INTERFACIAL BEHAVIOR OF ACORGA CLX-50 AND SURFACE KINETICS OF COPPER-EXTRACTION

Interfacial tension isotherms were determined and interpreted for ACOR GA CLX-50. The hydration of extractant molecules in aqueous solution a nd at hydrocarbon/water interfaces was studied by molecular modelling. The usefulness of this technique to interpret the adsorption behavior was demonstrated. The interfacial kinetics was considered and relatio nships for various models of interfacial mechanism were derived and di scussed. Despite its high hydrophobicity, ACORGA CLX 50 strongly adsor bs at the hydrocarbon/water interfaces and thus decreases effectively the interfacial tension. This high interfacial activity of ACORGA CLX 50 can be explained by the formation of hydrates. The interfacial tens ion isotherm can be well matched with the Szyszkowski equation. Molecu lar modelling suggests that ACORGA CLX 50 adsorbs at the hydrocarbon/w ater interface probably as a tetrahydrate containing two water molecul es bonded to the same carbonyl oxygen atom (e.g., at position 3), one water molecule bonded to the oxygen atom of the second alkoxyl group ( i.e., at position 5 when the hydration of carbonyl oxygen at position 3 is previously considered) and, finally, one water molecule bonded wi th the pyridine nitrogen atom. Positions 3 and 5 are equivalent. It is also shown that when the extraction of copper takes place in the kine tic regime, the reaction order with respect to ACORGA CLX 50 can chang e depending on the limiting step and the range of extractant concentra tion considered. Thus, a decrease of the extractant concentration from 10(-5)M to 3.10(-3) M causes a fall of the order with respect to ACOR GA CLX 50 from ? to 0 and 2 to 1 when the formation of the intermediat e 1:1 and final 2:1 complexes are considered to be the limiting step, respectively.