3.4.2. Sintering of green clays of Chashma-Sang Deposit with sodium hydroxide followed by aqueous sulfuric acid decomposition

The technological aspects of processing of kaolin-containing raw materials - green clays of Chashma-Sang Deposit of the Republic of Tajikistan have been studied, the optimal parameters for the extraction of alumina and iron oxides have been determined at sintering of green clays with sodium hydroxide and further water-sulfuric acid decomposition of raw materials. Preliminary results of elemental and flame photometric analyzes show that the composition of green clays includes (wt %): Al₂O₃ - 20.38; Fe₂O₃ - 11.97; SiO₂ - 51.3; Na₂O - 1.0; K₂O - 2.45; Ca O - 0.5; Mg O - 1.0. The extraction rate of Fe₂O₃ and Al₂O₃ into solution during sulfuric acid decomposition of green clay has been studied depending on process temperature in the range of 20-98 deg C, the duration of treatment in the range of 15-60 minutes and the concentration of sulfuric acid in the range of 20-96.5%. As a result of conducted research on sulfuric acid decomposition of green clays of Chashma-Sang Deposit of the Republic of Tajikistan, the optimal conditions for the extraction of aluminum and iron salts from the composition of green clays have been determined and their mineralogical composition has been established. A flowsheet for the processing of green clay of Chashma-Sang Deposit by sintering with sodium hydroxide and subsequent aqueous-sulfuric acid decomposition has been developed.