| Uranium is one of the most important radioactive elements on Earth and the most common nuclear fuel.Uranium pollution is a prevalent issue,with various sources contributing to its prevalence.These include the functioning of nuclear power plants,the extraction and handling of uranium ore,accidents at nuclear facilities,nuclear weapons testing,and natural geological conditions in specific regions.The radioactive toxicity and chemical toxicity of uranium will cause serious harm to the ecological environment and human health.Mercury is a highly toxic heavy metal element.Longterm drinking or contact with mercury-contaminated water will cause serious damage to multiple organs and systems in human body.Mercury pollution in water environment is an urgent problem for human beings to solve.As an efficient,selective,simple,reproducible and low-cost water treatment method,adsorption has been widely used in the removal of uranium and mercury from water.Core-shell structural materials have unique structures and properties that other single structural materials do not have,such as high specific surface,versatility,controllability,directional self-assembly and other characteristics,and have been widely used in the fields of energy,biomedicine and photocatalysis.At the same time,there are a lot of studies on the preparation of various types of core-shell structural materials based on different methods for the removal of uranium and mercury in water,showing excellent adsorption properties.Objective:Through the preparation of core-shell structure materials with arsenazo Ⅲ and silicon dioxide,a new core-shell structure adsorption material for uranium adsorption in water was prepared by using the strong complex property of arsenazo Ⅲ and uranium to overcome the limitation that arsenazo Ⅲ is soluble in water.By introducing sulfhydryl groups on the surface of dendritic mesoporous silica in different methods,the adsorption properties of mercury in water were compared between composites and raw materials.The optimum pH values of uranium and mercury adsorption by coreshell materials and functionalized dendritic mesoporous silica materials were determined by batch adsorption experiments under static state.Additionally,the adsorption kinetics of the aforementioned materials were examined,and the data was fitted using the Langmuir and Freundlich isothermal adsorption models.To explore more efficient adsorbent materials for uranium and mercury removal from water.Methods:The utilization of transmission electron microscopy(TEM)enabled the observation of the microstructure and morphology of the core-shell materials.Meanwhile,XPS was employed for the analysis of the element composition and its relative content.X-ray diffraction(XRD)was also used to observe the lattices of the core-shell structures.Fourier-transform infrared spectroscopy(FT-IR)was used to identify the functional groups in the materials.Additionally,the materials nitrogen adsorption-desorption curves were analyzed using the BET method to determine their specific surface area,mean pore diameter,and pore volume.The thermal stability of core-shell structural materials was evaluated by thermogravimetric curve(TGA).The adsorption data were obtained by means of microuranium tester and ICP-OES method.Results:1.SiO2 shell was prepared by hard template method,and then the impregnation method was used to fill the SiO2 shell with arsenazo Ⅲ.Finally,the PZS(A polymer formed by the condensation of 4,4-dihydroxy-diphenyl sulfone with Phosphonitrilic chloride trimer)polymer-coated SiO2 shell was used to prevent spillover of arsenazoⅢ,and the arsenazo Ⅲ cored shell structural material was successfully prepared for the adsorption of uranium(Ⅵ)in water.The optimal adsorption pH of uranium with arsenazo Ⅲ core-shell structure material is 4.The maximum adsorption capacity was determined to be 205.76 mg/g,and the analysis of adsorption data suggests that the adsorption process was chemical in nature,as evidenced by the suitability of the quasisecond-order adsorption kinetic model.Additionally,the Langmuir isothermal adsorption model was found to be a suitable representation of the adsorption phenomenon.2.Dendritic mesoporous silica(DMSN)was prepared from urea and surfactant(CTAB),and the functionalized DMSN composite(TGA@DMSN)was successfully prepared from thioglycolic acid(TGA).The optimum adsorption pH for mercury(Ⅱ)in water was 8,the maximum adsorption capacity of the material was found to be 257.07 mg/g,which was significantly greater than that of DMSN.Equilibrium for adsorption was achieved within 20 minutes.The kinetics of adsorption were best described by the quasi-second-order model,while the isothermal adsorption behavior was in agreement with the Langmuir model.3.Cysteine(CYS)functionalized dendritic mesoporous silica(DMSN)composites(CYS@DMSN)were successfully prepared by introducing activated carboxyl group and the adsorption efficiency was studied.It takes about 20 min for CYS@DMSN to achieve equilibrium adsorption of mercury(Ⅱ)in water.The optimal pH of CYS@DMSN reaction is 5,and the maximum adsorption capacity is 204.49 mg/g.Chemisorption was observed during the adsorption process,and the kinetics of adsorption were described well by the quasi-second order model.Even after undergoing five adsorption cycles,the material still displayed a high adsorption capacity of 110 mg/g,indicating excellent reusability.Conclusion:1.A core-shell structure material with good adsorption performance has been prepared by hard template method and impregnation method,which can be used for uranium(Ⅵ)removal in water,and can reach adsorption equilibrium in about 10 min.The adsorption capacity can reach 205.76 mg/g when pH is 4,and has good thermal stability.2.Thioglycolic acid(TGA)functionalized DMSN composite(TGA@DMSN)was prepared by heating reflux method.The material is a good adsorption material for mercury(Ⅱ)removal from water.The maximum adsorption capacity can reach 257.07 mg/g at pH 8.Compared with DMSN,the adsorption efficiency of mercury(Ⅱ)in water is greatly improved.3.Cysteine(CYS)functionalized dendritic mesoporous silica(DMSN)composites were synthesized by the introduction of activated carboxyl group(CYS@DMSN).The maximum adsorption capacity can reach 204.49 mg/g when pH is 5,and has good reuse,and can be used as an efficient adsorption material for mercury(Ⅱ)removal in water. |
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