Assessing the oxidative degradation of polyamide reverse osmosis membrane—Accelerated ageing with hypochlorite exposure

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

“…The peak at 1610 cm −1 is representative of the C=C stretching vibrations from the aromatic amide bonds [20,38]. 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.…”

“…Once in contact with chlorinated oxidants, the active PA layer is degraded through a number of suggested reaction pathways including Nchlorination of amine groups and aromatic ring chlorination, which can be summarised as the weakening of PA intermolecular hydrogen bond interactions with the incorporation of chlorine [18,19]. In addition, limited evidence has also been presented that the supporting layers of the membrane were unaffected by moderate chlorine exposure [20].Another significant factor affecting membrane performance is the method used for storage and transportation.…”

“…However, radical chemical treatment on used RO membranes could facilitate conversion for additional applications. The effects of oxidative degradation and long-term chlorine exposure have been well documented [18,19], and the literature suggests that removing the active layer of a retired RO membrane via oxidative degradation has the potential to result in a separation device that has a similar physical structure to standard polyethersulfone (PES) UF membranes [28][29][30]. This technique of oxidative chemical treatment to remove the PA active layer of the RO membrane resulting in an UF membrane is referred to as membrane conversion.…”

Degradation of polyamide reverse osmosis membranes in the presence of chloramine

“…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.…”

Evaluation of MF and UF as pretreatments prior to RO applied to reclaim municipal wastewater for freshwater substitution in a paper mill: A practical experience

“…Before entering RO membranes, feed water passes through a 5 µm cartridge filter forced by a low pressure pump (3.5-4.0 bar), then 4 mg·L -1 anti-scalant (PermaTreat®PC-191, Nalco Company, Naperville, Illinois, USA) and 8 mg·L -1 sodium bisulphite (NaHSO 3 ) were dosed to remove any trace of free chlorine to avoid the oxidation of the polyamide [35,36].…”