Research Progress on Lithium Extraction from Lepidolite

Lithium, a core material in the new energy sector, faces surging demand driven by electric vehicles and energy storage. In China, lepidolite (chemical formula: KLi₂Al₄Si₅O₁₀F₂OH) has emerged as a critical lithium source due to its abundant reserves, despite challenges like low grade and complex composition. This article reviews advances in acid, alkali, and salt-based extraction processes, analyzes their technical characteristics, and outlines future directions.

1. Main Extraction Processes and Advances

1. Acid Methods

• Sulfuric Acid Process: Lithium is extracted via high-temperature roasting (900°C) and sulfuric acid leaching. Zhang et al. developed a low-temperature roasting method achieving >95% lithium recovery, yet colloidal aluminosilicate adsorption causes lithium loss, necessitating improved impurity removal.

• Hydrofluoric Acid Process: HF dissolves silicates at low temperatures. Guo et al. achieved 94.26% lithium recovery through two-step heat treatment, but HF’s toxicity and wastewater treatment remain critical challenges.

2. Alkali Methods

• Lime Roasting: Limestone assists in breaking Si-O bonds at 750°C. Li Tao reported >99% lithium dissolution, but high energy consumption and solid waste limit economic viability.

• Autoclave Method: Steam at 850°C removes fluorine, converting LiF to Li₂O. Li et al. enhanced defluorination using a fluidized bed reactor with CaO, yet high equipment costs persist.

3. Salt Methods

• Chloride Roasting: CaCl₂ or NaCl displaces lithium ions at high temperatures. Yan et al. optimized the process to achieve 92.86% lithium extraction, but corrosive gases and calcium accumulation require resolution.

• Sulfate Roasting: K₂SO₄ or Na₂SO₄ reacts to form soluble lithium sulfate. Yongxing Materials industrialized a low-temperature composite salt process with >94% efficiency and closed-loop reagent recycling, setting a benchmark.

2. Technical Challenges

1. Environmental and Cost Pressures: Acid methods generate fluoride emissions; alkali processes are energy-intensive; salt methods face slag disposal costs.

2. Low Selectivity: Current processes recover<30% of associated rubidium and cesium, leading to resource waste.

3. High Equipment Requirements: High-temperature, corrosion-resistant equipment demands significant investment.

3. Future Directions

1. Process Synergy: Integrate pretreatment (e.g., ball milling, microwave) to enhance efficiency; adopt membrane separation for purification.

2. Green Innovations: Develop low-toxicity reagents (e.g., bio-based acids) and slag valorization (e.g., converting fluoride residues to construction materials).

3. Intelligent Control: Utilize AI for dynamic optimization of energy consumption and extraction rates.

4. Conclusion

Lepidolite lithium extraction must balance efficiency, economy, and sustainability. Sulfate roasting stands out for its comprehensive performance, yet challenges like rubidium/cesium recovery and slag management persist. Future advancements through technological innovation and multi-process integration will drive efficient, low-carbon development of lepidolite resources, bolstering the new energy industry.