Effective and sustainable Cs⁺ remediation via exchangeable sodium-ion sites in graphene oxide fibers

A monovalent sodium-functionalized graphene oxide fiber (Na-GO) structure was synthesized via facile and simple liquid coagulation of a graphene oxide solution. Supported by the stable GO framework, the readily accessible sodium site of this alkali-metal-carbon heterostructure allows effective removal of Cs⁺ in aqueous medium with a rapid equilibrium time (∼30 min) and a large adsorption capacity (220 mg g^-1). Na-GO possesses physical and chemical integrity in a broad pH range (4-10), and the adsorption behavior is influenced by the hydration radius of the targeting cation, charge effect, π-M⁺ interaction, and pH-dependent GO hydrophilicity. In utilizing the chemical potential effect of Na-GO, a simple regeneration process with NaOH solution selectively releases captured Cs⁺ and replenishes functional sodium sites within the Na-GO structure, providing a rechargeable Cs⁺ remediation functionality. This study demonstrates the successful adaptation of the alkali-metal-induced reversible ion-exchange principle for a versatile GO fiber structure.