Search Results (76)

Counter-current flow in channels separated by a membrane has been studied by several scientists and researchers. The current study aims to analytically simulate and describe the distribution of pressure, volumetric flow rate, and velocity in square channels separated by a membrane. Consequently, the study was conducted using one-dimensional (1D) analytical solutions to achieve several objectives: avoiding the execution of experimental tests, reducing the effort required for expensive and time-consuming module design, and enabling easy observation of variations in pressure, volumetric flow rate, and velocity. The 1D analytical solution directly simulates flow in square channels separated by a membrane by solving the continuity equation and Darcy’s law, through which pressure, volumetric flow rate, and velocity are calculated. Experimental results were used to validate the 1D analytical solutions. The results of the current study indicate that pressure decreases from the inlet to the outlet of the channel, while the horizontal velocity decreases from the inlet to the midpoint of the channel length and then increases toward the outlet. The 1D analytical solutions show acceptable accuracy when compared with experimental results. Consequently, these solutions can be used to explore and illustrate the distributions of pressure, volumetric flow rate, and velocity in square channels separated by a membrane, enabling the evaluation of hemodialysis prototype module performance and efficiency prior to fabrication. Full article

Solid-contact ion-selective electrodes (SC-ISEs) are typically constructed using ion-selective membrane (ISM)-based configurations. However, such structures often suffer from water-layer formation and the weak mechanical stability of the ISM. Herein, we report an ISM-free K⁺-SC-ISE based on a Prussian blue analogue transducer, KMnFe(CN)₆, eliminating the need for a conventional ionophore-based ISM layer. KMnFe(CN)₆ was synthesized via a one-step citrate-assisted co-precipitation method. The material functions as a bifunctional transducer, in which the open framework structure with ion-transport channels enables selective K⁺ recognition, while the redox-active Mn centers facilitate ion-to-electron transduction. The fabricated KMnFe(CN)₆-based K⁺ sensor exhibits a near-Nernstian response with a sensitivity of 52.3 ± 1.0 mV dec⁻¹ and a rapid response time of 25 s. The linear range and limit of detection were determined to 10⁻⁴ to 10⁻¹ M and 5.8 × 10⁻⁵ M, respectively. The sensor also demonstrates selectivity to representative interfering ions, with log K_ij of −2.39 ± 0.12 (Na⁺), −2.86 ± 0.09 (Li⁺), −3.06 ± 0.09 (Ca²⁺), −2.74 ± 0.12 (Mg²⁺) and −0.95 ± 0.08 (NH₄⁺). By eliminating the ISM layer, the water-layer effect is effectively avoided, resulting in excellent long-term stability with a potential drift of 57.2 ± 6.1 μV h⁻¹ over 7 days. The sensor was further applied to the analysis of K⁺ in real lake water samples, where the measured concentration showed good agreement with ion chromatography results. This work provides an ISM-free SC-ISE strategy for ion analysis in water environments. 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

Heavy metal contamination of drinking water remains a persistent global challenge, exacerbated by salinity, industrial discharge, and the limitations of existing membrane technologies that are constrained by permeability–selectivity trade-offs. In this study, we develop a hybrid thin film nanocomposite (TFN) forward osmosis (FO) membrane by incorporating a zirconium-based metal–organic framework (UiO-66) and its conductive polymer-functionalized analogue (PANI@UiO-66) into the polyamide active layer via interfacial polymerization. The incorporation of UiO-66 enhances water transport through the introduction of hydrophilic microporous domains, while the polyaniline coating modulates nanoscale transport pathways and interfacial interactions. Systematic variation in filler type and loading reveals distinct functional roles of the two fillers. Membranes incorporating bare UiO-66 exhibit increased water flux, attributed to facilitated transport through MOF-derived nanochannels, but show a moderate increase in reverse solute flux. In contrast, PANI@UiO-66 incorporation results in reduced water flux but significantly suppresses reverse solute flux and enhances chromium rejection, indicating improved control over selective transport. At an optimal loading of 0.15 wt% (TFN-PU3), the membrane demonstrates an improved balance between water permeability and solute selectivity compared to the pristine thin film composite (TFC) membrane under FO conditions. The observed performance is attributed to the combined effects of modified transport pathways and interfacial interactions introduced by the hybrid filler system. The results highlight the potential of conductive polymer–MOF hybridization as a strategy for tuning membrane performance. This work provides a practical framework for designing TFN membranes for selective heavy-metal removal in saline and complex water environments. Full article

To enhance the functionality of collagen (Coll)-based scaffolds, we developed a double-crosslinking strategy incorporating an electroconductive chitosan (Ch) and polypyrrole (Ppy) composite. Successful pre-crosslinking of Ch and Ppy was achieved using glutaraldehyde (GTA) at 100 µM. This facilitated imine linkage formation, confirmed by FTIR, enabling synergistic integration with Coll and successful nanofiber scaffold fabrication via electrospinning. While increasing the Ch-Ppy-GTA ratio affected the spinning process and higher GTA concentrations compromised fiber homogeneity, all other measured properties generally improved with increasing ratios. Crucially, this methodology allowed the membranes to maintain their morphology and significantly extended their degradation profile up to 20–30 days in PBS medium at 37 °C. Furthermore, the scaffolds exhibited electroactivity characterized by pseudocapacitance in the presence of Na⁺ and Ca²⁺ ions. These findings demonstrate a robust, tunable method for creating electroactive and structurally stable nanofiber scaffolds suitable for advanced tissue engineering. Full article

Several studies have investigated counterflow and concurrent flow in channels separated by a membrane to simulate mass transfer through membranes; however, few of them have used computational fluid dynamics (CFD). The current study aimed to numerically simulate and physically describe the distribution of pressure and velocity in counter-current flow by solving Navier-Stokes (N-S) equations in the channel and membrane pores (vertical channels). This is in contrast to most previous studies, in which the channel flow was simulated using N-S equations while ultra-filtration membrane flow was simulated using Darcy’s law. Consequently, the current study was executed using a CFD simulation to achieve several significant features: avoiding the execution of experimental tests, reducing the effort of model design and the expense and time consumption of fabrication, and facilitating the easy observation of variations in the pressure and the horizontal and vertical velocity for each point in the model. Two-dimensional CFD methods directly simulated the flow in channels and membrane pores to solve the N-S equations for each point in the whole domain, for which the velocity (horizontal and vertical) and pressure were calculated. In the current study, it was found that the pressure decreased from the inlet to the outlet of the channel, the horizontal velocity decreased from the inlet to the middle of the channel length and then increased to the outlet of the channel, and the vertical velocity decreased from the inlet to the middle of the channel length (L/2) with an upward direction (positive) and from L/2 to the outlet of the channel with a downward direction (negative). The analytical solution (1D model) was used to validate a numerical simulation (CFD) for the current study, but there were slight differences in the results between them. The results were perfectly explored and displayed the flow distribution patterns inside the channels and the membrane pores (vertical channels). The current study model represents the hemodialysis process. Full article

Stimuli-responsive liposomal membranes have attracted growing interest as dynamic soft materials capable of regulating permeability, fusion, and cargo release in response to external or internal triggers. By incorporating functional molecular or nanostructured guests, such as photochromic compounds, plasmonic nanoparticles, or ionizable lipids, bilayers can be endowed with reversible and tunable properties. These modifications often rely on the precise control of lipid packing, phase behaviour, and the formation of transient membrane defects that facilitate molecular transport. This review aims to provide an overview of the molecular design strategies and underlying mechanisms used to engineer such responsive liposomal systems, with particular emphasis on light- and heat-triggered behaviours and on supramolecular approaches that modulate membrane structure and dynamics. Emerging trends, current limitations, and opportunities for future development in functional lipid-based materials and biointerfaces will also be discussed. Full article

The demand for effective downstream processing of adeno-associated virus (AAV) is increasing as gene therapies advance toward broader clinical applications. Robust, efficient, and scalable ultrafiltration and diafiltration (UF|DF) operations are essential for generating high-quality AAV preparations, with tangential flow filtration (TFF) serving as a critical unit operation for vector concentration, impurity reduction, and buffer exchange while maintaining viral functionality. Development of TFF processes requires careful consideration of membrane characteristics—including chemistry, pore size or channel architecture—as these parameters directly influence vector retention, fouling behavior, and overall process efficiency. Equally important is the optimization of critical process parameters such as recirculation rate, transmembrane pressure (TMP), and total processing time, all of which govern hydrodynamic performance and product quality. This study assessed two Sartocon^® Hydrosart^® TFF cassette architectures—ECO-Screen and E-Screen—for the ultrafiltration and diafiltration of AAV8 clarified lysate. Through flux characterization and controlled small-scale evaluations, cassette-specific operating regions were defined. Both configurations supported high viral genome retention; however, the E-Screen geometry achieved faster processing and superior removal of host–cell protein and DNA contaminants, whereas the ECO-Screen format allowed for efficient operation under reduced pump rates and, therefore, lower shear conditions. Reproducibility assessments demonstrated minimal run-to-run variability, confirming the robustness of the optimized operating parameters. A 10-fold scale-up further validated the linearity and predictability of the UF|DF process, with consistent impurity-reduction profiles and only modest deviations in viral recovery. Collectively, these findings provide a quantitative basis for rational cassette selection in AAV purification workflows and establish a scalable, scientifically grounded UF|DF framework applicable across development and manufacturing scales. Full article

Rare earth elements (REEs) are increasingly critical for advanced technologies like high-tech electronic devices, electric vehicles, catalysts, and supercapacitors. However, separating and purifying the REEs is challenging due to their similar physicochemical properties, such as ionic sizes and oxidation states. Traditional methods like solvent extraction require extensive use of organic solvents, involving multiple stages that generate large volumes of acidic liquid wastes. This article introduces membrane separation technologies as a more efficient approach that minimizes waste generation and offers higher selectivity and recovery rates in a single step. Membrane separation methods utilize free energy gradients and differences in ionic size or material affinity to selectively reject or allow ion adsorption and diffusion through the membrane pores. In this review paper, we critically evaluate recent advancements in the development and implementation of membrane-based systems and focus on exploring different membrane materials for REE separation, including polymer inclusion membranes, ion-imprinted membranes, nanofiltration membranes, electrodialysis membranes, metal-organic frameworks, and supported liquid membranes. The advantages, potential challenges, and technical issues with implementing these technologies are discussed, and possible areas for improvement and insights for further research are presented. Full article

This study evaluates the partial dealcoholization of red wine using reverse osmosis (ACM3) and nanofiltration (TS80) membranes at 25 and 35 bar, targeting 2% and 4% ethanol reductions. Membrane performance was assessed through fouling analysis and ethanol partitioning, while wine phenolic (flavan-3-ols, anthocyanins) and color characteristics (CIELab parameters) were determined. The 2% reduction process with ACM3 at 25 bar resulted in minimal phenolic changes. The 4% reduction process revealed distinct performance profiles: ACM3 exhibited exceptional stability (3.35–5.30% permeability loss, linear flux decline with R² > 0.93) and ethanol rejection of 17.6–25.5%, while TS80 achieved processing rates three to six times faster with moderate fouling (16.3% loss, 7.7–13.3% rejection). Decreases in flavan-3-ols and anthocyanin concentrations correlated with fouling intensity rather than processing duration. Proanthocyanidin structure remained stable, and color shifts reflected changes in polymeric pigments rather than anthocyanin loss. Reverse osmosis at low transmembrane pressure proved most suitable for quality preservation. The operational trade-off is clear: TS80 offers three to six times faster processing but with greater phenolic loss, while ACM3 requires longer batch times with minimal fouling. Both processes demonstrate that membrane-based dealcoholization without fluid replacement is feasible, providing winemakers with a valuable method to reduce alcohol while preserving quality. Full article

Conversion of carbon dioxide (CO₂) to methanol in a traditional reactor (TR) with catalytic packed bed faces the challenge of lower reactant conversion due to thermodynamic limitations. On the contrary, membrane reactors selectively remove reaction products, enhancing the conversion, but it is still limited, and existing designs face challenges of structural integrity and scale-up complications. Therefore, for the first time, a ceramic membrane microchannel reactor (CMMR) system was developed with 500 µm deep microchannels, incorporated with catalytic membrane for CO₂ conversion to methanol. Computational fluid dynamic (CFD) simulations confirmed the uniform flow distribution among the microchannels. A catalytic LTA zeolite membrane was synthesized with thin layer (~45 µm) of Cu-ZnO-Al₂O₃ catalyst coating and tested at a temperature of 220 °C and 3.0 MPa pressure. The results showed a significantly higher CO₂ conversion of 82%, which is approximately 10 times higher than TR and 3 times higher than equilibrium conversion while 1.5 times higher than conventional tubular membrane reactor. Additionally, methanol selectivity and yield were achieved as 51.6% and 42.3%, respectively. The research outputs showed potential of replacing the current industrial process of methanol synthesis, addressing the Sustainable Development Goals of SDG-7, 9, and 13 for clean energy, industry innovation, and climate action, respectively. Full article

Reverse electrodialysis (RED) enables the efficient conversion of the chemical potential difference between seawater and freshwater into electricity while simultaneously facilitating hydrogen production for integrated energy utilization. Nevertheless, the widespread deployment of RED remains constrained by the reliance on ruthenium–iridium-coated electrodes, which are expensive and resource-limited. This study proposes the adoption of titanium-based redox electrodes as a replacement for traditional precious metal electrodes and employs a novel spike structure to accelerate hydrogen bubble detachment. The electrochemical performance of titanium electrodes in an RED hydrogen production system was systematically evaluated experimentally. The influences of several parameters on the RED system performance were systematically examined under these operating conditions, including the ruthenium–iridium catalytic layer, operating temperature (15 to 45 °C), electrode rinse solution (ERS) concentration (0.1 to 0.7 M), and flow rate (50 to 130 mL·min⁻¹). Experimental results demonstrate that optimized titanium redox electrodes maintain high electrocatalytic activity while significantly reducing system costs. Under optimal conditions, the hydrogen yield of the Ti redox electrode reached 89.7% of that achieved with the mesh titanium plate coated oxide iridium and oxide ruthenium as electrodes, while the electrode cost was reduced by more than 60%. This is also one of the cost-cutting solutions adopted by RED for its development. Full article

Building on our previous study on batch pervaporation membrane reactors for isoamyl acetate synthesis, this work evaluates a two-step continuous process integrating a slurry reactor and a commercial pervaporator module based on a hybrid silica membrane. The system combines catalytic esterification of acetic acid with isoamyl alcohol with simultaneous water removal to enhance conversion and product selectivity. Operating conditions were defined using experimentally validated thermodynamic, kinetic, and mass-transport models. A hydrodynamic assessment confirmed turbulent flow within the membrane module, and model predictions were compared with experimental data for validation. The results confirmed the occurrence of reactive pervaporation and demonstrated that both the membrane area-to-reactor volume ratio and catalyst loading significantly influence the equilibrium shift. Although conversion remained limited by the available membrane area, the commercial pervaporation unit exhibited stable operation, consistent flux behavior, and effective water selectivity. These findings demonstrate the technical feasibility of the continuous slurry reactor–pervaporator configuration and establish a framework for further optimization and scale-up of isoamyl acetate production via reactive pervaporation. Full article

The filtration of microalgae generates fouling through algal matter and exopolymer particles with consequences for the flow rate. Therefore, regeneration that is as complete and continuous as possible is necessary. For this purpose, a commercial membrane with a pore size of 0.8 µm is contaminated with the microalgae mixture Haematoccocus Pluvialis and Tetradesmus obliquus, and then regenerated with mechanical (backwashing), chemical (HCl, NaOH, NaClO, P3-Ultrasil) and biological (dishwashing and laundry detergents) cleaning methods. The filtration time of the individual experiments is compared with a new membrane, and the increase is determined. Backwashing cleans the pores, but the biofilm sticks to the membrane surface and blocks the pores shortly after a new cycle. It was shown that the biofilm can only be removed chemically through oxidative effects or anionic surfactants. Hydrolysis does not remove the biofilm, and it can actually make the blockage worse. Bigger cellular residues can only be removed with enzymes. This improves cleaning performance by 61% compared to commercial cleaning agents for membranes and 42% compared to backwashing. Full article