Carbon nanotube-supported polyamide membrane with minimized internal concentration polarization for both aqueous and organic solvent forward osmosis process

Abstract

We proposed a novel strategy for fabricating a high-performance forward osmosis (FO) membrane by forming a polyamide (PA) selective layer via interfacial polymerization on top of an interconnected porous carbon nanotube (CNT) network support. The fabricated CNT-PA membrane had a highly permeable and selective PA layer for fast water and solvents passage with efficient salt and solutes rejection, and an ultrathin CNT support that significantly reduced the internal concentration polarization in the FO process. Tested in the FO (e.g., active layer facing feed solution) mode using DI water as feed solution and 1.0 M NaCl as draw solution, the optimal CNT-PA membrane exhibited a water flux of as high as 139 L m−2 h−1(LMH)with comparable salt rejection, 686% higher than that of commercial FO membrane, outperforming the previously reported best FO membranes tested under similar conditions. Besides, the CNT-PA membrane also showed great capability to recover organic solvents such as ethanol (EtOH), dimethylsulfoxide (DMSO), dimethylformamide (DMF) and dimethylacetamide (DMAc) when used in the organic solvent forward osmosis (OSFO) process and to concentrate chemicals in organic solvents. Results present that the CNT-PA membrane exhibited a DMAc flux of around 20 LMH with near 100% rhodamine B dye rejection and a negligible reverse solute flux when using 2.0 M PEG400 as a draw solution. The contributions of the CNT support layer and the PA selective layer to the osmotic filtration performance of the CNT-PA membrane were investigated and discussed to provide insights on the FO membrane design and fabrication for the efficient separation in aqueous and organic solvent system.