High permselectivity thin-film composite nanofiltration membranes with 3D microstructure fabricated by incorporation of beta cyclodextrin

Based on the Freeman theory, tailoring polymer backbone stiffness can improve membrane performance. Therefore, a rigid monomer—bisphenol F—to enhance the backbone stiffness of polyester/polyamide was utilized to prepare high performance nanofiltration (NF) membranes in the previous work. Here, the three-dimensional (3D) hollow-bowl-structure monomer—beta cyclodextrin (β-CD)—is added into the polyester/polyamide backbone to fabricate a 3D-microstructure NF membrane. With the incorporation of β-CD, the pure water flux (PWF) increases by 68% (up to 152 L m−2 h−1, 0.6 MPa), while the rejection of Na2SO4 remains high (96.8%). Surprisingly, such NF membrane exhibits a very low rejection of NaCl (1.1%) and high rejection of Na2SO4 (up to 95.8%) when dealing with a Na2SO4/NaCl mixed solution. The fabricated 3D-microstructure NF membrane shows the potential to be applied in the monovalent/divalent anion separation field.