Lithium has been a high-demand element with the rapid development of lithium-ion batteries. The recovery of lithium from salt lake brine via solvent extraction is considered a promising technique. In this study, the solvent extraction process in the tributyl phosphate (TBP)−FeCl 3 /brine system was investigated. The order of metal ions competitively combining with TBP−FeCl 3 was Li + > Na + > K + > Mg 2+ , and the compositions of main cationic extraction complexes were Li(TBP+ , and Mg(TBP) 2 (H 2 O) 4 2+ , respectively. The energy decomposition analysis showed that the electrostatics was the major interaction between the metal ions and the solvent (TBP and water). Compared with water, TBP bound more competitively with the metal ions. The calculated species distribution results showed that the ferric ion reacted with the chloride ion to form FeCl 2 + , FeCl 3 , and FeCl 4 − in high Cl − concentration brine. Co-extractant FeCl 3 was found to exist in the organic phase in the form of FeCl 4 − upon comparing the experimental and simulated spectra. Furthermore, the length of the Fe−Cl bond increased and the charge on the iron element was distracted when the FeCl n 3−n complexes coordinated with the water molecules. This indicated that FeCl 4− was more stable in the TBP solvent environment and it can be extracted from the aqueous phase. The results help us understand the extraction mechanism in essence and develop a high-efficiency extraction solvent for industrial lithium recovery.

A bubble generator is a crucial component in the flotation system, and the bubble size is directly related to bubble mineralization. This paper focused on the microbubble size control of a swirl flow microbubble generator. The computational fluid dynamics coupled population balance model (CFD-PBM) was developed to evaluate the flow characteristic and the bubble generation performance of the microbubble generator with five novel internal baffles. The results showed that the baffle could improve the bubble dispersion without extra energy loss, and the single helical baffle could generate tiny bubbles with a Sauter mean diameter of 0.36 mm at a liquid flow rate of 2000 L/h. The baffle could limit the positive axial velocity and hinder the tangential velocity effect in the straight pipe section, weakening the swirl flow effect. Hence, although the baffle slightly reduced the pressure gradient magnitude and the turbulent intensity, it still presented an effective improvement in the bubble dispersion.

The solid–liquid-phase equilibria of quaternary system K+, Mg2+, Na+//Cl––H2O and its three ternary subsystems K+, Mg2+//Cl––H2O; Mg2+, Na+//Cl––H2O; and K+, Na+//Cl––H2O at 278.15 and 288.15 K were studied by an isothermal solution equilibrium method. The quaternary system K+, Mg2+, Na+//Cl––H2O includes two invariant points, five univariant curves, and four crystallization regions. The double salt KCl·MgCl2·6H2O is found in the quaternary system but no solid solution. Based on the experimental results and the multitemperature comparison, the order of the solubilities of the single salts is KCl < NaCl < MgCl2 within a certain temperature range. As the temperature decreases from 288.15 to 278.15 K, all of the solubilities of KCl, MgCl2·6H2O, and NaCl decrease. The dissolution of MgCl2 and NaCl can affect the crystallization of KCl. From a thermodynamic point of view, low temperatures are beneficial to the crystallization of potassium chloride from the system. Therefore, it is important to control the low operating temperature, low concentration of NaCl, and high concentration of MgCl2 in the production process. The data obtained in this work have important implications for the design and optimization of the production process of potassium chloride from K-carnallite in low-temperature conditions.

In this study, the mechanism of lithium extraction with β-diketones was investigated by resolving the reaction mechanism, thermodynamic property, and molecular interaction through density functional theory approach. Before the selective extraction of lithium, the β-diketones had tautomerism with the product of enol. The enol struc-

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