Enhanced Water Flux Research Articles

Optimization of ultrathin polyamide nanofiltration membranes with sulfonated polyethersulfone interlayers for enhanced performance

The “trade-off” effect of nanofiltration membranes may lead to problems of lower flux and higher energy cost, which limit their applications. In this work, an ultra-thin polyamide selective layer (34 nm in thickness, much lower than the conventional polyamide selective layer) was prepared by constructing a sulfonated polyethersulfone interlayer on the surface of polysulfone ultrafiltration membranes by liquid-phase deposition, taking advantage of the inhibitory effect of sulfonated polyethersulfone nanoparticles on the diffusion of piperazine. The prepared nanofiltration membrane exhibits a water flux per unit pressure of 33.2 L·m−2·h−1·bar−1, which is more than 2.5 times higher than that of the nanofiltration membrane without the introduction of the interlayer (12.2 L·m−2·h−1·bar−1). Additionally, it has a high rejection of 98.8 % for Na2SO4, which surpasses the upper limit of the equilibrium of trade-off. The study also delves into the modulation mechanism of the interfacial polymerization process by the presence of a sulfonated polyethersulfone interlayer and explores the potential reasons for the water flux enhancement. This research will likely provide theoretical support and practical experience for further optimization of nanofiltration membrane performance.

Experimental investigation and comparison of PBI/MWCNT and PSF/MWCNT membranes for recovering water from RO reject of brackish water by FO

The performances of polybenzimidazole (PBI) and polysulfone (PSF) membranes for recovering water from reverse osmosis (RO) reject of brackish water through forward osmosis (FO) were assessed and compared. Non-functionalised multi-walled carbon nanotubes (MWCNT) were added to the membrane casting solutions, with concentrations ranging from 0 to 3 wt%. The experiment was conducted for eight samples using RO reject of brackish water as the feed solution (FS) and 2 M analytical grade MgCl2 as the draw solution (DS). The hydrophilicity, water permeability, salt rejection rate (Rs), water flux (WF) and porosity of the membranes improved with increasing MWCNT content up to 2 wt%. Also, the structural parameter, salt permeability and reverse solute flux decreased. PBI/MWCNT2 wt% exhibited the best performance among the membranes tested compared with porosity of 70 ± 4 %, structural parameter of 0.36 ± 0.2 μm, and Rs of 93.5 %. In contrast with the pristine PBI membrane, an average water flux enhancement of 15 % and 49 % was observed for the FS and DS sides, respectively, for PBI/MWCNT2 wt%. It is evident from the results that including MWCNT improves the performance of both membranes, with better relative performance for PBI membranes than PSF membranes.

Carbon dots regulating microstructure of polyamide layer of forward osmosis membrane for anti-biofouling and unexpected dual-enhancement in water flux and salt rejection

The introduction of hydrophilic nanomaterials into the polyamide (PA) layer of forward osmosis (FO) membranes usually leads to the enhancement in water flux but a reduction in salt rejection. The decrease in salt rejection, however, inevitably influences the osmotic efficiency and operation cost. In this work, m-phenylenediamine (MPD), one of the chemicals of interfacial polymerization, was utilized as a precursor to synthesize carbon dots (MPD-C-dots) with a good photosensitization functionality. The MPD-C-dots were introduced into the PA layer of FO membranes through co-interfacial polymerization (denoted as Single-C-dots-M), and further grafted onto the PA layer by the conjugation of the residual acyl chloride of trimesoyl chloride with the amine of MPD-C-dots (denoted as Double-C-dots-M). The as-prepared Double-C-dots-M exhibited more outstanding FO performances than the pristine membrane (Control-M) and Single-C-dots-M. Most unexpectedly, the dual-enhancement in water flux and salt rejection of Double-C-dots-M was found. The further studies reveal that Double-C-dots-M had smaller and more uniform pore size, but larger porosity than the other two. In addition, the biofouling-resistance tests demonstrate that MPD-C-dots-M had an excellent anti-biofouling performance by generating singlet oxygen (1O2) under light irradiation. The proposed Double-C-dots-M provided a typical protocol for improving the performances of FO membrane, especially for the synchronous enhancement in water flux and salt rejection.

Hydrogel/mineral-integrated interface for synergistic antifouling membrane

Antifouling performance is significant for practical membrane separation, determining the membrane permselectivity, lifespan and maintenance cost. Integrating multi-component antifouling materials at the membrane interface is a promising solution for maximizing the membrane antifouling potential. Herein, a gel-mineral hybrid interface was constructed on polyvinylidene fluoride (PVDF) membrane via MnO2 mineralization induced by the tannic acid (TA)/polyvinylpyrrolidone (PVP) intermediate hydrogel layer. The resultant membrane exhibited superhydrophilicity and resulted in excellent enhancement in permeability and antifouling performance. The modified ultrafiltration membrane exhibited enhanced water flux, rejection of pollutants, and flux recovery rate (FRR) for organic solutions. The pure water flux of the optimal membrane is 40 % higher than that of PVDF. Most importantly, this hydrogel/mineral hybrid interface collectively resists the adhesion of pollutants and catalytic cleaning to remove pollutants. This integrated interface tailoring strategy paves a way for multi-scale antifouling separation membranes.

Synthesis and Characterization of Anti‐fouling Ultrafiltration Nanocomposite Membranes Integrated with S‐β Zeolite Nanoparticles for Oily Wastewater Treatment

AbstractMembrane separation has been proven to be highly effective in oily wastewater treatment, although fouling remains a persistent challenge. This study explored the incorporation of S‐β zeolite nanoparticles into an ultrafiltration membrane, forming a nanocomposite to tackle fouling and enhance water flux recovery. Porous nanoparticles were synthesized using sol‐gel and hydrothermal methods, featuring a remarkable surface area of 450 m2/g and pore sizes ranging from 50 to 175 nm according to BET results. These nanoparticles were integrated into the membranes at various concentrations using the phase inversion technique. The presence of S‐zeolite in the membrane was confirmed through FTIR, EDX, and SEM analyses. The S‐β1 nanocomposite membrane demonstrated exceptional antifouling properties, particularly at higher concentrations of oily wastewater. Its outstanding performance is attributed to its enhanced hydrophilicity and average pore size of 13±3 nm, which prevents fouling formation. Compared to other membranes, S‐β1 exhibited remarkable water flux recovery, reaching 100 % at an oil concentration of 50 ppm and 72 % at 1000 ppm. These results highlight the significant advantages of this nanocomposite in reducing fouling and improving the water flux recovery in oily wastewater treatment.

Synthesis and characterization of an innovative sodium alginate/flaxseed gum green hydrogel for forward osmosis desalination

Recently, fresh water resources have been limited globally. Thus, desalination has been the most recommended solution to overcome this issue. Forward osmosis (FO) is an affordable and developing desalination technique. In this current study, a cutting-edge green hydrogel was prepared from a polymer blend of flaxseed gum (FG) and sodium alginate using epichlorohydrin (ECH) as a crosslinker and polyethylene glycol (PEG) as a semi-interpenetrating network polymer. The impact of PEG incorporation on the hydrogel’s response was investigated, and the influence of different mass contents of FG and ECH on the swelling measurements of the hydrogel was studied to optimize the composition of the hydrogel. The optimum hydrogel was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction and the compressive strength test. Furthermore, the behavior of the present hydrogel was examined as a draw agent in a batch FO unit. The water flux and the reverse solute flux were measured at various values of average hydrogel particle size and feed solution (FS) temperature and concentration. The optimal hydrogel of 0.3 PEG/polymer blend mass ratio, 12% FG, and 0.95 ECH/polymer blend mass ratio exhibits a swelling ratio (%) of 1800 after an hour and an equilibrium swelling ratio (ESR) (%) of 5300. The results of the FO experiments revealed that raising FS temperature and reducing FS concentration and average hydrogel particle size enhance water flux.

Solar-driven surface-heating membrane distillation using Ti3C2Tx MXene-coated spacers

The emergence of two-dimensional (2D) MXenes as efficient light-to-heat conversion materials offers significant potential for solar-based desalination, particularly in photothermal interfacial evaporation, enabling cost-effective solar-powered membrane distillation (MD). This study investigates solar-powered MD afforded by a photothermally functionalized spacer, which is built by spray-coating Ti3C2Tx MXene sheets on metallic spacers. 2D Ti3C2Tx MXene gives an ultrahigh photothermal conversion efficiency; thereby, by Ti3C2Tx MXene-coated metallic spacer, this rationally designed spacer allows for a localized photothermal conversion and interfacial feed heating effect on the membrane surface, especially for MD operation. As a feed spacer and a photothermal element, Ti3C2Tx MXene-coated metallic spacer exhibited stable enhanced water flux of up to 0.36 kg·m−2h−1 under one sun illumination for a feed salinity of 35 g·L−1, corresponding energy conversion efficiency of 28.3 %. Overall, the developed photothermal Ti3C2Tx MXene-coated spacers displayed great potential in enhancing the performance, scalability, and feasibility of solar-driven MD process, paving the way for further development of photothermal elements that can be implemented in solar MD applications.

Beads-on-string structural nanofiber membrane with ultrahigh flux for membrane distillation

Membrane distillation (MD) is a promising technology among various desalination processes. However, the membrane used in MD is still problematic due to its low permeability and tendency to become wet. In this work, we fabricated a novel electrospun nanofiber membrane (ENM) with micro-nano structures resembling beads on a string to enhance water flux and anti-wetting properties in MD desalination. The composite ENM consists of a heat-conducting top layer made of polyvinylidene fluoride co-hexafluoropropylene (PH) nanofibers embedded with carbon sphere (CS) nanoparticles and a heat-insulating support layer made of pH nanofibers. The PH/CS top layer with beads-on-string micro-nano structures can not only provide a rough surface to elevate anti-wetting property of the membrane, but also create a maximum temperature difference inside the membrane to improve mass transfer of water vapor. The PH/CS composite ENMs acquired the highest water flux of ∼ 71.3 L m−2 h−1 at a temperature difference of 40 °C, and its salt rejection rate for a 3.5 wt% NaCl solution was higher than 99.9% in direct contact membrane distillation. Meanwhile, the composite ENM exhibited long-term stability of 5100 min. Our work presents a novel composite ENM with great potential for promoting water flux and anti-wetting properties towards MD desalination.

Modification of PAN electrospun nanofiber membranes with g-C3N4 nanotubes/carbon dots to enhance MBR performance

This study is dedicated to the enhancement of electrospun polyacrylonitrile (PAN) nanofiber membranes for their application in membrane bioreactor (MBR) processes. The improvement is achieved through the incorporation of graphitic carbon nitride nanotubes/carbon dots (g-C3N4 NT/CDs) and subsequent heat post-treatments at varying temperatures. Notably, the hot-pressing methodology effectively mitigates surface roughness and significantly reduces issues related to peeling during nanofiber experimentation. Our results demonstrate that the introduction of 0.5 wt% of g-C3N4 NT/CDs leads to a substantial enhancement in water flux. In particular, nanocomposite membranes subjected to hot-pressing at 90 °C for 10 min exhibited an impressive flux recovery ratio (FRR) of 70%. Furthermore, the heat-treated nanocomposite membranes exhibited remarkable antifouling properties and significantly reduced fouling rates when compared to their heat-treated bare counterparts. This study underscores the noteworthy potential of g-C3N4 NT/CDs-modified PAN nanofiber membranes to substantially elevate MBR performance, firmly positioning them as highly promising candidates for critical applications in the domains of water and wastewater treatment. However, it is imperative to underscore that the existing written material necessitates a comprehensive overhaul to align with the provided structural framework.

In‐situ generated ZnO nanoparticles for enhanced performance of thin film nanocomposite membrane in forward osmosis process

AbstractThis work developed a novel approach to the in‐situ synthesis of ZnO nanoparticles to modify the polysulfone (PSf) porous membrane substrate. The zinc acetate was added to the casting solution, and ZnO nanoparticles were synthesized during phase inversion. The non‐solvent pH and zinc acetate concentration controlled the ZnO synthesis and loading. Their effect on the substrates properties in terms of morphology, hydrophilicity and porosity was studied thoroughly. The result shows that the ZnO nanoparticles was not formed in acidic pH, while ZnO nanoparticles with size of 20 nm could be easily formed in basic pH. The successful synthesis of ZnO nanoparticles was investigated using FTIR and EDX analysis. The EDX images verify that in‐situ synthesis led to a more uniform dispersion than conventional incorporation method. Then the effect of ZnO loading on the interfacial reaction and polyamide (PA) structure was investigated. SEM images verify the successful synthesis of a uniform and defect‐free PA thin film on ZnO modified substrates. FO performance results show an enhancement in water flux and salt rejection as a result of ZnO incorporation in thin film nanocomposite (TFN) membranes, where TFN 1 wt.% in‐situ membrane showed 40% higher water flux than the control TFC membrane. The porous and hydrophile substrate in TFN 1 wt.% in‐situ membrane is responsible for improved separation performance. These modified membranes displayed uniform dispersion of ZnO nanoparticles within substrates, confirming that this method could effectively restrain the aggregation of the nanoparticles.

MOFs and surface modification synergistically modulated cellulose membranes for enhanced water permeability and efficient tellurium separation in wastewater

With the widespread use of tellurium-containing products such as cadmium telluride solar cells in daily life, tellurium-containing wastewater inevitably enters the environmental water system. Removal of the ionic contaminant tellurite is essential in wastewater reclamation due to its potential threat to human health and difficulty of elimination. Herein, a rational design of separation membranes with synergistic physical and chemical effects to enhance separation efficiency with almost complete compensation for the loss of water flux was proposed. Membranes for tellurium separation with high efficiency and enhanced water flux were prepared by surface modification on the MOF-based support layer forming a dense separation layer (TSNTCM). The membrane separation efficiency was enhanced by the introduction of NH2-MIL-125 in the support layer, while the water flux was improved by its nano water channels. The abundant hydroxyl and anionic groups in the structure of the polymer monomer sodium lignosulfonate not only endowed the separation layer with chemical interaction (hydroxyl substitution), but also made the membrane surface highly negatively charged and improved the physical interaction. TSNTCM showed excellent tellurium separation efficiency (>95%) over a wide concentration range and achieved the highest rejection (99.16%) at pH = 6. Besides, the rejection of tellurium by TSNTCM was above 90% in the presence of common coexisting ions, but decreased in the presence of selenite, which may be due to the similar structure and properties of selenite and tellurite. Moreover, TSNTCM demonstrated satisfactory reusability and anti-fouling properties. Overall, MOFs and surface modification enhanced the comprehensive performance of TSNTCM, providing great potential for its application in wastewater reclamation.

A novel and facile preparation of superhydrophilic/superoleophobic Mg(OH)2/ZnO coated mesh for fast and efficient oil/water separation

This study presents a new method for the rapid preparation of a superhydrophilic/underwater superoleophobic Mg(OH)2/ZnO coated mesh. Through one-step electrodeposition, a high underwater oil contact angle of 168.54° was achieved on the coated mesh. The electrodeposition process involved the deposition of ZnO nanoparticles on the cathode due to the presence of Mg2+ in the electroplating solution, while Mg(OH)2 was simultaneously formed on the surface of the cathode copper mesh. The cathode surface, where hydrogen is generated, leads to the formation of micropores and nanosheets on the Mg(OH)2/ZnO coated mesh structure. This structural feature traps more water molecules, further enhancing the superhydrophilicity of the coated mesh. The oil/water separation efficiencies for p-xylene, kerosene, paraffin liquid, and mineral oil were 99.8 %, 99.3 %, 99.5 %, and 99.4 %, respectively. The separation efficiency remained higher than 99.2 % even after conducting 350 p-xylene/water separation experiments. Additionally, the coated mesh displayed a strong oil/water separation ability after being immersed in alkali and salt solutions (pH = 7, 9) for 10 h. The coated mesh exhibited an enhanced water flux of (2.99 ± 0.20) × 105 L·m−2·h−1, along with a heightened invasion pressure (>2.8 kPa) and excellent oil-resistance performance. Overall, the Mg(OH)2/ZnO coated mesh developed in this study shows promising potential as a membrane for fast and efficient oil/water separation, with outstanding durability.

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.

New insights into the role of carbon nanotubes spray-coated on both sides of the PTFE membrane in suppressing temperature polarization and enhancing water flux in direct contact membrane distillation

Wetting and temperature polarization (TP) are two critical issues that are closely associated with the lifespan and production efficiency in membrane distillation (MD). An ideal MD membrane should be wetting resistant with low TP. Although great achievements were made to date in MD design, maintaining wetting resistance and low TP is still challenging. This study developed a facile and effective strategy to construct a high-performance hierarchical MD membrane by spraying carbon nanotubes (CNTs) on both sides of a pristine PTFE membrane (PTFE-dCNTs membrane, d stands for double layers). Spray coating the pristine PTFE membrane by less than 800 nm thick CNTs double-layers enhanced the water flux by 1.6 fold (52.3 LMH) and increased the wetting resistance time by 2.2-fold (51.1 h) with a temperature difference of 40 °C (feed of 60 °C and permeate of 20 °C). With optimized CNTs coating density, the PTFE-dCNT (2) membrane displays a water flux as high as 126 L m−2 h−1 with a salt rejection rate of 99.9% under the temperature difference of 60 °C in direct contact MD, surpassing most of the reported MD membranes. Experimental and simulation results demonstrate that a unique sandwich structure of MD membrane having thermal conductive and wetting resistant layers on both sides of membranes is beneficial to enhance the water flux and operation stability by suppressing temperature polarization and membrane wetting on both sides in direct contact MD. The strategy proposed here can be extended to a wide range of materials, holding a great potential to fabricate high-efficiency MD membranes.

Polyamide nanofiltration membrane fabricated via a metal-chelate strategy for high-flux desalination

Nanofiltration (NF) technology, utilizing polyamide (PA) membranes fabricated through interfacial polymerization (IP), has found extensive application in desalination processes. The pursuit of enhancing water permeance while maintaining high rejection rates of NF membranes has garnered substantial research attention. This study proposed a metal-chelate strategy by incorporating calcium chloride (CaCl2) as an aqueous additive during the IP process and employing EDTA-4Na for post-treatment. In the presence of Ca2+, the EDTA-4Na-soaked membrane achieved suitable swelling to better regulate membrane pores, which benefited water flux enhancement and avoided severe structural defects. Meanwhile, the modified membrane also showed a more hydrophilic and negatively charged surface, leading to a significant performance in removing Na2SO4. As a result, the optimized membrane exhibited a water flux of 24.6 L m−2 h−1 bar−1, nearly 3 folds that of the initial PA membrane, while maintaining a satisfactory Na2SO4 rejection (97.2 %). Moreover, the obtained membrane showed good operation stability and anti-fouling properties during long-term use. This work proves that the metal-chelate strategy can be an efficient modification method and inspires the fabrication of high-performance NF membranes with coupling processing.

Highly efficient deep eutectic solvents coated MIL-53(Fe) embedded polyvinylidenefluoride MMMs for phenol separation using pervaporation

Novel hydrophilic pervaporative mixed matrix membranes (MMMs), comprising deep eutectic solvent-coated MIL-53(Fe) embedded polyvinylidenefluoride (PVDF) matrix, are prepared to remove phenol from the water. Double cone hexagonal prism type MIL-53(Fe) nanofillers are first synthesized by hydrothermal method and then encapsulated with deep eutectic solvent (DES) solution by a deep coating process. The DES-coated MIL-53(Fe) nanofillers are added to the PVDF matrix to prepare the MMMs using the non-solvent-induced phase-separation (NIPS) process. The prepared DES@MIL-53(Fe) and MMMs are characterized by various analytic techniques to verify the successful addition of the nanofillers into the PVDF matrix. The highest pure water flux (PWF) values of nearly 126 L m−2h−1 are observed with a DES@MIL-53(Fe) loading of 7.5 wt% in the polymer dope solution for MMMs, which is three times higher than pure PVDF membrane values (41.5 L m−2h−1). The DES@MIL-53(Fe)/PVDF MMMs showed nearly 215% enhancement in pure water flux (131.66 L m−2h−1) and ∼ 107% enhancement in the phenol removal efficiency (93.22%) for the 50-ppm phenol solution as compared to pure PVDF membranes. Further, the experiments are carried out within a wide range of feed concentrations (feed concentration: 15–90 ppm) and feed pH (pH: 1–13) to study the separation performance of the MMMs.

In-situ growth of poly(m-phenylenediamine) in polyethylene (PE) matrix for nanofiltration membranes enabling outstanding selectivity of both mono-/di-valent ions and dyes/salt mixtures with enhanced water flux

Membrane-based nanofiltration is a crucial technique for treating dyestuff-salts wastewater, owing to its excellent selectivity towards mono/multivalent ions and organic matter. In this study, a facile and highly practical method was employed to enhance the hydrophilicity of the PE matrix through in-situ growth of poly(m-phenylenediamine) on the PE fibrils via the chemical oxidative polymerization of MPD. The inclusion of the poly(m-phenylenediamine) on PE enables the formation of homogenous and defect-free PA layer showing a unique honeycomb-like Turing morphology with characteristic crater-belt structure. Furthermore, the pendant amine groups from the poly(m-phenylenediamine) chain promotes the formation of a PA layer with a smaller effective mean pore size and a sharper pore size distribution, resulting from the formation of an extra polyamide network (reaction of PMPD with TMC) within the PA layer. The as-prepared PE-based NF membrane exhibits a high pure water permeance of 17.7 LMH bar−1, exceptional Na2SO4 rejection of 99.3%, and a long-term stability for cross-flow filtration for over 10 days. The PE-based NF membrane exhibits the water flux 2.2 times higher than that of the commercially available DK and DL membranes while maintaining a high salt rejection. Additionally, the PE-based NF membrane demonstrates exceptional selectivity, with a value of 115 for the separation of NaCl/Na2SO4 and 339.8 for Cl-/SO42- in a binary salt mixture. Furthermore, the PE-based NF membrane shows ultra-high selectivity values of 990 for CR/NaCl and 1039 for MB/NaCl in the treatment of dye/salt mixtures, respectively, which are significantly higher than those of the DK and DL membranes. The findings of this study highlight the potential of the in-situ growth of poly(m-phenylenediamine) on PE fibrils as a simple and cost-effective method for the modulation of hydrophilicity to enhance the NF membrane performance.

APTMS‐Modified Silica as a Thin‐Film Nanocomposite Forward Osmosis Membranes: Towards Enhanced Selectivity and Dye Rejection Stability for Congo Red and Rhodamine B

AbstractFumed silica (SiO2) is often applied in the modification of thin‐film composite (TFC) forward osmosis (FO) membranes due to its hydrophilicity. However, a key challenge to be solved is to improve its compatibility with organic matrices and dispersion in the material. In this study, we synthesized well‐designed nanoparticles of (3‐aminopropyl)trimethoxysilane‐modified SiO2 (APTMS‐SiO2) and applied them for the first time in the preparation of FO membranes. Furthermore, we systematically investigated the effects of different pretreated SiO2, SiO2 dosages, draw solution types, and concentrations on FO membranes. The results showed that APTMS‐SiO2 thin‐film nanocomposite with a silica dosage of 0.1 wt.% has the highest water permeate flux (Jw) (26.25 LMH, 370.43 % higher than the control TFC of 5.58 LMH) and the minimum specific reverse solute flux (SRSF) of 0.17 g/L with 1 M NaCl as the draw. The incorporation of APTMS effectively prevented mutual agglomeration of SiO2 and improved its dispersion. The Jw of 13.36 LMH after seven cycles and the rejection of above 96.6 % for Congo Red and 95.8 % for Rhodamine B indicated potential reusability and dye rejection. This work presents an alternative approach to prepare FO membranes with enhanced water flux and increased selectivity, and it also offers insights for the treatment of printing and dyeing wastewater using FO.

Transition from nanobubble-induced-blockage to enhancing water flux

Gas bubbles often form and accumulate in microfluidic devices, which is a critical obstacle in microfluidic applications. Here, we report by molecular dynamics simulations that “nanobubbles” can form and hinder water flow through the carbon nanotubes which are core components of nanofluidic devices. It is exceedingly difficult to remove the “nanobubble” trapped in the nanotube by a conventional method of hydrostatic or osmotic pressure gradient. Ratchet-like mechanics is applied to resume water flow powered by mechanical resonance. Interestingly, the water flow is even faster as compared to the pure water system without nanobubbles. Our findings provide a new means for solving pore-blocking problems in nanochannels and have potential applications in the design of high-flux nanofluidic systems.

Enhancing water flux and rejection performance through UV crosslinking: Optimization of surface modification of polyacrylonitrile (PAN)/acrylonitrile butadiene rubber (NBR) blend membrane using benzophenone as a crosslinking agent

Polyacrylonitrile (PAN)/acrylonitrile butadiene rubber (NBR) blend membranes were prepared by the phase inversion method using dimethylformamide as solvent. The blend membrane with a ratio of 85:15 was modified by ultraviolet (UV) radiation crosslinking of NBR using benzophenone as the crosslinking agent. The blend membrane was characterized through Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), porosity, contact angel, tensile strength, pure water flux, and rejection measurements. The blend membrane showed an increased pure water flux and decreased BSA rejection. However, the addition of benzophenone and UV radiation reduced the porosity and flux of the membrane, while improving the tensile strength and BSA rejection. The response surface method (RSM) with central composite design (CCD) using Design Expert software was employed to optimize the modification conditions of the PAN/NBR blend membrane, and the suggested membrane contained 2.5 wt% benzophenone and was exposed to UV radiation for 2 h. This membrane showed a pure water flux of 95.3 L/m2h, BSA rejection of 81.1%, and a tensile strength of 4.01 MPa, which is a 45% increase in water flux compared to the neat PAN membrane while showing better rejection and preserving the desired mechanical properties.