Extraction of strontium with dicarbolide in the presence of polyethylene glycol

Abstract

The extraction of microquantities of 85Sr in the presence of 3 . 10-4 - 0.25 mol l-1 polyethylene glycol (PEG 400) (L) with solutions of dicarbolide ({(π-(3)-1,2-B9C2H11)2Co}-) in nitrobenzene (10-3 - 10-2M) was investigated. The occurrence of the maxima (up to one order of magnitude) on the plots of the strontium distribution ratio vs the total PEG concentration was explained in terms of the competition between the charged strontium-PEG complex (SrL2+) and protonized PEG (HL+) during the balancing of the dicarbolide electrostatic charge in the organic phase. Theoretical relations were derived for the shape of this dependence, for the effect of the acid concentration in the aqueous phase and that of the dicarbolide concentration in the organic phase, as well as for the positions of the corresponding maxima. The theoretical dependences are in accordance with the experimental data. The values of the concentration equilibrium constants of the reactions Sr2+ + L + 2 H+ ##e SrL2+ + 2 H+ (Kex(SrL2+)) and H+ + L ##e HL+ (Kex(HL+)) (for variable ionic strength) are Kex(SrL2+) = 3.26 . 108 and Kex(HL+) = 538 at 25 °C.