Kineticand thermodynamic aspects of flotation beneficiation of polymetallic raw materials

The article presents the results of the development of a method-ological approach to the analysis of kinetic and thermodynamic parameters for improving the efficiency of flotation processing of polymetallic raw materials.The kinetic dependences of flotation, the hydrophobizing ability of butyl potassium xanthogenate, and the effect of reagents on preliminary mechanical activation were studied, and flotation modeling with and with-out an oxidizer was performed. The best results of convergence with the kinetic dependences of flotation are shown by the Beloglazov equation, the Kelsall and the modified Kelsall models. Technological indicators of sul-fide flotation in the presence of oxidants are higher, which can be ex-plained by the intensive oxidation of the formed transient ions on the sur-face of minerals, which contributes to the alignment of the flotation properties of the surface.It is possible to integrate the proposed research methods into technological schemes in order to optimize technological in-dicators and increase profits.

Effect of Mechanical Activation of the Powder Mixture on the Structure and Properties of Boro-Aluminized Low-Carbon Steels

Introduction. Boro-aluminizing is one of the most effective ways to improve the performance properties (corrosion resistance, heat and wear resistance) of low-carbon steels. Solid-phase methods of thermochemical treatment (TCT) are carried out from saturating mixtures based on powder materials. Preliminary mechanical activation of these powders is one of the ways to improve the properties of the resulting diffusion layer. The purpose of this work is to determine the effect of preliminary mechanical activation of the powder mixture on the structure and properties of the boro-aluminized layer on the surface of low-carbon steels. Methods: The paper considers the results of research on the preliminary mechanical activation of the saturating mixture in the TCT of low-carbon steels (for example, St3 and 3Kh2V8F) based on powdered boron and aluminum carbide. The results of experiments on preliminary mechanical activation of the saturating mixture are shown, and the dependence of the particle size of the initial mixture on the duration of mechanical activation is established. Samples of steels with a diffusion layer after TCT are obtained. It is found that the process temperature has a significant effect on the thickness of the layers obtained. With an increase in temperature from 950 ° C to 1050 ° C on St3 steel samples, the layer thickness increases from 120 to 150 μm, on 3Kh2V8F steel samples – 105 and 140 μm with a holding time of 2 h and 4 h, respectively. The microstructure of the obtained samples is investigated; dependence diagrams of the microhardness distribution on the depth of diffusion layers are shown. The distribution of Al over the depth of the resulting boro-aluminized layer is established. As additional studies, the saturation capacity of the mixture after a single application in the TCT process is studied. Results and discussions. The principal possibility of using mechanical activation in TCT to obtain diffusion layers with specified strength characteristics is established. An increase in the duration and temperature of TCT in mechanically activated mixtures leads to an increase in the aluminum content in the layer.

SYNTHESIS OF THE NANOCOMPOSITE BASED ON IMPACT DIAMONDS AND SILICON CARBIDE UNDER CONDITIONS OF HIGH PRESSURE AND TEMPERATURE

The article studies the structure, phase composition and physicomechanical characteristics of the nanocomposite based on impact diamonds. It is shown that the additions of a binder based on SiC and Si lead to reduction of the defectiveness of the nanocomposite and increase in the uniformity of its structure compared to the material without additives. Moreover, increase in the binder content also leads to the inversion of the structure type of the nanocomposite from polycrystalline to matrix. It is established that the addition of amorphous carbon black and boron affects the refinement of the nanocomposite matrix structure due to the formation of secondary finedispersed nanostructured SiC and boron carbide. Preliminary mechanical activation of the reaction mixture leads to structural changes in the synthesized material in comparison with the material obtained without the use of mechanical activation. In this case, the hardness of the samples obtained under comparable synthesis modes increases, which is associated both with the formation of a fine-grained structure of the material and with the phase transformation of lonsdaleite to diamond. An analysis of the microhardness and heat resistance of the obtained samples makes it possible to conclude that the achieved level of physicomechanical parameters of the diamond nanocomposite allows it to be used in a stone-processing tool for treating medium hard rocks.

MAGNESIOCHROMITE (MgCr2O4) SYNTHESIS: EFFECT OF MECHANICAL AND MICROWAVE PRETREATMENT

Magnesiochromite spinel synthesis based on oxides, hydroxides and nitrates of magnesium and chromium was investigated. The precursors reactivity was compared by means of effective rate constants calculated by Ginstling-Brounshtein equation. The possibility of use of this equation was confirmed by the dependences linearity with high linear approximation coefficients. The reactivity of MgO various forms (soft-burned, or caustic magnesite, and dead-burned, or periclase) in the spinel formation was compared. Oxide precursors (especially with the periclase participation) reacted with the substantially less rate in comparison with hydroxides and salts. The influence of a preliminary mechanical activation by impact-and-attrition (planetary mill) and attrition (ball-ring mill) action as well as a microwave treatment (2.45 GHz) was analyzed. The most positive effect of a mechanical treatment in a planetary mill that was associated with an activation of Mg and Cr compounds became apparent in the field of relatively low temperatures (700-1100 °С). For example, MgCr2O4 yield at 1000 °С and the joint impact treatment of oxides was twice as much than under the simple mixing. The subsequent temperature rising lead to some decrease of a pretreatment effect so long as diffusion coefficients in these conditions grew, so the reaction run rapidly even without a preliminary mechanical treatment. It was noticed that an appreciable reduction of MgO reactivity in the spinel formation after a certain attrition in a ball-ring mill linked to the plane sliding in cubic crystals and resulted in the removing of the most disordered and defective layer from grains and the plane surface uncovering. The combined method consisting of a mechanical treatment of magnesium and chromium nitrates mixture in a planetary mill and the subsequent burning in a thermal kiln (1000 °С) was considered as the most effective as it resulted in practically single product. The microwave treatment took up an intermediate position by the effectiveness.

Effect of the Mechanical and Thermal Prehistory of Precursors on the Zinc Spinel Synthesis

Thezinc spinel (gahnite) formation by a treatment of reaction mixtures of Zn and Al oxides, hydroxides, and salts was investigated. The influence of a preliminary mechanical activation by impact (planetary mill) and attrition (ball-ring mill) action as well as a microwave treatment was analyzed. The combined method consisting of a mechanical treatment of nitrates mixture in a planetary mill and the subsequent burning in a thermal kiln was considered as the most effective as it resulted in practically single product

Acid-free activation process of Vyatka – Kama phosphate in the presence of nitrogen-and potassium-containing salts

The work describes the production of complex fertilizers of prolonged effect on the basis of acid-free processing of phosphate rock of the Vyatka-Kama Deposit. The authors investigated the influence of chemical composition of salts and mass ratio between salt and phosphate components on the degree of activation of the phosphorite flour of the Vyatka-Kama Deposit (VKPF) during its treatment with solutions and suspensions of nitrogen-containing mineral salts and potassium chloride. It has been determined that the content of available form of P2O5 in phosphorite increases by 1.5-2 times, and the greatest activating effect is provided by ammonium salts. The use of preliminary mechanical activation of VKPF, in the method investigated, provides the increase in the content of available form of P2O5 by 11–13 %. The mechanism of interaction of the main minerals of phosphorite with salt additives (ammonium sulfate, ammonium nitrate, ammonium chloride, carbamide, potassium chloride) is proposed. The dynamics of changes in the content of ammonium nitrogen in fertilizer compositions at each stage of the process has been determined. The method for producing complex fertilizers based on phosphorite flour of the Vyatka-Kama Deposit has been developed and patented.