Technical Routes for Lithium Extraction from Lithium Mica

Lithium mica is one of the key sources of lithium. The lithium extraction process typically involves first using flotation to concentrate the ore into a lithium mica concentrate, followed by the use of acid, alkali, salt or pressure leaching processes to convert the lithium into soluble lithium salts, ultimately yielding products such as lithium carbonate.

I. Flotation Enrichment

Raw lithium mica ore has a low grade and is closely associated with gangue minerals such as quartz and feldspar; consequently, flotation is commonly employed in industry for pre-enrichment. By adding collectors and modifiers under specific pulp pH conditions, lithium mica is made hydrophobic and floats to the surface, separating it from the hydrophilic gangue minerals to yield lithium mica concentrate. To improve the separation efficiency of fine-grained lithium mica, a combination of collectors is often employed, utilising chemical adsorption and hydrogen bonding to enhance collection capacity.

II. Acid Leaching for Lithium Extraction

The acid leaching process primarily utilises sulphuric acid. Lithium mica concentrate is mixed with concentrated sulphuric acid and subjected to acid roasting at an appropriate temperature, which disrupts the lithium mica structure and converts the lithium into soluble lithium sulphate. The roasted product is leached with water to obtain a lithium sulphate solution, which is then purified to remove impurities, evaporated and concentrated, and precipitated to yield lithium carbonate. This method also allows for the simultaneous leaching of valuable metals such as rubidium and caesium from the ore. To avoid the high energy consumption and fluorinated exhaust gas issues associated with high-temperature roasting, a low-temperature sulphuric acid roasting process may be employed.

III. Alkaline Lithium Extraction

The alkaline method utilises alkaline substances such as sodium hydroxide or calcium oxide to break the siloxane bonds in lithium mica, converting the lithium into lithium hydroxide. Lithium mica concentrate is mixed with an alkaline solution in a pressurised reactor for leaching; the lithium dissolves into the solution, whilst silicon, aluminium and other elements form recoverable by-products. Following the reaction, solid-liquid separation, ion exchange or precipitation is carried out to produce lithium carbonate or lithium hydroxide. The alkali process avoids corrosion from hydrofluoric acid but requires high-pressure equipment.

IV. Salt Process for Lithium Extraction

The salt process involves mixing lithium mica concentrate with sulphates (such as sodium sulphate, potassium sulphate or calcium sulphate) and roasting the mixture at high temperatures. This disrupts the lithium mica crystal lattice, causing lithium to undergo ion exchange with the alkali metals in the salts, thereby forming soluble lithium salts. The roasted material is then leached using water or dilute acid, allowing the lithium to enter the solution. This method achieves high leaching rates and effective recovery of valuable metals; however, high-temperature roasting generates waste gases containing fluorine and sulphur.

V. Lithium Extraction by Autoclave Process

In the pressure leaching method, lithium mica concentrate is first subjected to defluorination roasting, then mixed with sodium chloride or sodium carbonate, and processed under high-temperature and high-pressure conditions to induce a displacement reaction between lithium and sodium, forming soluble lithium salts. The product is obtained through leaching, purification and lithium precipitation. This process features a short workflow and relatively low costs, but requires operation under high-temperature and high-pressure conditions, placing high demands on equipment safety.