Biomass-Assisted Reductive Leaching in H2SO4 Medium for the Recovery of Valuable Metals from Spent Mixed-Type Lithium-Ion Batteries

A hydrometallurgical method involving natural biomass waste as reductant was proposed for the treatment of spent mixed-type lithium-ion batteries. Results showed that almost complete dissolution of Li, Ni, Mn and nearly 90% dissolution of Co were achieved under the optimal conditions of H2SO4 concentration of 2 M, waste tea biomass dosage of 0.3 g/g, solid/ratio of 50 g L-1, temperature of 90 degrees C and time of 120 min. The leaching kinetics was further investigated, and the activation energies were determined to be 1.7 kJ mol(-1), 10.3 kJ mol(-1), 10.1 kJ mol(-1) and 10.9 kJ mol(-1) for Li, Ni, Mn and Co, respectively. The cathode materials before leaching and the leaching residue were characterized with different analytical methods. The characterization results confirmed that the addition of the waste tea acted as reductant and resulted in better dissolution of the metals, supporting the principles of sustainable processes by decreasing the chemical consumption and integrating waste into a secondary use.