# Far-UVC (222 nm) Enhances the Advanced Reduction Process for Per- and Polyfluoroalkyl Substance (PFAS) Destruction

## TL;DR

This study shows that using 222 nm UVC light with sulfite improves the breakdown of harmful PFAS chemicals in water more efficiently than traditional methods.

## Contribution

The integration of far-UVC (222 nm) with sulfite-based advanced reduction processes significantly enhances PFAS degradation efficiency and energy performance.

## Key findings

- UV222/sulfite systems generate more hydrated electrons, leading to better PFAS degradation.
- UV222/sulfite achieved 85% PFOS removal and 66% defluorination in 6 hours.
- Dissolved organic matter and carbonates strongly scavenge reactive species, reducing efficiency.

## Abstract

The UV-based advanced reduction processes (ARPs) have
emerged as
an effective strategy to degrade PFAS contaminants in water. This
study investigates PFAS degradation by integrating far-UVC irradiation
at 222 nm with sulfite-based ARPs. Comparative analysis of UV222/sulfite
and conventional UV254/sulfite revealed that UV222/sulfite systems
significantly improve the performance by generation of more hydrated
electrons (eaq
–), the primary reactive
species driving PFAS degradation, and exhibit superior energy efficiency,
characterized by lower electrical energy per order (E

EO
). The higher efficiency of UV222/sulfite
can be attributed to stronger light absorption of sulfite and higher
photon energy at 222 nm. Under optimized stepwise sulfite dosing conditions,
the UV222/sulfite ARP achieved high perfluorooctyl sulfonic acid (PFOS)
removal efficiency, nearly 85% reduction in parent compound and 66%
defluorination within a 6 h period, while the degradation of shorter-chain
PFHxS and PFBS was slower. Real water matrix components can influence
treatment efficiency. The impacts of nitrate/nitrite were transient
and diminished after rapid photolysis at 222 nm, while dissolved organic
matter and carbonates exerted strong reactive species scavenging effects.
This study establishes UV222/sulfite ARP as a promising strategy to
enhance PFAS degradation. Careful optimization of UV222/sulfite system
parameters and water matrices will increase the adaptability for environmental
PFAS remediation.