Influence of Electroconvection on Chronopotentiograms of an Anion-Exchange Membrane in Solutions of Weak Polybasic Acid Salts

Visualization of electroconvective (EC) vortices at the undulated surface of an AMX anion-exchange membrane (Astom, Osaka, Japan) was carried out in parallel with the measurement of chronopotentiograms. Weak polybasic acid salts, including 0.02 M solutions of tartaric (NaHT), phosphoric (NaH2PO4), and citric (NaH2Cit) acids salts, and NaCl were investigated. It was shown that, for a given current density normalized to the theoretical limiting current calculated by the Leveque equation (i/ilimtheor), EC vortex zone thickness, dEC, decreases in the order NaCl > NaHT > NaH2PO4 > NaH2Cit. This order is inverse to the increase in the intensity of proton generation in the membrane systems under study. The higher the intensity of proton generation, the lower the electroconvection. This is due to the fact that protons released into the depleted solution reduce the space charge density, which is the driver of EC. In all studied systems, a region in chronopotentiograms between the rapid growth of the potential drop and the attainment of its stationary values corresponds to the appearance of EC vortex clusters. The amplitude of the potential drop oscillations in the chronopotentiograms is proportional to the size of the observed vortex clusters.

Electrodynamic approach for description of mass transfer phenomena

Based on the equations of macroscopic electrodynamics, the article considers the most important consequences from the point of view of practical application for condensed matter. It has been theoretically shown that a virtual molecular filter with a fairly high degree of selectivity can be used for them. The theoretical substantiation of mass transfer processes in condensed systems is presented for cases of external influence on them when solving problems of technological change of macroscopic properties of a molecular system. Monitoring problems are indicated when moving the minimum amount of substance in the case of mass transfer for processes: diffusion, adsorption, capillary filtration. The functioning of the filter is based on the theory of macroscopic electrodynamics, namely, on how the space charge density is distributed in the sample under study. The results obtained make it possible to evaluate the physicochemical changes that occur in a condensed medium under external technological influence. The presented theoretical research results can serve as the basis for improving the methods of electrometric monitoring of gaseous and liquid media of unknown qualitative and quantitative composition.

Concept Design of a High-Voltage Electrostatic Sanitizer to Prevent Spread of COVID-19 Coronavirus

In addition to public health measures, including social distancing, masking, cleaning, surface disinfection, etc., ventilation and air filtration can be a key component of a multi-pronged risk mitigation strategy against COVID-19 transmission indoors. Electrostatic precipitators (ESP) have already proved their high performance in fluid filtration, particularly in industrial applications, to control exhaust gas emissions and remove fine and superfine particles from the flowing gas, using high-voltage electrostatic fields and forces. In this contribution, a high-voltage electrostatic sanitizer (ESS), based on the electrostatic precipitation concept, is proposed as a supportive measure to reduce indoor air infection and prevent the spread of COVID-19 coronavirus. The finite element method (FEM) is used to model and simulate the proposed ESS, taking into account three main mechanisms involving in electrostatic sanitization, namely electrostatic field, airflow, and aerosol charging and tracing, which are mutually coupled to each other and occur simultaneously during the sanitization process. To consider the capability of the designed ESS in capturing superfine particles, functional parameters of the developed ESS, such as air velocity, electric potential, and space charge density, inside the ESS are investigated using the developed FEM model. Simulation results demonstrate the ability of the designed ESS in capturing aerosols containing coronavirus, precipitating suspended viral particles, and trapping them in oppositely charged electrode plates.

The model of potential barrier appearing in a hydrolayer localized in a two-layer porous nanostructure

A model has been proposed to describe the potential barrier that appears during interaction of two compacted layers consisting of hydrophilic oxide nanoparticles of different sizes in each layer upon saturation of this structure with adsorbed water. The dependence of the space charge density of the compacted powder material on the density of particles in it has been theoretically calculated. The distribution of the potential over the thickness of contact between two layers consisting of nanoparticles with different sizes has been obtained.

Finite Element Based Comparative Analysis of Positive Streamers in Multi Dispersed Nanoparticle Based Transformer Oil

The dispersion of dissimilar nanoparticles (NPs) in transformer oil (TO) has a major impact on fast propagating positive streamers. This work investigates the positive streamer dynamics in TO modified by dispersing both Fe3O4 and Al2O3 NPs at a homogenous concentration. The hydrodynamic drift diffusion model of positive streamer evolution and propagation are solved using the commercial software package COMSOL Multiphysics. The impact of multiple NPs (MNPs) has been analysed for streamer propagation, electric field intensity, electron density, and space charge density of modified TO. MNPs successfully reduce streamer propagation velocity by 50%, 17%, and 37.5% comparing to pure oil, Fe3O4 based nanodielectric fluids (NDFs), and Al2O3 based NDFs, respectively. The spatial distribution of electron density reveals the loss of electrons from the ionization region until the saturation of NPs. A comparative study demonstrates that MNPs significantly alter the streamer dynamics and augment the dielectric strength of TO compared to individual NPs.

On the unusual properties dielectric constant of the electric field of the free atmosphere

On the basis of experimental data vertical distribution electric field strength of the atmosphere, the applied problem of fitting constants in the model of the average self-consistent electric field is solved.The model is based on the nonlinear Poisson equation. Such an approach is not trivial because generally known in meteorology interpolation exponential function describing the empirical distribution of the electric field, space charge density and conductivity with a height not quite correctly reproduce a stable stratification of the electric field. Since aircraft measurements are carried out in a natural environment, the dielectric constant is lost, which leads to underestimated values of the electron-ion concentration.This is due to the fact that the potential in situ is screened and the Gauss theorem does not hold for it, and if it does, then for the radius of the Gaussian sphere it is less than the Debye screening radius. For a large Gaussian sphere, only the near-wall part of the electrometer is experimentally determined, and the shielded (inner) part does not contribute to the field flux through the surface by the dynamic screening of the electron. The magnitude of the screening of electrons in air is very large due to the dynamic polarizability of the medium and consists of two parts — the Debye and ion-plasma screening spheres. This, in turn, requires a redefinition of the dielectric constant for correct reproduction of field measurements. Thus, the verification of the dielectric constant was carried out on different experimental data, and its values lie within the same limits as the values obtained from the classical relations of Penn, Debye, and Landau.

Some features of the analysis of water, soil and ground in mass spectrometers with inductively coupled plasma (ICP-MS)

The paper discusses the possibilities and limitations of the method of mass spectrometry with inductively coupled plasma on the example of elemental analysis of natural and drinking waters, soils and grounds. It is shown that the combination of this method with the simpler atomic emission method makes it possible to expand the range of determined elements, simplify the mass-spectral analysis and increase its reliability. It is shown that the use of the ICP-MS method in the analysis of various objects makes it possible to determine the majority of elements with extremely low detection limits. The reason for the manifestation of matrix effects is the positive space charge formed between the interface and the extractor, the composition of which is determined by the composition of singly charged argon ions. The increase in the concentration of ions in this region is the appearance of a matrix element, which facilitates the scattering of ions from this region. It was found that the heavier the ions of the matrix element, the more the space charge density increases and the scattering occurs. A serious limitation of the method is associated with interferences due to the presence of a certain amount of two and three-charged ions in the plasma. These ions, which have approximately the same mass as the isotopes of the element being determined, are formed as a result of various plasma-chemical reactions and interfere with the determination.

Improved Rectification and Osmotic Power in Polyelectrolyte-Filled Mesopores

Ample studies have shown the use of nanofluidics in the ionic diode and osmotic power generation, but similar ionic devices performed with large-sized mesopores are still poorly understood. In this study, we model and realize the mesoscale ionic diode and osmotic power generator, composed of an asymmetric cone-shaped mesopore with its narrow opening filled with a polyelectrolyte (PE) layer with high space charges. We show that, only when the space charge density of a PE layer is sufficiently large (>1×106 C/m3), the considered mesopore system is able to create an asymmetric ionic distributions in the pore and then rectify ionic current. As a result, the output osmotic power performance can be improved when the filled PE carries sufficiently high space charges. For example, the considered PE-filled mesopore system can show an amplification of the osmotic power of up to 35.1-fold, compared to the bare solid-state mesopore. The findings provide necessary information for the development of large-sized ionic diode and osmotic power harvesting device.

Reconstructing the electrical structure of dust storms from locally observed electric field data

While the electrification of dust storms is known to substantially affect the lifting and transport of dust particles, the electrical structure of dust storms and its underlying charge separation mechanisms are largely unclear. Here we present an inversion method, which is based on the Tikhonov regularization for inverting the electric field data collected in a near-ground observation array, to reconstruct the space-charge density and electric field in dust storms. After verifying the stability, robustness, and accuracy of the inversion procedure, we find that the reconstructed space-charge density exhibits a universal three-dimensional mosaic pattern of oppositely charged regions, probably due to the charge separation by turbulence. Furthermore, there are significant linear relationships between the reconstructed space-charge densities and measured PM10 dust concentrations at each measurement point, suggesting a multi-point large-scale charge equilibrium phenomenon in dust storms. These findings refine our understanding of charge separation mechanisms and particle transport in dust storms.