Solvent Extraction Studies of Uranium (VI) from Aqueous Media into Chloroform Solution of N,N´-ethylenebis(4-propionyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-oneimine)

Abstract

The extraction of Uranium (VI) from aqueous media of varying pH values (0.3 – 9.0) was studied using chloroform solution of 0.05M N,N`-ethylenebis(4-propionyl-2,4-dihydro-5-methyl-2-phenyl-3H- pyrazol-3-oneimine) (H2PrEtP) Schiff base. The effect of 4-propionyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one (HPrP) as a mixed ligand in these  extractions  was  also  studied.  The ligand H2PrEtP was shown to behave in solution as a very weak acid with potentiometrically determined acid dissociation constants pKa of 6.1±0.1 and 7.6±0.1. Colorimetric method was used to determine the Uranium(VI)  concentrations  in  aqueous  media  after  extraction processes. Slope analysis showed that the extracted uranyl complexes were UO2(HPrEtP).X in the absence of the mixed ligand (H2PrEtP/HPrP) and UO2(HPrEtP)HPrP.X in the presence of HPrP as a mixed ligand, with the excess anion X- coming from the buffers. The pH1/2 shifted from 6.9 ± 0.10 for H2PrEtP to 4.4 ± 0.10 for H2PrEtP/HPrP organic mixture. Though, log Kex values (-5.84 ± 0.18 log Kex H2PrEtP) > -8.71 ± 0.50 log Kex H2PrEtP/HPrP) indicated that the formation constant for UO2(HPrEtP).X was higher than that for UO2(HPrEtP)HPrP.X. Thus, the mixed ligand organic phase was shown to be a better extractant for Uranium(VI) with a wide extraction pH range of 4.0–6.5, a higher partition coefficient(KD) of 2.49 and quantitative extraction of 99.9% compared to extraction pH range of 7.75 – 8.75 and KD of 1.49 when H2PrEtP was used alone.