О влиянии «гидрофобности» газовой фазы на образование флотокомплексов в процессах флотации

Abstract

Introduction. A model of a three-phase system in which, as a result of hetero coagulation from a bulk liquid, its thin layer has formed, the surfaces of which separate the gas and condensed phases with different potentials, is a wetting film. The study of wetting films adds to the knowledge of the nature of the structure-induced surface forces acting in them, which serves to develop the theory of hetero coagulation and is of interest for solving various topical problems of the theory and practice of flotation. The purpose of the work is to study the influence of “hydrophobic” properties of the gas phase on the separation of minerals by flotation with a vapor-air mixture in flotation schemes with jet countercurrent flow of feed and rough concentrate. Materials and Methods. Methods and installations have been developed to investigate the temperature dependence of the equilibrium thickness of wetting films and wetting edge angles. Studies of wetting films are supplemented by measurements of induction time at adhesion of minerals to each other and to an air bubble on a specially designed installation. In-situ flotation experiments were performed on a sample of apatite-nepheline ores. Results. The temperature dependence of the equilibrium thickness of the wetting film has been revealed, which does not contradict the experimentally established decrease of the exponentially decreasing (non-oscillating) part of the cleavage pressure with increasing temperature. It is shown that the temperature dependence of the boundary angles formed by the wetting film on the hydrophobic and hydrophilic surface is multidirectional. The connection between the temperature dependence of the boundary angle and the temperature dependence of the spreading coefficient obtained from Young’s law and determined by multiplication of parameters characterizing the magnitude and long-range action of forces caused by the difference between the structure and properties of the liquid in the boundary layers and their values in the volume is shown. “Hydrophobicity” of the bubble is associated with a smaller range effect of structural repulsion forces compared to hydrophobic attraction forces. By measuring the induction time, it is shown that the “hydrophobicity” of air manifests itself in the difference in the stability of wetting (when hydrophobic and hydrophilic particles adhere to the air bubble) and symmetric (when particles of the same hydrophobicity/hydrophilicity adhere to each other) films as the temperature increases. Discussion. In the framework of the phonon mechanism of surface forces, the dynamic structure of the liquid in the boundary layers (the sign and magnitude of the phonon component of the bowing pressure) determines the selectivity of aggregation and completeness of particle extraction, as well as the stability of symmetric and wetting films from temperature. Conclusion. When discussing the stability of disperse systems, the concepts of additional (to dispersive (van der Waals) and ionic-electrostatic interactions) forces associated with the overlap of boundary layers of liquids with structure parameters changed compared to their bulk values are fruitfully used. Such differences are understood as static deviations of the structure and properties of the liquid induced by the surface. However, the main reason for changes in the stability of wetting films at increasing temperature may be the high sensitivity to temperature of the entire set of rotational and vibrational motions of atoms and molecules of the liquid, i. e., its dynamic structure and the associated phonon component of the wedging pressure. Resume. The results of the study can be used to improve the technological performance of ores enriched by flotation. Consideration of the influence of linear tension on the system with the line of threephase contact will be useful for revealing the peculiarities of flotation of micro-dispersions of minerals by the developed technology.