Preparation Of Manganese Oxide,titanium Oxide,and Their Composites And Study On Their U(Ⅵ)adsorption Properties

Nuclear energy is the most promising green and clean energy source of the future,which is usually obtained by fissioning ²³⁵U.However,uranium-containing wastewater resulting from the development of the nuclear industry poses a serious threat to human health and the ecological environment.In recent years,tremendous progress has been made in research on the treatment of uranium-containing effluents at home and abroad,and among various treatment methods,adsorption has attracted much attention because of its easy operability and adaptability under various conditions.Among the many adsorbents,metal oxides have high chemical activity and complexation capacity for U（VI）.Among them,manganese oxides and titanium oxides are materials with excellent adsorption performance and are widely used for the removal of uranium wastewater.However,they are easy to agglomerate during their preparation and difficult to obtain a fluffy structure,which seriously affects their adsorption performance and limits the application of manganese oxide and titanium oxide materials in nuclear wastewater treatment.In response to the problems of easy agglomeration of manganese oxide and titanium oxide,poor recycling regeneration ability and interference by ions,this thesis uses the freeze-drying-template calcination method to obtain high-performance manganese oxide materials and titanium oxide adsorbent materials.The details of the study are as follows:（1）To address the drawback of poor dispersion of manganese oxide,in this paper,ultra-low density manganese oxide aerogels were prepared by freeze-drying-template calcination method to obtain manganese oxide adsorbents with uniform distribution of pore structure,which solved the problem of easy agglomeration of manganese oxide.Three manganese oxide materials with different microstructures and crystalline states were prepared by calcining the Mn Cl₂-chitosan composite aerogels at different temperatures（500,600 and 700℃）in air for5 h.It was shown that the template material was completely removed after calcination at600℃,and no pore collapse and sintering were observed in the manganese oxide material.In the experiment using the manganese oxide material as U（VI）adsorbent,the maximum adsorption amount of Mn O-600 for U（VI）was as high as 635.4 mg/g,which was nearly three times that of other manganese oxide materials.These results indicate that the present work successfully used the freeze-drying-template calcination method to prepare Mn_xO_y materials with excellent performance.（2）High-performance titanium oxide adsorbent materials were prepared by the same method to address the problems of easy agglomeration and poor recycling capacity of titanium oxide.the removal behavior of Ti O₂ adsorbent materials for U（VI）was mainly controlled by electrostatic interaction and complexation.The isotherm and kinetic models are in accordance with the Langmuir model and quasi-second order model,respectively.Its maximum theoretical removal efficiency and adsorption capacity reached 97.1%and 638.0 mg/g,respectively.To explore the effect of coexisting ions on the adsorption behavior,the Ti O₂aerogel was not disturbed by most of the ions.The Ti O₂ aerogel prepared using this method has a strong adsorption capacity for U（VI）.In addition,this study not only improves the remediation ability of Ti O₂ materials for uranium-containing wastewater,but also increases their reusability.The study indicates that the freeze-drying-template calcination method provides a new idea for the preparation of metal oxide materials with high adsorption performance.（3）The two metal oxide materials,manganese oxide and titanium oxide,are still subject to high interference from some ions,Mn Cl₂?4H₂O was used as the manganese source,Ti Cl₃ as the titanium source and chitosan as the template material,and Mn_0.3Ti_0.7O_y,Mn_0.5Ti_0.5O_y and Mn_0.7Ti_0.3O_y were prepared by designing different manganese and titanium dosage ratios using freeze-drying-template calcination technique.The three Mn-Ti composites were prepared by designing different Mn-Ti dosage ratios.Its maximum adsorption capacity and adsorption rate reached 695.2 mg/g and 98.6%,respectively,which were superior to other titanium oxide and manganese oxide materials reported in the literature,and showed good selectivity in coexisting ions.Finally,the interaction mechanism of Mn_0.5Ti_0.5O_y with U（VI）is described.