Impact of environmental conditions on the sorption behavior of radionuclide ~(63)Ni(II) onto hierarchically structured γ-MnO _2

摘要

A novel hierarchically structured γ-MnO _2 has been synthesized using a simple chemical reaction between MnSO _4 and KMnO _4 in aqueous solution without using any templates, surfactants, catalysts, calcination and hydrothermal processes. As an example of potential applications, hierarchically structured γ-MnO _2 was used as adsorbent in radionuclide 63Ni(II) treatment, and showed an excellent ability. The effects of pH, ionic strength, temperature, humic acid (HA) and fulvic acid (FA) on the sorption of radionuclide 63Ni(II) to hierarchically structured γ-MnO _2 have been investigated by using batch techniques. The results indicated that the sorption of 63Ni(II) on γ-MnO _2 is obviously dependent on pH values but independent of ionic strength. The presence of HA/FA strongly enhances the sorption of 63Ni(II) on γ-MnO _2 at low pH values, whereas reduces ~(63)Ni(II) sorption at high pH values. The sorption of 63Ni(II) on γ-MnO _2 is attributed to inner-sphere surface complexation rather than outer-sphere surface complexation or ion exchange. The thermodynamic parameters (ΔH ~0, ΔS ~0, ΔG ~0) are also calculated from the temperature dependent sorption isotherms, and the results suggest that the sorption of 63Ni(II) on γ-MnO _2 is a spontaneous and endothermic process.