ADSORPTION OF PERRHENATE ON MODIFIED ALUMINAS

Series of rhenium catalysts were prepared by equilibrium adsorption on unmodified alumina and alumina containing F and Mg additives. The upt ake of perrhenate on alumina was dependent on the pH and the concentra tion of nitrate in the impregnation solution. Uptake of perrhenate at pH 6.5 on F modified alumina decreased with increasing F loading; for Mg-modified aluminas, perrhenate uptake at pH 9.3 increased with incre asing Mg content. A correlation was observed between perrhenate uptake and the isoelectric point (IEP) of the modified supports. These data are interpreted on the basis of electrostatic attractions which occur between perrhenate ions in solution and alumina surfaces. Competition between nitrate and perrhenate for adsorption sites satisfactorily acc ounts for the effect of nitrate on perrhenate adsorption. (C) 1994 Aca demic Press, Inc.