Crown ether intercalated graphene oxide membranes for highly efficient sieving of cesium with a large water permeability

The highly efficient sieving of Cs+ from natural brine resources has garnered considerable attention for the extraction of cesium raw materials. However, for the trade-off between ion rejection and water permeability, it remains challenging for graphene oxide (GO) membranes to improve efficient sieving of Cs+ with a large water permeance. Here, we have successfully addressed this challenge by fabricating a GO membrane that incorporates crown ether (CE) through π-π and CH-π interactions with GO sheets. This CE intercalation has resulted in a significantly enhanced Cs+ sieving capability from salt lake brines, concurrently improving water permeance. The unique Cs+ selective cavity structure of the CE has enabled the GO membrane to exhibit a Cs+ rejection rate of 94.4 % and a water permeance of 15.8 L m−2 h−1 bar−1 at a Cs+ concentration of 0.150 mmol/L (∼20 ppm). Compared to the pure GO membrane, these results represent an improvement of over 70 % in Cs+ rejection and more than 230 % in water permeance. Interestingly, we have also observed that this GO membrane exhibits a low Na+ system consisting of two components, the separation factor of Cs+/Na+ reaches up to 5.0, which is significant in monovalent ionic membrane separations. These significant discoveries provide a promising strategy for the highly efficient extraction and concentration detection of Cs+ from complex ion solutions.