Abstract

The extraction of Ni(II) ions in aqueous media was studied using chloroform solution of N,N’-ethylenebis(4-butanoyl-2,4-dihydro-5-
methyl-2-phenyl-3H-pyrazol-3-oneimine) (H2BuEtP) Schiff base as the organic extractant. The synergistic effect of 4-butanoyl-2,4-
dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one (HBuP) in these extractions were also investigated. The pH½ of extraction of Ni(II) was
significantly lowered from a near neutral pH 7.14 ± 0.10 to an acidic region of 5.51 ± 0.10 when a mixture of the ligands was used. The
partition coefficient (log KDNi1) 1.89 ± 0.05 (H2BuEtP) was same as (log KDNi2) 1.89 ± 0.02 (H2BuEtP-HBuP) while the extraction constant (log KexNi1) -12.39 ± 0.64 (H2BuEtP) was slightly less than (log KexNi2) -10.57 ± 0.10 (H2BuEtP-HBuP). Data analysis indicated that Ni(II) distributed slightly better into chloroform solution of H2BuEtP/HBuP as Ni(HBuEtP)(BuP)(o) than into a solution of H2BuEtP as Ni(HBuEtP)2(o) . Mineral acids show a masking effect in the extractions in both ligand alone and mixed ligands systems while mixed
ligands system was shown to be a better extractant system for Ni(II) ions in the presence of anions and auxiliary complexing agents studied. Acetate, fluoride, and phosphate ions gave the best percentage extractions and the extraction of Ni(II) ions with the ligand is more efficient at near neutral to basic pH.

Key words: Extraction, Nickel(II), N,N’-Ethylenebis(4-butanoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one imine), Effect of pH and anions