Photocatalysis: a promising technology for wastewater treatment

Photocatalysis is a phenomenon, where an electron-hole pair is generated on exposing semiconducting materials to light of suitable energy. Thus, the chemical reactions that occur in the presence of a semiconductor and light are collectively termed as photocatalytic reactions. Photocatalytic reactions are mainly classified into two categories : (i) homogeneous photocatalysis, where substrate and photocatalyst both exist in the same phase and (ii) heterogeneous photocatalysis, in which substrate and photocatalyst exist in different phases. Different dyes and some soluble coordination compounds are used as homogeneous photocatalyst whereas different semiconducting powders are good examples of heterogeneous photocatalysts. This field has been extensively reviewed by various workers(1-9). Exhaustive researches in the field of photocatalysis have shown various fascinating applications of photocatalytic reactions. In the present review, we are considering photocatalysis as a main tool in dealing with the worldwide problems of environmental pollution and wastewater treatment.