Synchrotron Fourier transform infrared mapping: A novel approach for membrane fouling characterization.

We described a synchrotron-based infrared (IR) microscopic method to characterize fouling layer induced by organic foulants and colloidal silica in membrane distillation (MD). This technique, utilizing the ultrahigh brightness of synchrotron infrared source, enables spectra with high signal-to-noise ratio that was obtained from micrometer-sized samples. Our results showed that synchrotron IR mapping was able to resolve the foulant spatial distribution in combined fouling in MD. Synchrotron IR mapping showed the spatial distribution of binary foulant (i.e., colloidal silica with alginate, bovine serum albumin (BSA) or humic acid, respectively) of the cross-section of MD membrane fouling layer. The well-resolved synchrotron IR mapping is also able to quantify the foulant distribution along the cross-section of the fouled MD membrane, providing detailed information regarding the transport and accumulation of specific foulant, which is of paramount importance to elucidate fouling mechanisms. Our results demonstrated that the synchrotron IR mapping method was a powerful method and had significant potential for both qualitative and quantitative characterization of membrane fouling layer.