Liquid-Liquid Extraction-Chromogenic System for Vanadium(V) Based on 4-(2-thiazolylazo)orcinol (TAO) and Aliquat 336

摘要

The quaternary ammonium salt Aliquat 336 (A336; R4N+Cl-) and the azo dye 4-(2-thiazolylazo)orcinol (TAO) were examined as constituents of a water-isobutanol extraction-chromogenic system for vanadium(V). Under the optimum conditions (c(TAO) = 1.6x10(-3) mol dm(-3), c(A336) = 1.3x10(-2) mol dm(-3) and pH 5.0), vanadium(V) is extracted as a ternary complex which can be represented by the formula (R-4 N+) [VO2(TAO(2-))]. The key extraction-spectrophotometric characteristics were determined. The interfering effect of foreign ions was studied as well. The wavelength of maximum absorption (lambda(max)), molar absorptivity (epsilon(max)), constant of extraction (K-ex) and fraction extracted (E) were found to be lambda = 547 nm, epsilon = 3.1 x 10(4) dm(3) mol(-1) cm(-1), Log K-ex = 2.8 and E = 90.2%, respectively. Beer's law was obeyed in the range of 0.084-2.0 mu g cm(-3) and the limit of detection was 25 ng cm(-3) of vanadium(V).