Abstract A new crystallization-precipitation method is proposed to extract lithium from salt-lake brine with high Mg Li mass ratio (Mg Li > 40). A closed loop path for carnallite crystallization is established and a high magnesium removal efficiency is achieved via MgHPO4(S) precipitation through thermodynamic analysis and experiments. In the first stage, KCl is added into the brine to remove about 50% of magnesium by forming carnallite. When the amount of KCl is 55.9% of stoichiometric requirement and further evaporation at 17.6%, the removal efficiency of total magnesium is 53.1% and the loss of lithium is 5.4%. In the second stage, residual magnesium in the brine is further removed by forming MgHPO4(s). With the amount of Na2HPO4 at stoichiometric requirement, reaction temperature 40 °C, reaction time 30 mins and aging time 3 h, the removal efficiency of residual magnesium is 99.2% and the recovery of residual lithium is 98.5%. To sum up, the total removal efficiency of magnesium is 99.6% and the recovery of lithium is 93.2%. In addition, KCl and Na2HPO4 used in this method can be recycled, which will significantly reduce the cost.

中文翻译：

---

结晶-沉淀法从高镁锂比卤水中提取锂

摘要 提出了一种从高镁锂质量比（Mg Li > 40）盐湖卤水中提取锂的结晶沉淀法。通过热力学分析和实验，建立了光卤石结晶的闭环路径，并通过MgHPO4(S)沉淀实现了高脱镁效率。在第一阶段，将氯化钾加入盐水中，通过形成光卤石去除约 50% 的镁。当KCl量为化学计量要求的55.9%，进一步蒸发17.6%时，总镁去除率为53.1%，锂损失为5.4%。在第二阶段，通过形成 MgHPO4(s) 进一步去除盐水中的残留镁。以化学计量要求的 Na2HPO4 量，反应温度 40 ℃，反应时间 30 分钟，老化时间 3 小时，残镁去除率99.2%，残锂回收率98.5%。综上所述，镁的总去除率为99.6%，锂的回收率为93.2%。此外，该方法使用的KCl和Na2HPO4可以回收利用，大大降低了成本。