Solvent Extraction Studies of Uranium (VI) fromAqueous Media into Chloroform Solution ofN,N?′-ethylenebis(4-propionyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-oneimine)

摘要

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) (H_(2)PrEtP) 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 H_(2)PrEtP was shown to behave in solution as a very weak acid with potentiometrically determined acid dissociation constants pK_(a) 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 UO_(2)(HPrEtP).X in the absence of the mixed ligand (H_(2)PrEtP/HPrP) and UO_(2)(HPrEtP)HPrP.X in the presence of HPrP as a mixed ligand, with the excess anion X- coming from the buffers. The pH_(1/2) shifted from 6.9 ± 0.10 for H_(2)PrEtP to 4.4 ± 0.10 for H_(2)PrEtP/HPrP organic mixture. Though, log K_(ex) values (-5.84 ± 0.18 log K_(ex) H_(2)PrEtP) > -8.71 ± 0.50 log K_(ex) H_(2)PrEtP/HPrP) indicated that the formation constant for UO_(2)(HPrEtP).X was higher than that for UO_(2)(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(K_(D)) of 2.49 and quantitative extraction of 99.9% compared to extraction pH range of 7.75 – 8.75 and K_(D) of 1.49 when H_(2)PrEtP was used alone.