Characterization of photocatalytic materials used for water treatment

As the pressure on water bodies throughout the world is increasing, good water quality obtained through water treatment is essential to secure health and welfare of the population. Many chemical compounds used in industry and agriculture with discharge to drinking water sources or vulnerable recipients have not been examined properly before approval. Many of these chemicals have eventually been considered to be toxic or hostile towards the environment, hence they are called micro-pollutants. Some of the newly discovered micro-pollutants are also known as emerging contaminants, but this is certainly not a well-defined group of species (K¨ummerer 2011), even though it is frequently reported in scientific papers. Examples of such compounds are pharmaceuticals, dyes, personal care products, soaps and pesticides. Actually, some of them threaten to destroy water sources and other aquatic environments. Unfortunately, conventional treatment methods are not designed to remove micropollutants. However, so-called advanced oxidation processes (AOPs) are up-and-coming water treatment processes that are promising for this matter. In this thesis one of the most well-known, but least understood AOPs are examined. It is called photocatalysis with the use of TiO 2 and UV-LED. Further, experiments designed to find the bandgap of a large selection of materials of modified TiO 2 have been conducted for this thesis. The modification has been conducted through doping with metal ions. Some of the most promising materials from the bandgap experiments were put in a photoreactor to find the radical production compared to a reference TiO 2 material. The results from the bandgap analyses showed that most of the materials had decreased bandgap compared to the reference at 3.16 eV. In particular, the manganese-doped TiO2 materials showed the highest decrease, down to 2.89 eV for one of the samples. Meanwhile, the radical production experiments had some promising results, but as duplicates and triplicates of the experiments were executed, none of them were reproducible. In other words, the results from the radical production were not valid and could therefore not be used for extensive discussion. Furthermore, this made large parts of the master thesis pointless, since the radical production is a substantial part of the process. For the future work in the project, the experiments and the revealed weaknesses may, however, contribute to a better setup and procedure for further testing