Permeation Flux Research Articles

Synergistic preparation of organic solvent nanofiltration membranes from polydopamine/polyethyleneimine interlayers with aminated attapulgite

This study utilized polydopamine (PDA)/polyethyleneimine(PEI) as the hydrophilic interlayer and added aminated attapulgite (ATP-NH2) to the aqueous phase monomer for interfacial polymerization (IP) to synergistically create nanofiltration membranes resistant to organic solvents. The hydrophilic nature of the PDA/PEI interlayer facilitates the rapid passage of polar solvents and results in excellent adhesion, ensuring tight bonding between the ultrafiltration support membranes and the active layer. Furthermore, the incorporation of the ATP-NH2 nanoparticles played a pivotal role in regulating the IP process. The resulting nanofiltration membranes, produced through the combined efforts of these components, achieved an optimal methanol permeation flux of 14.05 L m−2h−1 bar−1, with a rejection rate of Evans blue dye maintained at 99.42 %. Despite being exposed to N, N-dimethylformamide (DMF) at 80 ℃ for a period of 5 days, the nanofiltration membranes maintained both their exceptional separation effectiveness and stability. These findings suggest promising application prospects for the developed nanofiltration membranes.

Bioinspired surface silicification of cellulose-mediated PVDF membranes for significantly enhancing superhydrophilicity and anti-oil adhesion toward ultrafast oil/water emulsion separation

Cellulose is a widely used hydrophilic material due to its rich hydrophilic hydroxyl groups. However, the presence of its lipophilic segment will affect the antifouling performance. Finding strategies to improve this problem has attracted considerable attention. In this work, a layer of silica was applied to a cellulose-deposited polyvinylidene fluoride membrane through a straightforward in-situ bionic silicification process of tetraethyl orthosilicate. The contact angle and oil droplet contact test proved that the high-hydrophilicity and underwater superoleophobicity of the silicified membranes were significantly enhanced. The surface structure and composition were analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The results of show that this improvement was mainly attributed to the presence of silicon hydroxyl groups, buried cellulose chains, and micro-nanostructures composed of cellulose and silica. The stable silica coating also provided protection for the polymeric membrane against degradation after water washing for 24 h, ultrasonic treatment (40 KHZ) for 10 min or exposure to different pH levels (pH=1, 4, 9 and 12) and saturated sodium chloride solution for 24 h. Furthermore, the silicified membrane showed outstanding oil adhesion resistance and permeation flux, enabling effective purification of different oil-in-water emulsions that were stabilized by emulsifiers. Notably, the membrane achieved a high oil removal rate (> 99.4 %) of various emulsions (toluene-in-water, cyclohexane-in-water, tetrachloroethane-in-water, soybean oil-in-water, toluene-in-salt solution, toluene-in-acid solution and toluene-in-alkaline solution emulsions). In particular, for toluene-in-water emulsions (oil droplets in the emulsion ranged from 58.77 nm to 615.1 nm), a significantly enhanced permeation flux (4777 L·m−2·h−1·bar−1) was obtained at 0.8 bar pressure. Even after multiple cycles of separation, the flux was higher than that of the unsilicified membrane. Overall, this approach is mild, simple, efficient, and easily scalable, making it an ideal method for producing superhydrophilic coatings with substantial application potential.

Effects of porous supports and binary gases on hydrogen permeation in Pd–Ag–Y alloy membrane

This study investigates the effects of various porous supports and the presence of additional gases in the feed on hydrogen permeation using an unsupported Pd82–Ag15–Y3 membrane. The pore sizes and thicknesses of metallic supports varied from 1 to 270 μm and 50–3000 μm, respectively. The membrane was unsupported, synthesized by cold-rolling, and characterized by a thickness of 38 μm. The tests were performed at 400 °C with pressures ranging from 1.4 to 3 bar. Results showed that the unsupported Pd82–Ag15–Y3 membrane reached 12 % and 267 % higher hydrogen permeation than the supported membrane by 1 μm pore size and 50 μm thick woven mesh, and 1 μm pore size and 3 mm thick of porous stainless steel (PSS), respectively. The unsupported Pd82–Ag15–Y3 membrane showed one of the highest hydrogen permeability in the literature (7.5 × 10−8 mol m−1 s−1.Pa−0.5 at 400 °C). However, the presence of porous supports used to enhance the mechanical stability of the membrane negatively affected the hydrogen permeation due to mass transfer limitation. In addition, the presence of supports induced an unreal ‘n’ value for the Pd-based membrane, where the ‘n’ value is the exponent of the driving force in the equation of hydrogen transport, varying between 0.5 and 1. In particular, for the unsupported membrane, the ‘n’ value was 0.6, but it increased to 0.7 and 0.8 when supports with 1 μm pore size and 50 μm thick and 5 μm and 80 μm thick were utilized. Binary hydrogen permeation tests were also performed in the presence of N2, CH4, CO2, and CO at 400 °C by using unsupported and supported membranes to investigate the reduction in hydrogen permeation flux due to the effect of the supports plus the effect of the presence of other gas. The results revealed that CO had the highest inhibition effect for all the unsupported and supported membranes tested due to competitive adsorption on the surface. No superficial adsorption on the membrane was observed for N2, CH4, and CO2 during permeation, and they inhibited hydrogen permeation mainly due to depletion, dilution, and concentration polarization. The PSS_1–3000 indicated the lowest hydrogen permeation between the gas mixture and the porous support, whereas the presence of 40 % of the binary gas mixture had lower hydrogen permeation than porous support except for the PSS.

Optimization and Characterization of Mucoadhesive Buccal Films using Mimosa Seed-based Natural Polymer for Controlled Drug Release: A Sustainable Approach

Background: The present study attempted to develop cost-effective, biocompatible and biodegradable mucoadhesive buccal films exploring and using Mimosa pudica seed polymer, marking its potential as a sustainable drug delivery in pharmaceutical development. Methods: The extracted polymer was characterized for solubility, viscosity, loss on drying, pH, swelling index, starch, and mucilage ingredients. Compatibility between the polymer, drug, and excipients was assessed using FTIR analysis. Buccal film trial batches were formulated using the film casting technique and were optimized using the 23 full factorial design. Optimized formulation was characterized for drug release, permeability, mucoadhesive study, similarity, and difference factor along with histological and stability study. Results: The polymer’s pH, loss on drying, swelling index, and viscosity were 6.2, 6.8%, 81.77%, and 50,000 cP respectively. FTIR studies showed the compatibility between natural polymer, the model drug metoprolol succinate, and the excipients used. The early trial batches of polymeric films showed an extended drug release comparable to the standard polymers with a good permeability flux of 0.4048 ± 0.081 mcg*cm-2*h-1. The optimized film provided a controlled release of 52.31 ± 0.035% for more than 8 h following zero order kinetics. Mucoadhesive strength was found to be 32.25 ± 0.29 g. The similarity factor f2 (90.2) and difference factor f1 (8.197) indicated no significant difference compared to the standard formulation. Histological study demonstrated the non-irritant nature of the films and stability was established from the stability studies. Conclusion: Thus, a sustainable approach using natural polymeric buccal films was found promising for mucoadhesion and controlled release.

Development and performance investigation of a novel ultrasonic-assisted non-contact membrane distillation process to prevent membrane fouling

A novel non-contact membrane distillation (NCMD) process is proposed that prevents membrane fouling by preventing direct physical contact between the feed and membrane. The feed channel of the NCMD module is equipped with an ultrasonic transducer that provides high-frequency mechanical oscillations to the feed film, which forms a fine mist of droplets and water column. Experiments are conducted to determine the feed height required to maximize the evaporation rate, and the effects of feed temperature, flow rate, and ultrasonic power on the permeation flux. The results reveal that the highest permeation flux occurs at a feed height of 20 mm, and an increase in the feed height and flow rate decreases the ultrasonic cavitation effect, while a higher feed temperature and ultrasonic power significantly increases the permeation flux. At the feed temperature of 60 °C, feed flow rate of 1.0 L/min, and ultrasonic current of 600 mA, the permeation flux is 6.3 kg/m2h, which is 8.4 times greater than that of the NCMD process without ultrasonic treatment. The corresponding specific energy consumptions with and without the ultrasonication are 647 and 6028 kWh/m3, respectively. Moreover, the long-term experimental results indicate that the proposed system is unaffected by high feed concentrations.

High-performance COFs composite nanofiltration membrane fabricated by organobase catalyst

Covalent Organic Frameworks (COFs) composite nanofiltration (NF) membrane has high permeation flux and rejection. However, the reaction rate of COFs is relatively slow. Adding acid catalyst is a common method to shorten reaction time. However, the dissatisfactory synthesis rate will lead to irregular structure of COFs materials. In this work, it is the first time to use organobase as a catalyst to prepare COFs composite membrane. The COFs structure will be optimized and the membrane performance can be enhanced. The prepared TpPa-PIP membrane compared with acid catalyzed TpPa-HAc membrane has better permeability, permeance of 89 L m−2·h−1·bar−1 and CR rejection of 99.54 %. This improvement is because of the TpPa-PIP intermediate made slower reaction speed that improves the overall regularity and crystallinity of COFs. Therefore, it is better method for broadening the application of organobase-catalyzed in preparing membranes.

Highly selective alginate/CuO mixed matrix membranes for efficient dehydration pervaporation of various organic solvents

Pervaporation is an energy-efficient technique for dehydrating organic solvents from aqueous mixtures. To develop a highly selective pervaporation membrane with broad usage, we incorporated three types of CuO particles (solid CuO-S, sea urchin-like CuO-U, and porous CuO-P) into sodium alginate (Alg) for fabricating the Alg/CuO mixed matrix membranes (MMMs). The CuO syntheses and membrane preparation are simple and eco-friendly. The synthesized particles and membranes were systematically characterized. The improved hydrophilic feature of Alg/CuO MMMs was validated from the reduced water contact angle and higher water swelling ratio with increasing CuO wt%. When the Alg/CuO MMMs were applied to the pervaporation of 30 wt% water/isopropanol (IPA) at 25 ℃, both the permeation flux and separation factor were enhanced significantly compared to the pure Alg membrane. The separation efficiency followed the order of Alg/CuO-S MMMs < Alg/CuO-U MMMs < Alg/CuO-P MMMs, in good agreement with their water swelling tendency. The incorporation of 3 wt% porous CuO-P particles in MMM achieved the optimal dehydration efficacy (normalized total flux of 3.5 kg m-2h−1, separation factor of ca. 5000, and water purity of 99.96 wt%, with a stable performance over 168 h). A further larger loading wt% led to a decreased separation selectivity due to more void formation from particle aggregation. With an increase in feed temperature, both the permeation flux and separation factor were improved; however, the increase in feed water concentration deteriorated the separation selectivity while enhancing the flux. Furthermore, the high selectivity and broad applicability of Alg/3% CuO-P MMM were fruitfully demonstrated by exhibiting superior separation efficiencies in dehydrating various polar aprotic solvents compared with several membranes discussed in the literature.

Sub-nanometer size level regulation of biomimetic channels in porous membrane for high-capacity removal of toxic dye contaminants

Organic dyes are an important chemical with a market demand of millions of tons. However, their massive emissions, especially alkaline dye contaminants, have caused serious disruption of the ecosystem and even cancers. Inspired by bionic mass transfer, several amino acid fragments (carboxylic acid, γ-aminobutyric acid, and glutamic acid) are introduced into the 2.5 nm-pore size cavity through in-situ polymerization. The flexible amino acid chains facilitate the transport of guest molecules into the channels, accelerating their movement within the porous framework. These flexible chains are implanted into a 2.5 nm pore cavity, forming a 0.8–1.5 nano-meter-sized confinement space, bringing about the strong absorption capability for alkaline contaminants. Notably, LNU-74-glutamic acid achieves an ultra-fast absorption rate for toxic dye contaminants (4.74 g g−1h−1), as well as the highest capacity per unit area among all reported porous adsorbents, including porous carbons, metal–organic frameworks, porous polymers. After encapsulation in commercial polymer, the mixed-matrix membrane reveals (LNU-74-glutamic acid@MMM) a rejection rate greater than 98 % in various real water environments at permeation flux of ∼320 L m−2h−1, including strong acid/alkali, river water, and seawater.

HYDROGEN GAS RECOVERY THROUGH THE PERMEATION MEMBRANE BASED BIMETALLIC PALLADIUM ALLOY

Generally, the H2 gas produced from the industrial processes is not in a pure state but is mixed with other compounds. For example, the off-gas produced in the oil refinery process still contains CH4, H2, and other gases. Thus, the process of separating as well as recovering the valuable H2 gas from other gas compounds is of essential process. Currently, the H2 separation process is being developed with relatively low costs with good efficiency, namely using the permeation membranes separation process, in which the compounds with high permeability tends to be more easily separated. Here we report the hydrogen recovery process from the mixed H2/N2 off-gas contains 61 % hydrogen and 39% balancing nitrogen, by using the bimetallic Pd-Ag membrane, where the effect of the gas feed pressure (1 and 2 bar) and operating temperature (373.15, 423.15, 473.15, and 523.15, 573.15 K) on the resulting permeate flux is comprehensively studied. We found that the flux and permeability increased with the increase in the gas feed pressure and temperature. Under the same gas temperature of 373.15 K, the permeation flux at the 2 bar gas feed pressure was found to be 2.047 mol.s-1.m-2, which was 166% greater than that of 1 bar pressure, i.e. 1.204 mol.s-1.m-2. Meanwhile, under the same gas feed pressure of 2 bar, the permeation flux at the operating temperature of 573.15 K was found to be 2.103 mol.s-1.m-2, which is 104,9% greater than that of 373.15 K operating temperature, i.e. 2.047 mol.s-1.m-2. These findings suggest the breakthrough advantages of the Pd-Ag alloy membrane for its high hydrogen permeability at low pressure.

Hansen solubility parameters and quality-by-design oriented optimized cationic nanoemulsion for transdermal drug delivery of tolterodine tartrate

Tolterodine tartrate (TOT) is a selective anti-muscarinic drug to treat urinary urgency and overactive urinary bladder (OAB) occurring in children, renal disease and elderly patients. Oral delivery is associated with several adverse effects. We addressed HSPiP and QbD (quality by design)-oriented TOT loaded cationic nanoemulsions for transdermal delivery. Hansen solubility parameters (HSP) screened excipients based on theoretical solubility whereas, QbD optimized cationic nanoemulsions (CNE-TOT-6). Formulation characteristic parameters were desirable to execute targeted in vitro drug release and ex vivo permeation profiles. In vitro hemolysis was conducted at varied concentrations whereas, histopathological study supported the safety aspect of CNE-TOT6. A comparative bioavailability was carried out in a rat model. Capmul PG8 (CAP), tween 80, and PEG 400 (polyethylene glycol 400) were screened based on HSP and experimental solubility data. QbD suggested optimized content of CAP, tween 80, and PEG 400 to achieve the lowest value of size (184 nm), maximum % entrapment efficiency (87.2 %), high zeta potential (+32.6 mV), optimum viscosity (47.19 cP), and high extrudability (96 %) as compared to its gel. High gel consistency slowed down the drug release and permeation flux as compared to CNE-TOT6 suspension. Hemocompatible CNE-TOT6 increased pharmacokinetic parameters as compared to the control and gel without causing skin toxicity after application. Thus, HSPiP and QbD oriented cationic nanoemulsions are promising carriers to treat overactive urinary bladder.

Fluorinated MIL-53(Al) with breathing effect incorporated mixed matrix membranes for enhanced butanol/water pervaporation performance

Fillers of mixed matrix membranes (MMMs) play a crucial role in the pervaporation (PV) separation process. MIL-53(Al) is widely used in the preparation of MMMs due to its high stability, variable pore size, and ease of modification. In this study, fluorinated MIL-53(Al) (4F-MIL-53) was successfully synthesized using a solvent-free method. The introduction of fluorinated group made 4F-MIL-53 have better affinity for butanol and stronger hydrophobicity than MIL-53. Meanwhile, by utilizing its breathing effect, 4F-MIL-53 with narrow pore (4F-MIL-53(np)) could be transformed to 4F-MIL-53 with large pore (4F-MIL-53(lp)) through heat treatment. Also, the flexible framework of 4F-MIL-53 had good affinity with polymer chains. Then, 4F-MIL-53(lp) was introduced into PEBA to prepare MMMs for separating n-butanol/water. Compared with pristine PEBA membrane, the permeation flux and separation factor of the 4F-MIL-53(lp)-20/PEBA MMMs increased by 100.5 % and 90.4 %, respectively. Theoretical calculations indicated that there were multiple intermolecular forces between 4F-MIL-53(lp) and n-butanol, which enhanced the mixed matrix membrane affinity for n-butanol. The calculated self-diffusion coefficient of water in 4F-MIL-53 (lp) was lower than that in MIL-53, indicating that the introduction of fluorinated groups enhanced the hydrophobicity of MMMs. The proposed selection and modification strategies of MOF fillers provide excellent guidance for getting MMMs with high performance.

HSPiP and QbD oriented optimized stearylamine-elastic liposomes for topical delivery of ketoconazole to treat deep seated fungal infections: In vitro and ex vivo evaluations

The study explored stearylamine containing cationic elastic liposomes to improve topical delivery and efficacy of ketoconazole (KETO) to treat deeply seated fungal infections. Stearylamine was used for dual functionalities (electrostatic interaction and flexibility in lipid bilayer). Hansen solubility program (HSPiP) estimated Hansen solubility parameters (HSP) based on the SMILE file and structural properties followed by experimental solubility study to validate the predicted values. Various formulations were developed by varying phosphatidylcholine and surfactants (tween 80 and span 80) concentration. To impart cationic properties, stearylamine (1.0 %) was added into the organic phase. Using quality by design (QbD) method, we optimized the formulations and evaluated for vesicle size, polydispersity index, zeta potential, morphology (scanning electron microscopy), in vitro drug release (%), and ex vivo permeation profiles. Result showed that there is a good correlation (0.65) between HSPiP predicted and actual experimental solubility of KETO in water, chloroform, S80, and tween 80. Spherical OKEL1 showed an established correlation between the predicted and the actual formulation parameters (size, zeta potential, and polydispersity index) (259 nm vs 270 nm, +2.4 vs 0.21 mV, and 0.24 vs 0.27). OKEL1 was associated with the highest value of %EE (83.1 %) as compared to liposomes. Finally, OKEL1 exhibited the highest % cumulative permeation (49.9 %) as compared to DS (13 %) and liposomes (25 %). Moreover, OKEL1 resulted in 4-fold increase in permeation flux as compared to DS which may be attributed to vesicular mediated improved permeation and gel based compensated trans epidermal water loss in the skin. The drug deposition elicited OKEL1 and OKEL1-gel as suitable carriers for maximum therapeutic benefit to treat deeply seated fungal infections.

Preparation and performance of Rb+ doped La2Ce2O7-δ proton conductor for hydrogen permeation membranes

Compared with perovskite-type proton conductor materials, fluorite-type La2Ce2O7-δ has good tolerance to H2O and CO2, and is a promising candidate material for hydrogen permeation membranes. In this work, Rb+ doped La2Ce2O7-δ was proposed as a means to enhance both the hydrogen permeation flux and electrochemical performance of La2Ce2O7-δ. Experimental findings indicate that the sample exhibits the highest conductivity and hydrogen permeation flux at a doping concentration of 15 % (La1.85Rb0.15Ce2O7-δ). Specifically, the hydrogen permeation flux of Pt-La1.85Rb0.15Ce2O7-δ increased by 1.5 times when the dry sweeping gas was replaced with wet sweeping gas during hydrogen permeation testing. It was observed that variations in membranes thickness resulted in distinct hydrogen permeation control mechanisms. Moreover, La2Ce2O7-δ samples doped with various concentrations of Rb+ exhibited excellent stability in a wet atmosphere containing 20 % CO2, suggesting their potential as ceramic hydrogen separation membranes materials.

Advanced photocatalytic membrane GO-NiFe@SiO2/PVDF for efficient decontamination of synthetic dyes in batik wastewater with superior antifouling features

A novel composite membrane, GO-NiFe@SiO2/polyvinylidene fluoride (PVDF), was prepared via the sol-gel method for nanocomposite synthesis and phase inversion method for membrane fabrication. The investigation encompassed the structural features and properties of the nanocomposite membranes, including photocatalytic activity under UV type C, antifouling capability, and self-cleaning behavior. The degradation of dyes in real Batik wastewater followed pseudo-first-order kinetics, with the GO-NiFe@SiO2/PVDF 1 wt% nanocomposite membranes exhibiting a highest dyes removal efficiency up to 90.50 % within 8 h, compared to the pristine PVDF membrane (60.95 %). The XRD pattern analysis indicates that the incorporation of GO-NiFe@SiO2 into the PVDF membrane induced a transformation in the semi-crystalline phase of PVDF, shifting from the alpha-phase to the beta-phase, consequently facilitating the development of electrostatic charge on the membrane surface. The pore-size distribution analysis revealed that all prepared membranes fall within the range of nanofiltration and tight ultrafiltration (NF-TUF). Additionally, the photocatalytic membrane demonstrated enhanced permeation flux of 30.46 L.m−2.h−1 and flux recovery rate up to 92.57 % under simulated UV light irradiation, showcasing improved antifouling capability. Moreover, the membrane exhibited outstanding cycle test with 6 consecutive cleaning every 3 h, self-cleaning efficiency, with 61.32 % cleaning efficiency under UV irradiation. The incorporation of GO-NiFe@SiO2 enhanced the physicochemical properties of the photocatalytic membrane, including hydrophilicity, surface topologies, and mechanical strength, thereby improving photocatalytic anti-fouling performance and expanding the potential applications of membrane filtration technology.

Pulsed Airstream-Driven Hierarchical Micro-Nano Pore Structured Triboelectric Nanogenerator for Wireless Self-Powered Formaldehyde Sensing.

Formaldehyde (HCHO), as a common volatile organic compound, has a serious impact on human health in the daily lives and industrial production scenarios. Given the security issue of HCHO detection and danger warning, a ZIF-8/copper foam based pulsed airstream-driven triboelectric nanogenerator (ZCP-TENG) is designed to develop the self-powered HCHO sensors. By combining contact electrification and electrostatic induction, the ZCP-TENG can be utilized for airflow energy harvesting and HCHO concentration detection. The short-circuit current and output power of the ZCP-TENG can reach 2.0 µA and 81 µW (20 ppm). With the high surface area, abundant micro-nano pores, and excellent permeation flux, the ZCP-TENGs exhibit excellent HCHO sensing response (61.3% at 100 ppm), low detection limit (≈2 ppm), and rapid response/recovery time (14/15 s), which can be served as a highly sensitive and selective HCHO sensor. By connecting an intelligent wireless alarm, the ZCP-TENGs are designed to construct a self-powered warning system to monitor and remind the HCHO of exceedance situations. Moreover, by combining a support vector machine model, the difference concentrations can be quickly identified with an average prediction accuracy of 100%. This study illustrates that ZCP-TENGs have broad application prospects and provide guidance for HCHO monitoring and danger warnings.

Rough and porous silica-modified fiber membranes decorated with oleic acid for ultra-high flux and pH-responsive oil/water separation

The design of fiber membranes with both ultra-high flux and pH-responsive oil/water separation is challenging but of great significance to environmental protection and human health. In this work, the pH-responsive fiber membranes were prepared by immersing the silica-modified polyacrylonitrile fiber substrates into oleic acid solution. The obtained membranes exhibited highly rough surface structures (Ra = 14.26 µm), large pore sizes (5.35 µm), high porosities (86.04%), and pH-responsive functional groups, respectively. The pH-responsive fiber membranes also had superhydrophobic surfaces and excellent selective separation for oil/water mixtures, for example, a trichloromethane permeation flux of 87,829 L m-2h-1 for immiscible oil/water separation, and a water permeation flux of 69,802 L m-2h-1 after turning the pH of water from 7 to 13. The above data were much higher than those of stimulus-responsive fiber membranes used for oil/water separation. In addition, the pH-responsive fiber membranes were also used for separating water-in-oil emulsions and oil-in-water emulsions, and achieved the highest separation flux of 15,120 L m-2h-1. This work provides a simple strategy for the preparation of a stimulus responsiveness and high-performance material that can be used in the direction of treating practical oily wastewater.

Co-doping induced Mn-vacancy LiMn2O4 based membrane electrode for lithium extraction by electrochemically switched ion permselective process

LiMn2O4 (LMO) is considered an effective electroactive material for electrochemical lithium extraction from aqueous solutions. However, the stability issue limits its practical application. Herein, Co-doping induced Mn-vacancy LiMn2O4 (LCMO) powders were synthesized by a high-temperature solid-phase method, which were further applied to prepare an electrochemical permselective membrane electrode for selective lithium-ion extraction. Physicochemical characterizations combining with density functional theory (DFT) calculations revealed that Co-doping at 8a site will induce the formation of Mn vacancies in LMO, which can reduce the content of easily dissolutive trivalent Mn (Mn3+) and lower the Li+ migration energy barrier. As a result, the Li+ permeation flux of optimized LCMO-0.04 (Co: Mn = 0.04: 1.96) based membrane electrode (156.809 mmol·m−2·h−1) was increased by 85.65 % compared to that of LMO-based one (84.461 mmol·m−2·h−1) in an electrochemically switched ion permselective (ESIP) system. The selectivity factors of Li+/ Na+, Li+/Mg2+, Li+/ K+ for the LCMO-0.04 based membrane electrode were up to 10.06, 11.69, and 15.19, which were about twice as high as those for LMO membrane based one. After 1000 circles of cyclic voltammetry (CV) tests, the CV area of the LCMO-0.04 based membrane electrode maintained 91.59 % of the initial value, demonstrating remarkable electrochemical stability.

Study of the dual role mechanism triggered by in-situ cross-linking in hollow fiber membrane matrix

In this paper, a novel polyvinylidene fluoride (PVDF) hollow fiber membrane with uniform pore size and hydrophilic cross-linked network in membrane matrix was developed by non‐solvent induced phase separation method. The dual role mechanism of in-situ cross-linking in regulating molecular chain arrangement during phase separation and preventing deterioration of membrane mechanical properties were analyzed. The results demonstrated that the cross-linked network formed by in-situ crosslinking entangled with PVDF molecular chains which improved the regularity of PVDF molecular chains, increasing the uniformity of the pore size distribution, the percentage of the most probable pore size of the modified membrane increased to 93.25 %. The cross-linked network was immobilized in the membrane which formed semi-interpenetrating structure, maintaining the mechanical properties of the membrane. The permeation flux of the modified membrane increased by 24.1 times to 477.7 L m−2 h−1 compared to the original PVDF membrane. The rejection of BSA was maintained at 98.5 %, with the tensile strength increased to 2.52 MPa. The modified membrane exhibited persistent hydrophilicity in 21 days washing experiment with improved antifouling performance.

Intercalation of GO-Ag nanoparticles in cellulose acetate nanofiltration mixed matrix membrane for efficient removal of chromium and cobalt ions from wastewater

Cellulose acetate (CA)/Polyethylene glycol (PEG) blended composite nanofiltration (NF) membrane encompassing graphene oxide-silver (GO-Ag) nanoparticles (NPs) has been successfully synthesized by dissolution casting techniques. The effect of different NP loadings on membrane morphology, surface roughness, hydrophilicity surface charge and permeation flux were evaluated. Owing to Donnon exclusion, steric hindrance, and solution diffusion mechanism, the synthesized modified membranes exhibited excellent rejection rates in the order of Co (II) (99 %) > Cr (VI) (91 %). Furthermore, pure water flux (PWF) of the modified membrane was obtained 660.56 L/m2h which is 78.45 % greater than pristine membrane. Due to its high surface hydrophilicity, surface roughness, and porosity, modified membrane exhibited good antifouling characteristics. The results indicated that the intercalation of GO-Ag NPs with a loading ratio of 0.8 wt% leads to the optimum membrane for Cr (VI) and Co (II) removal. The present work demonstrates the potential application of GO-Ag/CA modified NF mixed matrix membrane for serving as a promising platform for eliminating heavy metal ions in wastewater.

Eco-friendly, highly interpenetrated and slightly swollen pHEMA hydrogel foam for durable underwater superoleophobicity and emulsion separation

Despite the emergence of hydrogels as ideal candidates for preparing the superhydrophilic materials for emulsion separation, their structural stability and swelling still hinder their long-term use, mainly due to structure defects after swelling. Herein, differing from the common modification, the eco-friendly poly 2-hydroxyethyl methacrylate (pHEMA) hydrogel foam was designed and synthesized via a one-step strategy by using the high internal phase emulsion (HIPE) template method, which endowed it with a highly interpenetrated porous structure. Unlike the normal swellable hydrogels such as poly(N-isoproplyacrylamide) (PNIPAM) hydrogel, or modified hydrogel coatings, the pHEMA hydrogel foam displayed stable structure and underwater superoleophobicity after 20 d of immersion in water. The pHEMA hydrogel foam could separate different kinds of highly surfactant-stabilized oil-in-water (O/W) emulsions with a high separation efficiency of 99.3% for liquid paraffin emulsion obtained solely under gravity-driven. Additionally, it exhibited excellent antifouling performance and long-term acid/alkali tolerance over 100 h without decrease in emulsion separation efficiency (98.0%, oil/water ratio of 99:1) and permeation flux (over 2000 L·m−2·h−1) attributed to its stable bulky structure. Moreover, the pHEMA hydrogel foam demonstrated high cell viability of 96.87% and 95.96% after culturing the 3T3 clone A31 cells in the pHEMA hydrogel foam for 24 h and 48 h, respectively, indicating good biocompatibility. Hence, our work provides a new design to develop an eco-friendly bulk hydrogel foam that achieves stable structure and performance for emulsion separation.