A Japanese research group has developed a new method to break down PFAS, a group of organic fluorine compounds often called "forever chemicals" for their persistence in the environment.
The group of Ritsumeikan University researchers succeeded in completely breaking down perfluorooctane sulfonate (PFOS), a type of PFAS, within hours by using nanometer-scale semiconductor crystals as catalysts and applying light from a purple light-emitting diode. A nanometer is one-billionth of a meter.
PFAS, or perfluoroalkyl and polyfluoroalkyl substances, have been used in a wide range of products, such as fire extinguishing agents and coated nonstick cookware, because they have strong water and oil repellent properties.
More than 10,000 types of PFAS are known to exist. The chemicals accumulate in the environment and within the body, raising health concerns.
Japan has banned the production and use of three main PFAS substances including PFOS in principle, but these compounds are believed to be leaking into soil and groundwater from various sources. They have been detected in well water in many places in Japan.
The group, led by professor Yoichi Kobayashi at the private university based in the western city of Kyoto, added 0.8 milligram of cadmium sulfide nanocrystals to a water solution containing 0.65 milligram of PFOS and exposed them to purple LED light.
Within eight hours, the PFOS degraded into organic compounds and fluoride ions. The method also demonstrated high efficiency in decomposing other types of PFAS.
Existing methods to break down PFAS involve ultraviolet irradiation and the application of very high temperatures and pressure, therefore requiring a lot of energy and expenses.
The new method has achieved efficient decomposition only through exposure to light at room temperature under normal atmospheric pressure. In addition, recovered fluoride ions can be used for other purposes.
But practical application of the method is not in sight yet, because the research is still in the experimental stage involving only small amounts of PFAS. However, the method has the potential to play a significant role in realizing recycling of fluorine compounds, the group said.
"It's necessary to design and arrange the apparatus very carefully because only the part exposed to light reacts" to cause decomposition, Kobayashi said. "We want to realize the practical application as soon as possible."
With your current subscription plan you can comment on stories. However, before writing your first comment, please create a display name in the Profile section of your subscriber account page.