Non-swelling oxidized graphene ribbon membrane for the effective separation of cesium and strontium from radioactive liquid waste

Abstract

The interlayer swelling effect of graphene oxide (GO) membranes seriously hinders their applications in the precise nanofiltration, especially sieving cesium and strontium from radioactive liquid waste. Herein, a non-swelling membrane was successfully prepared via vacuum-filtering oxidized graphene ribbons (OGR), one kind of GO analogs. The unchanged interlayer spacing in OGR membrane (OGRM) were proved to originate from the unique two-section structure of OGR building blocks. Specifically, the low-defect aromatic plane in the central axis region of OGR resulted in the strong π‒π interaction, which prevented the further intercalation of water molecules at the nanoribbon edges and locked the whole lamellar architecture, hence inhibiting the peripheral expansion of OGR. By virtue of fixed nanochannels of OGRM, an ideal separation of Cs+ and Sr2+ was realized in the multicomponent acidic waste (pH ∼2.3), and the separation factors relative to UO22+ were fCs/UO2 = 6319 and fSr/UO2 = 2705, respectively. Meanwhile, OGRM showed a fast water flux of 12.10 L m−2 h−1, 15% higher than that of graphene oxide membrane (GOM). In addition to the special interlayer nanochannels, an in-depth investigation revealed that oxygenated groups also played an important role in the ion selectivity of OGRM. This preparation strategy of the non-swelling membrane is crucial to overcome the inherent paradox between the optimal selectivity and low flux, and our findings are very useful to remediate radioactive pollution and ensure water security.