Hollow Fiber Research Articles

Sulfur hexafluoride gas response characteristics of hollow-core fiber based spectral absorption sensor

SF6 gas is a greenhouse gas that is harmful to the atmospheric environment and is widely used in gas-insulated power equipment. In this paper, a new SF6 gas detection system based on hollow waveguide fiber (HWG) is proposed, which can be used for low concentration SF6 gas leakage detection. The light emitted by the CO2 laser is attenuated and coupled into the hollow fiber through spatial collimation. Finally, it is detected by the detector after the absorption reaction between the hollow cavity and the gas. Finally, the signal is processed by digital filtering based on LabView and digital dual-phase lock-in amplification. SF6 gas with concentrations of 0.5 ppm, 2.45 ppm, 4.9 ppm, and 9.92 ppm were detected. The experimental results show that the detection limit of the detection system can reach 0.4 ppm, the detection error of the SF6 gas concentration is less than 1 %, and the repeatability test shows that the detection system has high stability.

CFD simulation and design of ceramic hollow fiber membrane stack for oxygen separation

Hollow fiber ceramic membrane technology demonstrates a great potential for high performance oxygen separation from air. Upscaling of single hollow fiber membrane for membrane stacks and modules is necessary toward practical applications. However, experimental methods are very time-consuming and highly cost. Mathematical modeling is a cost-effective technique and very flexible to evaluate different upscaling strategies. In this research, built upon the experimental results of a proof-of-concept hollow fiber membrane stack, a computational fluid dynamics-based Multiphysics stack model is developed and validated. Comprehensive simulations are conducted to understand the behaviors of stacks under different operating conditions. Different designs strategies are also evaluated toward optimizations of stack performance.

PBP-3 directed therapy in VIM-producing Pseudomonas aeruginosa creates bacterial transformers, persisters in disguise

ObjectivesThe proliferation of metallo-β-lactamase (MBL)-producing Pseudomonas aeruginosa represents a significant public health threat. P. aeruginosa undergoes significant phenotypic changes that drastically impair antibiotic efficacy. The objectives of this study were (1) to quantify the time-course of killing of VIM-2-producing P. aeruginosa in response to aztreonam-based therapies (including avibactam for coverage of AmpC), and (2) to document the capacity of P. aeruginosa to undergo morphological transformations that facilitate persistence. MethodsA well-characterised, clinical VIM-2-producing P. aeruginosa was studied in the hollow fibre infection model (HFIM) over 9 days (7 days of active antibiotic therapy, 2 days of treatment withdrawal) at a 107.5 CFU/mL starting inoculum. HFIM treatment arms included: growth control, aztreonam, ceftazidime/avibactam, aztreonam/ceftazidime/avibactam, polymyxin B, and aztreonam/ceftazidime/avibactam/polymyxin B. In addition, real-time imaging studies were conducted under static conditions to determine the time course of the reversion of persister cells. ResultsThere was a pronounced discrepancy between OD620 and bacterial counts obtained from plating methods (hereafter referred to as ‘OD-count discrepancy’). For aztreonam monotherapy, observed counts were 0 CFU/mL by 120 h. Despite this, there was a significant OD-count discrepancy compared with the pre-treatment 0 h. Between therapy withdrawal at 168 h and 216 h, all arms with suppressed counts had regrown to the system-carrying capacity. Real-time imaging of the P. aeruginosa filaments after drug removal showed rapid reversion from a long, filamentous phenotype to many individual rods within 2 h. ConclusionManaging MBL-producing P. aeruginosa requires a multifaceted approach, focused on maximising killing and minimising proliferation of resistant and persistent subpopulations, which will involve eliminating drug-induced phenotypic transformers.

Hollow fiber thin-film composite membrane regulated by macrocyclic polyamine molecules for high performance organic solvent nanofiltration

Organic solvent nanofiltration (OSN) technology has the potential to separate and purify organic solvents in high efficiency. The self-supporting structure and ease scaling-up merit of hollow fiber (HF) type membrane make it an attractive option for OSN application. Nevertheless, low solvent permeance is one of technical limitation in conventional HF OSN membranes due to their excessively dense separation layer and limited free volume. Herein, we propose a straightforward methodology to fabricate HF thin-film composite (TFC) OSN membranes having exceptional solvent permeance and solute rejection. This methodology is conducted through the incorporation of macrocyclic molecules, 1,4,7,10-tetraazacyclododecane (Cyclen), into the aqueous monomer solution of m-Phenylenediamine (MPD) during the interfacial polymerization to modulate the separation layer. In this way, the average pore size of the separation layer could be precisely enlarged and narrowed on a sub-nanometer scale. Consequently, the Cyclen-modulated HF TFC OSN membrane exhibits excellent separation performance, with a pure methanol permeance of 76.7 L m−2 h−1 MPa−1 and a pure ethanol permeance of 26.5 L m−2 h−1 MPa−1, which is nearly 60 % increase compared with the baseline TFC membrane, while the Rhodamine B (RDB) rejection only shows a neglectable decrease from 99.7 % to 99.6 % at optimal fabrication conditions. Furthermore, the optimal membrane exhibits remarkable solvent resistance, withstanding a 35 d immersion in N, N-dimethylformamide (DMF) at room temperature without a significant decline in RDB rejection. Additionally, the optimal membrane shows higher than 99 % rejection for Rifampicin (823 Da), which is considerable potential for applications in the separation and recovery of pharmaceuticals. In summary, incorporating macrocyclic polyamine Cyclen into the polyamide layer is a viable method for regulating the physical structure and strengthening the performance of HF OSN membrane.

Determining stemness and exosome production from nutrient-dependent cells: Influence of the molecular weight cut-off in hollow fiber membrane systems

This study aimed to optimize parameters for cultivating adipose-derived stem cells (ADSCs) in hollow fiber membrane systems. Enhanced ADSC cultivation was achieved in this study by utilizing a higher cell seeding rate (10 mL/min) and fibronectin coating (8 μg/cm²) on the membrane. A pulsatile flow perfusion (30 min on / 3 h off) for 24 h, followed by continuous flow perfusion at a lower rate (<20 mL/min), was employed. Notably, a two-day medium change maintained CD73 expression (79.26 %) compared to scenarios without changes (1.92 %) over eight days. Using a membrane cut-off of 20 kDa and <0.1 μm, a 1.4- and 2.8-fold increase in proliferated cells was observed; however, CD73 expression decreased by 10.07 and 33.63 %, respectively. The membrane with a pore size of <0.1 μm exhibited 1.4-fold higher exosome particle numbers. In conclusion, nutrient supplementation emerged as crucial for optimal ADSC cultivation in hollow fiber systems.

Flexible and Thermally Insulating Porous Materials Utilizing Hollow Double-Shell Polymer Fibers.

The global climate change is mainly caused by carbon dioxide (CO2) emissions. To help reduce CO2 emissions and conserve thermal energy, sustainable materials based on flexible thermal insulation are developed to minimize heat flux, drawing inspiration from natural systems such as polar bear hairs. The unique structure of hollow double-shell fibers makes it possible to achieve low thermal conductivity in the material while retaining exceptional elasticity, allowing it to adapt to insulation systems of any shape. The layered system of porous mats reaches a thermal conductivity coefficient of 0.031 W∙m⁻¹∙K⁻¹ and enables to reduce the heat transfer. The results achieved using scanning thermal microscopy (SThM) correlate with the simulated heat flow in the case of individual fibers. This research study brings new insights into the energy efficiency of domestic environments, thereby addressing the growing demand for sustainable and high-performance insulation materials for saving energy loss and reducing pollution footprint.

Application of Membrane Bioreactor (MBR) for Antibiotic Elimination From Wastewater

In this study, a membrane bioreactor – MBR system at laboratory-scale was designed to remove sulfamethoxazole (SMX) in water. The system consists of a 8-liter aerobic tank combined with a hollow fiber micro filtration membrane (MF). Influent flow rate of wastewater was 15,84 L/day. Affecting factors to treatment efficiencies (organic pollutants and antibiotics) such as contact time and initial antibiotic concentration were investigated. Experimental results indicated that wastewater with initial parameters COD, NH4+, NO3-, PO43- were respectively 240, 9,4, 37,5, 6,3 mg/L, the treatment efficiencies achieved were respectively at 63,4, 89,7, 78,1, and 79,8%. The removal efficiencies of the wastewater containing SMX (concentrations range from 0,052 to 0,268 mg/L) for COD and NH4+ decreased by 4,2 and10,9% respectively, and for NO3- and PO43- increased by about 4,5 and 7,9%, correspondingly. Overall SMX elimination performance is about 49,7%.

Retraction Note: Hollow fiber membrane contactor based carbon dioxide absorption − stripping: a review

Retraction Note: Hollow fiber membrane contactor based carbon dioxide absorption − stripping: a review

Experimental study on the mass transfer permeability of hollow fiber membranes for a humidifier in a proton exchange membrane fuel cell

A membrane humidifier is a device used to increase proton conductivity in a fuel cell system, enhancing the performance and longevity of the fuel cell. In this study, a hollow fiber membrane is tested under various operating conditions to determine the membrane humidifier performance by estimating the amount of water vapor through the membrane. The results show that the mass transfer rate increases with increasing temperature, flow rate, and relative humidity while it decreases with pressure and membrane thickness. Particularly, temperature affects the mass transfer rate the most. When the temperature is increased from 50°C to 80°C, the performance improves by approximately 4.5 times. In contrast, the flow rate affects it the least; an approximately 2.5 times increase in the flow rate results in a 16% improvement in performance. Furthermore, the counterflow consistently exhibits greater efficiency than the co-flow. Moreover, the water vapor permeability through the membrane is assessed. The membrane permeability increases with decreasing membrane thickness and pressure and increasing temperature and inlet relative humidity. The findings indicate that 1°C rise in temperature leads to an increase of approximately 5% in permeability and approximately 19% increase in pressure, resulting in an approximately 15% decrease in permeability.

Improved Synthesis of Hollow Fiber SSZ‐13 Zeolite Membranes for High‐Pressure CO2/CH4 Separation

AbstractHigh‐silica CHA zeolite membranes are highly desired for natural gas upgrading because of their separation performance in combination with superior mechanical and chemical stability. However, the narrow synthesis condition range significantly constrains scale‐up preparation. Herein, we propose a facile interzeolite conversion approach using the FAU zeolite to prepare SSZ‐13 zeolite seeds, featuring a shorter induction and a longer crystallization period of the membrane synthesis on hollow fiber substrates. The membrane thickness was constant at ~3 μm over a wide span of synthesis time (24‐96 h), while the selectivity (separation efficiency) was easily improved by extending the synthesis time without compromising permeance (throughput). At 0.2 MPa feed pressure and 303 K, the membranes showed an average CO2 permeance of (5.2±0.5)×10−7 mol m−2 s−1 Pa−1 (1530 GPU), with an average CO2/CH4 mixture selectivity of 143±7. Minimal defects ensure a high selectivity of 126 with a CO2 permeation flux of 0.4 mol m−2 s−1 at 6.1 MPa feed pressure, far surpassing requirements for industrial applications. The feasibility for successful scale‐up of our approach was further demonstrated by the batch synthesis of 40 cm‐long hollow fiber SSZ‐13 zeolite membranes exhibiting CO2/CH4 mixture selectivity up to 400 (0.2 MPa feed pressure and 303 K) without using sweep gas.

Highly permeable carbon nanotube membranes for efficient surface water treatment through separation and adsorption–electrochemical regeneration

Membrane-based processes feature many advantages for surface water treatment over other technologies; however, the trade-off between membrane selectivity and permeability usually results in the failure to obtain high-quality filtrate at a high permeance. In this study, we report a highly permeable sodium alginate/glutaraldehyde cross-linked carbon nanotube (CNT/SA-GA) membrane with high adsorption ability for surface water treatment. The CNT/SA-GA membranes have a well-formed hollow fiber morphology and good conductivity of 166–261 S/m. They could reject >98 % of large-sized molecules (e.g., Alcian Blue 8GX and Congo Red) at high permeances of 137–227 L/(m2·h·bar). Moreover, they could remove ~100 % of smaller molecules (e.g., Rhodamine B (RhB)) through dynamic adsorption with a capacity of ~57.3 mg/g. Benefiting from their good conductivity, the CNT/SA-GA membranes could easily decompose the pollutants after adsorption saturation through electrochemical oxidation and then regenerated themselves. Though the switch between adsorption and electrochemical oxidation (2.0 V), the CNT/SA-GA membranes could remove ~100 % RhB at a high permeance of 342 L/(m2·h·bar), which is one order of magnitude higher than those of nanofiltration membranes. When used for surface water treatment, the CNT/SA-GA membranes exhibited a much higher TOC removal rate than commercial poly(acrylonitrile) (PAN) membranes (56.2 % vs. 7.2 %). LC-MS/MS analysis showed that many small molecules such as caffeine could be effectively removed by the CNT/SA-GA membranes. In addition, they exhibited a higher fouling resistance than PAN membranes, evidenced by their lower permeance decline ratio (10.1 % vs. 43.7 %). This study will promote the development and applications of the CNT-based membranes for water purification.

Improved Synthesis of Hollow Fiber SSZ-13 Zeolite Membranes for High-Pressure CO2/CH4 Separation.

High-silica CHA zeolite membranes are highly desired for natural gas upgrading because of their separation performance in combination with superior mechanical and chemical stability. However, the narrow synthesis condition range significantly constrains scale-up preparation. Herein, we propose a facile interzeolite conversion approach using the FAU zeolite to prepare SSZ-13 zeolite seeds, featuring a shorter induction and a longer crystallization period of the membrane synthesis on hollow fiber substrates. The membrane thickness was constant at ~3 μm over a wide span of synthesis time (24-96 h), while the selectivity (separation efficiency) was easily improved by extending the synthesis time without compromising permeance (throughput). At 0.2 MPa feed pressure and 303 K, the membranes showed an average CO2 permeance of (5.2±0.5)×10-7 mol m-2 s-1 Pa-1 (1530 GPU), with an average CO2/CH4 mixture selectivity of 143±7. Minimal defects ensure a high selectivity of 126 with a CO2 permeation flux of 0.4 mol m-2 s-1 at 6.1 MPa feed pressure, far surpassing requirements for industrial applications. The feasibility for successful scale-up of our approach was further demonstrated by the batch synthesis of 40 cm-long hollow fiber SSZ-13 zeolite membranes exhibiting CO2/CH4 mixture selectivity up to 400 (0.2 MPa feed pressure and 303 K) without using sweep gas.

Two-photon pumped random lasing in MAPbBr3 with directional output for far-field applications

We investigate the random lasing properties of polycrystalline MAPbBr3 grown in a hollow fiber. Coupling of the random lasing on the inner wall of the hollow fiber into the annular cylinder and guided by the inner surface of hollow cavity enable directional output of the random lasing emission. The polycrystalline MAPbBr3 was grown by the capillary effect, when one end of the hollow fiber was dipped into the precursor solution. A two-photon pumping scheme was employed, where femtosecond pulses centered at about 800 nm was focused onto the MAPbBr3 polycrystals through the side wall of the hollow fiber. Random lasing was achieved due to the strong optical scattering by the interfaces within the polycrystals on the inner wall of the hollow fiber. The random lasing output was re-collimated into a roughly parallel beam with a circular transverse mode, which favors far-field applications of random lasers. Two-photon pumping enables larger penetration depth and larger excitation volume than single-photon pumping, so that strong lasing spot can also be observed in the center area of the output laser beam.

An Insight of TiO2 and Spent Bleaching Earth (SBE) Effect of Phase Crystalline Structures for PVDF Hollow Fiber Membrane

Abstract: Polyvinylidene fluoride (PVDF) hollow fiber membranes have excellent mechanical properties and chemical stability. However, their hydrophobicity can lead to fouling and hinder permeability. Modifying this hydrophobicity is challenging due to PVDF's complex polymorphous structures, with the β-phase offering superior fouling resistance. One approach to improve PVDF hollow fiber membranes is the addition of inorganic additive materials to reduce hydrophobicity. The objective of this study is to offer new insights into the preparation of PVDF hollow fiber membranes using wet spinning with various additives, such as TiO2 and SBE. The investigation focused on the functional groups of PVDF in both the α and β phases. The membrane was fabricated using regenerated SBE and TiO2, which were incorporated through dope solution preparation and phase inversion through a wet spinning technique. The study used the Fourier Transform Infrared (FTIR) technique to characterize the PVDF hollow fiber membranes. The study found that the PVDF hollow fiber membranes exhibit differences in α and β phase crystalline structures when combined with various additives. The addition of SBE to PVDF hollow fiber membranes results in a dominant β-phase crystalline structure, as indicated by the relative fraction of 0.70 and the largest peak area of 2.27. This has successfully improved the hydrophilic properties of the PVDF-SBE hollow fiber membrane.Abstrak: Membran hollow fiber polyvinylidene fluoride (PVDF) memiliki sifat mekanik dan stabilitas kimia yang sangat baik. Namun, sifat hidrofobiknya dapat menyebabkan fouling dan menurunkan permeabilitas membran. Oleh karena itu memodifikasi sifat hidrofobisitas ini cukup menantang karena struktur polimorf PVDF yang kompleks, terutama dengan keberadaan fase β yang memberikan ketahanan terhadap fouling. Salah satu pendekatan yang dapat dilakukan untuk meningkatkan membran hollow fiber PVDF adalah dengan penambahan bahan aditif anorganik untuk mengurangi hidrofobisitas. Tujuan dari penelitian ini adalah untuk menguak wawasan baru dalam pembuatan membran serat berongga PVDF menggunakan wet spinning dengan berbagai aditif, seperti TiO2 dan SBE. Investigasi difokuskan pada gugus fungsional PVDF berupa fase α dan β. Membran dibuat dengan menggunakan TiO2 dan SBE regenerasi, yang dibuat melalui pembuatan larutan dope dan inversi fasa melalui metode wet spinning. Penelitian ini menggunakan teknik Fourier Transform Infrared (FTIR) untuk mengkarakterisasi membran serat berongga PVDF. Penelitian ini menemukan bahwa membran serat berongga PVDF menunjukkan perbedaan struktur kristal fase α dan β ketika dikombinasikan dengan berbagai aditif. Penambahan SBE pada membran serat berongga PVDF menghasilkan struktur kristal fase β yang dominan, seperti yang ditunjukkan oleh fraksi relatif 0,70 dan area puncak terbesar 2,27. Hal ini telah berhasil meningkatkan sifat hidrofilik membran serat berongga PVDF-SBE.

Bridging papermaking and hydrogel production: Nanoparticle-loaded cellulosic hollow fibers with pitted walls as skeleton materials for multifunctional electromagnetic hydrogels

Electromagnetic hydrogels have attracted significant attention due to their vast potential in soft robotics, biomedical engineering, and energy harvesting. To facilitate future commercialization via large-scale industrial processes, we present a facile concept that utilizes the specialized knowledge of papermaking to fabricate hydrogels with multifunctional electromagnetic properties. The principles of papermaking wet end chemistry, which involves the handling of interactions among cellulosic fibers, fines, polymeric additives, and other components in aqueous systems, serves as a key foundation for this concept. Notably, based on these principles, the versatile use of chemical additives in combination with cellulosic materials enables the tailored design of various products. Our methodology exploits the unique hierarchically pitted and hollow tube-like structures of papermaking grade cellulosic fibers with discernible pits, enabling the incorporation of magnetite nanoparticles through lumen loading. By combining microscale softwood-derived cellulosic fibers with additives, we achieve dynamic covalent interactions that transform the cellulosic fiber slurry into an impressive hydrogel. The cellulosic fibers act as a skeleton, providing structural support within the hydrogel framework and facilitating the dispersion of nanoparticles. In accordance with our concept, the typical hydrogel exhibits combined attributes, including electrical conductivity, self-healing properties, pH responsiveness, and dynamic rheologic behavior. Our approach not only yields hydrogels with interesting properties but also aligns with the forefront of advanced cellulosic material applications. These materials hold the promise in remote strain sensing devices, electromagnetic navigation systems, contactless toys, and flexible electronic devices. The concept and findings of the current work may shed light on materials innovation based on traditional pulp and paper processes. Furthermore, the facile processes involved in hydrogel formation can serve as valuable tools for chemistry and materials education, providing easy demonstrations of principles for university students at different levels.

Surface Modification of PVDF and PTFE Hollow Fiber Membranes for Enhanced Nitrogen Removal in a Membrane-Aerated Biofilm Reactor

Surface Modification of PVDF and PTFE Hollow Fiber Membranes for Enhanced Nitrogen Removal in a Membrane-Aerated Biofilm Reactor

Hollow carbon fiber wrapped by regular rGO wave-like folds for efficient solar driven interfacial water steam generation

Efficient seawater desalination is an effective way to solve the shortages of fresh water and energy but with limitations of the low fresh water production rate and high cost. Here, a hollow carbon fiber (HCF) wrapped by regular reduced graphene oxide (rGO) wave-like folds (rGO@HCF) is prepared on account of the differences in thermal shrinkage performance between graphene oxide (GO) and willow catkins fiber. Under one sun irradiation (1 kW m−2), the dry and wet surface temperature of the resulting evaporator reached up to 119.1 °C and 61.7 °C, respectively, and the water steam production rate reached 3.42 kg m−2 h−1. Also, for the outdoor experiment, the rGO@HCF exhibits good evaporator performance which reach up 27.8 kg m−2 day−1. Additionally, rGO@HCF also shows good seawater desalination performance and excellent durability for longtime work. DSC results indicate that the evaporation enthalpy of bulk water and adsorbed water decreased from 2503.92 to 1020.54 J g−1. The excellent evaporating performance is mainly attributed to the regular wave-like microstructure surface of the HCF, which can enhance the light absorption, reduced the vaporization enthalpy of the adsorption water. The findings not only introduce a novel approach for agricultural utilization, but also establish a crucial theoretical foundation for the design of regular wave-like microstructures.

Development of ceramic hollow fiber from recycled quarry dust: exploring its properties as a support for ZIF-8 membrane in gas separation

Development of ceramic hollow fiber from recycled quarry dust: exploring its properties as a support for ZIF-8 membrane in gas separation

Design and fabrication of PPTA-braid-reinforced PFA/GE hollow fiber composite membranes

Due to the effects of the rapid development of modern society and fresh water resource pollution, water shortage has further accelerated, which is becoming a very urgent problem. Herein, the poly (p-phenylene terephthalamide)-(PPTA-) braid-reinforced (PBR) poly(tetrafluoroethylene-co-perfluoropropylvinylether)/graphene (PFA/GE) hollow fiber composite membranes (HFCMs) were prepared by dipping coating-thermal sintering coupling technique with a green process. GE is an emerging type of two-dimensional functional nanoparticle with a tunable passageway for oil molecules. The influences of the GE concentration in the casting solution on the structure and performance of the PBR−PFA/GE HFCMs were investigated. The results showed that the addition of GE produced a finger-like pore structure suitable for oil channels. Meanwhile, the roughness and contact angle of the composite membrane increased accordingly, and the water contact angle increased from 115° to 120°. The permeation fluxes of kerosene also increased obviously with the increase of GE contents, and the maximum flux of M-3 reached as high as 217.66 L·m−2·h−1. The application of the lubricating oil flux test under working conditions of 60–150 °C has demonstrated the high-temperature oil permeability resistance of the composite membrane. Even after long-term use, its separation efficiency for water-in-oil emulsions still remains above 99.5 %. In addition, the membrane separation-efficiency both up to 99.9 % for activated carbon and silica dioxide (SiO2) in kerosene. Overall, the PBR-PFA/GE HFCMs with excellent lipophilicity presented great potential for oily wastewater treatment at high temperatures.

Multi-objective optimization of solar-driven hollow fiber membrane dehumidification system based on MOPSO

The solar-driven hollow fiber membrane dehumidification (SHFMD) system is a renewable, energy-saving, and highly effective dehumidification system. It provides an effective solution to the problem of air-entrained liquid droplets during the traditional solution dehumidification process. The system's mathematical model was established and the reliability of the mathematical model was verified by experimental data. To enhance the comprehensive performance of the system, the multi-objective particle swarm optimization (MOPSO) algorithm is used in this paper to optimize the multi-objective parameters of the system. The objective function is the total exergy destruction of the system and the dehumidification capacity of the system. The optimization variables are cold water temperature, cold water flow rate, solution flow rate, air flow rate, and hot water flow rate. The optimization is performed using the multi-objective particle swarm optimization (MOPSO) algorithm to obtain the Pareto front, and the points of the Pareto front are normalized. Finally, the optimal trade-off point of the Pareto frontier is obtained. Each operating parameter of the optimal point of the Pareto front is also analyzed. The results show that the air flow rate and cold water flow rate have the most influence on the conflict between the total exergy destruction of the system and the dehumidification capacity of the system.