The Effect of Halogens on the Performance and Durability of Reverse-Osmosis Membranes

Preparation, characterization and chlorine stability of aromatic–cycloaliphatic polyamide thin film composite membranes

“…The likely reactions are: (1) chlorination of amide N H group to N Cl group followed by Orton rearrangement of chlorine to amine aromatic ring leading to polyamide chain degradation and (2) direct chlorination of the aromatic ring of the diamine unit leading to a change in membrane surface morphology [17]. The decrease in water flux of chlorine exposed membranes has been attributed to the increase in the hydrophobic character of the polyamide layer [11], and membrane tightening [12,13] upon the conversion of amide N H group to N Cl group.…”

“…The mechanism of chlorine attack on aromatic polyamides and polyamide membranes has been investigated by several researchers in order to understand the cause of performance change due to chlorination [11][12][13][14][15][16][17][18][19][20]. Several chemical changes in polyamides upon exposure to free chlorine have been reported.…”

“…These changes include: (1) chlorination of the amide N H group to form N Cl group, (2) Orton rearrangement, i.e., initial chlorination of the amide N H group to N Cl group followed by rearrangement of chlorine to aromatic ring of diamine unit, and (3) direct chlorination of the aromatic ring of the diamine unit. Thus, the decrease in membrane performance has been attributed to several factors like increase in hydrophobic character of the polyamide layer [11], tightening of the polyamide layer [12,13], physical separation of the polyamide skin layer [14], etc., upon chlorine addition to polyamide chain. Based on the above observations, it has been opined that polyamides containing tertiary amide linkage (polymers derived from secondary diamines and acid chlorides) and also polyamides derived from aliphatic diamines (which do not undergo Orton rearrangement leading to polymer degradation) would have better chlorine resistant characteristics.…”

Evaluation of Military Field-Water Quality. Volume 7. Performance Evaluation of the 600-GPH Reverse Osmosis Water Purification Unit (ROWPU): reverse Osmosis (RO) Components

“…The ROWPU'g were operated again for 35 h during 3-4 December 1082. and then were shut down until 16 December 1982, Another failure was evidenced at that time with the passage of large salt concentrations, The system was repaired and the ROWPU's were operated successfully for another 81 h until 21 December 1982. The system failures appai'ently were caused by leaks into the product"water tubes owing to structural failure of an end-cap product-water seal, 6 9 The ROWPUs' operational and performence data were taken on at hourly basis whenever possible by the Air Force personnel, Unfortunately, water temperature and feed-water TDS could not be ascertained until 16 December 1082 because of logistical problems.,9 The data for one of the two 600-gph ROWPU's were averaged for two periods, 18 November to 4 December 1982 and from 16 to 21 December 1982, as shown in Table 28, Observations made during system failures were not included in these averages.…”

A novel method of surface modification on thin-film-composite reverse osmosis membrane by grafting hydantoin derivative

“…The free chlorine in feed solution can cause the degradation of polyamide TFC RO membranes and ultimately results in membrane failure as measured by enhanced passages of both water and salt [17]. Membrane degradation/failure is attributed to certain structural changes within the aromatic polyamide in response to chlorine exposure [18][19][20]. Normally, it is considered that these changes mainly include N-chlorination by substituting the hydrogen on amide nitrogen, followed by ring-chlorination via an intermolecular rearrangement called Orton rearrangement [17,21].…”