Photodegradation of pollutants

The degradation of organic pollutants, especially chlorinated hydrocarbons, was the subject of many investigations. Only two examples will be given here, which are investigated in more detail. One is the degradation of chloroform. The overall reaction is given by 

In the latter case, the photodegradation was measured at various semiconductor particles as shown in Fig. 11.20 [108]. According to these results, Ti02 is the best catalyst 

20 Concentration of parachlorophenol vs. irradiation time (photodegradation). (After ref. [108]) 

The technique of photocatalytic purification of water is especially suitable for small concentrations of pollutants. Compared with other techniques, obviously here no other dangerous compounds like dioxine are formed. Another interesting application is the photocatalytic treatment of oil slicks [113]. In order to keep the photocatalytic material on the surface, Ti02 was deposited on hollow microbeads of aluminosilicate. 

In all cases where sunlight is used for detoxification processes the efficiency is rather small because Ti02 absorbs light only in the UV (A 400 nm). Accordingly, various attempts have been made to increase the activity. One way of doing this is the use of Ti02 particles loaded with Pt [114]. 

The technique of photocatalytic purification of water is especially suitable for small concentrations of pollutants. Compared with other techniques, obviously here no other dangerous compounds like dioxine are formed. Another interesting 

---

L. Campanella, R. Cresti, M. P. Sam-martino, G. Visco, Microwaves Assisted Photodegradation of Pollutant, SPIE Conf. Environmental Monitoring and Remediation Technologies, Boston, 1998, pp. 105-113. 

Bolton )R, Cater SR (1994) Homogeneous Photodegradation of Pollutants in Contaminated Water An Introduction, in Aquatic and Surface Photochemistry, Helz G R (ed.), Lewis Publishers, Boca Raton, pp 467-490. 

Bolton JR, Cater SR (1994) Homogeneous Photodegradation of Pollutants in Contaminated Water An Introduction, in ... 

Bolton, J., and Cater, S 1994, Homogeneous photodegradation of pollutants on contaminated water An introduction, in Aquatic and Surface Photochemistry, Hels, G., Zepp, R., and Crosby, D., eds., Lewis Publications, pp.467. 

---