Lithium resources are primarily found in hard rock deposits and salt lake brines, with more than 50% of global lithium reserves originating from hard rock sources. Spodumene, a common hard rock lithium mineral, contains a high lithium content — up to a theoretical 8.03%.So, how to extract lithium from spodumene? We classify spodumene based on its mineral composition, grain size, and oxidation level, and explain in detail the corresponding lithium extraction processes.
Spodumene deposits can be classified into simple spodumene ores and associated polymetallic spodumene ores based on their mineral composition. In actual production, simple spodumene ores are rare, while the majority are associated with other polymetallic minerals. These ores are commonly found in association with tantalum-niobium iron ore, cassiterite, beryl, feldspar, mica, quartz, and others. Due to the complex mineral composition, the lithium extraction process is relatively complicated and typically involves the following steps:
1. Ore Pretreatment
The ore is crushed and ground using crushers and ball mills until 65%–75% passes through a -0.074 mm screen.
2. Gravity Separation
Spiral chutes or shaking tables are used to discard tailings and recover coarse tantalum-niobium minerals or cassiterite.
3. Magnetic Separation
If magnetite is present, weak magnetic separation is used to remove iron, while strong magnetic separation is employed to recover tantalum-niobium minerals.
4. Flotation
Spodumene surfaces are activated using Na₂CO₃ or NaF, followed by the use of fatty acid collectors or combined collectors. Quartz and feldspar are inhibited with starch, and beryl with sodium hexametaphosphate. The flotation process typically involves 1 roughing, 2 scavenging, and 3 cleaning stages, resulting in a concentrate with Li₂O content > 5%.
The extraction of lithium from associated polymetallic spodumene ores generally requires a combined gravity–magnetic–flotation process.
Coarse-grained spodumene is characterized by crystal sizes typically larger than 0.5 mm, making it easy to dissociate. The general beneficiation method involves pre-enrichment via gravity separation, followed by flotation to improve lithium grade.
1. Gravity Separation (Pre-Enrichment)
The separation is based on the density difference between spodumene and gangue minerals.
For coarse particles (2–10 mm), a jig is used to quickly obtain a high-grade coarse concentrate.
For medium to fine particles (0.1–2 mm), a spiral chute is used.
For fine particles (<0.5 mm), a shaking table is employed for gravity separation and concentration.
2. Flotation
The gravity separation concentrate is further processed via flotation to extract lithium.
First, the concentrate is ground to -0.074 mm, accounting for approximately 80%.
Then, a flotation process consisting of 1 roughing, 2 scavenging, and 3 cleaning stages is applied to obtain a lithium concentrate with Li₂O content of 5.5%–6.5%.
The extraction of lithium from coarse-grained spodumene generally adopts a beneficiation process of "coarse grinding – gravity separation – fine grinding – flotation."
The challenges of extracting lithium from fine-grained spodumene include poor mineral dissociation, severe interference from ore slimes, and similar floatability between minerals.
1. Crushing and Stage Grinding
The ore is first crushed to below 10 mm, followed by two-stage grinding. The final grinding fineness should reach -0.038 mm (i.e., particles smaller than 38 μm).
2. Desliming Pretreatment
A hydrocyclone is used to remove slimes smaller than 20 μm, which helps reduce interference during flotation.
3. Flotation
A flotation process of 1 roughing, 2 scavenging, and 3 cleaning stages is adopted:
Roughing aims to recover spodumene,
Scavenging recovers residual lithium,
Cleaning improves the concentrate grade.
Branch flotation is employed to separate pulp by particle size and optimize flotation performance.
4. Concentrate Dewatering
The lithium concentrate is dewatered using thickening + filtration to ensure moisture content is below 12%.
Weathered spodumene ore has been exposed to surface conditions for a long time, leading to chemical alteration of the mineral surface. This results in poor floatability, serious mudification, and large fluctuations in lithium grade. Since the weathering layer covers the spodumene, it hinders reagent adsorption—making ore pretreatment before flotation a critical step.
1. Ore Pretreatment
Scrubbing equipment is used to clean the ore surface and remove slimes, which can eliminate 10%–30% of muddy tailings. If iron or manganese oxides are present on the ore surface, acid washing and activation can improve reagent effectiveness.
2. Flotation
A flotation process of 1 roughing, 2 scavenging, and 3 cleaning stages is applied.
Roughing enables fast recovery,
Scavenging recovers fine-grained spodumene.
3. Tailings Reprocessing
Iron-bearing spodumene can be recovered using a high-gradient magnetic separator. For low-grade tailings, acid leaching with H₂SO₄ achieves a lithium recovery rate of 60%–80%.
The classic approach for weathered spodumene is:“Pretreatment – Flotation – Enhanced Recovery”
Low-grade spodumene refers to ore with Li₂O content below 1.0%. To meet smelting requirements, it must be significantly enriched. This type of ore is often associated with gangue minerals such as quartz, mica, and feldspar. The typical extraction process includes the following steps:
1. Crushing and Grinding
The raw ore is crushed to below 2mm, then ground using a ball mill to around 200 mesh to fully dissociate the spodumene from gangue.
2. Flotation
A flotation process consisting of roughing → cleaning → scavenging is applied. Common reagents include fatty acid or sulfonate collectors, starch and dextrin as depressants, and NaOH as a pH regulator. This step increases the Li₂O grade to 4%–6%.
3. Combined Mineral Processing
Gravity separation is used to discard coarse tailings, while magnetic separation removes iron-bearing minerals, reducing the flotation burden.
4. High-Temperature Calcination
The spodumene is calcined to transform its crystal structure from the α-phase (inert) to the β-phase (reactive), enhancing lithium extraction efficiency.
5. Lithium Leaching
Further lithium recovery is achieved through water or acid leaching, with a leaching rate of 80%–90%.
6. Leachate Purification and Lithium Recovery
Impurities are removed, and lithium is enriched via neutralization precipitation, ion exchange, evaporation crystallization, or solvent extraction, ultimately producing lithium carbonate.
The above introduces five processes for extracting lithium from spodumene. In actual production, mineral processing tests are essential to determine the most suitable beneficiation method based on the ore's characteristics. This ensures maximum resource utilization and minimizes waste.
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