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Vol 15, No 1 (2025)
Articles
Introduction
3-4
Polyamides in Membrane Technology
Abstract
The issues of synthesis, structure and application of aromatic polyamides are considered. Unique thermal, physical-mechanical and chemical properties of these polymers have opened up possibilities of their use as functional and ultramodern materials. The variety of tools used in the creation and modification of aromatic polyamides makes it possible to „customize“ their properties for specific tasks, which makes aromatic polyamides truly universal for various industries, including membrane technologies.
7-21
Ion Transport Asymmetry in Hybrid Membranes MF-4SK with Gradient Distribution of Hydrated Silicon Oxide, Including Modified Surface
Abstract
The paper presents the results of investigation of properties of hybrid materials based on homogeneous membrane MF-4SC with gradient distribution of dopant along the thickness. Hydrated silicon oxide nanoparticles, including those with a functionalized surface containing proton acceptor groups, were used as dopant. The presence of asymmetry of diffusion permeability of HCl and NaCl solutions of the studied membranes was revealed. It is shown that the diffusion permeability depends on the orientation of the membrane with respect to the electrolyte solution and the asymmetry reaches 65%. Depending on the surface properties of the introduced silicon oxide (on the nature and size of grafted groups) the direction of preferential ion transport changes. The causes of the diffusion permeability asymmetry and factors determining its direction are described.
22-32
Distillation of Nonelectrolyte Solutions Using Reverse Osmosys Hydrophilic Membranes
Abstract
A mathematical model of membrane distillation of aqueous solutions of organic substances (alcohols) using hydrophilic membranes has been developed. The membrane is modeled as a capillary-porous body all the pores of which are rectilinear capillaries of the same length and radius. The study was carried out for moderately intense processes, when the radius of curvature of the meniscus of a cylindrical pore exceeds the radius of the capillary, that is, there is no deepening of the evaporation front. An analytical formula was obtained, its parametric study was carried out and the extreme behavior of the separation coefficient of the most membrane-trapped component of the mixture was revealed depending on the concentration of solvent vapor in the blowing gas stream, which qualitatively corresponds to the behavior of this coefficient during the pervaporation of aqueous ethanol solutions using crosslinked hydrophilic pullulane membranes and hydrophilic chitosan membranes, as well as chitosan membranes crosslinked with glutaraldehyde.
33-43
Stability of Polymer Composite Membranes Based on Fluorinated Polysiloxanes under Tropical Conditions
Abstract
One of the key objectives of membrane technology is to improve the resistance to fouling (fouling) and degradation of membrane surface. In this work, the stability properties of selective layer based on fluorinated polysiloxanes were investigated during exposure for 6 months at climatic sites in Vietnam. Three composite membranes on MFFC-1 microfiltration substrate with selective layers: 1) polydecimethylsiloxane (C10), 2) copolymer of C10 and polysiloxane with trifluoroalkylacrylate side group (C10-F3), 3) copolymer of C10 and polysiloxane with perfluorooctyl side group (C10-PFO) were investigated in this work. A comparison of changes in the composition and surface properties of the selective layer, as well as gas transport properties before and after exposure to the test sites was analyzed. It is shown that for membranes based on fluorine-containing polysiloxanes (C10-F3 and C10-PFO) less clogging and degradation of the selective layer polymer is observed. For sample C10, destruction of side alkyl fragments and increase in the concentration of oxygen atoms on the surface of the selective layer was observed, including due to the deposition of microalgae. Membranes C10-F3 showed the greatest stability of gas permeability by CO2 and N2 (change not more than 10%) and the least oxidative degradation.
44-62
Estimation of Polyelectrolyte Ionic Conductivity Using Molecular Dynamics Method
Abstract
This paper describes the procedure of developing a protocol for theoretical evaluation of the ionic conductivity of two polyelectrolyte systems consisting of oligomers simulating the lithium form of the Nafion-115 membrane plasticized in one case with dimethyl sulfoxide and in the other case with propylene carbonate. Model systems for theoretical calculations were constructed according to the values of the degree of swelling of the membrane in the mentioned solvents determined experimentally. The protocol for molecular dynamic simulations was selected taking into account the peculiarities of the structure and physicochemical properties of the components of the investigated systems. The analysis of molecular dynamic simulations trajectories included the evaluation of radial distribution functions and self-diffusion coefficients. The author’s code written in the Python language was used to calculate ionic conductivity. The results of the theoretical calculations are in agreement with the experimental data. The modeling approach proposed in this work can be used for relatively fast estimation of ionic conductivity in similar electrolyte systems in a close temperature range up to the phase transition boundary.
63-75
Reagent-Free Methods for Reducing the Amount of Concentrate from Reverse Osmosis Plants
Abstract
Of all developed water desalination processes, reverse osmosis takes the leading place - 69% of the world’s fresh water production is attributed to reverse osmosis plants, one of the efficiency criteria of which is the amount of concentrate produced. The article describes some modern baromembrane reagentless methods of reducing the amount of concentrate of reverse osmosis plants, the main criterion for the selection of which is the experience of their industrial application. Such processes as forward osmosis, pressure assisted forward osmosis, osmotically assisted reverse osmosis, semi-batch reverse osmosis, pulse flow reverse osmosis are considered, their working principle and results of practical application in industry or large-scale pilot tests are given.
76-86