Photocatalytic water treatment: substrate-specific activity of titanium dioxide

In this thesis, heterogeneous photocatalysis is presented as a promising technology for water purification. Photocatalysis is revisited from an experimental and engineering point of view, comprising some theoretical fundamentals towards the commercialization of domestic appliances for water purification. Next, will be described briefly the research done in each experimental chapter. In Chapter 2, it is presented a novel and inexpensive 96-well microplate photo-reactor, is presented suitable for high throughput screening. This method is applicable to a wide range of model organic contaminants and photocatalysts, and only requires very short reaction times, up to 15 min and the working volume of the reactor is only 200 µL. Finally, a very important aspect is that limitations in light penetration through the aqueous solution (reactor height is 1 cm) are absent, resulting in an efficient utilization of all the catalyst particles available within the reactor, providing a close to intrinsic value of the rate constant. One of the latest concerns in water purification technology, is the prevalence of pharmaceuticals in the environment and their potential detrimental effects on human health. High throughput screening of a pharmaceutical library with 1280 compounds was performed to evaluate ¬the ability of TiO2 to degrade these new emerging contaminants and the results are described in Chapter 3. The high throughput screening performed previously in Chapter 3 also revealed that steroids are a class of compounds that are difficult to oxidize. For that reason, in Chapter 4, further studies were done with cortisone acetate (model compound) with focus on optimizing the mineralization parameters (pH, catalyst loading, etc), in a laboratory scale slurry reactor (50 ml). In Chapter 5, a study of photocatalytic degradation of mixtures of organic compounds in aqueous solution is described. Such study is very relevant for practical application of photocatalytic water treatment, since then simultaneous decomposition of several organic contaminants is required. Chapter 6 is focused on photocatalytic degradation of organic compounds in oxygen lean conditions over Pt-TiO2 as catalyst, to achieve concurrent production of hydrogen