Search

Complexation between the 2,9-dihydroxy-1,10-diphenoxy-4,7-dithiadecane (DHDPDTD) ligand and La3+, UO 2 2+ , Ce3+, and Y3+ cations has been studied by means of conductometry in acetonitrile-ethyl acetate binary mixtures over a range of temperature. Formation of the 1 : 1 complexes has been confirmed, and the complexes stability constants have been determined taking advantage of GENPLOT software. The complexes stability is affected by the metal ion nature and the solvent composition. The ligand selectivity towards metal ions depends on the solvent composition. In detail, the complexes stability decreases in the Ce3+ ≈ UO 2 2+ > Y3+ > La3+ series in pure acetonitrile at 15°C, whereas the stability series in pure ethyl acetate at the same temperature is as follows: UO 2 2+ > La3+ ≈ Y3+ > Ce3+. Standard thermodynamic parameters of the complexation reaction (Δc H 0 and Δc S 0) have been determined and found to be affected by the metal ion nature and the binary solvent composition.

The competitive metal ion transport of copper(II), cobalt(II), zinc(II), cadmium(II), silver(I), chromium(III) and lead(II) with a S-O donor compound was examined. Competitive transport experiments involving the metal cations from an aqueous source phase through an organic membrane into an aqueous receiving phase have been carried out using 5,12-di(phenoxymethyl)-1,4-dioxa-7,10-dithiacyclododecane-2,3-dione as the ionophore present in the organic phase. Fluxes and selectivities for competitive metal cations transport across bulk liquid membranes have been determined in a variety of chlorinated hydrocarbon and aromatic hydrocarbon solvents. The membrane solvents include: dichloromethane (DCM), chloroform (CHCl3), 1,2-dichloroethane (1,2-DCE), and nitrobenzene (NB) and also in chloroform-dichloromethane (CHCl3-DCM) and chloroform-nitrobenzene (CHCl3-NB) binary mixtures. Although the selectivity for silver(I) cation in all of these organic solvents is fundamentally similar, but the most transport rate for Ag(I) was obtained in dichloromethane. The sequence of transport rate for silver ion in organic solvents was: DCM > CHCl3 > 1,2-DCE > NB. A linear relationship was observed between the transport rate of silver ion and the composition of CHCl3-DCM, but a non-linear behavior was observed in the case of CHCl3-NB binary solution. The influence of the stearic, palmetic and oleic acids as surfactant in the membrane phase on the transport of the metal cations was also investigated.

The competitive bulk liquid membrane transport of Cr3+, Co2+, Cu2+, Zn2+, Cd2+, Ag+ and Pb2+ metal cations with a new synthetic sulfur donor acyclic ligand (pseudo-cyclic ionophore), i.e. 1-(2-[(2-hydroxy-3-phenoxypropyl)sulfanyl]ethylsulfanyl)-3-phenoxy-2-propanol; (C20H26O4S2), was examined using some organic solvents as membranes. The membrane solvents include: chloroform (CHCl3), 1,2-dichloroethane (1,2-DCE), dichloromethane (DCM), nitrobenzene (NB), chloroform-nitrobenzene (CHCl3-NB) and chloroform-dichloromethane (CHCl3-DCM) binary mixtures. The transport process was driven by a back flux of protons, maintained by the buffering the source and receiving phases with pH 5 and 3, respectively. The aqueous source phase consisted of a buffer solution (CH3COOH/CH3COONa) at pH = 5 and containing an equimolar mixture of these seven metal cations. The organic phase contained the acyclic ligand, as an ionophore and the receiving phase consisted of a buffer solution (HCOOH/HCOONa) at pH = 3. For these systems that displayed transport behaviour, sole selectivity for Ag+ cation was observed under the employed experimental conditions in this investigation. The amount of Ag+ transported follows the trend: 1,2-DCE > CHCl3 > DCM > NB in the bulk liquid membrane studies. The transport of the metal cations in CHCl3-NB and CHCl3-DCM binary solvents is sensitive to the solvent composition. The influence of the stearic acid, palmitic acid and oleic acid in the membrane phase on the ion transport was also investigated.