Synthesis Of Layered Double Hydroxide And Oxide Modified Carbon Nanotubes Composites For The Application Of U(VI) Adsorption

With the development of nuclear power,the shortage of uranium resources and the harm of uranium wastewater have become increasingly prominent.Therefore,it is of great economic and social significance to investigate the economical and efficient method of separ.Layered double hydroxide?LDH?has attracted much attention,due to its excellent physicochemical property?such as thermo-stability,easily-exchanged intercalated layer anions and opened porous structures?.However,LDH materials also possess some drawback such as poor acid resistance and poor kind of oxygen-containing functional groups that harmful to their adsorption of radionuclides.Hence,this paper was aim to synthesize the composites that the carbon nanotubes was the skeleton materials.It has proposed to Ca/Al layered double hydroxide decorated carbon nanotube?Ca/Al-LDH@CNTs?,magnetic Fe/Zn layered double oxide decorated carbon nanotubes?M-Fe/Zn-LDO@CNTs?composites,Ca/Zn/Al layered double hydroxide decorated carbon nanotubes?Ca/Zn/Al-LDH@CNTs?and Ca/Zn/Al layered double oxide decorated carbon nanotubes?Ca/Zn/Al-LDO@CNTs?.Various characterization techniques?e.g.,SEM,TEM,element mapping,EDS,XRD,FT-IR and XPS?has been used to analyze the microstructure.The adsorption properties and mechanism between the adsorbents and the U?VI?has been investigated.Ca/Al layered double hydroxide decorated carbon nanotube?Ca/Al-LDH@CNTs?composites were fabricated by co-precipitation method and hydrothermal aged treatment.The adsorption results indicated that the adsorption of U?VI?on Ca/Al-LDH@CNTs was four times higher than that of U?VI?on bare CNTs.The kinetic investigations reflected the chemisorption of U?VI?on Ca/Al-LDH@CNTs through oxygen-containing functional groups.The adsorption isotherms demonstrated that the adsorption of U?VI?was well fitted by Langmuir model and the maximum adsorption capacity of U?VI?on Ca/Al-LDH@CNTs was 382.9 mg·g^-1 at 289.15 K.The thermodynamic parameters calculated from temperature-dependent isotherms suggested that U?VI?adsorption on Ca/Al-LDH@CNTs were endothermic and spontaneous process.The magnetic Fe/Zn layered double oxide decorated carbon nanotubes?M-Fe/Zn-LDO@CNTs?composites were synthesized via a hydrothermal method with further calcination treatment.The fabricated M-Fe/Zn-LDO@CNTs was characterized by XPS,FTIR,XRD,UV-Vis,SEM,TEM,and then applied for elimination of U?VI?under diversiform experimental conditions,such as p H,temperature,ionic strength,contact time and coexisting ions.The experimental results demonstrated that the U?VI?adsorption performance of M-Fe/Zn-LDO@CNTs was much higher than bare CNTs.The thermodynamic parameters revealed that U?VI?adsorption on M-Fe/Zn-LDO@CNTs was endothermic and spontaneous.More importantly,the adsorption performance of U?VI?on M-Fe/Zn-LDO@CNTs was still higher than⁸9%after five cycles,which confirmed that M-Fe/Zn-LDO@CNTs was an excellent material for efficient removal of lanthanides and actinides from environmental aqueous solutions in radionuclide'pollution remediation.A practical and simple hydrothermal and calcination method was used to synthesize Ca/Zn/Al-LDH@CNTs and Ca/Zn/Al-LDO@CNTs nanocomposites for U?VI?efficient removal.The U?VI?adsorption on Ca/Zn/Al-LDH@CNTs and Ca/Zn/Al-LDO@CNTs were investigated under various experimental conditions,and the results indicated that U?VI?uptake on were consumingly dependent on pH and the adsorption was mainly attributed to surface complexation and electrostatic interactions.The maximum adsorption capacity of U?VI?on Ca/Zn/Al-LDH@CNTs was calculated to be 340 mg·g^-1,T=298.15 K,which was higher than that of U?VI?on Ca/Zn/Al-LDO@CNTs(280mg·g^-1).In this paper the synthesis of LDH/CNTs nano-composites is expected to be applied to the separation and enrichment of actinide radionuclide,and provide a new method and technology for the radionuclide pollution treatment from environment.