In situ nanoporous structural characterization of asymmetric hollow fiber membranes for desalination using Raman spectroscopy

Abstract Observing the nanoporous structure inside membranes has been one of the greatest challenges in membrane research, and many recent studies have employed positron annihilation lifetime spectroscopy, among other methods, to gain structural insights. In this report, we demonstrate the significant potential of Raman spectroscopy for investigating the nanoporous structure inside membranes under in situ conditions. Sulfonated poly(arylene ether sulfone) and cellulose triacetate asymmetric hollow fiber membranes were fabricated and their nanoporous structures were examined using Raman spectroscopy. The membrane dimensions, mechanical properties, and reverse osmosis (RO) performances were also measured. The membrane structures estimated by Raman spectroscopy correlated very well with the mechanical properties and RO performances. This study indicated that Raman spectroscopy represents a promising method for detecting the nanoporous structures inside membranes for desalination applications, and furthermore, that it would be a good tool for developing membranes with optimized nanoporous structures.