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Refining α-Spodumene with Potassium Sulfate Compared to the Conventional Sulfuric Acid Process
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DOI：10.1021/acssuschemeng.4c06207.png)
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Abstract
En 中文
The conventional process of extracting lithium by decrepitating the concentrates of alpha-spodumene and then baking beta-spodumene with concentrated sulfuric acid is the most economic to operate but nonsustainable because of its feedstock, energy, and waste byproduct intensity. Directly extracting lithium from alpha-spodumene by roasting it with potassium sulfate (K2SO4) followed by leaching it with water offers a more sustainable alternative. We optimized the potassium sulfate process (PSP) at a ratio of K2SO4 to spodumene concentrate of 0.6:1 (w/w), 1050 degrees C, and 30 min roasting time, achieving a lithium extraction efficiency of 96.3 +/- 1.4% (w/w), in comparison to 96.66 +/- 0.37% (w/w) for the conventional process, for the same feedstock of spodumene concentrate. While the purification of the leach liquor from PSP is more complex, requiring the addition of aluminum sulfate to recover potassium as potash alum, its byproducts have high economic value. Both processes display a similar energy demand, based on 200 kt y-1 of the spodumene concentrate feed. The use of aluminum sulfate increases the overall cost of PSP by $12.8 million, but sales of potassium alum elevate the revenue by $45.8 million. We reveal that the key advantage of PSP lies in its capability of leveraging the byproducts (leucite and potash alum), while the sulfuric acid process (SAP) may incur disposal cost for its hydrogen aluminosilicate (HAS) byproduct. For PSP to breakeven with SAP, leucite must be converted to a fertilizer and sold at a price of $102.6 t-1 if HAS requires no disposal cost. With the process development focused on the byproduct value, the proposed PSP provides an efficient, more sustainable, and potential near zero-waste alternative to the conventional refining of the lithium chemicals from spodumene.
Keywords:
sustainable lithium refining
lithium extraction
potassium fertilizers
optimization
economicsof lithium processing
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7.3
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1.7W
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10.7W
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