Study On The Preparation Of MgO And ZnO Multilevel Structure And The Adsorption Properties

The environmental problems caused by fossil fuels have profoundly affected the human health and tangible economy.Meanwhile,along with the crisis of fossil fuels supply,it’s urgent to modify the energy source structure.Nuclear fission energy,as the most mature new energy of commercial application,is an effective means to deal with the problem.However,uranium is radioactive with strong biological toxicity,which poses a very real threat to human beings and other organisms.At the same time,wastewater containing a large amount of uranium discharged into the environment was produced in the process of uranium mining and nuclear fuel processing.Besides,with the rapid development of nuclear power,it is required to explore new nuclear fuel sources from the ocean.Therefore,it has been a research hotspot to look for efficient adsorbents to solve the problem during the process of uranium separation and purification in the field of environment and energy.Firstly,the effect of the volume of ethylene glycol（EG）on the adsorption property of MgO was studied and it was shown that the optimum addition of EG was 10 mL.Then MgO was obtained by the improved atmosphere evaporation furnace,and the micro morphology of MgO was characterized by SEM,TEM and N₂ adsorption isotherms.In addition,the adsorption performance of MgO from simulated seawater was explored with the high adsorption rate up to 95～100%and the maximum capacity reached 1.09 mg/g（25 ℃,141μg/L）.Finally,the adsorption mechanism of MgO binding with UO₂²⁺ was exploited by XRD and XPS.In order to make up for the poor stability of MgO,selectivity and the poor effect of continuous adsorption in solution,ZnO was prepared as a substitute by solvent evaporation self-assembly method.By investigating the effect of the amount of glucose（G）on the morphology of ZnO,the best addition of G in raw material was obtained,and the multilevel structure was proved by SEM,TEM and N₂ adsorption isotherms.It was displayed that the as-prepared ZnO with multistage structure shown good adsorption performance with the large capacity of 1004 mg/g（pH = 4.0,25 ℃,500 mg/L）.The adsorption process at room temperature followed with the Freundlich isotherm（R2 = 0.979）and the pseudo-second-order kinetics model（R2 = 0.978/100 mg/L,R2 = 0.998/400 mg/L）.Then,the adsorption mechanism toward U0₂²⁺ was investigated with the assistance of XRD and XPS.Desorpted by NaHCO₃,the best desorption agent（0.01 mol/L）,the removal rate of uranium can still reach 92%after five adsorption-desorption cycles,indicating the excellent selectivity of ZnO for uranyl ions.To further improve the stability of ZnO in the adsorption process（mass loss of single adsorption process was up to 10%）,magnesium nitrate,aluminum nitrate,ferric nitrate and tetrabutyl titanate were added to the raw materials,and three kinds of oxides Zn-Al-O,Zn-Fe-O and Zn-Ti-O were prepared and their crystal phase were characterized by XRD.The adsorption capacity,stability and selectivity of the above were comprehensively investigated.It was shown that the adsorption performance of Zn-Al-O was the best adsorbent and whose mass loss rate decreased to about 5%in the single adsorption process and 0.01 mol/LNa₂CO₃ solution was the best desorption agent and desorption rate reached 99%.