How to extract lithium from lepidolite?

15311826613

Welcome to consult Xinhai - customized mineral processing plan

Xinhai can provide you with mineral processing tests, mineral processing process and mineral processing equipment selection, mineral processing plant scheme design and construction drawing design; provide mining mineral processing equipment; provide mineral processing plant construction and equipment installation as well as mine management and operation services.

Consultation 153-1182-6613

15311826613

Click to add WeChat

Get product price

WeChat ID has been copied, add friends, and get manufacturer quotations!

In the process of lithium resource development and utilization, the processing and purification of lithium-containing minerals such as spodumene and lepidolite have long been carried out. At present, among the more than 130 known lithium-containing minerals, the processing and purification of lithium-containing minerals such as spodumene and lepidolite has long been carried out. Only a few silicate and phosphate minerals have economic value. This article takes spodumene (chain silicate) and lepidolite (layered silicate) as examples to introduce their lithium extraction technology.

How to extract lithium from lepidolite

Lepidolite, also known as lepidolite, is a layered silicate mineral with a monoclinic crystal structure. Its basic framework is two silicon-oxygen tetrahedral mesh layers filled with octahedral coordinated cations, and lithium is sandwiched between the two tetrahedral mesh layers in the form of octahedral coordination. If lithium is to be extracted from lepidolite by leaching, it is necessary to release lithium from the encapsulation structure by roasting. Lepidolite can be roasted by a variety of reagents. Currently, there are several methods, including sulfate roasting, carbonate roasting, and chloride roasting, i.e., defluorination lime pressure treatment.

1. Sulfate roasting treatment of lithium mica

As it is difficult to directly leach lithium from lithium mica, it is then leached and precipitated to extract a concentration of 1% to 2%. Concentrated sulfuric acid is used to treat the mineral at a temperature of 150 to 170°C, replacing Li+ with H+ to form Li2SO4. The digested Li2SO4 suspension is then selectively dissolved in cold water. After removing the dissolved AL by CA(OH)2 precipitation, NA2CO3 is used as a precipitant to precipitate lithium in the form of Li2CO3 at 90°C.

2. Carbonate roasting treatment of lepidolite

Lithium can also be recovered by leaching lepidolite with water after roasting with CACO₃. In this process, the mineral ground to the required particle size is roasted with CACO₃ at 1000°C until the material is completely solidified]. The melt is treated with hot water to dissolve Li, NA, Rb, CS, CA and a small amount of Fe and Mg. Therefore, impurities are removed before Li₂CO₃ precipitation, and CA is separated by precipitating CACO₃ by passing CO₂ into the solution, and neutralized with HCL to convert it into chloride.

3. Chloride roasting treatment of lepidolite

In addition to the sulfate and carbonate processes, lithium can also be extracted by leaching after chloride roasting. During calcination with sodium chloride and calcium chloride, lithium forms soluble chloride complexes such as NACL, CACL₂ and mixtures thereof.

When lepidolite and sodium chloride are calcined at a mass ratio of 1:2 and 1:1, the product combinations are LiCL, KCL, NAALSi₃O₈ and SiO₂. When CACL₂ and lepidolite are calcined at a mass ratio of 1:2, the product combinations are LiCL, KCL, NAALSi₂O₆, SiO₂, CAF₂, CASiO₃ and CAAL₂Si₂O₈. When the mass ratio of CACL₂ to lepidolite increases to 1:1, the LiALSi₂O₆ phase disappears.

Due to the incomplete diffusion of chlorine in lepidolite, the extraction efficiency in both cases is only 62%. Further roasting with a mixture of NACL and CACL₂ increases the fluidity of chloride and reduces the viscosity of the liquid phase, thereby improving the extraction rate of lithium, because the melting point of the mixture of NACL and CACL₂ is lower than that of NACL and CACL₂. Therefore, the mixed chloride roasting is easier to diffuse to the surface of lepidolite than pure NACL or CACL₂, and the extraction efficiency of Li is increased to 92.00% when maintained at 60℃ for 30min. After the leaching solution is purified under appropriate pH conditions, lithium is recovered in the form of Li₂CO₃.

4. Defluorination and lime pressure treatment of lepidolite

Lepidolite is treated with steam (H₂O) at high temperature to form LiAL(SiO₃)₂ (aluminum silicate), KALSi₂O₆ (leucite), and HF (hydrofluoric acid). During the heat treatment, H₂O dissociates into H⁺ and OH^-. H⁺ reacts with fluoride to form HF, and hydroxyl reacts with Si—O—Si bonds of lepidolite to form Si—OH groups. Si—OH groups can react with OH^- to form new phases, such as H₂O, leucite, or aluminum silicate. Under the optimal steam roasting conditions (860℃, 30ｍiN), 42.3% of fluoride can be removed from lepidolite. The steam-treated lepidolite is further pressurized with NA₂CO₃ solution at 130℃ to obtain Li with a purity of about 99%. Based on the principle that the solubility of LiOH is lower than that of other alkali metal hydroxides, LiOH is recovered in the form of salt crystals. After redissolution, CO₂ gas is introduced to generate LiHCO₃, which is heated to 90~100℃ to precipitate Li₂CO₃.