Membrane technologies have attracted growing interest in the fields of water purification and energy recovery. Membrane fouling is the bottleneck that limits the wide application of membrane-based technologies. Exploration of the fouling mechanism and the chemical composition, structure, and functions of foulants and their changes in the membrane filtration process is therefore of significant importance. Molecular spectroscopic methods are among the most efficient platform tools for characterizing membrane fouling because of their unique advantages, such as chemical identification at the molecular level, high sensitivity, and spatially temporally resolved feasibility. Here, an overview of spectroscopic and microspectroscopic approaches, including UV-vis, fluorescence, infrared, and Raman spectroscopy, for the online detection, identification, visualization, and chemical characterization of membrane fouling is provided, and their main advantages as well as limitations in membrane-fouling research are analyzed. Furthermore, future possibilities and challenges for the development of molecular spectroscopy for membrane-fouling characterization are envisaged in this critical review.

膜技术在水净化和能量回收领域引起了越来越多的兴趣。膜污染是限制膜技术广泛应用的瓶颈。因此，探索结垢机理以及结垢剂的化学组成，结构和功能及其在膜过滤过程中的变化非常重要。分子光谱法因其独特的优势而成为表征膜污染的最有效平台工具之一，例如在分子水平上进行化学鉴定，高灵敏度和在空间上可解析的可行性。在这里，我们将概述光谱和显微方法，包括紫外线可见光谱，荧光光谱，红外光谱和拉曼光谱，以进行在线检测，鉴定，提供了膜污染的可视化和化学表征，并分析了它们的主要优点以及在膜污染研究中的局限性。此外，在这一关键性的综述中，设想了用于膜污染表征的分子光谱学的发展的未来可能性和挑战。