Preparation and characterisation of alumina coated TiO₂ - poster

Steven Hall^1
1Centre for Doctoral Training in Complex Particulate Products and Processes, School of Chemical and Process Engineering, University of Leeds, LS2 9JT, UK

More than 7.5 million tonnes of titanium dioxide (TiO₂) are produced worldwide each year for use as white pigments in paints, plastics and paper. During manufacture, TiO₂ is often coated with small amounts of hydrous alumina in order to decrease its photocatalytic activity and prevent photodegradation of the material in which it is dispersed in.

In this work, alumina coated TiO₂ was prepared using a wet treatment process, precipitating various levels of alumina (0.3 – 3.0 wt%) on to aluminium-doped TiO₂ aggregates. The uncoated and alumina coated TiO₂ aggregates were then characterised by TEM, XRD, XRF, EDS, ESA, image analysis and laser diffraction particle size analysis in order to understand the influence of alumina coatings on physicochemical properties.

For uncoated TiO₂, the aggregate size was determined to be 334 nm, with a suspension IEP was of  pH 4.7. For alumina coated TiO₂, elemental analysis via XRF and EDS, supported by TEM and ESA measurements confirmed alumina had been precipitated at the required levels and were present on the surface of TiO₂ aggregates. With increasing alumina coating level, the IEP increased to a maximum of pH 8.7 and a maximum aggregate size of 1280 nm for an alumina coating level of 3 wt%. These findings can be used for the design of TiO₂ pigment products.