Integrated acid leaching of spent battery cathode material (LCO, NMC111) and flotation tailings of pyrite and pyrrhotite

Lithium-ion batteries require number of metals which have been listed as critical raw materials in European Union due to their supply risk and economic importance. Therefore, more emphasis needs to be put on (i) recycling of spent batteries, (ii) utilizing other secondary sources of battery metals and primary mining waste. In this research, leaching of battery metals from cathode materials—lithium cobalt oxide (LCO) and lithium nickel manganese cobalt oxide (NMC111)—was investigated with the aim to use waste fraction of primary mining, namely sulfide-rich flotation tailings, as reductant. Two types of tailings were investigated in the current study: pyrrhotite-pyrite tailings and pyrite tailings. These tailings contain reductive power necessary for leaching, as well as battery metals incorporated in the sulfide matrix. The investigated parameters were temperature (40–80 °C) and mass ratio of cathode material and tailings (0.5–2 g/g) whereas S/L-ratio (100 g/L), acid concentration ([H 2 SO 4 ] = 1 M), and leaching time (180 min) were kept constant. The results showed that both pyrrhotite-pyrite as well as pyrite dominated tailings can act as an effective reductant for the leaching of metals from cathode materials. The extraction efficiency of battery metals correlate with dissolved iron concentration. When only pyrite tailings were used in the process, the reductive effect of S 2 2− could also be recognized as lower concentration of dissolved Fe 2+ was required when compared to use of pyrrhotite tailings. At 80 °C, LCO and NMC could be completely dissolved within 60min while simultaneous extraction of battery metals from sulfide flotation tailings was up to 17 % of Ni, 15 % of Co, and 27 % of Cu. • LCO and NMC can be completely reduced by sulfide tailings. • Both pyrrhotite and pyrite can act as reductant for cathode material. • Reduction of LCO by Fe 2+ occurs faster than oxidation of tailings by Fe 3+ . • Additional battery metals can be extracted from tailings to leach solution.