4.2 Article

Experimental and Theoretical Insight of Perfluorooctanoic Acid Destruction by Alkaline Hydrothermal Treatment Enhanced with Zero-Valent Iron in Biochar

Journal

ACS ES&T WATER
Volume 3, Issue 5, Pages 1286-1293

Publisher

AMER CHEMICAL SOC
DOI: 10.1021/acsestwater.2c00614

Keywords

PFOA degradation mechanisms; hydrothermal alkaline treatment; zero-valent iron immobilized in biochar (BC-VZI); mechanism analysis; density functional theory (DFT) analysis

Ask authors/readers for more resources

This study demonstrates the synergistic effect between alkaline-thermal treatment and zero-valent iron immobilized in biochar (BC-ZVI) for the enhanced degradation of perfluorooctanoic acid (PFOA). The use of 19F-NMR and density functional theory (DFT) analysis provided insights into the defluorination efficiency and degradation mechanisms. The results showed that alkaline strength played a primary role in the defluorination process, and BC-ZVI improved the reaction kinetics by 2.4 times. The combination of alkaline-thermal treatment and BC-ZVI resulted in near-complete removal of fluorinated compounds within a short reaction time.
This study demonstrates the complementarity between alkaline-thermal treatment and zero-valent iron immobilized in biochar (BC-ZVI) for enhanced degradation of perfluorooctanoic acid (PFOA). New and complementary research techniques, including 19F-NMR and density functional theory (DFT) analysis were used to evaluate defluorination efficiency and elucidate possible degradation mechanisms. The defluorination of PFOA was governed primarily by alkaline strength while BC-ZVI could enhance reaction kinetics by 2.4 times. Adsorption of the intermediates to BC-ZVI resulted in near-complete removal of all fluorinated compounds (with the exception of perfluoracetic acid) in the aqueous phase within 15 min of reaction. After 4 h of alkaline hydrothermal treatment (240 degrees C and 250 mM NaOH) with BC-ZVI, defluorination efficiency of PFOA of 99.7% was observed. Perfluoracetic acid was the only persistent byproduct but accounted only for less than 1% of the initial PFOA. DFT analysis also showed that strong alkaline conditions could decrease the reaction energy barrier by 73.9% due to the decarboxylation of PFOA via nucleophilic substitution. In addition to Kolbe decarboxylation, the profile of intermediate products and DFT analysis results suggest that PFOA was degraded by other mechanisms leading to near-complete and effective defluorination.

Authors

I am an author on this paper
Click your name to claim this paper and add it to your profile.

Reviews

Primary Rating

4.2
Not enough ratings

Secondary Ratings

Novelty
-
Significance
-
Scientific rigor
-
Rate this paper

Recommended

No Data Available
No Data Available