Advanced Membranes最新文献

Spray coating has been exploited to fabricate and tailor the morphologies of various components in thin film composite membranes separately. For the first time, here we exploit this technology to construct and assemble both the selective layer and porous support of a thin-film composite membrane in a single process. In our approach, spray-assisted non-solvent induced phase inversion and interfacial polymerization reduced the time required to fabricate thin-film composite membranes from 3 – 4 days to 1 day and 40 ​min. Our approach did not sacrifice membrane separation performances during desalination of a mixture comprising 2000 ​ppm of NaCl in water at 4 ​bar and room temperature. At these conditions, compared to traditional thin film composite membranes, the water permeance of our spray coated membranes was higher by 35.7 %, reaching 2.32 ​L ​m⁻² ​h⁻¹ bar⁻¹, while achieving a NaCl rejection rate of 94.7 %. This demonstrated the feasibility of fabricating thin film composites via spray coating in a single process, potentially reducing fabrication time during scale-up production.

Polymers of intrinsic microporosity (PIMs) stand out as promising membrane materials with exceptional separation performance. In this study, we crafted a highly efficient gas separation membrane using an emerging material, called cyclohexyl-fused spirobiindane-based PIM (CCS-PIM). The CCS-PIM features a robust and rigid microporous structure with a high specific surface area (S_BET ​= ​704.6 ​m²/g), exhibiting excellent CO₂-selective adsorption capacity. The CO₂ adsorption uptake is 0.78 ​mmol/g at 273 ​K and 0.15 ​bar, leading to IAST selectivity of 25.2 for CO₂/N₂ (15/85 v/v) and 16.7 for CO₂/CH₄ (50/50 v/v) at 298 ​K. The precisely tuned pore size of the CCS-PIM membrane leads to an enhanced molecular sieving effect, showcasing superior selectivity across various gas pair separations. It demonstrates an O₂/N₂ selectivity of 6.03 and a CO₂/CH₄ selectivity of 26.1, surpassing the 2008 Robeson upper bounds. This study suggests a strategic method to improve gas separation efficiency by customizing a locked PIM structure with precise molecular sieving through the insertion of variously sized rings.

The prevalent adoption of lithium-ion batteries (LIBs) has sparked a surge in interest regarding lithium extraction, particularly from lithium-rich brines. As some brine sources contain a higher ratio of Mg²⁺ ions to Li ​⁺ ​ions, Mg²⁺/Li⁺ separation becomes essential to improve extraction efficiency. Multiple membrane technologies were utilized in this application, including electrodialysis, membrane capacitive deionization, and nanofiltration (NF). Among the different technologies, NF membranes fabricated through interfacial polymerization have gained interdisciplinary attention due to their ease of modification, relative simplicity, and cost-effectiveness. Despite that, there are still multiple challenges in Mg²⁺/Li⁺ ​separation such as high Mg²⁺/Li⁺ ratio (MLR), trade-off between Mg²⁺/Li⁺ separation factor and pure water permeance (PWP), membrane fouling, and optimal working pH. To address these challenges, this review summarizes different nanofillers used to enhance the NF membrane performance, including carbon-based nanofillers, and polyhedral oligomeric silsesquioxane (POSS). Additionally, different NF membranes were categorized based on the modification to the interfacial polymerization, such as types of aqueous monomer, addition of nanofillers in aqueous phase, addition of nanofillers in substrate, addition of an extra layer within the membrane, and other modifications. Lastly, perspectives on the factors that affect the separation performance of the NF membranes including surface zeta potential, feed pH, pore size, hydrophilicity, and MLR will be discussed. It is anticipated that this comprehensive review can provide insights into the current progress of various modification strategies on NF membranes to drive future research and development of Mg²⁺/Li⁺ separation using this technology among the community.

Dense ceramic membranes with H⁺ or O²⁻ conductivity have been widely used for fuel production through electro-hydrogenation/dehydrogenation or electro-oxygenation/deoxygenation. Electrochemical conversion processes demonstrate advantages over conventional redox reaction processes in terms of capital cost, energy savings, process intensification and product selectivity. Intermittent renewable power (e.g., solar and wind power) can be used to drive electrochemical processes so that renewable energy is stored in fuels as energy carriers, including hydrogen, ammonia, syngas, methane and ethylene. This review summarizes the pathways to store renewable energy via ion-conducting membrane reactors and discusses the commercialization progress and prospects of these energy technologies.

In this study, a multi-layer pervaporation composite membrane was prepared by spray-coating a hydrophilic layer consisting of poly(allylamine hydrochloride) (PAH)/polyvinyl alcohol (PVA)/trimesic acid (BTA) onto a polyethersulfone (PES) porous substrate. The presence of amine groups facilitated the transport of water molecules, enabling the composite membrane to exhibit excellent water/ethanol separation properties. When a feed solution consisting of 90 ​wt% ethanol and 10 ​wt% water was dehydrated using the PV membrane at 70 ​°C, a flux of 1.46 ​kg ​m⁻² ​h⁻¹ with a water/ethanol separation factor of 3300 was realized. In addition, after coating a 267 ​nm silicone rubber layer on top of the membrane, the separation factor was further increased by 70.79 % to 5285, while the flux was slightly decreased by 12.33 % to 1.28 ​kg ​m⁻² ​h⁻¹. This was because the hydrophobic silicone rubber layer reduced the water swelling effect of the selective layer and hindered the permeation of ethanol-water coupling molecules, resulting in a reduction in the ethanol flux of the composite membrane and an improvement in the separation factor. This simple but effective method to improve dehydration properties was very useful for fabricating PV composite membranes.

Polyamide (PA) membrane is extensively used in various membrane separation processes due to its easy preparation, high selectivity and good acid-base stability. However, the PA material is vulnerable to the attack of free chlorine which causes PA chlorination degradation and eventually damages the membrane selectivity. As such, developing chlorine-resistant membrane has become a research focus in membrane technology recently. This accelerates the emergence of a large number of novel PA membranes. However, reviews on this aspect are quite rare to date. Thus, providing an updated critical review on the PA-based anti-chlorine membrane is highly needed. This paper aims to critically review the recent development in the PA chlorine-resistant membrane designed specially via the modification of the PA selective layer. The recent advances in the PA anti-chlorine membranes are briefly introduced first. The mechanism and influential factors of the chlorination of PA membrane are subsequently presented. The strengths and limitations of the recently developed PA anti-chlorine membrane are critically evaluated afterward. The challenges and future research directions of the sustainably chlorine-resistant PA membranes are finally discussed. This article can provide insightful guidance for the future development of the PA-based chlorine-resistant membrane.

Crystallization of active pharmaceutical ingredients is essential in pharmaceutical production. Pervaporation, a thermally-driven membrane process, has not been explored in API crystallization. Here we demonstrated PV-assisted crystallization (PVaC) for simultaneous recovery of API ortho-aminobenzoic acid (o-ABA) and pure solvent. The PERVAP 4060 made of organophilic polymer was found suitable given the reasonable flux of ethanol of 3.69 ​kg/m²/h at 45 ​°C with saturated solution and 99.9% o-ABA rejection. A parametric study showed that the membrane permeance increased with feed flow rate and temperature, but decreased with supersaturation. In the sequential PVaC, the stable form I of o-ABA was obtained with 25 ​°C PV; while with 45 ​°C PV, only metastable form II crystallized. In the simultaneous PVaC, at 0 time lag pure form II was produced; by increasing time lag, form I increased significantly. The results indicated potential routes to control polymorph formation via PVaC, providing a promising alternative for API production.

Machine learning (ML) is a data-driven approach that can be applied to design, analyze, predict, and optimize a process based on existing data. Recently, ML has found its application in improving membrane separation performance for wastewater treatment. Models have been developed to predict the performance of membranes to separate contaminants from wastewater, design optimum conditions for membrane fabrication for greater membrane separation performance and predict backwashing membranes and membrane fouling. This review summarizes the progress of ML-based membrane separation modeling and explores the direction of the future development of ML in membrane separation-based wastewater treatment. The strengths and drawbacks of the ML algorithms extensively used in membrane separation-based wastewater treatment are summarized. Artificial neural network (ANN) was the most used algorithm for modeling membrane separation-based wastewater treatment. Future research is recommended to focus on the development of integrated ML algorithms and on combining ML algorithms with other modeling approaches (e.g., process-based models and statistical models). This will serve to achieve higher accuracy and better performance of the ML application.

Nanofiltration has gained increasing attention in lithium extraction from salt lake brine with high Mg²⁺/Li⁺ ratio. However, conventional nanofiltration membranes with negatively charged surfaces suffer from low Mg²⁺/Li⁺ selectivity. Herein, positive nanofiltration membranes with high charge density were fabricated via a two-step charge enhancement strategy. High concentration of polyethylenimine was used as the aqueous monomer to ensure the abundant amino groups on the membrane surface. To further enhance the electro-positivity, 2, 3-epoxypropyl trimethyl ammonium chloride was grafted through ring-opening reactions. The as-obtained membranes demonstrated positive zeta potentials over a large pH range (3-10), leading to significantly strengthened Donnan exclusion for Mg²⁺. The membrane rejection to MgCl₂ was up to 99.3% while the rejection to LiCl was only ∼30%. The Mg²⁺/Li ​⁺ ​separation factor was 167 when filtration simulated brine with a Mg²⁺/Li⁺ ratio of 20 (2000 ​ppm MgCl₂ and LiCl mixture), which is the highest value achieved among polyamide-based nanofiltration membranes. In addition, the membranes exhibited good stability in 40 ​h’ continuous testing. The modification strategy proposed in the present work is highly compatible with current industrial membrane preparation processes and easy to scale up with cost effectiveness.