Study On Preparation And Adsorption Properties For U(Ⅵ) Of N-based Core-Shell Materials

Uranium is a very dangerous pollutant to the environment.Most of the uranium in the environment is produced by activities such as uranium mining and grinding,nuclear energy production,coal mining,phosphate mining,and fertilizer production and application.Uranium enters the human food chain as a conta minant and can be removed or deposited in the target organs through the filtration of the kidneys after entering the human body.However,most uranium accumulates and is fixed and deposited in the bones,which is obviously toxic due to the long half-life of the organism.Therefore,the rapid removal and extraction of uranium from the environment is an urgent global issue,not only for human health and ecological reasons,but also for the sustainable development of nuclear energy.There are many methods to remove and extract uranium in water environment,among which the adsorption method has the advantages of economy,environmental protection and high efficiency.Due to its unique structural characteristics,core-shell structure materials have been used in the adsorption of radioactive uranium in wastewater in recent years,showing great application potential.A variety of core-shell nanocomposites were prepared by chemical in-situ polymerization and hydrothermal synthesis of Arsenazo Ⅲ,polyethylenimine and polyaniline containing nitrogen-containing functional groups,which are expected to be new functional adsorption materials for uranium adsorption.Objective:By comparing the adsorption performance of unmodified and nitrogen-modified adsorbents for radionuclide uranium,this paper discusses whether the introduction of nitrogen group can improve the adsorption capacity and efficiency of the new functional adsorbents.Static batch adsorption method was used to study the adsorption capacity and performance of functional adsorption materials modified by for nitrogen for uranyl ions,and the optimal adsorption conditions were determined.The adsorption kinetics of nitrogen-based functional adsorption materials for uranyl ions was studied.Langmuir and Freundlich isothermal adsorption models were used to fit the adsorption data.The elemental composition,functional groups and structure of the modified adsorption materials were characterized.This study provides a theoretical basis for the preparation of core-shell nanocomposites with high efficiency in removing uranyl ions.Methods:Using Arsenazo Ⅲ,polyethylenimine and polyaniline containing nitrogen functional groups,a variety of core-shell structure nanocomposite adsorption materials were prepared by chemical in-situ polymerization and hydrothermal synthesis,which were used to adsorb uranyl ions in uranium containing wastewater;the adsorption behavior of nitrogen-based functional adsorption materials for uranyl ions was studied by micro uranium analyzer;transmission and scanning electron microscopy were used to determine the adsorption mechanism.The microstructure and morphology of the adsorbent were observed by microscope;the element composition,atomic structure and chemical bond of the adsorbent were analyzed by XPS;the pore size and specific surface area of the adsorbent before and after modification were analyzed by BET;the possible functional groups of the adsorbent were analyzed by FT-IR;the crystallinity and structure of the adsorbent were analyzed by XRD;the magnetic properties of the adsorbent were analyzed by VSM.Results:1.GO/Arsenazo Ⅲ composites were successfully prepared by attaching Arsenazo Ⅲ to GO flakes and effectively binding the nitrogen-containing functional groups to the free hydroxyl groups on GO.The optimum pH of the material for uranyl ion adsorption is 5,and the maximum adsorption capacity is 200 mg/g.At the same time,temperature also affects the adsorption of uranyl ions by GO/Arsenazo Ⅲ,and the adsorption kinetics conforms to the quasi-second-order kinetic model.In addition,the adsorption of UO22+ by GO/Arsenazo Ⅲ conforms to Langmuir isothermal adsorption model.2.Impregnation method is used to make Arsenazo Ⅲ embedded into the channel of mesoporous silica SBA-15,and then coated with a layer of TiO₂.The Arsenazo Ⅲ@SBA-15@TiO₂ composite adsorption material was successfully synthesized.The optimal adsorption time for uranyl ions is 40 min,the optimum pH is 4.5,and the maximum adsorption capacity is 277.8 mg/g.The adsorption equilibrium is in accordance with Langmuir isothermal model.The kinetic data under the optimum conditions shows that the adsorption follows a quasi-second order kinetic model.The adsorption-desorption cycle experiment shows that the composite adsorption material can be reused.3.Nitrogen-based functionalized CuFe₂O₄ magnetic nanoparticle adsorption material（CuFe₂O₄/PANI）was successfully prepared by chemical in-situ polymerization and modification of CuFe₂O₄ nanoparticles by polyaniline（PANI）.When pH = 4,CuFe₂O₄/PANI adsorption material has a better adsorption effect on U（Ⅵ）in aqueous solution,and the maximum adsorption capacity is 322.6 mg/g.The adsorption performance of CuFe₂O₄/PANI is higher than that of CuFe₂O₄ nanoparticles.The adsorption process conforms to the pseudo-second-order kinetic equation and Langmuir isothermal adsorption model.CuFe₂O₄/PANI shows good stability and repeated regeneration,and the adsorption capacity of CuFe₂O₄/PANI remains above 170 mg/g after five cycles.4.CuFe₂O₄ @ SiO₂/PEI magnetic nanocomposites were successfully synthesized by coprecipitation of CuFe₂O₄ nanoparticles and polyethylenimine containing nitrogen groups.CuFe₂O₄ @ SiO₂/PEI shows good magnetism and stability.The maximum adsorption capacity of uranyl ion is 238.1 mg/g.The adsorption process accords with pseudo second order kinetic equation and Langmuir isothermal adsorption model.The results of recycling experiments show that the CuFe₂O₄ @SiO₂/PEI adsorption material can be reused.Conclusions:1.The GO flakes modified by Arsenazo Ⅲ contain a large number of nitrogen groups which can have strong complexation with uranyl ions.The maximum adsorption capacity of GO/Arsenazo Ⅲ for uranyl ions is up to 200 mg/g,which is higher than that of GO.2.A functionalized Arsenazo Ⅲ @ SBA-15 @ TiO₂ composite adsorption material with high specific surface area and high U（Ⅵ）adsorption capacity was successfully synthesized by impregnation method.It is a highly effective adsorption material for U（Ⅵ）removal from wastewater.Under the condition of pH = 4.5,the maximum adsorption capacity is 277.8 mg/g,which has good adsorption performance.It is a promising,efficient and reusable adsorption material for removing uranyl ions from wastewater.3.CuFe₂O₄/PANI composite adsorption material was synthesized by a nitrogen-based functionalization of CuFe₂O₄ nanoparticles by chemical in-situ polymerization.The adsorption performance of uranyl ions was improved.When pH= 4,CuFe₂O₄/PANI adsorption material has a good adsorption effect on U（Ⅵ）in aqueous solution and has a good reproducibility and stability.It is expected to become a uranyl ion adsorption material with a promising application prospect and no secondary pollution.4.Magnetic CuFe₂O₄ nanoparticles was functionalized with nitrogen groups by means of post-synthesis modification.The synthesized CuFe₂O₄ @ SiO₂/PEI magnetic nanocomposite was used to adsorb uranyl ions in aqueous solution,which improved the adsorption performance of uranyl ions.The adsorption material has good regeneration performance and can be used as a potential adsorption material to remove uranium from wastewater.