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Introduction. Currently, the purification of wastewater and technological solutions by membrane methods is considered a promising way to neutralize liquid waste. Therefore, the task of developing an engineering method for calculating baromembrane devices is a challenge. Studies on methods involving calculation of design and process variables, membrane equipment design, research of technological features of membrane devices, selection of design schemes, as well as methods of strength and rigidity analysis, are investigated. Materials and Methods. Basic elements of the body of the combined membrane apparatus are considered, a design scheme is proposed, and a method for calculating the strength and rigidity of the main load-bearing element, the cover, is described. Results. The methods determine the required dimensions of shells and plates for the development of a combined membrane apparatus, and evaluate the strength properties of the devices of this class. The construction elements of the apparatus (primarily, the load-bearing covers) must meet not only the requirements of efficiency and quality of separation and cleaning of solutions, but also the conditions for safe operation. Therefore, the design of the device covers should be based on the optimal design dimensions (thicknesses of round plates, toroidal shells, and support rings). To test the method, the stress-strain state of the membrane apparatus structure was calculated for strength and rigidity. As an example, we consider one cover presented in the form of an open toroidal shell. The evaluation of the application of this technique, taking into account the fact that the shell is mated with a round plate in the inner diameter, and with a ring in the outer diameter, has provided the determination of the required parameters. Discussion and Conclusions. The obtained method of analytical description of the mechanical impact on the elements of the combined apparatus and the example of calculating the toroidal shell and plate, enables to evaluate the stressstrain state of the structure for strength and rigidity. The results of the calculation of covers made of various materials at different pressures are presented. Loading the combined apparatus with transmembrane pressure made it possible to determine the required dimensions of the shells and plates for its design and development.

The influence of the structure of the surface cellulose acetate layer on the transport characteristics of ultrafiltration composite membranes is considered using the methods of IR spectroscopy and of scanning electron microscopy. The amorphous phase of ultrafiltration cellulose acetate composite membranes is formed at a certain stage of the technological cycle of obtaining a composite membrane. IR spectra are presented where the forms of the absorption bands of valence vibrations of hydroxylic groups at ν = 3339.14–3366.2 cm–1 alter the asymmetry parameter from ~1 for an air-dry sample and to 0.79 for a water-saturated one, which allows the assertion of formation of volumetric supermolecular structure of a cellulose acetate layer of an air-dry sample by two types of hydrogen bonds and dipole–dipole interactions of carbonyl groups. The decrease of the asymmetry parameter to 0.79 of the absorption bands of hydroxylic groups and of the intensity of absorption bands of methyl groups by 2.56, 3.3, and 3.8 times in water saturated samples of membranes occurs because of the destruction of supermolecular structure and reorganization of hydrogen bonds between the active groups of cellulose acetate and molecules of water. The data obtained by the method of scanning electron microscopy allow one to note that the surface layer of ultrafiltration membranes has an asymmetric pore structure. The surface layer of a membrane can be divided into two components: a selectively permeable layer with pores of small size and a pore substrate, in which the pores increase in their diameter as they approach the substrate.

This paper presents an analytical overview of the study of the kinetic and physicochemical characteristics of composite membrane films. UAM-100, UAM-150, and MGA-95 composite films have been studied using thermogravimetry in the temperature range from 30 to 300°C. A kinetic analysis of experimental data by the Freeman–Carroll method is carried out. It was found that hydrated water for all the studied semi-permeable films evaporates in the temperature range from ~95 to ~180°C. Comparison of the ratios of the amount of removed water in the film samples correlates with the geometric parameters of the pores. The values of the activation energy and the pre-exponential factor (E = 26.9 kJ/mol and ln(A ≈ 6.3 (min–1)) in the range 0.2 < α < 0.7 of the degree of dehydration indicate the same regularity in the distribution of water molecules in the polymolecular layer for all composite films. The high dehydration values, e.g., for a sample of a composite semipermeable film MGA-95 at the temperature of the maximum on the thermogravimetry curve (Tmax = 169.6°C) indicate that water molecules form hydrogen bonds both with ionogenic groups of cellulose acetate and with each other.

Experimental studies and analysis of the effect of transmembrane pressure on the composite porous film material of OFAM-K, OPMN-P membranes and their components by differential scanning calorimetry (DSC), X-ray diffraction analysis and optical microscopy are presented. Investigations of nanofiltration composite materials by differential scanning calorimetry make it possible to study thermal effects that cause changes in the structure and phase transformations with increasing temperature in the membrane sample. X-ray diffraction analysis of the crystalline and amorphous regions of composite films using the radial distribution function allow the change in the unit cells in the membrane polymer sample due to an increase in the interatomic distances to be established. The crystallinity in a membrane sample exposed to transmembrane pressure increases from 44 to 55% due to the appearance of an additional crystalline phase in the film. Optical microscopy studies of the membrane substrate show a morphological feature that resembles fiber compaction, as well as the presence of microscopic voids, which can ultimately be explained by the presence of more knitted fibers in some areas of the membrane.

The paper presents the results of experimental data on the kinetic characteristics of ultrafiltration tubular elements, such as the output specific flow, retention coefficient, diffusion permeability coefficient, distribution coefficient. To study the purification of milk whey, we used tubular ultrafilters BTU 05/2 with membrane material fluoroplast (F), polyethersulfone (PESF), polysulfone (PS). For theoretical calculation of the retention coefficient, output specific flux, diffusion permeability coefficient, distribution coefficient, mathematical expressions were developed and empirical coefficients were obtained. The developed mathematical expression describes the experimental data with good reliability. The obtained experimental and calculated data can be used with high reliability in calculating mass-transfer fluxes of substances through a semi-permeable membrane, as well as in engineering methods for calculating and predicting efficiency, and using membrane processes for concentrating serum. The protein concentration in real milk whey was determined by formol titration. On the basis of the studies carried out, the dependence of the growth of the output specific flow on pressure was established, that the optimal pressure for concentrating milk whey on the ultrafiltration membranes we have chosen is 0.25 MPa. For three types of ultrafilters, the experimental value of the coefficient was within 99% for protein. For the theoretical calculation of the retention coefficient, a program in the MAXIMA language was developed and registered. Due to the method of applying the membrane to the reinforcing element, the membrane material polyethersulfone (PESF) and polysulfone (PS) have a substrate, due to which they sorb more substances on themselves, because of this, the diffusion permeability coefficient and the distribution coefficient are much higher than that of a filter element with membrane made of fluoroplastic (F), which does not have a substrate.

Experimental data have been obtained, and the characteristics of the moisture content and permeability of cellulose acetate porous materials were analyzed via thermal action. Dynamic thermogravimetric analysis found that the destruction process in an air-dry sample of the membrane begins at 21°C. It is accompanied by a 2% weight loss and an endothermic effect. The destruction ends at 50°C. With a subsequent increase in temperature, the manifestation of endothermic effect continues a temperature of 120–175°C with the maximum rate of mass loss at 146°C. The weight loss ends at about 190°C and is 6.5%. The study of MGA-80 and MGA-95 porous cellulose acetate films at transmembrane pressure upon temperature exposure showed that the permeability and specific output flow to water increase as the temperature rises to 50°C. Analysis of dependences of the specific output flow on temperature revealed that the specific output flow to water increases by ~18% upon an initial temperature rise of 10°C. This is due to structural changes in the cellulose acetate layer. A further increase in temperature by 15°C leads to an increase in permeability by ~10%. These phenomena are associated with the process of structural transformation in the active layer and the polymer substrate of the MGA-95 and MGA-80P membranes, respectively.

The paper presents the structural organization of the surface (selective) layer. The amorphous phase of the cellulose acetate composite membrane is formed at a certain stage of the technological cycle of producing the cellulose acetate membrane. It presents a mass of broken, entangled, and twisted macromolecular chains connected by a network of hydrogen bonds of various strengths. Analysis of the IR spectra, where the shapes of the absorption bands of the valence vibrations of hydroxyl groups at ν = 3339.14–3366.2 cm–1 with the asymmetry coefficient varying from ~1 for a dry sample to 0.79 for a wet sample, suggests that the bulk supramolecular structure of the cellulose acetate layer of the air-dry sample is formed by two types of hydrogen bonds and the dipole–dipole interactions of the carbonyl groups. The interactions of macromolecules in the equatorial plane are formed by a network of hydrogen bonds of the OH…O type with the participation of a single hydroxyl group of the pyranose ring in cellulose acetate. In the axial direction, the supramolecular structure is organized through the hydrogen bonds of the CH…O=C type between the methane and carbonyl groups, as well as possibly the dipole–dipole interactions between the coplanar ordered dipoles of the C=O groups. The coefficient of asymmetry of the absorption bands of hydroxyl groups is reduced to 0.81–0.79 and the intensity of the absorption band of methyl groups is reduced by factors of 2.56, 3.3, and 3.8 in water-saturated samples due to the destruction of the supramolecular structure and the reorganization of the hydrogen bonds between the active groups of cellulose acetate and water molecules. The absence of an absorption band of ν = 873.53–851.9 cm–1 in the water-saturated samples indicates a conformational rearrangement of the macromolecules into a linear form with the formation of narrow mesopores of cellulose acetate between the macromolecules.

Results are presented from investigating active and drainage layers of composite films (membranes) UPM-50 and UPM-100 before and after exposure to transmembrane pressure by means of IR spectra of reflection, X-ray scattering, and raster electron microscopy. It is found that changes in the IR spectrum of the working sample are caused by the destruction of weak bonds of C=O···H–N amide fragments of the polysulfonamide film. A drop in (C=O) vibration frequency ν by Δν = 20 cm−1 indicates redistribution of the electron density between C=O-groups and benzene rings as a result of the inductive effect of coupling, which results in the formation of charged functional groups CO−. The presence of CO– groups fragments a new supramolecular structure whose stability due to the dipole–dipole interaction of carbonyl anions. X-ray scattering of the initial and working samples in the 10°–35° range of angles 2θ is determined by three intense reflections at angles 2θ ~ 17.23°, 22.24°, 25.41° from crystallographic planes ((010), (100), and (110)) corresponding to the crystalline structure of lavsan (polyethylene terephthalate). A comparative analysis of the reduced intensities of reflections from crystallographic planes (010), (100) and the sizes of lamellas indicates that transmembrane pressure initiates conformational rearrangement of crystallites with crystallographic axis b oriented parallel to the film plane.

Experimental data on the retention coefficient and the output specific flow are obtained. The test solutions were goat and cow's milk whey after obtaining cheese. The description, general view and technological scheme of a pilot installation of a tubular type are given. The studies were carried out on semipermeable tubular type ultrafiltration membranes manufactured by AO "ZAVKOM". Based on the studies, graphical dependences of the retention coefficient on the specific output stream were constructed and analyzed. During the analysis, it was noted that with an increase in the output specific flow of the solvent, the retention coefficient decreases. The reason for this is the boundary layers of fat and protein formed in the near-membrane layers, which prevents the passage of protein molecules through the pores of the membrane. Also during the experiment, it was noted that goat milk serum has a more oily structure and requires prior separation. For the theoretical calculation of the retention coefficient and specific output stream, mathematical expressions are developed and numerical values of the values of empirical coefficients are obtained. The developed mathematical expressions describe the experimental data with good confidence. The obtained experimental and calculated data can be used with great reliability in the calculations of mass-transported flows of substances through semipermeable membranes, as well as in engineering methods for calculating and predicting the effectiveness of the use of membrane processes for the concentration of whey.

The effect of temperature on the conformation changes of the structural and the thermophysical characteristics in the UAM-50, UAM-100, and MGA-95 composite films of cellulose acetate are studied. An interphase layer appears at the phase interface in the UAM-50 and the UAM-100 samples according to the data of differential scanning calorimetry. An exothermic effect appears in the calorimetry data curves for water-saturated samples in the temperature range of ΔT = 125–226°C with ΔH = 20.7 kJ/kg for the UAM-50 and 27.95 kJ/kg for the UAM-100; this indicates hydration of the polar groups of cellulose acetate and polyamide in the interphase layer of the composite films. When composite films in the air-dried and the water-saturated samples were studied with differential scanning, there was a redistribution of the ratio between the quantities of perfect crystalline structures in crystallites with different melting enthalpies. The melting enthalpy decreases from 6.06 to 0.99 kJ/kg for the MGA-95 low-temperature phase, from 1.99 to 1.72 kJ/kg for the high-temperature phase; from 3.04 to 1.38 kJ/kg for the UAM-50 low-temperature phase, from 8.12 to 1.76 kJ/kg for the high-temperature phase; from 4.99 to 1.5 kJ/kg for the UAM-100 low-temperature phase, and from 2.33 to 0.77 kJ/kg for the high-temperature phase. The total melting enthalpy of the endothermic peaks also decreases for all three samples; this is an indication of decreased crystallinity in the water-saturated samples of the composite films.

An analysis is given of the thermal action on an MGA-95 composite porous film cellulose acetate industrial prototype by differential scanning calorimetry. Investigation of an air-dry sample and a water-saturated sample indicates redistribution of the relation in the quantity of perfect crystal structures in crystallites having different values for the enthalpy of melting, which decreases for the low-temperature phase from 6.06 to 0.99 kJ/kg, and for the high-temperature phase, from 1.99 to 1.72 kJ kg. The total melting enthalpy of the endothermic peaks measures from 8.57 to 6.55 kJ/kg, which points to a reduction in the crystallinity of the water-saturated MGA-95 polymer composite film sample.

Air-dry and water-saturated samples of UAM-50 and UAM-100 composite membranes were studied by X-ray diffractomery (XRD) and differential scanning calorimetry (DSC). A full-profile analysis of the diffraction patterns was performed, and the radial distribution functions (RDFs) of atoms in the drainage layer were constructed. The RDFs generally illustrate the relationship with the geometry of the structure of the air-dry and water-saturated samples. The additional peak with the radii r3 = 6.18 A and r3 = 6.44 A with small coordination numbers in the water-saturated samples suggests that the interplanar space d (hk0) contains the atoms of the water molecules. It was found that water reduces the X-ray crystallinity by 26% in the UAM-50 sample and by 36% in UAM-100. According to the DSC data, an interfacial layer appears at the interface; the DSC curves of the water-saturated samples in the temperature range 125–226°C show an exothermal effect with ΔН = 20.7 kJ/kg for UAM-50 and ΔН = 27.95 kJ/kg for UAM-100, which indicates hydration of the polar groups of cellulose acetate and polyamide in the interfacial layer of the composite films.

Samples of original and working porous composite nanofiltration membranes were investigated by xray scattering, thermal analysis, and study of the specific flow rate and retention coefficient. It was established that mechanical loading due to excess pressure of 1.5 MPa in the OFAM-K membranes leads to conformational changes in the phenylone C-4 macromolecules in the crystalline and amorphous intercrystalline phases, where the calculated degree of crystallinity decreases from 49 to 36%. Investigations by differential-scanning calorimetry indicate homogeneous crystallites with a thermal effect of 7.87 kJ/kg are formed in the working sample of the membrane. The working sample of OPMNP membrane undergoes polymorphous rearrangement of the crystalline phase with a change in the dimensions of the crystalline cell in the direction of the crystal axis (c) and with increase of crystallinity from 44 to 55%, while the amorphous phase becomes looser.

A comparative analysis of the structural evolution of MGA-95 and ESPA1 polymer composite porous films is performed by plotting the radial distribution functions of atoms using empirical X-ray scattering intensity curves and the thermophysical parameters of melting are calculated using data from differential scanning calorimetry (DSC). In the case of the water-saturated MGA-95 sample, the atomic density in the first coordination sphere of the cellulose acetate macromolecule is shown to decrease due to the breaking of intramolecular hydrogen bonds. The atomic density of coordination spheres with radii corresponding to the lattice parameters decreased suggesting spatial disorder of the macromolecules. The DSC data for the MGA-95 film (the enthalpies of melting of the dry and water saturated samples are ΔH = 8.57 and 6.55 J/g, respectively) suggests that sorption of water molecules leads to a decrease in the degree of crystallinity due to a change in the crystalline fractions in the polycrystals. In the case of the ESPA1 composite film, a decrease in the radius and an increase in the atomic density of the first coordination sphere are indicative of the orientational disorder of amorphous phase molecules upon the sorption of water. The appearance of additional coordination spheres with R2 = 3.88 and R3 = 5.26 A in the swollen ESPA1 sample suggests the quantitative redistribution of crystal phases in the substrate material. A detailed analysis of endothermic peaks on the DSC curve shows that the ratio of low- and high-temperature phases varies from 64% : 36% in the dry sample up to 51% : 49% in the water saturated sample at almost identical enthalpies of melting of ΔH = 12.18 and 11.66 J/g, respectively.

The paper examines the specific output stream and the rate of detention of a semi-permeable ultrafiltration membranes, UPM, UAM150, UAM200 in the separation process, waste starch and syrup production JSC., the company "Krakhmaloprodukt" low-pressure baromembrane method. As a result of the analysis of experimental data, the dependence of the retention factor of ultrafiltration membranes UPM-K, UAM150, UAM20 at different concentrations of the dissolved substance was obtained and analyzed. For the theoretical calculation of the process of ultrafiltration separation technology solutions of starch and syrup production modified mathematical expression for the factor of detention and the specific output stream and the numerical values of the empirical coefficients. Ultrafiltration for the separation of waste starch and syrup production the technological scheme of purification, separating the main elements of which was the pre-filter, biofilter, cascade ultrafiltration apparatus, centrifugal and plunger pumps, as well as the adsorption column.The application expediency of the selected apparatus with flat chambers lies in the simplicity of their production technology and in the self-selection possibility of optimum type membranes. It is possible in the presented apparatuses to usemembranes of different types and in the course of the evaluation experiment to establish to what extent they correspond to the most important technological parameters of the process, such as specific output flow, retention factor and resistance to pollution. It is noted that the specific output flow of ultrafiltration membranes decreases with the increase of the initial concentration of the dissolved substance, as the viscosity of the solution increases and its osmotic pressure increases, and the decrease in the retention factor of ultrafiltration membranes is caused by the formation of diffusion boundary layers on the active layer of membranes.

Conformational transformations in the structure of the surface layer and the substrate of initial and working nanofiltration films have been investigated in this work using large-angle X-ray scattering. It has been determined that the mechanical load caused by excess pressure corresponding to 1.5 MPa in the case of OFAM-K porous-composition film has resulted in conformational changes of Phenylon C-4 macromolecules in crystal and amorphous intercrystallite phases; in this case, the calculated degrees of crystallinity have decreased from 49 to 36%. It has been noted that there is the polymorphous rearrangement of the crystal phase with the change of the sizes of crystal cell toward the crystal axis (c) and an increase in the crystallinity from 44 to 55% in the working specimen of the OPMN-P-composition nanofiltration film; in this case, the amorphous phase opens. A full calculation of the radial-distribution function of the atoms of initial and working films has been carried out, which confirms that there is rearrangement of lattice cells due to the increase in atomic distance.

Detailed experimental data are presented on the n-heptane isobaric heat capacity obtained by a modernized adiabatic running calorimeter with the calorimetric measurement of the flow rate in the liquid, gaseous, and supercritical domains, within a temperature range of 300–620 K and a pressure range of 0.5–60 MPa. A thorough consideration of errors made it possible to obtain an error of 0.4% within a wide range of the state parameters. According to the experimental data on the heat capacity, using the known thermodynamics relations, the tables of the n-heptane enthalpy, entropy, and Gibbs energy were calculated (estimated against the accuracy) on the basis of the reliable state equations and the available literature data. The obtained results can be applied directly in the design of chemical processes and the processes in the bedded systems of the hydrocarbon deposits and for development and testing of the equations of state and the methods of the thermodynamic similarity.

The pore space structure of MGA-95 and ESPA membranes has been investigated by the smallangle X-ray scattering (SAXS). The pore radii as the parameters forming the skeleton of the pore space of the reverse-osmosis composite membranes have been established. Three types of scattering pores (sphere, disc, and cylinder) are found in the region of the X-ray scattering vector of 0.171 < s < 0.538 nm−1, and their average radii of gyration have been determined. The pore structure of the MGA-95 and ESPA membranes, which can be described in terms of the self-affine fractal concept, has been revealed. In the region of the scattering vector of 0.245 < s < 0.342 nm−1 (the average pores with 9.2 < r