Macroporous Membranes Research Articles

Fabrication of porous beta-cyclodextrin functionalized PVDF/Fe–MOF mixed matrix membrane for enhanced ciprofloxacin removal

Herein, we demonstrate the synthesis of beta-cyclodextrin (β–CD) functionalized polyvinylidene fluoride (PVDF) and iron-based metal-organic framework (Fe–MOF) mixed matrix membrane (MMM) for the enhanced removal of ciprofloxacin (CIP) from water. The membranes were prepared using the phase inversion technique with PVDF as the polymer matrix, Fe–MOF as the filler, and polyvinylpyrrolidone (PVP) as the porogen. The optimized MMM with 7% wt. Fe–MOF exhibited excellent performance with 87.6% removal efficiency. Moreover, the maximum adsorption capacity was 6.43 mg g–1. The β–CD functionalization improved the MMM hydrophilicity exhibited by the water contact angle (WCA) analysis (WCA = 55°). Furthermore, excellent adsorption performance can be attributed to the large Fe–MOF specific surface area (682.5 m2 g–1), the high porosity (77%), and the average pore diameter (395 nm) of the membrane. The inclusion of PVP (1% wt.) enhanced the porous nature of the MMM and, consequently, the adsorption performance for CIP. Notably, the hydrophilic and macroporous membrane showed good reusability with over 70% removal efficiency after five sequential adsorption–desorption cycles. The insights from this study suggest that the PMC–7 membrane can be an excellent candidate for the remediation of organic contaminants from aquatic environments.

Improving waterproof-breathable capability of degradable macroporous film/hemp hydroentangled nonwovens composite membranes by porous structure and surface wettability modification

Due to recent serious COVID-19 pandemic, medical protective materials with outstanding microbial barrier and liquid barrier property have attracted much attention. However, the crucial issue of improving the waterproof-breathable capability and degradable properties of medical protective material is still challenging. In this research, poly(butyleneadipate-co-terephthalate) (PBAT)/hemp@silica-polyvinylsilsesquioxane (SiO2-PVSQ) composite membranes with good moisture permeability and waterproof property were fabricated. Firstly, hemp and cotton fibers were mixed and hemp/cotton hydroentangled nonwovens were produced to endow the membranes with outstanding water vapor penetration and mechanical properties. Then, degradable PBAT macroporous membranes were prepared by non-solvent induced phase separation (NIPS) method, and combined with hemp/cotton hydroentangled nonwovens to endow the composite membranes with waterproof property. Finally, SiO2 particles were hydrophobically modified by vinyltrimethoxysilane (VTMOS) and grafted on the surface of PBAT/hemp composite membranes. The waterproof property of composite membranes was further improved by hierarchical rough structure and low surface tension hydrophobic groups on the membrane surface. The prepared PBAT/hemp@SiO2-PVSQ composite membranes showed excellent tensile strength with high moisture permeability, good waterproof and water contact angle of 139.5°, indicating promising candidates for the new generation comfort and degradable medical protective textiles.

Growth of the Cycle Life and Rate Capability of LIB Silicon Anodes Based on Macroporous Membranes.

This work investigated the possibility of increasing the cycle life and rate capability of silicon anodes, made of macroporous membranes, by adding fluoroethylene carbonate (FEC) to the complex commercial electrolyte. It was found that FEC leads to a decrease in the degradation rate; for a sample without FEC addition, the discharge capacity at the level of Qdch = 1000 mAh/g remained unchanged for 220 cycles and the same sample with 3% FEC added to the electrolyte remained unchanged for over 600 cycles. FEC also improves the power characteristics of the anodes by 5-18%. Studies of impedance hodographs showed that in both electrolytes (with 0% and 3% FEC, respectively) the charge transfer resistance grows with an increasing number of cycles, while Solid Electrolyte Interphase (SEI) parameters, such as its resistance and capacitance, show little change. However, the addition of FEC more than halves the overall system impedance and reduces the resistance of the liquid electrolyte and all current carrying parts as well as the SEI film and charge transfer resistances.

A poly(amidoxime)-modified MOF macroporous membrane for high-efficient uranium extraction from seawater

Abstract Although metal–organic frameworks (MOFs) own excellent uranium adsorption capacity but are still difficult to conveniently extract uranium from seawater due to the discrete powder state. In this study, a new MOF-based macroporous membrane has been explored, which can high-efficiently extract uranium through continuously filtering seawater. Through modifying the UiO-66 with poly(amidoxime) (PAO), it can disperse well in a N,N-dimethylformamide solution of graphene oxide and cotton fibers. Then, the as-prepared super-hydrophilic MOF-based macroporous membrane can be fabricated after simple suction filtration. Compared with nonmodified MOFs, this UiO-66@PAO can be dispersed uniformly in the membrane because it can stabilize well in the solution, which have largely enhanced uranium adsorbing capacity owing to the modified PAO. Last but not least, different from powder MOFs, this UiO-66@PAO membrane provides the convenient and continuously uranium adsorbing process. As a consequence, the uranium extraction capacity of this membrane can reach 579 mg·g−1 in 32 ppm U-added simulated seawater for only 24 h. Most importantly, this UiO-66@PAO membrane (100 mg) can remove 80.6% uranyl ions from 5 L seawater after 50 filtering cycles. This study provides a universal method to design and fabricate a new MOF-based adsorbent for high-efficient uranium recovery from seawater.

Recycle coal fly ash for preparing tubular ceramic membranes applied in transport membrane condenser

Water recovery from flue gas with transport membrane condenser (TMC) has gained much attention in recent years. It has great potential in water conservation and air pollution control. However, effects of porosity and pore size variation of macroporous membranes on TMC application have not been revealed. Coal fly ash (CFA) is used as main raw material to prepare various tubular macroporous ceramic membranes for TMC application. The extrusion method is adopted. Characterization of membranes are conducted for structural parameters evaluation. Prepared membranes were used for TMC application to experimentally study the water and heat recovery performance. Influences of temperatures and flowrates of flue gas and cooling water on recovery performance have been investigated. Increasing cooling water flowrate and flue gas temperature, as well as decreasing cooling water temperature can promote water and heat recovery performance of TMC. The highest water recovery efficiency is 79.21%. Although membrane pore size increasing improves water and recovery, the average pore size should be less than 2 μm to avoid transmembrane gas permeation. Results indicate that CFA membrane is suitable for TMC application and provides investment reduction.

Application of 1.0-μm macroporous hollow fiber membrane for prevention of membrane fouling and enhancement of permeate flux in algae harvesting

We challenged to introduce macroporous membrane for algae harvesting with a permeate flux of 166 L m−2 d−1 to achieve significant reduction of harvesting cost. Analysis of the dissolved organic matter in the supernatant of cultures of the green alga, Coccomyxa sp. strain Obi, detected a scarce amount of hydrophilic macromolecules, which can be membrane fouling agents. The continuous filtration with a macroporous membrane achieved a 30-fold concentration of algal cells from 800 mg biomass/L to 24,000 mg biomass/L with a harvesting efficiency of 100%. Most of previous studies on the membrane filtration for harvesting microalgae merely utilized microfiltration membranes developed for wastewater treatment. However, the use of a membrane of the largest pore size that microalgal cells cannot seep through will result in slower fouling, higher flux, and a great reduction of harvesting cost.

Chitosan/gelatin/PVA membranes for mammalian cell culture

The study aims to fabricate and characterize biodegradable membranes, comprising of chitosan/gelatin/ polyvinyl alcohol (PVA) terpolymers to replace the use of synthetic membranes for mammalian cell culture. Blends of chitosan, PVA and gelatin, in varying ratios, were solution cast to fabricate macroporous membranes. The membranes were characterised using Field Emission Scanning Electron Microscopy (FE-SEM) and Fourier Transform Infrared Spectroscopy (FTIR). The influence of different ratios of polymers on membrane properties, such as in vitro degradation, apparent density and water contact angle were investigated. The biocompatibility of the membranes was confirmed using the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. Further, a mammalian skin keratinocyte (HaCat) cell line was employed to ascertain cellular adhesion and proliferation on the membranes. The developed macroporous membranes supported the adhesion and growth of mammalian cells and were thus found to be suitable and sustainable alternatives to synthetic membranes for in vitro cell culture.

Hierarchical porous cellulose membrane tethered with SiO2 nanoparticles as a sorbent’s platform for micropollutants removal

Micropollutants (MPs) present in water have shown increasing threat on the ecosystem. Membrane adsorption is playing an increasingly important role on the MPs removal but the synthesis of adsorptive membrane of high capacity remains challenging. This work proposed a strategy of grafting mesoporous nanoparticles onto macroporous membranes to prepare sorbents for MPs removal. The SiO2 nanoparticles with thiol groups (SiO2-SH) was introduced onto the RC membrane surface to prepare RC-SH membrane with a hierarchical porous structure. Specific adsorptive ligands, including itaconic acid (IA) or glycidol, was then immobilized to the RC-SH membrane surface via the thio-ene and thio-epoxy chemistry towards RC-IA and RC-PG membranes. Three kinds of adsorption membranes were obtained and their physical–chemical structure and morphologies were characterized by ATR-FTIR, XPS, SEM and BET. The grafted nanoparticles have been demonstrated to increase the surface area of the adsorptive membranes. The obtained adsorptive membranes, RC-SH, RC-IA, and RC-PG, show good adsorptive capacity for Hg(II) (179.0 mg/g) , Pb(II) (140.1 mg/g), and boron (2.55 mmol/g). The adsorption isotherm and kinetics fit well with Langmuir model and pseudo-second-order kinetic model, respectively. This work provides a universal method tethering porous nanoparticles onto the macroporous membrane surface for improved functionality capacity.

Efficient elimination of chlorpyrifos via tailored macroporous membrane based on Al-MOF

Chlorpyrifos as one of organophosphorus pesticides, is easily absorbed by human skin and dangerously causing inhibition of acetylcholinesterase that is essentially required for transporting nerve impulse. Therefore, the current approach focused on the adsorptive removal of Chlorpyrifos using superior adsorptive membrane composed of Al-metal organic framework@cellulose acetate (MIL-53-NH2@CA). The membrane was uniquely synthesized in two sequential steps; firstly, preparation of porous CA membrane and consequently, incorporation of MIL-53-NH2 within the synthesized porous CA membrane. Procedure was performed to impregnate various ratios of MIL-53-NH2 (20–60%) within the porous CA membrane. Micro-particles MIL-53-NH2 was successively immobilized within the membrane, while, the pore diameter was ranged in 124.5–485.6 nm. Adsorptive removal of chlorpyrifos through the prepared membrane was corresponded to Langmuir isotherm and pseudo-second ordered reaction. The maximum adsorptive capacity was observably increased from 160.36 mg/g for CA to 207.62–356.34 mg/g for MIL-53-NH2@CA. Impregnation of 60% MIL-53-NH2 resulted in fastening of the adsorptive removal rate of chlorpyrifos by factor of 2.2. The employed membrane exhibited very good recoverability and the adsorptive compatibility was diminished by 27.9% after five reuses. The prepared MIL-53-NH2@CA membrane can be promisingly applicable in the superior removal of pesticides and in various environmental applications.

Co-continuous structural effect of size-controlled macro-porous glass membrane on extracellular vesicle collection for the analysis of miRNA

Recent studies have shown that extracellular vesicles (EVs) can be utilized as appropriate and highly specific biomarkers in liquid biopsy for the diagnosis and prognosis of serious illness. However, there are few methods that can collect and isolate miRNA in EVs simply, quickly and efficiently using general equipment such as a normal centrifuge. In this paper, we developed an advanced glass membrane column (AGC) device incorporating a size-controlled macro-porous glass (MPG) membrane with a co-continuous structure to overcome the limitations of conventional EV collection and miRNA extraction from the EVs. The size of macro-pores in the MPG membrane could be accurately controlled by changing the heating temperature and time on the basis of spinodal decomposition of B2O3, Na2O, and SiO2 in phase separation. The AGC device with an MPG membrane could collect the EVs simply and quickly (< 10 min) from cell culture supernatant, serum and urine. This AGC device could extract miRNA from the EVs captured in the MPG membrane with high efficiency when combined with a miRNA extraction solution. We suggest that the AGC device with an MPG membrane can be useful for the diagnosis and prognosis of serious illness using of EVs in various kinds of body fluids.

Superhydrophobic PVDF/micro fibrillated cellulose membrane for membrane distillation crystallization of struvite

Phosphate recovery is essential due to the depletion of phosphate resources and the phosphate loss by surface run-off. Membrane distillation crystallization (MDC) system with macroporous membrane provides a large interfacial surface for water removal at low temperature and phosphate concentration for crystal growth in the phosphate recovery strategy. However, the water vapour removal rate is limited by the membrane porosity and pore size. Membrane wetting and fouling on the hydrophobic membrane surface further reduce phosphate recovery in the long operation. In this work, polyvinylidene fluoride (PVDF) membrane was enhanced by adding micro fibrillated cellulose (MFC) filler to enhance phosphate recovery through struvite precipitation in MDC. The membrane was further modified by non-fluorinated silane (hexadecyltrimethoxysilane or octadecyltrichlorosilane) after phase inversion to attain superhydrophobicity. MFC promoted pore growth and porosity creation in PVDF/MFC membrane as the solvent-non-solvent exchange rate was boosted during phase inversion. In silane modification, abundant moieties of MFC further promoted vertical polymerization for creating superhydrophobic surface. The PVDF/MFC membrane modified with octadecyltrichlorosilane obtained the highest water contact angle of 154.4°, liquid entry pressure of 1.51 bar, relatively large pore size of 0.40 μm and satisfactory porosity of 45.1%, resulting in the stable permeate flux in MDC. The needle-like struvite crystals formed after pH adjustment and the modified membrane surface was not fouled even after 24 h of operation.

Preparation of Temperature-Sensitive Inverse Macroporous Membranes Using Silica Spheres as a Template

The temperature-sensitive inverse macroporous membranes containing thermo-responsive poly (N-isopropylacrylamide) (PNIPAM) were prepared by a template of silica microspheres. The inverse membranes were characterized by SEM, FTIR and contact angle measurements. The PNIPAM containing inverse macroporous membranes had different pore diameters at different temperatures and could be used for separation. The conductivity was measured to characterize the temperature-responsive behavior and permeability of this inverse macroporous membranes. Due to variable pore sizes, the membranes exhibited specific temperature-responsive permeability. This strategy presented here is a simple, low-cost, and controllable alternative for fluidic applications, such as the separation of particles.

Enabling directional ion transport over graphene electrode surfaces for kilohertz electrochemical capacitors

The filtering capacitor is an electrochemical energy storage device, which can realize signal stabilization from alternating current to direct current in the modern electronic circuits. Traditional filtering capacitor, an aluminum electrolytic capacitor is usually limited by the bulky and rigid configuration. The graphene-based electrochemical capacitor with a fast frequency response has the potential to be the next-generation filtering capacitor. Kilohertz electrochemical capacitor with alternating current line-filtering performance requires the microstructural engineering of graphene electrodes to facilitate effective electrolyte ion permeation. Vertically-oriented graphene electrode-based electrochemical capacitor by microstructural engineering provides a significant solution for improving the filtering performance, but the underlying mechanism by which the vertical orientation endows graphene electrodes with the fast frequency response is still not clear. Therefore, a fundamental understanding of this mechanism must be developed and improved to ensure the design of superior kilohertz electrochemical capacitors for effective filtering. Here, a vertically-oriented graphene macroporous membrane is prepared to enable directional ion transport over the electrode surface at high frequencies, which is demonstrated by all of the electrochemical analysis, line scanning, schematic illustration and finite element analysis simulation results. Compared with those based on conventional horizontally-oriented and unordered graphene macroporous membrane electrodes, the vertically-oriented electrode-based electrochemical capacitor exhibits excellent filtering performance. Furthermore, it can convert arbitrary alternating current waveforms to straight signals. This work advances the understanding of the mechanism underlying the kilohertz frequency response and enables directional ion transport over the surface of vertically-oriented graphene electrodes, providing new insight into the search for future kilohertz filtering capacitors.

Numerical investigation on condensation mode of the transport membrane condenser

Transport membrane condenser is a novel device for capturing water vapor from wet flue gas, which is composed of porous ceramic membranes. The capillary condensation is once considered as the water vapor capture mechanism of transport membrane condenser. Recently, a few scholars have discovered that transport membrane condenser composed of macroporous ceramic membranes can capture more water vapor. Since the capillary condensation cannot occur in the pores of the macroporous membrane, water vapor is believed to condense on the surface of the macroporous membrane. However, there is currently no comparative study of the two condensation mechanisms. In this paper, based on the transport membrane condenser pilot scale testing platform built in a coal-fired power plant, a numerical model is established to discuss the effects of different condensation mechanisms on the performance of transport membrane condenser. Furthermore, the model is extended to the application engineering. The results show that water vapor captured by transport membrane condenser is 25–45 t/h in a 330 MW coal-fired power plant, which can reduce the amount of makeup water to some extent. The numerical model also can be used to calculate the number of ceramic membranes for engineering design.

RETRACTED: Macroporous photothermal bilayer evaporator for highly efficient and self-cleaning solar desalination

Abstract Solar steam generation is a promising technology for harvesting solar energy to purify seawater and wastewater. State-of-the-art technologies have struggled to achieve sufficient solar evaporation rate and antifouling property simultaneously. In addition, the antifouling strategies based on flow dynamics need to be established to develop more efficient membrane designs. Here we propose a new superhydrophilic thermally-insulated macroporous membrane (STIMM) composed of carbonized sucrose and polydimethylsiloxane as an efficient solar evaporator. The converted solar energy is fully utilized for evaporation by the aid of the coupled effects of superhydrophilicity and heat localization. STIMM achieves a high evaporation rate of 2.045 kg/m2/h even at its macropore size under 1 sun irradiation, overcoming the previous trend limit. The macropores of STIMM enable self-cleaning with a 93.1% salt rejection rate. The high evaporation rate and geometrical traits of STIMM generate strong convective flows to dynamically reject salt. The solar desalination system based on STIMM stably produces a practically high amount of purified water with a production rate of 24.9–30.6 L/m2/day. Our proposed STIMM demonstrates a new paradigm for facile desalination systems that are low cost, energy efficient, and self-cleaning under natural environmental condition.

Ultrarobust and Biomimetic Hierarchically Macroporous Ceramic Membrane for Oil-Water Separation Templated by Emulsion-Assisted Self-Assembly Method.

Reported herein is a novel ultrarobust and biomimetic hierarchically macroporous ceramic membrane that can achieve a high efficiency of up to 99.98% for oil-water separation, while the efficiency remains nearly unchanged even after 10 rounds of use and storage for up to 4 months. The macroporous ceramic membrane is prepared by combining surface hydrophobic coating with an emulsion-assisted template self-assembly of the modified Al2O3 ceramic powder. The as-prepared ceramic membrane is a lightweight material with high strength because the relative density is only ∼1.02 g/cm3; the compressive strength of the as-prepared ceramic membrane is expected to be 15-fold higher than that of the sample prepared using the traditional solid template approach even at a higher porosity due to the principle of self-assembly of Al2O3 particles. It is the mechanism of self-assembly that has broken the traditional principle in ceramic preparation that leads to a perfectly dense packing structure. Moreover, the ceramic membrane maintained excellent oil-water separation efficiency, because of which even after its top layer was damaged by sand impingement, superfine particles could be separated using our macroporous membrane due to the featured interconnected pore structure. We anticipate that this example of the combination of a superwettability theory and a traditional ceramic material can provide an important application direction of advanced oil-water separation techniques.

Constructing 3D optical absorption holes by stacking macroporous membrane for highly efficient solar steam generation

Abstract In recent years, solar steam generation technology has received widespread attention in seawater desalination, but existence of some problems, namely difficulty in salt cleaning and high expense, limited it further development. Herein, in this work, a carbon black gauze membrane (CBGM), with low cost and easy to clean properties, was developed by stacking macroporous membrane to construct 3D optical absorption holes, which were favorable to an enhancement of light absorption. The 4-layer CBGM evaporation device displayed an improved solar steam generation performance, which was corresponded to the evaporation rate of 1.60 kg m−2h−1 and the evaporation efficiency of 96.0% under 1 kW m−2, respectively. Likewise, the 4-layer CBGM evaporation device exhibited superior recyclability, long life and excellent desalination performance, as well as was able to effectively produce potable freshwater from seawater. Consequently, the CBGM was regarded as a promising alternative for high-efficiency solar-driven seawater desalination.

Porous Carbon Membrane-Supported Atomically Dispersed Pyrrole-Type FeN4 as Active Sites for Electrochemical Hydrazine Oxidation Reaction.

The rational design of catalytically active sites in porous materials is essential in electrocatalysis. Herein, atomically dispersed Fe-Nx sites supported by hierarchically porous carbon membranes are designed to electrocatalyze the hydrazine oxidation reaction (HzOR), one of the key techniques in electrochemical nitrogen transformation. The high intrinsic catalytic activity of the Fe-Nx single-atom catalyst together with the uniquely mixed micro-/macroporous membrane support positions such an electrode among the best-known heteroatom-based carbon anodes for hydrazine fuel cells. Combined with advanced characterization techniques, electrochemical probe experiments, and density functional theory calculation, the pyrrole-type FeN4 structure is identified as the real catalytic site in HzOR.

Hollow molybdenum oxide-graphene oxide spheres as a binder-free electrocatalyst membrane with enhanced hydrogen evolution efficiency

To make electrochemical water splitting to produce hydrogen realistic, earth-abundant and low-cost electrocatalysts need to be developed. In this work, we demonstrate a facile strategy to synthesize decorated molybdenum oxide (MoO2) nanoparticles on graphene oxide (GO) layers. With GO sheets, hollow spheres of MoO2-G are formed. Incorporation of the MoO2-G balls into a cryogel, subsequent freeze-drying and carbonization, gives a conducting MoO2-G macroporous membrane. The hybrid membrane exhibits excellent performance for HER with a Tafel slope of 52 mV dec-1 at an onset potential of −100 mV and high stability, reflected in the stable cathodic current over 23 h. of operation.

Life-Cycle Assessment of Gingko-Wood Three-Dimensional Membrane for Wastewater Treatment.

Forest is one of nature’s most generous gifts to human beings, providing materials and shelters for all living beings with over 30% global land coverage. Apart from being sustainable, biodegradable, and renewable, wood is also extremely fascinating from the application aspect, with numerous advantages including hierarchical and macroporous structure, excellent mechanical performance, and versatile chemistry. The macroporous structure of wood is comprised of numerous long, partially aligned channels along the growth direction. This structure is suitable for a range of emerging applications, especially as a separation/membrane material. In this research, the potentiality of Gingko biloba (Gb) wood in the remediation of wastewater, contaminated with methylene blue (MB), a dye found in the industrial waters, was investigated. We report a macroporous, three-dimensional (3D) Gb-wood membrane decorated with palladium nanoparticles (Pd NPs) for efficient wastewater treatment. The efficiency of the Pd NPs/Gb-wood membrane to remove MB from a flowing aqueous solution was demonstrated. The wastewater treatment rate of the 3D Pd NPs/Gb-wood membrane can reach 0.5 L/min, with a high MB removal efficiency (>99.9%). The 3D Gb-wood macroporous membrane with partially aligned channels exhibits promising results for water treatment and is applicable for an even wider range of separation applications. In addition, the benefit of this 3D-wood membrane system for wastewater treatment was evaluated against the potential impacts on the environment and human health by employing the life-cycle assessment (LCA) approach. The LCA was carried out using the Gabi-education version with the gate-to-grave approach, including industrial wastewater, 3D-wood membrane, and electricity consumption using CML (Centrum VoorMilieukunde Leiden). From the LCA, it can be observed that wastewater filtration using this membrane exhibited a better environmental footprint due to the improved performance of the membrane in treating a higher volume of the permeate. Therefore, this filtration system had outweighed the additional environmental impact of the wastewater treatment process. The energy demand was identified as the main environmental hotspot in the LCA analysis. The analysis revealed that the energy source for electricity generation had a significant influence on the overall sustainability of this system. Additionally, the wood itself, a naturally abundant and eco-friendly material, presented zero environmental hazard to the environment during the filtration process. The experimental and environmental impact results indicate that Gb-wood can be employed as a natural and eco-friendly adsorbent material for the removal of waste from aqueous solutions.