Na2SO4–NaCl binary eutectic salt roasting to enhance extraction of lithium from pyrometallurgical slag of spent lithium-ion batteries

Effectively extracting lithium at a relatively low temperature from the slag produced by the pyrometallurgical treatment of spent lithium-ion batteries remains a great challenge, which limits the acquirement of lithium. Herein, we proposed a eutectic system to roast slag at a lower temperature based on sodium sulfate–sodium chloride (Na2SO4–NaCl) binary eutectic salts. The optimal roasting conditions are as follows: the slag was roasted at 750 °C with a (SO42–+Cl–)/Li+ molar ratio of 5:1 for 120 min. Followed by aqueous leaching 5 min at room temperature with a water/roasted samples mass ratio of 30:1, it can get 97.07% lithium extraction efficiency.