Membrane Processes for Wastewater Treatment in Direct Battery Recycling. Experimental Evaluation, Zero Liquid Discharge Potential and Lithium Carbonate Recovery

The rapid expansion of lithium-ion battery use has increased the demand for critical raw materials, while a large share of spent batteries remains unrecycled. Efficient recycling and resource recovery are therefore essential to reduce environmental impacts and secure material supply. This study investigates the treatment of wastewater generated during the anode delamination step in the End-of-Life LFP direct recycling process developed by the company KYBURZ Switzerland AG. The work focuses on membrane filtration techniques—microfiltration, nanofiltration (NF), and reverse osmosis—for the recovery of water and lithium (Li), aiming to reduce environmental impacts and improve the sustainability of the recycling process. Two NF operational processes were elaborated. In the first, NF operated in diafiltration mode, where fresh water was continuously added at the same rate as permeate withdrawal, allowing Li to be progressively washed out of the anode wastewater. In the second process, the feed was first concentrated by NF, then the retentate was diluted with fresh water and concentrated again, enabling sequential permeate recovery. This second approach showed better performance, reducing energy consumption and operational costs while achieving Li recovery up to 91% in industrial-scale simulations. Subsequent reverse osmosis enabled the recovery of about 98% of water at industrial-scale conditions, while Li was almost completely retained and further concentrated, indicating strong potential for a zero-liquid-discharge approach. Screening tests showed that Li can be recovered as lithium carbonate through precipitation with sodium carbonate and ethanol, although further work is needed to improve product purity. Life Cycle Assessment results indicate lower environmental impacts for KYBURZ with membrane implementation compared with conventional recycling routes, highlighting the potential of membrane-based wastewater treatment to enhance Li recovery and water reuse.