Membrane Surface Research Articles

Enhancement of membrane filtration performance and mitigation of sludge calcification in an intermittent anaerobic membrane bioreactor treating high-calcium wastewater

Anaerobic membrane bioreactors (AnMBRs) can alleviate the inhibitory effect of sludge calcification on anaerobic process when treating high-calcium wastewater. However, sludge calcification induced by high-calcium wastewater and flocculated sludge formation under reactor aeration shear will inhibit membrane filtration performance. In this study, an intermittently operated AnMBR (A2) was used to treat high-calcium wastewater, and continuously operated AnMBR (A1) was used as the parallel control. When treating 200–1000 mg/L calcium ion wastewater, A2 achieved a stable chemical oxygen demand removal efficiency of 91.8±3.9 %. The methane production of A2 was 188.2±22.5 mL/(gVSS⋅d), which was marginally higher than the continuous AnMBR (A1) methane production of 174.7±11.7 mL/(gVSS⋅d). Analysis of the microbial community demonstrated significant enrichment in hydrolyzing acidifying bacteria and archaea in A2, compared to A1, which played a crucial role in improving the performance of anaerobic process. A1 exhibited a maximum transmembrane pressure (TMP) of 19.6 kPa, and scanning electron microscopy (SEM) analysis revealed the deterioration of membrane fouling due to sludge calcification on the membrane surface. Surprisingly, the maximum TMP of A2 was just 3.6 kPa during the study. When treating 1000 mg/L of high calcium wastewater, the average effluent calcium concentration in A2 was 650 mg/L, which indicated that A2 effectively retained calcium ions. SEM analysis revealed that anaerobic sludge had a tendency to agglomerate, which slowed down membrane fouling in A2. Sludge agglomeration was due to intermittent operation effectively increasing the contact time of sludge with calcium ions, thereby stimulating the protein secretion of extracellular polymers. These results showed that the intermittent operation effectively mitigated membrane fouling. This work provides a new strategy for comprehensively addressing the challenges of high-calcium wastewater and achieving the stable performance of anaerobic reactors.

Potential protumor function of CD74 in clear cell renal cell carcinoma.

CD74 is a transmembrane protein that functions as a specialized chaperone of HLA class II and CD74 in tumor cells was suggested to be involved in cell proliferation in several kinds of malignant tumors. CD74 is also known to be expressed in macrophages, therefore, we investigated the CD74 expression in clear cell renal cell carcinoma (ccRCC). Immunohistochemistry of CD74 indicated that CD74 was expressed not only in cancer cells but also macrophages. CD74 was detected in surface membrane and cytoplasm of cancer cells in 92 of 94 cases (98%) and of 87 of 94 cases (93%). CD74 was expressed both in cancer cells and TAMs in 86 of 94 cases (91%). In vitro studies using cancer cell lines and monocyte-derived macrophages stimulated by anti-CD74 antibodies showed that CD74 signal accelerated cancer cell proliferation and macrophage activation. However, macrophage activation via CD74 signal did not influence macrophage-mediated cancer cell growth. RNA-sequence of macrophages stimulated by anti-CD74 antibodies indicated that CD74 signal was associated to inflammatory responses in macrophages. In conclusion, we examined the expression and functional significance of CD74 in ccRCC using tissue specimens and cell culture studies. The function of CD74 was suggested to be different in cancer cells and in macrophages, and further studies are necessary to clarify the functional significance of CD74 in ccRCC.

Constructing a stable photocatalytic functional layer through cross-linking of chitosan and l-mannose for efficient removal of doxycycline hydrochloride in single-pass flow mode

The development of technologies for effectively eliminating antibiotic pollutants from aquatic environments is crucial for preserving environmental quality. In this study, the 0D/3D Ag/AgI/MOF-808 photocatalysts were immobilized on the surface of polyethersulfone membrane using the Schiff-base reaction between chitosan and l-mannose to form a photocatalytic membrane (PES-CSLM-1) with a unique “sandwich” structure, which consists of a cross-linked layer, a functional layer, and a supporting layer. Under 240 min of visible light irradiation, the removal rate of doxycycline hydrochloride (DOX) (10 mg/L) by PES-CSLM-1 membrane was more than 90 %, which was 26.2 % higher than that of PES-CS membrane. The flux recovery rate of the membrane after photocatalytic self-cleaning reached 92.2 %, notably surpassing that achieved through physical cleaning (73.75 %), indicating that the photocatalysis effectively converted irreversible pollutants into reversible pollutants. After four cycles, the DOX removal efficiency of PES-CSLM-1 remained near 80 %, and the membrane structure and crystal structure did not change significantly. ·OH and ·O2− play important roles in the degradation process of DOX, and three potential degradation pathways for DOX were proposed. Toxicity analysis revealed that the environmental risk was significantly reduced during the DOX degradation process.

Determination of Tetracaine and Oxymetazoline in Drugs and Saliva via Potentiometric Sensor Arrays Based on Fluoropolymer/Polyaniline Composites

AbstractA growing interest in dental practice in intranasal anesthesia using tetracaine and oxymetazoline dictates the need for their simultaneous determination in combination drugs and human saliva. Potentiometric multisensory systems based on perfluorosulfonic acid membranes, including polyaniline‐modified ones, were developed for these purposes. A change in the distribution of the sensor sensitivity to the related analytes was achieved by variation of the conditions for concentration polarization at the membrane interface with a studied solution due to a change in the intrapore volume, nature, and availability of the sorption centers, as well as the hydrophilicity of the membrane surface that were specified by the conditions for their synthesis and subsequent hydrothermal treatment. Reversibility of the analyte sorption using the chosen conditions for regeneration provided long‐term stable work of both the sensors and the calibration equations established by multivariate linear regression. The membrane modification promoted their resistance to fouling. The relative errors of the simultaneous tetracaine and oxymetazoline determination in the combination drug solutions were no greater than 7% and 11%, while in the artificial saliva solutions, they were 15% and 17%, respectively, when an array of the cross‐sensitive sensors based on the composite membranes prepared by different methods was used. The analysis errors were reduced to 3%–6% when analyzing the drug and to 0.2%–6% when analyzing the artificial saliva if an array was organized with the sensors based on the membrane with the dopant and the membrane without it, due to the decreasing correlation between their responses.

Biomimetic interlayer brought unexpected enhancement in permeability and rejection of polyamide nanofiltration membrane

Construction of interlayer between porous substrate and polyamide (PA) layer has been proved to be an effective way in improving membrane separation performance by the regulation of membrane structure and chemical properties. In present study, biomimetic material—1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) lipid bilayer was selected to serve as the interlayer prepared by suction filtration due to its unique advantages such as smooth, continuous, uniform and hydrophilic surface. The results showed that DOPE interlayer effectively lowered the diffusion rate of piperazine (PIP) from membrane surface to organic phase and thus contributing to the thinner and smoother PA layer. The permeability of the interlayer-based PA membrane reached 35.9 L/m2·h·bar, which was 190 % higher than pure PA NF membranes. More important, the interlayer-based PA membrane exhibited excellent Na2SO4 rejection about 99.8 % accompanied by a good separation selectivity between univalent and bivalent ions. Besides, the interlayer-based PA membrane possessed good stability to the changes of operating pressure, concentration and pH of feed solution, and the long-term NF test. Meanwhile, it performed well in removing NTU, TOC, Mg2+ and SO42− in the treatment of surface water and showed its potential in the practical application. In all, the present work brought new interlayer material in fabricating high-performance NF membrane.

Porous nanofiber/microparticles-structured membrane of polymyxin B modified poly(styrene-random-glycidyl methacrylate) by electrospray for endotoxin removal in blood purification

Inspired by the kidney's renal glomerulus, a binary solvent mixture system of tetrahydrofuran (THF) and methanol was used to form porous nanofiber/microparticles (PNfMp) during electrospray technology. Poly(styrene-random-glycidyl methacrylate) (PSGM) was synthesized by atom-transfer radical polymerization as a supporting material for the electrospray process. During the electrospray process, THF, with a lower boiling point, evaporated first, forming the PNfMp of PSGM containing the nanoemulsified methanol with a higher boiling point. After the solidification of the PSGM, the nanoemulsified methanol evaporated, creating highly porous microparticles/nanofibers of PSGM. The Brunauer-Emmett-Teller (BET) surface area of the PNfMp-structured PSGM membranes reached 986.6 m2/g. We further investigated modifying the surfaces of the electrospun membranes with polymyxin B (PMB) through the epoxy groups of PSGM for endotoxin adsorption. The maximum adsorption capacity of endotoxin on the PMB-modified PSGM membrane with a PNfMp structure is approximately 3.1 EU/mg, which is much higher than that without a PNfMp structure, at 0.7 EU/mg. A filter packed with the PMB-modified PSGM membrane was constructed to remove endotoxin from human plasma. The removal efficiency reaches almost 100 % for 14 mL using 3.2 mg of the membrane at a flow rate of 1 mL/min. Our proposed method provides an ideal strategy to prepare PNfMp membranes for endotoxin removal in blood purification.

A Membrane-Confined Signal Amplification Strategy for Sensitive Monitoring of Extracellular Enzymatic Activity Upon Drug Stimulus.

Extracellular enzymes are not only strongly correlated with disease development but also play critical roles in modulating immune responses. Therefore, real-time monitoring of extracellular enzymatic activity can afford straightforward insights into their spatiotemporal dynamics upon drug stimulus, and provide promising tools to unravel their key roles in modulating the cell signaling. Although DNA-based sensing probes have been frequently developed for the detection of a variety of biomolecules, there still lacks a modular design strategy for amplified imaging of extracellular enzymatic activity associated with live cells. Herein, we developed an enzymatically triggerable signal amplification strategy for real-time dynamic imaging of extracellular enzyme activity through a cell membrane-confined hybrid chain reaction (HCR). We demonstrated that, by modifying the initiator DNA with enzyme-specific incision sites and cholesterol tail, extracellular enzyme-trigged HCR could be fulfilled on the surface of the cellular membrane, facilitating amplified detection of extracellular enzymatic activity. Dynamic monitoring of enzyme secretion of cancer cells upon stimulus or macrophage cells upon inflammation challenge has also been achieved. We envision that the design strategy could provide valuable information for dissecting the role of extracellular enzymes in modulating cell responses to drug treatment.

Release of ions enhanced the antibacterial performance of laser-generated, uncoated Ag nanoparticles

Identifying the antibacterial mechanisms of elemental silver at the nanoscale remains a significant challenge due to the intertwining behaviors between the particles and their released ions. The open question is which of the above factor dominate the antibacterial behaviors when silver nanoparticles (Ag NPs) with different sizes. Considering the high reactivity of Ag NPs, prior research has primarily concentrated on coated particles, which inevitably hinder the release of Ag+ ions due to additional chemical agents. In this study, we synthesized various Ag NPs, both coated and uncoated, using the laser ablation in liquids (LAL) technique. By analyzing both the changes in particle size and Ag+ ions release, the impacts of various Ag NPs on the cellular activity and morphological changes of gram-negative (E. coil) and gram-positive (S. aureus) bacteria were evaluated. Our findings revealed that for uncoated Ag NPs, smaller particles exhibited greater ions release efficiency and enhanced antibacterial efficacy. Specifically, particles approximately 1.5 nm in size released up to 55 % of their Ag+ ions within 4 h, significantly inhibiting bacterial growth. Additionally, larger particles tended to aggregate on the bacterial cell membrane surface, whereas smaller particles were more likely to be internalized by the bacteria. Notably, treatment with smaller Ag NPs led to more pronounced bacterial morphological changes and elevated levels of intracellular reactive oxygen species (ROS). We proposed that the bactericidal activity of Ag NPs stems from the synergistic effect between particle-cell interaction and the ionic silver, which is dependent on the crucial parameter of particle size.

Trans-membrane piezoelectric activation of peroxymonosulfate for effective control of waterborne antibiotic resistance dissemination

Increasing prevalence of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) constitutes an emerging water safety issue globally. However, the effectiveness of current water treatment techniques in the control of ARGs dissemination remains controversial. Here, we develop a dual-zone strategy based on piezoelectric membrane filtration to efficiently eliminate waterborne antibiotic resistance. Following complete ARB inactivation and effective ARGs reduction in the retentate near the membrane surface (zone 1), a subsequent trans-membrane process (zone 2) further promotes ARGs elimination in the permeate, due to boosted interactions between ARGs and reactive oxygen species (ROS) generated from piezoelectric peroxymonosulfate activation and minimized ROS competition from inactivated ARB within piezocatalytic channels. The abundance of ARGs was largely reduced to ~1.0 × 103 copies·mL−1 in the permeate from ~5.0 × 106 copies·mL−1 in the feed solution. The singlet oxygen (1O2) is demonstrated to be primarily responsible for ARB inactivation, while 1O2, hydroxyl radical (•OH), sulfate radical (SO4·−) and superoxide radical (·O2−) can all participate in ARGs degradation. Our work demonstrates that the piezoelectric membrane-based dual-zone strategy has great potential to control the risk of ARGs dissemination.

Dynamic Deposition of PDA on a Hollow Fiber Ceramic Membrane for Oily Water Treatment.

Ceramic membranes have been widely used in oil-water treatment; however, membrane fouling remains a challenge that must be addressed to improve the process feasibility. A thin layer of polydopamine (PDA) was dynamically deposited on the surface of the alumina hollow fiber membranes to reduce oil adhesion. The PDA-alumina membranes were characterized by using SEM-EDS, AFM, and water contact angle measurements. The performance of the modified membranes was evaluated using synthetic crude oil emulsions (100 mg·L-1) in a crossflow system. Membranes modified with PDA exhibited 97% oil rejection, and a stabilized permeate flux of 463 L·h-1·m-2 with a relative flux reduction of 60% and a flux recovery ratio of 75% was observed after cleaning, indicating lower oil adhesion and better fouling reversibility. The most predominant fouling mechanism for the modified membranes seems to be cake filtration because of the reduction in pore size due to the deposition of the PDA layer.

Tuning polyamide membrane chemistry for enhanced desalination using Boc-protected ethylenediamine and its in situ Boc-deprotection

The scarcity of freshwater resources, driven by rapid population growth and industrialization, underscores the urgent need for advanced desalination technologies. This research aims to meet this critical demand by enhancing the performance of polyamide membranes through innovative chemical tuning of the active layer. By strategically using Boc-protected ethylenediamine (EDA), we can precisely control the membrane’s surface properties. One amino group in EDA is protected with a Boc group, allowing the other to participate in the interfacial polymerization (IP) reaction with meta-phenylenediamine (MPD) and trimesoyl chloride (TMC). This inclusion of Boc-protected EDA enables in situ tuning of the active layer chemistry during polymerization. Subsequent removal of the Boc protection generates hydrophilic ammonium groups on the membrane surface, enhancing its desalination capabilities. As a result, three distinct membranes were fabricated and thoroughly characterized: MPD-TMC (control), MPD-TMC-EDA-Boc, and MPD-TMC-EDA-Deboc. At 20 bar and 2000 ppm NaCl feed, the MPD-TMC-EDA-Deboc membrane demonstrated superior desalination performance with a salt rejection of 98 ± 0.5% and a permeate flux of 25 L m−2 h−1; an increase of 25% compared to the control membrane. For the seawater nanofiltration (NF) permeate with a TDS of 33,700 ppm, a salt rejection of 97% and a permeate flux of 23 L m−2 h−1 was recorded at 20 bar. The MPD-TMC-EDA-Deboc membrane showed enhanced antifouling performance (95 ± 1% flux recovery) compared to the control MPD-TMC membrane with 93 ± 1% flux recovery. The Boc-protection/deprotection strategy demonstrated the high potential of this approach to significantly enhance the performance of polyamide membranes for desalination applications.

Membrane fouling analysis of air-gap membrane distillation (AGMD) for recovery of water and removal of antibiotics from a model wastewater containing antibiotics and humic acid

The study investigates the efficiency of air-gap membrane distillation (AGMD) in water recovery and antibiotics removal from wastewater, focusing on high-concentration scenarios. Experimental findings reveal enhanced membrane performance with increasing the feed temperature, resulting in vapor permeate fluxes of up to 5 kg/m2.h at higher temperatures. Despite experiencing flux reduction caused by fouling from humic acid (HA) in the feed antibiotics solution, the antibiotics consistently maintain near-complete rejection rates (>99%) over 48 h. The foulant on the membrane surface was illustrated by SEM imaging. To know the temperature polarization and the fouling resistance, mathematical modeling was used, and it validates experimental results, elucidating temperature polarization effects and mass transfer coefficients. An increase in feed flow rates reduced thermal boundary layers, enhancing heat flux. Higher temperatures reduced HA fouling resistance. Therefore, AGMD proves effective in water recovery and antibiotics removal, with mathematical models aiding fouling understanding for future research and detailed computational fluid dynamics (CFD) models.

Preparation and Selective Adsorption Performance of the Carboxymethyl Salix psammophila Wood Powder-Imprinted Membrane for Tetracycline.

Carboxymethyl Salix psammophila wood powder-imprinted membranes (CMSM-MIPs) were prepared by using wet spinning technology and molecular-imprinting technology for the selective removal of tetracycline from wastewater. Scanning electron microscopy, X-ray diffraction, thermogravimetry, and X-ray photoelectron spectroscopy characterizations demonstrate that CMSM-MIPs retain the membranous structure of Carboxymethyl Salix psammophila wood powder membranes, successfully encapsulate thin layers of imprinted polymers on the membrane surface, and exhibit excellent thermal stability. The adsorption results showed that CMSM-MIPs had the highest selective adsorption capacity for tetracycline, which was 253.8 mg/g. In addition, the adsorption capacities for oxytetracycline and chlortetracycline were 208.8 and 188 mg/g, respectively. It can be observed that CMSM-MIPs not only exhibit a high adsorption capacity for tetracycline but also demonstrate good adsorption capacities for oxytetracycline and chlortetracycline. The experimental results showed that CMSM-MIPs were best fitted with pseudo-second-order kinetics and most consistent with Freundlich fitting. The regeneration experiment showed that CMSM-MIPs still had good regeneration performance after 5 regeneration cycles. In conclusion, the CMSM-MIPs can not only have the natural adsorption performance of Salix psammophila wood powder but also give it higher selectivity through molecular imprinting, so as to achieve efficient removal of target organic pollutants in water.

Preparation of an anticoagulant polyethersulfone membrane by immobilizing FXa inhibitors with a polydopamine coating

Anticoagulation treatment for patients with high bleeding risk during hemodialysis is challenging. Contact between the dialysis membrane and the blood leads to protein adsorption and activation of the coagulation cascade reaction. Activated coagulation Factor X (FXa) plays a central role in thrombogenesis, but anticoagulant modification of the dialysis membrane is rarely targeted at FXa. In this study, we constructed an anticoagulant membrane using the polydopamine coating method to graft FXa inhibitors (apixaban and rivaroxaban) on the membrane surface. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to characterize the membranes. The apixaban- and rivaroxaban-modified membranes showed lower water contact angles, decreased albumin protein adsorption, and suppressed platelet adhesion and activation compared to the unmodified PES membranes. Moreover, the modified membranes prolonged the blood clotting times in both the intrinsic and extrinsic coagulation pathways and inhibited FXa generation and complement activation, which suggested that the modified membrane enhanced biocompatibility and antithrombotic properties through the inhibition of FXa. Targeting FXa to design antithrombotic HD membranes or other blood contact materials might have great application potential.

Mixed-matrix membrane designed with water channels and sieving effect for effective removal of heavy metals

The challenge of eliminating heavy metal ions from water has been addressed using Polysulfone (PSf) membranes, which have demonstrated significant potential in treating contaminated solutions. This research aimed to improve the permeability and separation performance of PSf membranes by incorporating Al2SiO6 into their structure. The introduction of Al2SiO6 into the membrane matrix was achieved through the nonsolvent-induced phase separation (NIPS). The resulting mixed-matrix membrane (MMM) exhibited improved efficiency in water filtration. The inclusion of Al2SiO6 led to desirable changes in membrane properties such as hydrophilicity, contact angle and porosity, thereby enhancing the performance of heavy metal ion removal capability. Under a pressure of 2 bar, the mixed matrix membranes achieved rejections exceeding 95 % for lead and 70 % for arsenic. Furthermore, the occurrence of Al2SiO6 enhanced the anti-fouling assets of the PSf membrane by increasing its hydrophilic nature and facilitating the development of a hydration layer, which tends to prevent the interactions between the membrane surface and foulant. These properties make these membranes suitable candidates for separating toxic ions from water.

Biofouling control of thermophilic bacteria in membrane distillation

Previously, fouling of MD membranes was perceived to be minimal due to the operational conditions preventing bacterial growth. However, recent studies presented fouling of MD membranes, largely due to various halophilic and thermophilic bacterial. The current study presented potential of antibacterial cellulose nanocrystals (CNCs) capped silver nanoparticles (AgNPs) towards biofouling control in MD water desalination processes. Interestingly, the CNCs were used as capping and reducing agent in a microwave mediated synthesis of AgNPs. The green synthesis approach of AgNPs and its successful use in MD processes was reported for the first. The MD experiments were carried out using a series of modified PVDF membranes and feed solution spiked with a thermophilic G. stearothermophilus. Upon evaluation of fouled membranes, particularly PVDF, PVP-equipped PVDF, and f-CNTs-modified PVDF, the surface energy of interactions were −131 mJ/m2, −31.5 mJ/m2, −28.6 mJ/m2, suggesting favorable interaction between the membranes and bacterial foulant. The findings of this study were supported by fouling layer and bacterial growth as seen from scanning electron microscopy, atomic force microscopy and Fourier transform infrared results. Upon membrane surface modification using CNCs-capped AgNPs, bacterial growth on membrane surface was reduced. Specifically, the positive cohesion energy between the CNCs-capped AgNPs-modified PVDF membrane and thermophilic bacterial foulant was + 63.2 mJ/m2, distinctly proving reduced fouling. The findings were supported by 5.5 % flux decay of the modified membrane compared to 79.3 % flux decay of virgin PVDF membrane. This suggested a long-term membrane integrity in thermophilic bacterial contaminated feed solutions during the MD water desalination.

Correlation Between Antimicrobial Structural Classes and Membrane Partitioning: Role of Emerging Lipid Packing Defects.

In this study, a combination of bioinformatics and molecular dynamics simulations is employed to investigate the partitioning behavior of different classes of antimicrobial peptides (AMPs) into model membranes. The main objective is to identify any correlations between the structural characteristics of AMPs and their membrane identification and early-stage partitioning mechanisms. The simulation results reveal distinct membrane interactions among the various structural classes of AMPs, particularly in relation to the generation and subsequent interaction with lipid packing defects. Notably, AMPs with a structure-less coil conformation generate a higher number of deep and shallow defects, which are larger in size compared to other classes of AMPs. AMPs with helical component demonstrated the deepest insertion into the membrane. On the other hand, AMPs with a significant percentage of beta sheets tend to adsorb onto the membrane surface, suggesting a potentially distinct partitioning mechanism attributed to their structural rigidity. These findings highlight the diverse membrane interactions and partitioning mechanisms exhibited by different structural classes of AMPs.

Omniphobic PTFE based Hollow Fiber Membrane with ZnO Nanoparticles Deposition via Universal Spray Technique

This investigation aimed to enhance the hydrophobicity of a polytetrafluoroethylene (PTFE) hollow fiber membrane, transforming it into an omniphobic surface. This was achieved by coating the membrane with a mixture of zinc oxide nanoparticles (ZnO-NPs) and polyvinylidene fluoride-cohexafluoropropylene (PVDF-HFP) using the universal spray technique. The membrane's morphology and performance were evaluated based on the number of spray cycles, which influenced the coating thickness on the membrane surface. The spraying process was varied up to 4 cycles to determine the membrane with the most effective deposition of ZnO NPs in terms of water contact angle and liquid entry pressure (LEPw). Results indicated that the membrane spray-coated up to 4 cycles, denoted as PTFE-4, exhibited a rough hierarchical re-entrant morphology, imparting omniphobic characteristics. The optimized membrane demonstrated a high water contact angle of 170° and a liquid entry pressure of 2.6 bar. Fourier-transform infrared (FTIR) and energy dispersive analysis of X-rays (EDX) confirmed the successful chemical integration of ZnO NPs onto the commercial membrane. This research holds significance for the future of membrane distillation in treating wastewater containing low surface tension pollutants.

Covalent Organic Framework-Coated Polyimide Ion-Track-Etched Separator with High Thermal Stability for Developing Lithium-Ion Batteries with Long Lifespans.

Separators play a crucial role in inhibiting thermal runaway in lithium-ion batteries (LIBs). In this study, the doctor blade coating method and heavy-ion track etching technology were used to prepare a polyimide-based covalent organic framework (PI_COF) separator with excellent thermal stability and a long cycle life. Specifically, COF300 was simply coated on the surface of a polyimide-based track-etched membrane (PI_TEM) with straight through holes, which provided a rigid framework and high-temperature stability at 300 °C. These features were conducive to inhibiting thermal runaway, while porous COF300 with large holes increased the wettability of the electrolyte, facilitating lithium-ion migration and suppression of lithium dendrite growth; consequently, LIBs with an excellent cycling performance and a high rate capacity were obtained. The cell with the PI_COF separator delivered a high capacity of 90.0 mA h g-1 after 1000 cycles. The PI_COF separator with high thermal stability exhibited a long cycle life in LIBs. These features are beneficial for improving the safety characteristics of LIBs as well as for accelerating the practical application process of the PI_COF separator.

Engineering polyvinylidene fluoride membranes using charge tunable dendrimer polyamidoamine to enable microporous membranes for protein separation

Dendrimers are structurally precise molecules, whose peripheral layer provides ample sites for anchoring functional groups of different charges and charge densities. This characteristic renders them capability of providing numerous target functional groups on the surface of filtration membranes when modified by dendrimers. Consequently, there has been a growing interest in dendrimer-modified membranes. In this study, we investigated the engineering of polyvinylidene fluoride (PVDF) membranes using polyamidoamine (PAMAM) dendrimers anchoring different functional groups to tune the charges and charge density of membranes to enable microporous membranes for separation of charged macromolecules. PVDF membranes were functionalized by grafting PAMAM-G3.0 (generation 3) dendrimers with amine groups onto their surfaces and internal surfaces of membrane pores. Subsequently, the peripheral functional groups of dendrimers on the membranes were replaced by carboxyl groups, quaternary ammonium groups, or sulfonic acid groups for charges of different nature and densities. Surface chemical properties, electrical properties, and morphology were characterized using various techniques, including attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and surface zeta potential measurement. The filtration performance of both PVDF and modified membranes was evaluated using polyethylene oxide (PEO), polyacrylic acid (PAA), and whey protein filtration. Among the modified membranes, the G3PA membranes, with carboxyl functional groups, exhibited the most effective whey protein separation performance. The whey protein rejection and permeate flux of the G3PA membranes were 79 % and 30.3 LMH, respectively. As a comparison, the whey protein rejection and permeate flux of the pristine PVDF membranes were 58.9 % and 15.3 LMH, respectively.