High performance membranes circumventing the global water scarcity are emerging from exquisite nanofabrication but the materials preparation complexity and permeability stability remain challenges. We report here that both the permeability and antibacterial property of piperzine-trimesoyl chloride (PIP-TMC) polyamide nanofiltration membranes were improved through simple surface modification by a strong electrolyte monomer bearing a multiple of amines and quaternary ammonium (Quaternized diaminoethylpiperzine, QAEP). The new monomer reacts effectively with residual acyl chloride groups on pristine membranes, bringing about the synergy of improved hydrophilicity with surface microstructures that facilitates high way path for transmembrane transportation of water molecules. The PIP-TMCQAEP membrane exhibit high salt rejection (RNa2SO4 = 97.8%, RMgSO4 = 94.2%), coupled with high permeate flux (96 L m-2 h-1, feed: 1 g L-1 Na2SO4, 6 bar) that is 3 times as high as that of the PIP-TMC membranes. Meanwhile the membrane features a high salt selectivity (30) in processing NaCl/Na2SO4 mixed solution (10 g L-1), coupled with satisfactory performances against fouling and biofouling and elongated continuous operation time (12 days). 

https://www.sciencedirect.com/science/article/pii/S0376738819306301#appsec1