(251c) Filtration Characteristics of Anatase Colloids

Filtration tests on two forms of titanium dioxide particles (anatase ANX type N and P25) are reported as a function of the dispersion pH. The surface area, particle size, porosity, and particle density are characterised for these materials. Zeta potentials are also determined as a function of pH by the electro-acoustic method. The filter cake permeability and bed height are measured for each sample and reported as a function of time. Characterisation of the zeta potential indicates that both samples behave in dispersion as anatase TiO2. Furthermore, the inherent material properties such as density are also consistent for both samples. Measurement of the particle size distribution suggests that the two samples have a similar primary size around a micron. However, detailed analysis using electron micrographs shows that the inherent particle structures are quite different; the ANX Type N consisting of solid amorphous particles and the P25 having particles made up of fractal like aggregates of nano-sized primary particulates. These differences are seen to have a dramatic influence on the filtration properties for these two samples.