A study on optimization of graphite separation in lithium-ion battery waste recycling via froth flotation and selective flocculation: A response surface methodology approach

Abstract

The growing demand for lithium-ion batteries (LIBs) necessitates effective recycling methods to recover valuable materials and mitigate environmental impact. This study investigates the optimization of graphite separation from LIB waste using froth flotation and selective flocculation. Flotation is utilized due to the natural hydrophobicity of graphite compared to the hydrophilic nature of cathode materials, making it a suitable method for separation. Selective flocculation is explored to enhance the efficiency of this process by promoting the aggregation of target particles.

Key flotation parameters, including solid content, impeller tip speed, conditioning time, and flocculant dosage, were systematically varied and analyzed using a Response Surface Methodology (RSM) approach. Results indicated that employing ultrafine cathode particles (<10 µm) in the model black mass feed achieved a graphite concentrate grade of 98.63% with a recovery rate of 71.98% in a single-stage flotation process. Among the parameters studied, solid content was found to have the most significant impact on graphite grade, while impeller tip speed and flocculant dosage most influenced graphite recovery.

Through response optimization, it was determined that optimal conditions include a solid content of 20 g/L, a conditioning time of 13 min, and an impeller tip speed of 1040 rpm, resulting in a graphite grade of 99.02% and a graphite recovery of 74.54%. This study highlights the potential of combining froth flotation with RSM to enhance the efficiency and effectiveness of graphite separation in LIB recycling processes. Future research should explore alternative pH levels, flocculants, and multi-stage flotation processes to further improve separation performance.