Dependence of the Pd(II) complexes extracted with N,N'-dimethyl-N,N'-ditolyl-thiodiglycolamide (MTTDGA) in chloroform on HNO₃ concentrations in the aqueous phase was investigated by liquid-liquid extraction experiments and Fourier-transform infrared spectroscopy (FT-IR) measurements. The extraction behavior of Pd(II) clearly differed between 0.5 M and 8 M HNO₃ concentrations. It took ~8 h and <5 min to attain the extraction equilibrium at 0.5 M and 8 M HNO₃, respectively. The apparent stoichiometry of MTTDGA:Pd(II) in the extracted complexes obtained from the loading test was 1:1 at 0.5 M HNO₃ and 2:1 at 8 M HNO₃. FT-IR spectroscopy results suggested that the amide oxygen atom(s) coordinated to Pd(II) in both the 1:1 and 2:1 MTTDGA:Pd(II) complexes, but the coordination mode of the MTTDGA molecule(s) differed.

An ultrasonic assisted microchannel extraction (UAME) method was developed for the extraction of Fe(III) from wet-process phosphoric acid with di(2-ethylhexyl)phosphoric acid (D2EHPA). The influences of ultrasonic power, extractant concentration, water phase velocity and the ratio of the organic and aqueous phases (O/A) on the extraction rate of Fe(III) were systematically studied. The results showed that the extraction efficiency of Fe(III) reached 91.08%, which was significantly higher than that for ultrasound extraction and microchannel extraction respectively. Response surface methodology was adopted to obtain the optimal conditions and to evaluate the significance of variables affecting the extraction efficiency. The extraction efficiency of Fe(III) reached 92.24% under the following optimum conditions: extractant concentration, 2.1 mol/L; aqueous phase velocity, 0.055 mL/min; ratio of organic phase and aqueous phase, 2.98.

The β-lactam antibiotics such as penicillin and cephalosporin account for over 65% of the market. Development of a more effective separation technique is desired to extract and purify the biologically active cephalosporin antibiotics. In this study, to recover cephalosporin antibiotics, cephalosporin C and cephalexin, an aqueous two-phase system (ATPS) composed of a water-miscible organic solvent and salts was used. For cephalosporin C extraction with the ATPS, the extent of extraction of cephalosporin C was small because of its high hydrophilicity. For cephalexin, which is more hydrophobic, it was successfully extracted with ATPS. From binodal experiments, tetrahydrofuran (THF), 1-propanol and acetone were selected as the candidates for the extraction solvent. In the extraction experiments, THF was found to be suitable because it gave the highest extractability of cephalexin and the lowest water content in the top (solvent) phase among the candidates. When the initial volume ratio of water to solvent was unity, the maximum distribution ratio was 3.13. The value of the distribution ratio increased up to 9.87 with increasing initial volume ratio. The ATPS composed of a water-miscible organic solvent and salt was found to be promising for purification of antibiotics under such mild conditions.

Amine extractants are effective for extracting precious metals in hydrochloric-acid media. We developed a novel secondary-amine extractant 2-ethylhexylfurfurylamine (EH-A-F). EH-A-F showed a higher Pd(II) extractability compared with many secondary-amine compounds, such as di(2-ethylhexyl)amine. Because the Pd(II) extraction from solutions of lower hydrochloric-acid concentration is small, Pd(II) and Au(III) can be extracted selectively from the trivalent metal ions Fe(III), Ga(III), and In(III). Because the extractability of hydrochloric acid using EH-A-F was lower than that of a competitive amine compound, benzyl 2- ethylhexylamine, EH-A-F was found to show a higher Pd(II) extractability because of its moderate basicity. Slope analysis for Pd(II) extraction showed that the complex stoichiometry was 2:1 for EH-A-F and Pd(II). The Pd(II) extracted by using EH-A-F was stripped quantitatively by using aqueous thiourea solution.

Solvent extraction is one of the efficient separation techniques for the removal of toxic chemical species from aqueous media, as well as their enrichment for microanalysis. In this study, extraction of the toxic elements, arsenic, selenium, and antimony from acidic chloride media using the oxygen-containing compounds cyclopentyl methyl ether (CPME), dibutyl carbitol (DBC), and methyl isobutyl ketone (MIBK) was compared. Extraction of As(III) increases with increasing hydrochloric acid concentration and the extractability using CPME, DBC, and MIBK was similar. On the other hand, As(V) was not extracted at all using these extractants. Sb(V) and Se(VI) were extracted at high hydrochloric acid concentration. The order of extractability for Se(IV) in acidic chloride media was MIBK > DBC > CPME. The extraction of As(III) using CPME was examined under various conditions. As As(III) was extracted only at high hydrochloric acid concentration, arsenic trichloride (AsCl₃) was suggested as the extracting species. CPME was not saturated with As(III) under the extraction conditions used in this study. As(III) can be enriched by the combination of extraction using CPME followed by back extraction using a small volume of distilled water.

In this study, we synthesized a polymer extractant and its monomer analogue, and the multifunctional effect was investigated by comparing their extraction behavior for Au(III). To increase the affinity for gold ions, we introduced a sulfur atom into the molecular structure of the extractant as a soft donor. The extraction ability of the new extractants for gold ions was influenced by the HCl concentration in the aqueous feed solution. The multifunctional effect appeared when using the polymer extractant in the liquid–liquid extraction of gold ions. Selectivity of the extractants toward Au(III) was evaluated using a model solution generated from leaching of waste cellphones. Selectivity for Au(III) was found to be enhanced by the multifunctional effect of the polymer extractant.

Separation of scandium (Sc) from yttrium (Y) in aqueous chloride media was investigated by solvent extraction with bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272). Conventional slope analysis method revealed the extraction equilibrium formulation of the metals. Sc is more strongly extracted than Y by Cyanex 272, and the separation factor of the metals is quite high at 2.82 × 10⁵. Complete stripping of Sc from the loaded organic solution of Cyanex272 could not be achieved, even with a high concentration of hydrochloric acid. Addition of 1-octanol as a modifier to the organic phase decreased the extractability of Sc, leading to successful stripping of Sc from the loaded organic solution.

We report here a hydrophobic ionic liquid (IL), 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (P14-TFSI), that contributed to increasing the amount of production of paclitaxel and the related taxanes of 10-deacetyl baccatin III, baccatin III and cepharomannine with in situ extraction from an aqueous medium in the IL-medium two phase culture system. Addition of an elicitor, methyl jasmonate (MJ) to the cell culture system enhanced the amount of production of the taxanes in the culture including 2.5 % IL. The total amount of the taxanes in the culture including 10 µM MJ and 2.5 vol% IL was more than 200 times greater than those in the control culture in the absence of IL and MJ, and more than two times greater than those in the culture including 2.5 vol% IL alone.