High-Performance Zeolitic Hollow-Fiber Membranes by a Viscosity-Confined Dry Gel Conversion Process for Gas Separation.

Zeolite membranes show great potential for gas and hydrocarbon separations, but high manufacturing cost has been one of the main hurdles in their industrial application. Here we demonstrate a method termed viscosity-confined dry gel conversion (VCDGC) for zeolite hollow fiber membrane fabrication. We demonstrate in detail the VCDGC synthesis of small-pore CHA zeolite membranes. Extensive permeation measurements reveal that dry gel-processed CHA zeolite hollow fiber membranes have excellent gas and hydrocarbon separation characteristics well exceeding or comparable to current membranes. Medium-pore MFI membranes are also fabricated, and their favorable hydrocarbon separation characteristics indicate the versatility and reliability of the VCDGC method.

Continuous Zeolite MFI Membranes Fabricated from 2D MFI Nanosheets on Ceramic Hollow Fibers.

High-quality 2D MFI nanosheet coatings were prepared on α-alumina hollow fiber supports by vacuum filtration and then transformed into molecular sieving membranes by two sequential hydrothermal treatments. This processing method eliminates the need for specially engineered silica-based support materials that have so far been necessary to allow the formation of functional membranes from 2D MFI nanosheets. The sequential steps enhance adhesion of the membrane on the fiber support, fill in nanoscale gaps between the 2D nanosheets, and preserve the desirable (0k0) out-of-plane orientation without the need of any support engineering or modification. The membrane exhibits high performance for separation of n-butane from i-butane, and for other technologically important hydrocarbon separations. The present findings have strong implications on strategies for obtaining thin, highly selective zeolite membranes from 2D zeolites in a technologically scalable manner.

Single-walled zeolitic nanotubes.

We report the synthesis and structure of single-walled aluminosilicate nanotubes with microporous zeolitic walls. This quasi-one-dimensional zeolite is assembled by a bolaform structure-directing agent (SDA) containing a central biphenyl group connected by C10 alkyl chains to quinuclidinium end groups. High-resolution electron microscopy and diffraction, along with other supporting methods, revealed a unique wall structure that is a hybrid of characteristic building layers from two zeolite structure types, beta and MFI. This hybrid structure arises from minimization of strain energy during the formation of a curved nanotube wall. Nanotube formation involves the early appearance of a mesostructure due to self-assembly of the SDA molecules. The biphenyl core groups of the SDA molecules show evidence of π stacking, whereas the peripheral quinuclidinium groups direct the microporous wall structure.

All-Nanoporous Hybrid Membranes: Incorporating Zeolite Nanoparticles and Nanosheets with Zeolitic Imidazolate Framework Matrices.

Metal-organic framework (MOF) membranes have attractive molecular separation properties but require challenging thin-film deposition techniques on expensive/specialty supports to obtain high performance relative to conventional polymer membranes. We demonstrate and analyze in detail the new concept of all-nanoporous hybrid membranes (ANHMs), which combines two or more nanoporous materials of different morphologies into a single membrane without the use of any polymeric materials. This allows access to a previously inaccessible region of very high permeability and selectivity properties, a feature that enables ANHMs to show high performance even when fabricated with simple coating and solvent evaporation methods on low-cost supports. We synthesize several types of ANHMs that combine the MOF material ZIF-8 with the high-silica zeolite MFI (the latter being employed in both nanoparticle and nanosheet forms). We show that continuous ANHMs can be obtained with high (∼50%) volume fractions of both MOF and zeolite components. Analysis of the multilayer microstructures of these ANHMs by multiple techniques allows estimation of the propylene/propane separation properties of individual ANHM layers, providing initial insight into the dramatically increased permeability and selectivity observed in ANHMs in relation to single-phase nanoporous membranes.

Ion-Exchanged SAPO-34 Membranes for Krypton-Xenon Separation: Control of Permeation Properties and Fabrication of Hollow Fiber Membranes.

Separation of radioisotope 85Kr from 136Xe is of importance in used nuclear fuel reprocessing. Membrane separation based on zeolite molecular sieves such as chabazite SAPO-34 is an attractive alternative to energy-intensive cryogenic distillation. We report the synthesis of SAPO-34 membranes with considerably enhanced performance via thickness reduction based upon control of a steam-assisted vapor-solid conversion technique followed by ion exchange with alkali metal cations. The reduction of membrane thickness leads to a large increase in Kr permeance from 7.5 to 26.3 gas permeation units (GPU) with ideal Kr/Xe selectivities >20 at 298 K. Cation-exchanged membranes show large (>50%) increases in selectivity at ambient or slight subambient conditions. The adsorption, diffusion, and permeation characteristics of ion-exchanged SAPO-34 materials and membranes are investigated in detail, with potassium-exchanged SAPO-34 membranes showing particularly attractive performance. We then demonstrate the fabrication of selective SAPO-34 membranes on α-alumina hollow fibers.

Effect of Continuous-Wave Low-Intensity Ultrasound in Inflammatory Resolution of Arthritis-Associated Synovitis.

BACKGROUND: Low-intensity ultrasound (LIUS) can reduce pain and improve function in arthritic joints. Neutrophils are first-line actors in host defense that recruit macrophages. Dead neutrophils are removed during resolution of inflammation. Delayed neutrophil clearance can lead to extended inflammation or even chronic autoimmune disease. Although neutrophil extracellular traps (NETs) in arthritic tissue are involved in the pathogenesis of arthritis, their functional role has not been clarified. OBJECTIVES: This study aimed to investigate the effect of LIUS on synovial inflammation and its resolution via neutrophil clearance. METHODS: Synovitis was induced by intra-articular injection of complete Freund's adjuvant (CFA) into the left knee joint of 58 adult male Sprague-Dawley rats. Low-intensity ultrasound (1 MHz, 200 mW/cm(2)) was applied for 10 minutes daily. Neutrophil clearance was assessed with the expression of myeloperoxidase (MPO). In addition, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining and NET formation in the synovium were observed. In neutrophil and macrophage cultures from peripheral blood, the effect of NET clearance by LIUS was investigated. RESULTS: In CFA-induced synovitis, MPO-positive neutrophils peaked after 2 to 3 days, filling the inflammatory core. Monocytes and macrophages in the periphery later infiltrated the core and were reduced thereafter. Low-intensity ultrasound reduced synovial hyperplasia and induced earlier MPO clearance. Neutrophils in the core of the inflamed synovium exhibited NET formation, which LIUS increased. Low-intensity also induced NETs in peripheral polymorphonuclear cells in an intensity-dependent manner and potentiated phorbol myristate acetate (PMA)-induced NETosis. The PMA-induced NETs were cleared by macrophages; clearance was enhanced by LIUS. LIMITATIONS: The effect of LIUS on CFA-induced inflammation was observed only during the acute phase. Although the effect of LIUS on NETosis in the in vitro neutrophil culture system was clear, the in vivo NETosis cannot be quantified. CONCLUSIONS: Neutrophil extracellular traps act in inflammatory synovitis, and LIUS enhanced the NETs and resulted in neutrophil clearance by enhancing the phagocytosis of macrophages, which might be a factor underlying the therapeutic effect of LIUS in arthritic synovium.

Quantitative analysis of water distribution in human articular cartilage using terahertz time-domain spectroscopy.

The water distribution in human osteoarthritic articular cartilage has been quantitatively characterized using terahertz time-domain spectroscopy (THz TDS). We measured the refractive index and absorption coefficient of cartilage tissue in the THz frequency range. Based on our measurements, the estimated water content was observed to decrease with increasing depth cartilage tissue, showing good agreement with a previous report based on destructive biochemical methods.