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 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

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 describes the theoretical and experimental research data on possibility to improve the quality of the end concentrates of float-and-sink, X-ray luminescent, adhesive and froth separation. The method of nitride hardening is proposed for ferrosilicium grain surface with the hardened layer depth in the range of 30–60 nm for reducing ferrosilicium corrosion rate by 2.7 times at the preserved process properties. The necessity of adding the primary float-and-sink flotation circuit with two-stage magnetic separation to decrease the yield of rough concentrates and to improve their quality owing to removal of 29–95

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 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 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 thermodynamic analysis and tests of minerogenesis under higher temperatures determine conditions of thermochemical decomposition of hydrophilic attachments on diamond surface. It is found that hydrophilic mineral attachments can be removed from diamond surface by combining thermal treatment of slurry at the temperature of 80–85  $$^\circ$$ C with electrochemical treatment of recirculated water, which enables required change in ion–molecule composition of water phase in the slurry. The hybrid conditioning technology ensures recovery of the natural hydrophobic behavior and floatability of diamonds and enhances performance of froth flotation of diamonds by 5.1%.

The main reason of decreasing diamond recovery through froth separation is their surface hydrophilization by hypergene minerals and technogenic films, crystallized from the supersaturated aqueous phase, fixed on the surface structurally or by adhesion. Various types of physical actions, including thermal and ultrasonic treatment of the initial feed of froth separation, are recommended to increase the diamond-bearing kimberlite beneficiation process performance, providing cleaning of the surface of diamonds due to destruction of their accretions with rock minerals and removal of film hydrophilizing coatings from the surface of diamond crystals. A sample of kimberlite material with a given content of diamonds of 1.5–2 mm in size was used as a subject of research in the process of froth separation. The results of thermodynamic calculations and experimental research have substantiated the necessity of using electrochemical conditioning of recycled water for increasing the efficiency of diamond surface cleaning in froth separation operation when using the process of thermal treatment of initial ore feed. The use of diaphragmless electrochemical conditioning of recycled water increases the efficiency of thermochemical dissolution of hydrophilizing compounds on the surface of diamonds through reducing the concentration of calcium and carbonate ions as well as through shifting the medium pH to 6.1–6.5. The measurements of the limiting wetting angle showed that the maximum effect of increasing the diamond surface hydrophobicity was achieved when heat and electrochemical treatment were used together. Laboratory studies showed the possibility of increasing flotation diamond extraction from 65.7 to 91.4 % through application of electrochemical conditioning of recycled water. The optimum parameters of diaphragmless electrochemical treatment of recycled water of the froth separation cycle in conditions of application of pulp heat treatment: current density of 175–200 A/m2 and power consumption of 1.2–1.5 kWh/m3. Tests carried out at processing plant No. 3 of the Mirny GOK (Mining and Processing Complex) (Mirny, Yakutiya) showed that the application of the developed froth separation process intensification method with the use of thermal treatment of pulp and electrochemical diaphragmless treatment of recycled water allowed increasing the recovery of diamonds of +0.5–2 mm size by 4.9–5.1 %.

Using a combination of energy - dispersive X-ray spectroscopy, X-ray diffraction, X-ray fluorescence, Infrared and X-ray photoelectron spectroscopies, the effect of acids (sulfuric, hydrochloric, and nitric) and energy impacts (electrochemical, mechanochemical, high power electromagnetic pulses, ultrasound) on the leaching parameters of eudialyte concentrate was studied. Zr and sigma REE recovery after a single stage when using sulfuric acid was 91.5% and 82.4%, when using hydrochloric acid - 83.9% and 83.6%, when using nitric acid - 76.9% and 79.6%, respectively. Using sulfuric acid leads to the formation of the maximum amount of silicate gel and high loss of valuable components, while hydrochloric acid is highly aggressive to the process equipment. The possibility of nitric acid leaching intensifying by applying ultrasonic impacts was determined which disperse colloidal silicate gel, prevents the formation and precipitation of the gel on the mineral surface, provides the formation of numerous defects and microcracks on the eudialyte grains surface, including breakage thereof. Three stages of nitric acid leaching of eudialyte concentrate with an ultrasonic treatment in the first stage provide the highest recovery of zirconium (97.1%) and rare earth elements (94.5%) at a minimal loss of valuable components with silica gel. The process is recommended for commercialization.

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 investigation of influence exerted by ultrasound processing on recovery of zirconium and rare earth elements in pregnant solution of acid leaching of eudialyte concentrate is described. The methods of X-ray photoelectron spectroscopy and analytical scanning electron microscopy are used to study structural, chemical and morphological characteristics as well as elemental composition of minerals in eudialyte concentrate before and after acid leaching.

The mechanism of weakening and directional change in structural and chemical properties of eudialyte under nonthermal exposure to nanosecond high-voltage electromagnetic pulses and nitric-acid leaching is studied. The methods of X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy and microhardness measurement are used. The rational mode of high-energy pulsed treatment is determined. After such mode treatment, the acid leaching of eudialyte concentrate results in recovery of zirconium and total rare earth elements higher by 1.7 and 1.4 times as against reference standards.

Due to a technical error volume 53, issue 4, 2017 has been published online with an incorrect cover data. The issue has erroneously been distributed with the cover date July 2018. The correct caver date for volume 53, issue 4 should be July 2017.

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 article gives a report on integrated experimental research into targeted change of chemical and phase composition of surface and increase in contrast of physicochemical, electrical and electrochemical properties of tantalite, columbite and zircon under treatment by acid product of water electrolysis—anolyte (pH < 5) and by muriatic solution (HCl, pH 3–3.5). The X-ray photoelectron spectroscopy, high resolution spectroscopy and chemical and electrophysical techniques reveal the mechanism of structural–chemical surface transformation of tantalite, columbite, zircon and feldspar under leaching in acid solutions; this surface transformation mechanism consists in activation of dissolving of iron- and silicate-containing surface films and high-rate oxidation of iron atoms in surface layer of tantalite and columbite, with transition of Fe(II) to Fe(III) and surface destruction of zircon, with formation of oxygenvacant defects of SiO3 2− and SiO2 0 type under influence of anolyte.

Under analysis is interaction between 1-phenyl-2,3-dimethylaminopyrazolone-5 (AMD) and copper in solution and on the surface of chalcopyrite. It is found that AMD experiences chemical adsorption on the surface of chalcopyrite as a compound with copper. Effect exerted on adsorption of AMD agent on copper sulfide by ammonium rhodanate (NH4CNS), introduced as an additional ligand, or its mixture with acetic acid is defined. Based on the analytical research and the analytical chemistry data, the type of adsorption on the surface of chalcopyrite is determined. The flotation tests on monomineral fraction of chalcopyrite and pyrite, and copper sulfide ore prove selectivity of AMD in separation of chalcopyrite and pyrite.

The article analyzes flotation and adsorption capacity of a new complexing reagent AMD (nitrogen and oxygenated organic compound belonging to phenylpyrazole class) toward sphalerite, chalcopyrite and pyrite, combined with complexing modifiers, at varied consumptions of the reagents, in wide range of alkalinity. The basis for improvement of pyrite and sphalerite separation in flotation is provided.