Refining α‑Spodumene\nwith Potassium Sulfate\nCompared to the Conventional Sulfuric Acid Process

The conventional process of extracting lithium by decrepitating\nthe concentrates of α-spodumene and then baking β-spodumene\nwith concentrated sulfuric acid is the most economic to operate but\nnonsustainable because of its feedstock, energy, and waste byproduct\nintensity. Directly extracting lithium from α-spodumene by roasting\nit with potassium sulfate (K<sub>2</sub>SO<sub>4</sub>) followed by\nleaching it with water offers a more sustainable alternative. We optimized\nthe potassium sulfate process (PSP) at a ratio of K<sub>2</sub>SO<sub>4</sub> to spodumene concentrate of 0.6:1 (w/w), 1050 °C, and\n30 min roasting time, achieving a lithium extraction efficiency of\n96.3 ± 1.4% (w/w), in comparison to 96.66 ± 0.37% (w/w)\nfor the conventional process, for the same feedstock of spodumene\nconcentrate. While the purification of the leach liquor from PSP is\nmore complex, requiring the addition of aluminum sulfate to recover\npotassium as potash alum, its byproducts have high economic value.\nBoth processes display a similar energy demand, based on 200 kt y<sup>–1</sup> of the spodumene concentrate feed. The use of aluminum\nsulfate increases the overall cost of PSP by $12.8 million, but sales\nof potassium alum elevate the revenue by $45.8 million. We reveal\nthat the key advantage of PSP lies in its capability of leveraging\nthe byproducts (leucite and potash alum), while the sulfuric acid\nprocess (SAP) may incur disposal cost for its hydrogen aluminosilicate\n(HAS) byproduct. For PSP to breakeven with SAP, leucite must be converted\nto a fertilizer and sold at a price of $102.6 t<sup>–1</sup> if HAS requires no disposal cost. With the process development focused\non the byproduct value, the proposed PSP provides an efficient, more\nsustainable, and potential near zero-waste alternative to the conventional\nrefining of the lithium chemicals from spodumene.