Polyamide–surfactant interaction: Exploration of new avenues for reverse osmosis separation applications

Abstract

AbstractThin‐film composite (TFC) RO membrane has got widespread acceptability for desalination and water reuse applications. A novel approach toward modification of surface of TFC RO membrane using surfactant (anionic, cationic, and nonionic) has been presented. Anionic surfactant, sodium dodecyl sulfate, increased the water flux of TFC RO membrane up to 142% when TFC RO membrane was exposed to sodium hypochlorite solution of 2,000 mg/L for 2 hr followed by sodium dodecyl sulfate for 1 hr at pH 11. However, surface modification by cationic surfactant, that is, cetrimonium bromide resulted in decreased water flux. Boron rejection decreased to 87.31% when cetrimonium bromide of 500 mg/L was exposed after 2,000 mg/L sodium hypochlorite at pH 11 because of positive charge on the membrane surface. Nonionic surfactant Triton X‐100 exposure lower than critical micelle concentration, that is, 100 mg/L for 1 hr after sodium hypochlorite exposure of 2,000 mg/L for 2 hr, resulted in increased water flux of about 22%, however, on increasing surfactant concentration more than critical micelle concentration, that is, 4% with the same sodium hypochlorite pre‐exposure, resulted in 47.5% decline in water flux. Thus, surfactant can bind the top barrier layer of polyamide membrane to alter its performance.