Self-healing properties of GO nanofiltration membranes based on dialdehyde cellulose nanocrystals and ethylenediamine facilitate efficient separation of dyes

Abstract

Graphene oxide (GO) membranes can purify wastewater due to their unique two-dimensional channels, but they are susceptible to mechanical damage during use, which reduces membrane performance. In this paper, EGO nanosheets were prepared by grafting ethylenediamine (EDA) small molecules onto GO at high temperatures and introducing aldehyde groups on the molecular chain of double aldehyde cellulose nanocrystals (DACNC), which reacted with reactive amino groups on the surface of the EGO nanosheets via a Schiff base reaction to create interlayer nanochannels in the composite membrane. The best performing EGO-DACNC24 composite membranes were prepared by adding different aldehyde substitution degrees and different amounts of DACNC to mediate the crosslinked interlayer nanochannels and network structure of the composite membranes. The water flux is more than 10 times that of pure GO membrane, and the rejection rate of dye molecules larger than 400 Da is always more than 99%. Excellent separation results are achieved after 120 h of operation due to the structural stability of the membrane resulting from chemical cross-linking. Damaged in practical applications, small amounts of added DACNC can achieve self-healing through the synergistic effect of dynamic Schiff base and hydrogen bonding interactions.