M. V. Ryazantseva

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.

X-Ray photoelectron spectroscopy-based analysis of change in the composition and chemical state of atoms on chalcopyrite and sphalerite surface before and after the nanosecond electromagnetic pulse treatment

Using X-ray photoelectron spectroscopy, the authors analyze the change in the surface layer composition and chemical state of atoms of chalcopyrite and sphalerite as a result of treatment by high-power nanosecond electromagnetic pulses. General regular patterns and distinctions of modification of the mineral surface and floatability under high-power pulse treatment are found. The research findings are supported by the results of experimental improvement gained in selective separation of sulfides after the high-power nanosecond electromagnetic treatment.

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.

Structural and phase transformations of sulfide mineral surfaces irradiated by nanosecond electromagnetic pulses

The effect of high-voltage nanosecond electromagnetic pulses on the phase composition of chalcopyrite and sphalerite surfaces is investigated by IR-Fourier spectroscopy, XPS, and UVS. Electromagnetic pulse treatment results in the formation and accumulation of copper and/or iron sulphates Mex(SO4)y in superficial chalcopyrite layers, zinc sulphate ZnSO3, and carbonate ZnCO3 on sphalerite surfaces, changing their electrochemical and physicochemical properties; i.e., a rise in electrode potentials creates favorable conditions for anionic collector sorption and promotes sulfide flotation activity.

Theory and Applications of High-Power Nanosecond Pulses to Processing of Mineral Complexes

This paper reviews current research in high pulsed power technologies for processing of precious metals containing refractory ores and natural mineral aggregates. This is a branch of experimental engineering physics that critically depends on national priority research projects for its dynamic development. The aim of the manuscript is to show progress in the study of nanosecond processes involved in the disintegration and breaking-up of mineral complexes with fine disseminated precious metals. The manuscript presents results of theoretical and experimental studies of the mechanisms of the nonthermal action of high-power electromagnetic pulses with nanosecond leading edge, pulse duration, and high electric field strength on natural mineral media. Experimental data are presented to confirm the formation of breakdown channels and selective disintegration of mineral complexes as a result of pulse irradiation. This makes for efficient access of lixiviant solutions to precious metal particles and enhances precious metal recovery into lixivia during leaching. The paper shows the advantages of high-energy pulse treatment that provides a stable gain in valuable components recovery (5–80% gain for gold and 20–50% for silver) and at the same time helps to reduce energy consumption and cost of products in the processing of resistant gold-containing ores and beneficiation products from Russian deposits. X-ray photoelectron spectroscopy was used for determining the relationship between electromagnetic pulses energy and the surface chemical composition for pyrite and arsenopyrite. It has been concluded that impulsive treatment influences oxidation and hydrophobicity of the minerals and, therefore, it allows for the control of the hydrophobic–hydrophilic mineral surface balance.

Modifying acid–base surface properties of calcite, fluorite and scheelite under electromagnetic pulse treatment

With acid–base indicators, the change in the functional composition of surface of calcite, fluorite and scheelite under the action of high-voltage nanosecond pulses has been analyzed. After impulse treatment of mineral samples for ttreat ≤ 50 s, the concentration of electron–donor Lewis (рКа =–4.4) and proton-donor (рКа = 1.3, рКа = 4.1) Brønsted centers has grown on the surface of calcite. It is shown in the article that basic transformations of fluorite and scheelite surface under pulse treatment are connected with mutual transformations of Lewis bases and Brønsted acids.

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.

Influence of nanosecond electromagnetic pulses on phase surface composition, electrochemical, sorption and flotation properties of chalcopyrite and sphalerite

The mechanism for the powerful nanosecond electromagnetic pulse (MNEMP) effect on the phase composition of new-formed chalcopyrite and sphalerite structures is studied by IR Fourier spectroscopy method. The authors establish the effect of the higher sorption activity of sulfide minerals subjected to the electromagnetic pulse treatment. The research data are confirmed by the experimental data on MNEMP effect on electrochemical and flotation properties of chalcopyrite and sphalerite.

Nanosecond electromagnetic pulse effect on phase composition of pyrite and arsenopyrite surfaces, their sorption and flotation properties

The X-ray photoelectronic spectroscopy data give the grounds for statement that the powerful nanosecond electromagnetic pulse pretreatment improves sorption activity of pyrite surface and lowers sorption of a collector at arsenopyrite surface. The research results are verified by test data on the powerful nanosecond electromagnetic pulse effect on the structure and chemical properties of pyrite and arsenopyrite surface, as well as their electrochemical and flotation properties.