Spray drying of TiO2 nanoparticles into redispersible granules

We have demonstrated how titania nanoparticles can be spray-dried to produce redispersible granules. The evaluation of different dispersants using rheology, particle size and electrokinetic measurements showed that an anionic carboxylated polyelectrolyte, Dispex N40, was able to stabilize the primary aggregates of the titania nanoparticles with a size of about 180 nm at an addition of 2.4% dry-weight basis over a relatively large pH-range. Transmission electron microscopy showed that the commercial P-25 titania nanopowder could not be deagglomerated down to the individual crystallite size of 15-40 nm. Spherical granules with a size between 20 and 50 μm and a minimum amount of dusty fines could be produced by spray drying the aqueous titania dispersions in a configuration with internal bag filters. The granules could be completely disintegrated and redispersed in water by ultrasonication into a stable suspension with a size distribution that is identical to the as-received powder. The possibility to prepare redispersible nanoparticle granules by spray drying is a route to minimize the risk of airborne exposure and facilitate the handling of nanopowders.