A novel positively charged nanofiltration membrane stimulated by amino-functionalized MXene Ti3C2Tx for high rejection of water hardness ions

The demand to address issues such as drinking water safety and industrial fouling caused by high-hardness ions has still emphasized the development of advanced membrane materials. In this study, through a maneuverable amide-cross-linking strategy, a new positively-charged polyamide (PA) nanofiltration membrane was developed for the first time by incorporating amino-functionalized Ti3C2Tx nanoparticles (Ti3C2Tx-NH2, TN). In addition to the induced electropositivity, the hydrophilicity of the as-obtained PA-TN membrane was also elevated with a maintained nodular structure by tailoring the interfacial polymerization reaction process of piperazine (PIP) with trimesoyl chloride (TMC). Therefore, the newly developed PA-TN membrane exhibited both superhigh rejection of Ca2+ and Mg2+ over 96%, and the flux increased 2-3 times even for the salinity solutions than many similar NF membranes reported in literature. Furthermore, the enhanced long-term stability and fouling resistance of the PA-TN membrane was also validated due to its new organic-inorganic structural coupling and improved hydrophilicity. This work provides a new strategy for the preparation of organic-inorganic hybrid positively charged nanofiltration membranes for water softening treatment.