Infoscience

Thesis

Supported photocatalysts for model pollutant degradation and bacterial inactivation: preparation, evaluation and characterization

Water quality and bacterial infections are directly related to human health and wellbeing, thus waste water treatment is a necessary procedure for avoiding disturbances to ecosystems and for assuring human health. Furthermore, bacterial contamination in water bodies, the appearance of antibiotic resistant bacteria in hospitals and public places have to be addressed and not only by means of proper aseptic practices. Water quality improvement and antibacterial surfaces call for the need to design new supported catalsysts/photocatalysts. The above mentioned issues have given rise to a research field called advanced photochemical oxidation processes (APO’s). This Thesis is based on APO’s while designing, testing and characterizing supported photocatalysts. The used supports were: Polyethylene thin films, glass Rashig rings and Glass fiber mats. Photocatalysts as TiO2, Fe-oxides, Cu-decorated TiO2 and copper oxides were deposed by dip coating and sputtering on the mentioned supports. The photocatalysts were tested mostly under solar simulated light irradiation for the degradation of methylene blue (MB) in solution, the inactivation of bacteria (E. coli) in solution and inactivation of bacteria on solid-air interface. Characterization techniques allowed describing/optimizing the surface of the catalyst/photocatalyst leading to pollutant degradation and bacterial disinfection. Photocatalyts supported on polyethylene films (PE-TiO2 and PE-FeOx) showed activity in the degradation of MB in solution over several use cycles, suggesting a potential practical use. The TiO2 light absorbance in the visible region was improved by the addition of Cu/CuO and moreover, the contact between photocatalyst and targets (MB or E. coli) was increased by using glass Raschig rings or glass fiber mats (GF) as supports. Only very low amounts of Cu were enough to increase MB degradation kinetics. Self-cleaning of MB was evaluated on GF-TiO2-Cu-mats under simulated solar irradiation as well. Bacterial inactivation in solution by means of GF-TiO2-Cu 3%-mats showed to be much faster than via GF-TiO2-mats. Regarding antibacterial films, copper oxides were deposed on polyethylene by direct current magnetron sputtering (DCMS) showing antibacterial activity not only under very low light intensity but also in the dark.

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