To date, many kinds of chelating extractants have been developed, however, many of the good extractants are insoluble in aliphatic solvents. In the present study, cyclopentyl methyl ether (CPME) was assessed as a solvent for extractants to develop new solvent extraction systems. Many of the extractants (100 mM) were soluble in CPME. The extraction behavior of metal ions using a typical chelating extractant, 8-quinolinol (HQ) in CPME, was studied. The extraction profiles of metal ions using HQ in CPME were similar to those in toluene, whereas metal ions were extracted using HQ in 1-octanol and chloroform under lower pH conditions. The extraction reaction of In(III) using HQ in CPME was confirmed by slope analysis. A 3 : 1 complex between HQ and In(III) was formed in CPME by a proton exchange reaction, and the extraction equilibrium constant was determined. In(III), extracted using HQ in CPME, was quantitatively recovered using mineral acids. From the results, CPME was found to be a potential alternative solvent to other toxic organic solvents for the development of a solvent extraction system.
The ability of AMP03, a styrene–divinylbenzene copolymer functionalized with N,N,N-trimethylglycine moieties, to adsorb Pd(II) from HNO3 solutions was investigated to elucidate the affinity of N,N,N-trimethylglycine for Pd(II). AMP03 effectively adsorbed Pd(II) from 0.10–0.50 M solutions in HNO3, and the adsorption ability decreased with increasing HNO3 concentration owing to competitive adsorption of the acid. In contrast, the presence of added NO3− increased the Pd(II) adsorption ability of the copolymer. On the basis of slope analysis of data for Pd(II) and HNO3 at adsorption equilibrium, the Pd(II)/NO3−/ligand stoichiometry of the adsorbed Pd(II) species was determined to be 1 : 2 : 1. Structural studies performed by means of Fourier transform infrared spectroscopy and extended X-ray absorption fine structure spectroscopy revealed that the N,N,N-trimethylglycine moieties on AMP03 and NO3− coordinated to Pd(II) via their oxygen atoms. The adsorption selectivity of AMP03 for Pd(II), Ni(II), Cu(II), and Fe(III) was compared with the selectivities of commercially available carboxylic acid and iminodiacetic acid resins. AMP03 selectively adsorbed Pd(II) over Ni(II), Cu(II), and Fe(III) compared with that of the other resins. Our results suggest that AMP03 can be used for selective recovery of Pd(II) from HNO3 solution.
Three tridentate extractants and three masking reagents including O, N, and S donors have been developed and their properties are compared and discussed. The extractants are N,N,N′,N′-tetraoctyl-diglycolamide (TODGA), methylimino-N,N′-dioctylacetamide (MIDOA) and N,N,N′,N′-tetraoctyl-thiodiglycolamide (TDGA(C8)) together with masking agents having the same central frame but with short alkyl chains. The results of the present study indicate that TODGA can extract mainly hard acid metals belonging to groups 2-4,13-15 in the periodic table. MIDOA can extract soft acid metals and oxyanions (groups 5-10, 16), and TDGA can extract soft acid metals (groups 10-11). Some spectrophotometric studies (UV-vis., IR, and NMR) indicate the stoichiometry and the effect of donor atoms for metal-complexation. The ΔHf values, the heat generation during complex formation, obtained by chemical calculation by DFT theory show a reverse-correlation with their extraction ability.
For the separation of petroleum-derived heavy fractions by solvent extraction, the liquid-liquid equilibrium extraction of model heavy fractions, binary and multicomponent model oils, with aqueous methanol solutions was measured, and the effects of nitrogen heterocyclic and other coexisting compounds on the equilibrium extraction were studied. The distribution coefficient increased in the following order of the group compounds; alkanes, aromatics and heterocyclic compounds when the carbon numbers in the molecules of interest were same, and it decreased with an increase in the carbon number of the compound among the respective groups. The coefficients for indoles and quinolines were comparable, and those of carbazoles were smaller. The liquid-liquid equilibrium of nitrogen heterocyclic compounds with the multicomponent system was similar with that with the binary system, and the approximate trend of liquid-liquid equilibrium in the multicomponent system could be evaluated based on the results of simpler systems.