▎ 摘　　要

Herein, a graphene oxide (GO)-modified piperazine (PIP) nanofiltration (NF) membrane was successfully fabricated via in situ interfacial polymerization of PIP-GO and trimesoyl chloride on a porous substrate, in which GO induced a wrinkled membrane surface with improved roughness and hydrophilicity and reduced electronegativity. Ion separation tests show that GO increases the water flux of the membranes significantly by 10-15 LMH for all the studied salt solutions. Furthermore, GO can selectively increase the retention of CaCl2 and MgCl2, but slightly decrease the rejection of MgSO4, NaCl, and KCl; this indicates an improvement in the separation performance of the PIP-GO membrane between divalent and monovalent cations with a common counter ion, Cl- . The enhanced water permeation of the PIP-GO membrane can be ascribed to its increased surface area, hydrophilicity, and ultrafast water transport between GO nanosheets. The GO-promoted selective ion separation is the result of an attenuated electrostatic attraction between Ca2+, Mg2+, and the membrane as well as the water flow-accelerated transport of Na+ and K+. Therefore, GO-modified NF membranes exhibit great potential for applications in the areas of water purification and separation.