Separation of tungsten and rhenium on alumina

摘要

The conditions for the efficient separation of tungsten(Ⅵ) and rhenium (Ⅶ) on alumina were established. The distribution coefficients K_d for tungstate and perrhenate anions, as well as the separation factors α (α = K_(dWO4)~(2-)/K_dReO_4~-) 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 1.0mol dm~(-3) HNO_3 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 Al_2O_3, respectively. With increasing pH, these values decrease. Thus, at pH 6 they are only 4 and 13 mg W/g Al_2O_3, respectively.