Modeling of minerals contact interactions dynamics in flotation system

Introduction.The work is aimed at studying the dynamics of contact interactions of minerals under conditions modeling the process of froth agitation flotation. The study of the regularities of contact interactions is an urgent task not only because they are used to determine the fundamental macroscopic and microscopic properties of flotation systems, but also because the forces in the contacts between minerals are the most important factor in carrying out a variety of technological processes of mineral separation in ore dressing by flotation. Materials and methods. The main method of research is theoretical analysis of the results of experimental study of aggregative stability of aqueous dispersions of minerals by sedimentoluminescence method, laboratory scale flotation experiments performed on mono-mineral quartz using a specially designed flotation method. Results. It is shown that aqueous dispersions of hydrophilic quartz form precipitates whose volume decreases with increasing temperature, which can be explained by the growth of hydrophilic repulsion forces. The increase in the volume of the precipitate with increasing temperature in the aqueous dispersion of hydro-phobized quartz is associated with the strengthening of structural hydrophobic attraction. A method of quantitative estimation of the value of structural forces based on the results of sediment-lumetric measurements is proposed. The calculation shows that the forces in the contacts between hydrophilic quartz particles are the first micro-dines, and their magnitude increases by an order of magnitude with hydro-phobization of quartz and temperature increase. Discussion. It is hypothesized that the forces in contacts between minerals in their aqueous dispersions are related to the fact that the static and dynamic properties of water at the interface do not have the properties of the bulk phase. When anisotropic layers belonging to different interfaces overlap, when from one layer it is possible to reach the other without crossing regions homogeneous in intensive properties (i.e., possessing phase properties), forces of structural hydrophilic repulsion or hydrophobic attraction appear between particles. Structural interactions are an endothermic process and the main way to detect them in disperse systems is by temperature change. In aqueous dispersions of hydrophilic minerals the temperature increase is identical to the action of reagents-depressors in flotation – forces in mineral contacts decrease. On the contrary, in aqueous dispersions of hydrophobic minerals the temperature increase is qualitatively similar to the decrease of surface wettability under the action of reagents-collectors – decrease of forces of structural hydrophilic repulsion and increase of forces of hydrophobic attraction. Conclusion. Surface forces of structural origin, which determine the dynamics of contact interactions, are considered in relationship with the flotation factors of mineral micro-dispersions: the transition of wetting films into a metastable state at increasing temperature is associated with an increase in the forces of structural hydrophobic attraction and weakening of the forces of structural hydrophilic repulsion, which allows to radically change the conditions of the flotation process. The formation of flotation complex is determined by the balance of forces of attraction and repulsion, the radius of action of which is localized in thin wetting films, which means the possibility of transition in the delivery of coolant from the macro level – increasing the temperature of the whole flotation system – to the micro level – increasing the temperature of water in wetting films. It is experimentally confirmed that at hydrodynamic interaction of coolant with cold water in conditions simulating aeration of pulp at flotation, at the achieved level of heat transfer, one of the methods of flotation with heating of water in wetting films can be the use of down flow of air and water vapor as a gas phase. The description of the flotation mechanism is given with attraction of ideas about surface forces caused by inhomogeneity of liquid boundary layers and their temperature dependence. The developed mechanism is confirmed by the results of experiments on flotation of minerals with a collector, hydrophobic interactions between long hydrocarbon radicals in the molecules of which are the cause of growth of particle recovery. Resume. Aqueous mineral dispersions and hydrocarbon solutions are qualitatively similar in that the forces in the contacts between hydrophobic minerals and hydrocarbon radicals are related to the fact that the static and dynamic properties of water at the interface do not have the properties of the bulk phase. At the overlap of anisotropic layers belonging to different interfaces, when from one layer it is possible to reach the other without crossing areas homogeneous in intensive properties (i.e. possessing phase properties), forces of structural hydrophilic repulsion or hydrophobic attraction appear between particles. Structural interactions are an endothermic process and the main way of their detection in disperse systems is temperature change. It is shown that aqueous dispersions of hydrophilic quartz form precipitates whose volume decreases with increasing temperature, which can be explained by the increase in hydrophilic repulsion forces. The increase in the volume of the precipitate with increasing temperature in the aqueous dispersion of hydro-phobized quartz is associated with the strengthening of structural hydrophobic attraction. A method of quantitative estimation of the value of structural forces based on the results of sediment-lumetric measurements is proposed. The calculation shows that the forces in contacts between hydrophilic quartz particles are the first micro-dines, and their magnitude increases by an order of magnitude with hydro-phobization of quartz and temperature increase. The extent of anisotropic interfacial surfaces allows to pass from the macro level – increasing the temperature of the whole flotation system – to the micro level – increasing the temperature of water in wetting films during coolant delivery. By field experiment on flotation of mono-mineral quartz, the surface of which is activated by calcium chloride and hydro-phobized with sodium oleate, the technological efficiency of using air-water vapor mixture as a gas phase for pulp aeration is proved. Proposals for practical application and direction of future research. The obtained results can be used in the development of technological solutions aimed at improving the performance of fl otation of ores by changing the balance of structural forces of attraction and repulsion by increasing the temperature of water in wetting films.