Pristine nanodiamonds (NDs) obtained by detonation, or functionalized by different treatments, namely oxidation, hydrogenation and amination, were used to synthesize composites by insertion in TiO₂ matrixes. The different treatments of the NDs lead to materials containing diverse texture properties and surface chemistry functionalities, particularly concerning the insertion of nitrogen and oxygen groups. The photocatalytic activity of the prepared composites was evaluated for the oxidative degradation of two water soluble pharmaceuticals – diphenhydramine and amoxicillin – under near-UV/Vis irradiation. The most active photocatalyst in what concerns both pollutants degradation under near-UV/Vis irradiation was the composite containing pristine NDs (NDDT). The photocatalytic performances were dependent on the specific surface area and on the amount of functional groups incorporated over the NDs. The influence of ND in the composites activity is well correlated with the observed photoluminescence quenching of TiO₂, which corresponds to a delay in the recombination rate of charge carriers that benefices the photocatalytic reaction. Scavenging of photogenerated holes and radicals by employing sacrificial hole and radical agents revealed that the holes played the main role on both pollutants degradation under UV/Vis irradiation. Reutilization experiments proved that the ND composites have good stability and reusability.

Photocatalytic ozonation was employed for the first time in continuous mode with TiO₂-coated glass Raschig rings and light emitting diodes (LEDs) to treat urban wastewater as well as surface water collected from the supply area of a drinking water treatment plant (DWTP). Different levels of contamination and types of contaminants were considered in this work, including chemical priority substances (PSs) and contaminants of emerging concern (CECs), as well as potential human opportunistic antibiotic resistant bacteria and their genes (ARB&ARG). Photocatalytic ozonation was more effective than single ozonation (or even than TiO₂ catalytic ozonation) in the degradation of typical reaction by-products (such as oxalic acid), and more effective than photocatalysis to remove the parent micropollutants determined in urban wastewater. In fact, only fluoxetine, clarithromycin, erythromycin and 17-alpha-ethinylestradiol (EE2) were detected after photocatalytic ozonation, by using solid-phase extraction (SPE) pre-concentration and LC-MS/MS analysis. In surface water, this treatment allowed the removal of all determined micropollutants to levels below the limit of detection (0.01-0.20 ng L^-1). The efficiency of this process was then assessed based on the capacity to remove different groups of cultivable microorganisms and housekeeping (16S rRNA) and antibiotic resistance or related genes (intI1, blaTEM, qnrS, sul1). Photocatalytic ozonation was observed to efficiently remove microorganisms and ARGs. Although after storage total heterotrophic and ARB (to ciprofloxacin, gentamicin, meropenem), fungi, and the genes 16S rRNA and intI1, increased to values close to the pre-treatment levels, the ARGs (blaTEM, qnrS and sul1) were reduced to levels below/close to the quantification limit even after 3-days storage of treated surface water or wastewater. Yeast estrogen screen (YES), thiazolyl blue tetrazolium reduction (MTT) and lactate dehydrogenase (LDH) assays were also performed before and after photocatalytic ozonation to evaluate the potential estrogenic activity, the cellular metabolic activity and the cell viability. Compounds with estrogenic effects and significant differences concerning cell viability were not observed in any case. A slight cytotoxicity was only detected for Caco-2 and hCMEC/D3 cell lines after treatment of the urban wastewater, but not for L929 fibroblasts.