A novel kind of PAN/CP/PA nanofiltration (NF) composite membranes was fabricated by interfacial polymerization

while piperazine (PIP) was used as aqueous phase monomer and trimesoyl chloride (TMC) was chosen as organic phase monomer to prepare a polypiperazine-amide (PA) barrier layer based on polyacrylonitrile (PAN) nanofibrous substrate modified by carbopol (CP) gel (a bionic adhesive).FTIR results showed that hydrogen bonds were formed between carboxyl groups (COOH) of CP and cyano groups (CN) of PAN

while ionic bonds of carboxylic acid ammonium salt (COO-H2N+) were obtained by neutralization reaction between carboxyl groups of CP and secondary amine groups of PIP.Then interactions of each layer in composite membranes were enhanced.PAN/PA composite membranes and PAN/CP/PA composite membranes were prepared by the same interfacial polymerization process based on PAN and PAN/CP nanofibrous substrates

respectively.Tensile test results indicated that the PAN substrate and PA barrier layer of composite membranes were firmly bonded together by CP gel to form an integrated structure of composite membranes.The resulting tensile strength of composite membranes was increased from 15.1 MPa to 24.2 MPa.Compared with PAN/PA composite membranes

PAN/CP/PA membranes had similar water flux but possessed better rejection rates for different kinds of nitrate salts and MgCl2

which may be attributed to that the PAN/CP/PA composite membrane was strongly negative-charged according to a great amount of carboxyl groups of CP.