Study On The Mechanism Of U(?)on The Surface Of Pyrite And Hydroxyapatite

In recent years,with the rapid development of the world nuclear industry,uranium demand is increasing,inevitably produce waste water and waste residue.China is a depleted uranium country,now proven uranium reserves in the world after the 10 th,and the size of the deposit and the main small(accounting for more than 60% of the total reserves).The safety of uranium resources and the safety of nuclear power environment have become the key to the development of nuclear power.In this paper,uranium(?)and pyrite are carried out in view of the common geological phenomena of coexistence of uranium and pyrite and hydroxyapatite,Hydroxyapatite interactions in electrons,ions,atoms and molecules.The experimental results show that the process of adsorption of uranium from pyrite is controlled by the diffusion process of liquid film,mainly by chemical adsorption,and the adsorption process is an endothermic process.The enthalpy change ?H = 55.65 KJ /mol,the entropy change ? S = 241.31 J /(mol.K),the free energy ? G =-16.29 KJ /mol,the quasi-two reaction rate constant K2 = 0.0085 mg(XRD),Fourier transform infrared spectroscopy(FTIR),photoelectron spectroscopy(XPS),scanning electron microscopy(SEM),energy dispersive spectroscopy(XRD),scanning electron microscopy(SEM)(EDS).It was confirmed that pyrite could reduce the uranium ion and produce non-lamellar uranium compound precipitate and adsorbed on the surface of pyrite.Using cyclic voltammetry(CV)technique,the results showed that pyrite The ore-reducing uranium ion has a transition state U(V),and its node is the molar ratio of pyrite to uranium0.63;pyrite pyroelectric spectroscopy(XPS)shows that pyrite and uranium before and after the role of S Layer electron binding energy can be significantly changed,and Fe outer layer of electron binding energy also The S and Fe elements in the pyrite also play a role in the process of pyrite reduction,but the effect of element S is more obvious.It was also confirmed that humic acid had an inhibitory effect on the reduction of uranium from pyrite,and thiobacillus ferrooxidans had synergistic effect on pyrite reduction.The photocatalytic activity of UO2(OH)2,(UO2)3(OH)5+ and(UO2)4(OH)7+ ions were gradually decreased with the increase of pH value and UO22+ ions decreased rapidly with PHREEQC theory,When the molar ratio of pyrite to uranium is more than 0.75,U(IV)precipitation is initiated.When the molar ratio is greater than about 1.75,uranium(VI)is completely reduced to precipitated form of U(IV).The increase of temperature is beneficial to improve the reduction ability of pyrite.When the temperature is higher than 150 ?,the ability of uranium to reduce uranium is the best.The results of batch adsorption test show that the process of adsorption of uranium by hydroxyapatite is more consistent with the diffusion of liquid film,and the adsorption rate is more suitable than quasi-second-order kinetics.According to the different concentration of uranium,hydroxyapatite Adsorption.There are two different adsorption modes of uranium,which meet the Langmuir isothermal adsorption when the initial concentration of uranium is 20 ~ 100 mg / L.The initial concentration of uranium is 700 ~ 1000 mg / L,which is in accordance with Freundlich isothermal adsorption,indicating that when uranium concentration is low Ion exchange adsorption mainly in the uranium concentration can occur when the multi-layer physical adsorption.The maximum adsorption capacity Q2= 0.137 mg /(g.min)and the maximum adsorption capacity Qm = 1000 mg / g were obtained by the theoretical calculation.X-ray powder diffraction(XRD),scanning electron microscopy(SEM)(EDS)and cyclic voltammetry(CV).It was shown that the phase change occurred after adsorption of large amounts of uranium by hydroxyapatite,and changed from regular hexagonal to tetragonal system,and there was no change in valence state.Pyrite is a necessary factor for uranium mineralization,and apatite is favorable for the formation of uranium-rich ore.Microorganisms promote the enrichment of uranium,and humic acid and uranium with strong ability to complex organic matter is not conducive to the reduction and precipitation of uranium.