Efficient PFOA degradation using UiO-66-NH2 photocatalytic coupled persulfate activation: synergistic effect of surface radicals and photogenerated holes

Perfluorooctanoic acid (PFOA) has attracted growing attention due to its widespread occurrence and harmful effects on humans. Owing to the strong C F bonds that confer inherent stability on PFOA, achieving efficient degradation via traditional photocatalysts is highly challenging. In this study, a UiO-66-NH 2 photocatalytic-persulfate (UiO-66-NH 2 /PS) integrated system was constructed to achieve high-efficiency PFOA removal, and its underlying mechanism was systematically revealed. A zirconium-based metal–organic framework, UiO-66-NH 2 , with readily tunable porosity was successfully synthesized via a solvothermal route, and its crystal structure, microstructure, and optical absorption behavior were confirmed through comprehensive characterizations. After optimization of the reaction parameters, the UiO-66-NH₂/PS system exhibited excellent PFOA degradation performance, with a markedly enhanced removal efficiency relative to the single UiO-66-NH 2 or persulfate system. The degradation efficiency of UiO-66-NH 2 /PS system in degrading PFOA was affected by ubiquitous anions and humic acid in water. Investigation of degradation pathways revealed that the cooperative action of photogenerated holes and SO₄• − /•OH radicals progressively cleaved the recalcitrant C F bonds, with short-chain perfluorocarboxylic acids (PFCAs) including perfluoroheptanoic acid (PFHpA, C 6 F 13 COOH), perfluorohexanoic acid (PFHxA, C 5 F 11 COOH), perfluoropentanoic acid (PFPeA, C 4 F 9 COOH), and perfluorobutyric acid (PFBA, C 3 F 7 COOH) identified as the main degradation intermediates. This study proposed a high-efficiency, economical and eco-friendly approach for the mineralization of PFOA, and meanwhile shed new light on the mechanism underlying the efficient degradation of PFOA by UiO-66-based photocatalysis combined with persulfate activation.