Mechanism Of Uranium Adsorption On Nano-Oxide Composites

As an important energy material,uranium plays an irreplaceable role in the application fields of material science and nuclear industry.However,with the increasing demand and usage for uranium in modern society,it will inevitably enter the ecosystem.The existence and migration of uranium in water environment has attracted wide attentions because it will cause serious health problems to aquatic organisms and human beings through the food chain.MgO and Fe3O4 nanomaterials have attracted wide interests of researchers due to their widely available,low prices,and excellent adsorption properties,which provides an economic and effective method for removing uranium from the polluted waters.In order to improve the application potential of MgO and Fe3O4 materials in the field of adsorption,two kinds of nano-oxide composites were designed and prepared in this paper.The morphology,spectroscopic properties,and specific surface area of nanomaterials were systematically characterized and described by advanced characterization techniques.They were applied to the removal of uranyl in water,and the adsorption mechanism was carefully analyzed.(1)Adsorbents with magnetic separation performance and uranium adsorption capability are expected to help reducing the adverse effects of nuclear pollution.In this study,polydopamine(PDA)encapsulated Fe3O4 nanoparticles(Fe3O4@PDA)were synthesized and applied to remove uranium in water.The results showed that a large number of nitrogen-containing groups from PDA existed as uranyl chelating sites,which played an important role in the enrichment of uranium.The adsorption isotherm fits the Freundlich model,and the whole process is spontaneous and endothermic.Combined with X-ray photoelectron spectroscopy(XPS)analysis,it was confirmed that the adsorption of uranyl on Fe3O4@PDA was related to the surface-NH-,-NH2,and C-O complexation.It was also proved that the adsorbent had broad application prospects in the remediation of uranium-containing wastewater.(2)In order to improve the stability of MgO material,MgO/biochar(MgO/C)material was synthesized by a simple method and applied to the removal of uranyl ions in water.The results in this study showed that the adsorption reaction was more in consistent with the pseudo-second-order kinetics,and the adsorption isotherm met the Langmuir model.Compared with the MgO materials prepared by other research methods,the MgO synthesized in this study showed good adsorption capacity within the pH range of 4-8,which has greatly increased the adsorption stability of the materials.By combined with XPS analysis,it was found that the hydroxyl group on the surface of the MgO/C adsorbent played an important role in the adsorption process.