Granulometric analysis of TiO2 particles in the aspect of membrane filtration

The paper presents a granulometric analysis of the size of particles of Aeroxide® P25 and P90 titanium oxides in the context of their retention in low-pressure membrane processes (microfiltration, ultrafiltration). Measurements of the particle size using a laser granulometer showed that the particle size of TiO2 Aeroxide® P25 dispersed in water is in the range from approx. 0.3 μm to approx. 150 μm. The particles with dimensions smaller than 1.0 μm constituted about 7.0%, and the largest particles, with dimensions above 30 μm, constituted about 0.9% of the volume of all the particles in the suspension, respectively. In the case of TiO2 Aeroxide® P90, a double curve of grain size distribution was observed. For the main curve, the particle size ranged from approx. 0.3 μm to approx. 18.7 μm. The particles with dimensions smaller than 1.0 μm constituted approx. 3.0% by volume of all particles in the sample. The second curve, which can be described as oversized/supersized grains, was comprised of particles ranging in size from about 21 to 170 μm, and they accounted approximately for 3.9% by volume of the total particles in the sample. The specific surface area for the samples was 0.56 m2/g for TiO2 P25 and 0.48 m2/g for TiO2 P90. It was found that the observed large particle sizes of titanium oxide particles in aqueous solutions may be the result of their agglomeration, which gives one hundred percent certainty that they will be retained by ultrafiltration and microfiltration membranes with pore sizes above 0.3 μm.