In-situ capturing of fluorine with CaO for accelerated defluorination roasting of lepidolite in a fluidized bed reactor

Abstract

In-situ capturing of fluorine (F) with CaO in a fluidized bed reactor is proposed to accelerate the defluorination reaction and to improve the lithium extraction from lepidolite ore. Compared to the roasting process without addition of CaO, the Li extraction efficiency is improved by ca. 15 percentage points in the present of CaO during the roasting reaction. And more than 91% of the fluorides volatilized from the lepidolite are captured by CaO particles in the fluidized bed reactor and are converted to CaF2. The formation of CaF2 on the surface of CaO particle is attributed to the generated HF from the lepidolite particles. The in-situ capturing of HF by addition of CaO changes the thermodynamic equilibrium state that benefits the defluorination reaction. Therefore, the in-situ capturing of fluorine with CaO in fluidized bed reactor is a promising method for the de-fluorinate and for the lithium extraction for versatile applications.