Establishing Photocatalytic Kinetic Rate Equations: Basic Principles and Parameters -- Novel Photocatalytic Reactors for Water and Air Treatment -- Photocatalysts, Radiation Sources and Auxiliary Equipment for Photocatalysis -- The Irradiation Field in Photocatalytic Reactors -- Kinetic Modeling of the Photocatalytic Reaction Network: The Parallel-Series Approximation -- The Energy Efficiency Factors in Photocatalytic Processes -- Water Decontamination of Organic Species: Modeling Reaction and Adsorption Processes -- Photocatalytic Degradation of Air Borne Pollutants -- Advances and Perspectives for Photocatalysis.Heterogeneous photocatalysis is a novel technique for water purification. Publications on photocatalysis span a relatively recent period of not more than 25 years. This is a technique that, according to our extensive experience on the development of laboratory scale and pilot plant units, has great promise to eliminate water and air pollutants. Photocatalysis offers much more than competitive techniques where pollutants are transferred from phases; photocatalysis can achieve complete mineralization of pollutants leaving non-toxic species such as CO2 and H2O and can be exploited at close to room temperature and ambient pressure.