Adsorption Of U(?) On Graphene Oxide/Chitosan Modified By Amidoxime And Triethylenetetramine

The development and application of nuclear energy will produce a large number of uranium containing wastewater with chemical toxicity and low radioactivity,which will pose a potential threat to the ecological environment and human body.In order to protect environmental safety and human health,it is necessary to treat uranium containing wastewater.Adsorption method has been widely used in the treatment of uranium bearing wastewater because of its advantages of small secondary pollution,high removal efficiency and easy recovery.The key of adsorption method is to develop efficient and stable adsorbent.Among many composite adsorbents,graphene oxide/chitosan?GO/CS?is an excellent adsorbent.In order to further improve the adsorption performance of GO/CS for uranium,the amidoxime and triethylenetetramine are modified on this basis,and the composite materials of polyamidoxime/graphene oxide/chitosan?PAO/GO/CS?and triethylenetetramine/graphene oxide/chitosan?T/GO/CS?are synthesized.The adsorption properties of the materials to uranium under different environmental conditions are also investigated.They are as follows:1.In this study,GO/CS is synthesized by cross-linking method on the basis of GO.And new PAO/GO/CS composite is prepared by in-situ polymerization and reduction method finally.PAO/GO/CS is characterized by means of XRD,FTIR,XPS,TGA and SEM.Through the adsorption experiment of U?VI?,the effects of initial pH value,reaction time,initial concentration,temperature and coexisting ions for U?VI?removal on PAO/GO/CS are studied.At the same time,the adsorption behavior and mechanism of U?VI?on PAO/GO/CS are analyzed by fitting adsorption data and XPS method.FTIR and XPS show that the amidoxime group is successfully introduced into PAO/GO/CS;SEM shows that the surface morphology of PAO/GO/CS become rougher and shaggier,and display hierarchically where irregular and tiny protuberance coated.XRD shows that the amorphous degree of the material is higher;XPS and TGA analysis show that the amidoxime group is about 5%of the quality of PAO/GO/CS.The results of U?VI?adsorption experiments show that,with the pH value of 6,the temperature of 303 K,initial concentration of U?VI?10 mg/L,the PAO/GO/CS dosage of 10 mg and reaction time 90 min,the maximum removal efficiency of U?VI?by PAO/GO/CS is up to 99%.The quasi second-order kinetic model and Freundlich model can well fit the adsorption process,meaning that the surface of PAO/GO/CS is inhomogeneous where diffirent adsorption sites coated and U?VI?adsorbed to PAO/GO/CS mainly via chemical adsorption.The parameter analysis of adsorption thermodynamic equation shows that the adsorption process of U?VI?by PAO/GO/CS is spontaneous and endothermic.The results of XPS analysis before and after adsorption show that the carboxyl and amidoxime groups of PAO/GO/CS has complexation ability to U?VI?.The results of the interference experiments with common anion and anion show that CO₃^2-and SO₄^2-have a great influence on the adsorption of U?VI?,which reduce the adsorption capacity by about27%and 26%,respectively;K⁺in cation has a great influence on the adsorption of U?VI?,which reduces the adsorption capacity by about20%.The experiments of coexisting heavy metal ions show that the adsorption order of PAO/GO/CS to heavy metal ions is U>Cu?Mn?Cd?Zn,which proves that PAO/GO/CS has certain adsorption selectivity to U?VI?.The adsorption-desorption experiment shows that the adsorption rate of PAO/GO/CS to U?VI?remained 88%after5 cycles,which indicates that PAO/GO/CS composite has good recycling performance.2.T/GO/CS composite is prepared by solution blending and cross-linking method on the basis of GO.The composition of T/GO/CS are analyzed by FTIR and XPS.The effects of the dosage of T/GO/CS,the initial pH value,the reaction time and the initial concentration of U?VI?on the adsorption of U?VI?by T/GO/CS are investigated.The adsorption process is analyzed by isotherm model.The results of FTIR and XPS showed that T/GO/CS composite is successfully prepared.When the temperature is 303 K,pH is 6,adsorption time is 90 min,the dosage of T/GO/CS is 15 mg,and the concentration of U?VI?is 10 mg/L,the adsorption rate of T/GO/CS to U?VI?is up to 98%.The adsorption process accords with Langmuir isotherm adsorption model meaning that the maximum adsorption capacity of T/GO/CS for U?VI?is 214 mg/g.