| In recent years,the rapid development of nuclear energy has increased the demand for nuclear materials.China is also a depleted uranium country,with the proven uranium reserves ranking the 10th in the world,and the scale of ore deposits is mainly small and medium-sized(accounting for more than 60%of the total reserves).The security of uranium resources and the safety of nuclear power environment have become the key to the development of nuclear power.Based on the geological phenomenon of the symbiosis between pitchblende and pyrite,the kinetics of the dissolution of pitchblende by pyrite and hydrogen peroxide in acid leaching was studied in this paper.Firstly,the kinetics of the dissolution of pitch uranium by O2,H2O2 and pyrite in the air in different concentrations of sulfuric acid solution was studied.With the increase of the concentration of sulfuric acid solution,the dissolution rate of uranium dioxide increased.If hydrogen peroxide is used as the oxidant alone and the concentration of sulfuric acid is less than 3g/L,UO4 precipitation will be generated,resulting in incomplete dissolution of UO2.With the increase of H2O2 measurement,the conversion rate of UO2 toUO4 increased and the more UO4 precipitation was generated.When the concentration of sulfuric acid was greater than 5g/L,UO2 was completely dissolved.As the measurement of H2O2 increased,the dissolution rate of UO2 became faster.The calculation of the nucleation model showed that the whole dissolution process was mainly controlled by the surface chemical reaction.Add H2O2 increased the dissolution rate of UO2 by more than 116%.When pyrite was added with a mass of 0.3g to the reaction alone,uranium dioxide dissolved the most.At the same concentration of sulfuric acid,the dissolution rate of UO2 could be increased by more than 54.6%with the addition of a small amount of pyrite(0.05-0.30g).When pyrite was more than 0.7g,the coordination of Fe2+ and S22-inhibited the dissolution of uranium dioxide.The dissolution process was carried out step by step.The calculation of the shrinkage model showed that the dissolution process was firstly controlled by the surface chemical reaction,and then the dissolution of oxygen was controlled by the diffusion of the reaction between the sulfuric acid solution and UO2 and Fe2+,as well as the co-action of the chemical reaction between Fe3+ and UO2.Then,the effect of the concentration of sulfuric acid,hydrogen peroxide and pyrite on the dissolution kinetics of UO2 was studied.The study found that with the increase of the concentration of sulfuric acid from 0.5g/L to 10g/L,the dissolution rate of uranium dioxide increased by 85.7%.With the increase of hydrogen peroxide content from 0.1ml to 0.5ml,the dissolution rate of uranium dioxide increased by 31.6%.As the pyrite mass increased from 0.1g to 1.0g,the dissolution rate of uranium dioxide increased by 17.1%.The concentration of sulfuric acid has a great influence on the dissolution of UO2,followed by the amount of H2O2,and the quality of pyrite has the least influence on the dissolution of UO2.Finally,the kinetics of the oxidation and dissolution of UO2 under the action of sulfuric acid,hydrogen peroxide and pyrite was analyzed by means of the nucleation model.Results showed that under the action of sulfuric acid,hydrogen peroxide and pyrite dissolution of UO2 nuclear model conforms to the shrinkage rate equation[1-(1-x)1/3=kt],and mainly controlled by surface chemical reaction.Kinetic constant k relative to the concentration of sulfuric acid,the reaction of hydrogen peroxide concentration and dosage of pyrite series were 0.34,0.29,0.10,The kinetic equation is (?).It provides a theoretical basis for uranium mining. |
PDF Full Text Request