Mutual effects of U(VI) and Eu(III) immobilization on interpenetrating 3-dimensional MnO₂/graphene oxide composites

Radioactive contamination poses grievous latent threat to biology together with ecological balance. It is of great significance to eliminate radionuclides from nuclear waste solution. Herein, interpenetrating 3-dimensional (3D) MnO₂/GO composites (MGs) were rationally constructed by integrating α-crystal manganese dioxide (MnO₂) nanowire with graphene oxide (GO) via a simple ultra-sonication process. Preliminary experiments showed that the MG composite with mass ratio of 1:2 (M₁G₂) was the optimal material with superior adsorption capacities for U(VI) (271.7 mg/g) and Eu(III) (83.5 mg/g) at pH ~5.0 (298 K), as compared with commercial GO and individual MnO₂. Furthermore, M₁G₂ had high selectivity for U(VI) and Eu(III), which could remove >80% of target ions in the presence of NO₃^-, Cl^-, CO₃^2-, HCO₃^-, Mg²⁺, K⁺ or Na⁺ ions. It exhibited excellent stability under a wide range of pH 3-10 and great resistance to high ionic strength. More importantly, kinetic studies exhibited that M₁G₂ could efficiently capture target ions within ultra-short kinetic equilibrium time (<1 min). The interaction mechanism was clearly visualized by analyzing characterization data, showing that oxy-gen-containing functional groups took a major part for the binding of target ions. The excellent characteristics including the simple, fast and large-scale synthesis and the efficient performance endowed M₁G₂ with potential to remedy radioactive pollution in actual wastewater.