Petroleum Chemistry (v.53, #7)
Experimental study of the effect of high pressure on the efficiency of whey nanofiltration process using an OPMN-P membrane by V. G. Myronchuk; I. O. Grushevskaya; D. D. Kucheruk; Yu. G. Zmievskii (439-443).
The results of experimental investigation of the separation of milk whey with the use of OPMN-P nanofiltration membranes (Vladipor, Russia) at pressures of 1.6–6 MPa are presented. A dead-end membrane cell has been used for the experiments. Both the whole whey (without pretreatment) and the whey after microfiltration alone or micro- and ultrafiltration have been subjected to separation. It has been shown that the working pressure range of OPMN-P membranes can be extended from 1.6 to 5 MPa. The highest specific productivity and selectivity for lactose have been observed during the separation of whey ultrafiltration permeates. The presence of residual fats and proteins in the whey reduces the specific productivity. On the basis of calculation of the specific energy consumption, it has been concluded that a high pressure (5 MPa) is useful only for separation of whey ultrafiltration permeates.
Keywords: nanofiltration; whey; selectivity
A performance criterion for substance separation processes by E. P. Ageev; N. N. Matushkina; N. L. Strusovskaya (444-446).
A new criterion is proposed for evaluating the efficiency of separation processes—the selective flux of a pure desired component, which includes both concentration changes and the productivity of a separation apparatus. An algorithm for calculating the proposed criterion is given, the concept of the efficiency coefficient is introduced, and its relationship with the degree of selective separation of a binary solution is demonstrated.
Keywords: separation processes; selective flux; desired component; performance criterion
Investigation of permeability of fluorinated polycarbonate siloxanes by D. O. Anashkin; L. E. Strannikova; V. M. Kopylov; I. M. Raigorodskii (447-453).
Mass transfer properties of fluorinated polycarbonate siloxanes (PCS-F) for some gases and hydrocarbons depending on the chemical nature of the carbonate and siloxane blocks and the composition of the block copolymers have been investigated. As compared with poly(dimethylsiloxane)s, polycarbonate siloxanes, and methyltrifluoropropylsiloxane homopolymers, fluorinated polycarbonate siloxanes exhibit a higher separation selectivity α for CO2/N2, CO2/O2, and CO2/CH4. At a 30 wt % concentration of trifluoropropyl groups, PCS-F have α values of 4.9 and 17.8 for O2/N2 and CO2/CH4, respectively. The PCS-F copolymers exhibit a high resistance to hydrocarbons, retaining the mechanical properties in the swollen state.
The influence of surface flow on permeability anisotropy by A. V. Kryukov; I. M. Kurchatov; N. I. Laguntsov (454-459).
The influence of surface diffusion on the anisotropy of gas permeation through a two-layer nanoporous membrane has been studied. A model of gas transport in the bilayer membrane for the case of a gas flow composed of free molecular and surface flows has been constructed, wherein the scattering of molecules on the surface is defined by the “white noise” model. The influence of the surface diffusion on the anisotropy of gas permeability through the nanoporous bilayer membrane in the case of anisotropic scattering of gas molecules from the inner surface of the pores has been analyzed.
Keywords: two-layer membrane; anisotropy; nonsymmetric transport; surface diffusion; gas transport; nanoporous membranes
Noble gases as indicators of molecular-selective gas transport in polymeric membranes by I. N. Beckman; A. Yu. Golub; A. V. Yakovlev; V. V. Teplyakov (460-470).
Methods of estimation of molecular-selective gas transport parameters in polymeric membranes and explanation of separation selectivity evolution for ‘small’ and ‘large’ molecules up to inversed selectivity are proposed based on comparative analysis of diffusion and solubility of noble gases as isotropic diffusion probes in different classes of polymers and block copolymers on their basis. Two approaches are considered in this work: (1) analysis of diffusional migration of permanent gases, lower hydrocarbons, and alcohols (vapor) in glassy polymers and rubbers relative to the diffusion of noble gases including radon; (2) adaptation of the ‘hard sphere’ theory developed for gas solubility in liquids to the calculation of the solubility of gases in the polymer matrix. In the latter case, noble gases as isotropic probes are used for calculating the required fitting parameters of the polymer medium.
Keywords: gas diffusion in inhomogeneous media; parameters of noble gas permeability in polymers; methods for assessment of permeability of permanent gases and lower hydrocarbons
Methods for modification of track-etched membranes designed for separation of biological objects by E. Kh. Fatiyants; V. V. Berezkin; G. G. Kagramanov (471-481).
The existing and promising methods for modification of track-etched membranes are considered and analyzed; they are compared for subsequent separation of biological objects. On the basis of the results of comparative analysis, the simplest and most producible method of modification of track-etched membranes has been chosen.
Keywords: track-etched membranes; biological object; poly(ethylene terephthalate); track membrane modification methods; adsorption activity; hydrophilic-hydrophobic properties; selectivity; specific productivity
Effect of process parameters of manufacturing of composite fibrous membranes on their structure and ion selectivity by M. M. Kardash; Yu. M. Vol’fkovich; I. A. Tyurin; N. A. Kononenko; D. V. Oleinik; M. A. Chernyaeva (482-488).
The porous structure of Polikon K composite ion-exchange membranes based on polyacrylonitrile fibers has been studied by standard contact porosimetry. Differences in maximum porosity, internal specific surface area, macropore volume, and other structural characteristics attributed to the use of different molding pressures during the preparation of the membranes have been revealed. According to the analysis of the porometric curves measured in octane and water, it has been found that the volume of hydrophobic pores in the Polikon membranes is an order of magnitude lower than the total volume of hydrophilic pores. The ion selectivity of the membrane materials has been estimated from the porometric curves. A comparison of the ion transport numbers measured by the potentiometric method to the calculated values has shown that they are in good agreement.
Keywords: composite fibrous membranes; standard contact porosimetry; effective pore radius; internal specific surface area; ion selectivity
Hydrogen production by electrochemical reforming of ethanol by A. A. Murashkina; D. A. Medvedev; V. S. Sergeeva; A. K. Demin (489-493).
The theoretical analysis of processes occurring in the solid oxide electrochemical reformer based on the oxide conductor with mixed ion-electron conductivity has been carried out. Three versions of the preliminary conversion of the initial fuel (ethanol), namely, partial oxidation, steam reforming, and recycling by the anode effluent gas mixture have been considered. The last version is shown to feature the highest fuel conversion efficiency and hydrogen yield.
Keywords: reforming; synthesis gas; hydrogen; membranes
Effect of chromium compounds on the properties of ion-exchange membranes by S. V. Shishkina; E. A. Zhelonkina; T. V. Kononova (494-499).
The transport properties of ion-exchange membranes MK-40 and MF-4SK, MA-40, and MA-41 in solutions of sodium chloride, chromium(III) chloride, and chromium(VI) oxide have been studied. It has been found that the MA-40 and MA-41 membranes retain their transport properties in chromium chloride(III) solutions, whereas the anion-exchange membranes in chromium(VI) oxide solutions undergo partial or complete degradation. The oxidative impact of chromate ions on both the hydrocarbon matrix of the MK-40 membranes and the chemically resistant perfluorocarbon matrix of the MF-4SK membrane has been revealed.
Keywords: ion-exchange membrane; moisture content; electrical conductivity; IR spectrum
Investigation of bactericidal properties of modified polyamide membranes by A. V. Tarasov; S. A. Lepeshin; Yu. A. Fedotov; O. V. Pruntova; A. I. Fedotova; V. A. Tverskoi; Yu. T. Panov (500-503).
Bulk and surface modified polyamide microfiltration membranes have been investigated. Silver compounds and compounds containing quaternary ammonium groups were used as bactericidal agents. Surface modification with silver compounds and polyhexamethylene guanidine allow for production of membranes with bacteriostatic properties.
Keywords: polyamide membrane; modification; bactericidal properties; silver; chitosan; polyhexamethylene guanidine
Ion transport in hybrid membranes based on MF-4SC and silica surface-modified with proton acceptor groups by A. G. Mikheev; E. Yu. Safronova; A. B. Yaroslavtsev (504-510).
Methods for synthesizing hybrid MF-4SC membranes containing silica whose surface has been modified with proton acceptor amine-containing groups (3-aminopropyl- and 3-(2-imidazoline-1-yl)-propyl-) are proposed. The incorporation of surface-modified silica particles into the membrane matrix leads to a decrease in the water uptake and exchange capacity compared to a membrane containing pure SiO2. The proton conductivity and diffusion permeability of NaCl and HCl solutions and the H+/Na+ ion interdiffusion are studied. The proton conductivity of the membranes containing surface-modified silica is higher than that of the parent membrane and the membrane containing pure SiO2. It is shown that the surface modification of silica with 5 mol % of nitrogen-containing groups results in a decrease in the diffusion permeability and an improvement in the ion transport selectivity. This extraordinary change in the properties is caused by an increase in the size of the pores and the channels that connect them, along with a significant decrease in the free volume within the pores. At the same time, an increase in the amount of modifying groups to 10 mol % leads to a sharp acceleration of the diffusion permeability and interdiffusion processes because of the formation of through pores in the membrane matrix.
Keywords: hybrid membranes; ion transport; selectivity
Features of electrical breakdown of metal-coated track-etched membranes with cylindrical pores by S. N. Podoinitsyn; T. V. Tsyganova; B. V. Mchedlishvili (511-513).
Current-voltage characteristics and electrical breakdown have been investigated for metal-coated track-etched membranes with cylindrical pores. The specific features of current flow through a dielectric membrane that are associated with the presence of field-emission nanostructures on its surface have been revealed. The results are of interest for solving engineering problems of fabrication of field-emission nanostructures based on metal-coated track-etched membranes.
Keywords: track-etched membranes; metal-coating; field-emission nanostructures; current-voltage characteristic; breakdown
Composite polyacrylonitrile membranes with antibacterial properties by N. V. Potvorova; P. V. Vakuliuk; I. M. Furtat; A. F. Burban (514-520).
Techniques for preparing composite polyacrylonitrile membranes by immobilizing natural or synthetic compounds on their surface have been developed, and their transport, functional, and antibacterial properties have been studied. It has been found that the membranes with complexes immobilized on their surface exhibit a long-term antibacterial activity against gram-negative bacteria Escherichia coli HB 101.
Keywords: composite polyacrylonitrile membranes; immobilization; modification; photoinitiated polymerization; antibacterial properties
Investigation of the morphology of polymer-inorganic capillary membranes based on polysulfone by A. V. Bil’dyukevich; T. V. Plisko; G. A. Branitskii; N. G. Semenkevich; I. L. Zharkevich (521-528).
Capillary ultrafiltration membranes based on polysulfone and tin hydroxo compounds have been prepared by the phase inversion method. The formation of colloidal particles of tin hydroxo compounds in the membrane matrix has been carried out during the membrane formation process by hydrolysis of tin(II) chloride dihydrate, a component of the forming solution, in contact with the inner coagulating agent (water). The morphology and transport properties of the polymer-inorganic membranes have been studied. By using a digital image analysis program, it has been found that the addition of tin(II) chloride dihydrate to the forming solution increases the porosity, decreases the average pore size, and narrows the pore size distribution in the selective layer of the membrane. It has been revealed that the polymer-inorganic membranes are characterized by higher productivity and a lower retention compared with the unmodified membranes.
Keywords: ultrafiltration; polysulfone; capillary membranes; pore size distribution; inorganic additive
Electroreduction of molecular oxygen on the silver/perfluorinated ion-exchange membrane MF-4SK/dispersed carbon nanocomposite by V. V. Novikov; M. Yu. Chaika; T. A. Kravchenko (529-536).
By chemical deposition of silver in an ion-exchange matrix, the Ag0/MF-4SK/C nanocomposite has been fabricated, which is capable of changing the amount of deposited silver by varying the concentration of ionic groups in the MF-4SK membrane. Transmission electron microscopy has revealed the presence of silver particles of a 3 nm size. On an electrode coated with the MF-4SK membrane, electroreduction of oxygen occurs on the carbon substrate and the membrane is a diffusion barrier. Since the polymer matrix contains counterions H+ localized near fixed −SO3 groups, the hydrogen ion takes part in the stage of charge transfer to the oxygen molecule. An increase in the dioxygen electroreduction current on the Ag0/MF-4SK/C nanocomposite relative to the MF-4SK/C composite is due to the presence of silver particles, which result in acceleration of the reaction by the catalytic action, and to an increased contribution of the four-electron process as compared with the two-electron process characteristic of carbon materials.
Keywords: electroreduction of oxygen. composite electrode. silver; ion-exchange matrix
Nanofiltration of dye solutions through membranes based on poly(trimethylsilylpropyne) by S. E. Tsar’kov; A. O. Malakhov; E. G. Litvinova; A. V. Volkov (537-545).
Nanofiltration of dilute dye solutions in normal alcohols through membranes based on the glassy polymer poly(trimethylsilylpropyne) has been investigated. It has been found that the membrane separation properties substantially depend not only on the dye nature, but also on the properties of the solvent used. In particular, the retention of Solvent Blue 35 may be either positive (when the permeate is depleted in dye) or negative (permeate enriched in dye) depending on the type of the solvent. It has been revealed that the retention of the dyes by the polymer membrane correlates with the thermodynamic affinity of the components in the polymer-solvent-dye system and is almost linearly related to the partition coefficient between the membrane dye and the feed solution.
Keywords: nanofiltration; dyes; alcohols; poly(trimethylsilylpropyne); retention
Sorption of solutions complicated by the crystallization of a polymer sorbent by E. P. Ageev; N. L. Strusovskaya; N. N. Matushkina (546-548).
The sorption of a liquid polymer solution have been studied as a function of experimental conditions, and the experimental results are discussed taking into account the chemical nature of the sorbate and the sorbent and the structure of the polymer. An algorithm of successive actions is given; it shows the effect of the structure of aqueous organic solutions on their sorption by semicrystalline polyethylene terephthalate.
Keywords: polymer crystallization; active and inactive components; polymer strength; crystallinity; sorption