In flow-through reactors, the photodegradation rate can be enhanced by better contact and an increase in photocatalyst loading. Both can be attained with a higher surface-to-volume ratio. While previous work focused on thin membranes (30 – 130 µm) with small pore sizes of 20 – 650 nm, this work was performed with poly(tetrafluoroethylene) (PTFE) supports. The pore sizes are in the order of 10 µm, while porosity 22.5 − 45.3% and thickness 0.2 − 3 mm are variable. It was anticipated that these porous materials would enable enhanced loading of the porphyrin photosensitiser and better light penetration for subsequent photodegradation of steroid hormone micropollutants via singlet oxygen (¹O₂) generation. The reactor surface refers to the surface within the PTFE pores, while the reactor volume is the total void space inside these pores. The surface-to-volume ratio falls between 10⁵ and 10⁶ m²/m³, higher than those of typical microreactors (10³ to 10⁴ m²/m³). The weighted average light transmittance varied from 38% with the thinnest and most porous support to 4.8% with the thickest support. Good light penetration combined with minimal absorption by PTFE enhanced the light utilisation of the porphyrins when coated in the porous supports.Changes in the support porosity of the coated supports affected insignificantly steroid hormone removal, because the collision frequency in the very large pores remained relatively constant. However, varying the support thickness, porphyrin loading (0.3 − 7.7 μmol/g), and water flux (150 − 3000 L/m².h), and the resulting HRT influenced the collision frequency and steroid hormone removal. Results were not competitive with membranes, most likely owing to the larger pore size limiting contact between micropollutants and reactive oxygen species.From photostability testing of the pristine supports, perfluoroalkyl substances (PFAS) released from the supports were found at 10 − 300 ng/L concentrations during accelerated ageing. This indicates that some PFAS are released, while quantities during water treatment operations would be extremely low. In summary, this study elucidates the capability and limitations of porous supports coated with photosensitisers to remove waterborne micropollutants.

中文翻译：

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不同形态和光学特性的钯-卟啉包覆多孔 PTFE 对类固醇激素微污染物进行光降解


在流通式反应器中，可以通过更好的接触和增加光催化剂负载来提高光降解速率。两者都可以通过更高的表面体积比来实现。虽然以前的工作集中在具有 20 – 650 nm 小孔径的薄膜 （30 – 130 μm） 上，但这项工作是使用聚四氟乙烯 （PTFE） 载体进行的。孔径约为 10 μm，而孔隙率 22.5 − 45.3% 和厚度 0.2 − 3 mm 是可变的。预计这些多孔材料将能够增强卟啉光敏剂的负载，并更好地渗透光，以便通过单线态氧 （¹O₂） 生成随后对类固醇激素微污染物进行光降解。反应器表面是指 PTFE 孔内的表面，而反应器体积是这些孔内的总空隙空间。表面体积比在 10⁵ 到 10⁶ m²/m³ 之间，高于典型微反应器的表面体积比（10³ 到 10⁴ m²/m³）。加权平均透光率从最薄和孔隙率最强的支撑的 38% 到最厚支撑的 4.8% 不等。良好的光穿透性加上 PTFE 的最小吸收，增强了卟啉在多孔载体中涂覆时的光利用率。涂层支撑物的支撑孔隙率的变化对类固醇激素的去除影响不大，因为非常大的孔隙中的碰撞频率保持相对恒定。然而，改变支撑厚度、卟啉负载 （0.3 − 7.7 μmol/g） 和水通量 （150 − 3000 L/m^2.h） 以及由此产生的 HRT 会影响碰撞频率和类固醇激素去除。 结果与膜没有竞争力，很可能是由于较大的孔径限制了微污染物和活性氧之间的接触。通过对原始载体的光稳定性测试，在加速老化过程中发现，从载体中释放的全氟烷基物质 （PFAS） 浓度为 10 − 300 ng/L。这表明释放了一些 PFAS，而水处理操作期间的 PFAS 数量将非常低。总之，本研究阐明了涂有光敏剂的多孔载体去除水生微污染物的能力和局限性。