How much time for hydration of the surface of TiO2 should be provided before the photo-catalytic degradation studies of Organic pollutants. I have seen as 24hours in some articles and some authors use just immediately before use. Does this period has an impact on degradation efficiency of TiO2?
Are you talking about adsorption/desorption equilibrium of dye on the surface of TiO2 in dark? If yes then I request you to do a calibration for you own sample by taking uv-vis spectra of the supernatant from the TiO2/dye suspension kept in dark in every hour until the absorbance of the dye becomes constant. Then you start illuminating light. This equilibration time varies sample to sample. Now if you start measuring the dye degradation before reaching the dark equilibrium, your actual data, which you will be collecting by measuring the decrease in absorbance of the dye, would be the combination of adsorption of dye and the degradation!
TiO2 as a photocatalyst must be well hydrated, because It uses water and dioxygen as source of free radical production. Such particles has high specific surface so they need to be well hydrated to insure maximum efficiency : increasing the contact surface between liquid and solid layer, allow the repeatability of the measurement, and allow to reach a maximum of dispersion of the particle. As pointed by both Biswajit and Moisés, you must reach the equilibrium before using for your experiment. But it depends of the degree of accuracy you need for your experiment.
hoping I could help
It all depends on your sample. For metal oxides which feature relatively low specific surface area, it usually needs around 2 hours. The impact on degradation efficiency is minor.
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