Abstract Forward osmosis (FO) and reverse osmosis (RO) membrane processes differ in their driving forces: osmotic pressure versus hydraulic pressure. Concentration polarization (CP) can adversely affect both performance and lifetime in such membrane systems. In order to mitigate against CP, the extent and severity of it need to be predicted more accurately through advanced online monitoring methodologies. Whilst a variety of monitoring techniques have been used to study the CP mechanism, there is still a pressing need to develop and apply non-invasive, in situ techniques able to produce quantitative, spatially resolved measurements of heterogeneous solute concentration in, and adjacent to, the membrane assembly as caused by the CP mechanism. To this end, 23Na magnetic resonance imaging (MRI) is used to image the sodium ion concentration within, and near to, both FO and RO composite membranes for the first time; this is also coupled with 1H MRI mapping of the corresponding water distribution. As such, it is possible to directly image salt accumulation due to CP processes during desalination. This was consistent with literature expectations and serves to confirm the suitability of 23Na MRI as a novel non-invasive technique for CP studies.

中文翻译：

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使用 23Na 核磁共振的 NaCl 膜浓差极化成像

摘要 正向渗透 (FO) 和反渗透 (RO) 膜工艺的驱动力不同：渗透压与液压。浓度极化 (CP) 会对此类膜系统的性能和寿命产生不利影响。为了减轻 CP，需要通过先进的在线监控方法更准确地预测 CP 的范围和严重程度。虽然已经使用了多种监测技术来研究 CP 机制，但仍然迫切需要开发和应用非侵入性的原位技术，能够对其中和附近的异质溶质浓度进行定量、空间分辨的测量，由 CP 机制引起的膜组件。为此，使用 23Na 磁共振成像 (MRI) 对内部的钠离子浓度进行成像，并首次接近 FO 和 RO 复合膜；这也与相应水分布的 1H MRI 映射相结合。因此，可以直接对由于脱盐过程中的 CP 过程造成的盐分积累进行成像。这与文献预期一致，并有助于证实 23Na MRI 作为 CP 研究的一种新型非侵入性技术的适用性。