Critically analyze current non-waste technologies in production of rare metals.
Waste-free technology - a system of technological, technical, economic and organizational measures directed at maximum utilization of mineral resources, which provides complex processing of raw materials and disposal of waste in order to produce more products.
Example. The diagram shows a waste-free processing of copper-nickel sulfide ores by pyrometallurgical method.
Analyze and choose extraction methods of obtaining of rare metals.
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. Example:
Purification of beryllium
Can obtained by extraction of beryllium with a very high degree of purity. The extractant is acetylacetone:
When extraction takes place keto-enol rearrangement. Ketone in enol form is reacted with beryllium by cation exchange mechanism. Beryllium cation replaces the hydrogen in the - OH group. Be (OH) 2 is dissolved in a mixture of acetylacetone - carbon tetrachloride. Thus beryllium forms acetylacetonate which is dissolved in CCl4. The resulting organic solution washed with water and then contacted several times with an aqueous solution saturated with EDTA, which complexed ions in solution such as Ca2 +, Al3 +, S2 +, Fe3 +, Mg2 + and Cu2 +. Beryllium is purified from the organic phase reextracted with nitric acid. From this ammonia solution precipitated beryllium hydroxide, which is then sintering to BeO. In the resulting beryllium oxide, 10-6%: Ca <10, Al <10, Si <10, Fe <5, Mg <5, Cu <5.
It is best to extracted beryllium with solution of 1- (3-ethyl-butyl)-4-ethylmethylamine in CCl4. When using 0.3 M ammonium beryllium distribution coefficient reaches 20.
Analyze and choose ion exchange methods of obtaining of rare metals.
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.
Organic cation exchangers are insoluble substances, which are strongly related acid groups (sulfo, carboxyl, OH-group of phenols, phosphine, etc.) In the composition of the anion exchange resins are basic groups (e.g. amino group) which can form a salt when interacting with acids. Hydrogen ions or metal ions of cation and anions, included in the anion exchange resin, are exchanged for the cations or anions of a solution.
The separation of strontium-90
For separation of Y-90 and Sr-90 mixture is passed through the anion exchanger in the Oh form. When Y-90 is deposited, and Sr-90 washed with water.
After sorption on the cation Sr and Ca to carry out desorption with EDTA (0.01 M) with pH=7,4. The strontium is eluted first. The use of EDTA for elution allows clearly divided alkaline earth and rare earth elements.
A clear separation is achieved by elution of alkaline-earth elements from the sulphocationite with a solution of ammonium citrate.
It is established that strontium is well sorbed sodium molecular sieve is an artificial aluminosilicate type 4A.