Introduction to the process steps and characteristics of lithium extraction by lepidolite acid method!

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With the rapid growth of lithium consumption and the gradual depletion of spodumene minerals, the extraction of lithium from other mineral resources has developed rapidly in recent years. Lepidolite is rich in resources and has a relatively high lithium content, making it an important ore resource for lithium extraction. In the lithium extraction process, acid lithium extraction is one of the more common processes. The following editor will introduce the process steps around these methods. and its advantages and characteristics.

Lithium extraction by acid method is mainly divided into acidification roasting, concentrated sulfuric acid normal temperature pretreatment, high temperature pretreatment and sulfuric acid based on different acid treatment methods. Several methods of pressure leaching, after acidification treatment, lithium and the associated rubidium and cesium will become soluble salts.

1. High-temperature pretreatment lithium extraction method

The fluorine-containing tail gas produced by high-temperature acid treatment has a great impact on the environment and requires strict adsorption treatment procedures. Lithium, potassium, rubidium and cesium all have high leaching rates in the water leaching process. Under optimized conditions, the lithium leaching rate is more than 90%. The composition of the immersion liquid is complex, the amount of residual acid is large, and it is difficult to extract lithium and other valuable elements. In particular, the Al₂O₃ content in lepidolite is as high as 28%, and a large amount of aluminum enters the solution. Neutralization and aluminum removal after immersion produces a large amount of waste residue that is difficult to process and causes serious loss of lithium. Therefore, it is difficult to purify lepidolite infusion by sulfuric acid method, the overall yield of lithium is low, and the silicon-aluminum slag produced is difficult to utilize. There are currently no industrial application examples.

2. Lithium extraction method by acidification roasting

Lepidolite is obtained by acidification roasting and water leaching to obtain Li and a large amount of Al The sulfate leaching solution is concentrated and crystallized to obtain potassium aluminum sulfate alum, and part of Li₂CO₃ is recovered from the concentrated solution. After filtration, add lime to the filtrate and alum aqueous solution respectively to obtain aluminum-containing gypsum slag. React and dissolve gypsum slag with NaOH solution to obtain lithium and Al(OH)_{3 solution. After filtration, concentrate to obtain crystallized Al(OH)3, and add Na3PO4 to the concentrated solution to Li3 Sub>PO4 precipitates to further recover lithium. The filtrate is added with lime to remove PO4^3- and can be recycled as alkali liquid.}

The effective recovery and separation of lithium and aluminum is achieved, and the associated rubidium and cesium are simultaneously recovered in the process, providing an effective way for the efficient and comprehensive utilization of lepidolite.

New acid process for extracting lithium from lepidolite by treating lepidolite with sulfuric acid and hydrofluoric acid. The main steps are:

1. Mix lepidolite, fluorosilicic acid and sulfuric acid in proportion and react at 120°C;

2. The reactants are calcined at 250°C for defluorination;

3. Water leaching to obtain a variety of sulfate leaching solutions (Li₂SO₄, Al₂(SO< sub>4)₃, K₂SO₄);

4. Immersion cooling crystallization Potassium aluminum alum with added value is obtained, while Li₂SO₄ remains in the filtrate;

5. Add (NH₄)₂SO₄Second formation of vitriol to remove aluminum;

6. The purification liquid is evaporated and concentrated, and carbonized to precipitate lithium carbonate.

The addition of fluorosilicic acid can increase the yields of aluminum and lithium to more than 80% and 90% respectively. The obtained potassium alum and ammonium alum can be used as raw materials for the production of aluminum hydroxide, compound fertilizer, etc. to reduce the comprehensive cost of lithium extraction. The fluorine-containing gas generated in the calcined defluorination section enters the absorption tower and is absorbed by water and alkali classification, thus avoiding environmental pollution.

The above mainly introduces the disadvantages and improvement plans of acid extraction of lithium. In the actual mineral processing plant, for any lithium ore beneficiation, ore dressing test analysis is required, and a suitable lithium ore beneficiation process is designed and customized through analysis Only by using this method can we obtain higher lithium concentrate and achieve efficient return on investment.