To date, suitable organic solvents for the extraction of tetravalent selenium (Se(IV)) in highly concentrated hydrochloric acid have not been clarified systematically. In this study, the extraction of Se(IV) using various organic solvents was compared. Se(IV) was extracted from 8.0 mol/dm³ hydrochloric acid using various ketones. Se(IV) extraction using ethers was lower, while that using hydrocarbons was negligible. The correlation between the extraction and logP value of solvents was small, however, the extraction using a hydrophobic dicyclohexyl ketone was lower. The extractability of Se(IV) by most solvents can be classified with the Hansen solubility parameters of the solvents. However, Se(IV) extracted by 2-nonanone was not stripped by contact with fresh aqueous solutions containing HCl, HNO₃, NaOH, or EDTA.

The zwitterionic surfactant 3-(nonyldimethylammonio)-propyl sulfate (C₉-APSO₄) exhibits unique reversible temperature-dependent phase separation properties, which can be used for the extraction of watermiscible negatively charged gold nanoparticles (AuNPs) without any aggregation at high concentrations using only temperature change. This study investigated the extraction behaviors and properties of AuNPs transferred from the water phase to a small volume of the surfactant-rich phase. The AuNPs retained both their original shapes and sizes after temperature-dependent phase separation step. In addition, the concentration of AuNPs was enriched by a factor of 150 in the surfactant-rich phase without any changes in the sizes and shapes of AuNPs. The capacity was 63.7 μg (Au) present in 10 μL of the surfactant-rich phase (i.e., the saturated concentration was 1.6 × 10¹² particles/mL for 60 nm AuNPs). Furthermore, the extraction percentage was greater than 99% regardless of the pH (in the pH range of 2 – 12).

NTf₂^--based ionic liquids (ILs)/tri-n-butyl phosphate (TBP) systems can be used for extraction of Li⁺, but ILs are very expensive and their cations can cause the contamination of the aqueous phase in the extraction process. In this study, an inexpensive raw material lithium bis(trifluoromethanesulphonyl)imide (LiNTf₂) is used to prepare extraction organic phase NaNTf₂·TBP, which can avoid the contamination of the aqueous phase in the extraction process. The preparation conditions of extraction organic phase NaNTf₂·TBP were investigated. The extraction conditions of NaNTf₂·TBP system were also studied, and under the optimal extraction condition, the single extraction efficiency of Li⁺ is 91.7%. The extraction system is stable after seven extraction cycles, and it has good prospects for application in extraction of Li⁺ from brine with a high Mg/Li ratio.

Continuous extraction process of 5-hydroxymethylfurfural (HMF) in the liquid-liquid slug flow of water/methyl isobutyl ketone (MIBK) formed in the microcapillary was examined under hydroperoxide (H₂O₂) as a reactive oxygen species (ROS). Addition of H₂O₂ reduced the extracted amount of HMF into the MIBK phase. However, the addition of hemin recovered the HMF extraction. This probably resulted from the competitive binding of H₂O₂ and HMF to hemin. The binding of hemin to H₂O₂ and HMF contributed to anti-ROS activity and an accelerated mass-transfer of HMF, respectively.

The application of wet-process phosphoric acid in fertilizer is limited due to the excessive Fe³⁺ concentration. In this paper, a fundamental investigation on the removal of Fe³⁺ from phosphoric acid with P-15 extractant is conducted. First, effects of several parameters on the extraction rate such as extraction temperature, P-15 concentration, phase ratio O/A on Fe³⁺ extraction are carefully investigated. The composition of the extract was verified by slope method and saturation capacity method. Then, the kinetic and control mechanism of the extraction reaction is studied by constant interface cell. The extraction reaction rate equation was obtained by the initial rate method. The calculated activation energy of overall reaction is 15.4 kJ·mol⁻¹ and the change of enthalpy ∆H = −4.19 kJ·mol⁻¹ of Fe³⁺ is measured by automatic calorimeter.

Lactic acid is the raw material for polylactic acid, a biodegradable plastic, which is produced by fermentation. Development of a cost-effective separation technique is still required to extract and purify lactic acid from the broth. We conducted permeation of lactic acid and acetic acid through supported ionic liquid membrane containing Cyphos IL 101 as a carrier. Lactic acid successfully permeated through the membranes against its concentration gradient. By using a feed phase of pH 5 and a receiving phase of 0.01 mol/dm³ NaCl solution prepared at pH 3 with HCl, a higher permeation rate of lactic acid and a higher separation of lactic acid and acetic acid could be achieved than when the receiving phase was a HCl solution.