EXTRACTION AND DETERMINATION OF METAL IONS BY USING THE LIGAND HAVING NITROGEN AND SULPHUR DONOR ATOMS

Abstract

3-Amino-5-mercapto-1,2,4-triazole (5.0x10-2M) and its schiff base with salicylaldehyde (synthesis described) have been evaluated for solvent extraction of Cu from its aqueous solution (1.0x10-2M) into kerosene and toluene quantitatively and triazole (5.0x10-2M) has also been used for spectrophotometric determination of copper. Extraction was found to be dependent on pH (acetate buffer of pH 4.3-5.5) and it increases with an increase in pH of the aqueous phase. Maximum extraction occurs at pH 5.30 and 5.50 using triazole and schiff base, respectively. Effect of metal ion concentration, extractant concentration, shaking time and diluent on the extraction of copper have been investigated at the pH 5.30 to optimize the conditions for maximum extraction. It has been found that extractant concentration (triazole) of 5.0x10-2M is sufficient to extract 0.5x10-3 M of Cu(II) from its aqueous solution into kerosene at pH 5.30 ± 0.05 by using shaking time of 10 minutes . Extraction as well as back extraction behaviour of schiff base have been described in terms of its ability to form stable complex in organic phase. The effect of diluents in the extraction process has been studied over the pH range 4.30-5.50 and their extracting capacity was found to be of the order (decreasing order) kerosene>Toluene> Chloroform = carbon tetra chloride > Xylene> Cyclohexanone.Synergistic effect of two extractants, 2,2'-bipyridine and 1,10-phenanthroline has been studied in different diluents. Back extraction studies from toluene(organic phase) were carried out by using 1.0M-3.0M of HCI. The concentration of copper in aqueous phase before and after extraction and after back extraction (with necessary dilution) has been determined by using an atomic absorption spectrophotometer in an air-acetylene flame at 324.7 n'm for Cu. The composition of the complex formed has been determined by Job's continuous variation method and molar ratio method and the stoichiometry of the complex species to be extracted was found to be most probably 1:2 (metal-to-triazole). The blue coloured complex system in H2O obeys Beer's law in the range 0-3.0x10-3M Cu (II) at Amax 336.0, 348.0 and 512.0 nm and molor absorptivity is 9.9 x 103 L mo1-1 cm-I at 336.0 nm and 1.36x103 L mole cm-i at 512.0 nm. Interfer=ence due to Fe (111) was studied by extraction- atomic absorption spectrophotometry in an air - acetylene flame at 248.3 nm. Zn (II), Co (11), Ag (1), Fe (11), Ni (II), Pb(11), K+ and Na+ were found to be interfering .