Integrated Lithium Extraction Process for Phosphorite

Phosphorite is a high-grade lithium ore that, in addition to lithium, contains associated valuable components such as phosphorus and aluminium, making it highly valuable for comprehensive utilisation. Traditional lithium extraction processes generally suffer from issues such as high pollution levels and low resource utilisation rates. To address this, the industry has developed an integrated process comprising sulphate roasting, hydrometallic leaching and stepwise purification, which enables the simultaneous recovery of lithium, phosphorus and aluminium, thereby achieving the green and efficient comprehensive utilisation of mineral resources.

The entire process is primarily divided into four major stages: high-temperature roasting, hydrometallic leaching for lithium extraction, leachate refining, and leach residue recycling. The process begins with batch preparation and high-temperature roasting. The phospho-lithium-alumina ore is ground to an appropriate particle size, thoroughly mixed with sulphate-based mineral phase conversion agents, and then fed into a high-temperature furnace for roasting. Under high-temperature conditions, the phospho-lithium-alumina ore undergoes phase decomposition and reacts with the conversion agents. The lithium in the ore is gradually converted into water-soluble sulphates, whilst the phosphorus and aluminium are converted into insoluble phosphates, thereby achieving a preliminary separation of the valuable components.

Once the roasted material has cooled, it enters the leaching stage, where leaching is carried out using fresh water. The soluble lithium salts dissolve fully into the liquid phase, forming a lithium-rich leachate, whilst the phosphorus and aluminium components remain in the leaching residue. Through solid-liquid separation, two main products are obtained: lithium solution and leaching residue, with each material stream proceeding to subsequent processing.

For the lithium-rich leachate, evaporation and concentration are first carried out to increase the lithium concentration, followed by the use of selective precipitation to remove impurity ions such as calcium and magnesium, thereby preventing impurities from affecting the quality of the final product. Precipitation agents are added to the purified solution to initiate the lithium precipitation reaction; following filtration, washing and drying processes, battery-grade lithium carbonate is produced. The entire purification process is highly controllable, and the product purity meets the standards required by the lithium battery industry.

The leaching residue generated after lithium extraction is treated using an acid leaching process. Acid solutions are employed to selectively dissolve phosphate compounds within the residue, followed by adjustment of the solution’s pH to precipitate aluminium phosphate. After solid-liquid separation and high-temperature calcination and crystallisation, a high-purity aluminium phosphate product is obtained. This stage fully exploits the value of the tailings, ensuring that resources are utilised to the fullest extent.