Preparation Of Polypyrrole/Graphite Phase Carbon Nitride Composite And Its Adsorption Properties For Uranium(Ⅵ)

A large amount of uranium-containing wastewater generated during uranium mining and uranium production and application will cause radioactive uranium pollution to the environment such as water and soil,posing a potential threat to human living environment and ecological environment.Adsorption method is widely used in the treatment of uranium-containing wastewater due to its simple process,high efficiency and low cost.The adsorbent is the core of the adsorption method.Graphite phase carbon nitride（g-C₃N₄）has rich functional groups.Polypyrrole（PPy）contains a large number of amino groups,but both g-C₃N₄ and PPy are prone to agglomeration.The number of active sites Less,limiting the practical application of the two.Therefore,this project uses graphite-phase carbon nitride（g-C₃N₄）as a substrate,and prepares a polypyrrole/graphite-phase carbon nitride（PPy/g-C₃N₄）composite by in-situ polymerization,and studies its effect on U（Ⅵ）.Adsorption performance and adsorption mechanism,the main research results are as follows:（1）Using melamine as raw material,graphite phase carbon nitride（g-C₃N₄）was prepared by heat treatment,and then compounded with polypyrrole（PPy）by in-situ polymerization to prepare polypyrrole/graphite carbon nitride（PPy/g-C₃N₄）composite material.The specific surface area of PPy/g-C₃N₄ composites is 26.2%higher than that of g-C₃N₄,the pore volume is reduced by 4.3%,and the pore diameter is reduced by 34.3%;（2）The PPy/g-C₃N₄ composite has good adsorption properties for U（Ⅵ）.At pH=5,the reaction temperature is 303K,the initial concentration of U（Ⅵ）is5mg/L,and the dosage of PPy/g-C₃N₄ is 200mg/L,the maximum adsorption rate of U（Ⅵ）for PPy/g-C₃N₄ was 93.22%,which was 37.26%higher than that of single g-C₃N₄ for U（Ⅵ）.The adsorption reaction reached the adsorption equilibrium within 20 minutes.The theoretical maximum adsorption capacity of303K is 185.19 mg/g.pH has the greatest influence on the adsorption of U（Ⅵ）by PPy/g-C₃N₄,and the influence of temperature and coexisting ions on U（Ⅵ）adsorption is small.In addition,the composite material has good reusability.After5 adsorption/desorption cycle tests,the adsorption rate of PPy/g-C₃N₄ for U（Ⅵ）is still as high as 85.17%.（3）The adsorption of U（Ⅵ）by PPy/g-C₃N₄ satisfies a quasi-second-order kinetic model,indicating that the adsorption of U（Ⅵ）by PPy/g-C₃N₄ is mainly chemical adsorption;the Freundlich model is more in line with the PPy/g-C₃N₄pair The adsorption process of U（Ⅵ）indicates that the adsorption is multilayer adsorption;analysis of thermodynamic parameters reveals that the adsorption process is a spontaneous endothermic process;XPS and FTIR analysis results show that PPy/g-C₃N₄ removal mechanism is that the carbon-containing,nitrogen-containing groups and oxygen-containing groups on the surface react with U（Ⅵ）.