A. T. Kovalev

On the field-emission properties of sulfide minerals under high-power nanosecond pulses

The mechanism of absorption of the energy of high-power electromagnetic nanosecond pulses due to the field emission from the surface of natural semiconductors is considered. The limitations and possibilities of implementing this mechanism in sulfide minerals (pyrite and arsenopyrite) are demonstrated.

MECHANISMS OF DISINTEGRATION OF MINERAL MEDIA EXPOSED TO HIGH-POWER ELECTROMAGNETIC PULSES

This report is devoted to the following plausible mechanisms of disintegration of mineral substances exposed to high-power electromagnetic pulses (HPEMP) with high electric field strength: loosening of mineral structure through electrical breakdown; disintegration due to development of mechanical stresses at the boundary between the dielectric and conductive mineral components; electromagnetic energy absorption by thin metallic films or layers thinner than the characteristic skin layer. Disintegration through these mechanisms would proceed efficiently only provided that the size of the mineral sample exposed to HPEMP exceeds a definite minimum value, which is due to low concentration of the irradiating energy.

Energy concentration in electric discharges between particles of semiconducting sulfide minerals under the action of high-power nanosecond pulses

A model for development of electric discharges between particles of sulfide minerals (pyrite) under the action of high-voltage nanosecond pulses is proposed. It is shown that through discharges in a layer of pyrite particles lead to energy concentration in small contact regions between particles; the concentrated energy is sufficiently high for local decomposition (disintegration) of mineral complexes.

Formation of micro- and nanophases on sulfide mineral surfaces under the effect of nanosecond electromagnetic pulses

The gas outflow from nanosecond breakdown channels of sulfide minerals under high-power electromagnetic pulses is considered with regard to iron and sulfur vapor condensation. New experimental data on the structural and chemical transformations of sulfide mineral surfaces under nanosecond pulse action are reported.

Condensation of matter during gas outflow from nanosecond breakdown channels of sulfide minerals

The gas outflow from nanosecond breakdown channels of sulfide minerals under the effect of high-power electromagnetic pulses is considered, with allowance for the condensation of iron vapors. The condensation of matter in an outflowing jet is shown to be an effective mechanism for structural-chemical transformations of sulfide surfaces.

The role of gas outflow from nanosecond breakdown channels in the electric-pulse discharge disintegration of sulfide minerals

The heated gas outflow from nanosecond breakdown channels of sulfide minerals (pyrite) under high-power electromagnetic pulses is considered. It is shown that the gas outflow from channels can be an additional destructive factor in the processes of the electric-pulse discharge disintegration of fine-disseminated mineral complexes.

Structural Modification of Sulfide Minerals Irradiated by High-Power Nanosecond Pulses

The present work studies the effect of high-power (high-voltage) nanosecond pulses on the phase composition and chemical (quantum) state of atoms of surface layers of sulfide minerals with different semiconductor properties (galenite, chalcopyrite, pyrrhotite, pentlandite, molybdenite, and sphalerite) by means XPES and DRIFTS analysis , and analytical electron microscopy (SEM/EDX). Common patterns and main characteristic features of the structural phase transformations of sulfide surfaces under the pulsed energetic effect demonstrate: (i) formation and growth of a surface layer by the nonstoichiometric sulfur-enriched sulfide phase and metal (for example, Zn and Mo) oxides and hydroxides; (ii) the staged character of the transformation of sulfur atoms in the composition of galenite, pyrrhotite, pentlandite and sphalerite surface layers and (iii) the stability of the chemical state of sulfur in the molybdenite composition and lead atoms in the galenite composition. The increase of the electrode potential of sulfide minerals under pulsed effect provides favorable conditions for the adsorption of anion collector and, as a consequence, leads to the increase of galena, chalcopyrite and sphalerite floatability.

Nanosecond electrical discharges between semiconducting sulfide mineral particles in water

A model for developing electric discharges between sulfide mineral (pyrite) particles under high-voltage nanosecond pulses in a liquid medium (water) is considered. A possibility of electrical breakdowns of liquid gaps between particles under nanosecond pulses is shown. This probability and the energy released in discharge channels depend strongly on the sulfide conductivity.

Application of High-Power Electromagnetic Pulses to Desintegration of Gold-Containing Mineral Complexes

The application of High-Power Electromagnetic Pulses (HPEMP) irradiation in dressing of resistant gold- containing ores appears attractive as this technique provides for a significant increase in precious metal recovery (30-80% for gold and 20-50% for silver), therewith helping reduce both energy consumption and the cost of products. This study deals with plausible mechanisms of disintegration of mineral particles under the action of nanosecond HPEMP with high electric field strength ii~107 V/m. Experimental data are presented to confirm the formation of breakdown channels and selective disintegration of mineral complexes as a result of pulse irradiation, which makes for efficient access of lixiviant solutions to precious metal grains and enhanced precious metal recovery into lixivia during leaching. We studied the influence of HPEMP on the technological properties of particles of refractory gold- and silver-containing ores and beneficiation products from Russian deposits. Preliminary processing of gravity concentrate of one deposit ore with a series of HPEMP resulted in significant increase of gold and silver extraction into lixivia during the cyanidation stage, with gold recovery increased by -31% (from 51.2% in a blank test to 82.3% after irradiation) and silver recovery increased by 47% (from 21.8% to 68.8%). Gold recovery from stale gold-containing dressing tailings of the two integrated mining-and-dressing works increased after pulses-irradiation from 8-12% to 80-90%.