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Click to add WeChatLepidolite (also known as lepidolite) is one of the resources for obtaining lithium minerals. It has large reserves, but the lithium content is low. With the development of new energy industry and lithium battery technology, the demand for lithium is increasing. With the depletion of limited salt lake brine lithium and spodumene resources, lepidolite extraction process will become increasingly important.
At present, the main processes for lepidolite beneficiation (lepidolite extraction) are sulfuric acid method, sulfate roasting method, limestone method, chlorination roasting method, pressure cooking method, alkali dissolution method, etc.
Sulfuric acid method is one of the main methods for lithium extraction from lepidolite, which includes sulfuric acid roasting and impregnation method and sulfuric acid leaching method.
Sulfuric acid roasting and impregnation method: Due to the high roasting temperature, the energy consumption is too high, and the lithium extraction rate is also low, which has been gradually replaced by salt roasting method.
Sulfuric acid leaching method: This method avoids high-temperature roasting, has low energy consumption and low reaction temperature, and is a relatively efficient lithium extraction process with small amount of waste residue. However, this method has requirements for the fineness of lepidolite. Lepidolite needs to be ball-milled to a certain fineness before it can meet the leaching rate requirements, and the reaction time is also relatively long; during the leaching process, a large amount of aluminum will be dissolved, and a large amount of aluminum needs to be removed, which will cause a large loss of lithium; after the reaction is completed, a large amount of sulfuric acid remains, and a large amount of alkali needs to be consumed to neutralize the residual acid.
Lepidolite needs to go through three reaction stages in sulfuric acid medium:
Stage 1: Hydrogen ions in the solution reach the surface of the orthosilicic acid film layer through diffusion and penetrate the orthosilicic acid film layer, and contact the surface particles of lepidolite;
Stage 2: Hydrogen ions react with lepidolite particles to generate soluble sulfates such as lithium sulfate, sodium sulfate, potassium sulfate and aluminum sulfate;
Stage 3: Soluble sulfates penetrate the orthosilicic acid film layer through diffusion to reach the boundary and enter the solution.
The sulfate roasting method mainly involves mixing lithium mica with sulfates such as potassium sulfate, sodium sulfate or calcium sulfate and roasting them at high temperature. The principle is high-temperature ion replacement, that is, using high temperature to destroy the mineral phase structure of lithium mica, making the lithium ore structure loose, and the sodium and potassium in the sulfate react with the lithium ions near the aluminosilicate core in the lithium mica to replace the lithium and convert it into soluble lithium sulfate, which is then leached with water or dilute acid and filtered to extract the lithium.
This method is suitable for processing various lithium ores. During the selection, the aluminum in the minerals will hardly be replaced, the leaching rate is high, and the process is simple. However, to ensure the leaching rate of lithium, more K2SO4 needs to be consumed. During the high-temperature roasting process, more fluorine and sulfide waste gas will volatilize, and the environmental pollution is relatively serious.
The process of extracting lithium from limestone by beneficiation is to mix limestone and lithium mica in a certain mass ratio, grind them into a certain fineness in a ball mill, and then calcine them at 800~900℃ to obtain a lithium-containing solution. This method is simple, but the leaching rate of lithium minerals is low and the amount of limestone used is large.
The chlorination roasting method is to mix lepidolite with chlorides such as sodium chloride and calcium chloride in a certain proportion, grind it through a ball mill, and then roast it at a certain temperature to convert lithium and other valuable metals in lepidolite into soluble chlorides, and obtain a lithium-containing solution after leaching. There are two types of chlorination roasting methods: high-temperature roasting and medium-temperature roasting.
High temperature chlorination roasting: Roasting is carried out at a temperature higher than the boiling point of alkali metal chloride. During the roasting process, alkali metal chloride volatilizes in gaseous form and is separated from impurities;
Medium temperature chlorination roasting: Roasting is carried out at a temperature lower than the boiling point of alkali metal chloride, and then leaching is carried out with water to obtain a solution containing alkali metal chloride.
This method has a high lithium conversion rate, short reaction time, high alkali metal recovery rate, and less waste slag, but during the roasting process, chloride ions seriously corrode the equipment.
The pressure cooking method for extracting lithium minerals is to first roast the lithium ore for defluorination to transform the ore phase, then wet grind it with sodium carbonate in a ball mill at a certain ratio, and then react it at a temperature greater than 200°C and a pressure of 0.2~2MPa, replace the Li ions with Na ions, and introduce carbon dioxide into the water leaching slurry to convert lithium carbonate into soluble lithium bicarbonate. After solid-liquid separation, lithium bicarbonate solution is obtained, and lithium carbonate product is obtained after heating and decomposition.
This method has a simple process flow, small material flow, small equipment corrosion, and low energy consumption, but the recovery rate of lithium minerals is low, the reaction conditions are harsh, leaching under high temperature and high pressure is required, and more carbon dioxide gas is consumed.
Alkali dissolution and extraction of lithium ore is to mix a concentrated solution of sodium hydroxide with lepidolite, react at a certain temperature and pressure, so that the lepidolite is decomposed by concentrated alkali to generate a mixed solution of aluminate and silicate, and then use cation exchange resin to exchange alkali metal ions such as lithium and potassium in the mixed solution into the resin, and then use dilute sulfuric acid solution to replace the lithium and potassium ions in the resin to obtain a solution of alkali metal salts such as lithium and potassium, and then use a concentrated sodium carbonate solution to precipitate lithium in the form of lithium carbonate to extract lithium ore.
This method can almost completely dissolve lepidolite, and the lithium extraction rate is close to 100%, but it is difficult to recycle concentrated alkali waste liquid.
The above is an introduction to the method of extracting lithium from lepidolite. If you want to consult more spodumene, lepidolite lithium extraction technology and related ore dressing equipment, please consult Xinhai Mining.
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