2.3.4. Nitric acid decomposition of calcined borosilicate concentrate

In the next series of experiments the decomposition of pre-calcined borosilicate concentrate was studied using the reagent HNO₃. In the first series of experiments the influence of temperature on the decomposition of concentrate and extraction of oxides from its composition was studied. The decomposition temperature was varied in a wide range of values - from 20 to 100 deg C. The constants in this process were decomposition time of 60 minutes and HNO₃ concentration of 15 %. It was shown that as the temperature increased to 95 deg C, the recovery of B₂O₃, Fe₂O₃, Al₂O₃ and CaO oxides increased significantly, reaching maximum values of %, respectively: 94.6; 98.6; 83.5 and 90.4. The next series of experiments was carried out to change the decomposition duration of ore concentrate by nitric acid. The constants in this series of experiments were t=95 deg C and nitric acid concentration of 12-15 %. It is noted that at increase of time of processing of the considered concentrate by reagent - HNO₃ from 30 to 60 minutes the maximum values of extraction of oxides from the composition of concentrate are reached, making B₂O₃ - 93.9 %; Fe₂O₃ - 98.2 %; Al₂O₃ - 84.1 %; CaO - 98.2 % at 60-minute processing.