Study of the process of leaching of aluminum oxide from kaolin clays of the angren deposit

STUDY OF THE PROCESS OF LEACHING OF ALUMINUM OXIDE FROM KAOLIN CLAYS OF THE ANGREN DEPOSIT


Olimzhanov I.A., Nabiev U.I., M.E.Kenzhaev
Tashkent Institute of Chemical Technology

In terms of production, aluminum ranks first among non-ferrous metals. Aluminum is obtained from alumina, also called alumina. Alumina production is based on the use of high quality bauxites. Most (about 90%) of alumina is sent in small batches to enterprises in the chemical, refractory and a number of other industries.

production of aluminum and alumina in Uzbekistan , although there are kaolin clays, alunite rocks, substandard bauxite and coal ash to organize the production of alumina . The Angren kaolin deposit is the most developed . The total reserves of kaolin clay are more than one billion tons.
Known methods for producing alumina - alkaline and electrolytic for the conditions of our country are not acceptable at present. Of the acid processing methods, the nitric acid method is preferred, since its production is waste-free. With the hydrochloric acid method of processing, a large amount of ammonium chloride is formed, for which there is no demand, and sulfuric acid is a scarce product of large chemistry.
The great demand for alumina, the lack of an acceptable technology for processing kaolin clays makes the problem of obtaining alumina one of the most urgent. For studies of nitric acid leaching of aluminum oxide, three types of kaolin clay samples were used - unfired initial, fired at 6 5 0-700 ° C and enriched. Unfired clay contains on average (wt.%): SiO ₂ - 57.57; A l ₂ O ₃ - 17.66; F e ₂ O ₃ - 4.17; CaO - 2.10; S O ₃ - 1.25. The enriched clay contains 37.78% A l ₂ O ₃ ; 53.57% SiO ₂ , 0.43 F e ₂ O ₃ . Spectral analysis also showed the presence of compounds of potassium, sodium, calcium, magnesium. The remaining elements present in kaolin are hundredths and thousandths.
In order to study the processes occurring during the leaching of kaolin clays, studies of equilibrium states in the systems А l ₂ О ₃ - N ₂ O ₅ - Н ₂ O , F e ₂ О ₃ - N ₂ O ₅ - Н ₂ О, F e ₂ O ₃ - A1 ₂ O ₃ - N ₂ O ₅ - H ₂ O at temperatures of 160-200 ° C.
It has been established that impurities of combined potassium and calcium, regardless of their quantity and norm, completely pass into solution and significantly affect the insolubility of aluminum and iron. When the content of potassium and calcium in the original clay is from 0.3 to 1.2%, the concentration of aluminum in the solution practically does not change, and iron decreases. The degree of extraction of aluminum is very low and does not exceed 25%. Studies on the effect of the rate of nitric acid on the process of leaching aluminum oxide showed that reducing the rate of acid below 100% of stoichiometry leads to a decrease in the aluminum content in the solution and its degree of extraction.