Unveiling the Susceptibility of Functional Groups of Poly(ether sulfone)/Polyvinylpyrrolidone Membranes to NaOCl: A Two-Dimensional Correlation Spectroscopic Study

Abstract

A clear understanding of membrane aging process is essential for the optimization of chemical cleaning in membrane-based facilities. In this study, two-dimensional (2D) Fourier transformation infrared (FTIR) correlation spectroscopy (CoS) analysis was first used to decipher the sequential order of functional group changes of NaOCl-aged poly(ether sulfone)/polyvinylpyrrolidone (PES/PVP) membranes. The synchronous maps showed 12 major autopeaks in total. Based on the asynchronous maps, a similar aging sequence of membrane groups was clearly identified at three pHs (i.e., 6, 8, and 10): 1463, 1440, and 1410 (cyclic C-H structures) > 1662 (amide groups) > 1700 (succinimide groups) > 1320, 1292 (S═O asymmetric) > 1486, 1580 (aromatic structures) > 1241 (aromatic ether bands) > 1105, 1150 cm (O═S═O symmetric). Among them, membrane chlorination occurred at 1241, 1410, and 1440 cm. Moreover, the initial degradation of PVP and the subsequent transformation of PES could be highly responsible for the increased water permeability and the enlargement of membrane pores, respectively, both leading to serious fouling with humic acid filtration. In summary, the 2D-FTIR-CoS analysis is a powerful approach to reveal the interaction mechanisms of NaOCl-membrane and could be also useful to probe the process of membrane fouling and chemical cleaning.

Effects of Hydrogen Peroxide and Sodium Hypochlorite Aging on Properties and Performance of Polyethersulfone Ultrafiltration Membrane

“…For pristine membrane, apart from several characteristic peaks of PES (i.e., 1580, 1486, 1320, 1292, 1241, 1150, 1105 cm −1 ) exhibiting high absorption intensity, an obvious band at 1668 cm −1 was observed. The band at 1668 cm −1 represents the stretching vibration of the amide unit in PVP, and its intensity has been extensively used as an indicator of the content of PVP [16,34,35,36,37]. Similar to previous studies, NaClO aging caused decrease of intensity of the peak at 1668 cm −1 due to PVP oxidation /dislodgement, and new peaks at 1700 and 1772 cm −1 representing oxidation products of PVP were observed.…”

“…However, permeability of membranes aged by NaClO at pH 9 and 11 were increased to 5.75 and 3.84 times of that of the pristine membrane, respectively. Although the extent of increase varied depending on exposure dose and aging conditions, permeability increase of PES membrane due to NaClO aging has been reported in many studies [13,16,17,32,33,34], and it was commonly attributed to the increase of pore size and porosity [11]. The similar permeability of pristine, control, and H 2 O 2 -aged membranes suggested that pore structure of the PES membrane was not altered obviously by alkaline or H 2 O 2 under the aging conditions in this work.…”

“…In each filtration test, 350 mL of HA solution was added to the filtration cell, and filtration was carried out under a TMP of 60 kPa until the permeate volume reached 300mL. Based on initial and final permeate flux as well as permeate volume per unit membrane surface area, the unified membrane fouling index (UMFI) can be calculate to evaluate membrane fouling propensity [16,31]. With respect to retention ability, HA concentrations of feed solution ( C f ) and permeate ( C p ) were measured in terms of UV absorbance at 254 nm using a UV/Vis spectrophotometer (U-3900, Hitachi, Tokyo, Japan).…”

“…As for the main polymer (i.e., PES) with much higher chemical stability, several studies have reported PES chain scission and/or hydroxylation of PES aromatic rings [13,14,15]. Besides, it was reported that degradation of PES membrane by NaClO was more serious under neutral to weak alkaline conditions, which has been attributed to the formation of hydroxyl radical [14,16,17].…”

Sharp fluorescence nanofiber network of CdSe/CdS core-shell nanoplatelets in polyvinylpyrrolidone

“…It could be seen that there was no obvious difference between the PVP and nanofiber network be- cause the embedding content of NPLs was very low. There were a number of absorption characteristics of PVP observed in the FTIIR curves, the bond at 1663 cm −1 is assigned to the C− −O vibration of the amide groups, and the bond located at 1439 cm −1 and 1391 cm −1 were assigned with the cyclic C−H structures of pyrrolidine in PVP [32]. Moreover, the peaks at 2982 cm −1 and 2875 cm −1 were related to the stretching vibration of C−H and the broad band from 3583 cm −1 to 3081 cm −1 related to the overlap of the stretching vibrations of O−H group with N−H group [33].…”