5. Conclusions

potential of a rutile-type TiO2 before MFC processing was 0.554 V, while it fell to 0.272 V after processing, a difference of �0.282 V in the contact potential. In anatase-type TiO2, the mean surface potential before MFC processing was 9.928 V, but it fell to 0.166 V after processing, a difference of �9.762 V in the contact potential. The anatase-type TiO2 showed a far higher reduction than the rutile-type TiO2. This advantage of the anatase-type TiO2 is consistent with its superior results in dissociation of water and with the already-known lower band gap of

Table 2 shows how the measured volume of evolved H as measured with a QMS compared with the surface potential results. In rutile-type specimens, the surface potential fell after processing, while the volume of evolved H increased. This is consistent with the promotion of H generation by the low band gap. There was also a correlation between the difference between evolved H volume and surface potential in both rutile- and anatase-type specimens. In rutile-type specimens, the surface potential fell after processing, while the volume of evolved H increased. This is consistent with the promotion of H generation by the low band gap. The particles processed by swirling taper nozzle (inflow hole: 2 pieces) of Figure 4 further

rutile-type TiO2 under visible light.

Table 2. Relationship between surface potential and H + H2 pressure.

Table 1. Measured surface potential values.

68 Cavitation - Selected Issues

After processing titanium dioxide particles and platinum particles as a co-catalyst by cavitation jet using an ejector nozzle (EC) and the multifunction cavitation (MFC), the photocatalytic performance of the modified particles under ultraviolet radiation and visible light irradiation was examined. The following results were obtained.

