RESULTS IN ENGINEERING
Systematic covalent crosslinking of graphene oxide membranes using 1,3,5 triazine 2,4,6 triamine for enhanced structural intactness and improved nanofiltration performanceSystematic covalent crosslinking of graphene oxide membranes using 1,3,5 triazine 2,4,6 triamine for enhanced structural intactness and improved nanofiltration performance
KANDJOU, VEPIKA; ACEVEDO, BEATRIZ; MELENDI ESPINA, SONIA.
From its physicochemical characteristics, graphene oxide (GO) is a promising versatile next generation membrane material. Its unique characteristics like ultrafast permeation and hydrophilicity makes it a favourable separation membrane nanomaterial in water purification. However, a fundamental problem in the use of GO in nanofiltration is decreased performance overtime due to the pore size widening phenomenon. This paper explored the use of an amine group containing compound, 1,3,5 triazine, 2,4,6 triamine (melamine) to covalently interlink the GO nanosheets to counteract this swelling phenomenon. Prior to membrane fabrication, covalent interactions between GO and the crosslinker, melamine were successfully confirmed through thermogravimetric analysis (TGA), x-ray photoelectron spectroscopy (XPS), X-ray Diffraction (XRD) and Fourier Transform Infra-Red (FTIR) spectroscopy characterisations. Following these characterisations, crosslinked membranes were successfully fabricated and enhanced nanofiltration performance was confirmed. Resultantly, the surface morphology of the membranes was recorded via Scanning Electron Microscopy (SEM) characterisations while a lab-scale nanofiltration device was constructed for flux and rejection analysis. Evidently, performance improvement with covalent crosslinking was imminent as an up to a 100% rejection of methylene blue was achieved for the crosslinked membranes. Structural integrity of GO membranes has indeed been improved through crosslinking.
Link to source: https://www.sciencedirect.com/science/article/pii/S2590123023001639
2.2.2. Control and MLM crosslinked membrane fabrication
The membranes were fabricated with an automated rotary dip-coater (Nadetech Innovations, Navarra, Spain). The layer-by-layer fabrication time and the number of dips were set at 1 and 5 min and 1, 3 and 5 respectively with the assistance of an ND-R Rotatory Coater Software. They were then labelled accordingly to show the immersion time and assembly cycles, for instance crosslinked membranes fabricated under 1 min immersion time for 5 assembly cycles was duly labelled GO-MLM 1′5.