Rapid and efficient separation of radioactive cesium ion/other radioactive ions by reduced graphene oxide membrane

Abstract

Separation of cesium ions from other radioactive ions is of great significance for recycling and utilization of radioactive sources, facilitating the management of highly radioactive liquid waste (HLW), as well as for environmental protection. We achieved a highly selective and efficient separation of binary mixtures of 137Cs/60Co, Cs+/Co2+, Cs+/Ni2+, and Cs+/Zn2+ using amino-hydrothermal reduced graphene oxide membranes. The separation factor for non-radioactive binary mixtures is up to 4290, with a water permeance of 50.8 L m−2 h−1 bar−1. The separation factor for radioactive 137Cs/60Co is 623, which is somewhat underestimated due to the detection limit of the high-purity germanium spectrometer. The rGO membranes has the high water permeance of 72.4 L m−2 h−1 bar−1, with a thickness of ∼300 nm. The rGO membrane achieved effective separation of cesium and cobalt ions over a wide range of cesium-to-cobalt ion concentration ratios, with the best results achieved at a concentration ratio of 100:1 for cesium and cobalt. In addition, the rGO membranes showed outstanding stability. The superior performance is attributed to the amino hydrothermal treatment, which reduced oxygen functional groups and directly inserted nitrogen atoms into the GO lattice, ultimately forming stable narrow nanochannels conducive to the size-sieving effect. The findings show that the rGO membranes have excellent separation performance due to their size-sieving effect, and this work has great potential for rapid and efficient treatment of radioactive liquid waste.