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

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.