Journal of Membrane Science Letters最新文献

New method of emulsion synthesis of Nafion®-type copolymer composition by using nanodiamond platform has been proposed and implemented. Produced polymeric coagulate saturated with diamonds (4.1 % wt.) possessed increased ionic capacity of the copolymer comparative to the analogue without diamonds. SEM patterns for coagulate membranes showed labyrinthine structures with diamonds integrated into copolymer without any segregation. This structuring provided necessary elastic and strength properties of new type membranes for hydrogen fuel cells. In new membranes synchrotron experiments exhibited a network of ionic channels which ensured a proton conductivity by one order of magnitude higher than that for the analogue produced of premade components.

Electrokinetic measurements to determine the electrical properties (zeta potential) of membrane surfaces have become increasingly popular in the toolbox of characterization techniques. However, it has been established in the literature that parasitic phenomena such as electrokinetic leakage can hamper data interpretation, leading to not only quantitative but also qualitative errors in membrane zeta potential determination. To date, the only method for highlighting and accounting for electrokinetic leakage is limited to flat-sheet membranes. In this letter, we propose an alternative method that is much less time-consuming and applicable to all membrane geometries. This method is based on the determination of the electrokinetic index, which we define as the ratio of the apparent zeta potentials determined from single measurements of the streaming current and streaming potential coefficients. We show that variation in the electrokinetic index reflects modifications occurring within the membrane matrix (in addition to surface properties alteration). The chemical degradation of polyethersulfone (PES)-based flat-sheet and hollow-fiber membranes is used as a proof of concept, but the proposed approach is readily transposable to other problems of practical interest, such as e.g. membrane fouling. This work also paves the way for the development of a new type of electrokinetic sensors for on-line monitoring of membrane operations.

Membrane distillation (MD) is a separation technology for many industries including desalination, pharmaceuticals, and food processing. However, MD technology readiness has not reached the required level to penetrate the desalination and water treatment market. One of the challenges to commercialization is the limited development and inaccurate assessment of MD-specific membranes. In fact, measuring the performance of MD membranes is challenging because it is dependent on process parameters, making it difficult to separate the individual influences of the process operating conditions and the membranes’ intrinsic properties. These shortcomings drive the need for a standardized methodology to compare and report membrane performance independently of the process parameters. In this work, we propose a standardized methodology for measuring the permeance of MD membranes using a reduced scale direct contact membrane distillation (DCMD) setup. This methodology has the potential to streamline membrane assessment and support ongoing efforts in MD membrane development and process scale-up.

Controlling the internal concentration polarization in forward osmosis (FO) membranes by minimizing the substrate thickness is critical to enhancing the water flux. This study aimed to achieve the fabrication of an ultra-thin FO membrane by forming the polyamide (PA) active layer on a thin and straight-bore film, a so-called track-etched (TE) membrane. The polycarbonate TE membrane had a uniform pore size of 0.22 µm and a thickness of 25 µm. The PA active layer was successfully formed only by creating a thin m-phenylenediamine solution layer on the smooth TE membrane surface before interfacial polymerization. The TE- FO membrane with low porosity (14 %) provided a water flux of 21 L/m²h and a reverse salt flux of 8.0 g/m²h when evaluated with a 1.0 M NaCl draw solution. Further evaluations showed the potential of increasing water flux by increasing the TE substrate porosity (14 %) and reducing the apparent PA active layer thickness (504 nm). These results suggest the potential of achieving a high-water flux FO membrane using a thin TE substrate and ultimately improving the validity of FO membrane-based water treatment.

Nanofiltration is widely used in various industries to separate solutes from solvents. To foster a circular economy, establishing a closed-loop lifecycle for the membrane materials is highly important. In this study, we fabricated recyclable nanofiltration membranes from chemically recyclable polymers —polyester P(BiL⁼)_ROP and poly(cyclic olefin) P(BiL⁼)_ROMP— using γ-butyrolactone as a green solvent. These two polymers, of two different polymer classes, were obtained from a single monomer, which could be recycled back to the same monomer, exhibiting the unique “one monomer–two polymers–one monomer” closed-loop chemical circularity. The effect of physical treatment, such as annealing, hot-pressing, and air exposure on the morphological characteristics and performance of the nanofiltration membranes was investigated. We revealed the interplay between membrane pore size, thickness, density and the molecular sieving performance of the nanofiltration membranes. Solute rejections were mainly governed by the membrane pore size. However, solvent flux was mainly governed by the membrane density that determines the free volume interconnectivity. The membranes exhibited a tunable molecular weight cutoff between 553 and 777 g mol⁻¹ and methanol permeance between 5.9 and 9.8 L m^–2 h^–1 bar⁻¹. The membranes exhibited excellent long-term nanofiltration stability over 1 week. The combination of the green solvent used for membrane fabrication and the circular life cycle of the polymer membrane brings one step closer to closing the circularity loop of membrane technology.

Advanced membranes fabricated from multilayer/laminated graphene oxide (GO) are promising in water treatment applications as they provide very high flux and excellent rejection of various water pollutants. However, these membranes have limited viability, and suffer from instabilities and swelling due to the hydrophilic nature of GO. In this work, the permeability and rejection performance of laminated GO membranes were improved via functionalization with ethylenediamine (EDA) and polyethyleneimine (PEI). The membranes are fabricated via the pressure-assembly stacking technique, and their structure is well characterized. The performance, rejection, and stability of the fabricated functionalized GO membranes were evaluated. Pillaring the GO layers using diamine and polyamine resulted in exceptionally high water permeability of 113 L/m²h (LMH) compared to only 28 LMH for the pristine GO membrane while simultaneously satisfying high rejection of multivalent salts of 79.4, 35.4, and 19.6 % for Na₂SO₄, MgCl₂, and NaCl, respectively. The results obtained indicate that proper functionalization of GO provides a roadmap for the potential commercialization of such advanced membranes in water treatment applications.

The purification of 1,3-butadiene from C₄ hydrocarbon mixtures currently relies on energy-intensive extractive distillation. In this study, we employed ZIF membranes for this challenging separation for the first time, unveiling their superior capability in isolating 1,3-butadiene from other C₄ hydrocarbons with similar sizes, including 1-butene, isobutene, and n-butane. This strong sieving effect was evident from two types of ZIF-8 membranes: one with low crystallinity fabricated via the all-vapor-phase ligand-induced permselectivation (LIPS) method and another with high crystallinity synthesized through the seeded growth method. The gas permeances decreased with increasing kinetic diameters, following the order of 1,3-butadiene (4.31 Å) > 1-butene (4.46 Å) > n-butane (4.687 Å) > isobutene (4.84 Å). The LIPS-ZIF-8 membrane exhibited a high 1,3-butadiene permeance of approximately 1.43 × 10⁻⁷ mol/m² s Pa (∼430 GPU) and ideal separation factors of 18, 56, and 134 for 1,3-butadiene over 1-butene, n-butane, and isobutene, respectively. In separating four-component C₄ mixtures, these membranes could enrich 1,3-butadiene content from 50% in the feed to 96–98% in the permeate through a single separation step. This unprecedented performance is attributed to differences in C₄ diffusivities that span several orders of magnitude.

A solvent-free post-treatment process known as vapor phase infiltration (VPI) is used to engineer the organic solvent reverse osmosis (OSRO) performance of polymer of intrinsic microporosity 1 (PIM-1) membranes via infiltration of trimethylaluminum (TMA) metal-organic vapor. The infiltration of inorganic aluminum constituents hybridizes the pure polymer PIM-1 into an organic-inorganic material (AlO_xH_y/PIM-1) with enhanced chemical stability. A homogenous distribution of inorganic loading in PIM-1 is achieved due to the reaction-limited infiltration mechanism, and the OSRO performance is enhanced as a result. OSRO separations of ethanol/isooctane mixtures using these membranes are shown to be capable of breaking the azeotropic composition with a separation factor for ethanol over isooctane greater than 5 and an ethanol permeance of 0.1 Lm^–2h^–1bar^–1. Thus, these organic-inorganic hybrid membranes created via VPI show promise as an alternative method for separating azeotropic liquid mixtures.

Polymeric membranes have garnered widespread adoption in applications such as desalination, wastewater treatment, and water reuse. Nevertheless, the current disposal practices for these end-of-life (EoL) polymeric membranes, primarily landfill and incineration, are neither economically nor environmentally sustainable. To address this challenge, we first analyzed the factors leading to the EoL phase for these membranes; an understanding that is critical in developing or selecting appropriate recycling technologies. We further proposed a technological framework to guide recycling choices based on the specific state of the EoL membrane. In cases where the membrane exhibits significant breakage, dissolution using eco-friendly solvents, followed by membrane re-preparation, is recommended. For membranes without substantial breakage, regeneration, upcycling, or downcycling strategies can be deployed based on scenarios. We underscored the crucial role of irrecoverable foulant removal within the regeneration technology. Additionally, the reaction interface must be suitably remediated before the application of upcycling technology to EoL microfiltration/ultrafiltration membranes. The downcycling strategy, facilitated by NaOCl oxidation, is readily applicable to EoL nanofiltration/reverse osmosis membranes. This brief frontier review aims to serve as a valuable reference for recycling end-of-life water treatment polymeric membranes.

Thin-film composite (TFC) polyamide (PA) RO membrane modified with a layer of tethered poly(acrylic acid) (PAA) chains displayed intrinsic rejections of nitrate, boron, As(III), and As(V) of 98.0%, 90.7%, 96%, and 99.6%, respectively. The solute permeability coefficients for nitrate, boron, As(III), and As(V) by the SNS-PAA-PA membrane were lower by 31–38%, 49–63%, 57–72% and 87–93% relative to tested commercial membranes. The above results indicate that the SNS-PAA-PA membrane should be suitable for purification of brackish source water contaminated with nitrate, boron, As(III), and As(V) to levels 1219 ppm, 2 ppm, 95 ppb, and 948 ppb, respectively. The study results suggest that there is merit in further exploration of the potential of the present approach for enhancing RO membranes performance for targeted solute removal.