A DFT investigation of the lithium extraction process under different diluent environments

The polar diluent plays an important role in the TBP-diluent-FeCl3 system for lithium recovery from salt lake brine. In this study, a DFT model considering a complicated solvent model was developed to understand the role of diluent in the lithium extraction process at the molecular level. The theoretical framework contains the main analysis items on the solvation ability, intermolecular and intramolecular interactions. The results indicate that the atomic charge of the electronegative atom in the diluent was one of the key factors influencing solvation ability. TBP had the strongest solvation ability with Li+ to form the Li(TBP)2(H2O)2+ complex, and the diluent molecule had the potential to replace the water molecule to further form the Li(TBP)2(Dil)(H2O)+ complex. In this process, both the hydrogen bond and intramolecular repulsive interaction between TBP and the diluent molecule had adverse effects on lithium extraction. The simulation results were consistent with the experimental results.