Raman imaging of membrane fouling

Membrane processes are widely used in industrial applications such water purification, food processing and pharmaceutical manufacturing. During their operation, the accumulation of foulants in membrane pores and on membrane surfaces lead to the reduction in flux, membrane lifetime and increase in operational cost, and the understanding of the fouling phenomenon is important for mitigating these problems. In this paper we report the application of Raman chemical imaging as a means of identify and map foulants on a membrane surface. The surface of a Polytetrafluoroethylene (PTFE) membrane was studied by Raman chemical imaging before and after fouling during desalination via membrane distillation. Information about location and concentration of three different salts namely CaSO₄, BaSO₄ and CaCO₃ was studied. The three salts showed different distribution patterns, and their distribution was analyzed by correlation mapping and multivariate curve resolution. It was observed that CaSO₄ agglomerated in specific places while the BaSO₄ and CaCO₃ were more distributed. Raman imaging appears to be a powerful tool for studying membrane foulants and can be effective in identifying the distribution of different species on a membrane surface.