Study On Extraction Of High Purity Lithium Chloride By Freezing-adsorption From Brines Of Salt Lakes

Lithium chloride is an importance raw material, which is widely used in many fields such as energy sources, metallurgy, biology, medicine, etc. In order to reduce the cost of preparation, the thesis gives the method of direct extraction of high purity lithium chloride from the abundant resources of Qinghai salt lakes. In the experiments, The freezing-adsorption method was adopted to directly prepare high purity lithium chloride from salt lakes brines based on previous studies. What's more, the analysis of lithium chloride and each ion in the process are also studied.The thesis reviewed the extraction of lithium chloride from salt lakes home and abroad and studied on evaporation of brines and freezing process conditions which is used to separate NaCl from LiCl solution. After the sorbent Li_1.4Al_0.2Cr_0.2Ti_1.6(PO₄)₃ and Li_1.3Al_0.3Ti_1.7(PO₄)₃ were prepared, the investigation of the adsorption property and effect was firstly performed. Next, the regeneration mechanism was studied by using FT-IR, Raman, X-ray methods. High pure lithium chloride was prepared and the optimum process conditions were found. Results are as follows:1. The material brines were evaporated in two steps, LAS/ASC could not only reduce the loss rate of lithium chloride but also increase the particle size of sodium chloride. Through orthogonal analysis, optimum freezing conditions were determined as: -15℃of temperature, 5h of freezing duration and 0.5% (NH₃·H₂O to LiCl solution weight ratio) of dosage, under which the Na content in LiCl was 0.0991%.2. The optimum adsorption conditions are as follows: 3μm1.4Al_0.2Cr_0.2Ti_1.6(PO₄)₃ was 33.13mg/g. HCl was better than HNO3 for sorbent regeneration. FT-IR, Raman, X-ray methods showed: Li_1.4Al_0.2Cr_0.2Ti_1.6(PO₄)₃ transforms to Na_1.4Al_0.2Cr_0.2Ti_1.6(PO₄)₃ after adsorption.3. The specifications of the product were 99.85% LiCl, 0.0025% Na⁺, 0.0019% K⁺, 0.0017% Ca²⁺, whereas Fe²⁺, Mg²⁺, Cr³⁺ and Zn²⁺ were not detected. Flame atomicemission spectrometry (FAES) was better than flame atomic absorption spectrometry (FAAS) for determining Li⁺ and Na⁺ contents, whereas FAAS was better than FAES for determining Ca²⁺ and Mg²⁺ contents.