Photocatalytic reactions over TiO₂ supported on porcelain spheres

Abstract

Results of immobilisation of TiO₂ on low-cost porcelain beads and the resulting photocatalytic activities of the samples are presented. A very simple technique for immobilisation by immersion in a TiO₂ suspension, previously acidified to pH 2.5, followed by calcination at 450 °C, was used. After vigorous washing with a water jet, no detachment of the catalyst was observed at the end of the fixation process. Reasons for the stability of the material are discussed. The crystallographic nature of P-25 was not affected after attachment to the porcelain surface. The beads were submitted for 100 h to turbulent regimes corresponding to Re numbers of 100 and 400 in a recirculating system. The effect of the recirculation flow was carefully examined to evaluate the degree of detachment of the catalyst from the support and to assess how the treatment influences the activity of the supported catalyst. For this, photocatalytic tests were performed on two model compounds, 4-chlorophenol and potassium dichromate in the presence of ethylenediaminetetraacetic acid, and the results were compared with those of untreated beads. A good activity remained in the beads even after washing for more than 100 h in a turbulent regime (both Re = 100 and Re = 400). The activity of particles detached from the support by ultrasonication was also compared with that of the pure precursor.

Acknowledgements: We thank G. Leyva for taking XRD spectra. This work was performed as part of the Comisión Nacional de Energía Atómica CNEA P5-PID-36-4 programme, the Agencia Nacional de Promoción de la Ciencia y la Tecnología PICT98-13-03672 project and the Consejo Nacional de Investigaciones Científicas y Técnicas PIP662/98 project. G.P. thanks CNEA-CONICET for a fellowship to perform this work. M.I.L. is a member of CONICET.