Chemical leaching, precipitation and solvent extraction for sequential separation of valuable metals in cathode material of spent lithium ion batteries

Spent lithium ion batteries (LIBs) can be of great environmental concern because of the generation of heavy metal pollution in such wastes in huge quantities, mainly from the fast-growing mobile phone market. In this research, acidic leaching coupled with microwave and ultrasonic heating is integrated with oxidative precipitation and solvent extraction to reclaim and purify the metals in the cathode material of batteries. To optimize the leaching process, the effects of the concentrations of acids and reductant (H2O2), solid loading, and temperature, as well as heating with microwaves and ultrasound, on Co, Li, Mn, Ni, Cu, and Al dissolution are systematically tested. KMnO4 is first applied to remove Mn as MnO2 precipitate from the leachate, and most of the Li can be selectively collected in the aqueous phase by solvent extraction using di-(2-ethylhexyl) phosphoric acid. At the end of the process, the majority of Co and minor amounts of Ni, Cu and Al are reversely extracted using HCl. An effective purification process is proposed to obtain more than 90% of the valuable metals in each of the leaching, precipitation and extraction steps.