Acid leaching of mixed spent Li-ion batteries

Abstract

Acid leaching for different types of mixed spent Li-ion mobile batteries is carried out after alkali decomposition using NH 4 OH followed by H 2 SO 4 + H 2 O 2 leaching. In the alkali decomposition step, the effects of reaction time, NH 4 OH concentration, liquid/solid mass ratio and reaction temperature on the decomposition process are investigated to remove Al, Cu, Mn, Ni, Co, and Li. After alkaline treatment, the alkali paste is treated to leach the remaining metals using H 2 SO 4 + H 2 O 2 . The significant effects of reaction time, acid concentration, H 2 O 2 concentration, liquid/solid mass ratios and reaction temperature on the leaching rate are studied. More than 97% of Al, Mn, Ni, Co, and Li and about 65% Cu are leached in two stages. Kinetic analysis shows that, the data fit with chemical reaction control mechanism and the activation energies for the investigated metals using the Arrhenius equation ranged from 30.1 to 41.4 kJ/mol. Recovered metals are precipitated from the leaching liquor at varying pH values using NaOH solution and Na 2 CO 3 . Firstly, Mn is precipitated as MnCO 3 at pH = 7.5. Secondly, at pH = 9.0, nickel is precipitated as NiCO 3 . Thirdly, as the pH of the leaching liquor reaches 11–12, Co(OH) 2 is precipitated and the remaining Li is readily precipitated as Li 2 CO 3 using a saturated Na 2 CO 3 solution. Based on the experimental data, a flow sheet is developed and tested for the recovery process.