Adsorption Characteristics And Mechanism Experimental Study Of Uranium (?) By Graphene Oxide Composites

A large amount of uranium containing wastewater was inevitably produced in the nuclear fuel cycle activities and mine tailings, imposing long-term threat to the environment and human beings. Therefore, how to eliminate uranium ions from contaminated wasterwater has drawn more and more people's attention. Adsorption technique has been widely used to treat uranium pollution because it is easy to operate, economical and has no pollution to the environment.Few-layered graphene oxide nanosheets were firstly synthesized from graphite by the Hummers method. The chitosan/graphene oxide composite(CS/GO) was prepared by the reaction in solution and the magnetism graphene oxide/?-cyclodextrin composite(MGO/CD) was prepared by the in-situ coprecipitation reaction in alkaline solution, respectively. The effects of p H value, adsorbent dosage, contact time, temperature and initial concentration of U(?) were investigated by static adsorption experiment.The experimental results of U(?) adsorption on CS/GO show that the highest adsorption capacity is obtained at p H 5 and c0(U)=10mg/L, with 40 wt% GO incorporated. The adsorption reached equilibrium within 5h. The maximum adsorption capacity for U(?) at 30? was evaluated to be 227.3mg/g. Kinetics data and adsorption isotherm were better fitted by pseudo-second-order kinetic model and by Langmuir isotherm model, respectively. Thermodynamic study reveals that adsorption of U(?) on CS/GO is spontaneous and endothermic. SEM images show that the surface form of CS/GO changed after adsorbing U(?). FTIR spectra demonstrates that hydroxyl and amine groups are the main binding sites of U(?) in CS/GO. Desorption experiments indicate that the adsorbent has a good property for repeated use.The experimental results of U(?) adsorption on MGO/CD show that the highest adsorption capacity is obtained at p H 6. The adsorption equilibrium time is 5h. The maximum adsorption capacity for U(?) was evaluated to be 322.6mg/g at 30?. The kinetics and equilibrium adsorption were well-described by pseudo-second-order kinetics and the Langmuir isotherm model, respectively. Thermodynamic study reveals that adsorption of U(?) by MGO/CD is spontaneous and endothermic. SEM show that MGO/CD has a rough surface and an uneven porous structure. It is confirmed by FTIR that hydroxyl group, carbonyl group and epoxide group are the main binding sites of U(?) in MGO/CD. Desorption experiments indicate that MGO/CD is a stable and reusable adsorbent.