Insight into mechanochemical destruction of PFOA by BaTiO3: An electron-dominated reduction process

Li Li; Ruoning Guo; Jie Gao; Jie Liu; Zhiwei Zhao; Xin Sheng; JunYu Fan; Fuyi Cui

doi:10.1016/j.jhazmat.2023.131028

Insight into mechanochemical destruction of PFOA by BaTiO₃: An electron-dominated reduction process

J Hazard Mater. 2023 May 15:450:131028. doi: 10.1016/j.jhazmat.2023.131028. Epub 2023 Feb 16.

Authors

Li Li¹, Ruoning Guo¹, Jie Gao¹, Jie Liu², Zhiwei Zhao³, Xin Sheng¹, JunYu Fan², Fuyi Cui¹

Affiliations

¹ Key Laboratory of Eco-environments in Three Gorges Reservoir Region, Ministry of Education, College of Environment and Ecology, Chongqing University, Chongqing 400045, PR China.
² Department of Military Facilities, Army Logistics Academy, Chongqing 401311, PR China.
³ Key Laboratory of Eco-environments in Three Gorges Reservoir Region, Ministry of Education, College of Environment and Ecology, Chongqing University, Chongqing 400045, PR China. Electronic address: hit_zzw@163.com.

PMID: 36857827
DOI: 10.1016/j.jhazmat.2023.131028

Abstract

Perfluorooctanoic acid (PFOA) is a representative persistent organic pollutant and its disposal by mechanochemical (MC) technology emerges in recent years. However, degradation mechanism of PFOA especially rupture of C-F bonds during MC process is still unclear. Therefore, we innovatively employed barium titanate as co-milling reagent in MC system to disclose an electron-dominated reduction process. By stimulating piezoelectric effect of BaTiO₃ under MC impact, free electrons were generated. The results implied more than 95.00% degradation and 60.00% defluorination efficiency were obtained after 6 h' ball milling. DPPH• was used as probe to confirm the existence of piezo-excited electrons, which were further verified to be major reactive species by atmosphere experiments. Thus, PFOA destruction was dominated by reduction process, characterizing by breakage of C-F bonds induced by electrons. Accordingly, the fate of organic fluorides was explored and BaF₂ was identified as final product. The cleavage of carboxyl group initiated PFOA decomposition, following by successive removal of CF₂ groups and elimination of F^-. Moreover, the practical experiments and reusable trials implied promising application of this method. Overall, this paper provides a novel perspective for reductive decomposition of PFOA by MC technology and reveals the major role of electrons during reaction process.

Keywords: Electron transfer; Mechanochemical degradation; Perfluorooctanoic acid; Piezoelectric effect; Reduction process.