Interfacial activity of bis(2-ethylhexyl) phosphoric acid in model liquid-liquid extraction systems

Extraction of iron(III) from acidic sulfate solutions with bis(2‐ethylhexyl)phosphoric acid in PENRECO® 170 ES, a new friendly diluent

“…However, in a previous work it was shown that the molecules of long chain alcohols such as isodecanol compete with HDEHP for adsorption at the liquid±liquid interfaces. 23 In fact, Table 3 shows that there is indeed competition, but that the HDEHP molecules remain present at the interface, even in the presence of isodecanol at high concentration. Logically, the same phenomenon should occur when PENRECO 1 170 ES is used as a diluent and the presence of HDEHP at the interface should be not very strongly depressed.…”

“…23,29,30 Trimeric species have also occasionally been reported. 31 It is also well known that long chain alcohols often used as phase modi®ers may solvate extractant molecules and, as a result, have the tendency to depress the selfassociation of the latter in organic phases.…”

“…However, such predictions are tentative because PENRECO 1 170 ES is a complex mixture of hydrocarbons and alcohols having various degrees of branching and various lengths of alkyl chains, parameters which are known to have an in¯uence on bulk and interfacial properties in liquid±liquid systems. 23 (1) and eqn (2) to the overall process of extraction, the logarithmic plot of the distribution coef®cient of iron(III) versus the total concentration of free HDHEP (C HDEHP, free ) should lie between two straight lines whose slopes are equal to 3 (prevalence of eqn (1)) and 6 (prevalence of eqn (2)), respectively. Figure 1 shows that the plots log D Fe vs log C HDEHP, free obtained at various acidities, in the presence of an excess of HDEHP compared with the quantity of iron to be extracted, are straight lines whose slopes are equal to 3 within the limits of uncertainty.…”

Rate of Interfacial Reactions Compared to Bulk Reactions in Liquid–Liquid and Micellar Processes: An Attempt to Clarify a Confusing Situation

“…It is not clear whether this effect is to be attributed primarily to a decrease in the interfacial tension or to a fluidification of the extractant film; maybe both effects act simultaneously. In addition one can find alternative explanations in relation to specific effects of modifiers, which have been well documented (55,(60)(61)(62), such as their ability to give coassociation with extractant molecules or to coadsorb at the interface. If the addition of long-chain alcohols more or less inhibits the interfacial adsorption of extractant molecules, this will be expected to decrease the rate of metal extraction if the extractant is rejected in the organic phase, but the reverse may be true if it is rejected in the aqueous phase.…”

Los agentes de extracción del cobre. Asociaciones en la fase orgánica

“…El agua, si está presente de alguna manera en la fase orgánica, puede actuar de la misma forma, disminuyendo la asociación de las oximas. Existe otro factor que debe ser considerado al tener en cuenta la posibilidad de asociación en las oximas, tanto el grupo hidroxilo como el oximino presentan una baja acidez e hidrofilidad; por esto, las oximas con estructuras como la representada en la figura 1, no forman micelas inversas ni microemulsiones como los derivados organofosforados ácidos o los ácidos sulfónicos (17). Como ya se ha mencionado, los derivados piridínicos (Fig.5) al no presentar en su estructura áto-mos de hidrógeno lábiles, no pueden dar lugar a asociaciones intramoleculares.…”