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As the core strategic metal of the new energy industry, the extraction process of lithium is of great significance in modern industry. With the growing demand for lithium resources, extraction technology is also constantly improving. The following are several main processes for extracting metallic lithium:
The sulfuric acid method is one of the most mature methods for extracting lithium, mainly used to treat spodumene ore. This method roasts the ore at high temperature to change its structure from dense to loose, then mixes it with excess sulfuric acid after ball milling, roasts and dissolves it at 250°C in a rotary kiln, and obtains a crude lithium sulfate solution after water leaching. After purification, lithium precipitation, and evaporation concentration, lithium carbonate products are obtained.
The limestone roasting method is the oldest method for extracting lithium from ores. Limestone and lithium ore are ball-milled and mixed in a ball mill at a weight ratio of 3:1, and then roasted at 800-900℃ to obtain clinker. The clinker is then quenched with water, finely ground, leached, filtered or centrifuged to obtain leachate and residue. The leachate is evaporated, crystallized and centrifuged to obtain monohydrate lithium hydroxide, or prepared by CO2 carbonation to prepare lithium carbonate.
The sulfate method is often used to treat silicate minerals. By mixing α spodumene with potassium sulfate and roasting, the lithium in the ore is replaced with soluble lithium sulfate, which is leached with 10% dilute sulfuric acid. The leachate is purified and precipitated to obtain lithium carbonate. This method has low roasting temperature, short roasting time, high lithium concentration in the leachate, and low energy consumption, but it consumes a lot of potassium salt.
This process mixes spodumene and sodium carbonate solution, strengthens lithium leaching at a certain temperature and pressure, uses Na to replace Li, and then introduces CO2 into the water leaching slurry to convert lithium carbonate into LiHCO3 with higher solubility. After separating the residue, the solution is heated to precipitate lithium carbonate products.
The thermal cracking method, also known as the thermal crushing method, is suitable for processing spodumene containing non-albite, calcite and mica. Roasting at a certain high temperature converts lithium minerals from the original α-type to β-type lithium ore, while the gangue minerals remain unchanged, thereby obtaining lithium ore. The process is: crush the mineral to 50~20mm and then sieve it. The ore larger than 0.3mm is roasted at 1000~1200℃ for 1~2h, and then cooled and selectively ground, graded and purified. Lithium ore smaller than 0.3mm can be extracted from spodumene by combined separation technology.
The combined beneficiation method is mainly used to select poor and fine lithium minerals. When a single method cannot obtain qualified lithium concentrate, a combined method is required to obtain higher quality lithium concentrate. The main processes are: flotation-magnetic separation process, flotation-gravity separation-magnetic separation process, etc.
The chemical beneficiation method is mostly used to treat salt lake lithium minerals and extract lithium from brine. Its methods include precipitation, extraction, ion exchange adsorption, carbonization, calcination leaching, Xu's method and electrodialysis.
The potential regulation flotation process affects the floatability of the ore by adjusting the electrochemical characteristics of the ore pulp to achieve the effect of improving the flotation performance. By controlling the electrochemical conditions in the lead-zinc ore pulp, the substances that react with the collector and the surface of the sulfide ore are changed to achieve the selective flotation of the sulfide ore. This process has the characteristics of low reagent consumption and low pollution, but the potential is difficult to control and is not widely used in industry.
The primary potential control flotation process uses the redox-active substances in the pulp flotation system of sulfide ores to improve the flotation effect by changing the flotation conditions and utilizing the redox-active properties of their own electrochemical reactions. This technology can guide the selection of complex polymetallic sulfide ores, especially the actual production of other ores containing associated precious metals such as copper, lead, zinc, sulfide and iron, and can enhance the recovery of metal resources and achieve comprehensive utilization.
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