Loose polyamide nanofiltration membranes reinforced with MXene via constrained interfacial polymerization

To achieve loose polyamide (PA)-based nanofiltration membranes with high water permeability and salt selectivity, two-dimensional layered material MXene (Ti3C2Tx) and piperazine (PIP) were co-deposited onto the surface of polyacrylonitrile (PAN) substrate membranes to facilitate constrained interfacial polymerization (IP) between PIP and trimesoyl chloride (TMC). The negatively charged MXene, rich in oxygen-containing functional groups, adsorbs PIP molecules, thereby constraining the IP process and leading to the formation of an ultra-thin PA/MXene layer with a thickness of less than 100 nm on the PAN substrate. Additionally, MXene nanosheets promote the creation of extra nanochannels between the MXene and PA due to microphase separation. The effects of the mass ratio of MXene to PIP, TMC concentration, and MXene deposition on the nanofiltration performance of the composite membrane were systematically optimized. As a result, the optimized PA/MXene/PAN membrane demonstrates a permeate flux of 152.4 L m(-)2 h(-)1 and a rejection rate of 97.2% to sodium sulfate at 0.6 MPa. This outstanding separation performance underscores the significant potential of MXene-assisted IP in developing high-performance PA desalination membranes.