An innovative and value-added approach to recycle hexafluorophosphate from waste lithium-ion batteries: New perspective of electrolyte disposal and recovery

Waste effluent derived from spent lithium-ion batteries (LIBs) electrolyte is unavoidable in the recycling industry. But little attention has been paid to the disposal and treatment of the poisonous hexafluorophosphate-containing electrolyte effluent at present. In this study, an efficacious and green process was firstly proposed to recover hexafluorophosphate rapidly from spent solutions via liquid-liquid extraction and chemical precipitation. DFT calculations also provide a theoretical basis for extraction. The results showed that extraction efficiency was 79.26 % with first extraction and reached almost 100 % after two-stage extraction using Alamine336/TBP as extractant under optimal conditions (0.4 mol/L of Alamine336, 5 min, O/A ratio of 1). Subsequently, the hexafluorophosphate could then be recovered in the form of potassium hexafluorophosphate through ammonia scrubbing and precipitation. The extractant was not consumed and could be reused. Accordingly, this study provides an effective and environmentally friendly approach for reclaiming the hexafluorophosphate from spent LIBs, which is expected to be widely applied in practical production and meet the requirements of green circulation and sustainable development.