Improved separation performance and durability of polyamide reverse osmosis membrane in tertiary treatment of textile effluent through grafting monomethoxy-poly(ethylene glycol) brushes

To improve the separation performance and durability of the aromatic polyamide thin-film composite reverse osmosis membrane in tertiary treatment of textile effluent, grafting of hydrophilic polymer brushes was performed in this work through sequential surface treatment using acidic aqueous glutaraldehyde and monomethoxy-poly(ethylene glycol) (MPEG) solutions. ATR-FTIR and XPS analyses confirmed that MPEG brushes were grafted on membrane surface at the sites of NH group of amide linkages and end amino groups in the polyamide active layer. The modification was found to enhance membrane fouling resistance, water permeability and rejections to both COD and conductivity in tertiary treatment of textile effluent. The steady-state flux of the modified membrane to secondary textile effluent was higher by 24.0% compared with the virgin membrane and comparable with that of the commercial membrane BW30FR. The grafting of MPEG brushes was also found to make the membrane less susceptible to chlorine. After ten times of intensified chlorine exposure, i.e. total chlorine exposure of 42,000 ppmh NaClO of 35.0 °C and pH 9.0, the membrane grafted with MPEG brushes maintained COD and conductivity rejections of 97.9% and 98.5%, respectively, to textile effluent, showing better durability against chlorine than the virgin membrane and compared membrane BW30FR.