Near-UV light drives PFAS defluorination in new zinc oxide catalyst study
Iain Hoey
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A cheap material is breaking PFAS bonds faster than expected
Ritsumeikan University researchers have reported that ligand-capped zinc oxide (ZnO) nanocrystals can defluorinate perfluorooctanesulfonic acid (PFOS) under near-UV light, with results published online in Chemical Science on Wednesday 5 November 2025.
Perfluoroalkyl substances (PFASs) were described as synthetic chemicals used for heat, water and oil resistance.
The university said PFAS persistence is linked to the high energy required to break the carbon–fluorine (C–F) bond.
It described defluorination as removing fluorine atoms to make PFAS compounds more susceptible to further breakdown.
PFAS defluorination under ambient light
The study tested ZnO nanocrystals capped with acetic acid (AA–ZnO NCs) and 3-mercaptopropionic acid (MPA–ZnO NCs), along with other organic ligands for comparison.
The defluorination experiments used 365 nm LED light, which the researchers said mimics ambient lighting conditions.
Professor Yoichi Kobayashi, Professor at Ritsumeikan University, said: “Perfluorooctanesulfonic acid or PFOS is a PFAS compound that was once widely used but is now strictly regulated, and we wanted to see if ligand-capped ZnO NCs can defluorinate it,”
The team also tested the ligand-capped ZnO nanocrystals on other PFASs including trifluoroacetic acid and Nafion.
Efficiency results and key numbers
AA–ZnO nanocrystals achieved up to a 92% defluorination rate after 24 hours under optimised conditions.
MPA–ZnO nanocrystals achieved 8.4% defluorination after 24 hours.
The researchers reported that the acetic acid ligand produced higher defluorination efficiency than 3-mercaptopropionic acid in the PFOS tests.
Durability and repeat-use testing
The team also tested durability and changes in catalytic efficiency over time across multiple cycles.
It reported that a single ZnO nanocrystal could break up to 8,250 C–F bonds during the decomposition reaction.
The researchers described ZnO nanocrystals as low-toxicity, inexpensive and suitable for production at scale.
Mr. Shuhei Kanao, researcher at Ritsumeikan University, said: “The reaction occurs at room temperature and does not require high-energy light sources, which can be costly, fragile, or hazardous,”
Potential applications named by researchers
Ritsumeikan University said the system could be used to tackle industrial PFAS pollution and support PFAS recycling.
It listed fluorochemical materials manufacturing units, semiconductor manufacturing units, the recycling industry and wastewater treatment facilities as potential use settings.
Professor Yoichi Kobayashi, Professor at Ritsumeikan University, said: “PFAS pollution is a worldwide concern, and this simple NC-based technology could contribute significantly to tackling this issue,”
What this could mean for industrial contamination control
Wastewater treatment facility managers and environmental risk leads in industrial sites may track this work because it targets PFOS using 365 nm LED light under ambient conditions.
Fire safety officers and facility managers in semiconductor manufacturing units may also be interested because the researchers named that sector as a potential use setting.
Procurement teams and equipment specifiers supporting the recycling industry could compare this room-temperature photodegradation approach with methods that rely on harsh chemicals or high energy inputs, as described by the university.
Environmental compliance teams working in fluorochemical materials manufacturing may watch follow-on work because the researchers framed the method as a way to address PFAS recycling challenges.
The reported durability data, including repeated-cycle operation and the 8,250 C–F bond figure per nanocrystal, may be relevant for evaluating whether a catalyst can be reused in a process setting.