Effect of amine salt surfactants on the performance of thin film composite poly(piperazine-amide) nanofiltration membranes

The role of amine salt surfactants on the performance of thin film composite nanofiltration (TFC NF) membranes is crucial for the development of advanced NF membranes, but the information is still not enough. This paper presents a systematic investigation of the effect of the types of amine salt surfactants on nanofiltration performance. Four types of amine salts with different molecular structures, molecular weights (MW) and charges, including tetraethylammonium chloride (TEAC), tetrabutylammonium bromide (TBAB), camphorsulfonic acid triethylamine salt (CAS-TEA), and 1-butyl-3-methylimidazolium chloride (BMMIC), were incorporated into piperazine (PIP) solution during interfacial polymerization(IP) with trimesoyl chloride (TMC). The formed thin film composite (TFC) piperazine–amide polymer was supported on a polyethersulfone (PES) ultrafiltration membrane (UF). The membrane surfaces were characterized by scanning electronic microscopy (SEM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS). The flux and NaCl rejection were also evaluated. The addition of amine salt containing larger steric configuration cationic amine group in aqueous solution, resulted in a TFC membrane with better performance, and the amine salt would act as a surfactant and not adhere to the polymer layer at the end of polymerization.