Synthesis Of Permanganite-type Manganese Oxides And Study On Their Cs~+ Adsorption Properties

Cesium exists in trace in seawater,salt lake brine and geothermal water.In addition,137Cs from nuclear accidents and nuclear tests rapidly migrates to the groundwater.Therefore,the extraction of Cs+from solution is very important for cesium resource utilization and nuclear waste disposal.Due to the presence of Mn3+in the structure,which makes the skeleton negatively charged,manganese dioxide is called manganese oxide ion/molecular sieve.Meanwhile,due to the redox reaction between Mn3+ and Mn4+ in the structure,manganese dioxide is widely used as a material for supercapacitors.Todorokite(3×3)manganese dioxide can be used as an inorganic ion sieve for Cs+ adsorption.However,the instability of manganese oxide greatly limits application of the materials.Therefore,The main content of this paper is to prepare todorokite with high stability and use it for Cs+ adsorption in aqueous solution.The main research contents are as follows:1.Preparation of stable todorokite(Mg-Tod and Ni-Tod).Todorokite was synthesized by hydrothermal method.The optimization of temperature,metal ion doping,precursor crystallinity and other factors was discussed.The Mg-Tod and Ni-Tod was obtained at 160? by using the precursor of birnessite aged at 80?.The products have the advantages of high crystallinity and long-term stability in high concentration of acid.The Tod was characterized by XRD,FESEM,TG and XPS.2.The adsorption performance of Cs+ by Mg-Tod and Ni-Tod.H+can effectively remove the template Mg2+ and Ni2+in todorokite so that the materials can be used as the adsorbent in this work.Isothermal adsorption was carried out in 0.1 mol/L CsOH solution at room temperature.The Cs+ adsorption capacity of H-Mg-Tod and H-Ni-Tod was about 2.0 mmol/g.Taking the advantage of manganese dioxide as the ion storage material in the capacitor,H-Mg-Tod and H-Ni-Tod were used as electrodes for the adsorption of Cs+ under electrochemical process.As the concentration of Cs+ in the solution increases,the Cs+ adsorption capacity of the materials increases.With the increasing of pH,the Cs+ adsorption capacity also increases.Moreover,Ni-Tod shows a high selectivity for Cs+ in the mixed solution of different cations.The adsorption capacity of H-Mg-Tod and H-Ni-Tod for Cs+ reached 6.0 mmol/g and 11.5 mmol/g in neutral electrolyte solution,respectively.Therefore,todorokite type manganese dioxide as cesium ion adsorbents prepared in this paper has high stability and adsorption capacity in a wide pH range.It is expected to be used in separation and enrichment of low-concentration cesium ions in salt lake brine.