Effect of solvent on the extraction of lanthanides with picrolonic acid

Extraction of Eu(III), Tb(III) and Lu(III), as representatives of lanthanides, has been studied with picrolonic acid [1-p-nitrophenyl-3-methyl-4-nitro-5-pyrazolone (HPA)] as extractant in various solvents such as acetylacetone (ACAC), 1-octanol (ONL), n-hexanol (HNL), 1-butanol (nBNL), 2-butanol (iBNL), cyclohexanone (CHN), n-butyl ether (BE), di(1,2-dichloroethyl)ether (DCEE), diisobutylketone (DIBK), benzene and toluene from aqueous solution of pH 1-2, having ionic strength of 0.01 mol dm-3 (K+/H+, Cl-). The composition of the extracted adduct has been determined as M(PA)3 except in DCEE where it is M(PA)3.(HPA). Extraction constants (log Kex) were calculated and on the basis of log Kex, the role of diluents in the extraction process has been discussed. The solvents with respect to their extractability of the rare earth metal ions can be arranged in the order ACAC > DIBK > BE> DCEE > ONL > HNL > CHN. (orig.)