Kinetics of Ni and Co Recovery via Oxygen-Enriched Pressure Leaching from Waste Lithium-Ion Batteries

In the process of the comprehensive recovery and utilization of discarded lithium-ion batteries via acid leaching, a large number of NiS and CoS mixed materials are produced. To improve the metal recovery rate, the kinetics and rate-determining step of the oxygen-rich pressurized acid leaching of Ni and Co were investigated. The results showed that the leaching rates of Ni and Co were greater than 99% under the following conditions: sulfuric acid (leaching agent) concentration of 95 g/L, liquid-to-solid ratio of 6:1, leaching time of 120 min, temperature of 110 degrees C, stirring speed of 400 r/min, 90% oxygen-rich atmosphere, and pressure of 1.2 MPa. The leaching of Ni and Co was described by the shrinking unreacted core model, and the leaching rates of Ni and Co conformed to the kinetic equation 1 - (1 - x)(1/3) = k center dot t. The apparent activation energies of the Ni and Co leaching reactions were 50.87 and 45.6 kJ/mol, respectively, and the leaching process was found to be controlled by the chemical reaction at the interface.