Solvent extraction of heavy metals contained in phosphoric acid solutions by 7-(4-ethyl-l-methyloctyl)-8-hydroxyquinoline in kerosene diluent

The solvent extraction of zinc, cadmium and chromium contained in 5.5 mol/L phosphoric acid solutions (30% P2O5) was investigated using 7-(4-ethyl-1-methyloctyl)-8-hydroxyquinoline-Kelex 100 (R) as extractant and treated kerosene as diluent. At organic-to-aqueous phase ratio (1/1) and at room temperature, 58% of zinc, 34% of chromium and 15% of cadmium were recovered in 240 min. In order to improve the kinetics of extraction, a modifier reagent was added to the organic phase. The addition of n-decanol (10 vol.%) increased the rate metals extraction by reducing the equilibrium time from 240 min to 30 min, along with 60% recovery of metals. Extraction of metal ions increased with increasing aqueous phase pH. The pH(0.5) values difference of 0.1 M with Kelex 100 (R) indicates the possible separation of cadmium, zinc and chromium. Increasing the concentration of Kelex 100 (R) increased the percentage extraction of metal ions. The loading capacity values were found to be 83%, 80% and 71% for zinc, chromium and cadmium, respectively, at 0.4 M Kelex 100 (R) concentration, indicating that the extractant is highly selective for the metal ions considered. (c) 2005 Elsevier B.V All rights reserved.