Nanoscale polyelectrolyte/metal ion hydrogel modified RO membrane with dual anti-fouling mechanism and superhigh transport property

Abstract The anti-fouling polyamide (PA) reverse osmosis (RO) membranes modified by hydrophilic polymer are trapped in the problems of declined flux, single anti-fouling mechanism, high cost or complex fabrication. Here the nano-sized sodium alginate/Cu2+ hydrogel prepared with the layer-by-layer (LBL) method was firstly applied for PA RO membrane modification to solve these contradictions. The combination of passive and active antifouling capabilities can be imparted by the polyelectrolyte hydrogel cross-linked with metal ions. In addition, remarkable transport properties can be achieved by brilliant hydrophilicity of hydrogel layer and LBL method which can control the thickness of the modified layer at nanometer level to minimize the transmembrane resistance of water molecules. The modified membrane possesses a water flux of 71.40 LMH up to 192.97% of the unmodified membrane without sacrificing salt rejection at 25 °C, 1.6 MPa. In the BSA and DTAB fouling tests, the flux recovery rate of the modified membrane was 26.44% and 29.14% greater than that of the unmodified membrane, respectively. Moreover, the modified PA membrane exhibited great bactericidal potential to S. aureus and E. coli. Besides prominent comprehensive performance, this strategy is low cost and simple in operation, shining a light on preparing new generation of high-performance RO membrane.