Distribution Of Pb (II) Ions Into CHCl3 Solution Of N,N’- Ethylenebis(4-Butanoyl-2,4-Dihydro-5-Methyl-2-Phenyl-3HPyrazol-3-Oneimine) As Tris-Complex Species

Abstract

A study of the distribution of Pb(II) from aqueous media into chloroform solution of N,N'- ethylenebis(4-butanoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-oneimine) H2BuEtP and its mixture with (4-butanoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one) HBuP has been carried out. The pH½ of extraction of Pb(II) was slightly lowered from pH 5.88 ± 0.14 to 5.51 ± 0.13 when a mixture of the ligands was used. The physico-chemical properties were determined and the following values were recorded: partition coefficient (log KD) 1.92 ± 0.25 (H2BuEtP) and 1.82 ± 0.22 (H2BuEtP-HBuP); extraction constant (log Kex) - 32.90 ± 0.07 (H2BuEtP) and -9.79 ± 0.10 (H2BuEtP-HBuP). Data analysis indicated that Pb(II) complexes distributed more effectively into chloroform solution of H2BuEtP than into a solution of its mixture with HBuP, attributed to Pb(II) being extracted as the ion-pair tris-complex species Pb(BuEtP)(BuEtP)2 4- .4H + . Protonated Pb(HBuEtP).BuP species were extracted into organic solution mixture of the ligands. Extraction of Pb(II) from mineral acids, show that apart from sulphuric acid extraction is generally very poor, even when a mixture of H2BuEtP and HBuP was used. However a mixture of the ligands is observed to be more effective in the extraction of Pb(II) from solution of anion than when H2BuEtP is used alone. EDTA solution completely masked.the extraction of Pb(II) into organic solutions. Keywords- acids, anions, extraction, lead(II), N,N'-ethylenebis(4-butanoyl-2,4-dihydro-5-methyl-2-phenyl-3H- pyrazol-3-oneimine) I. Intrduction Derivatives of 1-Phenyl-3-methyl-4-acyl-pyrazolone-5 are known for their complexation reactions with transition metals forming metal complexes with interesting coordination chemistry (1-4). In continuation of our work on the synthesis and characterization (5) of derivatives of 1-phenyl-3-methyl-4-acylpyrazolone-5 we report the application of a Schiff base derivative of 4-butanoylpyrazolone as a potential extractant for metal ions. The synthesis provided an opportunity for a N=C-C-OH bonding moiety and extended the scope of coordination to involve tetradentate ligands from the initial bidentate 4-acylpyrazolone. Application of Schiff bases in selective adsorption of Yb(III) in the midst of a range of transition metal ions such as Eu(III), Gd(III), Nd(III), Tb(III) etc on a silica surface has been reported (6). Earlier studies on isolation and characterization of metal complexes of Schiff bases have shown that they are capable of forming stable metal complexes (7,8) with Cu(II) and Ni(II) and unstable metal complexes with Mo(VI), Co(II) and Cd(II). In this study the solvent extraction of lead(II) ions from aqueous media using N,N-ethylenebis(4- butanoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-oneimine) was investigated. Extraction of metal ions with Schiff base derivatives of 4-acylpyrazolone has attracted little or no attention in the literature. Thus the effect of pH, acids, anions and auxiliary complexing agents on the extraction of Pb(II) from aqueous solutions was investigated. The aim of the study was to see if there is a role played by the ability of Pb(II) to form both Pb-O and weak Pb-N bonds (9-10) in the extraction process.