Effect And Mechanism Of Multi-functionalized Luffa-rattan Biochar For Remediation Of Uranium Contaminated Water

The treatment of radioactive waste liquid is the primary environmental problem in the nuclear fuel cycle.The radioactive waste liquid containing uranium produced from uranium mining and smelting has the toxicity of radioactivity and heavy metals.This type of pollution is a great threat to the local ecological environment.In particular,there are a large number of uranium tailings ponds in southern China.The official implementation of the Law of the People’s Republic of China on the Protection of the Yangtze River is bound to more strictly control the impact of uranium tailings ponds on the local water ecology.Biochar with cheap,green,and renewable raw materials,as adsorbents is a low-cost solution for the treatment of radioactive waste liquids containing uranium.According to the characteristics of rich crop resources in Jiangxi Province,this study prepared base biochar（LRBC）by hydrothermal method using agricultural waste luffa ratten as a carbon source.Functionalized biochar（F-LRBC）was prepared by the Hummer method.Then the F-LRBC was magnetized to obtain magnetic functionalized biochar（MF-LRBC）.The performance of F-LRBC and MF-LRBC for the treatment of uranium waste liquid was studied by static adsorption experiment and dynamic column experiment.XPS,SEM,BET,FT-IR,Zeta potentiometer were used to analyze the microstructure,surface chemical composition and pore structure of the materials,to explore the reaction mechanism of uranium adsorption by F-LRBC and MF-LRBC.The main research results are as follows:SEM and BET data show that the microstructure of F-LRBC and MF-LRBC is rough and porous,and the pore structure is mainly mesoporous.The specific surface area of F-LRBC is 3.754 m²/g,and that of MF-LRBC is 20.925 m²/g.The increase of specific surface area is mainly caused by the covering of Fe₃O₄ microspheres on the surface of biochar.FT-IR,XPS,and EDS showed that the surfaces of F-LRBC and MF-LRBC were rich in oxygen-containing functional groups,which could effectively absorb uranyl ions in solution.The static adsorption experiments show that the solution p H can significantly affect the uranium adsorption properties of F-LRBC and MF-LRBC,and the best p H is 6.0.The key factors affecting the adsorption properties of materials are the surface functional groups are protonated and the morphologies of uranyl ions when the solution p H is different.The adsorption behavior of uranium by F-LRBC and MF-LRBC conforms to the quasi-second-order kinetics model and Langmuir isotherm model,indicating that uranium adsorption is mainly by chemical adsorption,and the saturation adsorption capacity of uranium at the molecular layer is 434.78 mg/g and243.25 mg/g,respectively.The increase of reaction temperature is beneficial to the improvement of material adsorption performance.After thermodynamic model fitting,（?）G<0,（?）H>0,indicating that the uranium adsorption process of F-LRBC and MF-LRBC is spontaneous endothermic.The dynamic column experiments using F-LRBC and MF-LRBC as the reaction media show that the penetration point of the penetration curve decreases with the increase of Ca²⁺concentration and CO₃^2-concentration.The multi-stage distribution of the reaction medium can effectively improve the treatment effect.When the concentration of Ca²⁺and CO₃^2-is 2.0 mmol/L,the q₀ andτof F-LRBC are 253.50mg/g,167.22 mg/g,and 760.52 mins,501.67 mins,respectively.The q₀ andτof MF-LRBC are 172.08 mg/g,134.30 mg/g,and 516.24 mins,402.91 mins,respectively.It is indicated that F-LRBC and MF-LRBC as the reaction media of permeable reaction wall have a certain application prospect in the remediation of uranium-contaminated groundwater.