摘要
The fluorine-based chemical method shows great potential in leaching lithium(Li) from lepidolite. Leaching kinetics of Li in a mixture of sulfuric acid and hydrofluoric acid, which is a typical lixivant for the fluorine-based chemical method, was carried out under crucial factors such as different HF/ore ratios(1:1-3:1 g/mL) and leaching temperatures(50-85℃). The kinetics data fit well with the developed shrinking-core model, indicating that the leaching rate of Li was controlled by the chemical reaction and inner diffusion at the beginning of leaching(0-30 min) as a calculated apparent activation energy(Ea) of 20.62 kJ/mol. The inner diffusion became the rate-limiting step as the leaching continues(60-180 min). Moreover, effects of HF/ore ratio and leaching temperature on selective leaching behavior of Li, Al and Si were discussed. 90% of fluorine mainly existed as HF/F-in leaching solution, which can provide theoretical guidance for further removal or recovery of F.
锂云母混酸HF/H2SO4浸出动力学研究表明:50~85℃下锂浸出速率在浸出前期(0~30 min)由表面化学反应以及内扩散共同控制,表观活化能Ea为20.62 kJ/mol;浸出后期(60~180 min)则主要由产物内扩散控制。氢氟酸添加量相比浸出温度对Li、Al和Si的浸出速率影响更显著。浸出温度对Li浸出效率影响比对Al和Si的影响更明显。F元素在固相不溶渣中的存在形式则主要为Al-F不溶氟化物和K2SiF6。此外,液相中F元素在所研究的氢氟酸添加量及浸出温度下均可保持较高保留率(>90%),为F元素的高效利用及后续回收利用提供保障。
基金
Project(51474237)supported by the National Natural Science Foundation of China
