Extraction of Sm(III), Gd(III) and Ho(III) ions with picrolonic acid in methylisobutylketone

Abstract

Picrolonic acid (HPA) in methylisobutylketone (MIBK) (0.01 mol. dm-3) has been used for the extraction of lanthanide(III) ions such as Sm(III), Gd(III) and Ho(III) (Me) (~3. 10-6mol. dm-3) from pH 1-2 buffer solutions of 0.1 mol. dm-3(H+, Cl-) ionic strength and quantitative extraction (>95%) was found at pH 2. Through slope analysis the composition of the organometallic adduct responsible for the extraction came out to be M(PA)3. The conditional equilibrium constant values, log Kex, were deduced to be 2.60±0.01, 2.09±0.01 and 1.44±0.03 for these lanthanide(III) ions, respectively. The metals in concentration up to ~2.5. 10-4mol. dm-3can be quantitatively extracted by the proposed system. Among the various anions, fluoride, oxalate and cyanide ions (~3.0. 10-4mol. dm-3) and, among the cations, Zn(II) Cu(II), Co(II) and Fe(III) reduced the lanthanide extraction. The extraction of various other metal ions at the optimized conditions of Me extraction for this series of lanthanide ions was also studied and high separation factors (102-103) were obtained showing the good selectivity of this extraction system.