Preparation Of Hydrotalcite-like Functional Composites And Enrichment Of Radioactive Element Uranium In Solution

Hydrotalcite has a unique layered structure,which structure is composed of a layer plate and an anion pillar between layers.It can made Different anion intercalation materials by changing the interlayer anions.At the same time,changing the metal cation composition and ratio of the laminate can also synthesis some specific hydrotalcite-like materials.some hydrotalcite-like compounds was Calcined at high temperature and was destroied its structure,which can obtain its composite oxide?spinel?.In this research,a common hydrotalcite was synthesized by hydrothermal synthesis method,and then anion pillars were replaced with thiol functional groups to obtain an adsorbent that efficiently adsorbs uranium ions in aqueous solution.In the second experiment,a metal element in the transition metal region was used as a material to synthesize a hydrotalcite-like compound and was calcined at a certain temperature to prepare a composite oxide.The product is used as a catalyst to catalytically reduce uranium ions in the wastewater.The hexavalent uranium ions in the solution was reduced to precipitated tetravalent uranium ions,so as to achieving the purpose of treating the uranium ions in the wastewater.This topic explores the application of hydrotalcite and its composite oxides in the environment.Hydrotalcite and its composite oxides are used to treat uranium ions in wastewater.This thesis includes the following aspects:1.The basic explanations of hydrotalcites,hydrotalcite-like compounds and their composite oxides were given,their preparation methods were briefly described,their structural characteristics were explained,and their uses were roughly summarized.Finally,The research content of this topic is put forward.2.Hydrotalcite was synthesized using urea as precipitant by hydrothermal method.And next the middle carbonate ion was removed by calcination,and then new organic functional groups were grafted to prepare thiol functionalized hydrotalcite.The samples were characterized by SEM,XRD,EDS,FT-IR and other characterization methods.3.The thiol-modified hydrotalcite was used as an adsorbent to adsorb uranium ions in an aqueous solution.The effects of contact time,dose of3-TMSPT,pH,temperature,initial uranium?VI?concentration,interfering ions and reusability were examined.At the end of the experiment,the adsorption mechanism is explained by some theoretical models.The batch adsorption experiments of Mg/Al-LDO-SH for UO₂²⁺was optimized at pH=3.0,equilibrium time 150 min,temperature 30?and initial UO₂²⁺concentration 30 mg/L with 1545.32 mg/g of adsorption capacity and99.06%of removal efficiency.The kinetic studies indicate that the adsorption process accords with pseudo second-order dynamic model and is primarily based on the Chemical adsorption process.Equilibrium experiments fit well with the Freundlich adsorption isotherm and show that the adsorption of UO₂²⁺by Mg/Al-LDO-SH is a multilayer adsorption process.4.The experiment utilizes the characteristics that the composition and ratio of the lamellar framework of hydrotalcite can be changed.Cobalt and Manganese elements in the transition metal zone are used as raw materials.Part of the divalent Manganese ions were oxidized to trivalent Manganese ions with an appropriate amount of strong oxidant,while the unstable trivalent Manganese ions are fixed with a complexing solution.Then the hydrotalcite is synthesized by hydrothermal method.Finally,it was calcined at a certain temperature to destroy its structure and to generate a composite oxide?spinel?.The prepared product also has two valence states of Mn element in one system:one is a common divalent Mn²⁺ion,and the other is a special unstable trivalent Mn³⁺ion.These two ions have ability at the same time.The morphology and crystal characteristics of the material were proved by SEM,XRD,XPS and other means.5.Spinel was used as a catalyst and thiourea was used as a reducing,which agent to co-process uranium ions in wastewater.The valence S element in thiourea provides electrons to the entire reaction system which reduces the valence state of uranium?VI?ions in the solution and reduce the hexavalent uranium ions(UO₂²⁺)in the solution to precipitated uranium ions?UO₂?.The effects of contact time,pH,temperature,initial uranium?VI?concentration were examined.Experimental data shows that batch catalytic experiments in an autoclave has a good catalytic reduction effect as temperature 100?,pH=6.0,time 20 h,catalyst dosage 3 mg,thiourea 500 mg,initial uranium?VI?concentration 50 mg/L and volume400 mL.The maximum catalytic reduction capacity reached 6500 mg/g and The maximum catalytic efficiency reached 98%,respectively.