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.