Photocatalytic reactions over TiO_2 supported on porcelain spheres

摘要

Results of immobilisation of TiO_2 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 TiO_2 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.