Membranes

For an iron-chromium redox flow battery (ICRFB), sulfonated poly(ether ether ketone) (SPEEK) membranes with five various degrees of sulfonation (DSs) are studied. To select the SPEEK membrane with the ideal DS for ICRFB applications, the physicochemical characteristics and single-cell performance are taken into consideration. Following all the investigations, it has been determined that the SPEEK membrane, which has a DS of 57% and a thin thickness of 25 μm, is the best option for replacing commercial Nafion 212 in ICRFB. Firstly, it exhibits a better cell performance according to energy efficiency (EE) and coulombic efficiency (CE) at the current density range between 40 mA cm⁻² and 80 mA cm⁻². Additionally, it has a more stable EE (79.25–81.64%) and lower discharge capacity decay rate (50%) than the Nafion 212 (EE: 76.74–81.45%, discharge capacity decay: 76%) after 50 charge–discharge cycles, which proves its better oxidation stability as well. In addition, the longer self-discharge time during the open-circuit voltage test further demonstrates that this SPEEK membrane could be employed for large-scale ICRFB applications. Full article

Fractional calculus is an essential tool in studying new phenomena in hydromechanics and heat and mass transfer, particularly anomalous hydromechanical advection–dispersion considering the fractal nature of the porous medium. They are valuable in solving the urgent problem of convective mass transfer in a porous medium (e.g., membranes, filters, nozzles, convective coolers, vibrational prillers, and so on). Its solution allows for improving chemical engineering and technology workflows, refining process models for obtaining porous granular materials, realizing the convective cooling of granular and grain materials, and ensuring the corresponding apparatuses’ environmental safety. The article aims to develop a reliable convective mass transfer model for a porous medium and proposes a practical approach for its parameter identification. As a result, a general scientific and methodological approach to parameter identification of the fractional convective mass transfer model in a porous medium was proposed based on available experimental data. It mainly used Riemann–Liouville fractional time and coordinate derivatives. The comprehensive application of the Laplace obtained the corresponding general solution transform with respect to time and a coordinate, the Mittag-Leffler function, and specialized functions. Different partial solutions in various application case studies proved this solution. Moreover, the algorithm for practically implementing the developed approach was proposed to evaluate parameters for the considered model by evaluation data. It was reduced to the two-parameter model and justified by the available experimental data. Full article

One main objective of this study was to increase the utilization of raw material in the rose (Rosa damascena Mill.) essential oil industry by the application of membrane technologies. In this research, distilled (dearomatized) rose petals, the primary byproduct in essential oil production, were subjected to an enzyme-assisted extraction and subsequent membrane separation for partial concentration at different levels using UF1-PAN and UF10-PAN membranes. The results show that the permeate flux decreased with a rise in volume reduction ratio and increased with a rise in transmembrane pressure and feed flow rate. At the beginning of the process, the highest flux was with the UF1-PAN membrane, but at the end of the process, it was with the UF10-PAN membrane. Total polyphenols of the retentates increased by 27–39% and 26–67% during ultrafiltration with the UF1-PAN and UF10-PAN membranes, respectively, with the highest value obtained for the UF10-PAN membrane at VRR 6. The highest concentration factor and rejection of total solids, total polyphenols, redox-active antioxidants, and radical scavenging antioxidants were obtained at VRR 6 with the UF10-PAN membrane. The use of green technology based on enzyme-assisted extraction and ultrafiltration for recovery and concentration of polyphenols from rose petal byproduct solves practical environmental problems for the treatment and utilization of byproducts from the rose oil industry. The retentate obtained could be used in the food production, cosmetic, and pharmaceutical industries. Full article

The adoption of Proton Exchange Membrane (PEM) fuel cells (FCs) is of great significance in diverse industries, as they provide high efficiency and environmental advantages, enabling the transition to sustainable and clean energy solutions. This study aims to enhance the output power of PEM-FCs by employing the Adaptive Neuro-Fuzzy Inference System (ANFIS) and modern optimization algorithms. Initially, an ANFIS model is developed based on empirical data to simulate the output power density of the PEM-FC, considering factors such as pressure, relative humidity, and membrane compression. The Salp swarm algorithm (SSA) is subsequently utilized to determine the optimal values of the input control parameters. The three input control parameters of the PEM-FC are treated as decision variables during the optimization process, with the objective to maximize the output power density. During the modeling phase, the training and testing data exhibit root mean square error (RMSE) values of 0.0003 and 24.5, respectively. The coefficient of determination values for training and testing are 1.0 and 0.9598, respectively, indicating the successfulness of the modeling process. The reliability of SSA is further validated by comparing its outcomes with those obtained from particle swarm optimization (PSO), evolutionary optimization (EO), and grey wolf optimizer (GWO). Among these methods, SSA achieves the highest average power density of 716.63 mW/cm², followed by GWO at 709.95 mW/cm². The lowest average power density of 695.27 mW/cm² is obtained using PSO. Full article

The lipid membranes of living cells are composed of a large number of lipid types and can undergo phase separation with the formation of nanometer-scale liquid-ordered lipid domains, also called rafts. Raft coalescence, i.e., the fusion of lipid domains, is involved in important cell processes, such as signaling and trafficking. In this work, within the framework of the theory of elasticity of lipid membranes, we explore how amphipathic peptides adsorbed on lipid membranes may affect the domain–domain fusion processes. We show that the elastic deformations of lipid membranes drive amphipathic peptides to the boundary of lipid domains, which leads to an increase in the average energy barrier of the domain–domain fusion, even if the surface concentration of amphipathic peptides is low and the domain boundaries are only partially occupied by the peptides. This inhibition of the fusion of lipid domains may lead to negative side effects of using amphipathic peptides as antimicrobial agents. Full article

Improved upstream titres in therapeutic monoclonal antibody (mAb) production have shifted capacity constraints to the downstream process. The consideration of membrane-based chromatographic devices as a debottlenecking option is gaining increasing attention with the recent introduction of high-capacity bind and elute membranes. We have evaluated the performance and scalability of the Sartobind^® Rapid A affinity membrane (1 mL) for high-productivity mAb capture. For scalability assessment, a 75 mL prototype device was used to process 100 L of clarified cell culture harvest (CH) on a novel multi-use rapid cycling chromatography system (MU-RCC). MabSelect™ PrismA (4.7 mL) was used as a benchmark comparator for Protein A (ProtA) resin studies. Results show that in addition to a productivity gain of >10×, process and product quality attributes were either improved or comparable to the benchmark. Concentrations of eluate pools were 7.5× less than that of the benchmark, with the comparatively higher bulk volume likely to cause handling challenges at process scale. The MU-RCC system is capable of membrane operation at pilot scale with comparable product quality profile to the 1 mL device. The Sartobind^® Rapid A membrane is a scalable alternative to conventional ProtA resin chromatography for the isolation and purification of mAbs from harvested cell culture media. Full article

Osmotically assisted reverse osmosis (OARO) is an innovative process that shows promising potential in the treatment of brine produced by conventional reverse osmosis (RO) systems. This study presents a theoretical and experimental analysis of the OARO process, focusing on its application to achieve minimum liquid discharge (MLD). This theoretical analysis includes the development of a mathematical model to describe the transport phenomena occurring during OARO. By considering mass balance equations coupled with transport equations, the theoretical model allows for the simulation of a full-scale system consisting of a single-stage RO and a four-stage OARO. Experimental investigations are also conducted to validate the theoretical model and to evaluate the performance of the OARO process. A laboratory-scale OARO system is designed and operated using a synthetic RO brine. Various operating conditions, including applied pressure, feed concentration, and draw concentration, are varied to investigate their effects on process performance. The experimental results demonstrate the feasibility of OARO as an MLD solution and also validate the predictions of the theoretical model, confirming its reliability for process optimization and design. The results of the theoretical analysis show that OARO has the potential to significantly improve water recovery compared to conventional RO. Based on the simulation, the optimal operating conditions are explored, leading to a significant reduction (up to 89%) in the volume of brine discharge. Full article

The precise liquidus projection of the V-Ti-Fe system are crucial for designing high-performance hydrogen permeation alloys, but there are still many controversies in the research of this system. To this end, this article first uses the CALPHAD (CALculation of PHAse Diagrams) method to reconstruct the alloy phase diagram and compares and analyses existing experimental data, confirming that the newly constructed phase diagram in this article has good reliability and accuracy. Second, this obtained phase diagram was applied to the subsequent development process of hydrogen permeation alloys, and the (Ti₆₅Fe₃₅)_100−xV_x (x = 0, 2.5, 5, 10, 15, 25) alloys with dual-phase {bcc-(V, Ti) + TiFe} structure were successfully explored. In particular, the alloys with x values equal to 2.5 at.% and 5 at.% exhibit relatively high hydrogen permeability. Third, to further increase the H₂ flux permeation through the alloys, a 500-mm-long tubular (Ti₆₅Fe₃₅)₉₅V₅ membrane for hydrogen permeation was prepared for the first time. Hydrogen permeation testing showed that this membrane had a very high H₂ flux (4.06 mL min⁻¹), which is ca. 6.7 times greater than the plate-like counterpart (0.61 mL min⁻¹) under the same test conditions. This work not only indicates the reliability of the obtained V-Ti-Fe phase diagram in developing new hydrogen permeation alloys, but also demonstrates that preparing tubular membranes is one of the most important means of improving H₂ flux. Full article

Six different TiO₂/CNT nanocomposite-coated polyvinylidene-fluoride (PVDF) microfilter membranes (including –OH or/and –COOH functionalized CNTs) were evaluated in terms of their performance in filtering oil-in-water emulsions. In the early stages of filtration, until reaching a volume reduction ratio (VRR) of ~1.5, the membranes coated with functionalized CNT-containing composites provided significantly higher fluxes than the non-functionalized ones, proving the beneficial effect of the surface modifications of the CNTs. Additionally, until the end of the filtration experiments (VRR = 5), notable flux enhancements were achieved with both TiO₂ (~50%) and TiO₂/CNT-coated membranes (up to ~300%), compared to the uncoated membrane. The irreversible filtration resistances of the membranes indicated that both the hydrophilicity and surface charge (zeta potential) played a crucial role in membrane fouling. However, a sharp and significant flux decrease (~90% flux reduction ratio) was observed for all membranes until reaching a VRR of 1.1–1.8, which could be attributed to the chemical composition of the oil. Gas chromatography measurements revealed a lack of hydrocarbon derivatives with polar molecular fractions (which can act as natural emulsifiers), resulting in significant coalescent ability (and less stable emulsion). Therefore, this led to a more compact cake layer formation on the surface of the membranes (compared to a previous study). It was also demonstrated that all membranes had excellent purification efficiency (97–99.8%) regarding the turbidity, but the effectiveness of the chemical oxygen demand reduction was slightly lower, ranging from 93.7% to 98%. Full article

The concentration dependence of the conductivity of ion exchange membranes (IEMs), as well as other transport properties, has been well explained by the contemporary two-phase model (Zabolotsky et al., 1993) considering a gel phase and an inter-gel phase filled with electroneutral solution. Here, this two-phase model has been adopted and first applied in electrolytes containing mixed counter-ions to investigate the correlation between the membrane ionic conductivity and its microstructure. For three representative commercial cation exchange membranes (CEMs), the total membrane conductivity (${\kappa }^T$) when in equilibrium with mixed MgSO₄ + Na₂SO₄ and H₂SO₄ + Na₂SO₄ electrolytes could be well predicted with the experimental composition of counter-ions in the gel and inter-gel phase, as well as the counter-ion mobility in the gel phase when the membrane is in a single electrolyte. It is found that the volume fraction of the inter-gel phase ($f_2$) has little impact on the predicted results. The accuracy of the model can be largely improved by calculating the inter-gel phase conductivity (${\kappa }^{in}$) with the ionic mobility being the same as that in the external solution (obtained via simulation in the OLI Studio), rather than simply as equivalent to the conductivity of the external solution (${\kappa }^s$). Moreover, a nonlinear correlation between the CEMs’ conductivities and the counter-ion composition in the gel phase is observed in the mixed MgSO₄ + Na₂SO₄ solution, as well as for the Nafion117 membrane in the presence of sulfuric acid. For CEMs in mixed MgSO₄ + Na₂SO₄ electrolytes, the calculated conductivity values considering the interaction parameter $\sigma$, similar to the Kohlrausch’s law, are closer to the experimental ones. Overall, this work provides new insights into membrane conductivity with mixed counter-ions and testifies to the applicability of the contemporary two-phase model. Full article

Multifunctional membrane technology has gained tremendous attention in wastewater treatment, including oil/water separation and photocatalytic activity. In the present study, a multifunctional composite nanofiber membrane is capable of removing dyes and separating oil from wastewater, as well as having antibacterial activity. The composite nanofiber membrane is composed of cellulose acetate (CA) filled with zinc oxide nanoparticles (ZnO NPs) in a polymer matrix and dipped into a solution of titanium dioxide nanoparticles (TiO₂ NPs). Membrane characterization was performed using transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and Fourier transform infrared (FTIR), and water contact angle (WCA) studies were utilized to evaluate the introduced membranes. Results showed that membranes have adequate wettability for the separation process and antibacterial activity, which is beneficial for water disinfection from living organisms. A remarkable result of the membranes’ analysis was that methylene blue (MB) dye removal occurred through the photocatalysis process with an efficiency of ~20%. Additionally, it exhibits a high separation efficiency of 45% for removing oil from a mixture of oil–water and water flux of 20.7 L.m⁻² h⁻¹ after 1 h. The developed membranes have multifunctional properties and are expected to provide numerous merits for treating complex wastewater. Full article

Extracorporeal membrane oxygenation (ECMO) is an important rescue therapy method for the treatment of severe hypoxic lung injury. In some cases, oxygen saturation and oxygen partial pressure in the arterial blood are low despite ECMO therapy. There are case reports in which patients with such instances of refractory hypoxemia received a second membrane lung, either in series or in parallel, to overcome the hypoxemia. It remains unclear whether the parallel or serial connection is more effective. Therefore, we used an improved version of our full-flow ECMO mock circuit to test this. The measurements were performed under conditions in which the membrane lungs were unable to completely oxygenate the blood. As a result, only the photometric pre- and post-oxygenator saturations, blood flow and hemoglobin concentration were required for the calculation of oxygen transfer rates. The results showed that for a pre-oxygenator saturation of 45% and a total blood flow of 10 L/min, the serial connection of two identical 5 L rated oxygenators is 17% more effective in terms of oxygen transfer than the parallel connection. Although the idea of using a second membrane lung if refractory hypoxia occurs is intriguing from a physiological point of view, due to the invasiveness of the solution, further investigations are needed before this should be used in a wider clinical setting. Full article

The design and fabrication of advanced membrane materials for versatile oil/water separation are major challenges. In this work, a superwetting stainless steel mesh (SSM) modified with in situ-grown TiO₂ was successfully prepared via one-pot hydrothermal synthesis at 180 °C for 24 h. The modified SSM was characterized by means of scanning electron microscopy, energy spectroscopy, and X-ray photoelectron spectroscopy analysis. The resultant SSM membrane was superhydrophilic/superoleophilic in air, superoleophobic underwater, with an oil contact angle (OCA) underwater of over 150°, and superhydrophobic under oil, with a water contact angle (WCA) as high as 158°. Facile separation of immiscible light oil/water and heavy oil/water was carried out using the prewetting method with water and oil, respectively. For both “oil-blocking” and “water-blocking” membranes, the separation efficiency was greater than 98%. Also, these SSMs wrapped in TiO₂ nanoparticles broke emulsions well, separating oil-in-water and oil-in-water emulsions with an efficiency greater than 99.0%. The as-prepared superwetting materials provided a satisfactory solution for the complicated or versatile oil/water separation. Full article

Recently, the multi-level interwoven structured micro/nano fiber membranes with coarse and fine overlaps have attracted lots of attention due to their advantages of high surface roughness, high porosity, good mechanical strength, etc., but their simple and direct preparation methods still need to be developed. Herein, the multi-level structured micro/nano fiber membranes were prepared novelly and directly by a one-step electrospinning technique based on the principle of micro-phase separation caused by polymer incompatibility using polystyrene (PS) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) as raw materials. It was found that different spinning fluid parameters and various spinning process parameters will have a significant impact on its morphology and structures. Under certain conditions (the concentration of spinning solution is 18 wt%, the mass ratio of PS to PVDF-HFP is 1:7, the spinning voltage is 30 kV, and the spinning receiving distance is 18 cm), the PS/PVDF-HFP membrane with optimal multi-level structured micro/nano fiber membranes could be obtained, which present an average pore size of 4.38 ± 0.10 μm, a porosity of 78.9 ± 3.5%, and a water contact angle of 145.84 ± 1.70°. The formation mechanism of micro/nano fiber interwoven structures was proposed through conductivity and viscosity tests. In addition, it was initially used as a separation membrane material in membrane distillation, and its performance was preliminarily explored. This paper provides a theoretical and experimental basis for the research and development of an efficient and feasible method for the preparation of multi-level micro/nano fiber membranes. Full article

Recently, electro-kinetic (EK) remediation has become more popular as a novel method for removing chromium contamination from soil. This approach, however, is ineffective since it uses both cationic and anionic forms of chromium. In this study, a membrane-based technique was employed to increase the efficiency of the electro-kinetic removal of chromium. Chromium removal from polluted sludge was studied using four bench-scale experiments. Two of these experiments employed distilled water (EK$-$1 and EK$-$2 and membrane), whereas the other used acetic acid as the catholyte (EK$-$3 and EK$-$4 and membrane). The pH, total chromium, and fractionation of chromium in the sludge were measured after remediation. In the EK$-$1, EK$-$2 and membrane, and EK$-$3 and EK$-$4 and membrane trials, the average removal efficiencies of total chromium were 47.6%, 58.6%, and 74.4%, 79.6%, respectively. In contrast to the electro-kinetic remediation strategy, which left approximately 80% of the sludge neutral or alkaline after treatment, the membrane created acidic soil conditions throughout the sludge. For example, the high field intensity used in the membrane tests may have helped to facilitate chromium desorption, dissolution, and separation from the sludge and enhanced chromium mobility. The findings show that the membrane can improve the effectiveness of chromium removal from sludge when utilized in the EK remediation process. Full article

The effect of water, methanol, and hexane vapors on gas permeability was studied in a hybrid membrane containing 5 wt% copolyimide brushes with poly(methyl methacrylate) side chains (PI-g-PMMA) in a poly(phenylene oxide) (PPO) matrix, and in a pristine PPO membrane. These membranes in the form of dense nonporous films were further examined by atomic force microscopy (AFM) and scanning electron microscopy (SEM), as well as by measuring their mechanical and gas transport properties. A gas separation study of the membranes in a dry state and the membranes saturated with water, methanol, and hexane vapors was performed to estimate the effect of each vapor on the H₂, CO₂, N₂ permeability and selectivity in the separation of H₂/N₂ and CO₂/N₂ pairs. In general, saturation with water, methanol, and hexane vapors caused a decrease in the gas permeability of both membranes. The hybrid membrane containing copolyimide brushes demonstrated enhanced selectivity in the separation of H₂/N₂ and CO₂/N₂ pairs. It was found that a special effect of the vapors used for membrane saturation is associated with their molar volume. The solubility and diffusion coefficients of N₂ and CO₂ were obtained by Grand Canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations. Full article

This study presented a detailed investigation into the performance of a plate–frame water gap membrane distillation (WGMD) system for the desalination of untreated real seawater. One approach to improving the performance of WGMD is through the proper selection of cooling plate material, which plays a vital role in enhancing the gap vapor condensation process. Hence, the influence of different cooling plate materials was examined and discussed. Furthermore, two different hydrophobic micro-porous polymeric membranes of similar mean pore sizes were utilized in the study. The influence of key operating parameters, including the feed water temperature and flow rate, was examined against the system vapor flux and gained output ratio (GOR). In addition, the used membranes were characterized by means of different techniques in terms of surface morphology, liquid entry pressure, water contact angle, pore size distribution, and porosity. Findings revealed that, at all conditions, the PTFE membrane exhibits superior vapor flux and energy efficiency (GOR), with 9.36% to 14.36% higher flux at a 0.6 to 1.2 L/min feed flow rate when compared to the PVDF membrane. The copper plate, which has the highest thermal conductivity, attained the highest vapor flux, while the acrylic plate, which has an extra-low thermal conductivity, recorded the lowest vapor flux. The increasing order of GOR values for different cooling plates is acrylic < HDPE < copper < aluminum < brass < stainless steel. Results also indicated that increasing the feed temperature increases the vapor flux almost exponentially to a maximum flux value of 30.36 kg/m²hr. The system GOR also improves in a decreasing pattern to a maximum value of 0.4049. Moreover, a long-term test showed that the PTFE membrane, which exhibits superior hydrophobicity, registered better salt rejection stability. The use of copper as a cooling plate material for better system performance is recommended, while cooling plate materials with very low thermal conductivities, such as a low thermally conducting polymer, are discouraged. Full article

In this study, a microbial fuel cell was integrated into a hydroponic system (MFC-Hyp) using a ceramic membrane as a separator. The MFC-Hyp is a passive system that allows the transport of nutrients from wastewater in the microbial fuel cell (MFC) to water in the hydroponic vessel (Hyp) through a ceramic membrane separator, with no external energy input. The performance of this system was examined using potato-process wastewater as a source of energy and nutrients (K, P, N) and garlic chives (Allium tuberosum) as a hydroponic plant. The results showed that based on dry weight, the leaves of Allium tuberosum grew 142% more in the MFC-Hyp than those of the plant in the Hyp without the MFC, in a 49-day run. The mass fluxes of K, P, and NO₃⁻-N from the MFC to the Hyp through the ceramic membrane were 4.18 ± 0.70, 3.78 ± 1.90, and 2.04 ± 0.98 µg s⁻¹m⁻², respectively. It was apparent that the diffusion of nutrients from wastewater in the MFC enhanced the plant growth in the Hyp. The MFC-Hyp in the presence of A. tuberosum produced the maximum power density of 130.2 ± 45.4 mW m⁻². The findings of this study suggest that the MFC-Hyp system has great potential to be a “carbon-neutral” technology that could be transformed into an important part of a diversified worldwide energy–water–food supply system. Full article

For decades, tissue regeneration has been a challenging issue in scientific modeling and human practices. Although many conventional therapies are already used to treat burns, muscle injuries, bone defects, and hair follicle injuries, there remains an urgent need for better healing effects in skin, bone, and other unique tissues. Recent advances in three-dimensional (3D) printing and real-time monitoring technologies have enabled the creation of tissue-like membranes and the provision of an appropriate microenvironment. Using tissue engineering methods incorporating 3D printing technologies and biomaterials for the extracellular matrix (ECM) containing scaffolds can be used to construct a precisely distributed artificial membrane. Moreover, advances in smart sensors have facilitated the development of tissue regeneration. Various smart sensors may monitor the recovery of the wound process in different aspects, and some may spontaneously give feedback to the wound sites by releasing biological factors. The combination of the detection of smart sensors and individualized membrane design in the healing process shows enormous potential for wound dressings. Here, we provide an overview of the advantages of 3D printing and conventional therapies in tissue engineering. We also shed light on different types of 3D printing technology, biomaterials, and sensors to describe effective methods for use in skin and other tissue regeneration, highlighting their strengths and limitations. Finally, we highlight the value of 3D bioengineered membranes in various fields, including the modeling of disease, organ-on-a-chip, and drug development. Full article