Development Of Membrane Materials Research Articles

P(MA-AMPS)/PVA@SiO2 hybrid hydrogel coated stainless steel mesh for effective separation of stabilized oil-in-water emulsions under gravity

The superhydrophilic/underwater superhydrophobic membrane offers unique advantages in effectively separating oily wastewater. However, the development of membrane materials that can efficiently separate emulsions only under gravity is still a challenge. A crosslinked network copolymer P(MA-AMPS) was synthesized by radical polymerization of N, n-methylenebisacrylamide (MBA), methacrylamide (MA) and 2-acrylamide-2-methylpropanesulfonic acid (AMPS) initiated by potassium persulfate. Then polyvinyl alcohol (PVA) and nano-SiO2 were inserted to the crosslinked polymer system in order to prepare a P(MA-AMPS)/PVA@SiO2 hybrid hydrogel. The hybrid hydrogel can be sprayed on the surface of stainless steel mesh (SSM) by a simple spraying method, so as to achieve superhydrophilicity/underwater superoleophobicity. The oil-water emulsion permeation flux reached more than 352.94 L·m−2·h−1, while xhibiting a more than 99.5 % separation efficiency under gravity. The anti-fouling tests demonstrated that the membrane exhibited outstanding anti-fouling performance. Moreover, the combination of stable semi-interpenetrating networks and nanoparticles made the membrane exhibit excellent stability and durable separation ability in complex physicochemical environments.

Design of photocatalytic self-cleaning poly (arylene ether nitrile)/nitrogen-doped Bi2O2CO3 composite membrane for emulsified oily wastewater purification

Membrane separation technique offers unique advantages for treating the emulsified oily wastewater with the oil droplet diameter less than 20 µm. However, the complicated membrane fouling originating from oils and soluble matters pose the huge challenges to membrane separation technique, which has stimulated the development of advanced membrane materials. Herein, we reported the photocatalytic and super-wetting poly (arylene ether nitrile) (PEN) fibrous composite membrane with high permeability and enhanced anti-fouling ability. The nitrogen-doped Bi2O2CO3 (N-Bi2O2CO3) was prepared by low-temperature chemical modification method and modified by dopamine (DA)-polyethyleneimine (PEI), which was further self-assembled on porous PEN support backbone. The hydrophilicity provided by the cross-linking reaction between PDA and PEI and micro-/nano- rough surface constructed by the flower-like N-Bi2O2CO3 contributed to the super wetting properties (WCA=0°, UOCA>150°), which imparted the membrane with ultra-low oil adhesion. In particular, the arrangement of flower-like N-Bi2O2CO3 effectively regulated the water channel of membrane, further increasing the permeate flux. Therefore, the fibrous composite membranes showed superior separation flux (632.79–762.81 L·m−2·h−1) and separation efficiency (>99.16%) for various oil-in-water emulsions, even under harsh conditions (90 ℃ and 2 M NaCl solution). More importantly, the N-Bi2O2CO3 rendered the membrane excellent degradation rates for various dyes (MO: 95.53%, MeB: 96.40%, CV: 96.45%, CR: 87.14%), achieving favorable photocatalytic self-cleaning ability. This work opens an alternative strategy to fabricate fibrous composite membrane with synergistically enhanced anti-fouling for the treating complicated emulsified oily wastewater in petrochemical industry.

Selectivity and permeability of gas separation in SILMs: Effect of collapsed structure

In this work, the influence of the intramembrane structure of SILMs on gas separation was demonstrated by molecular dynamics simulations. The five morphological characteristics of separation membranes bring different separation effects. For the selection process, interfacial characteristics have a significant effect on the selectivity by the analysis of density and energy barrier. The difference in the blocking effect on CO2 is the key to the separation. For the permeation process, the analysis of free volume and interaction energy revealed that the residence time and penetration of gas molecules in membranes are sensitive to distribution characteristics of ionic liquids. Lastly, the interaction energy and pressure difference were analyzed to reveal the influence of the membrane structure on the persistence of separation and flow interruption. This work can provide theoretical support for the high efficiency control of membrane separation and the development of two-dimensional membrane materials.

Progress on Improved Fouling Resistance-Nanofibrous Membrane for Membrane Distillation: A Mini-Review.

Nanofibrous membranes for membrane distillation (MD) have demonstrated promising results in treating various water and wastewater streams. Significant progress has been made in recent decades because of the development of sophisticated membrane materials, such as superhydrophobic, omniphobic and Janus membranes. However, fouling and wetting remain crucial issues for long-term operation. This mini-review summarizes ideas as well as their limitations in understanding the fouling in membrane distillation, comprising organic, inorganic and biofouling. This review also provides progress in developing antifouling nanofibrous membranes for membrane distillation and ongoing modifications on nanofiber membranes for improved membrane distillation performance. Lastly, challenges and future ways to develop antifouling nanofiber membranes for MD application have been systematically elaborated. The present mini-review will interest scientists and engineers searching for the progress in MD development and its solutions to the MD fouling issues.

Recent advances in heavy metal removal by thin film nanocomposite membrane

Abstract Rapid industrialization has become one of the root causes of environmental problems, particularly heavy metal pollution. Numerous methods, including chemical precipitation and ion exchange, have been used to remove heavy metal ions from aqueous solutions, but all of them have drawbacks, such as low metal removal effectiveness, significant reagent loss, excessive energy use, and the need for further development of the current techniques. Membrane-based technologies such as reverse osmosis (RO) and nanofiltration (NF) are gaining popularity in the removal of heavy metals due to their high rejection and low formation of secondary pollutants. Among the methods under consideration, the membrane-based approach holds the most promise for wastewater treatment with a focus on heavy metal ion removal due to its ease of manufacture, superior qualities, and increased separation effectiveness. Since membrane performance is typically hampered by fouling, low permeability, and significant contaminant permeation when compared to strict selectivity criteria, the development of novel membrane materials has emerged as an important area of research for academia, industry, and national laboratories. We have therefore reviewed previous initiatives and technological developments in order to achieve more effective heavy metal removal and recovery from industrial wastewater.

Insight of chitooligosaccharides diffusion within polymeric membranes using molecular dynamic simulation

The membrane separation technology with the advantage of cost-benefit, energy-efficient and ease to scale up, is promising to realize the industrialized separation of chitooligosaccharides (COS) to meet the industrial demands. While COS with different degree of polymerization (DP) have similar molecular size and physicochemical properties which hinders the precise separation of COS by the commercial membranes. Herein, molecular dynamics simulations were performed to explore the diffusion behavior of COS within PEEK, PES, PSF, PVDF and PPTA membranes, to provide a theoretical basis for the screening and development of novel polymeric membrane materials for precise separation of COS. The interaction among the COS, water, and the polymer chains were investigated by calculating diffusion coefficient, interaction energy, hydrogen bonding and radial distribution function. And the diffusion process of the COS within the five polymeric membranes was investigated. Results showed that the diffusion behavior of the COS within the polymeric membranes depended on the interactions among the polymer chain, COS and water, which determined by the DP of COS and the structural properties of the polymer chain. Compared with other four kinds of materials, the interaction between PPTA chain and COS molecules repressed the decline trend of the difference between the diffusion coefficients of COS with adjacent DP as the DP of COS increased, making PPTA the most beneficial to the precise separation of the COS with different DP.

Novel proton-conducting materials based on a polyethylene terephthalate track-etched membrane modified with an N, P-containing ionic liquid

The development of novel membrane materials for hydrogen fuel cells, a promising environmentally friendly technology, represents a relevant research task. In this work, we propose an approach to creating proton-conducting membranes from an industrial polyethylene terephthalate (PET) dielectric track-etched film. An N, P-containing ionic liquid was used as a modifying agent, whose polymerization was carried out directly in the PET membrane pores. The ionic liquid was obtained using a novel approach to the directed synthesis of organophosphorus compounds from elemental phosphorus via the Trofimov-Gusarova reaction developed at the A.E. Favorsky Institute of Chemistry of the Siberian Branch of the Russian Academy of Sciences. The ionic liquid properties were characterized by NMR and IR spectroscopy. The application of the obtained N, P-containing ionic liquid onto a PET membrane was shown to yield a material exhibiting the required mechanical parameters for operation as proton-conducting membranes. The novel proton-conducting materials demonstrate a high proton conductivity of 77.76 mS·cm-1 at 353 K. The obtained proton-conducting membranes seem promising for application in hydrogen fuel cells, thus contributing to the development of effective alternative energy sources.

Cellulose nanocrystals-microfibrils biocomposite with improved membrane performance

This study investigates eco-friendly membrane biocomposites derived from biomass, utilizing cellulose microfibrils (CMF) as the main membrane material. Cellulose nanocrystals (CNC), isolated from rice husk, were added as reinforcing fillers in CMF flat sheet membranes. CNC with concentrations of 0%, 10%, 20%, and 30% were employed. Scanning electron microscopy images revealed that CNC influenced the surface profile and the pore structure of the membranes, reducing the porosity by 23%. The empty areas formed by CMF interaction were effectively filled by CNC. This modified membrane resulted in an increase in NaCl rejection of up to 16%. Dynamic water contact angle demonstrated the role of CNC in enhancing permeability, with a shorter spreading time of 13 min. It was also confirmed by the highest flux of 351 L/m− 2h−1 under pure water flux conditions. Mechanical properties were significantly improved, with a 125% increase in tensile strength and a modulus of 329 MPa. The distribution of CNC within the membranes filled pores and enhanced CMF interaction, facilitated by abundant hydroxyl groups in CNC. Overall, this study highlights the potential of eco-friendly membrane biocomposites derived from biomass, offering valuable insights for the development of sustainable and efficient membrane materials.

Boosting membranes for CO2 capture toward industrial decarbonization

Membrane technology for carbon capture is becoming increasingly attractive to combat the excessive greenhouse gas emitted into the atmosphere, which involves the benefits of cost-effectiveness, environmental-friendly, easy scalability, high energy efficiency, simplicity in design, etc. However, most state-of-the-art membrane materials suffer from either low CO2 permeability, low selectivity towards CO2 separation, poor resistance to plasticization, or inadequate long-term stability, rendering it still challenging to be upscaled to an industrial level. Therefore, the development of advanced membrane materials as well as a reasonable design of the membrane separation process is crucial and urgent for its real-life application in the future. This account reviews the details of some recent research progress in our group on carbon capture from different scenarios including post-combustion carbon capture, biogas upgrading and natural gas sweetening and hydrogen purification. Notably, considerable efforts have been invested in the development of some novel membrane materials in our group, such as facilitated transport membranes, carbon molecular sieving membranes, mixed matrix membranes, composite membranes, and poly(ionic liquids)-based membranes. Meanwhile, some studies focusing on the techno-economic feasibility analysis of membrane technology have also demonstrated its promising application on practical carbon capture.

Hydrogen isotopic water separation in membrane distillation through BN, MoS2 and their heterostructure membranes

The development and application of nuclear energy involves a challenging process of separating H2O/HTO to treat tritium-containing radioactive wastewater (HTO). Recently graphene oxide (GO)-based membrane distillation process has shown good performance for the separation of H2O/D2O used as a laboratory model research process for H2O/HTO separation, but further development of novel membrane materials or structures for membrane distillation process to give higher permeation flux or separation factor is still desirable. Here, boron nitride (BN) and molybdenum disulfide (MoS2) were investigated as membrane materials in the type of PTFE supported membrane, and PTFE/BN membrane showed higher permeation flux than PTFE/MoS2 and PTFE/GO membrane, and higher separation factor than PTFE/GO membrane that was higher than PTFE/MoS2 membrane. Furthermore, binary PTFE/BN/GO and PTFE/MoS2/GO heterostructure composite membranes were explored. The permeation flux of PTFE/BN/GO membrane was higher than that of PTFE/MoS2/GO and PTFE/GO/GO membrane. The separation factor of PTFE/BN/GO membrane was higher than that of PTFE/GO/GO membrane, which was higher than that of PTFE/MoS2/GO membrane. These results suggest that other 2D material- or heterostructure membranes can give performance comparable with or even better than GO membrane for the separation of H2O/D2O. This can guide for further exploration of novel materials or membrane structures for membrane distillation process with higher performance to provide a solution for the treatment of tritium-containing radioactive wastewater in the nuclear energy sector.

An overview of anaerobic membrane bioreactors' evolving research statistics for treating wastewater

The purpose of this article is to give a statistical bar and pie chart representing 10 years' worth of papers on anaerobic membrane bioreactors (AnMBRs). Due to its impressive benefits over aerobic membrane bioreactors (AeMBR), which are renowned for producing biogas, having minimal sludge residuals, and having potential energy consumption, this technology has become more and more popular. Data were gathered from ScienceDirect, and each topic linked to AnMBRs degree of interest was evaluated. This study quantification has shown that there has been a rise in AnMBR technology activities, particularly during the last five years. To depict the statistical scenario, 536 articles were considered. Unsurprisingly, various types and strengths of wastewater treatment, membrane fouling, microbial community, and membrane material development have piqued the researcher's curiosity. With a concept-to-commissioning viewpoint, the general increasing trend in AnMBR research clearly demonstrates the growing appeal of the technology for more reliable and sustainable applications.

Molecular Dynamics Simulation Study of Organic Solvents Confined in PIM-1 and P84 Polyimide Membranes

Organic solvent nanofiltration (OSN) has recently proved to be a promising separation process thanks to the development of membrane materials with suitable resistance toward organic solvents. Among those materials, P84 polyimide membranes are currently the most used in OSN while PIM-1 membranes have recently attracted attention due to their high permeance in apolar solvents and alcohols. Both P84 and PIM-1 membranes have nanosized free volumes, and their separation performance is finely connected to polymer/solvent interactions. Consequently, modeling OSN membranes at the molecular scale is highly desirable in order to rationalize experimental observations and gain a deeper insight into the molecular mechanisms ruling solvent and solute permeation. A prerequisite for understanding solvent transport through OSN membranes is therefore to characterize the membrane/solvent interactions at the molecular level. For that purpose, we carried out molecular simulations of three different solvents, acetone, methanol, and toluene in contact with P84 and PIM-1 membranes. The solvent uptake by both membranes was found to be correlated to the degree of confinement of the solvent, the polymer swelling ability and polymer/solvent interactions. The translational dynamics of the solvent molecules in the PIM-1 membrane was found to be correlated with the solvent viscosity due to the relatively large pores of this membrane. That was not the case with the P84 membrane, which has a much denser structure than the PIM-1 membrane and for which it was observed that the translational dynamics of the confined solvent molecules was directly correlated to the affinity between the P84 polymer and the solvent.

A novel positively charged nanofiltration membrane stimulated by amino-functionalized MXene Ti3C2Tx for high rejection of water hardness ions

The demand to address issues such as drinking water safety and industrial fouling caused by high-hardness ions has still emphasized the development of advanced membrane materials. In this study, through a maneuverable amide-cross-linking strategy, a new positively-charged polyamide (PA) nanofiltration membrane was developed for the first time by incorporating amino-functionalized Ti3C2Tx nanoparticles (Ti3C2Tx-NH2, TN). In addition to the induced electropositivity, the hydrophilicity of the as-obtained PA-TN membrane was also elevated with a maintained nodular structure by tailoring the interfacial polymerization reaction process of piperazine (PIP) with trimesoyl chloride (TMC). Therefore, the newly developed PA-TN membrane exhibited both superhigh rejection of Ca2+ and Mg2+ over 96%, and the flux increased 2–3 times even for the salinity solutions than many similar NF membranes reported in literature. Furthermore, the enhanced long-term stability and fouling resistance of the PA-TN membrane was also validated due to its new organic-inorganic structural coupling and improved hydrophilicity. This work provides a new strategy for the preparation of organic-inorganic hybrid positively charged nanofiltration membranes for water softening treatment.

Design Strategies for Forward Osmosis Membrane Substrates with Low Structural Parameters-A Review.

This article reviews the many innovative strategies that have been developed to specifically design the support layers of forward osmosis (FO) membranes. Forward osmosis (FO) is one of the most viable separation technologies to treat hypersaline wastewater, but its successful deployment requires the development of new membrane materials beyond existing desalination membranes. Specifically, designing the FO membrane support layers requires new engineering techniques to minimize the internal concentration polarization (ICP) effects encountered in cases of FO. In this paper, we have reviewed several such techniques developed by different research groups and summarized the membrane transport properties corresponding to each approach. An important transport parameter that helps to compare the various approaches is the so-called structural parameter (S-value); a low S-value typically corresponds to low ICP. Strategies such as electrospinning, solvent casting, and hollow fiber spinning, have been developed by prior researchers-all of them aimed at lowering this S-value. We also reviewed the quantitative methods described in the literature, to evaluate the separation properties of FO membranes. Lastly, we have highlighted some key research gaps, and provided suggestions for potential strategies that researchers could adopt to enable easy comparison of FO membranes.

A Superhydrophobic Trifluoromethyl-Containing Covalent Organic Framework Membrane for Efficient Oil/Water Separation.

Oily water caused in the process of industry leads to not only the waste of resources, but also environmental pollution. Membrane separation, as a facile and efficient separation technology, has attracted widespread attention in the field of oil/water separation. The development of membrane materials with high separation performance is one of the key elements to improve separation efficiency. In this work, a superhydrophobic membrane composited with a trifluoromethyl-containing covalent organic framework (COF) is prepared, which exhibits excellent performance on separations of oil/water mixtures and water-in-oil emulsions. For different composition of oil/water mixtures, the highest flux of oil is up to 32000Lm-2 h-1 and oil/water separation efficiency is above 99%. Moreover, the high oil/water separation efficiency remains unchanged after successive cycles. This work provides a feasible scheme for the design of high-efficiency oil/water separation membranes.

Status and Trends of Membrane Technology for Wastewater Treatment: A Patent Analysis

Global access to clean water and sanitation has been broadly discussed in the context of the Sustainable Development Goals adopted by the United Nations. In this context, membrane technology has been increasingly applied with great success in wastewater treatment. Considering the relevance of patent information for understanding the current status and future trends of technologies, the patent filings on membrane technology for wastewater treatment in the period from 2011 to 2019 were analyzed. This study comprised a global analysis, aimed at determining the most general aspects, and a qualitative analysis, which consisted of a careful reading of the documents to assess technological statuses and trends. From a total of 7303 patent documents found on the topic, 488 documents were selected for the qualitative analysis. China, Japan and the United States play a leading role in the development of these technologies. Companies constitute the vast majority of the applicants. The focus of the inventions turned out to be: equipment, membranes, customized equipment/processes for specific wastewaters, fouling control and cleaning, combinations of technologies and sustainability. Finally, enhancements in the operational performance of the membrane separation equipment and the development of membrane materials with increased water flow and fouling resistance are found to be key factors to broaden the application of membrane separation technology in wastewater treatment.

Assessing and Modifying Selective Transport for Nonaqueous Flow Battery Membranes

Membranes are a critical component for redox flow battery (RFB) systems. An ideal membrane must be stable in the RFB solvent and process environment, and to obtain desirable electrochemical performance must facilitate transport of the charge compensating ion while minimizing crossover of the dissolved electroactive species (e.g., redox shuttles). For more established aqueous RFB systems commercial membranes, such as sulfonated fluoropolymers, have been used to successfully facilitate development of RFB power stacks at industrial scales.Recently, there has been interest in developing nonaqueous, or organic, RFB systems. A potential advantage of a nonaqueous RFB is the accessibility of higher voltages per cell, which would result in higher energy density for the RFB system. Membrane materials for nonaqueous RFBs are not well established, and thus the composition and processing for these membranes is an open area for further research.In this talk, efforts towards the understanding and development of a nonaqueous RFB membrane material will be described. Assessment of the conductivity and crossover of the membrane material system will be discussed, as well as efforts to improve electrochemical properties and membrane stability. Initial results suggest that the interactions between the redox shuttles and the membrane are in many cases fundamentally very different for nonaqueous RFB membranes compared to aqueous RFB membranes, providing possibilities for different routes to design nonaqueous RFB membrane materials.

Robust poly(alkyl–fluorene isatin) proton exchange membranes grafted with pendant sulfonate groups for proton exchange membrane fuel cells

The development of high-performance low-cost membrane materials is crucial for application in proton exchange membrane fuel cells (PEMFCs). In this study, two types of poly(alkyl–fluorene isatin)-based proton exchange membranes (PEMs) are designed and prepared successfully via facial superacid-catalyzed Friedel–Crafts polycondensation. The fluorene-based polymers exhibit good solubility and film-forming ability, and the produced PEMs possess excellent mechanical properties, dimensional stability, and oxidization stability because of the aromatic backbone. Atomic force microscopy showed that HFxDPy-PS-based PEMs have more significant phase separation structures than MFxDPy-PS-based PEMs due to the longer soft alkyl chains on the fluorene groups. HF3DP1-PS exhibits high proton conductivity that reached 88.56 mS cm−1 at 80 °C. The H2/O2 single fuel cell assembled with HF3DP1-PS exhibits a power density of 753 mW cm−2, which is close to that of a fuel cell with commercial Nafion 212 (774 mW cm−2) under the same conditions. All these results indicate the broad potential application of poly(alkyl–fluorene isatin)-based PEMs in PEMFCs.

On the Characterization of Membrane Transport Phenomena and Ion Exchange Capacity for Non-Aqueous Redox Flow Batteries

The development of high-performance membrane materials for non-aqueous redox flow batteries (NAqRFBs) could unlock a milestone towards widespread commercialization of the technology. Understanding of transport phenomena through membrane materials requires diagnostic tools able to monitor the concentrations of redox active species. While membrane characterization in aqueous media focused the attention of the scientific community, dedicated efforts for non-aqueous electrolytes remain poorly developed. Here, we develop new methodologies to assess critical membrane properties, namely ion exchange capacity and species transport, applied to NAqRFBs. In the first part, we introduce a method based on 19F-NMR to quantify ion exchange capacity of membranes with hydrophobic anions commonly used in non-aqueous systems (e.g., PF6 − and BF4 −). We find a partial utilization of the ion exchange capacity compared to the values reported using traditional aqueous chemistry ions, possibly limiting the performance of NAqRFB systems. In the second part, we study mass transport with a microelectrode placed on the electrolyte tank. We determine TEMPO crossover rates through membranes by using simple calibration curves that relate steady-state currents at the microelectrode with redox active species concentration. Finally, we show the limitations of this approach in concentrated electrolyte systems, which are more representative of industrial flow battery operation.

Design, fabrication, and physicochemical characterization of polyamideimide membranes containing ZIF-8 and CMS particles for potential gas separation applications

The development of hybrid membrane materials with excellent permeance and selectivity applied for gas separation has been the focus of world attention. However, the development of membranes with efficient separation performance remains a great challenge.The ZIF-8 nanocrystals were prepared by a precipitation reaction with Zinc metal cluster and 2-methylimidazole, whereas the carbon molecular sieves (CMS) were synthesized by pyrolysis of polyamideimide (PAI) polymer. The successful formation of ZIF-8 nanocrystals was evident from the rhombic octahedron shape, and EDX confirms the presence of Zn metal cluster and methylimidazole linker. The ZIF-8 and CMS nanoparticles incorporated PAI membranes were prepared using the phase inversion technique with varying loading wt.% of 1, 2, and 3%. PAI/ZIF-8 and PAI/CMS membranes cross-sectional morphology confirmed that synthesized nanoparticles were well embedded through the PAI membrane. The PAI/ZIF-8 (3 %) membrane, thin dense skin top layer, and well-defined honeycomb porous substructure were observed. It was noticed that the PAI/ZIF-8 (1 wt%) membrane had shown endurance for ultimate strain up to 8.25 % which is comparatively higher than the PAI/CMS membranes. However, both the ZIF-8 and CMS membranes had shown a decrease in the mechanical stability at the higher filler loading of 3 wt% which could be due to the increased brittleness due to the aggregation of filler particles at the higher loading. Thus, the inclusion of ZIF-8 and CMS particles in the PAI matrix positively altered the physicochemical properties of the resulting hybrid membranes, which could help them achieve remarkable gas permeance and selectivity.