This study investigated alkali metal extraction from zinnwaldite using chlorination roasting with CaCl2 and CaCO3. It was found that increasing the ratio of CaCO3 and zinnwaldite in the roasting mixture up to 3:1 significantly increased the efficiency of alkali metal extraction. The reactions in roasting mixture components occurred below 500 °C on the surface of zinnwaldite particles. Decomposition of zinnwaldite and CaCO3 began around 600 °C, leading to the formation of new CaO-SiO2-based phases. The maximal extraction of 96 % of Li, 96 % of K, and 100 % of Rb was achieved at 850 °C when the mixture of CaCO3/zinnwaldite at the ratio of 4:1 was used with significant volatilization of alkali metal chlorides. The formation of an amorphous glass phase associated with compaction of material above 850 °C did not affect the extraction of K and Rb, but it considerably constrained the extraction of Li due to immobilization of its ions in the glassy matrix. The additional limiting factor for Li extraction was the binding of chlorine in stable phases. Adding CaCO3 to the roasting mixture was found to prevent the release of HCl, HF or Cl2 during roasting. Li2CO3 was precipitated from leachate prepared from sinters obtained under the optimal sintering conditions and subsequently recrystallized from demineralized water, achieving battery grade purity of 99.80 %.

中文翻译：

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用 CaCl2 和 CaCO3 对锌瓦石进行氯化焙烧，以提取 Li、K 和 Rb

本研究研究了使用 CaCl2 和 CaCO3 氯化焙烧从 zinnwaldite 中提取碱金属。研究发现，将焙烧混合物中 CaCO3 和 zinnwaldite 的比例提高到 3：1 可显著提高碱金属提取的效率。焙烧混合物组分的反应发生在 500 °C 以下的锌瓦石颗粒表面。锌矿和 CaCO3 的分解开始于 600 °C 左右，导致形成新的 CaO-SiO2 基相。当 CaCO3/锌锌矿的混合物以 4：1 的比例使用，碱金属氯化物显着挥发时，在 850 °C 时实现了 96% 的 Li、96% 的 K 和 100% 的 Rb 的最大提取。与 850 °C 以上的材料压实相关的非晶状玻璃相的形成不会影响 K 和 Rb 的提取，但由于其离子固定在玻璃基体中，它大大限制了 Li 的提取。Li 萃取的另一个限制因素是氯在稳定相中的结合。发现在烘焙混合物中添加 CaCO3 可以防止烘焙过程中释放 HCl、HF 或 Cl2。Li2CO3 从在最佳烧结条件下获得的烧结矿制备的渗滤液中沉淀出来，然后从软化水中再结晶，达到 99.80% 的电池级纯度。