Research On The Process Of Nitrate-hexavalent Uranium Composite Contaminated Groundwater Based On Copper-based Cathodic Eletroretrovifonment Treatment

In the context of"carbon peaking-carbon neutrality",the development of clean energy is crucial to my country’s economic and social development.Nuclear energy has the characteristics of no greenhouse gas emissions and low carbon footprint in the whole life cycle,and is an important clean energy.With the increasing demand for nuclear energy,the demand for uranium,which is the fuel for nuclear power plants,is also increasing.How to efficiently treat the uranium-containing wastewater generated in the process of uranium mining has become an important issue.In-situ leaching with nitric acid is one of the most commonly employed uranium mining methods nowadays,but the acid reflux wastewater produced by after in-situ leaching contains high concentrations of hexavalent uranium and nitrate,and it is difficult to remove these two pollutants simultaneously by conventional methods.The electrochemical reduction method has the characteristics of high efficiency,simple operation,and no secondary pollutants,which helps it garnered the attention from wastewater treatment areas.In this project,copper foam is selected as the base material,and Ag is loaded on the copper foam skeleton by chemical impregnation modification,and the Cu-Ag bimetallic composite electrode material is prepared.The reduction and removal effect and electrochemical reduction mechanism of Cu-Ag bimetallic composite electrode materials of nitrate and hexavalent uranium were studied by experimentally.The main findings obtained are as follows:（1）Through BET,SEM,XRD and other characterizations,it is found that elemental Ag with crystal structure grows on the surface of the copper foam supported by Ag,which proves that elemental Ag is successfully supported on the foamed copper substrate through chemical impregnation reaction.The ability of the Ag-loaded Cu-Ag bimetallic composite electrode material to reduce nitrate and hexavalent uranium is improved.（2）The optimal ratio of Cu-Ag bimetallic composite electrode material is Cu:Ag（mass ratio）=9:1.Compared with the original foamed copper electrode material,the Cu_0.9Ag_0.1bimetallic composite electrode has a significant increase in the electrochemical reduction and adsorption of U（VI）and nitrate,respectively,and the removal effect of nitrate and U（VI）is greatly improved.,the Cu_0.9Ag_0.1electrode has a removal rate of 97.4%for nitrate and 74.5%for U（Ⅵ）within 12 h.And the characterization by SEM and XRD proves that the electrode skeleton structure of the reacted Cu_0.9Ag_0.1copper-silver bimetallic composite electrode material is well preserved,and the 1000-cycle CV cyclic voltammetry test experiment can prove that the electrode material has good performance.（3）According to the LSV electrochemical test curve,it can be seen that when the Cu_0.9Ag_0.1bimetallic composite electrode is used as the cathode and the applied potential is-0.75 V and-1.2 V,the adsorption and reduction reaction of NO₃^--N and NO₂^--N occurred sequentially.The adsorption-reduction reaction of U（VI）occurs when the applied potential is-1.0 V,and the reduction of nitrogen-containing products by nitrate is closely related to the cathode reduction potential.When the cathode reaction potential was optimized at-0.8 V～1.4 V through the Cu_0.9Ag_0.1bimetallic composite electrode,it was found that when the cathode reaction potential was-1.4 V,the simulated uranium pollution with the coexistence of nitrate and hexavalent uranium ions wastewater,with the best removal efficiencies of 99.1%and93.6%within 24 h,respectively.