Applications of ANNs on photocatalytic reactors: a brief overview

Heterogeneous photocatalysis is a “green” technology with potential applications in various disciplines, such as chemical synthesis and environmental technologies. These processes use certain metal oxides those can generate hydroxyl radicals on the surfaces of particles when exposed to UV light. The anatase form of TiO2 has low band-gap energy (approximately 3.2eV), which is almost equivalent to 400nm wavelength of light. Activation of semiconductor TiO2 catalyst achieved through the absorption of photon of ultraviolet band gap energy, results in the formation of electron donor (reducing) and electron acceptor (oxidizing) sites. The photocatalytic activity of TiO2 depends on the relative rates of generation and recombination of electron-hole pairs as well as the adsorption of radical-forming species on TiO2 surfaces. Hydroxyl radicals (HO·) and superoxide ion are the principal agents responsible for the oxidation of aqueous organic contaminants [1].  The carbon containing pollutants are oxidized to carbon dioxide and water, while the other elements bonded to the organic compounds are converted to anions such as nitrate, sulphate or chloride. The purification of wastewater by heterogeneous photocatalysis is one of the most rapidly growing areas of interest to both research workers and water purification plants. Commercial application of the process is called advanced oxidation process (A.O.P).