A. M. Kutepov

Interfacial Mass Transfer in the Liquid–Gas System: An Optical Study

Mass transfer across the liquid–gas interface was studied by a number of optical methods: holographic interferometry in real time, polarization microscopy, shadow imaging, and modified surface-fluctuation spectroscopy. These methods visualize the evolution of the surface layer, the in-depth profile of density, and mass fluxes. Absorption and desorption of various gases by perfluorodecalin is discussed. The origination and development of irregularities in the diffusion–reaction zone were observed during chemical absorption of carbon dioxide by monoethanolamine and KOH solutions.

Dissolution Kinetics of Manganese(III, IV) Oxides in Sulfuric Acid in the Presence of Ethylenediaminetetraacetic Acid

Dissolution kinetics of manganese(III, IV) oxides in sulfuric acid in the presence of ethylenediaminetetraacetic acid was studied at various pH values and temperatures. Kinetic, spectrophotometric, and electrochemical studies demonstrated that the dissolution rate of manganese oxides is governed by the potential step at the oxide/electrolyte interface and by the solution pH. A mechanism of the dissolution is suggested.

Dissolution Kinetics of Nickel(II) and Nickel(III) Oxides in Acid Media

The rate of nickel(II) and nickel(III) oxide dissolution in sulfuric, hydrochloric, and nitric acids was measured as a function of the acid concentration and temperature, and a kinetic model of this process is suggested. The limiting step of the dissolution process is the passage of the complexes forming on the oxide surface into the solution.

Analysis of Fe2O3 and Fe3O4 Dissolution Kinetics in Terms of the Chain Mechanism Model

Kinetic data on Fe2O3 and Fe3O4 dissolution in solutions of hydrochloric and sulfuric acids of different concentrations are analyzed in terms of the chain mechanism model at different solution temperatures under different conditions of synthesis of oxide samples. A kinetic model of dissolution of iron oxides is proposed. It is shown that features of the iron oxide dissolution kinetics are explained by the difference between the concentrations of dislocations and other defects on the surface of particles.

Interaction between Copper(II) Oxide and Aqueous Ammonia in the Presence of Ethylenediaminetetraacetic Acid

The interaction of copper(II) oxide with aqueous ammonia containing ethylenediaminetetraacetic acid (H4L) is analyzed in terms of formal heterogeneous kinetics and the fractal dimension of the dissolving space. It is shown experimentally that, in the presence of H4L, the dissolution rate of CuO grows with increasing ammonia concentration. At a fixed ammonia concentration, the dissolution rate of CuO passes through a maximum at an H4L concentration of 8 × 10–3mol/l. Two mechanisms of dissolution are suggested, namely, an adsorption and a redox mechanism. The adsorption mechanism involves four intermediate species and implies that the dissolution rate is a fractional rational function of the EDTA concentration. The redox mechanism takes into account the oxide/electrolyte interfacial potential. The role of the CuOHL3–ion is elucidated, and the kinetic parameters of dissolution are derived.

Catalytic Effect of Ammonia on the Kinetics and Mechanism of MoO3 Dissolution in Alkaline Solutions

The effect of the ammonia concentration, pH, and temperature on the kinetics and mechanism of MoO3 dissolution are analyzed based on the principles of heterogeneous kinetics. It is found that the rate of the limiting step is determined by the adsorption of the ammonium ion, which leads to the formation of an intermediate surface compound.

Crystallization Science at the Turn of the Third Millennium

Crystallization science is an experimental science grounded on a well developed theoretical and methodological basis. This area of knowledge is being advanced from a macrokinetic to a molecular kinetic description of elementary processes. Research is made along many lines, among them cluster chemistry, the physical chemistry of crystal growth, the morphology of aggregates and colloidal crystals, the dynamics of suspensions of crystals in inhomogeneous supersaturated media, and protein crystallization. Researchers in these fields are about to elucidate the role of individual molecules of the crystallizing substance in the crystallization process.

Selection of the Hydrodynamic Conditions of Galvanocoagulation on Application of Low-Frequency Pulsations to the Medium Being Treated

A study is undertaken to analyze the enhancement of galvanocoagulation in wastewater treatment to remove nonferrous and ferrous metal ions on application of low-frequency pulsations to the medium being treated. It is noted that, in most cases, galvanocoagulation is controlled by the mass transfer in the anodic dissolution of an element of a galvanic couple and by the ion transfer to the cathode, which are determined by the hydrodynamic conditions at the interface. A procedure is proposed to select the hydrodynamic conditions in the apparatus on application of low-frequency pulsations to the medium which enhance mass transfer. The procedure is tested on the example of treatment of wastewater containing Cr+3 and Cr+6 ions in a vertical pulsation galvanocoagulator of original design. It is shown that fluidization caused by the application of pulsations increases the rates of mass transfer and overall galvanocoagulation process.

Modeling of Separation in a Cocurrent Cylindrical Hydrocyclone

The radial motion of the dispersed phase in a cocurrent cylindrical hydrocyclone under the action of deterministic forces, including the inertial force, is considered. It is shown that the acceleration of particles in the direction away from the apparatus axis toward the apparatus wall can be neglected. Under this assumption, a method is proposed to calculate the characteristics of separation of the solid–liquid and solid–liquid–gas systems.

Transitional modes and crisis phenomena in hydrocyclones

Transitional modes and crisis phenomena caused by the specific features of the velocity field of swirl flows and the dispersed phase in hydrocyclones are studied. The critical situations are analyzed and the reasons for the ambiguity of operational modes and the emergence of crises are discussed.