Study Of Optimization Experiment And Removal Mechanism Of Electrokinetic Remediation For Radioactive Uranium Contaminated Soil

The large amount of waste rock waste produced in the process of uranium mining and smelting,which usually piled up in the tailings pond.The uranium would be released into the soil under the action of weathering,acid rain and leaching.Due to its strong radioactivity,it will pose a certain threat to human survival.Therefore,carrying out uranium-contaminated soil restoration has important research significance.In this paper,uranium-contaminated soil was used as research object,and EK remediation technology is combined with saliency analysis,Visual MINETQ simulation software and material characterization methods to improve energy efficiency and removal efficiency of uranium and reduce secondary pollutants.The experiment was conducted to EK remediation of uranium-contaminated soil.Details as follows:?1?There factors?the voltage gradient,electrolyte type and electrolyte concentration?were selected for EK remediation.The thermal effect phenomenon and energy utilization efficiency in the EK remediation process are mainly investigated.The experimental results show that in EK remediation process,the phenomenon of thermal effect is ubiquitous,which led to different degrees of soil temperature rise.At the same time,the concept of energy utilization rate was introduced to evaluate the utilization rate of energy consumption in the EK remediation process.The results of the saliency analysis show that the voltage gradient has the greatest influence on the energy utilization rate,the electrolyte type is the second,and the electrolyte concentration is the smallest.However,in the EK remediation process,excessive electrolyte introduction will significantly increase the useless work?thermal effect and non-target ion transfer?and reduce the energy utilization efficiency.Therefore,the introduction of a suitable amount of electrolyte may make the energy distribution beneficial to improve the target metal removal.The direction of the rate shifts and improves engineering efficiency.?2?A new type of composite reagent?citric acid+ferric chloride,CA+FeCl₃?,was used in EK remediation of uranium-contaminated soil,and explored the concentration of different components on the soil.The effect of uranium removal efficiency,energy efficiency and leaching toxicity.The results showed that the optimal electrolyte combination method was 0.1mol/L CA+0.03mol/L FeCl₃.As a result,the removal efficiency of uranium was?61.55±0.41?%,and the energy utilization rate was?0.24±0.22?×10³,uranium.The leaching toxicity was 0.059 mg/L.Compared with inorganic acid acids and citric acid,the combination of citric acid and ferric chloride has higher removal efficiency,higher energy utilization rate and lower uranium leaching toxicity.?3?The acid washed zero-valent iron/activated carbon mixture was used as the permeable reactive barrier coupled with EK technology to remove uranium from contaminated soil.The effects of the type,quantity and location of PRBs media on the removal efficiency of uranium were studied,and the mechanism of Fe⁰/AC mixture removal of uranium was revealed by means of characterization.The experimental results show that the Fe⁰/AC mixture as the PRB medium has higher removal efficiency than the single Fe and activated carbon.At the same time,increasing the number of PRB and reducing the thickness of the PRB medium can promote the removal efficiency of the electrically repaired uranium-contaminated soil.The removal efficiency of the highest uranium is 80.58%.The mechanism of uranium removal by Fe⁰/AC mixture was revealed by means of SEM,EDS,FTIR and XPS,including electrostatic adsorption,surface complexation and coprecipitation of activated carbon,and the micro-cell formed between Fe⁰/AC could promote hexavalent.The progress of uranium to tetravalent uranium reduction reaction.