Carla Riolo

Separation of trace amounts of aluminium on a strong anion-exchange resin loaded with a sulphonated azo dye

The sulphonated azo dye Chromotrope 2B is sorbed quantitatively by the strong anion exchanger AG 1-X8. A chelating resin is obtained, which is able to sorb aluminium from aqueous solutions selectively. The distribution equilibria were investigated under different conditions and interpreted on the basis of a Donnan equilibrium based model for the resin. A separation and pre-concentration method for aluminium in natural waters is proposed, based on the use of the modified resin in a column at ambient pressure. The selectivity with respect to other metal ions was good; this was to be expected because Chromotrope 2B in solution is also selective for aluminium. Recoveries of 100 ± 1% were obtained, with a pre-concentration factor of 50, at a total aluminium concentration of 2 × 10–6 mol kg–1.

Spectrophotometric determination of palladium(II) with four water-soluble heterocyclic azo dyes

1-(Tetrazolylazo)-2-hydroxynaphthalene-3,6-disulphonic acid (T-azo-R), 2-(tetrazolylazo)-1,8-dihydroxynaphthalene-3,6-disulphonic acid (T-azo-C), 1-(thiazolylazo)-2-hydroxynaphthalene-3,6-disulphonic acid (3,6-disulpho-TAN) and 2-(thiazolylazo)-1,8-dihydroxynaphthalene-3,6-disulphonic acid (TAAC) have been investigated as spectrophotometric reagents for palladium(II). Stable water-soluble complexes are formed, even in 1 M perchloric acid, and at this acidity the considered reagents are specific for palladium(II). A number of donor anions interfere in the palladium(II) determination, mainly by competing with the azo dyes for complexation with the metal ion. The first three reagents were found to form 1:1 (metal to ligand) complexes, while the last forms a 1:2 complex, with a molar absorptivity more than twice that of the others. In all instances the spectra of the complexes are well resolved with respect to those of the free ligands. Concentrations of palladium(II) ranging from 2 × 10–6 to 1.5 × 10–4M can be determined spectrophotometrically. The accuracy (relative difference between the known and the found concentration) is 1% at a concentration of 2 × 10–5M.

Spectrophotometric investigation of the reaction of CU(II) and Cu(I) with 1-isonitroso-(1,2,3,4)-tetrahydrophenazine

The reactions of Cu(II) and Cu(I) with 1-isonitroso-(1,2,3,4)-tetrahydrophenazine (HITF) have been studied spectrophotometrically. Both ions form complexes with metal/ligand ratio 1:2. The complex of Cu(I) and ITF can be used for copper determination in the range 2-50 x 10(-6)M, and has been separated as the perchlorate in crystalline form. The spectrophotometric characteristics and the equilibrium constants for the ligand and for the complexes are reported.

Protonation and complex formation with heavy-metal ions of two tetrafunctional amines and of a new structurally related ion-exchange resin

The basicity and complexing ability towards copper(II) of two new tetrafunctional amines containing four basic aliphatic nitrogens (1) and two aliphatic and two heterocyclic nitrogens (2) have been investigated by potentiometric techniques. The basicity constants of the two compounds are different which indicates that the mechanism of protonation is different for the two amines. The presence of complexes [Cu(HL)], [CuL], [Cu(OH)L] for L =(1) and [Cu(H2L)], [Cu(HL)], [CuL], and [Cu(OH)L] for L =(2) could be detected in aqueous solution. A resin whose repeating unit is structurally related to (2) has been synthesized, and its basicity and stability constants have been compared with those of compound (2).