On the colloidal behaviour of titanium dioxide nanoparticles in artificial and natural aqueous media.

The considerable growth of engineering nanomaterials (ENMs) applications in many fields has been driven by their novel physicochemical properties, which promise improved functionality. However, the extensive use and high complexity of ENMs fate processes have led concerns about their potential impact upon human and environmental health. ENMs dispersed in biological or environmental media are subjected to several processes such as dissolution, aggregation and surface transformations processes. Since there is a strong likelihood that human and biological impact from ENMs will depend on key physicochemical properties that represent the so-called exposure and hazard determinants, the investigation of interactions between ENMs and the surrounding media is of great importance for supporting the risk and safety assessment of these materials. Among the different ENMs, titanium dioxide nanoparticles (TiO2 NPs) have been selected for this study due to their widespread use in many consumer products, very low solubility, and surface which can be easily modified. The work presented in this thesis can be divided into: (i) the colloidal characterization of TiO2 NPs dispersed in ultra-pure water, artificial fresh water, artificial marine water, and Venice lagoon water (ii) study of the interactions between TiO2 NPs and suspended particulate matter (i.e. kaolinite as model and sediment from the Venice lagoon).