Synergistic extraction of Eu(III) with mixture of picrolonic acid and neutral organophosphorous extractants

Synergistic extraction of Eu(III) has been studied with a mixture of picrolonic acid (HPA) and neutral organophosphorous extractants; trioctylphosphine oxide (TOPO), triphenylphosphine oxide (TPPO) and tributylphosphate (TBP) in chloroform separately, from aqueous solution of pH 1-2, having ionic strength of 0.1 mol dm(-3) (K+/H+, Cl-). Highest extraction (a parts per thousand yen99 %) was achieved at pH 2 within five minutes using all the three mixtures. Composition of the extracted adduct has been determined as Eu(PA)(3)center dot 2TOPO, Eu(PA)(3)center dot 2TPPO and Eu(PA)(3)center dot TBP. The equilibrium constants (logK(Mix)) for Eu(III) were calculated to be 4.54 +/- A 0.03, 5.69 +/- A 0.06 and 6.17 +/- A 0.04 using 0.01 mol dm(-1) mixture of HPA and TBP, TPPO and TOPO respectively. Highest extraction was observed with HPA-TOPO, followed by HPA-TPPO and least with HPA-TBP mixture. Order of extraction becomes TOPO > TPPO > TBP. Separation factors for various metal ions have also been calculated and it is found that Eu(III) can be separated quantitatively from divalent metal ions. Pronounced synergism was observed in the range of 10(3)-10(4) when the europium was extracted with the mixture of these extractants.