Separation of tungsten and rhenium on alumina

Abstract

The conditions for the efficient separation of tungsten(VI) and rhenium (VII) on alumina were established. The distribution coefficients K-d for tunstate and perrhenate anions, as well as the separation factors alpha (alpha = K-dWO4(2-)/K-d ReO4-) were determined using hydrochloric or nitric acid as the aqueous media. A solution of sodium chloride in the pH range 2-6 was also examined. Under all the tested experimental conditions. alumina is a much better adsorbent for tungsten than for rhenium. The obtained results indicated that the best separation of these two elements is achieved when 0.01-0.1 mol dm(-3) HCl or 1.0 mol dm(-3) HNO3 are used as the aqueous media. If NaCl is used as the aqueous phase, the best separation is achieved with 0.20 mol dm(-3) NaCl. pH 4-6. Under these experimental conditions. the breakthrough and saturation capacities of alumina for tungsten at pH 4 are 17 and 26 mg W/g Al2O3. respectively. With increasing pH, these values decrease. Thus, at pH 6 they are only 4 and 13 mg W/g Al2O3, respectively.