Study On The Adsorption Of Uranium (?) By A Novel Polyoxometalate-Based Inorganic-Organic Hybrid Materials

With the deepening of the industrialization process,fossil fuels represented by coal and oil struggling to support people's pursuit of higher and better production and lifestyle,thus new energy sources such as wind energy,light energy,nuclear energy and other clean and efficient energy sources are the most promising future energy sources for mankind.Among them,nuclear energy has become one of the key research and development projects in various countries due to its high energy density,no CO₂ emissions,and easy storage.However,the leakage of uranium-containing radioactive waste slag generated during the nuclear fuel cycle will pose a serious threat to human and environmental safety.Therefore,it is of great significance to develop a class of economical and efficient new materials for low-concentration radioactive waste water,waste slag,and to measure the separation and enrichment of uranium in seawater.Polyoxometalates?POMs?,a class of metal-oxygen cluster multinuclear complexes formed by the linkage of a pro-transition metal?Mo,W,etc.?having a d⁰ electron configuration to an oxygen atom.POMs materials have a variety of changes,adjustable topologies,and excellent redox,acid and alkali properties are favored by researchers in many fields.POMs can be used as a pure inorganic multidentate ligand to construct new functional materials with different dimensions and different compositions.Investigations have shown that the use of POMs-based functionalized materials as a new solid adsorbent for the treatment of radionuclide-uranium has rarely been reported.Therefore,using the oxygen-rich and high electronegativity of the surface of POMs to provide a large number of active sites for uranyl ions,different POMs-based inorganic-organic hybrid materials were designed and synthesized,and their concentrations as solid adsorbents were studied.Separation and enrichment of uranium???.It not only expands the application fields of POMs,but also provides a new idea and new method for the capture and recovery of uranium.This is of great value for the study of the safe and sustainable use of nuclear energy.Based on this,this paper intends to adopt the method of hydrothermal synthesis,using[P₄Mo₆]as the secondary building unit,replacing different transition metals?Zn,Mn,Cd?as the linkers,and screening the nitrogen-containing organic ligands with different functional groups.Three novel POMs-based inorganic-organic hybrid materials?Mn-POM:one-dimensional chain structure,Zn-POM:two-dimensional layered structure and Cd-POM:three-dimensional skeleton structure?were successfully synthesized by adjusting the reaction conditions such as temperature.The crystal structure,thermo-chemical stability of these three materials,and the ability of the new solid adsorbent to capture uranium???in aqueous solution were studied in depth.The structure,purity and physicochemical properties of the materials before and after adsorption of uranium???and the adsorption mechanism were tested by a series of characterization methods.The effects of Mn-POM,Zn-POM and Cd-POM adsorbents on the adsorption performance of uranium???were studied by static adsorption conditions.The results showed that the optimum pH for uranium adsorption of the three materials are 4.0,5.0,and 5.0,respectively,and reached the adsorption equilibrium after 20 min,90min,and 210 min,respectively.Study on the uranium adsorption mechanism of the material was found to be affected by the chemical interaction between the Mn-POM and Cd-POM in the uranium adsorption process.The fitting curve is more in line with the quasi-secondary kinetic model and Langmuir.Isothermal adsorption model,which indicates that the adsorption mechanism of the two POMs-based materials is the chemical adsorption process of the monolayer;The Zn-POM uranium adsorption process conforms to the quasi-secondary kinetic model and is accompanied by quasi-first-order adsorption behavior,ie,chemical adsorption and physical adsorption coexist.At the optimum pH and equilibrium time,the maximum saturated adsorption capacities of the three adsorbents were 357.14 mg/g?Mn-POM?,632.90 mg/g?Cd-POM?and 781.25 mg/g?Zn-POM?,its adsorption capacity far exceeds some organic-inorganic hybrid materials?such as MOF,COF?.In addition,the experiment and study on the elution of POMs materials also proves the recyclability and stability of the adsorbents.Therefore,POMs-based inorganic-organic hybrid materials can be used as an ideal uranium adsorbent due to their excellent properties.Used for the removal and recovery of uranium???in radioactive wastewater.