The heterogeneous photocatalysis combined with the use of nanostructured materials has proven to be a viable and highly efficient technology in the degradation of numerous organic compounds. This chapter present the fundamental aspects of nanometric semiconductors related to photodegradation and their treatment conditions for effluents contaminated. The role of the predominant species involved in each process has been studied using radical scavengers. In photocatalytic studies, clay minerals have recently been used as supports for the anchoring of semiconductors, developing photocatalysts with appropriate crystalline structure, which are more ecologically compatible and also have a high surface area. Additionally, the operational devices and influence on the degradation effectiveness such as dyes, pesticides and drugs were discussed for environmental treatment.