2017 Volume 1 Pages 1-8
For recycle of cathode materials (LiCoO2) contained in spent lithium ion batteries, hydrothermal leaching with organic acids(citric acid and oxalic acid) was investigated. Hydrothermal leaching of LiCoO2 with 0.4 M citric acid at 423 K for 30 min of treatment time by convective heating was compared with that by microwave-assisted heating. Both Li and Co leaching yields were higher with the microwave heating than yields with convective heating. Hydrothermal leaching of LiCoO2 with oxalic acid additives was also studied. In this case, the yield of the solid residue that was probably Co-oxalate was promoted by the microwave heating. Diffusion of Li and Co at the surface boundary layer at the unreacted LiCoO2 core is possibly the controlling step of the leaching process. Microwave affects not only heating rate, but also diffusion of ions-water clusters and thus probably enhanced the leaching efficiency for citric acid and the solid residue formation for oxalic acid. The effect of treatment temperature, treatment time and concentration of citric acid on the hydrothermal leaching of LiCoO2 citric acid was evaluated. Almost 100 % of leaching yield of Li and Co was achieved over 423 K with 0.4 M citric acid. Hydrothermal leaching with 0.4 M oxalate acid at 423 K allowed Li ion to be completely leached but gave Co ion and oxalate anion complex that was insoluble in water.