Selective leaching and recovery of lithium ions from lithium slag with low lithium content

Abstract Hard rock lithium ore has become a significant natural lithium resource, which is second only to brine lithium resources. However, the recovery process generates a considerable quantity of tailings with very low lithium content. At present, there is no established process for efficient recovery of lithium ions from low‐grade lithium ores. In this study, a novel recovery method was established to extract lithium ions from a tailing slag with lithium content of 0.8% by using sulphuric acid solution as leaching reagent. Furthermore, the mechanism of the recovery process was deeply explored. In accordance with the optimal leaching conditions with hydrogen–lithium ratio as 2:1, leaching temperature as 70°C, and leaching time as 60 min, the leaching rate of lithium ion reached up to approximately 100%. The obtained low lithium‐ion solution was concentrated to yield a lithium‐rich solution, which was then used to produce the lithium products. Lithium phosphate product was obtained by precipitation of lithium ion with sodium dihydrogen phosphate with the addition of sodium hydroxide and oxalic acid to remove impurities. The recovery and purity of lithium phosphate were 94.5% and 99.7%, respectively. This study demonstrated the successfully selective recovery of lithium ions from low‐grade lithium tailing slag through a novel and efficient recovery method.