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Abstract
A number of industrial and technology sectors have been paying attention to a particular chemical element in recent years, namely niobium (Nb). There are many niobium deposits scattered around the world, and for each deposit different technologies are applied for extraction and processing due to the singular characteristics present at each site. In this paper, a review of the many technologies for niobium production will be presented starting at the mine, through techniques of niobium ore beneficiation and refining, technologies to produce ferroniobium alloy, oxides, special oxides, ammonium niobium oxalate, the separation of niobium from tantalum, and techniques to reduce and purify metallic niobium.
Key words: niobium production; pyrochlore concentration; metallic niobium; tantalum-niobium separation; ferroniobium; niobium oxides.
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Abstract
Quantitative and qualitative regularities of a collector low and high molecular weight fractions distribution between solid and liquid phases in foam separation process were determined with the use of extraction-spectrophotometrical technique. The feasibility of producing a collector with optimal ratio of fractions of light distillates, hydrocarbon oils, resin, and asphaltenes by mixing M-40 fuel oil with diesel fuel oil in specified ratios was substantiated. It was shown that applying compound collectors with M-40 fuel oil weight percentage of 60-70 enabled increasing diamond recovery by 2.7-3.5%. Similar increase was also achieved when using F-5 bunker fuel oil diluted by 10-18% with diesel oil fraction. The optimal temperature of 24 °C for initial ore feed conditioning with flotation agents and foam separation providing maximum diamond recovery into concentrate and high selectivity was determined. The proposed collectors and temperature conditions enabled increasing diamond recovery.
Key words: Diamonds; Foam separation; Extraction; UV spectroscopy; IR spectroscopy; Compound collectors; Fuel oil; Diesel fuel oil; Medium temperature.
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Abstract
Phytomining, although predominantly in its early stages on the broader scientific scope of investigation, has garnered interest in metals such as Ni, Au, or rare earth elements (REE). However, Zn pollution from mine wastes, smelters, coal ash and other anthropogenic sources has become an environmental problem. Phytoremediation by hyperaccumulating plants is one of the proposed solutions to mitigate the pollution. Therefore, a need to utilize or dispose Zn hyperaccumulating plants occurred. Since studies of certain hyperaccumulating plant species have been previously conducted in order to extract metal products, similar hydrometallurgical and pyrometallurgical techniques were tried with Zn. The hydrometallurgical route was more focused on producing crude eco catalysts for organic chemistry or separating metal hydroxides by cementation. This was achieved with acid leaching of the ash which was obtained by calcinating the aboveground plant biomass. On the other hand, the pyrometallurgical route was more focused on safe and eco-friendly disposal of combustion products such as ash or biochar, while achieving zero toxic gaseous emissions from biomass pyrolysis. Regardless of the approach further research is needed to investigate the stabilization of metals that remain in the solid fraction during combustion and lowering the metal content in produced gases. So far, none of these technologies have been brought to a semi industrial scale and there is the potential of linking those two approaches together.
Key words: Phytomining; Hyperaccumulators; Metal extraction; Hydrometallurgy; Pyrometallurgy.
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Abstract
In present paper the energy consumption of the excavator and overburden linear cutting resistance by invoking the multiple linear regression was examined. As a result, the corresponding models as nonlinear functions of physical and mechanical overburden properties: grain size, unit weight, cohesion, and friction angle, were proposed. The analysis was based on records made at ”Tamnava Eastern Field” mine for the bucket-wheel excavator with new excavation teeth. The obtained results indicated that excavator energy consumption significantly depended on the grain size and cohesion, as individual factors, while the effect of two-factor interactions was particularly significant: clay percentage with cohesion and small grained sand fraction, and friction angle with medium grained sand and cohesion. On the other hand, linear cutting resistance of the overburden was largely controlled by all the examined physical and mechanical properties (grain size, unit weight, and shear strength), with the following significant two-factors interactions: shear strength parameters with all grain size fractions, different grain size fractions among each other, and friction angle with unit weight.
Key words: Cutting resistance; Energy consumption; Unit weight; Grain size; Shear strength; Multiple linear regression.
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