The behavior of rare-earth elements and major impurities during the nitric-acid decomposition of a lean yttrofluorite concentrate by the method of sorption conversion is studied. The decomposition conditions providing satisfactory extraction into the sorbent for rare-earth elements, especially yttrium and yttrium group lanthanides, are determined.
A simple method for obtaining sea buckthorn (Hyppophae rhamnoides) oil with carotenoid content high enough to comply with the requirements for sea buckthorn oil based wound remedy is proposed. A method is based on supercritical carbon dioxide extraction of dried pressed cake of sea buckthorn berries at high extraction pressures (up to 55 MPa) for obtaining higher carotenoid concentration and subsequent centrifugation in order to separate solid wax fraction. Chromatography and spectrophotometry analyses of such oil support the potential perspective of the proposed method.
The interaction of perovskite concentrate with nitric acid under atmospheric conditions and at an excess pressure was studied. High efficiency was achieved in the separation of components in the form of a solid phase (hydrated precipitate of titanium and rare metals) and a liquid phase containing calcium, rare-earth metals, and thorium. It was shown that the conditions of the acid treatment of the resulting precursors determine their structure and composition, which, in turn, determine the directions of their further processing to obtain final products. In particular, it was established that an increased pressure in the reaction zone causes rutilization of the hydrated precipitate, and therefore its further processing to produce titanium dioxide and rare metals should be carried out by chlorination.
An approach based on the gas-phase processing of secondary wastes in an HNO3 (vapor)–air or NOx–H2O (vapor)–air atmosphere with further Mn and Cr leaching with water is proposed for Mn and Cr extraction from the secondary wastes of metallurgical plants (fly ash from the ore-dressing plant of the Norilsk Combine and rock refuses from the Punda Gourda Nickel Production Combine of the Cuban State-Owned Commercial Caribbean Nickel Company). It is shown that the preliminary treatment of secondary wastes in a nitriding atmosphere at a temperature of 400–425 K for 5 h makes it possible to leach Mn from the volume of secondary wastes. For the fly ash from the ore-dressing plant of the Norilsk Combine and the rock refuses from the Punda Gourda Nickel Production Combine of the Cuban State-Owned Commercial Caribbean Nickel Company, the degree of Mn extraction with water is less than ~33 and ~65% of their total content in the wastes, respectively. The degree of Cr extraction is less ~2% in all cases.
An effect of supercritical carbon dioxide compressive self-heating was observed both in stationary and flow regimes. The effect is probably caused by fluid compression in near-adiabatic conditions during system filling and pumping. This phenomenon should be taken into account in process design and optimization for systems employing sub- and supercritical fluids, such as supercritical fluid extraction, chromatography, aerogel drying etc.
The results of extractive distillation of a four-component mixture of solvents are predicted by means of simulation using the Aspen Plus 10.0 software. Schematic flow diagrams of separation are suggested using various selective agents in distillation columns operating under different pressures.
The structural and energy characteristics of some commercial and laboratory microporous carbon adsorbents applied in the cyanide gold recovery technology are studied. The average effective widths of the micropores in these adsorbents are close to 1.1 nm. The successive application of such adsorbents is explained by molecular sieve effects with respect to the cyanide gold complex.
The paper studied the extraction of lanthanides from nitrate solutions (0.01 M HNO3 + 0.1 M NaNO3) in hexane–isopropanol–water three-component systems using Cyanex 572 as an extractant. The experiments showed the promise of using the extractant Cyanex 572 for the separation of lanthanides from nitrate media in three-component systems.
Laboratory samples of a new functional material are obtained by mixing two fractions of crushed gabbro rock with different particle sizes in the ratio coarse : fine = 1 : 10 and discrete basalt fibers in an amount of 8 wt % of the initial mass of the mixture. Potassium liquid glass is used as a binder. The resulting mass is placed in a mold, followed by pressing and molding of blanks. After drying, they are sintered. The sintered samples have the shape of a cylinder with dimensions h × d = 10 × 10 mm. For all samples, the following are determined: pycnometric density, Brinell hardness, tensile strength, and residual deformation.
An assessment is made of the current state of the global food security, which arises as a result of new challenges, in order to achieve the UN Sustainable Development Goals. Currently, aquaponic technologies are considered quite promising for providing regional consumers with food (hydrobionts and phytoproducts). Reagent-free technologies for intensifying plant growth and development (electromagnetic influence, ultrasonic waves, corona discharge) are analyzed. The use of installations for the electrolysis treatment of aqueous solutions for growing hydrobionts before feeding them into hydroponic modules is substantiated. The results indicate a significant increase in plant productivity by more than 30% after electrochemical treatment. Changes in the hydrochemical and hydrophysical properties of water after electrolysis are analyzed. A scheme of an aquaponic system for intensifying reagent-free electrolysis of growing microgreen plants is proposed and verified. It is substantiated that further research should be aimed at building process-control systems in aquaponic installations and creating specialized energy-efficient DC power supplies.
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