Synthsis Of Phosphorylated Composite For U(?) Removal

Uranium is one of the key elements used in the nuclear power industry and a highly toxic contaminant.It will be harmful to both natural and human beings after being released to the environment.Because of the potential hazardous of uranium,it's of great importance to develop new materials and techniques to remove uranium from contaminated solutions and the environment.The phosphate and phosphonate ligands are usually engaged to extract uranyl from aqueous solution because it readily bond to uranyl in solution.In this thesis,a series of phosphorylated materials were synthesized as sorbent for uranium removal based on the affinity of phosphoryl group to uranyl.This work contains two parts as follow:1.By using “hydrothermal method” and “one-pot” synthesis,a phytic acid(PA)modified titanate nanotube(PA/TNTs)was prepared,and this composite was used as adsorbent for uranium uptake.The synthesized material was identified with Powder X-ray diffraction(PXRD),Fourier Transformation Infrared spectroscopy(FTIR),Zeta Potential,Thermogravimeric Analysis(TGA),and Transmission Electron Microscope(TEM),and results show that the morphology of TNTs maintains after modification.The distribution of phosphoryl group was unraveled by STEM.The results of batch experiments indicate that the PA/TNTs exhibit good sorption performance toward U(?)for possessing a satisfied maximum sorption capacity of 1.16×10-3 mol/g at p H = 5.0,T = 293 K,and the sorption equilibrium can be reached within 6 h.Furthermore,by combining the results of sorption/desorption with the characterizations of PXRD,FTIR,solid fluorescence,and EXAFS,we can conclude that the uranyl was sequestrated by PA/TNTs via the formation of inner-sphere complexation.Overall,the synthesized PA/TNTs composite could be utilized as a cost-effective material for the removal of U(?)from wastewater.2.According to the previous study about the synthesis and sorption performance of PA/TNTs composite.We have obtained some useful information.Here,graphene oxide,which has large specific surface area,abundant surface functional groups,and convenience to modification,was taken as a substrate.For the purpose of improving the efficiency and uniformity of phosphorylation,a novel Graphene Oxide-Chitosan(CS)composite(GO-CS-P)was synthesized by combining amidation and Arbuzov reaction via an oriented synthesis strategy.The as-prepared composite was applied for U(?)removal.Scanning Electron Microscope(SEM)and TEM images were recorded to analyze the morphology of the bare/modified materials.PXRD,FT-IR,Zeta Potential,and TGA results show that the ternary material was successfully prepared.From STEM image,it is obvious that the phosphorylation of the material is uniform and well-proportioned.The results of batch experiments show that the GO-CS-P composite exhibits excellent sorption performance toward U(?)for the sorption equilibrium can be reached within 15 min and the maximum sorption capacity was 779.44 mg/g at p H=5.0,T=293 K.The Qmax is one of the highest values among the current reported adsorbents.The GO-CS-P also exhibits excellent selectivity for capturing U(?)from a mixture containing multiple competing metal ions.Additional,mechanism of the interaction between uranyl and GO-CS-P was manifested by analyzing the results of desorption,PXRD,FT-IR,X-ray Photoelectron Spectroscopy(XPS),and X-ray Absorption Spectroscopy(XAS).Results indicate that the highly efficient immobilization of U(?)on GO-CS-P was predominantly controlled by inner-sphere surface complexation with a minor contribution of surface reduction.The experimental findings demonstrate the removal of U(?)by GO-CS-P with combined advantages of ultrafast removal kinetics,high sorption capacity,and great selectivity.These observations indicate that the GO-CS-P composite can be used as a potential adsorbent for the purification of uranium-bearing wastewater.In this work,two kinds of phosphoryl-containing composites(PA/TNTs and GO-CS-P)were successfully prepared and the synthesis procedures as well as the structural characteristics of these two materials were demonstrated from microscopic point of view.Influence of different factors to the sorption behavior of U(?)on these two composites was investigated scrupulously and circumspectly.The relationship between the sorption performance of the two composites in different aqueous systems and species of U(?)as well as surface properties of the two composites were comprehensively dissected and elaborated.It was found that the surface properties of the composites and the nature of the cations affect the selectivity in sorption to a great extent.In this,the interaction mechanisms between U(?)and the composites were studied from bulk material to molecular level,in which the inner relevancy of the structure and sorption performance of the materials was revealed.On account of the detailed results,the structure-activity relationship was established macroscopically and microscopically.All in all,this study not only offers two promising materials that can be used in the remediation of uranium-contaminated water but also provides theoretical and experimental basis for the subsequent design and synthesis of advanced adsorbents with high efficiency and high selectivity,which will benefit the future work on uranium sorption.