The advent of new energy vehicles not only brings convenience to our lives, but also reduces people's travel costs. In today's high oil prices, new energy vehicles have more significant advantages. However, battery grade lithium carbonate is the main raw material for new energy vehicle batteries. Lithium ores used to extract lithium carbonate mainly include salt lake lithium, spodumene and lepidolite. Lithium extraction from salt lakes is affected by many objective factors, especially when winter comes, the output will also decrease. Therefore, spodumene and lepidolite have become the main raw ores for extracting lithium carbonate. Do you know how to distinguish spodumene from lepidolite? Are their beneficiation methods the same? This article will provide answers.
Spodumene belongs to a kind of pyroxene, which is mainly produced in granite pegmatite, and sometimes can form coarse crystals. Spodumene is a high-quality mineral source for extracting lithium in industry. Spodumene belongs to silicate mineral with chain structure, and its color is mostly gray, green, dark green or yellow, with glass luster, translucent to opaque. The chemical composition of spodumene is LiAl [Si2O6], in which the theoretical content of Li2O is as high as 8.03%. The Li2O content of spodumene concentrate is generally 6.3~7.5%, and the actual content is generally 2.91~7.66%.
Lithium mica is a common lithium mineral and an important mineral for lithium
extraction. It is a basic aluminosilicate of potassium and lithium, belonging to
one of mica minerals. Lithium mica is generally only produced in granite
pegmatite, which is purple and pink in color and can be light to colorless, with
pearly luster, and presents short columns, small flake aggregates or large
tabular crystals. The main composition of lepidolite is KLi1.5Al1.5 [AlSi3O10]
(F, OH) 2, with Li2O content of 1.23-5.90%, often containing rubidium, cesium,
etc.
Due to the high content of Li2O in spodumene and the lower cost of
lithium extraction, it is currently the main mineral used to extract lithium
metal. However, with the continuous optimization of lithium extraction
technology from lepidolite, the cost of lithium extraction continues to
decrease, and the recovery rate gradually increases. At present, lepidolite has
become an important lithium extraction mineral after spodumene.
Although
spodumene and lepidolite are both important minerals for lithium extraction and
further preparation of lithium carbonate, their mineral composition is quite
different, and their beneficiation methods are not the same. Let's take a look
at the differences between the beneficiation methods of spodumene and
lepidolite.
According to the properties of raw spodumene ore, spodumene processing methods include flotation, magnetic separation and gravity separation (heavy suspension method). Flotation is often used as the main method, while magnetic separation and gravity separation are auxiliary methods. Flotation mainly includes positive flotation method and reverse flotation method.
Positive flotation method: this method is to grind the ore first, then use
cationic collectors (sodium hydroxide or sodium carbonate) under strong alkaline
conditions, after high concentration, strong stirring, multiple ore washing and
desliming, and then add fatty acids (such as oleic acid) or saponin collectors
to directly float spodumene. In the flotation process, without adding
inhibitors, sodium hydroxide will combine with silicate in the pulp to form
glass water, which can effectively inhibit gangue minerals such as quartz and
feldspar.
Reverse flotation method: the method of lithium extraction by
reverse flotation is to use lime as the regulator, add dextrin, starch, etc. in
the alkaline medium as the inhibitor to inhibit spodumene, and then use dextrin
amine cationic collectors to collect gangue minerals, first float gangue
minerals, and tailings (in the flotation cell) are lithium concentrates.
The common beneficiation methods of lepidolite include sulfuric acid
roasting, sulfate roasting, limestone roasting, chlorination roasting, pressure
boiling and alkali dissolution.
Sulfuric acid roasting method: after fine
grinding of lepidolite and concentrated sulfuric acid, conduct acidification
roasting at low temperature (110~200 ℃) to obtain acidified clinker for cooling,
and then obtain lithium sulfate solution through water leaching.
Sulfate
roasting method: after mixing lithium mica with sulfate (potassium sulfate,
sodium sulfate or calcium sulfate, etc.), calcine at a certain high temperature
(800~950 ℃) to replace lithium mica and convert it into soluble lithium sulfate,
and then leach with water or dilute acid and filter to obtain lithium
mineral.
Limestone calcination method: after the lithium mica and limestone
are mixed and ground to a certain fineness, they are calcined at high
temperature (800~900 ℃), cooled, and then leached with water to obtain lithium
containing solution.
Chlorination roasting method: after grinding lithium
mica and chlorides (sodium chloride, calcium chloride, etc.), calcine them at a
certain temperature to convert lithium and other valuable metals into soluble
chlorides, and then obtain lithium chloride solution through water leaching.
Chlorination roasting includes two methods: high-temperature roasting and medium
temperature roasting.
Extraction of lithium by pressure boiling method: first, calcine the lithium
mica to defluoride to transform the mineral phase, then mix it with a certain
amount of sodium carbonate for wet grinding, react at a certain temperature (200
℃) and pressure (0.2~2MPa) to replace Na+with Li+, and then add carbon dioxide
to the leaching solution to convert lithium carbonate into soluble lithium
bicarbonate. After solid-liquid separation, lithium bicarbonate solution is
obtained, and lithium carbonate products are obtained after heating and
decomposition.
Method of extracting lithium by alkali melting: mix the
concentrated sodium hydroxide solution with lithium mica, react under a certain
temperature and pressure, so that Li+is decomposed by the concentrated alkali to
generate a mixed solution of aluminate and silicate, then exchange lithium,
potassium and other minerals in the mixed solution into the resin by cation
exchange resin, and then replace lithium and potassium in the resin by dilute
sulfuric acid solution to obtain lithium potassium mixed solution, Finally,
lithium in the mixed solution will be precipitated with sodium carbonate.
It
can be seen that spodumene is mostly processed by physical methods, while
lepidolite is mostly processed by chemical methods. Compared with spodumene, the
lithium extraction process is simpler and the cost is lower, while the
processing method of lepidolite is much more complex.
Xinhai is committed to
providing customers with high-quality mining whole industry chain services
(EPC+M+O), which can complete beneficiation test, scheme design, equipment
manufacturing and installation, concentrator operation and other services. If
there is a demand for lithium ore beneficiation, please contact Xinhai!
