Solar photocatalysis for water disinfection: Materials and reactor design.
Document Type Article
This article is also available at http://pubs.rsc.org/en/content/articlepdf/2014/cy/c4cy00006d
The number of people living in areas without safe drinking water is predicted to increase by three billion by the end of this decade. A number of recent cases of E. coli and Cryptosporidium contamination in drinking water is also reported in a number of advanced countries. Therefore ensuring the hygiene of drinking water will be highly challenging to both developing and developed world in the future. A combination of the SODIS (Solar disinfection) and photocatalysis technology offers the real possibilities of removing lethal bacteria from drinking water. The time taken for the conventional SODIS disinfection process can be greatly reduced by semiconductor based photocatalysis. The current review addresses the fundamental reaction mechanism, advances in the materials synthesis and selection and recent developments in the reactor design for solar energy driven photocatalysis. The major advantage of using a photo-reactor is that they enhance disinfection by increasing photon flux into the photocatalyst. Major factors affecting such efficiency of solar based photocatalysis such as i) the illuminated volume/total volume ratio, catalyst load and flow rate are addressed in detail. The significance of using an immobilised catalyst over the slurry catalyst is also highlighted. It is noted that, despite the encouraging early field studies, the commercialisation and mass production of solar photocatalysis systems remains highly challenging. Recommendations for future directions for addressing issues such as mass transfer, requirement of a standard test method, bottle design and light absorption by TiO2 coatings are also discussed.