Search Results (451)

Background: Viral vectors are indispensable tools in gene therapy and neural circuit mapping, offering promising therapeutic strategies for diverse genetic diseases and advancing neuroscience research. To achieve high transduction efficiency while mitigating impurity-induced immunogenicity, the development of viral vectors with improved purity and quality is essential. However, this critical requirement is often unmet by conventional purification methods such as ultracentrifugation, which are time-consuming and frequently result in limited product purity. The pseudorabies virus (PRV) is extensively employed as a viral tool for mapping neural circuits, where improved purity contributes to enhanced accuracy of neural tracing. PRV531 is a retrograde trans-synaptic tracer modified from the PRV Bartha strain, specifically designed to facilitate the precise visualization of hierarchical neural networks. Methods: In this study, we developed a method for the concentration and purification of PRV531 by integrating hollow fiber ultrafiltration (HF) with Capto^TM Core 700 (CC700) chromatography. Initially, to concentrate the viral supernatant, a 500 kDa HF membrane was employed, maintaining a feed flow rate of 80 mL/min, a shear rate ranging from 2000 to 6000 s⁻¹, and a transmembrane pressure (TMP) between 0.5 and 1 bar. Following concentration, the virus underwent purification through CC700 chromatography, operating at linear flow rates ranging from 100 to 300 cm/h. Results: Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) revealed distinct bands consistent with the expected sizes of major PRV structural proteins, each with molecular weights ranging from 25 kDa to 150 kDa, concurrently demonstrating a substantial reduction in host cell proteins (HCPs) contamination. The purified PRV531 achieved a high final infectious titer of 3.55 × 10⁹ PFU/mL, with an overall functional virus recovery of 8.88% from the crude supernatant to the final product. Conclusion: These data demonstrate that TFF combined with CC700 resin can efficiently purify retrograde trans-synaptic PRV tracer. Furthermore, this approach provides a promising strategy for purifying other viral-based tracers that traditionally rely on conventional centrifugation methods. Full article

Membrane distillation (MD) is a promising technology for high-salinity water treatment, but scaling still remains a critical limitation to stable operation. This study introduces a novel approach by exploring vibration signal design as a control variable for scaling mitigation in hollow-fiber DCMD, shifting from the conventional treatment of vibration as a fixed-frequency mechanical input. The influence of different vibration modes, including fixed, random, and patterned (music-derived structured non-stationary excitation) vibrations, on CaSO₄ scaling in hollow-fiber direct contact membrane distillation (DCMD) was systematically investigated. Bench-scale experiments were conducted using synthetic saline feed (35,000 mg/L NaCl and 2000 mg/L CaSO₄) under both outside-in and inside-out configurations. The results reveal that vibration modifies flux decline behavior by delaying the critical volume concentration factor (VCF_cr) and reducing post-critical scaling kinetics. In the outside-in mode, patterned vibration achieved the highest critical VCF (3.39) and lowest scale formation rate, indicating effective suppression of nucleation and crystal growth. In contrast, fixed-frequency vibration (100 Hz) was more effective in the inside-out mode, owing to resonance-induced amplification of vibration transmissibility (>140%), which enhanced local shear at the membrane surface. Spectral analysis shows that patterned vibration provides broadband and non-stationary excitation with multiple dominant frequencies, enabling continuous disruption of scaling processes, whereas random vibration lacks structured energy distribution. Furthermore, patterned vibration reduced energy consumption by 16–23% compared to fixed and random modes while maintaining comparable or superior fouling mitigation. These findings demonstrate that vibration pattern design, coupled with system resonance characteristics, is a key factor in optimizing MD performance and energy efficiency. Full article

Micro-nanobubbles (MNBs) aeration has been widely reported as an effective approach for membrane fouling mitigation. However, their optimal operation in polymeric hollow fiber membrane (HFM) systems remains unclear. In this study, the antifouling performance of MNB-assisted ultrafiltration was systematically investigated using a PVDF-HFM, with particular emphasis on release pressure and intermittent aeration strategy. Increasing the release pressure to 0.60 MPa produced smaller and more concentrated bubbles, significantly alleviating membrane fouling. A distinct intermittent-aeration window was observed, in which a 15 min interval achieved the best overall performance, with a rejection efficiency of 75% and a cleaning efficiency of 93%, approaching that of continuous aeration. Longer intervals resulted in rapid deterioration in fouling control, indicating insufficient bubble replenishment. Compared with continuous operation, the optimized intermittent mode maintained comparable membrane performance while reducing energy consumption by approximately 50%, demonstrating a clear advantage in energy efficiency. Importantly, the optimal intermittent interval for PVDF-HFM (15 min) differs from that reported for ceramic membranes (30 min), highlighting that the performance of intermittent MNB aeration is not universal but strongly dependent on membrane properties. This shift in optimal interval is attributed to differences in surface wettability, structural flexibility, and local hydrodynamic conditions, which collectively influence bubble retention, interfacial shielding, and foulant detachment. Full article

Biogas upgrading to biomethane is an important route for increasing the energy value of renewable gas streams and enabling their wider use in fuel, heat, and power applications. In the present study, a two-stage membrane process for biogas upgrading was developed and validated using polysulfone (PSF) and polyetherimide (PEI) hollow-fiber membranes. The main original aspects of this work include the formulation of a PEI/DMF/IPA spinning dope composition (27/60/13 wt.%), the mixed-gas testing of PSF and PEI hollow-fiber membranes in a six-component model biogas mixture, and the combined simulation, experimental validation, and techno-economic evaluation of a two-stage membrane process. Mixed-gas permeation experiments with a six-component model biogas mixture were used as the basis for process simulation of four membrane-stage configurations. Only the PSF + PEI cascade simultaneously provided methane recovery above 90%, methane concentration in the product above 95 mol.%, and residual carbon dioxide content below 2 mol.%. Experimental verification confirmed the modeled process concept and demonstrated that the target biomethane quality was achieved at feed flow rates of 0.9–1.1 L min⁻¹, where methane recovery reached 93.5–95.2% and methane purity was 95.5–96.2 mol.%. A preliminary techno-economic analysis for a 100 m³ h⁻¹ unit indicated an upgrading penalty of USD 96.4 per ton of 95.5 mol.% CH₄. PSF membranes provided higher carbon dioxide permeance, whereas PEI membranes exhibited higher CO₂/CH₄ selectivity, which explains the efficiency of their combination in the two-stage scheme. The results show that the proposed PSF + PEI cascade is a promising membrane-based approach for energy-efficient biogas upgrading. Full article

This paper describes a simple and sensitive method for determining the content of five bisphenols at the µg L⁻¹ level in tea infusion samples. The procedure uses a polypropylene hollow fiber filled with a deep eutectic solvent as the acceptor phase and 1-octanol as the supported liquid membrane, and the optimal conditions for the three-phase stir bar microextraction method were established as follows: a menthol–octanoic acid mixture (1:1 molar ratio) as the hollow-fiber filling, an extraction time of 1 h, and 80 µL of methanol for analyte desorption. The method demonstrated good linearity over the ranges of 1.5–30.0 µg L⁻¹ (BPF, BPA, BPAF, and BADGE) and 6.0–120.0 µg L⁻¹ (BPZ), with limits of detection between 0.28 and 1.01 µg L⁻¹, and the relative recovery values were satisfactory (99–120%) with acceptable precision (RSD < 17%). Thus, the method was successfully applied to quantitatively analyze twenty commercial tea infusions, in which BPF was detected at concentrations above the LOQ, and the greenness and overall applicability of the approach were confirmed using the AGREEprep and BAGI assessment tools. Full article

Perovskite mixed proton–electron hydrogen-permeable membranes have been widely applied in the field of membrane separation due to their 100% selectivity for hydrogen separation. La_5.5WO_11.25-δ-La_0.87Sr_0.13CrO_3-δ (LWO-LSF) four-channel hollow fiber membranes were prepared by the phase inversion and sintering technique using a one-step thermal processing (OSTP) approach. The effects of temperature, feed gas concentration, sweep gas flow, permeation mode, and water vapor on hydrogen flux were systematically investigated. At 900 °C, the hydrogen permeation flux of 50% H₂/N₂ feed from the shell side to the lumen side was 0.613 mL·min⁻¹·cm⁻², which was 62.59% higher than that from the lumen side to the shell side. The enhanced hydrogen permeation performance is attributed to the lower gas mass transfer resistance under shell-side feeding. Under humidified conditions on the sweep side, the hydrogen flux increased by an additional 3.42%. The presence of water vapor increased the number of proton carriers, effectively enhancing proton–electron-coupled transport and thereby increasing the hydrogen permeation flux. Full article

Hybrid gas separation technologies combining different physicochemical mechanisms represent a promising approach for the efficient treatment of complex natural gas mixtures. In this work, a hybrid process integrating gas hydrate crystallization and membrane gas separation was investigated for the upgrading of multicomponent natural gas-containing hydrocarbons (C₁–C₄), acid gases (CO₂ and H₂S), and inert components. Polysulfone hollow-fiber membranes were fabricated, and their gas transport properties were experimentally determined using an eight-component quasi-real natural gas mixture under elevated pressure conditions. The obtained mixed-gas permeance values were used as input parameters for the development of a detailed mathematical model of a hollow-fiber membrane module implemented in the Aspen Custom Modeler. The model was applied to simulate membrane separation of both gas- and hydrate-derived streams produced by the gas hydrate crystallizer. Simulation results were analyzed in terms of hydrocarbon composition, acid gas removal efficiency, and hydrocarbon recovery as a function of the stage-cut. The modeling predictions were validated experimentally using a laboratory membrane module integrated with the gas hydrate crystallization unit. Good agreement between the experimental data and simulation results was observed for all major components. The deviation between modeled and experimental concentrations remained small, while the discrepancy in hydrocarbon recovery was higher and reached approximately 10–20%, which is attributed to the cumulative uncertainty of flow rate and composition measurements. These results confirm the adequacy of the developed model. The hybrid process demonstrates strong complementarity between the thermodynamic selectivity of hydrate formation and the transport selectivity of membrane separation, enabling efficient removal of acid gases while maintaining acceptable hydrocarbon recovery. The results indicate that the proposed gas hydrate–membrane hybrid process is a promising strategy for advanced natural gas purification and upgrading. Full article

Direct ocean carbon capture (DOC) has emerged as a promising strategy for mitigating atmospheric CO₂ levels and addressing ocean acidification. Unlike direct air carbon capture methods, DOC leverages the ocean’s vast carbon storage capacity, offering a scalable and efficient route for carbon dioxide removal. This systematic comparative review categorizes existing DOC methods into three types: (1) biological carbon capture, which relies on photosynthesis by microalgae and marine microorganisms; (2) electrochemical carbon capture, which utilizes water electrolysis to generate H⁺ and OH⁻ ions for pH-driven CO₂ removal; and (3) physical carbon capture, which employs hollow fiber membranes to directly separate CO₂ from seawater. For each technology, we evaluate efficiency, energy consumption, cost, technology readiness level (TRL), scalability, and major challenges. By integrating recent pilot data and providing a critical assessment, this review offers a roadmap for future research in direct seawater CO₂ capture. The comparative analysis reveals that electrochemical methods achieve the highest efficiency (60–85%) but face membrane fouling and electrode degradation challenges, while biological methods offer low-energy operation but suffer from slow kinetics and high harvesting costs, and membrane-based methods provide high removal rates (up to 94%) but require improved fouling resistance. Full article

Robust numerical frameworks are essential for the simulation, design, monitoring, and control of membrane-based separation units, particularly under highly nonlinear and industrially relevant operating conditions. In this context, a comprehensive phenomenological and numerical framework is proposed for the simulation of hollow-fiber membrane modules, incorporating coupled mass, momentum (through pressure drop), and energy transport equations. The governing equations are discretized using a rigorous orthogonal collocation formulation, and the performances of two numerical solution strategies are systematically investigated for the first time to allow the in-line and real-time implementation of the model: a steady-state approach based on the Newton–Raphson method with careful treatment of initial estimates, and a pseudotransient formulation. Particularly, an original and consistent numerical treatment is introduced for the energy balance at boundaries where the permeate flow vanishes, enabling the stable incorporation of thermal effects and Joule–Thomson phenomena. The results clearly show that the steady-state Newton–Raphson approach provides the best overall performance in terms of computational efficiency, numerical robustness, and accuracy when physically consistent initial profiles are employed. In particular, the combination of a linear initial guess and a numerical mesh constituted of four collocation points yielded the most favorable balance between convergence speed, numerical robustness, and accuracy for the base-case sensitivity analysis. For monitoring-oriented applications, the numerical choice should be weighted primarily toward computational performance once physical consistency and convergence criteria are satisfied, rather than toward maximum mesh-refinement accuracy. In this context, small differences in internal-fiber profiles can be compensated through real-time permeance estimation and are negligible when compared with measurement uncertainty in real industrial processes. Under extreme operating conditions involving low concentrations, low flow rates, and highly permeable species, the pseudotransient formulation proved to be a reliable auxiliary strategy, enabling robust convergence when suitable initial guesses were not readily available. The proposed framework is validated against experimental data from the literature and subjected to extensive convergence and sensitivity analyses, providing a reliable basis for simulation and for assessing computational feasibility in in-line and real-time monitoring-oriented applications. A full demonstration of digital-twin integration, online parameter updating, reduced-order coupling, and closed-loop control is beyond the scope of the present study and will be addressed in future work. Full article

The high-temperature proton ceramic membranes with simultaneous separation of hydrogen and oxygen exhibit promising applications in the catalytic conversion field. However, their separation performance often relies on external electrical circuits, which limits practical application. To overcome this limitation, doping strategies have emerged as a viable approach to develop triple-conducting (H⁺/e⁻/O²⁻) membranes for simultaneous hydrogen and oxygen separation in non-electrochemical mode. In this study, honeycomb-structured hollow fiber membranes were fabricated, and the effects of varying Fe³⁺ and Y³⁺ doping concentrations on hydrogen and oxygen permeation fluxes were systematically investigated. At the Fe³⁺ doping level of 0.2 mol, the oxygen permeation flux of 0.692 mL min⁻¹ cm⁻² in BaCe_0.6Zr_0.2Fe_0.2O_3−δ (BCZF) was achieved at 1000 °C, while the hydrogen permeation flux was 0.201 mL min⁻¹ cm⁻². The BaCe_0.55 Fe_0.05Zr_0.2Y_0.2O_3−δ (Fe-BCZY) hollow fiber membrane can enhance the hydrogen permeation flux by 75% at 1000 °C. Furthermore, during the simultaneous permeation of hydrogen and oxygen, a 1.7-fold enhancement in hydrogen permeation performance was achieved for the Fe-BZCY hollow fiber membrane at 1000 °C, and with oxygen permeation flux of 1.76 mL min⁻¹ cm⁻² at the same temperature. More significantly, a hydrogen permeation flux of 0.34 mL min⁻¹ cm⁻² can be achieved at 700 °C under simultaneous hydrogen and oxygen permeation, which is favorable for the application of membrane reactors in catalytic reactions. Full article

The efficient removal of dyes and separation from dissolved salts are crucial for the recovery of valuable resources from saline textile wastewater. In this study, hollow fiber membranes were fabricated using the non-solvent-induced phase separation (NIPS) method and then improved with a dual-coating process to create effective nanofiltration (NF) membranes. First, hollow fiber substrates with Fe³⁺ were fabricated using NIPS. Subsequently, the inner surface of the membrane was coated with phytic acid (PA) and polyethyleneimine (PEI), which increased the thickness of the separation layer and reduced the size of the surface pores, thereby improving the separation efficiency. The loose NF membrane exhibited superior water permeance (pure water permeability of 280 L·m⁻²·h⁻¹·bar⁻¹) and, with dye rejection rates consistently exceeding 95%, also remarkable dye/salt selectivity (with separation factors of CR/NaCl: 64.08, CR/Na₂SO₄: 21.21, CBB/NaCl: 14.75, and CBB/Na₂SO₄: 10.74). The flux recovery of the membrane was over 80% for humic acid, and the membrane exhibited favorable stability under acidic and alkaline conditions, confirming its excellent antifouling and stability performance. In conclusion, this study presents a straightforward and effective approach for fabricating hollow fiber loose NF membranes, underscoring their potential for treating hypersaline wastewater and resource recovery. Full article

Polyetherimide (Ultem-1000) hollow-fiber membranes were developed for biogas purification with emphasis on the relationship between spinning conditions, membrane morphology, gas transport properties, and module performance. Hollow fibers were prepared from dope solutions based on dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP) at different conditions, followed by post-treatment with 1 and 3 wt.% silicone solution in n-heptane to reduce nonselective defects and improve selectivity toward the intrinsic behavior of dense PEI films. SEM analysis revealed that DMF-based fibers formed a more open, macrovoid-rich structure, whereas NMP-based fibers exhibited a more homogeneous sponge-like morphology with a better-defined selective layer. DMF-based fibers experienced faster demixing, which promoted macrovoid formation, increased pore connectivity of the substructure, lowered mass transfer resistance, and at the same time increased the probability of nonselective pathways and defect-related loss of selectivity. This structural evolution was reflected in gas transport properties: untreated DMF fibers showed high mixed-gas permeance but limited selectivity, while NMP fibers demonstrated lower permeance and selectivity values closer to those of the dense film. Silicone post-treatment significantly improved separation performance, with 3 wt.% coating being markedly more effective than 1 wt.% coating. The best compromise between permeance and selectivity was achieved for the DMF-based fibers treated with 3 wt.% silicone, which exhibited CO₂ and H₂S permeances of 39.4 and 47.12 GPU, respectively, together with selectivity values of 22.4, 26.8 and 20.2 for CO₂/CH₄, H₂S/CH₄ and CO₂/N₂. A membrane module containing 500 fibers was studied during the quasi-real biogas upgrading. With increasing stage-cut, the CH₄ concentration in the retentate increased from ~74 to 96 mol.%, while CO₂ decreased from ~21 to 2 mol.%. The results demonstrate that structure control combined with silicone post-treatment is an effective strategy for producing PEI hollow fibers suitable for simultaneous methane enrichment and removal of acid impurities from biogas. Full article

Due to the ultra-trace concentrations of perfluoroalkyl compounds (PFCs) existing in environmental aqueous matrices, it is imperative to develop sensitive and high-enrichment-efficiency approaches for the determination of these emerging pollutants. In this study, a nitrogen-doped carbon dot-functionalized hollow fiber membrane (NCDs@HFM) was fabricated and employed in solid-phase microextraction (SPME) mode for the simultaneous identification of eight perfluoroalkyl carboxylates (PFCAs). The NCDs@HFM offers several advantages, including multiple active binding sites, chemical durability, a large specific surface area and environmental compatibility. Owing to these properties, the NCDs@HFM-based SPME demonstrated high extraction efficiency for PFCAs, where enrichment factors for target molecules could reach 35–61 fold under the optimum conditions. This established method was then integrated with liquid chromatography–tandem mass spectrometry (LC-MS/MS) for the qualitative and quantitative analysis of eight representative PFCAs in drinking and environmental water samples. The limits of detection (LODs, S/N = 3) and quantitation (LOQs, S/N = 10) of the method were at the scale of 0.0018–0.015 μg/L and 0.006–0.050 μg/L, respectively. This proposed method exhibited good precision, with RSDs below 13.2% and satisfactory accuracy, with recoveries ranging from 70.6% to 122.5%. The developed method was successfully applied in the identification of eight typical PFCAs in drinking and environmental water samples. This method exhibits several merits, including low cost, high sensitivity, good reliability and reusability, representing a promising alternative for measuring trace levels of PFCAs in aqueous matrices. Full article

Hollow fibers (HFs) have recently gained attention as an advantageous photocatalyst immobilizer for heterogeneous catalysis. Depending on their fabrication method, they can come up, or not, with a porous network within their structure. In this case, they are sometimes referred to as membranes, although they are not applied in liquid flow applications as filters. This work provides a concise overview of all the studies encountered in the literature on photocatalytic hollow fibers (HFs) and hollow fiber membranes (HFMs), clarifying the prevailing confusion about the topic. All publications are categorized with respect to their reported applications in batch liquid, flow, or gas experiments. Full article

The hollow fiber membrane humidification modules are used for indoor humidification in hot–dry regions and heating in winter. The module is composed of several flexible hollow fiber membranes, which are bent and displaced by gravity and fluid forces. This paper is a further study of previous work that reveals the internal relationship between the forces generated by vortex shedding and fiber vibration. The central trajectories of fibers in the flow field are described for various pulsating flow and fiber structure parameters. The effects of fiber displacement on fluid flow, heat transfer, and mass transfer performance at different parameters are discussed. The results show that the fiber displacement in the flow field consists of two components: (i) deformation caused by fluid drag force and gravity and (ii) periodic vibration caused by periodic lift and drag force as vortices shed at the fiber surface. The fiber vibration facilitates the vortex shedding on the fiber surface, which enhances the convective heat and mass transfer performance on the fiber surface. The average friction factor (f_m,v), Nusselt number (Nu_m,v), and Sherwood number (Sh_m,v) increased by 12.9%, 39.3%, and 20.0%, respectively, when the fiber vibrated compared to non-vibration. This implies that inducing fiber vibration can optimize the heat and moisture transfer performance. Full article