-fouling performances. The coated membranes also show excellent adsorption and desorption performances for crystal violet (CV). The superior performances of incompletely crystallized cellulose coating over amorphous cellulose coating were attributed to the increased specific surface area resulting from the surface roughness. The construction of cellulose molecular coating with controlled aggregation structure provides a novel efficient technology in the field of purification of wastewater, opening up a new approach to the microstructural manipulation of the hydrophilic coating.

Construction of high performance thin-film nanocomposite nanofiltration membrane by incorporation of hydrophobic MOF-derived nanocages

In this study, hydrophobic nanofillers (ODA-h-NCs) were firstly synthesized through surface modification of MOF-derived nanocages by octadecylamine (ODA). ODA-h-NCs were then incorporated into poly(piperazine-amide) (PA) active layer to fabricate thin-film nanocomposite (TFN) nanofiltration membranes. The effects of ODA-h-NCs dosage on PA’s properties were characterized and the membrane performances on salt rejections were evaluated. Finally, the TFN nanofiltration membrane with the optimal nanoparticle doping amount was chosen. The experimental results show that the water permeance of the constructed TFN nanofiltration membrane reaches 8.97 L/(m2·h·bar) with 95.8% Na2SO4 rejection when ODA-h-NCs concentration is 0.0075 wt%, which is 1.7 times that of pristine membrane. It is also testified that the prepared TFN nanofiltration membrane possesses good stability through 50-h filtration test. Although the introduction of hydrophobic ODA-h-NCs increases the PA layer thickness, ODA-h-NCs decrease the crosslinking degree of PA layer by inhibiting the piperazine diffusion rate and pathway, their unique porous nanocage structure and large surface area provide additional transport path for water molecules, which equips TFN nanofiltration membrane with higher water flux.

Efficient Fenton-Like Catalysis Boosting the Antifouling Performance of the Heterostructured Membranes Fabricated via Vapor-Induced Phase Separation and In Situ Mineralization.

A photocatalytic membrane with significant degradation and antifouling performance has become an important part in wastewater treatment. However, the low catalyst loading on the polymer membrane limits its performance improvement. Herein, we fabricated poly(vinylidene fluoride) (PVDF) and poly(acrylic acid) (PAA) blend membranes with a rough surface via a vapor-induced phase separation (VIPS) process. Then Fe3+ was cross-linked with the carboxyl groups on the membrane surface and further in situ mineralized into β-FeOOH nanorods. The resultant membranes exhibit not only hydrophilicity and underwater superoleophobicity but also favorable separation efficiency and high water flux in oil-in-water emulsions separation. Under visible light irradiation, the membrane can degrade methylene blue (MB) to 95.2% in 180 min. More importantly, the membrane has a significant photocatalytic self-cleaning ability for crude oil with a flux recovery ratio (FRR) as high as 94.1%. This work brings a new strategy to fabricate the rough and porous surface for high loading of the hydrophilic photo-Fenton catalyst, improving the oil/water emulsion separation and antifouling performance of the membranes.

Symmetric forward osmosis membrane coupled with dendritic draw solute: New insights into sustainable properties

The development of current forward osmosis (FO) technology has experienced a significant challenge because of the ineliminable internal concentration polarization effect in conventional asymmetric FO membranes as well as the extremely energy-intensive recovery process of the common draw solutes (e.g., NaCl). Here, we report, for the first time, a coupling system comprising a symmetric FO (SFO) membrane and a series of macromolecular draw solutes (MDS). The lack of a support layer in the SFO membrane facilitates free MDS diffusion, thus completely eliminating the ICP effect. As a result, the obtained reverse flux selectivity (JwFO/JsFO, ratio of water flux to reverse salt flux) of the SFO/MDS system was approximately 5000, 20000, and 40000 L mol−1, which were 2–3 orders of magnitude higher than that of the conventional salt-based FO system. Moreover, due to the low rejections to inorganic salts, the SFO membrane exhibited the unique ability for allowing most NaCl to pass through while retained most MDS simultaneously, which endowed a great utility of the SFO/MDS system for desalination of textile wastewater. Subsequently, the MDS with large molecular weights could be readily recovered by a facile nanofiltration membrane process with a much higher water flux than that of the conventional reverse osmosis process at the same operating pressure, indicating the high energy-saving capacity of the SFO/MDS system. Given the significant compatibility of SFO and MDS, our study provides a new coupling strategy for the development of sustainable FO technologies.

Preparation of poly(piperazine-amide) nanofilms with micro-wrinkled surface via nanoparticle-templated interfacial polymerization: Performance and mechanism

Incorporation of nanoparticles (NPs) into the polyamide (PA) selective layer is an effective way to improve the separation performance of nanofiltration (NF) membranes. However, the mechanism of permeability enhancement and the effect on membrane properties remain unclear. Here, different NPs-incorporated NF membranes were made through several nanoparticle addition strategies and used as an alternative approach for water desalination. NPs dispersed using pressure-deposition in amine-aqueous solution before the interfacial polymerization reaction exhibited a uniform micro-wrinkled morphology with increases in effective filtration area and thus a high water flux without the sacrifice of their selectivity. The loading density, shape, and size of NPs are the most important influential factors for the distribution and pattern of micro-wrinkled structures. Three NPs representatives, including MoS2 nanosheets, UiO-66 octahedrons, and Au nanorods were used to tailor the morphology and their effect on the membrane performance was systematically investigated. The three TFN membranes under the optimal preparation conditions showed a high permeability without a sacrifice of salt rejections (Na2SO4 >95%, and MgSO4 >93%): 18.0, 16.8, and 16.0 L m-2 h-2 bar-1 for MoS2-TFN, UiO-66-TFN, and Au-TFN, respectively. Notably, all the membranes exhibited long-term structural stability. The NPs predeposition-induced micro-wrinkled method is a facile and viable strategy to enhance the performance of NF membranes, indicating their great potential in actual water desalination.

Effect of carbon nitride synthesized by different modification strategies on the performance of carbon nitride/PVDF photocatalytic composite membranes

Carbon nitride (CN)/polyvinylidene fluoride (PVDF) photocatalytic composite membrane (PCM) is considered as a promising candidate to improve the anti-fouling characteristic of conventional PVDF membrane and overcome the difficulty encountered during recovery of powder catalyst simultaneously. However, the effects of differently-modified CN on PCM and its mechanism are still unclear. In this study, bulk-CN (BCN), carbon defects CN (CCN), nitrogen defect CN (DCN), mesoporous CN (MCN), and nitrogen-rich CN (NCN) were incorporated into PVDF by phase inversion method. The influence of changes in the physical and chemical properties of CN, including hydrophilic groups, photocatalytic activity, and particle size, on the permeability, anti-fouling characteristic, and photocatalytic self-cleaning activity of CN/PVDF was systematically analyzed. The mechanism of excellent performance of PCM was revealed by experimental test and theoretical calculation. The flux of PCM was significantly improved by increasing the hydrophilic group on modified CN. However, the differences in particle size and interaction between different types of modified CN and PVDF chains endowed the CN/PVDF with different porosity. DCN/PVDF showed high porosity and hydrophilicity, leading to high water flux and rejection rate of 293.6 L (m2 h)−1 and 90.1%, respectively. Compared to pure PVDF, the flux recovery rate of DCN30/PVDF increased by 27.6%, and the irreversible fouling decreased from 36.9% to 9.2%. The modified CN/PVDF showed excellent photocatalytic activity for the removal of cefotaxime (CFX) and E. coli. Owing to the narrow band gap of DCN, large specific surface area, and low photogenerated carrier recombination rate, the CFX removal rate reached 99% in 2 h, and E. coli inactivation achieved 3.7 log within 4 h via DCN30/PVDF.

High-performance nanofiltration of outer-selective thin-film composite hollow-fiber membranes via continuous interfacial polymerization

Outer-selective thin film composite (TFC) hollow fiber membranes have the advantages of fiber blockage with less pressure drop and high surface area module. This work highlights novel strategies to design continuous interfacial polymerization that can allow mass production, performance controllability, and small margin of error in performance. Processing parameters were symmetrically optimized to maximize high water flux and salt rejection using poly(piperazine-amide) TFC membranes. For further improving the membrane performance, polyvinyl alcohol was incorporated for an interlayer, thereby having the water flux of 48 LMH/bar and the salt rejection (Na2SO4) of 99.6%. The system can be used in a variety of applications such as reverse osmosis, forward osmosis, or gas separations by simply replacing the monomers.

Enhanced water permeability and fouling resistance properties of ultrafiltration membranes incorporated with hydroxyapatite decorated orange-peel-derived activated carbon nanocomposites

Hydroxyapatite-decorated activated carbon (HAp/AC) nanocomposite was synthesized and utilized as a nanofiller to fabricate a novel type of polyethersulfone (PES) nanocomposite ultrafiltration (UF) membranes. Activated carbon (AC) derived from orange peel was synthesized by low-temperature pyrolysis at 400 °C. A hydroxyapatite/AC (HAp/AC) nanocomposite was developed by a simple one-pot hydrothermal synthesis method. The UF membrane was fabricated by intercalating HAp/AC fillers into PES casting solution by the non-solvent induced phase separation (NIPS) process. The prepared membranes exhibited a lower water contact angle than the pristine PES membrane. The hybrid membrane with 4 wt% HAp/AC nanocomposite displayed 4.6 times higher pure water flux (~660 L/m2 h) than that of the pristine membrane (143 L/m2 h). In static adsorption experiments, it was found that the amount of humic acid (HA) and bovine serum albumin (BSA) adsorbed by the HAp/AC-PES hybrid membrane was much lower than that of the original membrane due to the electrostatic repulsive forces between them and the surface of the membrane. Irreversible fouling was reduced from 33 to 6 % for HA and from 46 to 8 % for BSA after HAp/AC was incorporated into the PES matrix. After 7 cycles of water-BSA-water, the HAp/AC-PES hybrid membrane maintained a high pure water flux of 540 L/m2 h with an excellent flux recovery ratio (FRR), demonstrating the long-term stability of the membranes. The developed UF membranes outperformed the original PES membranes in terms of permeability, selectivity, and antifouling.

Fabrication of high-performance composite membranes based on hierarchically structured electrospun nanofiber substrates for pervaporation desalination

Electrospun polyacrylonitrile (PAN) nanofiber membrane was fabricated. The surface of the PAN nanofiber membrane was spray-coated with a hydrophobic paint or knife-casted with an ultra-fine nanofiber cellulose (NC) layer. This was to mitigate the problem of infiltration of the coating solution into the pores of the virgin PAN nanofiber membrane when preparing composite membranes. As a result, defect-free and thin PVA layers were successfully deposited onto the hydrophobic PAN nanofiber or NC-PAN nanofiber substrates by a spray-coating method. The thin film composite (TFC) PVA/NC-PAN membrane exhibited extradentary pervaporation desalination properties. A water flux of 238.7 ± 4.1 kg/m2·h and a salt rejection above 99.8% were obtained using a 3.5 wt% NaCl solution as feed at 80 °C. This is the highest reported water flux of all the PV desalination membranes. Moreover, a high-water flux of 103.1 ± 5.8 kg/m2·h was observed using the composite membrane to desalinate a 20 wt% NaCl solution at 70 °C. The excellent desalination property of the PV composite membrane demonstrates a great potential for recycling brine solutions.

Surface engineering through biomimicked structures and deprotonation of poly(vinyl alcohol) membranes for pervaporation desalination

Membrane pervaporation provides an effective approach for production of desalinated water and treatments of salted water. The water permeation fluxes through the membranes could be the key issue for practical systems. In this work, a surface engineering through introduction of lotus-leaf biomimicked structures and chemical deprotonation has been performed on poly(vinyl alcohol) membrane surfaces. The increased surface area and hydrophilicity of the membranes significantly enhance water dissolution into the membrane, so as to bring a 2.8 times of water permeation flux to the membrane. In addition to a high thickness-normalized water flux of 386 kg-μm h−1 m−2, the surface-engineered PVA membrane also exhibit ability for desalination on high salinity water (15 wt% NaCl(aq)). The surface-engineering method could be integrated with other approaches for membrane modification to exhibit synergistic effect on enhancements of membrane separation performance.

Evaluating Fertilizer-Drawn Forward Osmosis Performance in Treating Anaerobic Palm Oil Mill Effluent.

Fertilizer-drawn forward osmosis (FDFO) is a potential alternative to recover and reuse water and nutrients from agricultural wastewater, such as palm oil mill effluent that consists of 95% water and is rich in nutrients. This study investigated the potential of commercial fertilizers as draw solution (DS) in FDFO to treat anaerobic palm oil mill effluent (An-POME). The process parameters affecting FO were studied and optimized, which were then applied to fertilizer selection based on FO performance and fouling propensity. Six commonly used fertilizers were screened and assessed in terms of pure water flux (Jw) and reverse salt flux (JS). Ammonium sulfate ((NH4)2SO4), mono-ammonium phosphate (MAP), and potassium chloride (KCl) were further evaluated with An-POME. MAP showed the best performance against An-POME, with a high average water flux, low flux decline, the highest performance ratio (PR), and highest water recovery of 5.9% for a 4-h operation. In a 24-h fouling run, the average flux decline and water recovered were 84% and 15%, respectively. Both hydraulic flushing and osmotic backwashing cleaning were able to effectively restore the water flux. The results demonstrated that FDFO using commercial fertilizers has the potential for the treatment of An-POME for water recovery. Nevertheless, further investigation is needed to address challenges such as JS and the dilution factor of DS for direct use of fertigation.

Influence of physicochemical characteristics of feed solution on water permeability in forward osmosis desalination system

Many chemical species are involved in the feed solution (FS) in a forward osmosis (FO) process used for water/wastewater treatment and desalination. Chemicals and their molecular interactions in FS could have variable influences on water transfer and permeability, and consequently the overall performance of the FO process. This fundamental is important for understanding molecular transfer mechanisms in FO system, but has received a little attention. This preliminary study associated with its systematic investigations aimed to discover the impacts of physical and chemical properties (chemical composition, diffusivity, molar mass and charges) of FS on the water transfer characteristics and permeability in a FO desalination system. We evaluated the water flux in FS containing different salts in natural water and seawater. Our results revealed that water permeability can be significantly affected by the chemical constituents and molecular weights of FS. Water flux profiles follow an order of cations in FS: Na+ > K+ > Mg2+ > Ca2+, while high water flux reduction was found in K+ and NO3− FS. Solute diffusivity in FS was evidenced to play a crucial role in the water permeability. High water flux was determined in the FS with K+ and NO3− as which have the high diffusion coefficient. Experimental data showed that water flux could be affected by ionic mass and charge of solutes in FS as analysed by ratio of charge to molar mass (Z/M). Water flux reduction follows an increase of Z/M. This preliminary study raises insight to getting better understanding of molecular interactions in the chemically complex FS and their impact on the water transfer mechanisms in FO system.

Techno-economic comparison between forward osmosis (FO) and temperature-enhanced osmotic membrane distillation (T-OMD) in agricultural fertigation

Forward osmosis (FO), as one energy-efficient desalination technology, had been intensively studied in agricultural fertilization to meet the demand of the water resource and the fertilizer for plant growth, showing good techno-economic benefit. As such, the energy-efficient temperature-enhanced osmotic membrane distillation (T-OMD) heated by low-grade thermal sources (i.e. solar energy) was firstly investigated in agricultural fertilization via techno-economic comparison with FO. The experimental investigation revealed that T-OMD in the agricultural fertigation can be endowed with quadruple advantages of high water flux at a high-temperature difference (>40 °C), low fertilizer loss, good compatibility for different fertilizers, and good feasibility to utilize some unconventional waters (i.e. wastewater, seawater, and seawater RO brine). Furthermore, a preliminary economic analysis showed that the membrane area and the price of the FO membrane module are two significant indicators to evaluate the economic feasibility of T-OMD. In detail, T-OMD must be more cost-effective than FO if the total membrane area is larger than 10,000 m2 under the same operating temperature configuration or dilution factor lower than 0.25 and permeate flux higher than 10,000 m3/h are satisfied under different operating temperature configurations. Based on the experimental investigation and economic analysis, T-OMD can provide an alternative pathway to achieve high-efficient and cost-effective agricultural fertigation.

Degradation of antibiotics, organic matters and ammonia during secondary wastewater treatment using boron-doped diamond electro-oxidation combined with ceramic ultrafiltration

In this study, a BDD electrolytic oxidation-ceramic membrane ultrafiltration (EO-CM) system for the removals of antibiotics, organic matters and ammonia in wastewater was evaluated. Sulfamethazine (SMZ) was degraded following a pseudo first-order kinetics. The removal rate of SMZ improved with the increase of electro-oxidation time (0–60 min) and current density (5–30 mA/cm2). During the BDD electro-oxidation process, H2O2 and hydroxyl radicals (•OH) were generated which were detected by N, N-diethyl-p-phenylenediamine (DPD) method and electron paramagnetic resonance spectroscopy (EPR), respectively. Chemical oxygen demand (COD) was able to be removed by EO and CM processes, in which proteins and humic acids were regarded as the main removed components measured using excitation-emission matrix (EEM) technique. Moreover, BDD electro-oxidation pretreatment could make the CM process maintain a high water flux and significantly control the membrane fouling and relieve transmembrane pollution. In addition, the removal of ammonia was enhanced with the increase of chloride ions (Cl−) in wastewater during EO process due to the generation of active chlorine (i.e., ClO−, HClO, or Cl2) from the oxidation of Cl−. Chloramine and nitrogen were produced in the oxidation of ammonia by active chlorine. Overall, the results of this study suggest that BDD EO-CM system is a promising process for removing antibiotics, organic matters and ammonia.

Effects of temperature, pH, feed, and fertilizer draw solution concentrations on the performance of forward osmosis process for textile wastewater treatment.

Water is crucial for enhancing the yield of agricultural land to meet the growing demand. Forward osmosis (FO) is a developing technology that utilizes the natural osmotic gradient of solutions. In this study, fertilizer drawn FO setup was considered by using potassium chloride (KCl) as the draw solution (DS) for treating textile wastewater as the feed solution (FS). This study investigated the effects of FS temperature, pH, and FS and DS concentrations. The performance investigation involved the study in terms of water flux, reverse salt flux, and specific reverse salt flux. DS and FS properties, osmotic potential, and temperature played a vital role in the performance. At 30°C FS temperature, the highest water flux (5.5 LMH) was observed. Reverse salt flux increased due to the increase in solute diffusivity. The highest value of water flux was obtained at a DS of 1.150 M and FS of 1000 mg/L. The permeation of water improved due to the difference in DS and FS concentrations at pH values above 7. The results of this study suggest that KCl as DS has a higher potential for the treatment of textile wastewater at a temperature of 30°C. Additionally, the functional groups attached to the FO membrane were identified through Fourier-transform infrared (FTIR) spectroscopic study. PRACTITIONER POINTS: Treatment of textile wastewater with the use of fertilizer draw solution (KCl) by forward osmosis process as carried out. The performance was assessed in terms of water flux, reverse salt flux, and specific reverse salt flux. The effects of feed and fertilizer draw solution concentrations; pH and temperature were evaluated on the performance of FO process.

Comparison of blue and green water fluxes for different land use classes in a semi-arid cultivated catchment using remote sensing

Study areaKikuletwa catchment, Upper Pangani River Basin, Tanzania. Study focusThis study compared yearly blue and green water fluxes using four different methods: Senay’s method (SN) (Senay et al., 2016), van Eekelen method (EK) (van Eekelen et al., 2015), the Budyko method (Simons et al., 2020) and the Soil Water Balance (SWB) model (FAO and IHE Delft, 2019). The yearly blue and green water fluxes of different Land Use Land Cover (LULC) classes were estimated using an ensemble of seven global remote sensing-based evapotranspiration products (Ensemble ET) and the CHIRPS rainfall dataset. The Ensemble ET was created from seven global RS-based surface energy balance models (GLEAM, CMRS-ET, SSEBop, ALEXI, SEBS, ETMonitor and MOD16). New hydrological insightsOur study found that the EK method was able to map blue and green water fluxes with realistic results for irrigated and non-irrigation cultivated areas. Budyko and SWB gave too high blue water fluxes for the non-irrigated agricultural areas, whereas the Budyko and SWB models were not able to show a clear difference in blue-water fluxes in irrigated versus non-irrigated areas. On the other hand, the SN method estimated no blue water fluxes in more than half of the identified irrigated areas.Three of the four methods estimate the highest blue water fluxes (318–582 mm/y) in forested areas, while the SWB model estimates the highest blue water fluxes in irrigated banana and coffee (278 mm/y). Overall, we conclude that the EK method yielded the most realistic spatial pattern of blue-water fluxes when compared to the irrigated land use map, whereas SWB could be considered after further calibration if higher temporal data resolution (e.g. monthly) is required.

Efficient water desalination with graphene nanopores obtained using artificial intelligence

Two-dimensional nanomaterials, such as graphene, have been extensively studied because of their outstanding physical properties. Structure and topology of nanopores on such materials can be important for their performances in real-world engineering applications, like water desalination. However, discovering the most efficient nanopores often involves a very large number of experiments or simulations that are expensive and time-consuming. In this work, we propose a data-driven artificial intelligence (AI) framework for discovering the most efficient graphene nanopore for water desalination. Via a combination of deep reinforcement learning (DRL) and convolutional neural network (CNN), we are able to rapidly create and screen thousands of graphene nanopores and select the most energy-efficient ones. Molecular dynamics (MD) simulations on promising AI-created graphene nanopores show that they have higher water flux while maintaining rival ion rejection rate compared to the normal circular nanopores. Irregular shape with rough edges geometry of AI-created pores is found to be the key factor for their high water desalination performance. Ultimately, this study shows that AI can be a powerful tool for nanomaterial design and screening.

Superhydrophilic polyvinyl alcohol-formaldehyde composite sponges with hierachical pore structure for oil/water emulsion separation

Regarding emulsion separation using porous materials, two keypoints, i.e. proper average pore size and wettability, should be carefully considered. Herein, three-dimensional (3D) superhydrophilic polyvinyl alcohol-formaldehyde (PVA-PVF) sponges with tunable pore size are successfully prepared through crosslinking reaction of polyvinyl alcohol (PVA) in the polyvinyl alcohol-formaldehyde (PVF) network under acidic condition. The introduction of PVA containing chitosan, diatomite and sodium alginate can effectively decrease the average pore size of PVF from approximately 75 μm to 23 μm along with a few hundred nanometers pore channels, while maintaining porosity above 73.4%. These PVA-PVF composite sponges with hierachical pore structure are applied to separate various surfactant­stabilized oil-in-water emulsions solely by gravity. The separation efficiency can reach up to 97.40% with a high water flux of 2.40 × 104 L m−2 h−1 bar−1. Meanwhile, the separation efficiency of different charged PVA-PVF composite sponges (i.e. PVA-CS-PVF, PVA-Si-PVF, PVA-SA-PVF) for oil-in-water emulsions stabilized by different types of surfactants, including anionic, nonionic, and cationic surfactants, is also evaluated. Definitely, the PVA-PVF composite sponges with outstanding hydrophilic, excellent stability, simple preparation method can be regarded as a new candidate of emulsion separation material in practical applications.