Preparation of manganese dioxide/hollow mesoporous silica spheres (MnO2/HMSS) composites for removal of Sr(Ⅱ) from aqueous solution

Strontium ion in radioactive wastewater causes serious harm to the biological and ecological environment, so the removal of strontium ion is of great significance. We have prepared an inorganic adsorption material (MnO 2 /HMSS) by impregnation method. The adsorbent can effectively remove Sr 2+ in radioactive wastewater. The synthetic materials were characterised by X-ray diffraction (XRD), Scanning electron microscope (SEM), X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and N 2 adsorption-desorption isotherms. The effects of the mass ratio of manganese dioxide and hollow mesoporous silica spheres, pH, initial concentration of Sr 2+ , adsorption time, competitive ion and other parameters on the adsorption properties were systematically investigated. The results showed that the 4:1Mn0 2 /HMSS composite had the highest adsorption capacity. The adsorption of Sr 2+ on MnO 2 /HMSS is highly dependent on pH and initial solubility. Furthermore, the adsorption equilibrium is reached at 120 min, with a maximum adsorption capacity of 138.70 mg/g. In addition, the composite still maintains a good adsorption capacity under a variety of competitive ions. The Langmuir and pseudo-second-order models can better fit the adsorption isotherm and kinetic data than the Freundlich and pseudo-first-order models, respectively. The new composite obtained in this work has the advantages of rapid adsorption, large adsorption capacity, strong selectivity and capable of large-scale preparation, which makes it expected to play an important role in the removal of strontium ions.