Reliable and adequate removal of small and uncharged trace organic chemicals, particularly N-nitrosodimethylamine (NDMA) that is carcinogenic and known to occur in treated effluent, is essential for implementing direct potable water use. This study provides new insights to explain the low rejection of NDMA and other N-nitrosamines by reverse osmosis (RO) membranes by examining the role of molecular size and polarity in their molecular structure. The results show that molecular weight is not a suitable molecular property for evaluating the rejection of small uncharged chemicals. In this study, NDMA and two other uncharged chemicals have similar molecular weights (i.e., 72–74 g/mol), but their rejection by the ESPA2 RO membrane varied considerably from 30 to 88%. Instead, a minimum projection area was identified as a more suitable molecular property, indicating that size exclusion plays a primary role in their rejection. It was also determined that chemicals with more nitrogen atoms in their chemical structure consistently showed rejections lower than those of their similarly sized counterparts. The results suggest that chemicals bearing more nitrogen atoms (e.g., NDMA) have higher affinity to amide or amine functional group of a polyamide RO membrane possibly through hydrogen bonding interactions.

中文翻译：

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N-亚硝胺通过反渗透膜的运输：分子大小和氮原子的作用。

可靠，充分地去除少量不带电的微量有机化学物质，尤其是已知致癌的N-亚硝基二甲基胺（NDMA），在处理后的废水中会发生，这对于实现直接饮用水的使用至关重要。这项研究提供了新的见解来解释NDMA和其他N的低拒绝率-亚硝胺通过反渗透（RO）膜检测分子大小和极性在其分子结构中的作用。结果表明，分子量不适合用于评估小的不带电化学物质的排斥性。在这项研究中，NDMA和其他两种不带电荷的化学物质具有相似的分子量（即72–74 g / mol），但是它们被ESPA2 RO膜的截留率从30％到88％相差很大。取而代之的是，将最小投影面积确定为更合适的分子特性，表明尺寸排阻在其排斥中起主要作用。还确定化学结构中具有更多氮原子的化学药品始终显示出比同等大小的同类产品更低的拒绝率。结果表明，带有更多氮原子的化学物质（例如