Synergistic Effect in the Solvent Extraction and Separation of Lanthanoids by 4-(4-Fluorobenzoyl)-3-methyl-1-phenyl-pyrazol-5-one in the Presence of Monofunctional Neutral Organophosphorus Extractants

Abstract

4-(4-Fluorobenzoyl)-3-methyl-1-phenyl-pyrazol-5-one (HL) has been synthesized and its complexation properties in solution were examined. Mixed ligand chelate extraction of trivalent lanthanoids (La, Nd, Eu, Ho, and Lu) from chloride medium at constant ionic strength μ = 0.1 into C6H6 with HL in combination with one of the three phosphine oxide compounds trioctylphosphine oxide (TOPO), tributylphosphine oxide (TBPO), or triphenylphosphine oxide (TPPO) as well as with tributylphosphate (TBP) was studied. The interaction between the extractants in C6H6-d6 has been studied by 1H, 13C, and 31P NMR spectroscopy and its influence on the synergistic extraction of Nd(III) ion has been investigated. The composition of the extracted species was established as LnL3·HL with HL alone and as LnL3·2S in the presence of TOPO, TPPO, and TBP or LnL3·S with the mixture of HL–TBPO. A synergic effect up to 106 was observed for the extraction of the above-mentioned lanthanoid ions with binary mixtures of extractants. The change of the synergistic agent causes a significant increase of the KL,S values. The parameters of the extraction process were determined and the separation factors were calculated.