A New Method for Studying the Extraction Kinetics with Monitoring of the Organic Phase Properties by Attenuated Total Reflection IR Spectroscopy

The kinetics of europium and yttrium extraction with mono- and polyfunctional ligands in organic diluents was studied by attenuated total reflection IR spectroscopy and a method using a diffusion cell. The extraction rate is influenced by the kind of the ligand, solvate formation mechanism, and specific features of diffusion. The extraction rate constants in the systems studied were calculated. In the extraction of europium with organophosphorus ligands, the extraction rate constants range from 3.3 × 10–4 to 1.1 × 10–3 cm s–1. A stepwise complexation mechanism with polyfunctional ligands containing P=O and C=O groups was revealed. In the case of yttrium extraction, the extraction rate constant with a mixed extractant, 2,3-dihydroxynaphthalene + methyltrioctylammonium carbonate, is 1.5 × 10–3 cm s–1, which is higher by an order of magnitude than the rate constant obtained with 8-hydroxyquinoline (k = 4.3 × 10–4 cm s–1), owing to a synergistic effect.