A NOVEL SYNTHESIS OF HIGH-AREA ALUMINA VIA H2O2-PRECIPITATED BOEHMITEFROM SODIUM ALUMINATE SOLUTIONS

A novel procedure was devised, whereby crystalline boehmite, gamma-AlO (OH), was efficiently precipitated from sodium aluminate solutions, Na AlO2(aq), following controlled addition of H2O2 aqueous solution. The effects of the aluminate solution variables (viz. concentration, volum e, caustic ratio, pH and temperature), as well as the H2O2/Al2O3 molar ratio, on the amount and composition of the yield, were examined. Acc ordingly, optimal conditions for 98% recovery of the aluminium content of the parent aluminate solution were realized. The remaining NaOH ca n be recycled and used to extract further amounts of aluminium from ba uxite (Bayer process). Thermal stability of the resulting boehmite was explored by thermogravimetry and differential thermal analysis. Accor dingly, various calcination products of the boehmite were obtained at some selected temperatures in the range 400-1100 degrees C and charact erized by chemical analysis, X-ray powder diffractometry, and surface charge and specific area measurements. The results obtained indicated the synthesis of relatively high surface area transitional aluminas of industrial and catalytic merits. (C) 1998 SCI.