Novel sulfonated thin-film composite nanofiltration membranes with improved water flux for treatment of dye solutions

In this paper, two types of novel sulfonated aromatic diamine monomer, 2,5-bis(4-amino-2-trifluoromethyl-phenoxy)benzenesulfonic acid (6FAPBS) and 4,4′-bis(4-amino-2-trifluoromethyl-phenoxy)biphenyl-4,4′-disulfonic acid (6FBABDS), were synthesized and used to prepare the thin-film composite (TFC) nanofiltration (NF) membranes. Two series of sulfonated TFC NF membranes were prepared on a microporous polyphenylsulfone (PPSU) support membrane through an interfacial polymerization technique with trimesoyl chloride (TMC) solution and amine solutions containing 6FAPBS/6FBABDS and piperazine (PIP), and their properties including chemical composition, membrane morphology and hydrophilicity of the active layer were characterized by ATR-IR, XPS, SEM and contact angle measurement. After that, these resultant membranes were employed to perform dye treatment experiments with aqueous solutions of rhodamine B and methyl orange. The membranes prepared under the optimum condition showed an increase in the water flux by improving surface hydrophilicity which was enhanced by the presence of sulfonated aromatic diamine monomers without compromising the rejection of dyes. The introduction of sulfonic acid groups plays a major role in water permeation and rejection of dyes during TFC NF separation process.