Efficient Recovery of Lithium from Spent Lithium Ion Batteries Effluent by Solvent Extraction Using 2-Ethylhexyl Hydrogen {[Bis(2-Ethylhexyl) Amino]methyl} Phosphonate Acid

Abstract

In order to overcome the interface emulsification problem of TBP-FeCl3 systems and the instability of β-diketone systems in high-concentration alkaline medium, it is necessary to design and synthesize some new extractants. By introducing amino groups into a phosphorus extractant, a new 2-ethylhexyl hydrogen {[bis(2-ethylhexyl)amino]methyl} phosphonate acid (HA) extractant was synthesized. In this study, an efficient method of recovering lithium from the effluent of spent lithium-ion batteries (LIBs) is proposed. Experiments were conducted to assess the influential factors in lithium recovery, including the solution pH, saponification degree, extractant concentration, and phase ratio. Over 95% of lithium in the effluent was extracted into the organic phase, and nearly all lithium in the organic phase could be stripped into the aqueous phase using a 3 mol/L HCl solution. There was no significant decrease in extraction capacity after 10 cycles. The experimental results indicated that the extraction mechanism was a cation exchange process, and the extractive complex was proposed as LiA. Importantly, after three months of stable operation, the process demonstrated excellent stability and extraction efficiency, with rapid phase separation and a clear interface. This study offers an efficient, cost-effective, and environmentally friendly method for lithium extraction from the effluent of spent LIBs.