The raw materials for making lithium carbonate mainly include sodium bicarbonate, calcium carbonate and lithium hydroxide.
1. Sodium bicarbonate: Sodium bicarbonate is one of the main raw materials of lithium carbonate, and the chemical formula is NaHCO3. Sodium bicarbonate can be prepared by the reaction of soda ash or industrially synthesized sodium hydroxide with pure carbon dioxide. This method mainly uses the process of reacting metal ions with alkaline solution to generate carbonate precipitation to extract metal ions, which is a typical "precipitation method".
Advantages: Raw materials are easy to obtain and the cost is low. Disadvantages: The process is long, and it needs to go through steps such as sedimentation, separation, dissolution, and evaporation, and a certain amount of wastewater and waste residue will be generated in the production process.
2. Calcium carbonate: Calcium carbonate is also one of the commonly used raw materials for the preparation of lithium carbonate, with the chemical formula CaCO3. Calcium carbonate is a mineral, which can be used as one of the raw materials for lithium carbonate preparation after beneficiation and grinding. This method belongs to the "carbonization method", that is, calcium carbonate is prepared by calcining calcium oxide and carbon dioxide obtained by calcination of limestone.
Advantages: abundant raw materials and low cost. Disadvantages: It needs to go through multi-step reaction and high-temperature carbonization treatment, which has high energy consumption, and a large amount of waste gas and waste residue will be generated in the production process.
3. Lithium hydroxide: The chemical formula of lithium hydroxide is LiOH, which is the direct preparation of lithium carbonate. Sodium bicarbonate or calcium carbonate is commonly used as raw materials to prepare lithium carbonate. This method belongs to the "conversion method", that is, lithium hydroxide is used to react with acid to produce corresponding salts, and then converted into lithium carbonate by pyrolysis and other means.
Advantages: lithium carbonate can be directly prepared without multi-step reaction and separation operations, and the product has high purity. Disadvantages: Higher cost of raw materials.
In nature, lithium minerals are also important raw materials for the preparation of lithium carbonate, such as spodumene, lepidolite, petalite feldspar, etc.
Fourth, spodumene: spodumene is one of the main raw materials for the extraction of lithium carbonate, which is mainly extracted by sulfuric acid method. The specific steps include crushing, grinding, acidizing, evaporation and crystallization. The lithium ions in spodumene react with sulfuric acid to form lithium sulfate, and then go through carbonation, neutralization and other steps to obtain lithium carbonate. This method has a high extraction rate and purity, but requires a large amount of sulfuric acid and sodium carbonate, and the cost is higher.
Advantages: Spodumene has a high lithium content, which can reduce production costs, and spodumene resources are abundant. Disadvantages: It needs to go through multi-step processes such as crushing, grinding, acidification, evaporation and crystallization, and requires a large amount of sulfuric acid and sodium carbonate, and the cost is high.
Fifth, lepidolite: The method of extracting lithium carbonate from lepidolite is similar to spodumene, and the sulfuric acid method is also used. First, the lepidolite is crushed, ground finely, and then sulfuric acid is added for acidification to release the lithium ions in the lepidolite. After filtration, washing, drying and other steps, the filter cake containing lithium is obtained, and lithium carbonate is obtained by carbonation, neutralization and other steps. Compared to spodumene, lepidolite has more impurities and requires further processing to obtain high-purity lithium carbonate.
Advantages: Lepidolite has a high lithium content and abundant resources. Disadvantages: It needs to go through multiple processes such as crushing, grinding, acidification, evaporation and crystallization, and there are many impurities, and further processing is required to obtain high-purity lithium carbonate.
6. Salt lake brine: Salt lake brine is rich in sodium, potassium, calcium, magnesium and lithium, among which the content of lithium is low, but the resources are abundant. The extraction of lithium carbonate from salt lake brine mainly uses the solar pool method and the evaporation crystallization method. The solar pond method is to inject salt lake brine into a sealed pond, and through natural evaporation of solar energy, the water is evaporated to obtain lithium-containing salts, and then processed to obtain lithium carbonate. The evaporation crystallization method is to introduce salt lake brine into the evaporation crystallizer, and obtain lithium carbonate through steps such as heating evaporation and cooling crystallization.
Advantages: abundant resources and low cost. Disadvantages: The extraction rate and purity are low, and further processing is required to obtain high-purity lithium carbonate.
7. Waste batteries: Waste batteries are rich in metal elements, including cobalt, nickel, manganese, lithium, etc., of which the content of cobalt and nickel is high. **Lithium carbonate in used batteries is mainly used by two methods: fire method and wet process. The fire method is to incinerate waste batteries at high temperatures, remove chemicals and water in them to obtain residues containing metal elements, and then go through acid dissolution, filtration and crystallization to obtain lithium carbonate. The wet method is to add acid to dissolve the waste battery after crushing, and then go through the steps of extraction, separation and reduction to obtain lithium carbonate.
Advantages: It can make full use of the resources in the waste battery and reduce environmental pollution. Disadvantages: It needs to go through multiple steps such as crushing, dissolving, extraction, separation and reduction, and further processing is required to obtain high-purity lithium carbonate.