Fabrication of single- and mixed-phase titanium dioxide photocatalysts

Abstract

Multifaceted research was conducted into the fabrication of single- and mixed-phase titanium dioxide photocatalysts using organometallic precursors and commercially available powders. Three photocatalyst immobilisation techniques involving the use of electrophoretic deposition, spin coating of sol-gels and the deposition of coatings on sand grains were explored. Associated enabling work involved the development of novel methods for the enhancement of dispersion and aqueous electrophoretic deposition of oxides on large-scale surfaces. Similar work was done on the coating of small-scale surfaces in the form of TiO2 coatings on sand grains, which are a potential low-cost support for water purification photocatalysts. The preceding studies were interpreted in terms of the anatase to rutile and brookite to rutile phase transformation behaviour was investigated through the thermal treatment of supported and powdered TiO2 materials. Various compositional and morphological factors were found to have significant effects on the anatase to rutile phase transformation and the temperatures at which mixed-phase TiO2 materials were obtained. These effects were discussed in light of an interpretive and predictive review of the phase transformations. The performance of these single- and mixed-phase supported titanium dioxide materials were investigated in pilot-scale water purification studies through the inactivation of bacteria and through the photo-oxidation of methylene blue. The similarity in the results was such that it was not possible to determine if these data resulted from the impact of insufficient sensitivity of the testing and analytical procedures on the ability to differentiate between the competing effects of compositional and morphological aspects of the phase assemblage.