Energy models and the process of fluid-magnetic separation for recovering cobalt micro-particles from vacuum reduction products of spent lithium ion batteries

Improper treatment of spent lithium ion batteries will cause great damages to environment. Vacuum reduction was advised as a green recovery technology of nickel and cobalt from spent lithium ion batteries. However, the separation of magnetic particles from the vacuum-reduced products of spent lithium-ion batteries has not been studied. After reduction, the particle size was so small that the formation of agglomerates would affect the separation efficiency which was a common problem in fine magnetic particle sorting. In this paper, a fluid-magnetic separation method was developed for micro-separation of cobalt from the vacuum reduction product of electrode materials of spent lithium ion batteries. This method had a high level of clean production and sustainable development at the same time as high separation rate. An energy model was established to analyze the mechanism of breaking agglomerates, and the experimental parameters affecting recovery efficiency were studied according to the energy model. In simulation experiments, under the optimal parameter conditions of 35 °C, solid-liquid ratio of 500 mL/g and collection mat material of plastic, the recovery rate and purity of cobalt micro-particles were both above 99%. After applying the vacuum reduction product to fluid-magnetic separation, the recovery rate of magnetic fine particles was 98.26%, which fully verified the effectiveness. Further, it provides a new idea for separating micro magnetic particles from micro-sized mixed particles and promoted the process of recycling spent lithium ion batteries.