Study On Solidification Treatment Of Uranium Mill Tailings By Zeolite Minerals And The Stability Of Solidified Body

In order to achieve the safe and effective t reatment and disposal of uranium mill tailings(UMT), taking montmorillonite as raw materials, the solidification of UMT by in-situ synthesis of sodalite was investigated. First of all, the mineral properties of UMT was studied, which include mineral compo sition, particle characteristics and acid leaching of UMT. In the second, the one-step hydrothermal synthesis of zeolite A and sodalite on montmorillonite was researched, and the influence of Na OH concentration, liquid-solid volume ratio, reaction temperature and time on the phase and morphology of the products were also discussed. Based on the above research, we make a study about the synthesis of Cs-sodalite by montmorillonite to immobilize radionuclides Cs, and study the effects of Cs concentration, Na OH concentration and reaction time on the crystal cell parameters and the inclusion rate of Cs. The leaching possibility of Cs from Cs-sodalite was analyzed by leaching experiment. Finally, the solidification of UMT by in-situ synthesis of sodalite was investigated, and the leaching behavior of the solidified body was analyzed.The results showed that the main phase of uranium tailings is quartz, gypsum and sodium feldspar. The uranium content in UMT is very low, only 30.4 mg/kg, and the leaching rate of UMT in acidic medium is large. The optimal conditions for preparation of sodalite from montmorillonite is Na OH concentration of 4 mol/L, liquid-solid volume ratio of 17.5, reaction time of 12 h and reaction temperature of 90 ℃. Sodalite was synthesized with high purity, fine crystallinity and uniform particle size distribution under the optimum conditions. At low temperature and alkalinity, montmorillonite can not be activated effectively, which is not conducive to the synthes is of sodalite, and improving the alkalinity and temperature was contributed to the synthesis of sodalite. Cs-sodalite was synthesized successfully by using montmorillonite as raw material after the adsorption of Cs, and it’s optimum synthesis conditions was the Cs concentration of 2g/L, Na OH concentration of 5mol/L and reaction time of 10 h. Under the optimum conditions, the leaching rate of Cs-sodalite was less than 0.36%, which implies that the consolidation effect of Cs was good. Using montmorillonite and UMT as raw material, the composite of 是 odalite and UMT was successfully prepared, and the best preparation conditions is Na OH concentration of 4 mol/L, reaction temperature of 105 ℃ and reaction time of 20 h. The leaching resistance of the composite is go od, and the 42 nd day of leaching rate is less than 5.0 × 10-8 cm/d, the cumulative leaching fraction is less than 3.08 x 10-6 cm. Both indexes of leaching is almost 2 or 3 orders of magnitude lower than the cement solidified, reached the national standard of uranium tailings disposal. This study provided a new method for the crystal lattice solidification of UMT, and it is of great significance for further study the treatment of UMT.