Preparation of expandable vertically aligned carbon nanotube arrays/polydimethylsiloxane membrane by a modular splicing method and its application in in situ ethanol recovery from ethanol fermentation

Aligned carbon nanotube (CNT) arrays have been widely used in the preparation of polymer composites. CNT arrays are commonly prepared by chemical vapor deposition (CVD) in a high temperature tubular furnace, and the areas of the aligned CNT/polymer membranes prepared are relatively small (<30 cm²) due to the limitation of the inner diameter of the furnace, which limits its practical application in the field of membrane separation. Herein, the vertically aligned CNT arrays/polydimethylsiloxane (PDMS) membrane with large and expandable area was prepared by a modular splicing method for the first time, with a maximum area of 144 cm². The addition of CNT arrays with openings at both ends significantly improved the pervaporation performance of the PDMS membrane for ethanol recovery. At 80 °C, the flux (671.6 g m^-2 h^-1) and separation factor (9.0) of CNT arrays/PDMS membrane were increased by 435.12% and 58.52%, respectively, compared with those of the PDMS membrane. Furthermore, the expandable area enabled the CNT arrays/PDMS membrane to couple with fed-batch fermentation for pervaporation for the first time, which increased the ethanol yield (0.47 g g^-1) and productivity (2.34 g L^-1 h^-1) by 9.3% and 4.9% respectively compared with batch fermentation. Besides, the flux (135.47-166.79 g m^-2 h^-1) and separation factor (8.83-9.21) of CNT arrays/PDMS membrane remained stable in this process, indicating that this membrane has the potential to be applied in industrial bioethanol production. This work provides a new idea for the preparation of large-area aligned CNT/polymer membranes, and also opens up a new direction for the application of large-area aligned CNT/polymer membranes.