Lithium is an important raw material for energy supply. With the rapid rise of new energy sources, lithium ore resources have been pushed to a development boom. The common lithium resources are mainly pegmatite lithium and brine lithium, among which the development of brine lithium is difficult, and currently most of them are pegmatite type. The pegmatite-type lithium resources are mainly spodumene and lepidolite.
Lepidolite is the most common lithium mineral and is an important mineral for lithium extraction. It is a basic aluminosilicate of potassium and lithium, which is one of the mica minerals. Lepidolite is generally only produced in granite pegmatites. The color is purple and pink and can be light to colorless. It has a pearly luster and is in the form of short columns, small flake aggregates or large plate-shaped crystals.
Spodumene is a kind of pyroxene, which is mostly produced in granite pegmatite, and sometimes can form coarse crystals. Spodumene is a high-quality ore source for lithium extraction in industry, but spodumene with beautiful color and transparent crystal ( Emerald spodumene, purple kodumene) are used as gem materials, usually gem-grade spodumene can weigh more than 1 carat, and spodumene exceeding 5 carats is not uncommon.
1. Mineral processing method of spodumene
Spodumene is a silicate mineral with a chain structure, and its color is mostly off-white, green, dark green or yellow, with glass luster, translucent to opaque. According to its ore properties, the beneficiation methods that can be used for spodumene include flotation, magnetic separation and gravity separation (resuspension method), while flotation is often used as the main method, and magnetic separation and gravity separation are auxiliary methods. Flotation mainly includes: forward flotation and reverse flotation.
01. Positive flotation method
The method is to firstly grind the ore finely, then use a cationic collector (sodium hydroxide or sodium carbonate) under strong alkaline conditions, after high concentration, strong stirring, and multiple times of ore washing and desliming, then add fatty acids (such as Oleic acid) or saponins collectors, directly flotation spodumene. In the flotation process, there is no need to add inhibitors. Sodium hydroxide will combine with the silicate in the pulp to form glass water, which can effectively inhibit the gangue minerals such as quartz and feldspar.
02. Reverse flotation method
The reverse flotation lithium extraction method is to use lime as a regulator, add dextrin, starch, etc. as inhibitors in alkaline media to inhibit spodumene, and then use dextrin amine cationic collectors to collect gangue minerals. The gangue minerals are first floated out, and the tailings (in the flotation tank) are lithium concentrates.
2. Mineral processing method of lepidolite
Lepidolite (also known as scale mica) belongs to the mica group minerals, is a layered silicate, the color is rose, purple, light purple, grayish yellow, sometimes colorless, non-magnetic, from which lithium, rubidium, Cesium and other valuable metals. Commonly used mineral processing methods include sulfuric acid roasting method, sulfate roasting method, limestone method, chlorination roasting method, pressure cooking method and alkali dissolution method.
01. Sulfuric acid roasting method
The sulfuric acid roasting method is to finely grind lepidolite and concentrated sulfuric acid, then acidify and roast at low temperature (110~200°C) to obtain acidified clinker, cool it, and then immerse in water to obtain lithium sulfate solution.
02. Sulfate roasting method
The sulfate roasting method is to mix lepidolite with sulfate (potassium sulfate, sodium sulfate or calcium sulfate, etc.) and roast at a certain high temperature (800~950°C) to replace lepidolite and convert it into soluble lithium sulfate. , and then leached with water or dilute acid and filtered to obtain lithium minerals.
03. Limestone method
The limestone roasting method is to mix and grind lepidolite and limestone to a certain fineness, then roast at high temperature (800~900°C), cool and leaching with water to obtain a lithium-containing solution.
04. Chlorination roasting method
The chlorination roasting method is mainly to grind lepidolite and chlorides (sodium chloride and calcium chloride, etc.) and roast them at a certain temperature to convert lithium and other valuable metals into soluble chlorides, and then obtain them by water immersion. Lithium chloride solution, chlorination roasting has two methods: high temperature roasting and medium temperature roasting.
High-temperature method: the roasting temperature should be higher than the boiling point of the alkali metal chloride. During the roasting process, the alkali metal chloride is volatilized (in gaseous form) and separated from impurities.
Medium temperature method: the roasting temperature is lower than the boiling point of alkali metal chloride, and the solution containing alkali metal chloride is obtained by water leaching.
05. Pressure cooking method
Lithium extraction by pressure cooking requires roasting and defluorinating lepidolite to transform the ore phase, and then wet grinding it with a certain amount of sodium carbonate, at a certain temperature (200°C) and a certain pressure (0.2~2MPa). Reaction, Na+ is replaced by Li+, and then carbon dioxide is added to the leaching solution to convert lithium carbonate into soluble lithium bicarbonate. Lithium bicarbonate solution is obtained after solid-liquid separation, and lithium carbonate product is obtained after heating and decomposition.
06. Alkali solution method
The method of alkali melting lithium extraction is to mix the concentrated sodium hydroxide solution with lepidolite, and react under a certain temperature and pressure, so that Li+ is decomposed by concentrated alkali to form a mixed solution of aluminate and silicate, and then use cation exchange resin Exchange lithium, potassium and other minerals in the mixed solution into the resin, and then use dilute sulfuric acid solution to replace the lithium and potassium in the resin to obtain a lithium-potassium mixed solution, and finally use sodium carbonate to precipitate the lithium in the mixed solution .
Spodumene and lepidolite are the main mineral resources for extracting lithium. There are different methods for extracting lithium. In the actual concentrator, the choice should be made according to the nature of the lithium ore. Therefore, the editor recommends to conduct a beneficiation test first, and design a suitable lithium extraction method and customize lithium ore beneficiation equipment through test analysis.