The Green Page:

Japanese Researchers Develop Method to Break Down PFAS 'Forever Chemicals':

Kyoto –

A Japanese research group has developed a new method for breaking down PFAS, a group of organic fluorine compounds often called "forever chemicals" because they persist 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 poly-fluoroalkyl 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.

There are more than 10,000 types of PFAS. The chemicals accumulate in the environment and in the body, raising health concerns.

Japan has banned the production and use of three main PFAS substances, including PFOS, in principle. However, 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 in Kyoto's western city, added 0.8 milligrams of cadmium sulphide nanocrystals to a water solution containing 0.65 milligrams 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 of breaking down PFAS involve ultraviolet irradiation and the application of very high temperatures and pressure, which require a lot of energy and expense.

The new method efficiently decomposes fluoride only after exposure to light at room temperature under normal atmospheric pressure. In addition, recovered fluoride ions can be used for other purposes.

However, the method's practical application is not yet in sight because the research is still in the experimental stage, involving only small amounts of PFAS. The group said the method has the potential to significantly contribute to the recycling of fluorine compounds.

"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 realise the practical application as soon as possible."