Hydrometallurgical Recovery of Potassium from Potassium-Bearing Micas: Comparative Leaching Behavior of Biotite and Phlogopite.

Potassium-bearing mica minerals have attracted increasing attention as alternative feedstocks for fertilizer production due to their abundance in mineral resources and mining residues. This study evaluated the hydrometallurgical extraction of potassium from biotite and phlogopite through sulfuric acid leaching under ambient conditions. Biotite-rich rock from the Carajás region (Pará, Brazil) and phlogopite-rich rock from Serra da Carnaíba (Bahia, Brazil) were characterized by mineralogical and chemical analyses prior to leaching. The materials contained 9.60 wt.% and 9.26 wt.% K₂O, respectively. Leaching experiments were conducted in a 5 L rolling bottle operated at 10 rpm for 36 h at 25 °C using particles smaller than 1 mm and H₂SO₄ dosages ranging from 0.28 to 0.85 mL g⁻¹ of ore. Potassium extraction from biotite increased from 25% to 67% as acid dosage increased, whereas phlogopite exhibited significantly lower recoveries, ranging from 29% to 33%. At the highest acid dosage investigated (0.85 mL g⁻¹), sulfuric acid consumption reached 0.23 mL g⁻¹ for biotite and 0.18 mL g⁻¹ for phlogopite. The higher reactivity of biotite was attributed to its greater susceptibility to acid attack and dissolution of structural elements such as Fe, Al, and Mg. In contrast, the lower potassium recovery from phlogopite was associated with its lower leaching reactivity and the presence of refractory gangue minerals. The results demonstrate that biotite-bearing rocks represent a more promising alternative source of potassium for fertilizer production than phlogopite under low-temperature sulfuric acid leaching conditions. Furthermore, the process generates a potassium sulfate-rich solution and may provide a pathway to valorize potassium-rich mining residues and unconventional mineral resources.

Hydrometallurgical processing; Biotite

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