Modeling of the Effect of pH on the Calcite Dissolution Kinetics

The kinetics and mechanism of calcite dissolution at various pH are investigated. A scheme of the ion distribution in various states of the medium is presented. The kinetic curves of dissolution are modeled, taking into account the structure of the electrical double layer and the acid-base characteristics of calcite.     

Adsorption of dichromate ions on the red mud surface

The possibility of using a red mud (waste of alumina production) as a sorbent of dichromate ions from aqueous solutions is studied. A method for the activation of red mud by hydrochloric acid is proposed. The dependences of the amount adsorbed of dichromate ions on the pH and initial concentration of aqueous solutions are studied.     

Influence of oxalic acid on the dissolution kinetics of manganese oxide

The kinetics and electrochemical processes of the dissolution of manganese oxides with various oxidation states in sulfuric acid solutions containing oxalate ion additives is studied under variable conditions (concentration, pH, temperature). The parameters favoring a higher degree of the dissolution of manganese oxides in acidic media are determined. The optimal conditions are found for the dissolution of manganese oxides in acidic media in the presence of oxalate ions. The mechanism proposed for the dissolution of manganese oxides in sulfuric acid solutions containing oxalic acid is based on the results of kinetic and electrochemical studies. The steps of the dissolution mechanism are discussed.     

Study of Calcium and Iron Carbonate Dissolution Kinetics in Order to Resolve Corrosion Problems in Carbonate Solutions

Chemical and Petroleum Engineering - It is established that carbonate dissolution kinetics have diffusion and kinetic control, i.e., chemical reaction rate determines the transfer of calcium and...     

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 CuOHL^3–ion is elucidated, and the kinetic parameters of dissolution are derived.     

Calculation of thermodynamic acid-base equilibrium constants at oxide-electrolyte interfaces from experimental electrokinetic potential versus pH data

A procedure is described for determining the parameters of the electrical double layer and acid-base equilibrium constants at oxide-electrolyte interfaces from the pH dependence of the electrokinetic potential when there is no specific adsorption of ions. The procedure is used to calculate the parameters of the electrical double layer and acid-base equilibrium constants for 20 oxides. At a given background electrolyte concentration, the dependence of the calculated parameters on the difference pH - pH₀ is insensitive to the nature of the oxide.     

Dissolution of Manganese Oxides of Various Compositions in Sulfuric Acid Solutions Studied by Kinetic Methods

The dissolution of manganese oxides in sulfuric acid solutions of various concentrations has been studied by kinetic methods. We have investigated the dissolution of manganese oxides of various compositions in sulfuric acid solutions of various concentrations. The composition of the manganese oxides and the sulfuric acid concentration have been shown to influence the dissolution rate. We have calculated kinetic parameters of the dissolution of manganese oxides in sulfuric acid solutions (dissolution rate, activation energy for dissolution, and reaction orders) and proposed a model for the dissolution of manganese oxides in sulfuric acid solutions.     

Modeling of copper(II) oxide dissolution in sulfuric acid solutions in the presence of ammonia and complexones

The effect of ammonia and complexones on the kinetics of copper(II) oxide dissolution in aqueous solutions of sulfuric acid is studied. It is found that addition of complexones and ammonia to acidic media decreases the dissolution rate. Modeling of the dissolution kinetics shows that the inhibiting effect of complexing agents is caused by a decrease in the concentration of surface intermediate compounds, which are transferred into the solution.Translated from Teoreticheskie Osnovy Khimicheskoi Tekhnologii, Vol. 39, No. 2, 2005, pp. 220–228.Original Russian Text Copyright © 2005 by Plakhotnaya, Gorichev, Batrakov, Izotov, Kutepov.Deceased.     

Kinetics of aluminum hydride thermal decomposition

The kinetics of A1H₃ decomposition were studied as a function of temperature and hydrogen pressure. Analysis of the experimental data in the formal heterogeneous kinetic approach suggests that the rate of the process is limited by the breaking of Al-H bonds.     

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.