Membranes and Membrane Technologies最新文献

This study explores electrospun nanofiber membranes fabricated from cellulose acetate (CA) and polyvinylidene fluoride (PVDF) for adsorbing methylene blue (MB) dye and heavy metals, likely copper (Cu(II)) and lead (Pb(II)). The CA/SDS-GO/zeolite demonstrated enhanced performance, achieving a 95.02% adsorption efficiency for MB dye and a capacity of 237.35 mg/g, compared to PVDF/SDS-GO/zeolite, which exhibited 90.62% efficiency and a capacity of 226.54 mg/g. The enhanced efficiency can be ascribed to the CA membrane’s extensive surface area and numerous active sites. For heavy metal removal, the CA membrane showed a higher adsorption efficiency for Pb(II) (95.48%, 238.71 mg/g) than for Cu(II) (94.39%, 235.99 mg/g). Further adsorption isotherm studies revealed that the Langmuir model (correlation coefficient of 0.9999) fit better than the Freundlich model, suggesting homogenous surface interactions with Pb(II) molecules. Due to its extensive surface area and active sites, CA/SDS-GO/zeolite shows great potential as an efficient adsorbent for eliminating Pb(II), thereby improving both adsorption efficiency and the membrane’s applicability in environmental remediation.

Anion-exchange membranes based on cardo polybenzimidazole and zinc(II) ions with various molar ratios of metal ions (0, 0.05, 0.25, 0.50, and 1.00) were prepared by casting solutions of metal–polymer complexes. The introduction of zinc(II) ions into the structure of cardo polybenzimidazole is accompanied by the formation of a cross-linked polymer matrix due to the coordination of metal ions to the pyridine nitrogen atoms of the monomer unit (–N=) and the appearance of anion-conducting properties. Increasing the metal content leads to an increase in the ionic conductivity of the membranes in the nitrate form from 1.8 × 10^–8 to 8.3 × 10^–6 S/cm. It is shown that the obtained materials demonstrate preferential transfer of monovalent anions (chloride, fluoride, nitrate) compared to divalent anions (sulfate) during electrodialysis. The selectivity coefficients reach 9.7 and 14 for chloride–sulfate and nitrate–sulfate pairs, and 5.7 and 9.1 for chloride–fluoride and nitrate–fluoride pairs, respectively. The obtained selectivity coefficient values exceed the corresponding values for the commercial Neosepta AMX anion-exchange membrane. At the same time, long-term cycling of the obtained membranes in galvanostatic mode leads to their degradation with leaching of zinc ions.

In this study, membranes based on palladium and its alloy with copper, capable of selectively transmitting hydrogen in the range of 25–500°C, were manufactured. Modification of the membrane surface by applying a nanostructured coating significantly expanded the operating capabilities of Pd membranes to low temperatures unattainable by analogs. This result was achieved by accelerating the limiting surface stages and, accordingly, shifting the influence of the diffusion stage toward lower temperatures. The obtained results were confirmed by data on the activation energy of the processes, according to which, due to surface modification, the activation energy was reduced by up to 2 times, compared to uncoated membranes. These results formed the basis for the mathematical model of hydrogen transport through Pd membranes at low temperatures developed in this study. This model takes into account the membrane surface roughness factor, which is an important criterion for the selected temperature range, where surface processes limit hydrogen transport. The obtained results suggest that the developed model is promising for predicting the efficiency of Pd-based membranes.

Modern studies in the field of lithium metal batteries focus on the development of safe and stable electrolytes with high ionic conductivity and electrochemical stability. In this context, promising materials are gel polymer electrolytes based on perfluorosulfonic acid cation-exchange membranes modified with inorganic fillers and solvated with aprotic solvents. This study addresses Nafion® composite membranes containing surface-sulfonated zirconia (sZrO₂) and solvated with binary mixtures of ethylene carbonate (EC) with dimethylacetamide (DMAc), dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) at a 1 : 1 ratio by volume. The presented systems demonstrate the dependence of ionic conductivity on the nature of the solvent, following the series: EC–DMAc > EC–DMF > EC–DMSO, with the maximum conductivity (2.2 mS/cm at 25°C) being achieved for the Nafion@sZrO₂–EC–DMAc composition. The resulting electrolytes are electrochemically stable up to 4.2 V (vs. to Li⁺/Li), which makes them compatible with cathode materials such as LiFePO₄ (LFP). However, DMSO slowly interacts with lithium metal to form a low-conductivity SEI layer, whereas EC–DMAc and EC–DMF systems provide stable operation of Li|Li cells for >1000 h at a current density of 0.1 mA/cm². Cyclic tests of Li|LFP cells with Nafion@sZrO₂–EC–DMAc and Nafion@sZrO₂–EC–DMF electrolytes show an initial discharge capacity of ∼155 mA h/g (0.1C) and high stability—capacity loss after 50 cycles at 0.5C is 4.7 and 2.0%, respectively. The obtained results confirm the potential of using Nafion^®-based composite gel polymer electrolytes solvated with amide solvents in new generation lithium metal batteries.

This work presents an optimized bead-milling approach for producing monodisperse cesium dihydrogen phosphate nanoparticles (100–200 nm), while preserving their P2₁/m crystal structure, as confirmed by X-ray diffraction and particle size characterized by scanning electron microscopy and Rietveld refinement (125 ± 10 nm crystallites). The obtained nanoparticles demonstrated high proton conductivity (∼1.8 × 10^–2 S cm^–1 at 240°C) due to the bulk transport mechanism predominance, which allowed them to be successfully applied in the first tests in fuel cell electrodes (OCV 0.96 V, current density ∼120 mA/cm² at 235°C). The developed mechanical processing method enables precise particle size control, facilitating the fabrication of electrode materials with enhanced three-phase boundary characteristics for improved fuel cell performance.

A method for producing electrically conductive ceramic membranes based on a fly ash microsphere substrate and a selective layer of alumina nanofibers with a carbon coating is proposed. The formation of a carbon layer by chemical vapor deposition reduces the average pore size from 28 to 19 nm and decreases the water permeability of the membranes from 207 to 45 L/m² h bar. A setup for an electro-baromembrane process was developed, based on a tangential filtration cell with radial flow and the capability of applying a potential to the membrane relative to a counter electrode. Experiments on the ultrafiltration of an aqueous solution of the ionic dye Berillon II showed that the rejection increases from 60 to 82% over time and is provided by the electrostatic interaction of negatively charged dye molecules with the pore surface. Applying a positive potential of +800 mV to the membrane increases the rejection by 20–25% at the beginning of the process and by 13% in the steady state due to enhanced sorption of dye molecules on the membrane surface. Applying a negative potential of –800 mV ensures a stable rejection of 93–96% and a flux of 160 L/m² h at a pressure difference of 5 bar due to the enhanced Donnan exclusion of negatively charged dye molecules in the membrane pores. The obtained results can be used to improve the efficiency of separation, concentration, and purification processes of aqueous solutions of ionic dyes.

This study investigated the physicochemical characteristics and treatment methods for finely dispersed oil-containing wastewater with a dispersed phase particle size of less than 100 nm. For this purpose, both novel composite membranes developed by the authors and commercially available analogs were used. The novelty of the work lies in the development of a method for producing composite membranes comprising a micro-mesh support and a surface layer of cellulose acetate. The developed ultrafiltration membranes consisted of a micro-mesh coated with a layer of cellulose acetate. Nylon was chosen as the base material for the micro-mesh due to its strength and chemical resistance. The pore size of the developed ultrafiltration membranes ranged from 0.05 to 0.1 μm, which allowed for effective separation of oil particles sized 82–86 nm present in the emulsions. Compared to the commercial UPM-100 membrane, the developed membranes demonstrated higher performance and fouling resistance.

Fundamental barrier properties of biomimetic membranes have to be similar to those of biological membranes. Previously, this was demonstrated on many examples for nitrocellulose ultrafilters impregnated with esters of fatty acids. We also discovered that when the filters were impregnated with fatty acids, transmembrane potential starts spontaneous oscillations at or near the melting point of the fatty acid. This effect was observed even when the membrane separated two acidic aqueous solutions with the same ionic composition and without a concentration gradient. Here we describe current oscillations near the melting point, discuss their mechanisms, possible applications and relations to biological channel oscillations.

Increasing the mass transfer rate in electrodialysis allows for a reduction in the area of expensive membranes and, in some cases, lowers the cost of the final product. It has been experimentally established that an increase in the concentration of a KCl solution (from 0.02 to 0.75 M) in the concentrate chamber of a flow-through electrodialysis cell (c_c) leads to a significant growth in the limiting current density (i_lim) through the MA-41P anion-exchange membrane, provided that the desalination chamber contains a solution with a constant concentration (0.02 M KCl). This growth (36% at c_c = 0.5 M) significantly exceeds the value (4%) that could be expected due to the increase in diffusion and electromigration transport of co-ions through the membrane caused by the increase in c_c. As the experiment shows, an increase in c_c leads, on the contrary, to a decrease in the rate of H⁺ and OH^– ion generation at the solution/membrane boundaries, which could also contribute to an increase in the limiting and overlimiting current density. Using voltammetry, chronopotentiometry, and pH-metry, it is shown that the observed growth in i_lim may be associated with the emergence of unstable equilibrium electroconvection, the possibility of which was theoretically predicted in the works of Rubinstein and Zaltzman.

The effect of a natural biocide based on forest chemical raw materials as an additive to cellulose acetate (CA) casting solutions on the structure and properties of the resulting membranes was studied. The NMR method was used to determine the component composition of rosin and turpentine, from which rosin terpene maleic adduct (RTMA) was obtained. Successful modification of the AC-membranes was confirmed by the results of FTIR-spectroscopy. The operational properties of AC-membranes were studied (electron microscopy, atomic force microscopy, study of the transport properties of membranes). It was shown that the introduction of 1.5–2.0 wt % RTMA into the casting solutions does not affect the transport properties of the membranes, but decrease the surface roughness of the selective layer. At the same time, modified membranes are characterized by increased antibacterial resistance and resistance to fungal fouling.