Solvent extraction of lithium from aqueous solution using all ionic liquid system

The vigorous development of the lithium battery industry has prompted widespread attention to the development of lithium resources. In this paper, tetrabutylphosphonium bis(2,4,4-trimethylpentyl) phosphinate ([P4444] [BTMPP]) ionic liquid was synthesized and characterized by NMR spectroscopy and FT-IR. A novel extraction system with [P4444][BTMPP] as the extractant and 1-pentyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide salt ([C5mim][NTf2]) as the diluent was constructed. The behavior of all ionic liquid for the extraction of lithium ions from aqueous solutions was investigated. The process conditions for the extraction of lithium from this binary ionic liquid system were optimized by examining the influencing factors, such as extractant mass molar concentration, temperature, and ionic strength, for the extraction of lithium from this system. The extraction experiments were carried out for the aqueous phase with different ionic strengths (I = 0.3-1.8 mol.kg-1) and temperatures (T = 293.15-318.15 K) at the optimal extractant concentration. The extraction data under different conditions were obtained, and the extraction equilibrium constants K0 for this reaction at each temperature were calculated. And, other thermodynamic parameters were calculated by polynomial fitting. The all ionic liquid extraction system laid a solid foundation for the development of green extraction technology.