Evolution of Membrane Fouling Revealed by Label-Free Vibrational Spectroscopic Imaging.

Membrane fouling is the bottleneck that restricts the sustainability of membrane technology for environmental applications. Therefore, the development of novel analytical tools for characterizing membrane fouling processes is essential. In this work, we demonstrate a capability of probing the chemical structure of foulants and detecting their 3-dimentional spatial distribution on membranes based on stimulated Raman scattering (SRS) microscopy as a vibrational spectroscopic imaging approach. The adsorption process of foulants onto membrane surfaces and their aggregation process within membrane pores during the microfiltration of protein and polysaccharide solutions were clearly monitored. Pore constriction and cake layer formation were found to be the coupled membrane fouling mechanisms. This work establishes an ultrafast, highly sensitive, nondestructive and label-free imaging platform for the characterization of membrane fouling evolution. Furthermore, this work provides new insights into membrane fouling and offers a powerful tool for membrane-based process exploration.