N. E. Anashkina

Surface activation and induced change of physicochemical and process properties of galena by nanosecond electromagnetic pulses

X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy are used to study the change of the surface layers and chemical state of atoms on galena surface after treatment by high-voltage nanosecond electromagnetic pulses. By XPS the induced structural changes of galena surface layer are associated with alteration of chemical state of sulfur atoms, which conditions the change of electrochemical and flotation properties of the semiconductor sulfide mineral: growth of electrode potential creates favorable conditions for adsorption of anion collector and promotes increased floatability of galena.

Changes in the functional chemical composition of the surfaces and microhardness of kimberlite minerals under the action of nanosecond high voltage pulses

Using a set of physicochemical methods (XPS, analytical electron microscopy, the adsorption of acid–base indicators, and measuring microhardness), the effectiveness of nonthermal action produced by nanosecond high voltage pulses for targeted changes in the phase (functional chemical) composition and technological properties of rock-forming minerals of kimberlites and diamonds is shown. According to data obtained via XPS and SEM-EDX analyses, pulse energy actions damage the surface microstructure of dielectric minerals with the subsequent formation of traces of surface breakdowns and microcracks, softening rockforming minerals, and reducing their microhardness by 40–66% overall. The following changes in the functional chemical composition of a geomaterial surface are established through the adsorption of acid–base indicators: mutual transformations of the Brønsted base, Lewis base, and Brønsted acid sites on a calcite surface under the action of an electromagnetic pulse and the hydroxylation and/or formation of carbonyl groups on a diamond surface, doubling the diamond electrokinetic potential in the negative range.

Experimental validation of mechanism for pulsed energy effect on structure, chemical properties and microhardness of rock-forming minerals of kimberlites

Using the Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), microscopy and microhardness test methods, the change in the crystalline and chemical properties and in microhardness of rock-forming minerals of kimberlites as a result of exposure to high-power nanosecond electromagnetic pulses (HPEM) has been studied. From FTIR and XPS data the non-thermal effect of HPEM results in damage of surface microstructure of dielectric minerals due to formation of microcracks, surface breakdowns and other defects, which ensure effective weakening of rock-forming minerals and reduction in their microhardness by 40–66%.

Effect of acid and electrochemical treatment on physicochemical and electrical properties of tantalite, columbite, zircon and feldspar

The article gives a report on integrated experimental research into targeted change of chemical and phase composition of surface and increase in contrast of physicochemical, electrical and electrochemical properties of tantalite, columbite and zircon under treatment by acid product of water electrolysis—anolyte (pH < 5) and by muriatic solution (HCl, pH 3–3.5). The X-ray photoelectron spectroscopy, high resolution spectroscopy and chemical and electrophysical techniques reveal the mechanism of structural–chemical surface transformation of tantalite, columbite, zircon and feldspar under leaching in acid solutions; this surface transformation mechanism consists in activation of dissolving of iron- and silicate-containing surface films and high-rate oxidation of iron atoms in surface layer of tantalite and columbite, with transition of Fe(II) to Fe(III) and surface destruction of zircon, with formation of oxygenvacant defects of SiO32− and SiO20 type under influence of anolyte.

Changes in the functional chemical compositions of surface and structural defects of diamonds, due to the nonthermal influence of nanosecond high voltage pulses

Fourier transform infrared spectroscopy (FTIR), analytical electron and atomic force microscopy, and physicochemical examination of the structure and properties of mineral surfaces are used to study changes in the structural defects, functional and chemical compositions, and surface electrical properties and hydrophobicity of diamond surfaces exposed to nonthermal nanosecond high-voltage pulse treatment. The degradation of secondary mineral phase films, their peeling from the diamond surfaces, the growth of crystal hydrophobicity, and an increase in the number of B2 defects were observed after 50 s of treatment with electric pulses. Lengthening the period of irradiation (the dose) to 150 s resulted in oxidation of the diamond surfaces by products of water–air medium radiolytic decomposition, which led to the production of hydroxyl and/or carbonyl groups on the crystal surfaces, a further shift of the diamond electrokinetic and electrostatic potential into the region of negative values, and deterioration of the diamond’s hydrophobic properties.

Oxidation of a galenite surface under the impact of nanosecond pulses

The effect of high-voltage nanosecond pulses on the phase composition of a galenite surface is investigated by means of XPES and IR Fourier spectroscopy. According to the XPES data, structural-phase transformations caused by pulsed treatment are mainly associated with variations in the chemical state of sulfur atoms, which determines the electrochemical and flotation properties of a semiconductor sulfide mineral: an increase in the electrode potential creates favorable conditions for adsorption of anion collectors and raises the flotation activity of galenite.

Modification of Structural, Chemical and Process Properties of Rare Metal Minerals under Treatment by High-Voltage Nanosecond Pulses

The authors have studied the mechanism of controlled modification of composition, structure, chemistry, physicochemical and process properties of columbite, tantalite, zircon and feldspar at the meso-, micro- and nanoscales after nonthermal treatment by high-voltage nanosecond electromagnetic pulses. The studies used methods: X-ray photoelectron spectroscopy, scanning electron and atomic force microscopy, potentiometric titration, electromigration chromatography, Kelvin probe force microscopy, microhardness metering and assessment of hydrophobic behavior and flotation activity of the minerals. It is found that changes in the chemical state of atoms on the surface of minerals are mainly connected with the sequential transformation of stages in the process of formation and modification of a functional cover of mineral surface, with variation in a ratio of different type hydroxyl groups on the surface of columbite, zircon and feldspar, which conditions contrast physicochemical properties of rare metal minerals and improves selectivity of their separation by flotation.

Effect of High-Voltage Nanosecond Pulses on the Physicochemical and Technological Properties of Rare-Metal Minerals

The mechanism of the structural and chemical state modification of columbite, tantalite and zircon surface under the effect of high-voltage nanosecond pulses is investigated using a set of precision physical and chemical methods (e.g., XPS, FTIR, SEM–EDX, potentiometric titration, electrophoretic light scattering, AFM–Kelvin force probe microscopy, and microhardness). An effective mode of preliminarily treating rare-metal minerals with high-voltage nanosecond pulses to produce directional changes in their physicochemical, electrical, mechanical, and technical properties is validated that increases mineral flotation and sorption activity and greatly improves the flotation technological characteristics of columbite and zircon.

Mechanism of the Effect of High-Voltage Nanosecond Pulses on the Structural, Chemical, and Technological Properties of Natural Dielectric Minerals

The mechanism behind the modification of the surface chemical structure and technological and physicochemical properties of Ca-bearing minerals (calcite, scheelite, and fluorite) under the effects of highvoltage nanosecond pulses is investigated by means of XPS, FTIR, X-ray luminescence spectroscopy, electrophoretic light scattering (ζ-potential), atomic-force microscopy (Kelvin probe force microscopy), microhardness measurements, and an approach based on the adsorption of acid–base indicators with different intrinsic pKα parameters. The acceptor properties of calcite and scheelite surfaces grow and the electron donor ability of fluorite increases as a result of pulsed electric field processing (ttreat ~ 30 s, Nimp ~ 3 × 103). The impact of energy pulses results in the formation of structural defects, surface softening (a 50–67% reduction in microhardness), and a directional change in mineral electric properties. Preliminary electropulse treatment generally enhances mineral flotation activity by 5–12%.

Non-thermal Effect of High-Voltage Nanosecond Pulses on Kimberlite Rock-Forming Minerals Processing

In the present paper, we attempted to substantiate the efficiency of non-thermal high-power (high-voltage) nanosecond electromagnetic pulses for the directional change of phase (chemical and functional) composition and technological properties of kimberlite rock-forming minerals (olivine, calcite and serpentine) investigated using a complex of physical and chemical methods (XPS, DRIFTS, analytical electron microscopy, atomic-force microscopy, microhardness measurement—Vickers indentation method, and the method of acid-base indicators adsorption). According to XPS, DRIFTS, SEM-EDX and microhardness testing data, the effect of high-voltage nanosecond pulses leads to damage the surface microstructure of dielectric minerals with the subsequent formation of traces of surface breakdowns and microcracks, softening of rock-forming minerals, and reducing their microhardness by 40–66% overall.