Advanced Membranes最新文献

Superacid catalysis, a suitable method for the synthesis of membrane materials owing to its facile polymerization procedure, has been extensively studied. However, superacid-catalyzed binary coplanar polymer membranes generally exhibit low permeabilities. In this study, a rigid 3D triptycene-based polymer was synthesized by the superacid catalysis of triptycene with trifluoroacetophenone and diphenyl ether to enhance membrane permeability for the molecular sieving of nitrogen over volatile organic compound (VOC). The synthesis of polymers with (CF₃PhET) or without triptycene (CF₃PhE) was investigated using different characterizations. The triptycene content of the synthesized polymers was optimized based on an analysis of the molecular weight, membrane-forming properties, and separation performance. The separation performances of membranes fabricated using CF₃PhE, CF₃PhET, and a mixture of CF₃PhE and triptycene were compared. Results showed that the introduction of non-coplanar triptycene in the membrane can increase permeability by nearly 60 times due to the enhanced free volume, from 30 Barrer for the CF₃PhE membrane to 1755 Barrer for the membrane with 5 ​mol% triptycene content for the separation of a 3 ​mol% nitrogen/cyclohexane mixture at 1 ​L/(m²·min). Furthermore, the rejection remains constant, which provides an effective idea for the synthesis of membrane materials with high performance using superacid catalysis.

Commercial nanofiltration (NF) membranes based on polyamides may experience a decline in permeation performance after prolonged operation. The short lifespan of NF membranes will lead to waste and additional carbon emissions. Thus, rejuvenating membranes and extending their lifespan seem more meaningful than investigating new materials. In this paper, polyamide NF membranes were modified with various polyphenol monomers to improve their permeation performance. The effects of different polyphenols on pore size, surface morphology, and permeation performance of the NF membranes were thoroughly investigated. After modification with tannic acid, the NF membrane exhibits improved salt rejection while experiencing an acceptable decrease in water flux. It should be noted that the commercial NF membrane element fabricated by Koch can recover its Na₂SO₄ rejection from 83.0% to 94.2% and demonstrate long-term stability after rejuvenation with tannic acid. Combined with the environmental friendliness of polyphenols, this straightforward modification method has the potential for prolonging the operational lifespan of industrial NF membrane products.

Organic solvent nanofiltration (OSN) is an emerging energy-efficient separations technology, which urgently requires easily processable OSN membranes with high selectivity and broad-spectrum organic solvent applicability to facilitate enhanced industrial applications. Herein, we describe the preparation of microporous polyesteramide (PEA) membranes through interfacial polymerization (IP) between amino-diphenol monomers and trimesoyl chloride (TMC) on a poly(ether ether ketone) (PEEK) support. The crosslinked network structures and large twisted monomers enhance the microporosity of PEA membranes, leading to a significant improvement in solvent permeance while maintaining high selectivity. The optimized PEA membrane demonstrates exceptional permeance for acetone (21.0 ​L ​m⁻² ​h⁻¹ bar⁻¹) and methanol (14.3 ​L ​m⁻² ​h⁻¹·bar⁻¹), with a molecular weight cut-off of 296 ​g ​mol⁻¹. Additionally, the PEA/APH-diphenol membrane exhibits ultrafast permeance for the nonpolar solvent toluene (8.3 ​L ​m⁻² ​h⁻¹·bar⁻¹), owing to the introduction of a large number of ester groups. Overall, PEA membranes prepared through the molecular-level structure design of IP monomers possess enormous industrial application potential owing to their high performance and broad-spectrum applications.

Both salt rejection and pressure-bearing properties of the conventional thin film composite (TFC) polyamide reverse osmosis (RO) membrane are easily weakened at high temperature. In order to improve the high temperature resistance, in this work, a polyamide TFC RO membrane with covalent organic frameworks (COFs) intermediate layer was prepared. Firstly, the COFs layer was decorated on polyether sulfone (PES) support membrane by a unidirectional diffusion method and further modified for shrinking the micropore via the chemical crosslinking reaction with 1,3-diamino-2-propanol (DAPL) or ethylenediamine (EDA), and then continued the conventional interfacial polymerization of m-phenylene diamine (MPD) and trimesoyl chloride (TMC) on the resultant COFs layer for preparing the RO membrane. Furthermore, the correlationship between the microstructure of COFs layer and the separation performance of modified RO membrane was systematically investigated. Due to the introduction of the COF_TpPa-DAPL intermediate layer with more regular microstructure and specific hydrophilicity, the resultant TFC-COF_TpPa-DAPL RO membrane exhibited improvement in water flux by 30 ​% (reached to 50.5 ​L ​m⁻² ​h⁻¹) and higher salt rejection (>99.5 ​%) as compared with the conventional polyamide RO membrane and other reported temperature resistance RO membranes. Meanwhile, this TFC-COF_TpPa-DAPL membrane showed good long-term separation stability during the RO process for 160 ​h. Especially, its water flux increased to 98.8 ​L ​m⁻² ​h⁻¹ without weakening salt rejection (about 99.4 ​%) at 70 ​°C. This study provides an effective way to fabricate the high temperature resistance TFC polyamide RO membrane with good comprehensive separation performance based on COFs intermediate layer.

The study provides an in-depth study on the gas adsorption and transport behaviors of MOF glass membranes for the first time. Temperature dependance of gas permeability, adsorption coefficients and diffusion coefficients between 298 ​K and 313 ​K for TIF-4 and ZIF-62 glass membrane were evaluated. The CO₂ permeability was dominated by the adsorption process, while CH₄ transport was mainly driven by the activated diffusion. Further, the MOF glass membranes exhibited significant entropic selectivity in adsorption, along with notable enthalpic selectivity in diffusion.

Emerging contaminants, including antibiotics, threaten water safety and public health. To remove these contaminants while retaining beneficial minerals in water, such as calcium (Ca), a novel thin-film composite nanofiltration (NF) membrane was manufactured through polymerization of a barrier layer composed of polypiperazine amide onto polyvinylidene fluoride (PVDF) hollow fiber (HF) substrate. The pore size of the PVDF surface was refined by introducing poly(vinylpyrrolidone) via a thermally induced phase separation method. Then piperazine (PIP) and trimesoyl chloride were selected to synthesize the NF membrane by interfacial polymerization with NaHCO₃ as an additive. The influence of PIP concentration on the membrane morphology and separation performance was investigated. The optimized HF NF membrane (NF3) exhibited high water permeability (8.08 ​L/(m² ​h ​bar)) due to its strong hydrophilicity. It also demonstrated a molecular weight cut-off of 378 ​Da and an enhanced negative surface charge (−43.96 ​mV), which was beneficial for the exclusion of antibiotics and passage of Ca²⁺. The high tetracycline rejection (98.9 ​%) enabled the NF3 membrane to achieve superior Ca²⁺/antibiotic selectivity (37.27) compared with most commercially available NF membranes. This study offers novel insights into tailoring the mineral/micropollutant selectivity of HF NF membranes for drinking water purification.