The authors studied theoretically and experimentally the compositions of luminophores in modification of spectral characteristics of anomalously luminescent diamonds to the effect of their recovery. ...Attachment of a luminophore-bearing composition at the diamond crystal surface takes place owing to the stable aggregation of the diamond, organic liquid and inorganic luminophores by the mechanism of hydrophobic interaction in polar medium. Stability of such aggregates is ensured by intense adhesion of the components having similar surface energy. For diamond and zinc sulfide, the dependence of the wetting angle, generated by the organic liquid drops in the water medium, on the surface tension of the organic phase exhibits the extreme nature. By the coordinate of the maximum of the wetting angle–organic liquid surface energy curve, the surface energy of diamond and zinc sulfide is determined. It is proved that the organic liquids and oil products, which are used as organic collectors and have surface energies similar to the luminophore surface energy, maximize the force of hydrophobic interaction and stability of the diamond–organic liquid–inorganic luminophore aggregate.
The integrated thermodynamic calculations and spectral analyses validated concentrations of hydrophobization agents (butyl xanthate and sodium oleate) to ensure chemisorption and chemical interaction ...with silicate matrix of luminophore FL-530. It is found that in the optimized conditions, hydrophobization agents interact with zinc orthosilicate without volume reaction which degrades spectral characteristics of luminophore. The increased oil receptivity of luminophore FL-530 improves its ability to remain in the organic phase of emulsion and to better attach to the surface of diamonds. The UV visiometrics revealed better attachment of hydrophobic luminophore at diamonds. The optimal concentrations of solutions of butyl xanthate and sodium oleate are determined. The tests using separator Polyus-M proved efficiency of hydrophobic luminophore FL-530 which essentially enlarged amplitudes of the fast and slow signal components in X-ray fluorescence of slight fluorescent diamond and their recovery in separation.
The authors have correlated the fluorescence spectrum with the spectrum and kinetics of X-ray luminescence of organic collectors. The correlations prove applicability of organic collectors with ...modifying agents. From the integrated evaluation of organic liquids by the criteria of their adhesion capacity relative to diamonds and extraction capacity relative to inorganic luminophores, the selected organic collectors are: diesel, heavy gasoil of catalytic cracking, and their mixture. The spectral functions of organic luminophores contained in organic collectors are replaceable with polyaromatic hydrocarbons which generate intense signals similar to the signals of organic luminophores. Efficiency of modifying agents containing organic collectors and hydrophobic luminophores E-515-115-G5 and FL-530-GZ is high. The test organic collector was heavy gasoil of catalytic cracking and diesel fraction at a ratio of 61–9:1. Recovery of weakly and abnormally fluorescent diamonds was 80–90%, while recovery of kimberlite was not higher than 1%. The results allow recommending the developed modifying agents for the commercial-scale X-ray luminescence separation of diamond-bearing materials.
The article describes the studies into the current flow charts available for processing diamond-bearing kimberlites of complex material constitution. The theoretical and experimental substantiation ...is given for the methods to modify properties of the mineral components to enhance selectivity of their separation. Efficiency of luminophore-containing compositions is proved for weakly and abnormally luminescent diamond. Luminophores modify the spectral and kinetic properties of diamond crystals to the values at which diamonds become recordable and recoverable in the current flow charts of X-ray luminescence separation. Efficiency of integration of ultrasonic, thermal and electrochemical methods in removal of hydrophilic impurities from diamond surface toward enhanced recovery of diamonds by grease technology and froth separation is demonstrated. The method is developed to increase the corrosion resistance of ferrosilicon by means of its nitride coating which unsupports interaction with corrosive components of the water environment. Experiments justify that magnetic separation improves the quality of preconcentrates of float-and-sink separation owing to removal of up to 95.8% of magnetic minerals from the diamond-bearing material.
The authors study the processing behavior of luminophore-containing blends of zinc and cadmium chalcogenides with a view to using them for the modification of the kinetic and spectral characteristics ...toward enhanced recovery of weakly and abnormally luminescent diamonds usually lost in X-ray luminescence separation. It is shown that zinc and cadmium sulfides activated by copper and silver have the kinetic and spectral characteristics which are the most similar to natural diamonds. The procedure developed for the improvement of the processing behavior of luminophores with zinc and cadmium sulfides includes the circuits of surface activation with copper cations and subsequent treatment in the potassium butyl xanthate solution. The visiometric analysis reveals that the increased oil receptivity of luminophores and the dispersing agents ensure selective attachment of luminophores to diamonds. The bench testing proves feasibility of complete extraction of diamonds to concentrate, including weakly and abnormally luminescent crystals.
The modification procedure for the kinetics and spectral characteristics of fluorescent diamonds using luminophores ensures the simultaneous increase in the amplitudes of the long- and ...short-persistent luminescence signals at a preset ratio (1 : 1). Abnormally and weakly fluorescent diamonds after luminophore modification have elevated amplitudes of the kinetics and spectral characteristics, and are identifiable as natural crystals with the required luminescence intensity. This approach allows the simultaneous increase of the collapse and the decay constant of X-ray luminescence signal. As a result, abnormally and weakly fluorescent diamonds acquire higher values of these characteristics, become detectable as natural diamonds and are recoverable in X-ray fluorescent separation.
The found interaction mechanism between a mineral–diamond mixture and a modifying agent includes the stage of adhesive attachment of luminophore at grains of diamonds and kimberlite. The selected ...compositions of modifying agents and the modification process parameters ensure efficient attachment of luminophore-bearing compositions at diamonds. The proposed criterion of selective action of modifying agent on spectral characteristics of diamonds enable choosing modes of recovery of weak and high luminous diamonds from kimberlite ore in X-ray luminescence separation. The rational variation parameters are determined for the organic collector composition, water phase of a modifying agent and for the process of modifying treatment of diamond–kimberlite products before the X-ray luminescence separation. The test of the selected compositions of modifying agents and the diamond-bearing product treatment modes proved almost complete extraction of weak and high luminescence diamonds to concentrate at minimized yield of kimberlite.
The article gives test data on the influence exerted by energy impacts (ultrasonic, electrochemical and thermal) on the recovery of zirconium and rare earth elements from eudialyte concentrate to ...leach solution in acid leaching. An original installation is developed for the implementation of leaching. Based on the research findings on the kinetics of acid leaching of eudialyte concentrate and on the change in the concentrate micro-structure and phase composition, the mechanism for the influence of integrated energy effects on the efficiency of recovery of zirconium and rare earths into leach solution is substantiated.
The authors have studied the mechanism of controlled modification of composition, structure, chemistry, physicochemical and process properties of columbite, tantalite, zircon and feldspar at the ...meso-, micro- and nanoscales after nonthermal treatment by high-voltage nanosecond electromagnetic pulses. The studies used methods: X-ray photoelectron spectroscopy, scanning electron and atomic force microscopy, potentiometric titration, electromigration chromatography, Kelvin probe force microscopy, microhardness metering and assessment of hydrophobic behavior and flotation activity of the minerals. It is found that changes in the chemical state of atoms on the surface of minerals are mainly connected with the sequential transformation of stages in the process of formation and modification of a functional cover of mineral surface, with variation in a ratio of different type hydroxyl groups on the surface of columbite, zircon and feldspar, which conditions contrast physicochemical properties of rare metal minerals and improves selectivity of their separation by flotation.
The authors provide the theoretical and experimental justification for the effective methods of modification of saponite—pillaring and thermal treatment—which ensure production of sorbents possessing ...high cation exchange capacity relative to cations of heavy metals. The mechanism of pillaring and thermal modification of a saponite-containing product at the temperature of 625 °C involves expansion of layers of the mineral, formation of additional acid or redox sites (pillaring) and restructuring with generation of metastable phases (thermal treatment). Modification of saponite increases static exchange capacity relative to copper cations by 2 times after pillaring and by 2.6 times after thermal treatment.
