Ultrafiltration and nanofiltration membranes that are traditionally used in baromembrane processe... more Ultrafiltration and nanofiltration membranes that are traditionally used in baromembrane processes have become increasingly frequently applied in electromembrane and baroelectromembrane processes. In the latter case, two driving forces, an electric field and a pressure gradient, are simultaneously used. This study presents data on the specific electrical conductivity, diffusion permeability, and transport numbers of ions as well as current-voltage characteristics and chronopotentiograms of AMN-P and OPMN-P weakly ionized nanofiltration membranes and a number of track membranes in solutions of NaCl and CaCl 2. The relationship of obtained characteristics with the structure and exchange capacity of membranes is discussed. It is shown that both nanofiltration and track membranes can exhibit a quite high selectivity towards the electrical transport of ions with a certain charge sign. Such selectivity is especially high in respect of the transport of Ca 2+ ions. In the case of an AMN-P membrane, the transport number of Ca 2+ reaches 0.98, while it is noticeably lower for Na + ions. This result correlates well with a known fact about a higher rejection coefficient of doubly charged ions in comparison with singly charged ions in baromembrane processes. Track membrane #115 is also distinguished by high selectivity in respect of cations, the transport number of sodium ions in it is close to 0.96.
A promising solution for the implementation of extraction processes is liquid–liquid membrane con... more A promising solution for the implementation of extraction processes is liquid–liquid membrane contactors. The transfer of the target component from one immiscible liquid to another is carried out inside membrane pores. For the first time, highly asymmetric track-etched membranes made of polyethylene terephthalate (PET) of the same thickness but with different pore diameters (12.5–19 nm on one side and hundreds of nanometers on the other side) were studied in the liquid–liquid membrane contactor. For analysis of the liquid–liquid interface stability, two systems widely diverging in the interfacial tension value were used: water–pentanol and water–hexadecane. The interface stability was investigated depending on the following process parameters: the porous structure, the location of the asymmetric membrane in the contactor, the velocities of liquids, and the pressure drop between them. It was shown that the stability of the interface increases with decreasing pore size. Furthermore, i...
A combination of a long exposure to ultraviolet (UV) radiation and the extraction of radiolysis a... more A combination of a long exposure to ultraviolet (UV) radiation and the extraction of radiolysis and photolysis products from tracks makes it possible to create ion-selective membranes from polyethylene terephthalate (PET) films irradiated with heavy ions. These membranes exhibit high selectivity for singly charged cations and high transport characteristics in the electrodialysis mode. The aim of this study is to analyze the mechanisms of the transformation of latent tracks into a system of through pores of the subnanometer range in more detail. Polyethylene terephthalate films are irradiated with accelerated Xe and Bi ions with energy losses in the polymer of 11 and 18 keV/nm, respectively. The evolution of the free volume and the accumulation of carboxyl groups in the irradiated films at different stages of the treatment are studied using gravimetry, IR and UV spectroscopy, conductometry, and electron microscopy methods. It is found that the properties of the resulting membranes depend on several critical parameters, which include, in addition to temperature during extraction, the energy loss of the bombarding ion, the pH of the solution used for extraction, and ion fluence. Dramatic changes in the membrane properties are observed at ion fluences at which individual tracks begin to overlap.
The great potential of nanoporous membranes for water filtration and chemical separation has been... more The great potential of nanoporous membranes for water filtration and chemical separation has been challenged by the trade-off between selectivity and permeability. Here we report on nanoporous polymer membranes with an excellent balance between selectivity and permeability of ions. Our membranes are fabricated by irradiating 2-μm-thick polyethylene terephthalate Lumirror® films with GeV heavy ions followed by ultraviolet exposure. These membranes show a high transport rate of Kions of up to 14 mol h mand a selectivity of alkali metal ions over heavy metal ions of >500. Combining transport experiments and molecular dynamics simulations with a polymeric nanopore model, we demonstrate that the high permeability is attributable to the presence of nanopores with a radius of ~0.5 nm and a density of up to 5 × 10 cm, and the selectivity is ascribed to the interaction between the partially dehydrated ions and the negatively charged nanopore wall.
International Journal of Radiation Applications and Instrumentation. Part D. Nuclear Tracks and Radiation Measurements
The changes occurring in thin polyethylene terephthalate (PETP), polycarbonate (PC) and polypropy... more The changes occurring in thin polyethylene terephthalate (PETP), polycarbonate (PC) and polypropylene (PP) films irradiated with heavy ions have been investigated. The track etching properties were studied in the submicroscopic diameter range of 1-60 rim. The method of absorption spectroscopy in ultraviolet (u.v.) and infrared (i.r.) regions, viscosimetry of polymer solution and sol-gel analysis were used to investigate radiation chemical processes in the polymers. It has been found that in all three polymers both the chain rupture and cross-linking processes occur simultaneously. The chain ruptures predominate in the track core with a diameter of several nanometers. The cross-linking process takes place in the vicinity of the track core at radii of up to 30-50 nm and appears most clearly in PETP where cross-linking events prevail over the destruction at large distances from the ion path.
International Journal of Radiation Applications and Instrumentation. Part D. Nuclear Tracks and Radiation Measurements
The radial structure of the etch~ble tracks of multiply charged ions in polethylene terephthalate... more The radial structure of the etch~ble tracks of multiply charged ions in polethylene terephthalate, polycarbonate, polyarylate and polypropylene is investigated using the conductametric method. It is found that the track of a highly ionizing particle in a polymer consists of a core in which intensive destruction occurs and a halo where thc cross linking of macromolecules may predominate. A hypothesis is proposed that the cross linking of a polymer in the track halo is conditioned by the effect of the hydrogen ions and atoms which are generated in the track core due to the ion explosion spike mechanism and diffuse to the surrounding space.
International Journal of Radiation Applications and Instrumentation. Part D. Nuclear Tracks and Radiation Measurements
In this review the status of the technical and scientific problems associated with the nuclear tr... more In this review the status of the technical and scientific problems associated with the nuclear track membranes is briefly given. The main results obtained in the recent years are presented.
The propagation of ultrasonic waves in the cylindrical micro-pores (pore diam. <1 μm) of ion-trac... more The propagation of ultrasonic waves in the cylindrical micro-pores (pore diam. <1 μm) of ion-track membranes (ITMs) is studied. This membrane fabrication technique provides unique possibilities to obtain cylindrical micro-pores with a very high degree of accuracy in pore shape, size, and orientation. Several ITMs were specially produced having the same pore diameter, orientation, and geometry, but different thickness. Porosity, pore diameter, and shape were determined using scanning electron microscopy, and then the coefficient of ultrasound transmission was measured using air coupling and spectral analysis. These experimental conditions permit us to eliminate the influence of the boundary conditions and to achieve a strong decoupling between the fluid filling the pores and the solid constituent of the membrane. Hence, the velocity and the attenuation coefficient for ultrasound propagation in the pores can be measured. These parameters are compared with the predictions made by conventional theories for sound propagation in porous media and in cylindrical channels. The conclusions of this work provide a better understanding of wave propagation in micro-pores and establish the basis of an ultrasonic porometry technique for ITMs.
Ultrafiltration and nanofiltration membranes that are traditionally used in baromembrane processe... more Ultrafiltration and nanofiltration membranes that are traditionally used in baromembrane processes have become increasingly frequently applied in electromembrane and baroelectromembrane processes. In the latter case, two driving forces, an electric field and a pressure gradient, are simultaneously used. This study presents data on the specific electrical conductivity, diffusion permeability, and transport numbers of ions as well as current-voltage characteristics and chronopotentiograms of AMN-P and OPMN-P weakly ionized nanofiltration membranes and a number of track membranes in solutions of NaCl and CaCl 2. The relationship of obtained characteristics with the structure and exchange capacity of membranes is discussed. It is shown that both nanofiltration and track membranes can exhibit a quite high selectivity towards the electrical transport of ions with a certain charge sign. Such selectivity is especially high in respect of the transport of Ca 2+ ions. In the case of an AMN-P membrane, the transport number of Ca 2+ reaches 0.98, while it is noticeably lower for Na + ions. This result correlates well with a known fact about a higher rejection coefficient of doubly charged ions in comparison with singly charged ions in baromembrane processes. Track membrane #115 is also distinguished by high selectivity in respect of cations, the transport number of sodium ions in it is close to 0.96.
A promising solution for the implementation of extraction processes is liquid–liquid membrane con... more A promising solution for the implementation of extraction processes is liquid–liquid membrane contactors. The transfer of the target component from one immiscible liquid to another is carried out inside membrane pores. For the first time, highly asymmetric track-etched membranes made of polyethylene terephthalate (PET) of the same thickness but with different pore diameters (12.5–19 nm on one side and hundreds of nanometers on the other side) were studied in the liquid–liquid membrane contactor. For analysis of the liquid–liquid interface stability, two systems widely diverging in the interfacial tension value were used: water–pentanol and water–hexadecane. The interface stability was investigated depending on the following process parameters: the porous structure, the location of the asymmetric membrane in the contactor, the velocities of liquids, and the pressure drop between them. It was shown that the stability of the interface increases with decreasing pore size. Furthermore, i...
A combination of a long exposure to ultraviolet (UV) radiation and the extraction of radiolysis a... more A combination of a long exposure to ultraviolet (UV) radiation and the extraction of radiolysis and photolysis products from tracks makes it possible to create ion-selective membranes from polyethylene terephthalate (PET) films irradiated with heavy ions. These membranes exhibit high selectivity for singly charged cations and high transport characteristics in the electrodialysis mode. The aim of this study is to analyze the mechanisms of the transformation of latent tracks into a system of through pores of the subnanometer range in more detail. Polyethylene terephthalate films are irradiated with accelerated Xe and Bi ions with energy losses in the polymer of 11 and 18 keV/nm, respectively. The evolution of the free volume and the accumulation of carboxyl groups in the irradiated films at different stages of the treatment are studied using gravimetry, IR and UV spectroscopy, conductometry, and electron microscopy methods. It is found that the properties of the resulting membranes depend on several critical parameters, which include, in addition to temperature during extraction, the energy loss of the bombarding ion, the pH of the solution used for extraction, and ion fluence. Dramatic changes in the membrane properties are observed at ion fluences at which individual tracks begin to overlap.
The great potential of nanoporous membranes for water filtration and chemical separation has been... more The great potential of nanoporous membranes for water filtration and chemical separation has been challenged by the trade-off between selectivity and permeability. Here we report on nanoporous polymer membranes with an excellent balance between selectivity and permeability of ions. Our membranes are fabricated by irradiating 2-μm-thick polyethylene terephthalate Lumirror® films with GeV heavy ions followed by ultraviolet exposure. These membranes show a high transport rate of Kions of up to 14 mol h mand a selectivity of alkali metal ions over heavy metal ions of >500. Combining transport experiments and molecular dynamics simulations with a polymeric nanopore model, we demonstrate that the high permeability is attributable to the presence of nanopores with a radius of ~0.5 nm and a density of up to 5 × 10 cm, and the selectivity is ascribed to the interaction between the partially dehydrated ions and the negatively charged nanopore wall.
International Journal of Radiation Applications and Instrumentation. Part D. Nuclear Tracks and Radiation Measurements
The changes occurring in thin polyethylene terephthalate (PETP), polycarbonate (PC) and polypropy... more The changes occurring in thin polyethylene terephthalate (PETP), polycarbonate (PC) and polypropylene (PP) films irradiated with heavy ions have been investigated. The track etching properties were studied in the submicroscopic diameter range of 1-60 rim. The method of absorption spectroscopy in ultraviolet (u.v.) and infrared (i.r.) regions, viscosimetry of polymer solution and sol-gel analysis were used to investigate radiation chemical processes in the polymers. It has been found that in all three polymers both the chain rupture and cross-linking processes occur simultaneously. The chain ruptures predominate in the track core with a diameter of several nanometers. The cross-linking process takes place in the vicinity of the track core at radii of up to 30-50 nm and appears most clearly in PETP where cross-linking events prevail over the destruction at large distances from the ion path.
International Journal of Radiation Applications and Instrumentation. Part D. Nuclear Tracks and Radiation Measurements
The radial structure of the etch~ble tracks of multiply charged ions in polethylene terephthalate... more The radial structure of the etch~ble tracks of multiply charged ions in polethylene terephthalate, polycarbonate, polyarylate and polypropylene is investigated using the conductametric method. It is found that the track of a highly ionizing particle in a polymer consists of a core in which intensive destruction occurs and a halo where thc cross linking of macromolecules may predominate. A hypothesis is proposed that the cross linking of a polymer in the track halo is conditioned by the effect of the hydrogen ions and atoms which are generated in the track core due to the ion explosion spike mechanism and diffuse to the surrounding space.
International Journal of Radiation Applications and Instrumentation. Part D. Nuclear Tracks and Radiation Measurements
In this review the status of the technical and scientific problems associated with the nuclear tr... more In this review the status of the technical and scientific problems associated with the nuclear track membranes is briefly given. The main results obtained in the recent years are presented.
The propagation of ultrasonic waves in the cylindrical micro-pores (pore diam. <1 μm) of ion-trac... more The propagation of ultrasonic waves in the cylindrical micro-pores (pore diam. <1 μm) of ion-track membranes (ITMs) is studied. This membrane fabrication technique provides unique possibilities to obtain cylindrical micro-pores with a very high degree of accuracy in pore shape, size, and orientation. Several ITMs were specially produced having the same pore diameter, orientation, and geometry, but different thickness. Porosity, pore diameter, and shape were determined using scanning electron microscopy, and then the coefficient of ultrasound transmission was measured using air coupling and spectral analysis. These experimental conditions permit us to eliminate the influence of the boundary conditions and to achieve a strong decoupling between the fluid filling the pores and the solid constituent of the membrane. Hence, the velocity and the attenuation coefficient for ultrasound propagation in the pores can be measured. These parameters are compared with the predictions made by conventional theories for sound propagation in porous media and in cylindrical channels. The conclusions of this work provide a better understanding of wave propagation in micro-pores and establish the basis of an ultrasonic porometry technique for ITMs.
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Papers by Pavel Apel