Илья Рыжков - Academia.edu (original) (raw)
Papers by Илья Рыжков
The pressure–driven electrolyte transport through nanofiltration membrane pores with specified wa... more The pressure–driven electrolyte transport through nanofiltration membrane pores with specified wall po- tential is investigated theoretically. The finite ion size effect is taken into account by introducing an additional term to electrochemical potential. The two–dimensional Navier–Stokes, Poisson, and modified Nernst–Planck equations are solved numerically in a high aspect ratio nanopore connecting two reservoirs with a larger diameter. The calculations are performed for potassium chloride aqueous solution. In the case of point–like ions, the non–physical rise of counter–ion concentration is observed near the pore wall at large applied voltages. When finite ion size is taken in account, the concentration of counter–ions decreases significantly and saturates to the maximum value. It leads to lower osmotic pressure jump and larger magnitude of potential in the pore. The stronger co–ion depletion observed for finite size ions results in the increase of salt rejection, membrane potenti...
The diffusion of binary aqueous electrolytes through nanopores with dielectric as well as conduct... more The diffusion of binary aqueous electrolytes through nanopores with dielectric as well as conductive surface is investigated theoretically on the basis of Space–Charge model. The latter is extended to the case of polarizable nanopore wall. It is shown that the diffusion of ions with different mobilities generates the electric field, which induces non–uniform surface charge in a polarizable nanopore. It results in charge separation inside the pore and leads to a dramatic enhancement of membrane potential in comparison with a non–polarizable nanopore. The calculations are performed for three aqueous electrolytes based on KCl, NaCl, and LiOH. The influence of electrolyte type and concentration difference applied across the pore on the ion transport and membrane potential is discussed and analyzed.Проведено теоретическое исследование диффузии бинарных электролитов через нанопоры с диэлектрической, а также проводящей поверхностью на основе модели пространственного заряда. Данная модель о...
Journal of Siberian Federal University. Mathematics and Physics, 2021
The ionic conductivity of nanopores with electrically conductive surface is investigated theoreti... more The ionic conductivity of nanopores with electrically conductive surface is investigated theoretically. The generalization of two-dimensional (2D) Space–charge model to calculating the ion transport under the applied potential gradient in a nanopore with constant surface potential is proposed for the first time. The results are compared with one-dimensional (1D) Uniform potential model, which is derived from the Space–charge model by assuming the independence of potential, ion concentrations, and pressure on the radial coordinate. We have found that the increase of surface potential magnitude leads to the enhancement of conductivity due to the increase of counter–ion concentration inside the nanopore. It is shown that the 1D and 2D models provide close results when the pore radius is smaller than the Debye length. Otherwise, the 1D model essentially overestimates the ionic conductivity. According to the 2D model, the ionic conductivity decreases with increasing the nanopore radius, ...
Membranes and Membrane Technologies, 2020
An interesting area of modern membrane science is the development of "smart" membranes, which can... more An interesting area of modern membrane science is the development of "smart" membranes, which can affect the transport properties of selected components via external tuning. When the target components are ions, such a tuning can be realized with the help of electric field created by the conductive pore surface. We have proposed in this work a mathematical model of ions transport in a cylindrical nanopore with the electronic charge at the conductive surface and the chemical charge, which is separated from the surface by the Stern layer. The model is based on one-dimensional equations for potential, ion concentrations, and pressure in the diffuse layer. It is applied for describing the membrane potential at zero current, which characterizes the type and strength of ionic selectivity. It is shown that the change of surface potential in the direction from negative to positive results in the continuous change of pore selectivity from cation to anion. The decrease in the Stern layer capacitance and increase in the pore radius lead to the decrease in ionic selectivity. The presence of positive (negative) chemical charge causes the shift of potential value, at which the selectivity is switched, in the direction of negative (positive) values. At this value of potential, the membrane becomes non-selective, the diffusive flux of ions reaches maximum, and the osmotic flow ceases. The suggested model provides a qualitative and quantitative description of experimental results on switchable selectivity of tracketched membranes modified by the gold coating.
Doklady Chemistry, 2019
A composite of alumina nanofibers (ANF) and modified detonation nanodiamonds (MDND) was produced ... more A composite of alumina nanofibers (ANF) and modified detonation nanodiamonds (MDND) was produced by mixing aqueous suspensions of the components in a weight ratio of 5 : 1 with subsequent incubation of the mixture for 15 min at 32°C. It was assumed that the formation of the composite is ensured by the difference of the zeta potentials of the components, which is negative for MDND and positive for ANF. Vacuum filtration of the mixture through a fluoroplastic filter (pore diameter 0.6 μm) formed disks 40 mm in diameter, which were then heat-treated at 300°C to impart structural stability to the composite. Scanning electron microscopy detected that the obtained composite has a network structure, in which MDND particles are distributed over the surface of ANF. It was determined that the MDND particles incorporated in the composite catalyze the phenol-4-aminoantipyrine-H 2 O 2 oxidative azo coupling reaction to form a colored product (quinoneimine). The applicability of the composite to repeated phenol detection in aqueous samples was demonstrated.
Journal of Siberian Federal University. Mathematics & Physics, 2019
The impact of potential applied to the conductive surface of nanoporous membrane on the membrane ... more The impact of potential applied to the conductive surface of nanoporous membrane on the membrane potential at zero current is investigated theoretically on the basis of two–dimensional Space–charge model. The membrane separates two reservoirs with different salt concentrations. It is shown that the variation of applied potential from negative to positive values results in the continuous change of membrane selectivity from cation to anion. For equal ion diffusion coefficients, the dependence of membrane potential on the applied potential is an odd function, while for different ion diffusion coefficients it is shifted along the applied potential axis due to contribution of diffusion potential enhanced by the induced charge effect. The decrease of pore radius results in the increase of ionic selectivity and steep transition between cation– selective and anion–selective states when the applied potential is changing
Journal of Siberian Federal University. Mathematics & Physics, 2017
The pressure-driven electrolyte transport through nanofiltration membrane pores with specified wa... more The pressure-driven electrolyte transport through nanofiltration membrane pores with specified wall potential is investigated theoretically. The finite ion size effect is taken into account by introducing an additional term to electrochemical potential. The two-dimensional Navier-Stokes, Poisson, and modified Nernst-Planck equations are solved numerically in a high aspect ratio nanopore connecting two reservoirs with a larger diameter. The calculations are performed for potassium chloride aqueous solution. In the case of point-like ions, the non-physical rise of counter-ion concentration is observed near the pore wall at large applied voltages. When finite ion size is taken in account, the concentration of counter-ions decreases significantly and saturates to the maximum value. It leads to lower osmotic pressure jump and larger magnitude of potential in the pore. The stronger co-ion depletion observed for finite size ions results in the increase of salt rejection, membrane potential, and required pressure drop. Taking into account the steric effect allows to calculate the characteristics of nanofiltration process in much wider range of applied voltages.
The thermocapillary flows and their stability in an infinite liquid column surrounded by a co-axi... more The thermocapillary flows and their stability in an infinite liquid column surrounded by a co-axial gas layer with a given flow rate are investigated. The gas layer is surrounded by a rigid cylindrical surface, which can move in vertical direction. A constant axial temperature gradient is maintained in the layers. The exact solution describing the stationary flow in the given two-phase system is derived. Possible flow regimes are investigated and linear stability analysis of these regimes is performed. The cases of non-deformable and deformable interface are studied.
The pressure–driven electrolyte transport through nanofiltration membrane pores with specified wa... more The pressure–driven electrolyte transport through nanofiltration membrane pores with specified wall po- tential is investigated theoretically. The finite ion size effect is taken into account by introducing an additional term to electrochemical potential. The two–dimensional Navier–Stokes, Poisson, and modified Nernst–Planck equations are solved numerically in a high aspect ratio nanopore connecting two reservoirs with a larger diameter. The calculations are performed for potassium chloride aqueous solution. In the case of point–like ions, the non–physical rise of counter–ion concentration is observed near the pore wall at large applied voltages. When finite ion size is taken in account, the concentration of counter–ions decreases significantly and saturates to the maximum value. It leads to lower osmotic pressure jump and larger magnitude of potential in the pore. The stronger co–ion depletion observed for finite size ions results in the increase of salt rejection, membrane potenti...
The diffusion of binary aqueous electrolytes through nanopores with dielectric as well as conduct... more The diffusion of binary aqueous electrolytes through nanopores with dielectric as well as conductive surface is investigated theoretically on the basis of Space–Charge model. The latter is extended to the case of polarizable nanopore wall. It is shown that the diffusion of ions with different mobilities generates the electric field, which induces non–uniform surface charge in a polarizable nanopore. It results in charge separation inside the pore and leads to a dramatic enhancement of membrane potential in comparison with a non–polarizable nanopore. The calculations are performed for three aqueous electrolytes based on KCl, NaCl, and LiOH. The influence of electrolyte type and concentration difference applied across the pore on the ion transport and membrane potential is discussed and analyzed.Проведено теоретическое исследование диффузии бинарных электролитов через нанопоры с диэлектрической, а также проводящей поверхностью на основе модели пространственного заряда. Данная модель о...
Journal of Siberian Federal University. Mathematics and Physics, 2021
The ionic conductivity of nanopores with electrically conductive surface is investigated theoreti... more The ionic conductivity of nanopores with electrically conductive surface is investigated theoretically. The generalization of two-dimensional (2D) Space–charge model to calculating the ion transport under the applied potential gradient in a nanopore with constant surface potential is proposed for the first time. The results are compared with one-dimensional (1D) Uniform potential model, which is derived from the Space–charge model by assuming the independence of potential, ion concentrations, and pressure on the radial coordinate. We have found that the increase of surface potential magnitude leads to the enhancement of conductivity due to the increase of counter–ion concentration inside the nanopore. It is shown that the 1D and 2D models provide close results when the pore radius is smaller than the Debye length. Otherwise, the 1D model essentially overestimates the ionic conductivity. According to the 2D model, the ionic conductivity decreases with increasing the nanopore radius, ...
Membranes and Membrane Technologies, 2020
An interesting area of modern membrane science is the development of "smart" membranes, which can... more An interesting area of modern membrane science is the development of "smart" membranes, which can affect the transport properties of selected components via external tuning. When the target components are ions, such a tuning can be realized with the help of electric field created by the conductive pore surface. We have proposed in this work a mathematical model of ions transport in a cylindrical nanopore with the electronic charge at the conductive surface and the chemical charge, which is separated from the surface by the Stern layer. The model is based on one-dimensional equations for potential, ion concentrations, and pressure in the diffuse layer. It is applied for describing the membrane potential at zero current, which characterizes the type and strength of ionic selectivity. It is shown that the change of surface potential in the direction from negative to positive results in the continuous change of pore selectivity from cation to anion. The decrease in the Stern layer capacitance and increase in the pore radius lead to the decrease in ionic selectivity. The presence of positive (negative) chemical charge causes the shift of potential value, at which the selectivity is switched, in the direction of negative (positive) values. At this value of potential, the membrane becomes non-selective, the diffusive flux of ions reaches maximum, and the osmotic flow ceases. The suggested model provides a qualitative and quantitative description of experimental results on switchable selectivity of tracketched membranes modified by the gold coating.
Doklady Chemistry, 2019
A composite of alumina nanofibers (ANF) and modified detonation nanodiamonds (MDND) was produced ... more A composite of alumina nanofibers (ANF) and modified detonation nanodiamonds (MDND) was produced by mixing aqueous suspensions of the components in a weight ratio of 5 : 1 with subsequent incubation of the mixture for 15 min at 32°C. It was assumed that the formation of the composite is ensured by the difference of the zeta potentials of the components, which is negative for MDND and positive for ANF. Vacuum filtration of the mixture through a fluoroplastic filter (pore diameter 0.6 μm) formed disks 40 mm in diameter, which were then heat-treated at 300°C to impart structural stability to the composite. Scanning electron microscopy detected that the obtained composite has a network structure, in which MDND particles are distributed over the surface of ANF. It was determined that the MDND particles incorporated in the composite catalyze the phenol-4-aminoantipyrine-H 2 O 2 oxidative azo coupling reaction to form a colored product (quinoneimine). The applicability of the composite to repeated phenol detection in aqueous samples was demonstrated.
Journal of Siberian Federal University. Mathematics & Physics, 2019
The impact of potential applied to the conductive surface of nanoporous membrane on the membrane ... more The impact of potential applied to the conductive surface of nanoporous membrane on the membrane potential at zero current is investigated theoretically on the basis of two–dimensional Space–charge model. The membrane separates two reservoirs with different salt concentrations. It is shown that the variation of applied potential from negative to positive values results in the continuous change of membrane selectivity from cation to anion. For equal ion diffusion coefficients, the dependence of membrane potential on the applied potential is an odd function, while for different ion diffusion coefficients it is shifted along the applied potential axis due to contribution of diffusion potential enhanced by the induced charge effect. The decrease of pore radius results in the increase of ionic selectivity and steep transition between cation– selective and anion–selective states when the applied potential is changing
Journal of Siberian Federal University. Mathematics & Physics, 2017
The pressure-driven electrolyte transport through nanofiltration membrane pores with specified wa... more The pressure-driven electrolyte transport through nanofiltration membrane pores with specified wall potential is investigated theoretically. The finite ion size effect is taken into account by introducing an additional term to electrochemical potential. The two-dimensional Navier-Stokes, Poisson, and modified Nernst-Planck equations are solved numerically in a high aspect ratio nanopore connecting two reservoirs with a larger diameter. The calculations are performed for potassium chloride aqueous solution. In the case of point-like ions, the non-physical rise of counter-ion concentration is observed near the pore wall at large applied voltages. When finite ion size is taken in account, the concentration of counter-ions decreases significantly and saturates to the maximum value. It leads to lower osmotic pressure jump and larger magnitude of potential in the pore. The stronger co-ion depletion observed for finite size ions results in the increase of salt rejection, membrane potential, and required pressure drop. Taking into account the steric effect allows to calculate the characteristics of nanofiltration process in much wider range of applied voltages.
The thermocapillary flows and their stability in an infinite liquid column surrounded by a co-axi... more The thermocapillary flows and their stability in an infinite liquid column surrounded by a co-axial gas layer with a given flow rate are investigated. The gas layer is surrounded by a rigid cylindrical surface, which can move in vertical direction. A constant axial temperature gradient is maintained in the layers. The exact solution describing the stationary flow in the given two-phase system is derived. Possible flow regimes are investigated and linear stability analysis of these regimes is performed. The cases of non-deformable and deformable interface are studied.