Preparation And Properties Of Functionalized Graphene Oxide For Uranium Adsorption

The seawater contains about 4.5 billion tons of uranium.Extracting uranium from seawater is of strategic importance for the sustainable development of nuclear energy.Graphene oxide(GO)is widely used for adsorption uranium due to its excellent physical and chemical properties,such as large specific surface area,abundant modified organic functional groups,and special aromatic structures.However,the steric hindrance effect,the significant negative charge and the agglomeration caused by van der Waals force of GO surface,limit the adsorption capacity of GO.Meanwhile,GO will induce the insertion of two or three water molecules to make the GO layer spacing larger than the diameter of uranyl ion,which reduces the adsorption selectivity of GO.Therefore,it is still a challenge to design GO-based adsorbent materials for extracting uranium from seawater with high adsorption capacity and high selectivity.The GO-BSA composite was prepared by covalently crosslinking GO with bovine serum albumin(BSA)by using carbodiimide,which reduced GO agglomeration and improved the adsorption capacity of uranyl ions.Meanwhile,a series of physicochemical characterizations of GO-BSA were performed.The effects of pH,adsorption time and initial concentration on the adsorption performance of uranium were studied.The adsorption capacity of GO-BSA composite at pH=6 is 389 mg g-1.The adsorption kinetics was fitted the pseudo-second-order.Besides,the composites show good adsorption efficiency in simulated seawater,indicating that GO-BSA composites have good prospects for seawater uranium extraction.GO-DM-AO composites were prepared through post-decoration with amidoxime functionalized diaminomaleonitrile(DM-AO).The material provides more active sites for the adsorption of uranyl ions with high adsorption capacity and adsorption selectivity.Adsorption amount of uranyl ions on the as prepared GO-DM-AO reached at 915 mg g-1,which is increased by 206%increment compared with that of pristine GO at the same concentration.Excitingly,the excellent removal efficiency could still maintain even after 5 cycles of adsorption-desorption.A new type of GO based adsorbent GO-C16TAB-PA was successfully prepared by organic modification of GO with cetyltrimethylammonium bromide(C16TAB)and phytic acid(PA).The relationship between the PA and GO layer spacing was investigated.When the GO spacing is 3.88 A,the adsorption capacity of adsorbent can reach 923 mg g-1,and removal rate is 90%.The adsorption equilibrium time of GO-C16TAB-PA was shortened by 50%compared with that of pristine GO.In addition,the GO-C16TAB-PA adsorbent exhibited good recyclability with a six-adsorption-desorption cycle test.Finally,the GO-C16TAB-PA adsorbent exhibited good adsorption performance in simulated seawater.In order to acquire more void space of UiO-66 as active points for improving adsorption capacity,GO-COOH/UiO-66 composites were designed via coordination of the carboxyl groups of GO with zirconium ion of UiO-66.The GO-COOH/UiO-66 composites were characterized by transmission electron microscopy,X-ray diffraction and Fourier transform infrared spectroscopy.The adsorption properties of GO-COOH/UiO-66 composites were studied.The results show that adsorbent has high adsorption capacity and great removal rate.The adsorption mechanism of uranyl ions onto GO-COOH/UiO-66 composites was revealed by infrared spectroscopy,the change of pH before and after uranium adsorption and X-ray photoelectron spectroscopy.