Release Of Fluid Inclusions In Chalcopyrite And Its Interaction With Relaxation Surface

Chalcopyrite is an important representative of sulfide copper ore, and its flotation theory research has always been a hot spot of local and international research. Studies on flotation have formed complete theoretical systems, thereby providing important theoretical bases for chalcopyrite flotation. However, due to the complexity of the mineral surface and flotation solution system and the limitations in conventional detection techniques, calculation, and analysis methods, many defects remain in the research fields of chalcopyrite surface atomic configuration, the complex ion source in the solution, and its adsorption on the surface. These results lead to a lack of understanding on some phenomena on flotation, and its mechanism has not been fully revealed. Therefore, based on the quantum chemistry principle and by using advanced detection and analysis, as well as from the perspective of geochemical research and atomic-scale level, the release of fluid inclusions and its interactions with relaxation surface are investigated. These concepts have important theoretical value for in-depth and comprehensive understanding of chalcopyrite flotation mechanism.Based on widely reviewing relevant references, chalcopyrite and its associated minerals as the research object, the analysis and testing methods like IR-UV microscopic imaging, SEM-EDS analysis, HRXMT 3D scan, ICP-MS and IC were adopted. Fluid inclusion morphology, size, and component release to pulp solution have been investigated. Methods such as molecular mechanics, AFM atomic scale characterization, and density functional theory (DFT) calculation were used to study the electronic structure and surface relaxation properties of chalcopyrite. By determining copper ion concentration change in pulp solution with time, mineral surface potential real-time detection, and DFT calculation, the adsorption of copper ions released from fluid inclusions and its influence on surface electrical properties were investigated. Meanwhile, by DFT calculation, the interaction of copper and iron ions in pulp solution with xanthate collecting agent and the adsorption behaviors of water molecules, oxygen molecules, and xanthate on surface were studied. Through flotation experiment, the impact of fluid inclusion components on chalcopyrite flotation was explored. Thus, the self-induced activation flotation model with fluid inclusion components of chalcopyrite was established.A large number of fluid inclusions were found in the chalcopyrite crystal and fluid inclusions in various forms, presenting isolated or aggregated distribution, strip arrangement, and elliptical and irregular shapes. The individual linear dimensions of the inclusions ranged from 3 μm to 60 μm. Numerous Cun+, Fen+, Cl-, SO12-, and other ions were found in the fluid inclusions The release of these components and their entry into the pulp solution resulted in one of the main unavoidable ion sources when the mineral crystal broke. At the same time, many different sizes and shape of fluid inclusions distributed in bornite, sphalerite, quartz, and calcite associated with chalcopyrite and their components were released in the pulp solution when these fluid inclusions broke. Compared with the mineral dissolution experiment results, fluid inclusions component release was confirmed as the main source of unavoidable ions in pulp solution.The theoretical results showed that covalent and ionic bonds exist in the chalcopyrite crystal, which is a hybrid bond-type semiconductor. The interaction between Fe and S was relatively stronger than that between Cu and S, and electron transfer and the oxidation reaction were most likely to occur at the S center. Atomic configuration in the vertical and horizontal directions of the chalcopyrite surface showed greater change than that in bulk configuration; the sulfur atom layer extruded outward, the copper-sulfur and iron-sulfur bond lengths increased, and surface relaxation caused the atoms to aggregate and form sufur-rich atom configurations on the surface. The formation of a sulfur-rich surface on chalcopyrite was confirmed by molecular mechanics qualitative analysis, atomic characterization, and XPS analysis.The experiment results showed that the copper ions released from fluid inclusions and those that were artificially added were all adsorbed on the chalcopyrite relaxation surface, surface potential continued to increase with copper ion adsorption, and the adsorption equilibrium corresponded to potential balance. Xanthate anion adsorption activity increased because of copper ion adsorption on the relaxation surface, which under certain conditions was conducive to chalcopyrite flotation. DFT calculations also showed that the copper ion release from fluid inclusions, water and oxygen molecules in the pulp all were adsorbed on the relaxation surface, which theoretically proved the experiment result that copper ion from fluid inclusions could be adsorbed on surface. In addition, in water molecules mainly with oxygen-site adsorption, the lone-pair electrons of water molecules preferentially bond with iron atoms. Oxygen bridge-site adsorption had the highest adsorption energy, and electronic exchange occurred between the surface metal atom and the sulfur atom.The theoretical calculation results also showed that xanthan ions, copper and iron ions released from fluid inclusions, and copper and iron ions of the mineral surface would react. As a result, metal-xanthate complexes with various valence and spin states exhibit different properties. Two kinds of structures are mainly present in the metal-ethyl xanthate complex. Spin quantum number has an important influence on the interaction of iron ions with ethyl xanthate and its complex geometric structure. The interaction energy of Fe2+with ethyl xanthate increased along with the increase in spin number, and the spin state of iron-ethyl xanthate being IV with the high spin structure was the most stable. In the case of Fe3+, the most stable complex structure was found when spin state was IV. The Fe3+-ethyl xanthate complex was more stable than the Fe2+-ethyl xanthate complex. After ethyl xanthate ions interacted with Cu+, spin polarization energy and the non-polarization energy was the same, ionic bond of ethyl xanthan ion with Cu+ was relatively strong. Adsorption of ethyl xanthate with a single bridge structure on the disulfide bridge-site was the most stable. Surface atomic position distortion was caused by adsorption, and sulfur atom extruded further outward, which was conducive to sulfur polymer formation. Moreover, adsorption also increased the atomic coordination among the copper and iron atoms, and the charge transfer between the metal atoms of the surface and xanthate proved to be covalent. At the same time, the EX-Cu-S ternary structure exhibited higher adsorption energy.In-depth research on the fluid inclusion component release, crystal bulk structure, surface atomic relaxation, copper ion adsorption on relaxation surface as well as real-time examination of surface electrical potential and the theoretical calculation of xanthate adsorption behavior put forward the new concepts of a main source of "unavoidable" copper ion in chalcopyrite pulp being the release of fluid inclusion, copper ion adsorption on the "sulfur rich" surface changing mineral potential, and it being conducive to adsorption of the xanthate collector. Moreover, the self-induced activation flotation theory model of fluid inclusion components was presented, thereby enriching the development of the basic theory of flotation and placing important theoretical value on chalcopyrite flotation study.