Homogeneous Photodegradation of Pollutants in Contaminated Water: An Introduction

This chapter focuses on the processes that involve homogeneous photolysis. It also focuses on applications in water treatment, since this area is much more developed than the photochemical treatment of contaminated air. The use of homogeneous photodegradation to treat contaminated water dates back to the early 1970s. The range of contaminated waters that may be treated with homogeneous photolysis systems is quite broad, including drinking water, groundwater, industrial process water, marine tank ballast water, process water in offshore drilling rigs, etc. Only the homogeneous photolysis processes have been fully implemented commercially, and even in that case only a small fraction of potential sites are employing these processes. The use of ultraviolet light for the photodegradation of pollutants in water can be classified into three principal areas: photooxidation, photoreduction, and direct photodegradation. In order to maximize the rate of reaction, there must be a good wavelength overlap between the emission of the lamp and the absorbance of the absorbing species.