Treating perfluorooctanoic acid (PFOA) in an aqueous environment is problematic due to its low concentration and its high resistance to biological and chemical degradation. To tackle this challenge, combinations of pre-enrichment and photodegradation processes are promising solutions. In this work, we investigated metal ion-exchanged zeolites as adsorbents and photocatalysts for PFOA treatment. Among various transition metal ion-exchanged BEA zeolites, Fe-exchanged BEA (Fe-BEA) zeolites showed significant activity for the photodegradation of PFOA. The isolated iron species in Fe-BEA zeolite are responsible for PFOA photodegradation, whereas other iron species present from excess iron loading in the zeolite will lower its photocatalytic activity. Furthermore, it was proved via size exclusion tests using branched PFOA isomers that the photodegradation of PFOA took place on the internal surface rather than the external surface of Fe-BEA zeolite. Photodegradation of PFOA was also tested to be effective with Fe-exchanged BEA-type zeolites having various SiO₂/Al₂O₃ ratios, but ineffective with FAU-type zeolites. The optimal Fe-BEA zeolite showed a sorption coefficient K_d of 6.0 × 10⁵ L kg^–1 at an aqueous phase PFOA concentration of 0.7 μg L^–1 and a PFOA half-life of 1.8 h under UV-A irradiation. The presented study offers a deeper understanding of the use of metal ion-exchanged zeolites for photodegradation of PFOA.

中文翻译：

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使用金属离子交换沸石深入了解全氟辛酸光降解

由于全氟辛酸（PFOA）浓度低且对生物和化学降解具有很强的抵抗力，因此在水环境中处理全氟辛酸（PFOA）是有问题的。为了应对这一挑战，预富集和光降解过程的组合是有前途的解决方案。在这项工作中，我们研究了金属离子交换沸石作为 PFOA 处理的吸附剂和光催化剂。在各种过渡金属离子交换BEA沸石中，Fe交换BEA（Fe-BEA）沸石对PFOA表现出显着的光降解活性。Fe-BEA 沸石中的孤立铁物质负责 PFOA 光降解，而沸石中过量铁负载所存在的其他铁物质会降低其光催化活性。此外，通过使用支化PFOA异构体的尺寸排阻测试证明，PFOA的光降解发生在Fe-BEA沸石的内表面而不是外表面。_{还测试PFOA的光降解对于具有各种SiO 2} /Al ₂ O ₃比率的Fe交换的BEA型沸石是有效的，但对于FAU型沸石是无效的。最佳Fe-BEA沸石在水相PFOA浓度为0.7 μg L ^{–1时的吸附系数}K _d为6.0 × 10 ⁵ L kg ^–1，在UV-A照射下PFOA半衰期为1.8 h。本研究提供了对使用金属离子交换沸石光降解 PFOA 的更深入的了解。