Search Results (335)

This study introduces a novel hybrid model for an electromembrane stack, unifying an equivalent electrical circuit model incorporating specific resistance ($R_M,R_s$) and capacitance ($C_{gs},C_{dl}$) parameters with an empirical fouling model in a single framework. The model simplifies the traditional approach by serially connecting N ($N=10$) ion exchange membranes (anionic PC-SA and cationic PC-SK) and is validated using $NaCl$ and $N{a}_{2}S{O}_4$ solutions in comparison with laboratory tests using various voltage signals, including direct current and electrically pulsed reversal operations at frequencies of 2000 and 4000 Hz. The model specifically accounts for the chemical stratification of the cell unit into bulk solution, diffusion, and Stern layers. We also included a calibration method using correction factors (${\alpha }_i$) to fine-tune the electrical current signals induced by voltage stimulation. The empirical component of the model uses experimental data to simulate membrane fouling, ensuring consistency with laboratory-scale desalination processes performed under pulsed reversal operations and achieving a prediction error of less than 10%. In addition, a comparative analysis was used to assess the increase in electrical resistance due to fouling. By integrating electronic and empirical electrochemical data, this hybrid model opens the way to the construction of simple, practical, and reliable models that complement theoretical approaches, signifying an advance for a variety of electromembrane-based technologies. Full article

Cationic surfactants from the group of quaternary ammonium compounds (QACs) are widely used in disinfectants, cosmetics, and household and industrial products. Their strong antimicrobial activity and chemical stability make them valuable in applications but also highly persistent and toxic when released into aquatic environments. This problem has become increasingly relevant during and after the COVID-19 pandemic, when global use of QAC-based disinfectants increased drastically, resulting in their frequent detection in municipal, hospital, and industrial effluents. The concentrations of QACs reported in wastewater range from trace levels to several mg/L, often reaching inhibitory thresholds for biological treatment processes. Although surfactants are not listed in any current European directive, the revised Directive (EU) 2024/1440 classifies micropollutants as a priority group, imposing stricter environmental quality standards and mandatory monitoring requirements. Within this regulatory framework, QACs are recognized as compounds of emerging concern, and their effective removal from wastewater has become a critical challenge. This review summarizes the current knowledge on conventional treatment technologies (coagulation, adsorption, ion exchange, advanced oxidation, and biological processes) and membrane-based methods (ultrafiltration, nanofiltration, reverse osmosis, forward osmosis, and hybrid systems) for the removal of cationic surfactants from water and wastewater. Mechanisms of separation, performance, and operational limitations are discussed. Full article

Scorpion venom toxins are important peptides being studied for their clinical significance. These peptides act by binding to ion channels in the membrane of nerve cells, causing the symptoms associated with scorpion stings (scorpionism). They principally affect the function of voltage-gated sodium channels (Nav) and are valuable for studying ion channels. Scorpions from the Buthidae family contain toxins that affect sodium channels and have a high affinity for mammalian channels. In this study, two sodium toxins isolated from the venom of the scorpion Centruroides hirsutipalpus, a member of the Buthidae family, were identified as belonging to the beta-type subfamily. These toxins were purified from whole venom using molecular exclusion, cationic-exchange, and reverse-phase chromatography techniques. Their molecular masses were determined using mass spectrometry, while their amino acid sequences were obtained by Edman degradation. A comparative analysis revealed that the sequences are identical to ChiNaBet60 and ChiNaBet50 toxins (now named Chirp7 and Chirp9, respectively) previously identified in the venom gland transcriptomics from C. hirsutipalpus. Furthermore, toxicity studies showed that these toxins were lethal to mammals. Electrophysiological analysis revealed that these peptides act as sodium channel–modulating toxins. In addition, interaction assays with antibodies were performed to analyze the structural determinants governing the binding mechanism. Full article

Ionomers are promising materials because ionic interactions and their reversible clustering provide sensitivity to stimuli and facilitate energy dissipation, polymer miscibility, and ion transport. The existence of a wide variety of interacting ionic groups and their associated macromolecular structures provides the basis for considering the supramolecular organization of ionic polymeric materials as a factor determining the emergence of specific properties. The main structural elements of ionomers are ionic clusters, and the properties of ionomers are determined by their sizes and size distribution. Ionomers are attractive for use in composites, actuators, coatings, dyed textiles, adhesives, shape-memory and self-healing materials, water purification membranes, and ion-exchange membranes for fuel cells and batteries. This paper presents a review of the macromolecular structure and supramolecular organization of ionomers and their properties, depending on the basis of their ionic functionalization. The ionic functions of ionomers are determined primarily by the type of ion (cations or anions) that serves as the basis for their functionalization. Ionomers containing both anionic and cationic pendant ions are considered, with attention given to the influence of the nature of the counterions used on the properties of ionomers. Full article

This study investigates the simultaneous removal of copper and nickel ions from aqueous solutions using Donnan dialysis (DD), with process optimization performed through Response Surface Methodology (RSM). An initial screening identified the most effective counter-ion, guiding the experimental design toward optimal ion removal. Comparative experiments using Fujifilm Type 1 and Type 2 cation-exchange membranes revealed the superior performance of Type 1 for both metals, as confirmed by FTIR-ATR spectroscopic analysis of membrane morphology. A comprehensive experimental campaign based on a Central Composite Design (CCD) evaluated the effects of copper, nickel, and sodium ion concentrations on removal efficiency. Under optimized conditions—80 mg/L Cu²⁺, 100 mg/L Ni²⁺, and 0.06 mol/L Na⁺—the Fujifilm Type 1 membrane achieved remarkable removal rates of 99.67 ± 0.21% for copper and 98.85 ± 0.34% for nickel. These values were experimentally validated (99.45 ± 0.18% and 98.71 ± 0.27%, n = 3), showing excellent agreement between predicted and observed data and confirming the robustness of the optimized Donnan dialysis process. Overall, the results highlight Donnan dialysis as a highly efficient and environmentally sustainable approach for the removal and recovery of heavy metals from aqueous solutions using Fujifilm cation-exchange membranes. Full article

Inspired by the mechanism of ion exchange resins, this study is a first-report in constructing a dual-layer photocathodic protective coating with ionic selectivity to enhance corrosion resistance property. The microstructure, composition, and ion selectivity of the coating are characterized by scanning electron microscopy, Raman spectroscopy, infrared spectroscopy, and membrane potential. It shows that the outer g-C₃N₄/TiO₂ cation-selective layer plays a role in preventing corrosive Cl⁻ ions passing through the coating; the inner g-C₃N₄-TiO₂-CTAB anion-selective layer could prevent Fe²⁺ ions from diffusing through the coating. Furthermore, the coated carbon steel sample demonstrates a minimum OCP (open circuit potential) value of −770 mV (vs. SCE) under illumination in 3.5% NaCl media. Interestingly, the OCP remains around −720 mV (vs. SCE) even after light deprivation. The synergistic effect between ion selectivity and photocathodic protection is described, in detail, in the following. Full article

Ionic Polymer–Metal Composites (IPMCs) are promising electroactive polymers for artificial muscles, as their bending motion depends on the induced current—greater current leads to greater bending. While conventional IPMCs use cation exchange membranes, this study explores IPMCs containing both immobile positive and negative charges, resembling real muscle tissue. Considering that an IPMC consists of an ion-exchange membrane sandwiched between two thin metal coatings serving as electrodes, we found that (i) improving the contact between the metal coating (electrode) and the ion exchange membrane is an effective way to enhance current induction. Achieving tight electrode membrane contact can drastically increase the induced current by up to four orders of magnitude, and even samples that previously showed no current induction can exhibit measurable current after improvement. (ii) Doping with mobile ions is another well-known method of enhancing IPMC current. However, we found that simply introducing dopants into the IPMC body is not effective; the choice of dopant is crucial. In this work, we identified silver ions as effective dopants for enhancing current induction. Considering that real muscles consume oxygen for activation, we also attempted to supply oxygen to the IPMC surface. We confirmed that (iii) supplying oxygen to the IPMC surface is another effective means of enhancing current induction, which in turn resulted in a significant improvement in IPMC bending performance. Full article

This paper presents comprehensive studies of pitting corrosion, which precedes the appearance of fistulas in galvanized steel pipelines of hot and cold water supply systems. Corroded galvanized pipes taken out from water supply systems within their operation and scale samples were the subject of this research. The current work continues the research on one of the four structural elements of tubercles—the dense layer. The corrosion of the zinc coating and the steel base of pipes inside the tubercles led to a gradual increase in the concentration of a solution containing components of the corroding metal (zinc and iron cations) and anions in water (mainly chlorides and sulfates). To explain the corrosion under the tubercles, their dense layer was compared with an anion exchange membrane with selective properties, which provided the primary concentration of the salt solution in the structure of the tubercles with a significant increase in the concentration of aggressive anions compared to the source water. The formation of fistulas in the cavity leads to a secondary concentration of solution inside the tubercle, mainly consisting of iron chloride. At the same time, due to the hydrolysis of the formed iron salts and a decrease in pH, the corrosion rate increases and becomes independent of external conditions. This article summarizes ten years of experience in examining corrosion of steel pipes from external and internal water supply systems. Full article

This study evaluated the performance of a constant-current two-compartment bipolar membrane electrodialysis (BMED) system comprising cation exchange membranes and bipolar membranes for the recovery of sodium hydroxide (NaOH) from sodium sulfate (Na₂SO₄) solution. Key operating parameters, current density, feed concentration, initial base concentration, and solution volume, were systematically varied to investigate their effects on ion transport, NaOH concentration, current efficiency, and energy consumption. At 450 A/m² with 1.30 M Na₂SO₄, 0.10 M initial NaOH, and 1.00 L solution volume, the system achieved a NaOH recovery yield of 69.21%, a final concentration of 2.13 M, a current efficiency of 36.39%, and an energy consumption of 1.82 kWh/kg Na₂SO₄ processed, corresponding to 4.72 kWh/kg NaOH produced, indicating optimal energy efficiency and process stability. To maximize concentration, the highest NaOH concentration of 2.85 M was obtained at the same current density by reducing the initial NaOH volume to 0.50 L, although this led to increased water transport and higher energy consumption (2.31 kWh/kg Na₂SO₄; 5.99 kWh/kg NaOH), compromising process efficiency. Full article

In the production of recombinant antibody/Fc-fusion proteins using mammalian cells, many aggregates often form alongside the target proteins, particularly with bispecific antibodies. To ensure the safety of biological products, it is essential to control the amount of aggregates within a specific range. A traditional downstream process typically involves using Protein A (ProA) resin to capture the target antibody, followed by two polishing steps to ensure purity; for instance, using an anion exchange chromatography (AEX) in flow-through mode and a cation exchange chromatography (CEX) in binding–elution mode. In this study, we choose a Dual Action Fab (DAF), which can bind two antigens and is prone to aggregation when expression in CHO (Chinese Hamster Ovary) cells. We introduce hydrophobic interaction membrane chromatography (HIMC) operating in flow-through mode, which enhances production efficiency while reducing costs and the risks associated with column packing. We evaluated the impact of the operating buffer system, as well as the pH and conductivity of the loading samples, on aggregate removal using HIMC. Additionally, we investigated the mechanism of aggregate binding and found that loading conditions had a limited impact on this process. Overall, our findings indicate that employing HIMC can achieve a 20% reduction in aggregate levels. These results demonstrate that HIMC in flow-through mode is an effective and robust approach for reducing aggregates during antibody purification. Full article

Composite anion exchange membranes (AEMs) based on poly(terphenylene piperidinium) (PTPiQA) and impregnated with varying loadings of quaternized graphene oxide (QGO) as filler were developed, and their properties as anion exchange membranes for use in water electrolysis (AEMWEs) and fuel cells (AEMFCs) were explored. This study investigates the trade-off between mechanical robustness, ionic conductivity, and alkaline stability in QGO-reinforced twisted polymer backbones. QGO synthesized by functionalization with ethylenediamine (EDA), followed by quaternization with glycidyl trimethylammonium chloride (GTMAC), was used as a filler for PTPiQA, and the properties of the resulting composites PTPiQA-QGO-X investigated as a function of QGO loading for X between 0.1 and 0.7 wt%. Among all compositions, PTPiQA-QGO-0.3% exhibited the highest OH⁻ conductivity of 71.56 mS cm⁻¹ at room temperature, attributed to enhanced ionic connectivity and water uptake. However, this increase in conductivity was accompanied by a slight decrease in ion exchange capacity (IEC) retention (91.8%) during an alkaline stability test in 1 M KOH at 60 °C for 336 h due to localized cation degradation. Mechanical testing revealed that PTPiQA-QGO-0.3% offered optimal dry and wet tensile strength (dry TS of 42.77 MPa and wet TS of 30.20 MPa), whereas higher QGO loadings yielded low mechanical strength. These findings highlight that 0.3 wt% QGO balances ion transport efficiency and mechanical strength, while higher loadings improve alkaline durability, compromising mechanical durability and guiding the rational design of AEMs for AEMWEs and AEMFCs. Full article

Background/Objectives: Recent evidence challenges the classical chemiosmotic theory, suggesting that proton movement along membrane surfaces—not bulk-phase gradients—drives bioenergetic processes. Proton accumulation on membranes like the myelin sheath and endoplasmic reticulum (ER) may represent a universal mechanism for cellular energy storage. This study investigates whether phospholipids from these membranes, combined with anionic bee venom proteins, enhance proton absorption, potentially elucidating a novel bioenergetic pathway. Methods: Five phospholipids (phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, sphingomyelin, phosphatidylcholine) from rat liver were isolated to model myelin/ER membranes. Anionic proteins (pI 5.65–5.80) were purified from bee venom via cation exchange chromatography. Liposomes (with/without proteins) were prepared, and proton absorption was quantified by pH changes in suspensions versus pure water. Statistical significance was assessed via ANOVA and t-tests. Results: All phospholipid liposomes examined in this study absorbed protons under the tested conditions, with phosphatidylethanolamine showing the highest capacity (pH increase: 7.00 → 7.18). Liposomes enriched with anionic proteins exhibited significantly greater proton absorption (e.g., phosphatidylserine + proteins: pH 8.15 vs. 7.15 alone; p < 2.43 × 10⁻⁶). Sphingomyelin-protein liposomes absorbed the most protons, suggesting that protein–phospholipid interactions modulate surface proton affinity. Conclusions: Anionic bee venom proteins amplify proton absorption by phospholipid membranes, supporting the hypothesis that lipid–protein complexes act as “proton capacitors”. This mechanism may underpin extramitochondrial energy storage in myelin and ER. Pharmacologically, targeting these interactions could mitigate bioenergetic deficits in aging or disease. Further research should define the structural basis of proton capture by membrane-anchored proteins. Full article

In coastal countries facing a shortage of drinking water, seawater desalination is essential for the production of potable water. During desalination, a large volume of waste stream, known as brine, is generated. This stream contains high concentrations of salts, particularly those of economic importance to the European Union, such as magnesium and calcium. By further processing this stream, these materials can be recovered. One method studied for separating magnesium from wastewater is membrane crystallization (MCr). The MCr process developed in this work utilizes ion-exchange membranes that separate the model brine solution from a precipitating agent, which is a solution of sodium hydroxide. During the process, the membrane allows the transport of anions between the two solutions, enabling the reaction between OH⁻ anions and Mg²⁺ cations, which leads to the formation of a magnesium hydroxide precipitate. The formed precipitate can then be filtered out of the brine solution, which now has decreased salinity due to crystallization facilitated by the ion-exchange membrane. However, precipitation occurs near the membrane surface, resulting in the deposition of magnesium hydroxide onto the outer surface of the membrane. The aim of this study is to investigate methods for effectively removing magnesium hydroxide from the membrane surface, with a primary focus on maximizing the yield of magnesium hydroxide crystals in suspension. Crystal removal was induced by circulation of hydrochloric acid, followed by circulation of demineralized water through the membrane module after crystallization. In this study, a membrane module made of hollow-fiber anion-exchange membranes was employed. The production cost of these membranes is approximately 50% lower per square meter compared to flat-sheet membranes commonly used in electrodialysis, demonstrating strong potential for commercial application. More than 85% magnesium conversion was achieved during the process, yet the majority of the crystals remained attached to the membrane. Circulation of hydrochloric acid and demineralized water after the crystallization process caused detachment of the crystals into suspension, nearly doubling their yield. Full article

Determining the active substance content in the tested product is an essential part of research for overall assessment of the quality of a medicinal substance. This role can be successfully performed by membrane electrodes that are selective for a specific drug. The novelty of the presented research is the development of the first ion-selective electrode with a polymer membrane phase with the octenidine (OCT) function. Classical ion-selective electrodes (ISE), polymer electrodes with an internal Ag/AgCl electrode, and electrode bodies with glassy carbon were used for the research. The membranes were prepared based on cation exchangers from the borate group and neutral cyclodextrin. All sensors have good parameters, e.g., the polymer electrode with KtpClPB is characterised by a wide linear range of −logc 6−3, a low limit of detection 5 × 10⁻⁷ M, and a near-Nernstian, reproducible slope of characteristics of 31.41 ± 1.14 mV/decade. It can be seen that a stable, reversible potential and a short response time were achieved for this sensor. The obtained favourable selectivity coefficients of the electrode determined in relation to excipients allowed direct determination of octenidine, e.g., in lozenges. The results obtained with the calibration curve method show a recovery of 97% and a precision of SD 2.3 mg/L, which indicates that the data are consistent with the pharmacopoeia requirements. Full article

Brine with a high magnesium-to-lithium ratio was separated by electrodialysis equipped with a monovalent cation exchange membrane under differing operational parameters. The ionic concentration variations, separation coefficients, lithium recovery ratio, permselectivity coefficient, and Li⁺ flux were analyzed to evaluate the effect of the initial Li⁺/Mg²⁺ mass concentration ratio, applied voltage, and initial volume ratio between the dilute and concentrated compartments on the separation performance of magnesium and lithium. The results showed that the increase in initial Li⁺/Mg²⁺ concentration ratio significantly increased the separation coefficient, lithium recovery ratio, and Li⁺ flux, demonstrating an improvement in the separation performance since the Li⁺ migration was accelerated when less Mg²⁺ competed with Li⁺. As the applied voltage increased from 10 V to 15 V, the separation coefficient increased, and the lithium recovery ratio and Li⁺ flux increased within 60 min; however, as the applied voltage increased to 20 V, the separation coefficient, the lithium recovery ratio, and the Li⁺ flux did not increase, which indicated that an increase in the applied voltage within the limits would contribute to the separation performance. The increase in the initial volume ratio between the dilute and concentrated compartments decreased the separation coefficient and lithium recovery ratio, indicating that the separation performance had declined. Full article