Critically evaluate of methods of purification to obtain pure rare metals.
Obligatory stage of technology is the production of pure chemical compounds, rare metal separation from accompany it impurities. To solve this problem is widely used extraction, ion exchange, distillation and other methods. From pure chemical compounds by electrolysis and metallothermy obtain metal.
For the technology of rare metals are characterized by the need for refining the resulting metal. To this end, widely used vacuum distillation, iodide refining, crystallographic methods of cleaning, etc.
One of the main limits is to obtain compact and alloy ingots in a convenient form for the subsequent machining, producing semi-finished or finished products.
In technology of rare elements ion-exchange chromatography has proved particularly useful when splitting a large group of chemically similar rare earth metals. It is possible to identify four main areas of application of ion exchange in hydrometallurgy: 1) the enrichment and concentration; 2) separation; 3)purification; 4)the disposal of effluent.
Extraction methods in the technology of rare metals used for purification and for separation of similar properties of rare elements. Application of extraction allows for the continuous of high-performance process, it is easy to control and automation.
Metallothermy - a process of recovery of metals from their compounds with other metals, are chemically more active at high temperature. Sometimes here also includes non-metals recovery processes.
Metallothermic reduction reaction can be represented by the equation, wherein X - anion, ∆Н - thermal effect
Electrolysis is one of the main methods of obtaining rare metals, alloys and refining the crude metal.
Electrolysis is the decomposition of the electrolyte by a constant electric current, which is accompanied by the formation of new substances. On the electrodes occur the oxidation reaction – recovery: the anions at the anode give up electrons and are oxidized and the cations are recovered at the cathode.
45. Evaluate the current problems in mineral processing technologies in Kazakhstan.
Environmental problems in the area of operation of the mining and mineral processing and metallurgical industries
Mining companies are among the largest consumers of natural resources and environmental pollutants. Wastes from mining and processing and metallurgical industries occupy large areas and are a source of environmental risk due to the ingress of harmful components in the atmosphere, soil and water. In this regard, the problems of environmental protection and safe life in GOKov coverage area acquired multi-faceted nature, affect the interests of hundreds of thousands of people, production and nature in general.
For long period of intensive development of mining and metallurgical complex of the total amount of accumulated waste in the steel industry of Kazakhstan (iron ore, manganese ore and hromovorudnaya industry) is more than 6.2 billion tons, of which:. Oilfield extraction and stripping - 92.8% enrichment - 6 , 1% and metallurgical - 1.1%. The area of land occupied by the waste - more than 15 thousand hectares.
The bulk of the waste mining and metallurgical complex is formed on the non-ferrous metallurgy enterprises. When the extraction and processing of non-ferrous metals to produce a final product of 2% of ore is processed into marketable products, the remaining 98% goes to waste dumps and HVO-stohranilischa. And to produce 1 tonne of copper recycled 100 tons of commercial ore; to produce 1 tonne of salable lead ore is necessary to produce 3 tons of ore raw materials. Waste is waste rock, tailings and waste products of mining and metallurgical enterprises
An open way to develop as the most economical and efficient for the extraction of ferrous and non-ferrous metals, and continues to evolve in the near future we should expect an increase in the depth of the large quarries Kazakhstan. This will lead to the deterioration of natural ventilation and working conditions of miners in deep horizons, enhance the impact of industry on the environment in the area of operations of mining companies. The fact that the open mining of ore deposits associated with impaired ground. In the area of land allotment has an open mine workings, tailings commitments and overburden, tailings and sludge storage, transport communications and other industrial facilities. At the open development of mineral deposits, in addition to long-term alienation of land, land damage occur, the violation of the hydrogeological regime areas, air pollution with dust and gases, poisoning the flora and fauna of toxic substances, the deterioration of sanitary conditions in the region of field development.
When the process of ore mining operations in underground mines following the production of waste is generated:
rock formed in the conduct of mining operations;
technological waste;
scrap metal (black and color);
process water, which is formed in the conduct of technological operations (drilling holes, wells, irrigation of the rock mass, mining and others.), and ground water released by the outcrop of rocks;
harmful gases during blasting operations and on internal combustion engines of self-propelled equipment;
dust emissions in the atmosphere by vozduhovydayuschim trunks;
emissions of dust from cement concrete-stowing complexes . The most negative impact on the environment has issued and stockpiled on surface waste rock from the tunnel works.
There is now about 320 million tons of waste, and more than 50 million tons of gold mining enterprises of Kazakhstan impounded at gold extraction plants [4..; 3]. It's only in the Semipalatinsk Irtysh region there are more than 10 mining companies in gold mining, which together cause great harm to the environment. The largest of these include: Bakyrchik, Jean, Central Mukur, Suzdal, Miyaly, Zherek.