Behavior of engineered nanomaterials from marketed tiles under standardized abrasion conditions
Résumé
The study presented here focuses on marketed antibacterial tiles whose emissivity of (nano) particles due to abrasion has yet barely been investigated. The tiles have been characterized regarding their surface properties and composition throughout their life cycle, i.e. from their use until the end-oflife. In contrast to conventional tiles, their surfaces happen to be uneven. Titanium dioxide is found in the depressions these being protected from abrasion. at the surface, thus protected by the hilly areas against abrasion on the surface of tile. Furthermore, a deposition technique has been put in place by producers allowing coating of the aforementioned marketed tiles with titanium, thus rendering them similar to those available on the market. It consists of depositing titanium dioxide on the surface to be fixed later on the ceramic surface using thermal treatments. Besides the intermittent deposition of nano-TiO2, the major modification on the state of surface can lead to a greater emissivity during its use. The tests reveal the aerosolization of inhalable micronic and submicronic particles that can subjected to be released in the environment from antibacterial tiles. The generated aerosol is mainly dominated by so called nanoobjects, agglomerates and aggregates (NOAAs) where titanium is widely detected but at low concentrations, which is in accordance with the relatively low nano-titanium dioxide presence on the tile surface. No free and isolated nano-TiO2 particles have been released. This emission of NOAAs can be attributed to the intermittent deposition on the tile surface which may be less resistant to abrasion as compared to the uncoated tile surface , the specific mechanical resistance of the nanocoating and the change in the surface morphology where the irregular surface facilitates not only deposition of nano-TiO2 suspension but also the wrench of tile pieces during the abrasion. Long term duration weathering under standardized and documented conditions lead to the formation of submicronic and compact NOAAs. No growth in emission due to weather stress has been detected.