Photocatalysis oxidants other than

The rate constants for reactions of OH with pollutants are summarized in Table 8.1. Rate constants can be used to estimate how easily a pollutant car. be treated by photocatalysis. N02 shows a higher rate constant with OH than any other inorganic compound in Table 8.1, while CH3SH, CH3CHO, propylene, m-xylene appear to be oxidized faster than other organic compounds. 

In the majority of cases, the oxidizing species involved in the photooxidation reactions is not well known because the nature of the species is inferred from indirect experiments. The 02 ion has been invoked as the precursor of the oxidizing species in a number of reactions because it is often the only species observed at room temperature using EPR. However, a variety of other species such as O and OJ have been identified on surfaces when the low-temperature photoreactions are observed by EPR. In addition, O" formed on the surface may have a very short lifetime (as discussed in Ref. 1, p. 93) and can only be detected by its reactivity. With these points in mind, we conclude that O-, and particularly OJ in the presence of excess oxygen, may play a much more important role in photocatalysis than has yet been generally realized. In this connection, the paper of Kubokawa et al. (410) is of particular importance but the use of 170-labeled oxygen is necessary to confirm the nature of the species involved. In order to explore... 

The extraordinary photocatalytic performance of AEROXIDE TiOj P 25 in comparison to other nanoscaled titania particles has been published in several papers It is, for example, useful in the degradation of humic acid [71], of phenol and salicylic acid [72], of l,4dichlorobenzene [73], and in the photocatalytic reduction of Hg(II) [74]. It is also used in the oxidation of primary alcohols to aldehydes [75] or in the photopolymerization of methyl methacrylate [76]. Its use in cement can help reduce environmental pollution [77, 78]. A detailed study is reported by Bolte [79]. The results show that crystal size and filling ratio in mass are more important than the modification of the titania. Pyrogenic titania is not only useful in photocatalysis but also in other catalytic applications. 

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