某铀尾矿库渗水中铀的化学形态和影响因素模拟分析

Chemical Species and Influence Factors Analysis of Uranium in the Seepage of One Uranium Tailings Pond

铀尾矿库中铀是污染周边环境的主要根源,其半衰期长难以处置。本文以我国南方某铀尾矿库为例,利用地球化学模拟软件PHREEQC对尾矿库渗水铀的主要化学形态和影响因素进行模拟分析。结果表明:(1)尾矿库渗水中铀主要以正六价存在,约占总铀浓度的99.99%,且其6种主要化学形态所占百分比大小为:UO_2F^+>UO_2F_2>UO_2SO_4>(UO_2SO_4)_2^(2-)>UO_2^(2+)>UO_2F_3^-。(2)铀的6种主要化学形态摩尔浓度在4.1<pH值<6.1受影响较小,而当pH值>6.1时,摩尔浓度下降明显;温度除了对UO_2(SO_4)_2^(2-)的摩尔浓度影响较大之外,对铀的其他主要化学形态摩尔浓度影响较小。(3)随着p E值的增大,渗水溶液中U6+摩尔浓度减小,U^(4+)和U^(5+)摩尔浓度增加。(4)该场地下U^(6+)迁移占绝对优势,建议采用阻滞材料阻滞迁移。

Uranium of uranium tailings pond is the main source polluting the surrounding environment and its long half - life is difficult to be dealt with. In this paper, a uranium tailings pond in southern China is used as an example to analyze the main chemical forms and influencing factors of uranium in seepage using geophysical simulation software PHREEQC. The results show that, （1） Uranium is mainly present in the seepage, accounting for 99. 99% of the total uranium concentration, and the percentage of the six main chemical forms follows UO2F＋ 〉 U02F2 〉 UO2SO4 〉（U02S04 〉 UO2 ＋ 〉 U02F3 ） . （2） The six major chemical forms of uranium in the molar concentration of 4. 1 〈pH 〈6. 1 are less affected, but when pH 〉6. 1, the molar concentration decreased significantly and the temperature has little effect on the molar concentration of other major chemical forms of uranium, except for the greater influence on the molar concentration of UO2 （ SO4 . （3） With the increase of pE value, the concentration of U6＋ in the infil-tration solution decreases and the molar concentration of U4＋ and U5＋ increases. （4） The migration of U6 ＋ in seepage is the absolute advantage, and the migration of retarded materials can be retarded.