Electroactive nanofiltration membranes based on carbon nanostructures for enhanced desalination performance

Abstract

Recent advancements in materials science has paved the path for creating nanofiltration membranes that are both electrically conductive and suitable for desalination purposes. These smart membranes offer a powerful approach to regulate ion transport and fouling through surface potential variation. Herein, we report the development of an electrically responsive nanofiltration membrane through a novel process involving the physical entrapment of carbon nanostructures (CNS) within a regenerated cellulose network, followed by crosslinking with glutaraldehyde and casting. We investigated different crosslinking conditions to achieve optimal desalination results. Electron microscopy techniques such as, TEM and SEM, were utilized to confirm the successful incorporation of CNS within the cellulose network. Consequently, the resulting membrane exhibited remarkable electrical conductivity (6044 ± 6.404 S/m), which was exploited to improve membrane performance in desalination. Our results showed that applying an external voltage of −1 V increased the rejection rates of NaCl from 43.8 % to 54.6 %, and Na2SO4 from 75.6 % to 81.7 %, with insignificant effect on the permeate flux. This enhancement was attributed to the increased Donnan potential difference resulting from the polarization-induced charges generated on the membrane when a negative bias was applied. Moreover, the membrane demonstrated reversible ion transport modulation, excellent recyclability, and self-cleaning capabilities. Overall, our findings highlight the potential of these electroactive nanofiltration membranes for desalination and other ion separation applications.