Extraction and Characterization of TiO2 Pigments from Commercial Paints for Environmental Studies

TiO2 nanoparticles are found as pigments in coatings and paints and are, therefore, released into the environment through runoff. To assess their environmental impact, comprehensive fate and ecotoxicity studies necessitate particles closely resembling those released into the environment. In response, we developed a method designed to isolate TiO2 particles from commercial paints. Using six contrasting paints alongside a pure TiO2 pigment, we evaluated two extraction methods in terms of recovery, purification rate, and preservation of both inorganic and organic particle coatings. The paints and extracts were characterized using cryogenic-TEM, ICP-OES, thermogravimetry, and infrared spectroscopy. In contrast to the alkaline-based extraction method, the extraction with acetic acid facilitated the retention of both inorganic and organic coatings and ensured good removal of organic polymers. Recovery rates exceeded 70% for all paints and extraction methods, yet the complete removal of SiO2, when present, was not achieved. CaCO3 removal was effective with both extraction methods. Our developed extraction method enables the isolation of TiO2-particles similar to those aged within paints. However, we recommend using silicate-free paints when SiO2 interference is of concern for the study design. Furthermore, this method could be interesting for pigment recycling, offering a gentler alternative to existing techniques which compromise particle coatings.