Hydrodefluorination of Perfluorooctanoic Acid in the H2-Based Membrane Catalyst-Film Reactor with Platinum Group Metal Nanoparticles: Pathways and Optimal Conditions

Min Long, Welman C. Elias, Kimberly N. Heck, Yi Hao Luo, Yen Jung Sean Lai, Yan Jin, Haiwei Gu, Juan Donoso, Thomas P. Senftle, Chen Zhou, Michael S. Wong, Bruce E. Rittmann

Research output: Contribution to journalArticlepeer-review

Abstract

PFAAs (perfluorinated alkyl acids) have become a concern because of their widespread pollution and persistence. A previous study introduced a novel approach for removing and hydrodefluorinating perfluorooctanoic acid (PFOA) using palladium nanoparticles (Pd0NPs) in situ synthesized on H2-gas-transfer membranes. This work focuses on the products, pathways, and optimal catalyst conditions. Kinetic tests tracking PFOA removal, F release, and hydrodefluorination intermediates documented that PFOA was hydrodefluorinated by a mixture of parallel and stepwise reactions on the Pd0NP surfaces. Slow desorption of defluorination products lowered the catalyst’s activity for hydrodefluorination. Of the platinum group metals studied, Pd was overall superior to Pt, Rh, and Ru for hydrodefluorinating PFOA. pH had a strong influence on performance: PFOA was more strongly adsorbed at higher pH, but lower pH promoted defluorination. A membrane catalyst-film reactor (MCfR), containing an optimum loading of 1.2 g/m2 Pd0 for a total Pd amount of 22 mg, removed 3 mg/L PFOA during continuous flow for 90 days, and the removal flux was as high as 4 mg PFOA/m2/d at a steady state. The EPA health advisory level (70 ng/L) also was achieved over the 90 days with the influent PFOA at an environmentally relevant concentration of 500 ng/L. The results document a sustainable catalytic method for the detoxification of PFOA-contaminated water.

Original languageEnglish (US)
Pages (from-to)16699-16707
Number of pages9
JournalEnvironmental Science and Technology
Volume55
Issue number24
DOIs
StatePublished - Dec 21 2021

Keywords

  • hydrodefluorination
  • nanoparticle
  • palladium
  • perfluorooctanoic acid (PFOA)

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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