Highly stable graphene-oxide-based membranes with superior permeability

Khalid Hussain Thebo,Hui-Ming Cheng,Long Chen,Qing Zhang,Xitang Qian,Wencai Ren

doi:10.1038/s41467-018-03919-0

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.

Highlights

Increasing fresh water demand for drinking and agriculture is one of the grand challenges of our age
It is important to note that TA and TH are rich with oxygen functional groups, which, respectively, have an O/C atomic ratio of 0.61 and 0.43, the O/C atomic ratio decreases from 0.44 for pristine Graphene oxide (GO) membrane to 0.40 for reduced GO (rGO)–TA membrane and 0.22 for rGO–TH membrane
The rGO–TH membrane shows typical C1s X-ray photoelectron spectroscopy (XPS) characteristic of rGO (Fig. 1g), with greatly reduced peak intensity related to the oxygen functional groups

Summary

Results

Synthesis and characterization of rGO–TA and rGO–TH membranes. GO sheets were synthesized by exfoliation of graphite oxide made by the modified Hummers method[29] using sonication. This confirms that the TA and TH molecules serve as spacer to provide a large interlayer distance to facilitate water transport and as molecular sieves to block the dyes. The rGO–TH (1:4) membranes show water permeance of 2370 ± 30 L m−2 h−1 bar−1 and EB rejection of 98 ± 1% These results suggest that the separation performance of the rGO–TA and rGO–TH membranes can be further improved by optimizing the thickness and the content of TA or TH of the membranes.

Discussion

Methods

AΔtP ð1Þ