Np在Np-水-膨润土平衡体系中的形态及价态分布
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摘要
采用批式法和溶剂萃取法,研究了Np在Np-水-膨润土平衡体系中的形态及价态分布以及pH值对形态及价态分布的影响。结果表明:在Np-水-膨润土平衡体系中,水相中的Np全部为Np(Ⅴ),固相中的Np为Np(Ⅳ)、Np(Ⅴ);pH=8~9时,随着pH值的升高,固相中Np的比例升高,pH>9时,固相中Np的比例降低;随着CO3_~(2-)浓度的升高,固相中Np的比例降低。PHREEQCI计算结果表明:pH<9时,Np在水相中的主要形态为NpO~+_2,pH>9时NpO_2OH逐渐成为Np在水相中的主要形态;在高CO_3~(2-)浓度条件下,NpO_2(CO_3)_2~(3-)、NpO_2(CO_3)~(5-)_3是Np在水相中的主要形态;pH值对Np在水相和固相中的价态分布无影响。
The speciation and valence distributions and effect of pH on the speciation and valence distributions of Np in the balanced system of Np-groundwater-bentonite were studied by batch experiments and solvent extraction methods.The results indicate that the valence of Np in groundwater is penta-valent state,and tetra-and penta-valent states were obtained on bentonite.With the increase of pH,the percentage of Np(Ⅴ)in bentonite increases at first and then decreases at pH>9.With the increase of CO_3~(2-),the percentage of Np(Ⅴ)in bentonite decreases.The calculation results of PHREEQCI show that NpO~+_2is the main speciation of Np at pH<9,and NpO_2 OH at pH>9.NpO_2(CO_3)_2~(3-)and NpO_2(CO_3)~(5-)_3are the main speciations of Np at high concentration CO_3~(2-)solution.The valence of Np is not affected by pH.
The speciation and valence distributions and effect of pH on the speciation and valence distributions of Np in the balanced system of Np-groundwater-bentonite were studied by batch experiments and solvent extraction methods.The results indicate that the valence of Np in groundwater is penta-valent state,and tetra-and penta-valent states were obtained on bentonite.With the increase of pH,the percentage of Np(Ⅴ)in bentonite increases at first and then decreases at pH>9.With the increase of CO_3~(2-),the percentage of Np(Ⅴ)in bentonite decreases.The calculation results of PHREEQCI show that NpO~+_2is the main speciation of Np at pH<9,and NpO_2 OH at pH>9.NpO_2(CO_3)_2~(3-)and NpO_2(CO_3)~(5-)_3are the main speciations of Np at high concentration CO_3~(2-)solution.The valence of Np is not affected by pH.
引文
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[12]DEL-NERO M,ADVOCAT T,JOLLIVET P,et al.Sorption of neptunium(Ⅴ)on an alteration gel of alumino-borosilicate glasses and on synthetic silicate gels[C]∥Proc 2nd Int Symp Nuclear Fuel Cycle Safety Eng Res Facility NUCEF’98.Tokyo,Japan:Japan Atomic Energy Research Institute,1999:584-595.
[13]KOHLER M,HONEYMAN B D,LECKIE J O.Neptunium(Ⅴ)sorption on hematite(α-Fe2O3)in aqueous suspension:The effect of CO2[J].Radiochim Acta,1999,85:33-48.
[2]ITAGAKI S,TANAKA K,YAMAWAKI M.Neptunium chemical behavior in underground environments using ultrafiltration and centrifugation[J].Radiochimica Acta,1991,52/53:91-94.
[3]姚军.237 Np在模拟处置条件下的迁移行为研究[D].北京:中国原子能科学研究院,2006.
[4]MEYER R E,ARNOLD W D,CASE F I.Valence effects on the adsorption of nuclides on rocksand minerals,NUREG/CR-3389(ORNL-5978)[R].Oak Ridge,Tennessee:Commission by Oak Ridge National Laboratory,1984.
[5]SUSAK N J,FRIEDMAN A,FRIED S,et al.The reduction of neptunium(Ⅵ)by basalt and olivine[J].Nuclear Technology,1983,63:266-270.
[6]NAKATA K,NAGASAKI S.Sorption and desorption kinetics of Np(Ⅴ)on magnetite and hematite[J].Radiochim Acta,2000,88:453-457.
[7]GRIGORIVE M S,FEDOSEEV A M.Study of interaction of Pu(Ⅳ)and Np(Ⅳ,Ⅴ,Ⅵ)with Fe hydroxides to predict the behavior of actinides in environmental media[J].Radiochim Acta,2001,89:95-100.
[8]NAKATA K,NAGASAKI S.Reduction rate of neptunium(Ⅴ)in heterogeneous solution with magnetite[J].Radiochim Acta,2004,92:145-149.
[9]NAKATA K,NAGASAKI S.Sorption and reduction of neptunium(Ⅴ)on the surface of iron oxides[J].Radiochim Acta,2002,90:665-669.
[10]WU T,AMAYRI S,REICH T.Neptunium(Ⅴ)sorption onto gibbsite[J].Radiochim Acta,2009,97:99-103.
[11]DEL-NERO M,BEN-SARD K,MADE′B,et al.Effect of pH and carbonate concentration insolution on the sorption of neptunium(Ⅴ)by hydrargilite:Application of the non-electrostatic model[J].Radiochim Acta,1998,81:133-141.
[12]DEL-NERO M,ADVOCAT T,JOLLIVET P,et al.Sorption of neptunium(Ⅴ)on an alteration gel of alumino-borosilicate glasses and on synthetic silicate gels[C]∥Proc 2nd Int Symp Nuclear Fuel Cycle Safety Eng Res Facility NUCEF’98.Tokyo,Japan:Japan Atomic Energy Research Institute,1999:584-595.
[13]KOHLER M,HONEYMAN B D,LECKIE J O.Neptunium(Ⅴ)sorption on hematite(α-Fe2O3)in aqueous suspension:The effect of CO2[J].Radiochim Acta,1999,85:33-48.