Release Analysis of Nano-Titanium Dioxide (TiO2) from Paint: An Accelerated Weathering Experiment

Abstract

Engineered nanomaterials (ENM’s), particularly TiO2 nanoparticles are being incorporated on paints due to their capabilities to enhance optical properties and to scatter UV radiation, which eventually protects the paint from discoloration. In this study, the release of these nano-TiO2 from paint was investigated. Two (2) types of paint were used, one containing pigment- and nano-TiO2 (P1), while the other only contains pigment-TiO2 (P2). The paints were subjected to accelerated weathering wherein the paints were exposed to cycles of UV irradiation and water condensation. The SEM-EDX results showed the distribution of the pigment- and nano-TiO2 on the surface of P1 and P2, and the changes in the morphologies before and after weathering. The photomicrograph revealed the formation of cracks on the surface of P1 brought about by the photocatalytic degradation due to the presence of nano-TiO2. Leachate samples were also collected weekly in the duration of the weathering test and were analysed using ICP-OES. The presence of Ti, which can be correlated to the release TiO2, on the samples was detected. The release of Ti from P1 and P2 showed a decreasing trend throughout the weathering experiment, having the following initial amounts of release: 1.38 mg/L and 2.10 mg/L for P1 and P2, respectively. Moreover, a graphical release mechanism for the nano-TiO2 release was conceptualized based on the results of the study. In general, potential release of nano-TiO2 from paints could happen since these TiO2 nanoparticles serve as a photocatalyst in the paint degradation when exposed to prolonged weathering conditions.