Preparation and properties of polyamide/titania composite nanofiltration membrane by interfacial polymerization

• We added TiO2 sol instead of TiO2 nano-particles to make PSF/TiO2 hybrid membrane.
• The polymerization reaction happened on the surface of PSF/TiO2 hybrid membrane.
• The addition of TiO2 sol changed the salt rejection slightly.
• The water flux increased three times after adding proper TiO2 sol.

The TiO2 sol was added in the polysulfone (PSF) casting membrane solution to prepare polysulfone/titania hybrid membrane in this work. Then the polypiperazine–amide composite nanofiltration (NF) membranes were prepared on PSF/TiO2 hybrid membranes by interfacial polymerization. Piperazine and trimesoyl chloride were used as monomers in aqueous phase and organic phase, respectively. Different preparation conditions affecting the separation performances of NF membrane were discussed, including TiO2 sol concentration, piperazine concentration, trimesoyl chloride concentration, and reaction time. The chemical structure characterizations of polyamide composite membrane were tested by attenuated total reflectance infrared (ATR-IR). The surface images and cross sections were observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The addition of TiO2 sol changed the salt rejection slightly, but the water flux was three times than that of the polyamide membrane on the PSF support membrane. The polyamide NF membrane prepared under the optimum condition exhibited Na2SO4 rejection of 96.94% and water flux of 12.84 L m− 2 h− 1. According to the intercepting experiments of polyethylene glycols, the molecular weight cut-off (MWCO) of the resulting membrane was under 600 Da.