One-step synthesis of Ti[O.sub.2]/perlite composites by flame spray pyrolysis and their photocatalytic behavior

Ti[O.sub.2]/perlite composites were prepared via facile one-step flame spray pyrolysis (FSP) route. Titanium alkoxide (TIPO) and expanded perlite were used as Ti source and substrate, respectively. Precursor TIPO-ethanol solutions containing homogeneously dispersed perlite particles were processed through FSP setup at different experimental conditions regarding the gas flow and precursor supply rates. The structure, morphology, and the composition of the obtained powders were investigated. The porosity and the light absorbance of the Ti[O.sub.2]/perlite composites were examined and their photocatalytic activity in NO oxidation was evaluated. Commercial titania powder P25 was also FSP processed and investigated for comparison. The XRD analysis revealed that biphased titania with different anatase-rutile ratio and particles size 20-40 nm was synthesized onto the perlite which according to microscopy results was covered by neck-connected Ti[O.sub.2] nanoparticles. The anatase-rutile interplay was also demonstrated by the Raman spectra where presence of Si-O-Ti vibrational modes was observed for some samples. The UV-Vis diffuse reflectance spectra of the Ti[O.sub.2]/perlite composites revealed up to 70% reflection that was connected to the presence of the gray perlite and superficial carbon. The best photocatalytic activity of the composites was connected to almost equal anatase-rutile ratio and possible synergetic effect of the two Ti[O.sub.2] phases.