Abstract: In order to recover lithium from cryptoexploded breccia tube type lepidolite ores effectively,roasting-leaching process was used to extract lithium,and a comparative study was carried out with lithium extraction from granite type lepidolite. The optimal lithium leaching conditions were obtained by L9(33) orthogonal experiments,and the factors affecting the lithium leaching rate and the lithium leaching mechanism were explored. The results show that under the conditions of sulfuric acid mass fraction of 15%,liquid-solid ratio of 4 mL/ g and roasting time of 4 h,the optimal leaching conditions for lithium from breccia tube type lepidolite are roasting temperature of 450 ℃,reaction time of 4 h and leaching temperature of 200 ℃. The optimum conditions for leaching lithium from granite type lepidolite are roasting temperature of 900 ℃,reaction time of 4 h and leaching temperature of 200 ℃. Under the optimal conditions,the leaching rates of lithium were 99. 65% and 94. 11%,respectively. The influence degree of different factors on the leaching rate of lithium is in order of leaching temperature,roasting temperature and reaction time. It was further found that the structure of lepidolite in the sample is destroyed during the roastingleaching process,and the lithium is converted into soluble sulfate and diffused into the solution. Meanwhile,hydrogen ions in sulfuric acid can be substituted more easily for lithium ions and other metal ions in lepidolite structure after roasting at high temperature,and lithium leaching rate can be effectively increased. Due to the fluorine-containing minerals such as fluorite and topaz in the breccia tube lepidolite,when it is roasted at an appropriate temperature (450 ℃) and then leached,fluorine and H+ can react to destroy its structure,which is conducive to the dissolution of lithium. Granite type lepidolite requires roasting at high temperature (900 ℃) to dehydroxy,so that the lithium in its structure can be easily replaced with H+ ,so as to obtain a higher lithium leaching rate. The roasting and leaching process uses a lower concentration of sulfuric acid,which is less corrosive to the equipment,and the process is simple and efficient with superiority.

Key words: lepidolite,lithium,sulfuric acid,roasting and leaching process,orthogonal experiments