Highly efficient uranium adsorption by salicylaldoxime/polydopamine graphene oxide nanocomposites

Uranium is the main element for nuclear energy production and is one of the most hazardous radionuclides; its effective enrichment plays a key role in energy strategy and environmental safety. Oxime-functionalized nanostructures are the most promising candidates for uranium adsorption. However, current methods for their preparation mainly focus on multistep grafting and oximation processes, and the nanostructures usually show low efficiency. Here, we report a rapid one-step process to synthesize salicylaldoxime/polydopamine modified reduced graphene oxide (RGO-PDA/oxime) via the polymerization of dopamine (DA) and simultaneous deposition of oxime with an obviously decreased total synthesis time of 2 h. The obtained maximum uranium adsorption capacity of up to 1049 mg g(-1) was 3-16 times larger than those of the reported single PDA or oxime modified nanostructures. The RGO-PDA/oxime followed the pseudo-second-order kinetics model and Langmuir isotherm equation with much higher adsorption selectivity and recyclability. The outstanding sorption performance is attributed to the electrostatic repulsion between GO and salicylaldoxime and the effective combination between PDA and oxime molecules. Finally, given the adhesion capability of DA to diverse surfaces, this rapid one-step method was used to prepare five other oxime/PDA modified materials, which also showed improved uranium adsorption efficiency. These findings provide a way to obtain oxime-functionalized nanostructures with promising uranium adsorption efficiency.