The sulfuric acid method (пишите любо текс, либо рисуйте схему)
The method is based on the reaction between sulfuric acid and ß-spodumene (there is virtually no interaction between ɤ-spodumene and sulfuric acid) in which the hydrogen of the acid is substituted for the lithium without a change in the structure of the mineral:
After the enrichment (by decrepitation) the cooled and crushed (in a roller mill, to a particle size of -0.074") material is fed to a horizontal screw-conveyer or rollers in which it is mixed with concentrated (9370) sulfuric acid by a sprinkling technique.
The sinter formed is cooled and leached with water to extract the Li2S04. The solution is separated by filtration on a drum-type vacuum filter and the magnesium and calcium are removed from the solution by precipitation, respectively, as magnesium hydroxide and calcium carbonate. The iron and aluminum are precipitated as the hydroxides by adding sulfuric acid to the solution (to pH 7) together with a small amount of carbon black,
The solution is filtered and lithium carbonate is precipitated by the addition of a saturated solution of sodium carbonate. The lithium carbonate is washed twice with deionized water yielding a product with a carbonate content of 96 to 97%. The precipitate is separated by centrifuging, and dried at a reduced pressure .The dry lithium carbonate is contaminated with sulfate ions, chloride ions, the oxides of sodium, potassium, iron, calcium, and the heavy metals, and contains 0.01 % moisture.
27. Create a modern technological scheme of processing of mineral raw materials containing beryllium.
The average concentration of beryllium in the Earth's crust is 6*10-4. There are more than 30 known beryllium minerals; the most common are beryl, chrysoberyl, phenacite, helvite, danalite, and bertrandite. Beryl is the main commercial beryllium mineral, but phenacite and helvite are also of commercial value. The main beryllium ore deposits are found in Brazil, Argentina, Congo (Leopoldville), India, Southern Rhodesia, Australia,and the USA (South Dakota and California). All these deposits contain mostly beryl. The largest phenacite and helvite deposits are in Norway.
Two industrial methods for the decomposition of beryl are used at present: the fluoride method and the sulfate method.
Sulfate process, h2so4
Alkaline treatment
Be3Al2(Si6O18) + 7CaO = 3CaBeSiO4 + CaO·Al2O3 + 3CaSiO3
CaBeSiO4 = BeO + CaSiO3
Heat treatment
Beryl is melted (1650 °C) and quenched in water. After treatment 50-60 % beryl has a greater solubility in H2SO4 heat treatment renders of 90-95 % of the beryl soluble.
Leaching with water
Filtration SiO2
Separation, alum separation, chelate separation, (NH4)2CO3 separation
Hydrolysis
Drying Be(OH)2
BeSO4 + 4 NaOH = Na2BeO2 + Na2SO4 + 2H2O
Na2BeO2 + 2H2O = Be(OH)2 + 2NaOH
30. Critically evaluate modern technology in the processing of rubidium and cesium containing rare metal raw materials.
Cesium is found in the minerals pollucite and lepidolite. Pollucite is found in great quantities at Bernic Lake, Manitoba, Canada and in the USA, and from this source the element can be prepared. Most commercial production is as a by-product of lithium production.