Use of surface enhanced Raman spectroscopy for studying fouling on nanofiltration membrane

Abstract

Membrane fouling is a key constraint for the widespread application of membrane-based technologies in water and wastewater treatment because it reduces the production volume of water, thereby increasing operating and maintenance costs. Characterization of membrane materials and foulant layers is crucial for an accurate understanding of fouling processes. This study used surface-enhanced Raman spectroscopy (SERS) and normal Raman spectroscopy as a novel technique to examine fouling caused by naturally occurring organics on a polymeric nanofiltration (NF) membrane, which is used for the treatment of drinking water. The results from this study suggest that normal Raman spectroscopy is useful for characterization of polyamide NF membranes used in drinking water treatment, but is not sensitive enough to resolve the foulant materials present on the membrane surface. Scanning electron microscopy (SEM) analysis of virgin and used membrane suggests significant membrane fouling. The observed SERS peak of fouled membrane at wavenumber 1543cm−1 suggests the presence of protein and those at 1444, 1305, and 1239cm−1 indicate the possible presence of carbohydrate on the membrane surface. These results demonstrate that SERS has the potential for identification of functional groups of organics involved in NF membrane fouling in water treatment that could lead to improved strategies for membrane fouling reduction. The use of SERS for possible foulant identification offers a rapid, cost effective and portable tool for on-site analysis of membrane surfaces.