The Role of Some Commom Anions in the Multi-Metal Extraction Using 4,4´-(1E,1E´)-1,1´-(Ethane-1,2-Diylbis(Azan-1-YL-1Ylidene))Bis(5-Methyl-2-Phenyl-2,3-Dihydro-1H-Pyrazol-3-OL) (H2BuEtP)

Abstract

The roles of CH₃COO^-, PO₄^3-, and SO₄^2- in the multi-metal extraction of Cadmium (II), Iron (II), Lead (II), and Nickel (II) from aqueous solutions buffered to pH 4.75 and 7.5 were studied using ligand H₂BuEtP alone and in the presence of another ligand 4-butanoyl-2-4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one (HBuP) in chloroform organic phases using solvent-solvent extraction methods using 2 batches of extractions based on theoretically number of batches needed to achieve 99.9% extractions of the four metals from single metal extractions studies with same organic phases. 50 mgL^-1 each of the four metal in 2 mL aqueous solutions containing 0.001 M – 0.1 M of the anions CH₃COO^-, PO₄^3- and SO₄^2- and buffered to pH 4.75 and 7.5 containing either 2 mL 0.05 M H₂BuEtP or 2 mL 0.05 M H₂BuEtP/0.05 M HBuP in a 9:1 volume ratio was agitated mechanically for an hour, allowed to settle and organic extractants removed and fresh organic extractants added and process repeated. Aqueous raffinates are then analysed for the four metals by comparing with standards using Atomic Absorption Spectrometry for Cadmium, Lead and Nickel and colorimetry for Iron using 1,10-phenanthroline. The results show that CH₃COO^-, PO₄^3- and SO₄^2- can be used for the multi-metal extraction of the four metals and single digit batches (5-8) of extraction were the least needed to get 99.9% extraction of Cadmium (II), Iron (II), Lead (II) and Nickel (II) simultaneously from aqueous solutions buffered to either pH 4.75 or 7.5 using either H₂BuEtP alone or H₂BuEtP/HBuP. 0.1 M CH₃COO^- and buffered to pH 4.75 using chloroform solutions of ligand H₂BuEtP alone and 0.05 M PO₄^3- with aqueous solution buffered to pH 7.5 using H₂BuEtP/HBuP organic phase with 99.9% extraction of the four metal theoretically extractable after 5 batches of extractions gave the best result. pH 7.5 was slightly better for the multi-metal extraction of Cadmium (II), Iron (II), Lead (II) and Nickel (II) from aqueous solutions. CH₃COO^- and SO₄^2- effects were significantly different for Cadmium and iron extractions at both pH 4.75 and 7.5 for H₂BuEtP alone but not significantly different in H₂BuEtP/HBuP organic phases. PO₄^3- and SO₄^2- effects were significantly different for Iron extractions alone at both pHs for H₂BuEtP alone and significantly different for Cadmium and Iron at pH 4.75 for H₂BuEtP/HBuP organic phases. Changes in permittivities/dielectric contants of the solvents leading to favourable energetics in the transfer of formed complexes or adducts from aqueous media to the organic phases was attributed to the simultaneous extractions of the four metals.