Preparation of loose polypiperazine amide membranes. Effect of the nanocomposite sublayer on the NF process performance

•Novel thin film nanocomposite membranes were prepared.•Nanoparticles were added into the membrane sublayer.•The nanocomposite sublayer shows an effect on the NF process performance.•Addition of SBA(COOH) enhanced the NF membrane permeability and sulphate rejection.

Novel nanofiltration (NF) membranes were prepared by interfacial polymerization using four different nanocomposite membranes as sublayers. The nanocomposite sublayers were prepared by immersion precipitation method, dispersing nanoparticles such as TiO2, SBA-15 and functionalized SBA-15 with carboxylic groups (SBA-15(COOH)). The physico-chemical properties of the sublayers were studied by means of cross section morphology, pore diameter, pore density, contact angle and roughness by SEM and FEG-SEM. The successful incorporation of the thin film layer was evaluated by FT-IR. The addition of the nanoparticles increased the pore density and hydrophilic character of the ultrafiltration (UF) sublayers. Results showed that the nanocomposite sublayers can improve the process performance of the thin film composite membrane. In this study, the most significant performance improvement was observed on the NF with SBA-15(COOH) doped sublayer, achieving permeability values in the UF range (56.3 dm3/m2 hbar) and successful MgSO4 rejection coefficients (68.3%). Results also show that there is no strong influence between the physical parameters of the sublayers and NF process performance. Therefore, it was concluded that the COOH functional group of the nanoparticle SBA-15(COOH) might have interfered in the interfacial polymerization process, leading to more permeable and selective NF membranes.