Solar photocatalytic degradation of water and air pollutants:: Challenges and perspectives

Solar photocatalytic oxidation processes (PCO) for degradation of water and air pollutants have recently received increasing attention. Some field-scale experiments have demonstrated the feasibility of using a semiconductor (TiO(2)) in solar collectors and concentrators to completely mineralize organic contaminants in water and air. Although successful pre-industrial solar tests have been carried out, there are still discrepancies and doubt concerning process fundamentals such as the roles of active components, appropriate modelling of reaction kinetics or quantification of photoefficiency. Challenges to development an catalyst deactivation, slow kinetics, low photoefficiency and unpredictable mechanisms. The development of specific non-concentrating collectors for detoxification and the use of additives such as peroxydisulfate have made competitive use of solar PCO possible. The challenges and perspectives of solar driven PCO as illustrated in the literature and our own results in large solar held loops at the Plataforma Solar de Almeria and CIEMAT laboratories are described. (C) 1999 Elsevier Science Ltd. All rights reserved.