Synthesis Of Mesoporous Materials By Nanoemulsion Method And Its Application To Extraction Of Uranium From Seawater

As an important low-carbon emission non-fossil energy,nuclear energy plays an important role in the global energy supply.Seawater uranium extraction technology can solve the problems of insufficient reserves on land,difficult mining,and uneven distribution,and is a very important separation technology.However,problems such as the low concentration of uranium in seawater,the competition of many ions,and the complex marine environment make it difficult to popularize on a large scale.Therefore,it is necessary to develop efficient and low-cost adsorbents.At present,most of the adsorbents are amidoxime-based materials,and their harsh polymerization conditions,low hydrophilicity,and low selectivity make the adsorption effect unable to be effectively improved.Inorganic mesoporous materials are a class of green adsorbents with high specific surface area,dispersed adsorption sites and simple preparation,which have been widely used in various sewage treatment and heavy metal recovery.In order to seek effective nanomaterials as adsorbents and enrich the system of adsorbents,this paper investigates the existing forms of uranium in seawater and land,and combines the mechanism of the current new adsorbents to prepare a new adsorbent with high adsorption capacity and high selectivity.Highly mesoporous inorganic materials.The main content is divided into the following two parts:1.Combined with the phenomenon that most of the uranium ores on land are phosphoric acid-uranium ores,the nano-emulsion method was used to prepare mesoporous calcium hydrogen phosphate nanowires with extremely low density.The effect of microemulsion on the morphology and phase was mainly studied.In the simulated uranium-doped seawater solution,the highest adsorption capacity was 3125mg-U/g,and the adsorption reached saturation within 30 minutes.In real seawater,a higher adsorption capacity of 13.5 mg-U/g was achieved.More importantly,it has good selectivity for transition metal ions,especially for V.The chelation of uranyl ions by P-O whose coordination structure is mainly phosphate was analyzed by EXAFS and XPS.Secondly,through DFT calculation,it was found that the adsorption energy per unit mass of hydrogen phosphate on uranyl ions was much lower than that of vanadyl ions.The reason for its high selectivity was confirmed.The preparation is simple,green and inexpensive,and has excellent adsorption performance.Therefore,the large-scale application of mesoporous calcium hydrogen phosphate nanowires in real seawater uranium extraction is very promising.2.Combined with the phenomenon that uranyl in the ocean is bound by carbonate,mesoporous vaterite calcium carbonate was prepared by microemulsion method.The effects of surfactants on morphology and phase were focused on.Among them,F127 can not only create pores,but also stabilize vaterite oligomers.When m Ca CO₃ is used in the extraction of uranium from seawater,its adsorption capacity is about twice that of commercial calcium carbonate.In the simulated seawater solution doped with uranium,the highest adsorption capacity was 852 mg-U/g.What’s more,put it in the dialysis bag,its adsorption performance is almost unaffected.In real seawater,a high adsorption capacity of 6.5 mg-U/g was achieved with good selectivity for transition metal ions,especially for V.The existence and adsorption coordination structure of uranyl were confirmed by XPS and IR.Mesoporous vaterite calcium carbonate is simple to prepare,green and cheap,and has good selectivity,which makes mesoporous vaterite calcium carbonate very promising for use in real seawater uranium extraction.