Sequestration and retention of uranium(VI) in the presence of hydroxylapatite under dynamic geochemical conditions
Sequestration and retention of uranium(VI) in the presence of hydroxylapatite under dynamic geochemical conditions
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DOI：
10.1071/en07060
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发表时间：
2008-02
影响因子：
4.3
通讯作者：
D. Wellman;J. N. Glovack;K. Parker;E. L. Richards;E. Pierce
中科院分区：
文献类型：
--
作者：
D. Wellman;J. N. Glovack;K. Parker;E. L. Richards;E. Pierce
环境背景。由于过去的核作业，地表和地下地质介质被重金属和放射性核素污染是美国能源部综合设施内的一个重大问题。已经提出了许多基于磷酸盐的补救策略，以将羟基磷灰石直接或间接（即通过原位沉淀）引入地下区域，作为金属和放射性核素（如铀）螯合的有效吸附剂。这里提出的结果说明了变量的地球化学条件的重要性，在羟基磷灰石的存在下，铀的封存和长期保留的机制。抽象的。许多用于补救重金属和放射性核素的固相和水相磷酸盐技术都有一个共同的前提，即通过羟基磷灰石进行螯合。络合反应和水解一般排除锕系元素纳入晶内网站，而是，表面吸附和沉淀的螯合锕系元素的重要机制。pH值的影响，水的形态，和可用性的矿物，如羟基磷灰石的活性表面位点有显着的影响的机制和程度的螯合和保留的带电荷的污染物，如铀。然而，很少有人注意到在补救活动中可能遇到的动态地球化学条件下羟基磷灰石对铀的螯合和保留。我们提出了一项调查的结果，评估去除铀的羟基磷灰石在接近平衡的系统相对于羟基磷灰石，和动态水的地球化学条件的影响，如那些遇到的修复活动期间和之后，保留铀。这里提出的结果支持以前的调查表明，羟基磷灰石封存铀的效率，并说明地球化学条件的重要性，包括表面性质和水的形态变化，对铀的封存和保留。
Environmental context. Contamination of surface and subsurface geologic media by heavy metals and radionuclides is a significant problem within the United State Department of Energy complex as a result of past nuclear operations. Numerous phosphate-based remediation strategies have been proposed to introduce hydroxylapatite directly or indirectly (i.e. through in situ precipitation) into subsurface regimes to act as an efficient sorbent for sequestration of metals and radionuclides such as uranium. Results presented here illustrate the importance of variable geochemical conditions on the mechanism of sequestration and long-term retention of uranium in the presence of hydroxylapatite. Abstract. Numerous solid- and aqueous-phase phosphate-based technologies for remediating heavy metals and radionuclides have the common premise of sequestration by hydroxylapatite. Complexation reactions and hydrolysis generally preclude actinides from incorporation into intracrystalline sites; rather, surface sorption and precipitation are significant mechanisms for the sequestration of actinides. The effect of pH, aqueous speciation, and the availability of reactive surface sites on minerals such as hydroxylapatite have a significant impact on the mechanism and degree of sequestration and retention of variably charged contaminants such as uranium. Yet, little attention has been given to the sequestration and retention of uranium by hydroxylapatite under dynamic geochemical conditions that may be encountered during remediation activities. We present the results of an investigation evaluating the removal of uranium by hydroxylapatite in systems near equilibrium with respect to hydroxylapatite, and the effect of dynamic aqueous geochemical conditions, such as those encountered during and subsequent to remediation activities, on the retention of uranium. Results presented here support previous investigations demonstrating the efficiency of hydroxylapatite for sequestration of uranium and illustrate the importance of geochemical conditions, including changes to surface properties and aqueous speciation, on the sequestration and retention of uranium.