Ultrathin cyclodextrin nanofilm composite membranes for efficient separation of xylene isomers

Abstract

Molecule separation membranes with high flux and precise sieving are promising for discriminating xylene isomers. However, the thick separation layer (>300 nm) and dense inner structure with wide pore size distribution generally restrict the further development. Here, we demonstrate the preparation of novel thin-film composite membranes with sub-10 nm cyclodextrin (CD) nanofilms that are cross-linked on thin vermiculite (Vr) lamellar layer through electrostatic atomization-assisted interfacial polymerization technology. The regular Vr layer provides smooth and hydrophilic platform for synthesizing ultrathin and defect-free CD nanofilms. The as-prepared composite membranes achieve precise separation for xylene isomers and benzene derivatives based on size sieving effect using the intrinsic cavities in CDs. Meanwhile, the ultrathin CD nanofilms and regular Vr layer jointly contribute to fast molecule transfer. Specifically, TFC membrane with β-CDs nanofilm attains separation factor (SF) of 6.7 and 6.1 for p-xylene/m-xylene (PX/MX) and p-xylene/o-xylene (PX/OX), respectively, with the PX permeance of 7.9 and 7.8 L m−2 h−1 bar−1. Moreover, the SF for cyclohexane/1,3,5-triisopropyl benzene reaches as high as 46.8 by membrane with α-CD nanofilm. In addition, these TFC membranes exhibit favorable structural and operational stabilities, providing insight into practical separation applications.