EFFECTS OF ACIDS, ANIONS AND AUXILIARY COMPLEXING SPECIES ON THE DISTRIBUTION OF BIVALENT NICKEL IN LIQUID-LIQUID EXTRACTION

Abstract

The distribution of Nickel (II) ions between two immiscible solvent medium was investigated using (H2PrETP and HPrP) in chloroform as the organic extractants. The influence of acid substances (HCl, HNO3, H3PO4, H2SO4 and CH3COOH), anions (Cl-, SO42-, NO3-, PO42-, CH3COO- and I-), and complexing agents (Br-, F-, EDTA, SCN-, (COO-)2, (CHOHCOO-)2 ) were all studied under a well defined extraction condition. Results obtained showed that Nickel (II) ions were masked in the acid medium both in single and mixed ligand extraction. Percentage extractions (% E) of metal ions were less than 10 % for all the acids at all concentrations studied. Increasing the acid concentration to 2.0M pushes the % E to zero in all cases. Various anions showed varied extraction pattern at different concentration values. The least % E was given by Cl- at 0.001 M which corresponds to 19.90 % while the anion CH3COO- gave the highest percentage extraction at 0.10 M which corresponds to 96.30 %. Increasing the anions concentrations beyond 0.10 M resulted to steady decrease in % E in most cases. No complexing agents gave up to 50 % E in the single ligand extraction. The highest % E was observed at 0.50 M of F- which corresponds to 47.74 % in the single ligand extraction. The effect of HPrP as a synergist enhanced the extraction tremendously. F- ion also gave the highest % E at 0.50 M which corresponds to 83.35 %. EDTA and Oxalate ions gave below 50 % at all their studied concentrations while F- give above 50 % E at all concentration in the presence of HPrP. Generally, anions are better extractants than the auxiliary complexing agents and the acid species. Keywords; Distribution of bivalent Nickel, effects of acids, anions and complexing agents