DISTRIBUTION OF IRON (II) BETWEEN BUFFERED AQUEOUS SOLUTIONS AND CHLOROFORM SOLUTION OF N,N’-ETHYLENEBIS(4- BUTANOYL-2,4-DIHYDRO-5-METHYL-2-PHENYL-3H-PYRAZOL-3- ONEIMINE)

1 Department of Chemical Sciences, Niger Delta University Wilberforce Island, PMB 71, Bayelsa State, Nigeria. Godwinj2012@gmail.com 2 Department of Pure and Industrial Chemistry, University of Port Harcourt, PMB, 5323, Port Harcourt, Rivers State, Nigeria. lydiuche@yahoo.com 3 Department of Chemical Sciences, Niger Delta University Wilberforce Island, PMB 71, Bayelsa State, Nigeria. dorathygad@gmail.com


INTRODUCTION
Solvent extraction of metal ions using Schiff bases has generated lots of interesting results over the years. The successes recorded in these studies have been utilized in the synthesis of a wide range of metal complexes with varying properties; trivalent Samarium, Europium and Gadolinium complexes of tridentate salicylidene hydrazone derivatives of 4acylpyrazolone-5 1 have shown that their solid complexes have fluorescence properties and the thiosemicarbazone 2 Schiff base derivatives exhibited biochemical 3 , photo chromic 2 and acid chromic properties due to tautomerism in their molecular structures. There are also reports of promising antitumor, antipyretic and anti-inflammatory activity of Schiff bases 3,4 . These extractions have also been successfully applied in separation of metal ions in aqueous solutions owing to varying degree of extraction of metal at different pH, in the presence of mineral acids, common anions and auxiliary complex agents 5,6 .

MATERIALS AND METHOD
All reagents and chemicals used in the study were all analytical grade from BDH and Aldrich. 4-butanoyl-2,4-dihydro-5methyl-2-phenyl-3H-pyrazol-3-one (HBuP)(figure. 1) and N,N"-Ethylenebis(4-butanoyl-2,4-dihydro-5-methyl-2-phenyl-3Hpyrazol-3-oneimine) (H2BuEtP) (figure. 2) were synthesised by method described elsewhere 7 . The ligands were recrystallized from aqueous ethanol and its purity established by elemental analysis for C, H and N. The synthesised ligand N,N'-Ethylenebis(4-butanoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-oneimine) melting point was determined with a melting point apparatus to be 234 0 C. Measurement of IR and NMR spectral data were done at the Institut fur Anorganische Chemie, Technische Universitat Dresden, Germany. Stock solutions of 0.05M H2BuEtP and 0.05M 4butanoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one (HBuP) were prepared by dissolving appropriate mass of the ligands in CHCl3. The concentration of Fe(II) in the aqueous phase was determined colorimetrically with a UV spectrophotometer (Spectronic 20 Genesys) at wavelength of 520nm 5 . The colour development for Iron(II) determination was by addition of 0.1ml of hydroxylamine hydrochloric acid, 0.5ml of 1,10-phenathroline and 0.5ml of sodium acetate. Fe(II) ion concentration extracted into the organic phase was determined from the difference between the concentration of Fe(II) ion in aqueous phase before and after the extraction. Distribution ratio D was calculated as the ratio of metal ion concentration in the organic phase (Co) to that in the aqueous phase (C). Thus D = Co/C.

RESULTS AND DISCUSSION
The addition of H2BuEtP organic phase to the aqueous phase containing Fe(II) at pH range of 8.00 -8.25 resulted in the immediate formation of a purple coloured solution. This was not observed at other pH and indicates that at these 8.00 -8.25 pH range, coloured Fe complex species formed. The coloured Fe complex with H2BuEtP can be evaluated for use as a colorimetric reagent for Fe analysis. The presence of ligand H2BuEtP alone, plots of log D against pH shown in figure 3 had a slope of 2, indicating that two hydrogen ions where displaced during the extraction reaction.  ]). Substitution into equation (2) gives:

Log D 1 = log K ex1 + log[H 2 BuEtP] + 2pH (3)
The The extraction parameters were similar to those obtained for the extraction of Ni 2+ ion with this ligand H2BuEtP as reported 8 , indicating that similar mechanism might be involved in their extraction mechanisms. However, even though their pH1/2 values are close (pH1/2Fe = 7.24 ± 0.10 and pH1/2Ni = 7.14 ± 0.10), comparing other extraction parameters with those of Ni 2+ (Log KexNi = -12.39 ± 0.64 > Log KexFe = -13.45 ± 0.2 and Log DNi = 1.89 ± 0.05 > Log DFe = 1.5 ± 0.16) showed that Ni 2+ distributed better than Fe 2+ in the presence of this ligand H2BuEtP. The optimal pH for the extraction of Fe(II) with the ligand H2BuEtP was 8.25 at which a 97.59% extraction of Fe(II) was achieved. However, it was observed that the pH range at which quantitative extraction occurred was very narrow (7.5 -8.5). It is noteworthy to state that the mechanism of extraction of Fe(II) and Ni(II) is different from that observed in the extraction of Pb(II) and U(VI) with the same ligand. In the distribution of Pb(II), it was observed that the extracted complex was proposed as ion pair tris complex species with a wide pH range (5.9 -8.0) at which quantitative extraction occurred 9 . In the case of U(VI), it was observed that anions from buffer reagents might have played a part in the formation and hydrophobicity of the extracted complex. The pH range at which quantitative extraction occurred was also wide (5.5 -8.25) 10 . The partition coefficient KD1 for Fe(II) compared with those gotten for the other three metal ions Ni(II), Pb(II) and U(VI) in similar studies with the same ligand H2BuEtP indicated that U(VI) was the least extracted into the oganic phase, while Pb(II) was the most extracted; Log DU(VI) = 0.56 ± 0.11 < Log DFe(II) = 1.5 ± 0.16 < Log DNi(II) = 1.89 ± 0.05 < Log DPb(II) = 1.92 ± 0.25.
Iron ions have been shown to form strong and weak bonds with nitrogen atom in ligands in their formation of complexes 12,,13 . Combining slope analysis results from figure 3, figure 4, figure 6 figure 3 to be equal to 1.68 ± 0.18. Log Kex2 was calculated from equation 6 to be -13.27 ± 0.54 and the pH1/2, determined from figure 3 to be 7.13 ± 0.10. These results were not significantly different from those obtained with the ligand H2BuEtP alone even though they are slightly better; KD2H2BuEtP/HBuP = 1.68 ± 0.18 > KD1H2BuEtP = 1.5 ± 0.16; Log Kex2H2BuEtP/HBuP = -13.27 ± 0.54 > Log Kex1H2BuEtP = -13.45 ± 0.2. The pH1/2 was slightly reduced from 7.24 ± 0.10 in ligand H2BuEtP alone to 7.13 ± 0.10 in mixed ligands (H2BuEtP/HBuP) organic phase. The pH range at which quantitative extraction occurred was still narrow (7.25 -8.25). However the optimal pH at which maximum extraction was achieved was slightly reduced from 8.25 in ligand H2BuEtP alone to 8.0 in mixed ligands (H2BuEtP/HbuP) organic phase.
The distribution of Fe(II) in the mixed ligands organic phase was lower than those obtained for U(VI), Pb(II) and Ni(II) with the same mixed organic phase; Log KDfe = 1.68 ± 0.18 < Log KDu = 1.74 ± 0.20 < Log KDPb = 1.82 ± 0.22 < Log KDni = 1.89 ± 0.02. The combined results for the so far studied four metals with this same mixed ligands organic phase indicated that Mar c h 2 4 , 2 0 1 3 while quantitative extraction of Fe(II) occurred only above the neutral pH region (7.75 -8.00), the other three previously studied metals were quantitatively extraction over a wider range, stretching from the acidic pH region to the alkaline pH regions Ni(II) (6.0 -9.0); Pb(II) (5.75 -8.00) and U(VI) (3.75 -7.25) 8,9,10 . This could be exploited in the separation of Fe(II) from Ni(II), Pb(II) and U(VI) in aqueous phases using the mixed ligands (H2BuEtP/HbuP) organic phase.
Analysis of data showed that extraction involving a mixture of the ligands probably gave a protonated mixed ligand Fe(II) complex species. The suggested Iron complex species is shown in figure 8 having Fe-N bonds. The formation of the adduct complex Fe(HBuEtP).BuP(o) resulted in increased distribution of Fe(II) into the organic phase due increased hydrophobicity and reduced polarity of the complex compared to the complex Fe(BuEtP) formed in the ligand H2BuEtP alone organic phase

CONCLUSIONS
The ligand H2BuEtP has potentials for use as a colorimetric reagent for the analysis of Fe.
The ligand H2BuEtP can be used as an organic extractant for Fe(II) extraction from an aqueous solution, alone or in a mixed ligands organic system containing HBuP.
The optimal pH for extraction of Fe(II) with the ligand H2BuEtP alone and mixed ligands (H2BuEtP and HBuP) organic phase was 8.25 and 8.00 respectively.
Though the calculated extraction parameters showed that the ligand HBuP slightly improved the distribution of Fe(II) into organic phases, the synergistic effect of HBuP in the extraction of Fe(II) with H2BuEtP was not significant.
Slope analysis showed the extracted Fe complex species in both type of organic phases were Fe(BuEtP)o and Fe(HBuEtP)BuPo respectively.