An environmentally friendly improved chlorination roasting process for lepidolite with reduced chlorinating agent dosage and chlorinated waste gas emission

The traditional chlorination roasting has been criticized for the large amount of chlorinated waste gas emission. In this paper, an environmentally friendly improved chlorination roasting process for lepidolite was proposed. Firstly, a series of conditional experiments were performed to optimize the parameters in the process. The extraction of lithium, potassium, rubidium, and cesium was 85.5%, 80.9%, 94.5%, and 90.2% under the optimal conditions, respectively. Calcium hydroxide was selected as the chlorine-fixing agent and the dosage of chlorinating agent was greatly reduced from 50 to 100% to 25%. Then, the phase changes of the process were clarified by characterizing the solid products after roasting and leaching. The main phases of roasting slags were determined as anorthite (Ca(Al2Si2O8)), potassium chloride (KCl), andradite (Ca3Fe2(SiO4)3), calcium fluoride (CaF2), and ferroferric oxide (Fe3O4). Only soluble KCl was dissolved in the leaching process. The chlorinated waste gas emission was absorbed and analyzed. The emission of Cl2 was effectively restrained and the total volatilization of chlorine was also greatly reduced from 80% to 20%. The improved chlorination roasting process proposed in this paper was much more environmentally friendly compared with the traditional chlorination roasting process.