Destruction and defluorination of PFAS matrix in continuous-flow supercritical water oxidation reactor: Effect of operating temperature

Conrad Austin; Jianna Li; Stuart Moore; Anmol Purohit; Brian R Pinkard; Igor V Novosselov

doi:10.1016/j.chemosphere.2023.138358

Destruction and defluorination of PFAS matrix in continuous-flow supercritical water oxidation reactor: Effect of operating temperature

Chemosphere. 2023 Jun:327:138358. doi: 10.1016/j.chemosphere.2023.138358. Epub 2023 Mar 9.

Authors

Conrad Austin¹, Jianna Li², Stuart Moore¹, Anmol Purohit¹, Brian R Pinkard³, Igor V Novosselov⁴

Affiliations

¹ University of Washington, Mechanical Engineering Department, Seattle, WA, 98195, USA.
² University of Washington, Mechanical Engineering Department, Seattle, WA, 98195, USA; Key Laboratory of Thermo-Fluid Science and Engineering of MOE, Energy and Power Engineering, Xi'an Jiaotong University, 28 Xianning West Road, Xi'an, 710049, China.
³ University of Washington, Mechanical Engineering Department, Seattle, WA, 98195, USA; Aquagga, Inc., Tacoma, WA, 98402, USA.
⁴ University of Washington, Mechanical Engineering Department, Seattle, WA, 98195, USA. Electronic address: ivn@uw.edu.

PMID: 36906000
DOI: 10.1016/j.chemosphere.2023.138358

Abstract

Cleanup and disposal of stockpiles and waste streams containing per- and polyfluoroalkyl substances (PFAS) require effective end-of-life destruction/mineralization technologies. Two classes of PFAS, perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs), are commonly found in legacy stockpiles, industrial waste streams, and as environmental pollutants. Continuous flow supercritical water oxidation (SCWO) reactors have been shown to destroy several PFAS and aqueous film-forming foams. However, a direct comparison of the SCWO efficacy for PFSAs and PFCAs has not been reported. We show the effectiveness of continuous flow SCWO treatment for a matrix of model PFCAs and PFSAs as a function of operating temperature. PFSAs appear to be significantly more recalcitrant than PFCAs in the SCWO environment. The SCWO treatment results in a destruction and removal efficiency of 99.999% at a T > 610 °C and at a residence time of ∼30 s. Fluoride recovery lags destruction PFAS at 510 °C and reaches >100% above 610 °C, confirming the formation of liquid and gaseous phase intermediate product during lower temperature oxidation. This paper establishes the threshold for destroying PFAS-containing liquids under SCWO conditions.

Keywords: Defluorination; Destruction; PFAS; Supercritical water oxidation; Waste treatment.

MeSH terms

Carboxylic Acids
Fluorocarbons* / analysis
Sulfonic Acids
Temperature
Water
Water Pollutants, Chemical* / analysis
Water Purification*

Substances

Water
Carboxylic Acids
Sulfonic Acids
Water Pollutants, Chemical
Fluorocarbons