D. V. Makarov

Oxidation Sequence of Sulfide Minerals in Operating and Out-of-Service Mine Waste Storage

To determine the oxidation sequence for sulfides in stored mine waste and to assess the effect of sulfide oxidation on the environment and the processing characteristics of anthropogenic deposits, the electrode potentials of sulfide minerals were measured in alkali solutions under conditions similar to storage conditions. The surface oxidation of sulfides was studied in relation to the nature and concentration of the dissolved gas. The influence of sulfide surface inhomogeneities and mineral concretion on the electrochemical oxidation was investigated. The oxidation rate of minerals was found to be increased by impurities with higher electropositive potentials.

Interaction of Micas with Nickel Sulfate Solutions

The interaction of natural biotites with dilute nickel sulfate solutions at various pHs are studied by X-ray powder diffraction, thermogravimetric analysis, and chemical analysis. K ⇆ Ni, Mg ⇆ Ni, and to a lesser extent Fe ⇆ Ni ion exchange is shown to occur. Nickel can both enter octahedral layers and act as an interlayer cation. Tetrahedral layers have a virtually invariable composition. The mechanoactivation of biotites enhances exchange reactions.

Reaction of niobium pentoxide with ammonium hydrodifluoride

The reaction between Nb2O5 and NH4HF2 is studied by thermogravimetric analysis, IR spectroscopy, and crystal-optical analysis. Intermediates and their formation temperatures are determined.

Hydrofluoride Synthesis of Fluorides of Some Rare-Earth Elements

Thermal gravimetric, X-ray phase, IR spectroscopic, and chemical analyses were applied to study the reaction of yttrium and neodymium oxides with NH4HF2.

Reaction of magnesium oxide and magnesium silicates with ammonium hydrodifluoride

The reactions of magnesium oxide and magnesium silicates (forsterite and serpentines) with ammonium hydrodifluoride is studied using DTA, X-ray powder diffraction, and IR spectroscopy. The conditions for the formation of intermediate phases are determined. The structure of the silicate mineral does not significantly affect the fluorination.