Abstract This study investigated the pressure leaching of lithium and other valuable metals from lepidolite using NaOH and Ca(OH)2. The findings showed that NaOH concentration, temperature, and stirring rate are the most significant process parameters. The addition of Ca(OH)2 facilitates the leaching of lithium and minimizes the concentration of silicate and fluoride in the leach liquor by forming solid phases identified as Ca3Al2Si3O12 CaF2 and NaCaHSiO4, with a loss of about 7% NaOH. The leaching efficiencies after 2 h were 94% Li, 98% K, 96% Rb, and 90% Cs under the most suitable conditions (250 °C, 320 g/L NaOH, liquid-to-solid ratio of 10, 300 rpm stirring speed, lime addition of 0.3 g/g). Precipitation of lithium as Li3PO4 by adding phosphoric acid and subsequent conversion of Li3PO4 to LiOH using Ca(OH)2 recovered 83% of lithium as LiOH allowing recycling the rest along with 93% of NaOH for leaching.

中文翻译：

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磷酸盐沉淀加石灰法浸出锂云母并从纯化的碱性加压浸出液中回收氢氧化锂

摘要 本研究调查了使用 NaOH 和 Ca(OH)2 从锂云母中压力浸出锂和其他有价值金属的过程。结果表明，NaOH 浓度、温度和搅拌速率是最重要的工艺参数。Ca(OH)2 的添加促进了锂的浸出，并通过形成被确定为 Ca3Al2Si3O12CaF2 和 NaCaHSiO4 的固相来最小化浸出液中硅酸盐和氟化物的浓度，损失约 7% NaOH。在最合适的条件下（250 °C，320 g/L NaOH，液固比为 10, 300 rpm，2 h 后的浸出效率为 94% Li、98% K、96% Rb 和 90% Cs搅拌速度，石灰添加量为 0.3 g/g）。