U(Ⅵ) Ions Adsorption With Functionalized Mesoporous Silicas From Aqueous Solutions

With the rapid development of the nuclear power industry, especially after last year’s Fukushima nuclear plant crisis, the demands for dealing with the troublesome nuclear contamination and the diffusive high concentrated radioactive waste water are more and more increasing. The versatile materials that can remove the radionuclides and remediate the environment are thus anticipated. Herein, a series of organic functionalized mesoporous silicas, phosphonate functionalized MCM-41(NP10), dihydroimidazole functionalized SBA-15(DIMS) and amino functionalized SBA-15(APSS) were synthesized by co-condensation and grafting method, and were used to separate uranium (U) from aqueous solutions. The synthesized functionalized mesoporous silica materials were characterized by XRD, NMR, SEM, and N2adsorption/desorption isotherm experiment. The synthesized materials were observed to possess highly ordered mesoporous structure with large surface area and well-defined pore size. The sorption of U(Ⅵ) ions by three materials were investigated under different conditions of pH, contact time, initial U(Ⅵ) concentration, ionic strength and solid-liquid ratio. The desorption and selective experiments were also studied. The preliminary sorption results show that the sorption is ultrafast and the equilibrium time is less than30min for all the three materials. The maximum sorption capacity for U (Ⅵ) sorption by APSS is even as high as409mg/g at pH=5.3±0.1, by NP10and DIMS were303mg/g and395mg/g at pH=7respectively. More importantly, it was found that all the three materials can selectively adsorbed U (Ⅵ) from the aqueous solution which containing a range of competing metal ions. In addition, the sorption of U(Ⅵ) is strongly dependent on pH by all the three materials and independent of solid-liquid ratios (m/V). For example,100mg of APSS material can almost completely remove the U(Ⅵ) ions from4.0L of the extremely diluted solution with U(Ⅵ) concentration as low as4.2ppb. Finally, a complete desorption (>99%) of U(Ⅵ) from the three materials can be achieved using0.05mol/L and more concentrated HNO3solution, the preconcentration factor can reach350. This work highlights the vast opportunities of organic functionalized mesoporous silicas applied in separation of uranium from waste water and enrichment of uranium from seawater.