Adsorption of Uranium Ion by Polyacrylonitrile/Hummers Oxidized Lotus Seedpod Carbon Composite

The separation and recovery of uranium from natural water is of great significance to the exploitation of unconventional uranium resources. In our paper, a novel polyacrylonitrile(PAN)/Hummers oxidized lotus seedpod carbon composite was prepared, and adsorption of U(Ⅵ) ion from U(Ⅵ)-CO₃ solution under weakly alkaline condition was also studied. Batch adsorption experimental results show that at room temperature, pH=8.0, ρ(U(Ⅵ))=50 mg/L, c_T(CO₃)=2 mmol/L, the adsorption reaches equilibrium after 840 min, and the maximum adsorption capacity is about 51.92 mg/g. The increase of the pH values, calcium ion concentration, magnesium ion concentration and carbonate concentration inhibit the U(Ⅵ) adsorption. Thermodynamic results indicate that it is a spontaneous, endothermic chemical adsorption process. Characterization results show that the composite displays good structure stability during U(Ⅵ) adsorption process, meanwhile, the phenolic —OH and —COOH(C=O) are the main adsorption sites on the composite surfaces. In the presence of calcium/magnesium ions, the order of adsorption affinity of U(Ⅵ) on the composite material is as follows: Mg-U(Ⅵ)-CO₃ system＞Ca-U(Ⅵ)-CO₃ system. The results can provide the new materials for the separation and extraction of uranium from natural uranium-containing water.