Single-walled carbon nanotube buckypaper as support for highly permeable double layer polyamide/zeolitic imidazolate framework in nanofiltration processes
11 figures, 1 table.-- Supplementary information available. ; The development of membranes for nanofiltration applications requires not only selective layers but also suitable supports to control their synthesis as well as to enable efficient and competitive membrane performances. Single-walled carbon nanotube free-standing films (denoted as buckypaper) have been used as supports for the preparation of polyamide (PA) layers by interfacial polymerization (IP) and tested for dead-end nanofiltration for dyes removal (265–1017 Da) from water and organic solvents. The arrangement of the phases during the IP is essential, thus impregnation on the buckypaper support, first with the organic phase and then with the aqueous phase (denoted as inverse IP, iIP) leads to permeances (of up to 28.0 and 31.4 L m−2 h−1 bar−1 for water and methanol, respectively) and rejection values (>96%) that exceed those of the membranes prepared by reversing the impregnation order. Secondly, a double layer PA/zeolitic imidazolate framework (ZIF-8 or ZIF-93) was prepared on the buckypaper (bp). The design of this double layer led to superior membrane performance, in particular for the hydrophilic ZIF-93, as it changes the PA layer properties (increasing both hydrophilicity and surface roughness) providing higher permeances (up to 59.3 and 76.0 L m−2 h−1 bar−1 for water and methanol, respectively) and dye rejections (>98.5%) than the bare PA layer prepared by iIP. This attractive performance of the PA/ZIF-93/bp membrane has been corroborated with experiments in cross-flow nanofiltration and dead-end nanofiltration of aqueous salt solutions, long-term stability nanofiltration and the study the membrane separation performance after a chlorine treatment. The results reported here therefore show the enormous potential of these membrane architectures for a variety of selective separation processes. ; Grants PID2019-104009RB-I00 and PID2019-104272RB-C51 funded by MCIN/AEI/10.13039/501100011033 are gratefully acknowledged (Agencia Estatal de Investigación (AEI) and MCIN (Ministerio de Ciencia e Innovación), Spain). The Aragón Government is also gratefully acknowledged (Grupos reconocidos T43_20R, T03_20R and E25_20R). V. B.-S. thanks the Grant BES-2017-080209 funded by MCIN/AEI/10.13039/501100011033 and by "ESF Investing in your future". ; Peer reviewed