SOURCE:

Faculty: Physical Sciences
Department: Pure And Industrial Chemistry

CONTRIBUTORS:

Nwadire, F.C;
Ajiwe, V.I.E;
Okoye, P.A.C;

ABSTRACT:

Liquid – liquid extraction of Ni(II) Co(II) and Cu(II) ions from buffered solution into N,N1 -ethylenebis (4-propionyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one) imine (H2PrEtP) Schiff base as a function of pH and concentration of solution was investigated. The synergistic effect of 4-propionyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one (HPrP) have all been investigated and optimized. Effects of complexing species alongside anionic substances and certain mineral and organic acids were all investigated (for nickel(II) and cobalt(II) under a well-defined extraction conditions. The various effect of these reagents and experimental conditions on nickel(II), cobalt(II) and copper(II) ions extraction. About 99 % of nickel(II) was extracted between pH 6.0 to pH 9.0. The extraction of cobalt gave about 99 % between pH 7.5 to pH 9.5, while copper was quantitatively extracted in acidic pH of 3.0 to pH 6.5 where highest percentage extraction 98.23 % was observed at pH 6.1 in a mixed ligand system of H2PrEtP and HPrP in the ratio 9:1 by volume. In the extraction of nickel and cobalt, increase in pH above 9.0 and 10.0 resulted in a steady decrease in the extraction while increase in pH above 8.0 resulted to decrease in the percentage extraction of copper. The addition of HPrP as a synergist in the extraction of these three metals not only increases the percentage extraction from 62.45 % at pH of 5.75 (pH 1/2) to 99.14 % at pH 7.25 (pH max) for nickel, 52.60 % at pH 6.25 (pH1/2) to 99.30 % at pH 8.26 (pH max) for cobalt and 50.25 % at pH 3.0 (pH1/2) to 98.23 % at pH 6.10 (pH max) for copper but equally shifted the extraction pH to a more acidic region thus making way for quantitative extraction of these metals at a slightly acidic pH as seen in nickel and cobalt and higher acidic pH as in the case of copper. Studies carried out with varied metals’ concentrations in aqueous medium showed that the extractions of the metal ions from solutions are independent of their concentrations in solution with nickel having highest extraction of 98.7 % at 4.77×10-4 M and 5.10×10-4 M respectively in a mixed ligand extraction while cobalt and copper gave highest percentage extraction of 98.52 % at 4.75×10-4 M and 97.43 % at 3.46×10-4 M respectively. All studies on chelating agents H2PrEtP and synergist HPrP showed that increase in their concentrations resulted into increase in the percentage extraction of nickel, cobalt and copper. Nickel gave maximum extraction of 99.50 % at 4.0×10-2 M H2PrEtP concentration while cobalt gave 97.20 % at 3.0×10-2 M H2PrEtP concentration all in the presence of HPrP. Of all the mineral acids and the organic acid studied non formed extractable complex with Ni(II) and Co(II) ions. Increasing the concentration of the various acids beyond 2.0 M pushed the percentage extraction to zero except in H2SO4, H3PO3 and CH3COOH where a negligible extraction of 4.80 %, 5.30 % and 5.60 % was obtained at dilute concentration of 0.01 M for H3PO4 and H2SO4 and 0.50 M for CH3COOH for nickel and 6.09 % (H3PO4), 8.09 % (H2SO4) and 7.67 % (CH3COOH) for cobalt. Anions and complexing agents showed different behaviors at different pH values and concentrations. CH3COO- at pH value of 7.95 and concentration of 0.10 M gave the highest percentage extraction of 96.30 % in the mixed ligands system while the least extraction was given by Cl- at pH of 5.65 and concentration of 0.00 M corresponding to 19.90 % E in single ligand (H2PrEtP) extraction for nickel. Cl- in single ligand at 1.00 M gave least extraction of 35.61 % for cobalt while PO42- in mixed ligand gave highest extraction of 92.06 % at 0.10 M for Co(II). For complexing agents the highest extraction was observed in Br- at pH value of 6.07 and concentration of 0.10 M which corresponds to 71.30 % E while EDTA gave the least extraction at pH value of 5.12 and concentration of 0.10 M where 21.60 % extraction was obtained in a single ligand system for nickel. F- in mixed ligand gave highest extraction of 83.35 % for cobalt while oxalate in single ligand gave the least 19.80 % E for Co (II). Generally anions gave a better extraction of the metals than the complexing species.