Comparison of 8-Quinolinol Derivatives as Carriers for the Collection of Heavy Metals with Emulsion Globules

Abstract A series of 8-quinolinol derivatives has been examined as carriers for the collection of heavy metals with water-in-oil emulsion globules. The emulsion was prepared by dissolving 50 μmol of 8-quinolinol derivative and 30 mg of Span-80 (sorbitan monooleate) in 2.0 cm3 of toluene and vigorously mixing with 0.50 cm3 of 1.0 mol dm−3 hydrochloric acid by ultrasonic irradiation. The resulting emulsion was gradually injected into 25 cm3 of sample solution [containing 0.10 μg each of Fe(III), Co(II), Ni(II), Cu(II), Cd(II), and Pb(II)] at pH 4–8 and dispersed by stirring for 10 min as numerous tiny globules. When working with the parent compound, 8-quinolinol, Fe(III), Co(II), Ni(II), Cu(II), and Cd(II) were effectively transported through the toluene layer into the internal aqueous phase of the emulsion. However, Pb(II) was not transported at all. The derivatives of 5,7-dichloro-, 2-methyl-, and 5-octyloxymethyl-8-quinolinol were not useful for the simultaneous collection of the heavy metals. On the other hand, Kelex-100 (7-dodecenyl-8-quinolinol) allowed a nearly quantitative (more than 90%) collection of all the metals at pH 7–8. The effects of the substituents on the metal-collection efficiency are discussed in terms of the acidity and hydrophobicity of the carriers.