A comprehensive physicochemical characterization of zinc oxide nanoparticles extracted from sunscreens and wastewaters

The widespread popularity of sunscreens contributes significantly to the release of zinc oxide (ZnO) nanoparticles into bodies of water, yet there is still lack of sufficient understanding on the realistic behaviour and long-term exposure. In this study, a simple and effective method was used to extract ZnO nanoparticles from ZnO-based sunscreen products (available in Australia) that end up in wastewaters. The extracted ZnO nanoparticles were negative charged at controlled pH 7. Transmission electron microscopy (TEM) analysis revealed an irregular, spherical and rod-shaped nanoparticles extracted from sunscreens and wastewaters with size ≥100 nm. Various nanoparticles containingZnO, iron, silver, and titanium were detected in wastewater samples collected from treatment plants. Other contaminants were also found in the wastewater samples based on TEM elemental analysis. The results documented in this study are useful to understand the presence and characterizations of ZnO nanoparticles in sunscreens and wastewaters. With this knowledge, we can realistically investigate the fate, behaviours and adverse effects of ZnO nanoparticles.