Study and Development of Photocatalytic Lab-Scale Plants for Pollutants Degradation and Urban Wastewater Treatment

This PhD thesis investigates the development and application of lab-scale plants utilizing synthesized TiO2-based materials for the photocatalytic degradation of pollutants and urban wastewater treatment. Heterogeneous photocatalysis was applied as an advanced oxidation process (AOP) to degrade both model organic pollutants, specifically Methylene Blue (MB), Rhodamine B, and Methyl Orange (MO), and a complex mixture of 29 emerging contaminants. This mixture, prepared by the analytical chemistry group of the Chemistry Department of Genoa University, which also performed the post-treatment analyses, comprised several classes of compounds, including non-steroidal anti-inflammatory drugs (NSAIDs), a plant growth regulator, a β-agonist, UV filters and so on. Both pure titanium dioxide (TiO2) and TiO2 supported on a persistent luminescence material (PeL), which consisted of a mixed solid solution of zinc oxide (ZnO), gallium oxide (Ga2O3), germanium dioxide (GeO2), and chromium(III) oxide (Cr2O3), were used as photocatalysts. The materials were synthesized via sol-gel methods, differently heat treated, and subsequently characterized in collaboration with researchers from the Chemistry Department, Faculty of Science, Kuwait University to highlight any physical-chemical features depending on the chosen synthetic route. The photocatalytic performance of these materials was evaluated in a 1L laboratory-scale plant of our own making. A chemometric approach, employing 2 different experimental design models, was used to investigate the optimal experimental parameters for achieving enhanced photocatalytic activity within the established experimental domain. In addition to the degradation studies, two distinct recovery methods were evaluated, demonstrating successful recovery of the great majority of the photocatalytic materials investigated. Furthermore, a preliminary study on the cleaning and regeneration of the photocatalysts was performed. Thanks also the collaboration of the Nanostructures Magnetic Materials Lab group (nM2) of the Chemistry and Industrial Chemistry Department (DCCI) of the University of Genoa and with colleagues of the University of Uppsala, Sweden, in the present PhD project a first study on the piezo-catalytic and piezo-photocatalytic activity of bismuth ferrite (BiFeO3) based materials was also carried out. A more structured and systematic approach was adopted for scaling up the photocatalytic plant passing from 1L to 10L as maximum operating volume. In this plant the unsupported synthesized TiO2, was employed to study the degradation of the aforementioned mix of emerging pollutants. Furthermore, thanks to the collaboration with Iren S.p.A., the industrial partner involved in this doctoral research project, preliminary investigations were performed on the photocatalytic treatment of real urban wastewater samples collected from wastewater treatment plants (WWTPs) within the Genoa’s metropolitan area. Each individual contribution will be clearly underlined within its dedicated section throughout this manuscript.