Abstract
The influences of extractants concentrations and solvent polarity on the efficiency of pantothenic acid separation by synergic extraction with tri-n-octylamine (TOA) and di(2-ethylhexyl) phosphoric acid (D2EHPA) mixture have been analyzed. The results indicated the formation of an interfacial compound which includes one molecule of pantothenic acid and one of D2EHPA, its hydrophobicity being increased by solvation with additional TOA molecules. For solvents with lower dielectric constants, n-heptane and n-butyl acetate, the number of amine molecules participating in the interfacial complex formation was controlled by solvent polarity and D2EHPA concentration, decreasing with the increase of these two parameters. For dichloromethane, the chemical structure of the extracted compound remained the same regardless of D2EHPA concentration. The most important synergic effect corresponded to the extractant mixture dissolved in n-heptane, at low D2EHPA concentration in the organic phase (5 g/l).
Highlights
The phenomenon of synergism was first noted in biological systems as the combined actions of two or more bioactive compounds
The results indicated the formation of an interfacial compound which includes one molecule of pantothenic acid and one of di(2-ethylhexyl) phosphoric acid (D2EHPA), its hydrophobicity being increased by solvation with additional TOA molecules
The study of separation of pantothenic acid by reactive extraction with the mixture of TOA and D2EHPA dissolved in three solvents with different polarities indicated the possibility of obtaining a synergic effect
Summary
The phenomenon of synergism was first noted in biological systems as the combined actions of two or more bioactive compounds. Translated to the extraction process, it appears when the efficiency of reactive extraction using a mixture of extractants is superior to the sum of the efficiencies of each individual extractant (Schugerl, 1994; Matsumoto et al, 2001). The synergic effect can be quantitatively described by means of the synergistic coefficient, CS, usually calculated as a function of the distribution coefficients or extraction yields (Matsumoto et al, 2001; Keshav et al, 2009; Caşcaval et al, 2012). In the case of reactive extraction with the extractants A and B, the synergistic coefficient represents the ratio between the distribution coefficients corresponding to the extractants mixture and the sum of the distribution coefficients obtained CS = DAB DA + DB (1). It was accepted that the main effect consists of the improvement of the hydrophobicity of the extracted complex produced by reaction between the solute dissolved in aqueous solution and the extractants from the or-
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