FT-IR study of the coordination of an organophosphonic acid with lanthanide ions

The coordination interaction between saponified 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEHEHP) with lanthanide ions [Ln(III)] in an extracted organic phase has been studied by FT-IR spectral analysis. The result indicates that with the increase of lanthanide loading in the organic phase, the microstructure of the water/oil microemulsions formed by the saponified extractant is gradually destroyed. The P=O group of the extractant was found to coordinate with the Ln(III). The coordination ability of the lanthanide series with the P=O group was found to increase from La(III) to Pr(III), but decrease from Pr(III) to Lu(III).