(1) Introduction to Photocatalytic Oxidation Process
Photochemical and photocatalytic oxidation methods are a kind of advanced oxidation technologies that have been studied more recently. A photocatalytic reaction is a chemical reaction performed under the action of light. After a molecule absorbs electromagnetic radiation of a specific wavelength, the molecule reaches an excited state, and then a chemical reaction occurs to generate a new substance or become an initiator of a thermal reaction.
and process of photocatalytic oxidation
As a semiconductor material, Ti02's own photoelectric properties determine that it can be used as a photocatalyst. The energy band structure of a semiconductor is usually an electron-filled low-energy valence band (VB) and an empty high-energy conduction band (CB). The region between the conduction band and the valence band is called the forbidden band.
When the energy of the light irradiating the semiconductor is equal to or greater than the width of the forbidden band, the valence band electrons are excited, enter the conduction band across the forbidden band, and generate corresponding holes in the valence band. The electrons are excited from the valence band to the conduction band, and some of the separated electrons and holes undergo further reaction.
(3) Influencing factors of photocatalytic oxidation process
Studies have shown that the initial concentration of reactants has a significant effect on photocatalytic efficiency or degradation rate. The photocatalytic efficiency fluctuates with the increase of the initial concentration, and there is a clear concentration transition point; the photocatalytic degradation efficiency of the low-concentration target is greater than that of the high-concentration target.
There is no consistent conclusion about the effect of humidity on the photocatalytic reaction. There are great differences in experimental conditions such as different compounds or different concentrations.
(4) Advantages and disadvantages of photocatalytic oxidation process
High processing efficiency, low operating cost, suitable for low concentration and wide range of VOCs, especially high removal efficiency of aromatics;
The treatment efficiency for high-concentration VOCs is average; it is still mainly in the laboratory stage and lacks practical application.