Mechanism study on the synergistic effect and emulsification formation of phosphine oxide with β-diketone for lithium extraction from alkaline systems

Abstract

• More accurate synergistic mechanism of β-diketone and phosphine oxide for lithium extraction was confirmed. • The extraction species of Li(H 2 O)·TTA·TOPO was determined by the synergistic system. • The reasons for the ready emulsification formation was analysed. • Possible measure to solve the emulsification problem was proposed. The synergisms of β-diketone and phosphine oxide are very efficient for lithium selective extraction from alkaline systems, and have been obtained wide applications, especially for lithium recovery from salt lake brines. However, the systems are ready to form emulsification which seriously impacted their practical applications. In this study, the synergistic mechanism of β-diketone and phosphine oxide was intensively studied using a typical β-diketone of HTTA (2-Thenoyltrifluoroacetone) and TOPO (Trioctylphosphine oxide) through extraction parameter relationships, FT-IR measurements, structure computational simulations. It is found that one molar water readily presented in the extracted species forming Li·(H 2 O)·TTA·TOPO, while two molar water presented when HTTA alone was used which more readily forms emulsification or even solid. When TOPO was attended, one molar of water was replaced by it as there is an unconfirmed “boundary“ formed between them which will significantly mitigate the emulsification formation.