Polyfluoroalkyl substances (PFAS), which contain numerous carbon-fluorine (C-F) bonds and exhibit extremely high stability, have been used across a wide range of industrial sectors. However, because these substances do not easily degrade in the environment and lead to environmental persistence and bioaccumulation, regulations and management have been strengthened around the world. Conventional PFAS decomposition methods require harsh conditions such as high-temperature treatment, powerful oxidizing agents, and deep ultraviolet light, making the development of new decomposition technologies an urgent necessity.
A research group led by Professor Yoichi Kobayashi of the College of Life Sciences at Ritsumeikan University developed a sustainable PFAS decomposition technology that leads directly to practical application by utilizing the photocatalytic properties of zinc oxide (ZnO) nanocrystals, which are low in toxicity, inexpensive, and can be synthesized in large numbers. The research group added ZnO nanocrystals with surfaces modified by acetate ions and triethanolamine as a hole scavenger to an aqueous solution containing perfluorooctanesulfonic acid (PFOS), which is particularly difficult to decompose among PFAS. They then irradiated the suspension with near-ultraviolet LED light at a wavelength of 365 nanometers (nano means one billionth). As a result, the PFOS was efficiently decomposed at room temperature and atmospheric pressure, with the C-F bonds reduced to fluoride ions (F−), and the residual rate of the PFOS was reduced to 0.5 percent after 10 hours of irradiation.
This technology has potential for wide-ranging applications including water treatment facilities, industrial wastewater treatment, and regeneration of filters that have adsorbed PFAS. The fluoride ions generated can easily be separated and recovered as fluorite, a raw material ore, by adding calcium ions, making it potentially useful as a technology that achieves both environmental purification and resource recycling.
(Article: Masanori Nakajo)
