含锂矿物机械化学强化提锂工艺

Technology of lithium extraction from lepidolite through mechanochemistry activation

采用机械化学活化方法,在机械活化过程中用K2SO4为活化添加剂,强化锂云母中惰性Li-O配位结构活化转型,通过温和稀酸浸出高效分离锂,考察了活化过程添加剂用量、球磨时间和球料比及浸出条件如酸浓度、液固比、搅拌速度、温度和时间等对锂回收率的影响,确定了最佳工艺条件,讨论了反应过程机理。结果表明,机械化学活化强化破坏云母片层结构中的Si-O-K结构,降低了Si-O配位结构对Li-O配位结构的牵制力,导致Li-O键强减弱,反应活性增加。在最优条件下(精矿与K2SO4质量比5:1、球磨机转速500 r/min、球料质量比20:1、球磨时间3 h、硫酸浓度15vol%、液固比4 L/g、反应温度80℃、浸出搅拌速率200 r/min),锂浸出率可达99.1%。

The demand for lithium resources has increased significantly in recent years due to the rapid development of hybrid electric vehicles, plug-in-vehicles and so on. To alleviate the shortage of lithium resources in China, the lithium extraction from lithium-containing minerals has received widely attention. As an important lithium-containing minerals, lepidolite has a stable mineral structure. Therefore, it is difficult to extract valuable metals from lepidolite efficiently. Based on the understanding of the stable mineral structure of lepidolite, direct leaching lithium from minerals with dilute sulfuric acid and limestone calcination-sulfuric acid leaching method are adopted to realize the activation and separation oflithium from minerals. However, the extraction of lithium by these methods are complicated, besides, the comsumption of medium is great, and a large amount of residues and waste water are produced during these processes. In this paper, the mechanochemical activation was introduced to activate the transformation of inert Li-O coordination structure in lepidolite under the condition of K2 SO4 as an additive, then dilute acid was used to achieve efficient separation of lithium. Various parameters including type and amount of additive, milling time and ball-to-concentrate mass ratio in the mechanochemical activation process as well as the acid concentration, liquid-to-solid ratio, stirring speed, temperature and time in the leaching process were optimized and the mechanism was further discussed. The results showed that the mechanochemical process destroyed the structure of Si-O-K and reduced the effect of the Si-O coordination on the Li-O coordination structure, resulted in a decrease in the Li-O bond strength and an increase in its reactivity. Under the optimum conditions(lepidolit-to-additive mass ratio 5:1, ball mill speed 500 r/min, ball-toconcentrate mass ratio 20:1, ball milling time 3 h, sulfuric concentration 15 vol%, liquid-to-solid ratio 4 L/g, temperature 80 ℃ and stirring speed 200 r/min), the leaching rate of Li was 99.1%. With this research, it is expected to provide a new approach for short range extraction and efficient utilization of lepidolite.