Research On Removal Of Uranium(?) Based On The Enhanced Electrocoagulation By Uranyl Ion Cooperative Chelation With Organic Ligands

With the vigorous promotion and development and application of nuclear energy,more and more uranium-containing waste water is discharged into the water environment,causing serious damage to the ecological environment and human health.The green,high-efficiency and resource-based treatment of uranium-containing wastewater is a problem that needs to be solved and a research hotspot.In this study,the low-concentration uranium-containing wastewater?5.0mg/L?was expensive to process and it was difficult to recycle resources.A new idea was proposed for the chelation of uranyl ions(UO₂²⁺)with organic ligands to enhance electrocoagulation and remove uranium from wastewater.That is,the selective chelation of uranyl ions and organic ligands allows the free-dispersed,highly active uranyl ions to be grafted and fixed,and then uranium-containing chelates are generated by electrocoagulation to remove uranium from the wastewater.The oxidized washing of the obtained flocs destroys the chelating chemical bonds between the organic ligands and uranyl ions,so as to realize the dissociation of uranium in the precipitated flocs,providing a theoretical and technical reference for solving the high-efficiency treatment and resource recovery of the uranium-containing wastewater.This paper explores and discusses the main influencing factors of electro-flocculation and organic ligands for enhanced deflocculation of uranium,and analyzes the dynamic characteristics of electro-flocculation and the addition of organic ligands to enhance electro-coagulation;Physical characterization and analysis of the flocculated flocs were performed to reveal the mechanism of enhanced flocculation and precipitation of FeO/hydroxide flocculating precursors and UO₂²⁺and UO₂²⁺-organic ligand chelates.H₂O₂and Na₂CO₃ were used to wash precipitated flocs,dissociate and enrich the U?VI?in the flocs,and realize the resource enrichment of radioactive U?VI?in wastewater.Mainly achieved the following conclusions and understanding:?1?The effects of different influencing factors on the effect of electrocoagulation and organic ligands on enhanced pucculation removal of uranium were studied.The effect of electrocoagulation on uranium removal was best under pH 6.0 and current density j=2.0mA/cm².Under the conditions of pH 6.0,current density 1.0 mA/cm²,Alizarin Red as organic ligand,molar ratio of organic ligand to uranyl ion 3:1,and initial uranium concentration 3.5mg/L,the uranium removal rate of the body-reinforced electrocoagulation is up to 99.35%,and the power utilization rate is higher.The addition of organic ligand chelating electro-flocculation technology is more suitable for the treatment wastewater of low-concentration uranium-containing.?2?The analysis of kinetics of removal uranium electrolytic flocculation and addition of organic ligands to enhance electro-flocculation show that the electro-coagulation process for uranium removal complies with the first-order kinetics model.The addition of organic ligands for chelation and enhanced electrocoagulation process is more consistent with the second-order kinetics model.?3?H₂O₂+Na₂CO₃ oxidation elution was used to increase the concentration of UO₂²⁺in the eluate,and the concentration of Al³⁺,Ca²⁺,Mg²⁺,and Fe³⁺was lower,indicating that the organic ligands were mainly used.Selective UO₂²⁺sequestration,Al³⁺,Ca²⁺,Mg²⁺,and Fe³⁺are basically not chelated and enriched,and the elution amount of uranium is proportional to the amount of precipitated floes.It shows that the addition of organic ligands for chelating and intensifying electrocoagulation to remove uranium precipitated flocs is easy to realize resource recovery and enrichment,and is suitable for the treatment wastewater of low-concentration uranium-containing.?4?SEM,XRD,XPS,and FTIR were used to characterize the electro-coagulation and the addition of organic ligands to enhance electro-coagulation and flocculation.It is revealed that the mechanism of electro-flocculation and uranium removal is mainly caused by uranyl ions being precipitated by electro-coagulation of precursors Fe?OH?₃ and Fe₂O₃,and uranyl ions and OH-precipitate directly.The mechanism of adding organic ligands for chelating and strengthening electro-flocculation to remove uranium is:both the electrocoagulation of precursors Fe?OH?₃,Fe₂O₃,and the trapping of uranyl ions?ie physical adsorption?,there are also uranyl ions and organic ligands in the active group chelating?ie,ion exchange?,and then by the precursor of Fe?OH?₃,Fe₂O₃ flocculation removed.