Abstract The polyamide skin layer of reverse osmosis (RO) membranes was characterised using advanced and complementary analytical techniques to investigate the mechanisms underlying the permeation of contaminants of emerging concern in potable water reuse – N -nitrosodimethylamine (NDMA) and N -nitrosomethylethylamine (NMEA). This study used five RO membrane samples with similar membrane properties. The five RO membrane samples spanned over a large range of water permeance (0.9–5.8 L/m 2 h bar) as well as permeation of NDMA (9–66%) and NMEA (3–29%). Despite these differences among the five RO membranes, characterisations of the skin layer using positron annihilation lifetime spectroscopy, atomic force microscopy and field emission scanning electron microscopy revealed almost no variation in their free-volume hole-radius (0.270–0.275 nm), effective surface area (198–212%) and thickness (30–35 nm) of the skin layer. The results suggest that there could be other RO skin layer properties, such as the interconnectivity of the protuberances within the polyamide skin layer additional to the free-volume hole-size and thickness of the skin layer, which can also govern water and solute permeation.

中文翻译：

---

小分子和中性溶质通过反渗透膜的传输：聚酰胺薄膜表层构象的作用

摘要 反渗透 (RO) 膜的聚酰胺表层使用先进的互补分析技术进行表征，以研究饮用水再利用中新出现的污染物 - N-亚硝基二甲胺 (NDMA) 和 N-亚硝基甲基乙胺 (NMEA) 的渗透机制. 本研究使用了五个具有相似膜特性的 RO 膜样品。五个 RO 膜样品跨越了大范围的水渗透率（0.9–5.8 L/m 2 h bar）以及 NDMA (9–66%) 和 NMEA (3–29%) 的渗透率。尽管五种 RO 膜之间存在这些差异，但使用正电子湮没寿命光谱、原子力显微镜和场发射扫描电子显微镜对表层的表征显示它们的自由体积孔半径（0.270-0.275 nm）几乎没有变化，表层的有效表面积 (198–212%) 和厚度 (30–35 nm)。结果表明，可能存在其他 RO 表层特性，例如除了自由体积孔尺寸和表层厚度之外的聚酰胺表层内突起的互连性，这也可以控制水和溶质的渗透。