Preparation Of Magnetic Mesoporous TiO₂/Graphene Oxide Composites And Their Adsorption Properties Of U???

Uranium has chemical toxicity and radioactivity which can damage the function of the organism and the ecological environment.In order to protect the environment and human health,it is necessary to treat the uranium-containing wastewater.The adsorption method is widely used in the treatment of uranium-containing wastewater because of its advantages of high efficiency and low cost,simple synthesis and operation,selective adsorption and so on.In this study,magnetic mesoporous TiO₂?MTiO₂?was prepared by sol-gel method and hydrothermal synthesis method using tetrabutyl titanate?TBOT?as precursor and nano-ferric oxide?Fe₃O₄?.The magnetic mesoporous TiO₂/graphene oxide?MTiO₂/GO?composites were prepared by mixing and stirring with 3-propyltrimethoxysilane?APTMS?used as a cross-linking agent and GO suspension prepared by Hummers method.Then the adsorption properties of MTiO₂/GO on wastewater of U?VI?,Cd?II?unit system and U?VI?-Cd?II?binary system wastewater at a concentration of 10 mg/L were investigated.The adsorption results of MTiO₂/GO on U?VI?and Cd?II?unit systems show that the adsorption effect of MTiO₂/GO composites are better than that of MTiO₂ and GO alone;The maximum adsorption rates of U?VI?and Cd?II?are99.52%and 95.43%,respectively,under the optimal condition,the temperature is 303 K,the pH value is 6,the mass fraction of GO is 60.00wt%,the MTiO₂/GO dosage is 10.00 mg;both the quasi-secondary kinetic model and the Freundlich adsorption isotherm model can describe the adsorption process well.The desorption experiments show that the adsorption rate of U?VI?and Cd?II?is still more than 90.00%after 5 cycles of adsorption-desorption,indicating that MTiO₂/GO has a higher recycling performance.The adsorption results of MTiO₂/GO on the binary system of U?VI?-Cd?II?showe that the existence of U?VI?and Cd?II?mutually inhibit the adsorption capacity of MTiO₂/GO,which is due to the fact that,U?VI?and Cd?II?have the same active sites on the surface of MTiO₂/GO,and there is competition between them,but the inhibition of Cd?II?by U?VI?is stronger,which indicate that MTiO₂/GO has stronger selective adsorption ability to U?VI?;the quasi-secondary kinetic model and the Freundlich adsorption isotherm model can describe the adsorption process well.The results adsorption-desorption experiment show that the adsorption rate of U?VI?and Cd?II?by MTiO₂/GO is maintained at a high level after 5 adsorption-desorption,indicating that MTiO₂/GO has a higher recycling performance.X-ray diffractometer?XRD?,scanning electron microscope?SEM?,Fourier transform infrared spectrometer?FTIR?,etc.,was used to characterize and analyze the microscopic morphology,material properties and structural changes of the adsorbed samples.The results show that MTiO₂ is successfully loaded onto GO,and MTiO₂/GO composites with uniform size and narrow pore size distribution are prepared;GO improves the utilization ratio of sunlight by MTiO₂ and enhances the absorption intensity of MTiO₂ in the ultraviolet range.In the adsorption process of U?VI?or Cd?II?,the main functional groups of MTiO₂/GO composites are hydroxyl group,carbonyl group and epoxy group,etc.,which mainly occur complexation reaction,electrostatic attraction or ion exchange reaction.