Development of a method and apparatus for measuring the forces in particle contacts under conditions of flotation of gold microdispersions
Authors:   North Caucasian Institute of Mining and Metallurgy (State Technological University), EVDOKIMOV Sergey , MAKOEVA Alla ,   North Caucasian Institute of Mining and Metallurgy (State Technological University), MAKSIMOV Ruslan ,   North Caucasian Institute of Mining and Metallurgy (State Technological University), DYATLOVA Daria ,   North Caucasian Institute of Mining and Metallurgy (State Technological University)
Published: May 2023

Introduction. In flotation of gold-containing ores, metal losses with tailings are mainly related to the fine particle size classes - micro dispersions. Study of the physical nature of the forces in the contacts between the particles, including gold micro dispersions, allows gaining new knowledge associated with the solution of the pressing problem of effective extraction of difficult to extract forms of the precious metal by flotation. Materials and methods. Measurement of the forces in contacts of particles was carried out by sediment volumetric method using the developed device. The method allows to determine the forces in contacts of particles by the volume of their sediment, formed as a result of kinetic destruction of the disperse system. Alluvial gold from the collection formed during the experimental tests of the equipment of separation complexes "Shlich", "Shlich-2", "PGShOK-50-2" was used in the experiments. The results of measuring the forces were supplemented by theoretical studies, which had the aim to estimate the contribution of the fluid volume held by capillary forces in contacts of particles to the volume of sediment. Results. It was found that the volume formed by the kinetic destruction of the disperse system is determined by the force in the contacts of particles, and the volume of capillary held liquid is of subordinate importance. Discussion. It is shown that the results obtained can be explained by involving the notions of boundary layers of fluids with a structure changed under the influence of surface forces. The low-entropic structure of liquid in the boundary layer of hydrophobic surface is caused by forces arising inside liquid itself near weakly interacting surface, and is energetically the least favorable, corresponding to the maximum of free energy. Therefore, the particles behave as if there are hydrophobic attraction forces among them. Conclusion. Uncompensated charges near hydrophilic surface create high-entropic structure of water with normal orientation of its dipoles and increased density, which causes the appearance of structural hydrophilic repulsive forces among particles. Resume. Structural hydrophobic attraction and hydrophilic repulsion are endothermic processes. Their violation will be an exothermic process and its exo-thermicity increases as the temperature rises. The developed method of flotation is based on this property of structural forces: the stability of wetting films in flotation processes of micro-dispersions of minerals is changed by heating water in the boundary layers of air bubbles - hydrophobic cavities in water - due to the condensation heat of hot water vapor. For this purpose, aeration of the flotation system is carried out by a mixture of air and steam. Proposals for practical application and direction of future research. Practical significance of the project is to develop technology for flotation of the most difficult to extract forms of gold. Its essence is based on the effect of preferential adhesion of gold micro-dispersions on its own hydrophobic large particles - a solid wall. Thin plates, flakes and sheets of native gold are used as it. The aggregates formed by the above described mechanisms from poly disperse particles are extracted by flotation. In case of extraction in several steps the rough concentrate can be used as a solid wall (carrier minerals). In further research it is necessary to develop an organizational mechanism of joint processing of ores and gold placers.