Study on hypochlorite degradation of aromatic polyamide reverse osmosis membrane

Production and characterisation of UF membranes by chemical conversion of used RO membranes

“…The converted membrane exhibits suppression and possibly elimination of the characteristic aromatic polyamide peaks which has been previously shown to be an indication of chlorine damage via the mechanism of Orton rearrangement [18]. When comparing these results to previous studies on free chlorine damage to PA membranes, the relative peak suppression is extreme and nearly complete [19,39], a difference which can be explained by the significantly higher oxidant exposures used. This suppression corresponds to breaking of various bonding groups and the subsequent deterioration of the chemical structure.…”

Degradation of polyamide reverse osmosis membranes in the presence of chloramine

“…1540 cm -1 decreases in intensity and undergoes a slight hypochromic shift with exposure. The peak at 1487 cm -1 corresponds to a characteristic peak (CH 2 stretch) of polysulfone [52] whereas the peak at 1540 cm -1 corresponds to the C-N stretch of the PA (II) group [18]. It appears that the polysulfone layer of this material is not affected by the chloramine solution as evidenced by the unchanged characteristic peak however a chemical change in the PA structure has occurred as a result of chloramine exposure.…”

“…Changes in chemical composition of the membrane samples were measured regularly using spectroscopic techniques [18]. Horizontal attenuated total reflectance (HATR) infrared spectroscopy and specular reflectance spectroscopy were used to measure changes in major …”

“…The effects of chlorination on RO membranes that are made of PA have been widely reported in the literature [10][11][12][13][14][15][16][17][18]. Generally these studies conclude that chlorine causes irreversible damage to the PA membrane resulting in a loss of membrane integrity.…”

“…Fourier-transform infrared (FTIR) spectroscopy is a valuable analytical technique that is typically used qualitatively to assess the structures and changes in materials such as PA membranes [18,[32][33][34][35] [39]. The usefulness of this technique can extend to quantitative analyses that can reveal more detailed information regarding changes in polymer structures that are the result of degradation or other physical and/or chemical changes.…”