The use of surfactants in solvent extraction chemistry.

概要

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Distribution equilibria of some chelating reagents and their metal chelates have been studied between two phases (surfactant and aqueous phases) which were formed from a micellar solution of polyoxyethylene-4-nonylphenyl ether with on average 7.5 oxyethylene units (PONPE-7.5). On the basis of the distribution curves for the chelating reagents and the chelates as a function of pH, the partition constants of the reagents and the chelates were determined at 293 K and ionic strength of μ=0.1 (NaC1). The reagents were extracted not only in the uncharged form (HL) but also in the charged form probably as the type Na+L- and H<SUB>2</SUB>L+Cl-. Relatively large values of the partition constants for L- suggest that L-is extracted as an ionic associate with the Nay ion that is complexed with the ether oxygen of PONPE-7.5. The partition constant of the neutral chelates (K<SUB>D2</SUB>) depends on the kind of metal ions and is considerably smaller than those expected from the regular solution theory. These facts suggest that the chelates are incorporated into a hydrocarbon environment in the surfactant phase, whereas the reagents are distributed into the polyoxyethylene part of PONPE-7.5.
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