Process Analytical Technology-Integrated FT-IR and Raman Spectroscopies for Efficient Reactive Liquid–Liquid Extraction Processing in Lithium Recycling

Lithium is a strategic metal that is essential for the electrification of the economy and society as it is commonly used in high-tech applications and batteries. The EU has mandated that 25% of annual consumption be sourced from recycling. To achieve this goal in an economic and ecological manner, recycling processes need to improve in efficiency. One path toward this aim is by introducing smart control enabled by process analytical technologies (PATs). In this work, a framework for the integration of an in-line spectroscopy system with a chemometric model as a PAT methodological approach for a typical reactive liquid-liquid extraction using a synergistic solvent with a β-diketone is exemplified. The concentration of extractants and the degree of saponification as well as the concentration of metal-ion complexes in the organic phase are to be measured with FT-IR and Raman spectroscopies. This is achieved by generating partial least-squares regression models with a coefficient of regression <i>R</i> ² of minimum of 0.95 for application in a continuous process. With these, a reduction of the chemical cost for a typical lithium purification plant of 15% with a reduction in the global warming potential (GWP) of 20% and a return on investment of less than 0.4 years is estimated.