Cleaner Process for the Selective Extraction of Lithium from Spent Aluminum Electrolyte Slag

Spent aluminum electrolyte slag is a byproduct produced during the electrolysis of aluminum and contains elements such as F, Al, Na, and Li. It is a toxic and harmful substance with a stable and complex structure. As a consequence of fluorine pollution and low lithium recovery efficiency in the traditional hydro metallurgy process, a novel cleaner production technology was developed in this research. The lithium was selectively recovered and enriched from spent aluminum electrolyte slag by using calcium salt roasting transformation followed by HBL121solvent extraction. The new process realizes a high leaching efficiency of lithium, solidification of fluorine, low energy consumption, and improved lithium recovery in solutions with low concentrations of lithium. First, the spent aluminum electrolyte slag phase was reconstructed through a calcium sulfate roasting process, which solidified fluorine into CaF2 and transformed lithium into Li2SO4. > 97% lithium can be selectively leached using only water leaching without inorganic acid. After removing calcium from the leaching solution, > 99% of lithium was selectively recovered by HBL121 solvent extraction. The concentration of lithium in the solution increased from 1.24 g/L to 15.56 g/L after stripping. Compared with traditional evaporation and concentration processes, the new process significantly reduces energy consumption, and the extractant can be recycled, resulting in lower recovery costs. Overall, this newly developed process for the selective transformation and enrichment of lithium from spent aluminum electrolyte slag has considerable environmental and economic advantages.