Scaling remains a serious barrier to membrane-based desalination. While some real-time techniques have proven effective for scaling detection, none provides the crucial capability of chemical identification with high temporal and spatial resolution under realistic operating conditions. In this work, we describe a real-time technique for detection of early stage scaling via chemical quantification using Raman spectroscopy. Experiments utilized a custom bench-scale flow cell integrated with a commercial Raman microscope that accesses the membrane through a 10 mm optical window. Calcium sulfate was used as a model foulant at high concentration (1.8 g/L) to minimize the time required for membrane scaling. The experiments were conducted with a commercial brackish water reverse-osmosis thin film composite membrane operating at a feed pressure of 1.17 MPa (170 psi) and a feed flow velocity of 4.7–5.6 cm/s. Raman measurements were made in real time at a laser excitation wavelength of 785 nm. Real-time results were validated with post-mortem SEM and energy-dispersive X-ray analysis and indicated the capability to detect early-stage scaling characterized by a relatively modest reduction in the permeate flow rate.

中文翻译：

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拉曼光谱法实时检测反渗透膜结垢

结垢仍然是基于膜的脱盐的严重障碍。尽管已证明某些实时技术可有效地进行水垢检测，但在现实操作条件下，没有一种技术能够提供具有高时空分辨率的化学识别的关键功能。在这项工作中，我们描述了一种实时技术，用于通过使用拉曼光谱的化学定量检测早期结垢。实验利用定制的台式规模流通池，该流通池与商用拉曼显微镜集成在一起，可通过10毫米光学窗口进入膜。硫酸钙用作高浓度（1.8 g / L）的模型污垢剂，以最大程度地减少膜结垢所需的时间。实验是使用市售微咸水反渗透薄膜复合膜在进料压力为1的条件下进行的。17 MPa（170 psi），进料流速为4.7-5.6 cm / s。拉曼测量是在785 nm的激光激发波长下实时进行的。实时结果已通过事后SEM和能量色散X射线分析进行了验证，并表明了能够检测早期水垢的能力，其特征是渗透流量的相对适度降低。