Brown corundum fly ash (BCFA) is a solid waste from the brown corundum smelting process that contains abundant Ga, K, Si, and Al, but effectively extracting Ga can be challenging since most of it is located inside the particles. This study proposes a comprehensive utilization method of BCFA that combines hydrothermal leaching and alkali regeneration to extract Ga efficiently while producing silica-potassium compound fertilizer (SPCF) and zeolite F. By utilizing the transformation of phase and structure in the hydrothermal leaching process, Ga extraction is efficiently achieved. The results showed that under the conditions of 210 g/L KOH concentration, a liquidsolid ratio of 25 mL/g, and 160 °C hydrothermal leaching for 60 min, the extraction efficiencies of Ga, K, and Si were 95.91 %, 51.78 %, and 69.57 %, respectively. The solid product's effective SiO2 and K2O contents increased to 24.72 wt% and 17.74 wt%, respectively, which can be further used as SPCF for agricultural production. The hydrothermal leaching solution was regenerated by adjusting the Al/Si molar ratio and crystalizing at 160 °C for 24 h. The Si was recovered in the form of high value-added zeolite F, with only a 3.60 % loss of Ga.
Keywords: Alkali regeneration; Hydrothermal leaching; Partial recrystallization; Phase transformation.
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