Ultrathin sulfonated mesoporous interlayer facilitates to prepare highly-permeable polyamide nanofiltration membranes

Highly-permeable nanofiltration (NF) membranes are strongly required and have become more crucial with increasing concerns in water treatment and purification. Herein a versatile approach is developed to prepare a highly-permeable polyamide (PA) NF membrane via the traditional interfacial polymerization (IP) process facilitated by an ultrathin sulfonated mesoporous interlayer. A series of the interlayers with a thickness of 110–250 nm and a cut-off around 12 nm is prepared and employed to prepare the PA NF membrane from piperazine (PIP) and 1, 3, 5-benzotriformyl chloride (TMC). Influence factors on the membrane preparation including the interlayer thickness and monomer concentrations are investigated in detail. Sulfonic groups on the interlayer greatly facilitate the PIP adsorption and thus increase the PIP storage in the interlayer, resulting in the formation of a defect-free, 10–50 nm-thick PA membrane at a low monomer concentration. The thickness and surface roughness of PA layer increase with the interlayer thickness simultaneously. Typically, the 40 nm-thick PA membrane has a pure water permeance of high to 36.3 L m−2 h−1 bar−1 with a Na2SO4 rejection of 98.5%. The newly developed approach has a wide application in the preparation of highly-permeable PA membranes for various fields including water treatment and chemical separation.