Graphene (rGO) hydrogel: A promising material for facile removal of uranium from aqueous solution

In the present study, graphene (rGO) hydrogel was fabricated by reducing graphene oxide (GO) with ascorbic acid to remove U(VI) from aqueous solution. The resulting rGO hydrogel shows a 3D porous network structure and good mechanical stability. The effect of contact time, pH, and initial U(VI) concentration on U(VI) adsorption, as well as the reusability of the material were estimated with batch experiments. The results illustrate that U(VI) adsorption on rGO hydrogel agreed well with pseudo-second order kinetic model, indicating a chemical adsorption. According to correlation coefficients, Freundlich model is the most suitable isothermal model to describe the U(VI) adsorption process of rGO hydrogel, with a maximum adsorption capacity of 134.23 mg/g (pH 4.0). The solution pH posed significant influence on U(VI) adsorption: the adsorption amount rises sharply from pH 2.0 to 4.6, reaches a plateau at 4.6–6.5, and then declines slightly at pH levels above 6.5. The rGO hydrogel shows good reusability, with maintaining 94.76% adsorption ability after ten adsorption/desorption cycles, demonstrating that rGO hydrogel is a promising adsorbent for U(VI) removal from aqueous solution, providing a new insight for the developing of U(VI) adsorbents.