Preparation Of Amidoxime Modified Graphene Oxide And Its Adsorption Properties Of Uranium

In recent years,the nuclear science and technology industry has developed rapidly.A large number of nuclear wastes were produced,which are seriously harmful to environment and human.In order to deal with uranium in nuclear waste water,some methods have been used to study,among which adsorption method is favored for the advantages of good treatment effect,low cost and simple and convenient operation.Adsorption material is an important link in adsorption method and plays a decisive role in the results.The preparation of excellent adsorption materials has become an important and attractive research content.In previous studies,the selectivity of the amidoxime group to uranium element has stood out among many groups,and the related amidoxime-based materials have the potential of application in adsorption treatment.Graphene oxide has also been concerned in uranium element adsorption treatment because of its large specific surface area and good hydrophilicity.In this paper,graphene oxide（GO）was prepared first,then modified by amine group,then modified by nitrile group,and then treated with hydroxylamine hydrochloride.Graphene oxide rich in amidoxime was prepared as uranium adsorption material.Among them,in the link of amine modification,ethylenediamine and dopamine were used to modify,and finally two kinds of materials with different content of imidoxime group were obtained,which were recorded as amidoxime modified graphene oxide 1,2（GO-E-AO,GO-D-AO）.And GO,GO-E-AO,GO-D-AO were characterized by FT IR、TG、XRD、XPS、SEM.The results showed that the nitrogen content of GO-E-AO was 6.21%,and that of GO-D-AO was 7.39%,the content of GO-D-AO amidoxime group is higher than that of GO-E-AO.Adsorption experiments were carried out,and ICP was used to determine the adsorption capacity.At 25℃,m=0.2 g/L;volume of uranium solution=50 m L,p H=7,Time=360 min,C₀=100 ppm,maximum adsorption capacity of GO-E-AO was 352 mg/g;and the maximum adsorption capacity of GO-D-AO to uranium was 483 mg/g.Ethylenediamine can only react with carboxyl groups on the edge of GO,and dopamine can form polydopamine layer on the surface of graphene oxide.Polydopamine layer has super adhesion and can be coated on the surface of graphene oxide with large specific surface area.Therefore the modification of GO by polydopamine may achieve more amine groups then that by ethylenediamine,resulting in the higher contents of nitrile groups and amidoxime groups.More amidoxime groups of GO-D-AO lead to higher adsorption capacity than GO-E-AO.Kinetic and thermodynamic study was carried out on the adsorption process of uranium elements by GO-E-AO,GO-D-AO.Adsorption process is in accordance with the quasi-second-order kinetic model and belongs to chemical adsorption.Adsorption process is consistent with Langmuir model and belongs to monolayer adsorption.As to rmodynamic studies,calculations show thatΔH°>0,it shows that the adsorption process is the process of absorbing heat;ΔG°<0,the adsorption reaction can be carried out spontaneously;ΔS°>0,it shows that the adsorption process is an entropy process.The confusion of the solid-liquid interface increases during the adsorption process..