Photocatalytic degradation of pollutants with emphasis on phthalocyanines and related complexes

Abstract

Safe disposal of different harmful substances considered as pollutants is a key problem in the environmental context. Principal approaches for decontamination are briefly overviewed. The main focus is then placed on different photochemical methods used for degradation of pollutants. Application of phthalocyanine complexes for degradation of chlorinated phenols, dyes, etc. is discussed in more details. Three principal approaches involving these readily accessible catalysts are formulated: (i) chemical systems including a catalyst and an oxidant; (ii) photochemical systems based on photosensitizers absorbing UV and visible light for generation of reducing and oxidizing sites which react directly with molecules of pollutants and with molecular oxygen to form strong oxidants like hydroxyl radical; (iii) combined photo-assisted oxidation processes when external oxidant like hydrogen peroxide and light are used together to boost the oxidative degradation. Mechanistic aspects of different approaches are discussed to illustrate the essential features of different processes to provide some background for the choice of optimal system for new developments.