Developing an Oscillatory Flow Packed Column for Intensified Sequential Metal Extraction from Spent Lithium-Ion Battery Leachate: Process Optimization and Environmental Assessment

An intensified solvent extraction process using an oscillatory flow packed column (OFPC) was developed for sequential recovery of Mn, Co, and Ni from lithium-ion battery (LIB) leachate streams. Hydrodynamic feasibility was first evaluated to establish the operating window of the OFPC, followed by single-factor experiments and response surface methodology (RSM) to systematically investigate the effects of pH, phase ratio, and residence time on extraction performance. Under optimal conditions, extraction efficiencies exceeding 99% were achieved for Mn, Co, and Ni with high separation factors, confirming efficient sequential metal partitioning in a continuous intensified system. Experimental results showed good agreement with model predictions, validating the robustness of the RSM-based optimization strategy. A Waste Reduction Algorithm-based environmental assessment was further conducted to benchmark the OFPC process against a conventional mixer–settler configuration. Owing to enhanced mass-transfer efficiency and reduced energy demand, the OFPC process achieved a 37.6% reduction in total potential environmental impact (PEI) output rate and a 50.8% decrease in PEI generation rate. Overall, the coupling of oscillatory hydrodynamics with packed column intensification enables high-efficiency sequential recovery of critical metals while significantly reducing environmental burdens, providing a robust and sustainable alternative for LIB recycling.