Highly stable graphene-oxide-based membranes with superior permeability

Abstract

Increasing fresh water demand for drinking and agriculture is one of the grand challenges of our age. Graphene oxide (GO) membranes have shown a great potential for desalination and water purification. However, it is challenging to further improve the water permeability without sacrificing the separation efficiency, and the GO membranes are easily delaminated in aqueous solutions within few hours. Here, we report a class of reduced GO membranes with enlarged interlayer distance fabricated by using theanine amino acid and tannic acid as reducing agent and cross-linker. Such membranes show water permeance over 10,000 L m^-2 h^-1 bar^-1, which is 10-1000 times higher than those of previously reported GO-based membranes and commercial membranes, and good separation efficiency, e.g., rhodamine B and methylene blue rejection of ~100%. Moreover, they show no damage or delamination in water, acid, and basic solutions even after months.

Fig. 1

Structure characterization of GO-based membranes. a–c Photos of GO dispersion (a), rGO–TA dispersion (b), and rGO–TH dispersion (c). d, e Typical cross-sectional SEM images of GO (d) and rGO–TH membranes (e). f–h C 1 s XPS spectra of GO (f), rGO–TH (g), and rGO–TA (h) membranes. i XRD patterns of GO, rGO–TA, and rGO–TH membranes. Scale bars: (d) 1 μm; (e) 5 μm

Fig. 2

Hydrophilicity and stability of GO-based membranes. a–c Photos of a water droplet on GO (a), rGO–TA (b), and rGO–TH (c) membrane surface. d–l Stability in water (d–f), acidic solution (g–i), and basic solution (j–l). d, g, j GO membrane. e, h, k rGO–TA membrane. f, i, l rGO–TH membrane. The time staying in the aqueous solution is indicated in each photo

Fig. 3

Permeability and separation performance of GO-based membranes. a DI water permeance of GO, rGO–TH, and rGO–TA membrane at a transmembrane pressure of 1.0 bar. b–d Permeance and rejection of organic dyes (50 µM) of GO (b), rGO–TA (c), and rGO–TH (d) membranes at a transmembrane pressure of 1.0 bar. GO membrane, 100 nm thick; rGO–TA membrane, 150 nm thick; rGO–TH membrane, 60 nm thick. e Permeance comparison of rGO–TH and rGO–TA membranes with the GO-based membranes reported in the literature^–. Here, the permeance of rGO–TH and rGO–TA membranes is the maximum values that are obtained in the dye separation experiments

Fig. 4

Structure and performance of rGO–GT membranes. a rGO–GT dispersion. b C 1 s XPS spectra. c XRD pattern. d Photo of a water droplet on rGO–GT membrane surface. e–g Stability in water (e), acid solution (f), and basic solution (g). h Permeance and rejection of organic dyes (1000 ppm) through a ~500-nm-thick rGO–GT membrane at a transmembrane pressure of 1.0 bar