Investigation of Poly(ethersulfone)/Polyvinylpyrrolidone ultrafiltration membrane degradation by contact with sodium hypochlorite through FTIR mapping and two-dimensional correlation spectroscopy

It is well recognized that chlorine is responsible for aging of membrane materials. The goal of this study is to investigate the modifications of a commercial PES/PVP hollow fiber membrane exposed to hypochlorite solution at pH 7.5 by continuous filtration. Thanks to ATR-FTIR 2D Correlation Spectroscopy (2DCoS) analysis it was confirmed that PVP is oxidized into succinimide compound. 2DCoS analysis revealed the sequence order of PES/PVP membrane degradation: PVP oxidation is followed by the modifications of C-H cyclic structures and finally the formation of succinimide compounds. ATR-FTIR-microscopy mapping unveiled that PVP was mainly situated at the inner surface of hollow fibers exhibiting initially a 67 μm thickness layer. PVP layer disappearance was not homogenous versus the exposure dose suggesting the topochemical character of the PVP-chlorine reaction. Results demonstrate that advanced material characterization are key methodologies to understand membrane aging mechanisms.