Construction of Carbon Nanotube-based Composite Membrane with Electron-ion Double Transfer Function and its Electrically Driven Ion Separation Performance

Abstract

The construction of electroactive ion separation membranes with dual functions of electron and ion transfer is a key technology in the field of electronchemically switched ion permselectivity membrane (ESIPM) separation. In this paper, CNT/CNF composite membranes with three-dimensional porous structure in submicron scale were prepared by blending and filtration of conducting carbon nanotubes (CNT) and cellulose nanofibers (CNF). Using CNT/CNF composite membranes as conductive base membrane, the SPS/CNT/CNF composite membrane with dual electron and ion transfer function was prepared by in situ filling of sulfonated polystyrene (SPS) with cation exchange function into the nano-micron channel of CNT/CNF without destroying the structure of CNT crosslinking network through solution penetration strategy. The structure and properties of CNT/CNF membrane were characterized by SEM, XRD, FTIR, and contact angle test. The ion separation performance of CNT/CNF membrane and SPS/CNT/CNF membrane was systematically compared on an electrodrive membrane separation tester. The results show that the SPS/CNT/CNF composite membrane has the cation separation ability equivalent to commercial ion exchange membrane, and has excellent electrical conductivity with an electrical conductivity 7 orders of magnitude higher than that of traditional inert ion exchange membrane. In addition, the SPS/CNT/CNF composite membrane also has excellent electrochemical activity, hydrophilicity, and stability. This study provides a novel synthesis strategy for the preparation of high performance ESIPM.

Keywords

• carbon nanotube
• sulfonated polystyrene
• cellulose nanofibers
• electrochemically switched ion permselectivity
• conductivity