The recovery of potassium oxide and alumina from alunite concentrate

The novel recovery process of potassium oxide and alumina from alunite concentrate was studied under different conditions, and the key technology of this process was the combination of high-temperature reductive calcination and low-temperature Bayer process. Results showed that high-temperature reductive desulfurization achieved efficient removal of sulfur in potassium aluminum sulfate, and it also accomplished the selective leaching of aluminum and potassium on the premise that the alkaline-digesting properties of alumina was kept. The desulfurization degree reached 75%, and almost all of aluminum potassium sulfate was decomposed in desulfurization process. The leaching rate of potassium oxide was 86% in hydro-leaching procedure. The digestion rate of alumina in hydro-leaching residues reached 80% as a Na2Ok of 140 g/L, a temperature of 150 °C, and a solid-liquid ratio of 1: 6 after 60 min in low-temperature Bayer process.