Vertically aligned polyamidoxime/graphene oxide hybrid sheets' membrane for ultrafast and selective extraction of uranium from seawater

With the continuous research and development of amidoxime (AO)-based adsorbents, industrialization production of uranium from seawater gradually becomes a reality. However, the currently available AO-based adsorbents still suffer from low adsorption rate and poor selectivity. Herein, vertically aligned polyamioxime-graphene oxide (VA-PG) sheet membrane is fabricated by directional freeze casting. The run-through microchannels contribute to the free diffusion of uranyl ions (UO${}_2$${}^{2+}$), leading to the fast adsorption kinetics. Furthermore, partially reduced graphene oxide allows high photothermal conversion efficiency and rapid in-plane heat transfer, resulting in the fast temperature rise under simulated sunlight irradiation. Because of the endothermic behavior of UO${}_2$${}^{2+}$, light-irradiated VA-PG can simultaneously satisfy the requirements of high adsorption capacity (13.63 mg-U g-Ads${}^{-1}$), high adsorption rate (0.43 mg g${}^{-1}$ day${}^{-1}$), and excellent selectivity toward U(VI) over V(V) (U/V = 1.24) in natural seawater, indicating the right direction for a breakthrough in the field of uranium extraction from seawater. (© 2021 Wiley‐VCH GmbH)