Enhanced water-selective performance of dual-layer hybrid membranes by incorporating carbon nanotubes

Water-selective membranes are utilized in many fields such as wastewater treatment, desalination, organic solvent dehydration. In this study, dual-layer hybrid membranes were designed and prepared through electrostatic interactions for ethanol dehydration. The polyethyleneimine (PEI) with carboxyl decorated carbon nanotubes (CNT-C) was spin-coated on porous hydrolyzed polyacrylonitrile (HPAN) substrate as one active layer and then coated with sodium alginate (Alg) layer as another active layer. The hydrophobic outside surface of CNT-C provided the abundant paths for the fast water transport, which facilitated the water permeation. Meanwhile, the incorporated CNT-C increased the surface roughness and enhanced the hydrophilicity of the membranes. PEI improved the dispersion of CNT and interfacial compatibilities within membranes. The resultant dual-layer hybrid membranes acquired enhanced separation performance when utilized for pervaporation dehydration of 90 wt% ethanol aqueous solution. The permeation flux was increased by 15% to 2825 g/(m2h) and the separation factor was increased by 1.70 times to 2148, compared with the Alg/PEI/HPAN membrane