Extraction of lithium from lepidolite by sulfation roasting and water leaching

Sulfation roasting followed by water leaching process was used to extract lithium from lepidolite. Various parameters including roasting temperature, the amount of additions, and solid/liquid ratio in leaching process were optimized. The lithium extraction efficiency of 91.61% could be reached with a mass ratio of lepidolite/Na₂SO₄/K₂SO₄/CaO of 1:0.5:0.1:0.1, and roasting at 850 °C for 0.5 h. XRD analysis showed that sulfation roasting caused the decompositions of the original aluminosilicate to NaSi₃AlO₈, KAlSi₂O₆ and CaAl₂Si₂O₈. The phases of CaF₂ and Ca₄Si₂O₇F₂ are observed due to the addition of CaO.