A. D. Izotov

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.

Effect of the anionic composition and pH on the dissolution kinetics of chromium(III) oxide and chromium(III) hydroxide oxide in acids

Based on an experimental investigation of the effects of the pH and anionic composition on the dissolution rate of chromium(III) oxide α-Cr2O3 and chromium(III) hydroxide oxide α-CrOOH and subsequent modeling of the process, it is demonstrated that, depending on the pH, the rate-controlling stage of the dissolution is the CrOH2+ or CrHSO42+ sobulization.

Simulation of the effect of hydroxyethylidenediphosphonic acid on the kinetics of copper(II) oxide dissolution in sulfuric acid

The effect of hydroxyethylidenediphosphonic acid (HEDP) on the kinetics of copper(II) oxide dissolution in aqueous sulfuric acid was studied. The addition of HEDP in acidic media decreases the CuO dissolution rate. The simulation of these processes showed that the inhibiting effect is due to the decrease in the concentration of the intermediate compound (CuOH+), which restricts the dissolution of Cu2+ ions, due to adsorption of the HEDP ions (H4Y−) on the oxide surface.

α- al(OH)3, dissolution in acid media

The dissolution rate of aluminum hydroxide in sulfuric and hydrochloric acids was studied as a function of acid concentration, solution temperature, and the hydroxide/electrolyte interfacial potential. It was found to be limited by the transfer of surface complexes from the solid phase to the solution.

Interaction between lanthanide cuprates and hydrochloric acid

The interaction between lanthanide cuprates Ln2CuO4 − δ (Ln = La-Gd) and hydrochloric acid is investigated. The effects of solution pH, temperature, and the nature of the rare-earth element ion on dissolution is studied. The formal order of the reaction in the acid is the same for all the substances under study and is 0.53 ± 0.05. The effective activation energy for the process is 40 ± 0.5 kJ/mol. A scheme of Ln2CuO4 − δ interaction with HCl is proposed.

Investigation of the mechanism and kinetics of dissolution of nickel(II) and nickel(III) oxides in sulfuric acid

Based on the experimental data on the effect of pH and the H2SO4 concentration on the dissolution rate of nickel oxides, the nature of the limiting stage is revealed, which consists in the formation of surface compounds and their subsequent transfer into the electrolyte solution. The intermediate products of dissolution of nickel(II) oxide in sulfuric acid are identified.