Industrial grade lithium carbonate background and overview
Lithium carbonate is widely used in the production of secondary lithium salts and metallic lithium products. It is the most critical product in the lithium industry. In the current actual production process of lithium carbonate, its main production raw materials come from salt lake brine and ore extracts. At present, in the production process of lithium carbonate in my country, the solid fluorphlogopite ore extraction method is mainly used, and abroad the salt lake brine extraction process is mostly used. At present, our country is also actively exploiting salt lake lithium resources, but due to limitations in technology, resources and other factors, the development speed is relatively slow. To this end, it is necessary to conduct in-depth research on the production and application of battery-grade lithium carbonate. Lithium carbonate is widely used in industrial production and is also one of the important raw materials in pharmacy. It also plays a very important role in the development of the chemical industry. In its actual production practice, lithium carbonate is divided into industrial grade lithium carbonate and battery grade lithium carbonate according to different purity.
Industrial grade lithium carbonate applications
Industrial-grade lithium carbonate can be used to prepare battery-grade lithium carbonate and other compounds. Examples of its applications are as follows:
1) The method of purifying and preparing battery-grade lithium carbonate from industrial-grade lithium carbonate is to mix industrial-grade lithium carbonate and water to form a slurry, add organic acids drop by drop while stirring at a constant speed to convert the lithium carbonate into a soluble clear liquid, and then Add the aqueous solution of urea to it, adjust the pH value to about 10, and control the temperature between 80°C and 100°C, so that the urea slowly releases CO2 gas and precipitates lithium carbonate. This method combines the advantages of the lithium formate recrystallization method and the urea precipitation method, and uses the CO2 produced by the hydrolysis of urea in the urea homogeneous precipitation method as the source of CO2 gas in the lithium formate recrystallization method to avoid local reactions that cause crystallization to precipitate too quickly. The generated lithium carbonate particles are large and are not suitable for secondary aggregation. The particles do not contain impurity ions in the solution system, which improves product purity, effectively removes impurity ions, and reduces production costs. At the same time, industrial grade lithium carbonate is used as raw material, which simplifies the production process compared to the refined lithium hydroxide used in the urea homogeneous precipitation method.
2) The method of preparing lithium hydroxide from industrial grade lithium carbonate solid belongs to the field of lithium hydroxide preparation. The invention uses industrial grade lithium carbonate solid as raw material to prepare lithium hydroxide, and removes solid impurities, sodium, calcium, Magnesium, aluminum, iron plasma, plate and frame filtration can separate solids and liquids, multi-media filtration is used to remove suspended solids, colloids, organic matter, etc. Ultrafiltration can further reduce the content of residual COD, suspended solids and dissolved macromolecules. To achieve the purification and separation of liquids, the chelating resin makes the high-valent ion content in the liquid meet the water inlet requirements of the bipolar membrane. The sulfate radicals in the pre-electrolyte migrate to the acid chamber and combine with the hydrogen ions decomposed on the anode surface of the bipolar membrane. Sulfuric acid is generated, and the lithium ions in the pre-electrolyte migrate to the alkali chamber and combine with the hydroxide ions decomposed on the negative membrane surface of the bipolar membrane to generate lithium hydroxide.
Preparation of industrial grade lithium carbonate
A method for preparing industrial grade lithium carbonate by recovering lithium from spodumene calcium and magnesium slag, including the following steps:
A. Dissolution of lithium-containing calcium magnesium slag: Under normal temperature conditions, put a certain mass of spodumene calcium magnesium slag into the reaction vessel, add a certain mass of pure water while stirring, and use a density meter to monitor and control the solution. When the density is 1.167~1.211g/cm3, a calcium magnesium slag solution is obtained;
B. Acid addition reaction: At room temperature, slowly add concentrated sulfuric acid with a mass percentage concentration of 98% to the calcium magnesium slag solution obtained in step A while stirring, adjust the pH of the solution to 5 to 7, and obtain a slightly acidic solution. , stir and react at room temperature for 1 to 2 hours;
C. Quicklime magnesium removal: Add quicklime with a purity of 60 to 80% to the slightly acidic solution obtained after reacting for 1 to 2 hours in step B again, adjust the pH to 10 to 11, stir and react for 0.5 to 1.5 hours, and filter to obtain the removal of magnesium. Magnesium containing lithium solution and slag, the slag is then washed with 2 times the pure water to obtain the eluent;
D. Concentrate and add alkali to remove calcium: Mix the magnesium-containing lithium-containing solution and the eluent of the primary filtration solution obtained in step C, and then heat it to 110-120°C for concentration, and concentrate it to 5-10 times to Li The concentration is 5-11g/L, and then 32% liquid caustic soda is added to adjust the pH to 12-13, and filtered to obtain a solution rich in lithium for preliminary calcium removal;
E. Deep calcium removal with soda ash: Heat the preliminary calcium-removed lithium-rich solution obtained in step D to 80-90°C, and then add an excess of 5% sodium carbonate solution with a concentration of 180-230g/L based on molar Ca. , that is, the molar ratio Na2CO3:Ca=1.05:1, stir and react at 80-90°C for 0.5-1h, remove the remaining calcium, and filter to obtain a filtered lithium-containing solution with Ca<10ppm;
F. Acidification and impurity removal: Add sulfuric acid to the filtered lithium-containing solution obtained in step E to adjust the pH to 2~3, then heat to 80~90°C, stir and react for 0.5h, and obtain an acidification and impurity removal solution;
G. Lithium precipitation with soda ash: Concentrate the acidified impurity removal solution obtained in step F to a Li concentration of 16-20g/L, then add 32% liquid caustic soda to adjust the pH to 11-12, at about 85-95°C Add 5% excess sodium carbonate solution with a concentration of 180-230g/L based on mole Li, that is, molar ratio Na2CO3:Li=2.1:1, stir for 0.5-1h, filter, rinse and dry to obtain industrial grade lithium carbonate. .
The specific reaction principle analysis is as follows: using H2SO4, the insoluble Li2CO3 can be reacted into Li2SO4 and CO2, in which Li2SO4 is dissolved in the solution in the form of ions.��, CO2 volatilizes in the form of gas. At the same time, H2SO4 will also react with Mg(OH)2, causing Mg to dissolve in the solution in the form of ions. Then add CaO to precipitate Mg, and at the same time, SO42- in MgSO4 can be precipitated. This achieves solid-liquid separation and recovery of Li, and Li2SO4 is mainly present in the solution. The reaction equation is:
