Production of Titanate Microspheres by Sol-Gel and Spray-Drying

Porous titanate precursor microspheres (20–60 m in diameter), with a high sorption capacity for radioactive wastes from nuclear reprocessing plants, have been produced on a 50 kg scale by spray-drying precursor sols. Well-dispersed, stable sols were produced by hydrolyzing acetic acid modified tetraisopropyltitanate and peptizing the titania hydrolysate with acidic zirconia sol. The resulting TiO2 /ZrO2 sols were routinely concentrated to 900 g dm–3 (oxide basis) and exhibited excellent stability. These sols were subsequently mixed with dispersible alumina powder and partially aggregated by adding calcium and barium nitrate salts. The resulting sols were spray-dried to produce microspheres with controlled porosity and morphology. The properties of the spray-dried powder were very dependent upon the chemical properties of the precursor sol. In particular, hollow spheres were produced from well-dispersed sols, whereas solid spheres could be produced from partially-aggregated sols.