Nanofiltration membrane with CM-β-CD tailored polyamide layer for high concentration cephalexin solution separation

Nanofiltration (NF) is a promising technique to achieve sustainable and efficient separation of antibiotics with high industrial value. In this work, carboxymethyl-β-cyclodextrin (CM-β-CD) modified nanofiltration membrane was fabricated through interfacial polymerization (IP) for high concentration cephalexin solution separation, which is a classic antibiotic pharmaceutical wastewater. In principle, CM-β-CD can slow down the diffusion of amine monomers via electrostatic attraction, steric effect, hydrogen bonding and adsorption of the piperazine (PIP) monomer onto the hydrophilic surface, which renders amine monomer the high local concentration. The fabricated NF membranes possessed a larger proportion of dense primary layer on the surface. In addition, the accumulation of CM-β-CD between the substrate membrane and polyamide (PA) layer played the role as a barrier with specific cavity structure and bulk carboxylate to enhance the rejection of cephalexin. The cavity structure and stacking gap of CM-β-CD simultaneously rendered the membrane interlayer highly permeable. The optimal CM-β-CD modified membrane exhibited high rejection of cephalexin (94.7%) and water permeability of 122.4 L m−2 h−1 MPa−1 when the concentration of cephalexin was 3473.9 ppm (10 mmol/L). This work furnished an available way to prepare a novel nanofiltration membrane with efficient separation performance for relevant pharmaceutical production wastewater.