Giammar D E, Hering J G
California Institute of Technology, Environmental Engineering Science, Pasadena, California 91125, USA.
Environ Sci Technol. 2001 Aug 15;35(16):3332-7. doi: 10.1021/es0019981.
The sorption of uranium on mineral surfaces can significantly influence the fate and transport of uranium contamination in soils and groundwater. The rates of uranium adsorption and desorption on a synthetic goethite have been evaluated in batch experiments conducted at constant pH of 6 and ionic strength of 0.1 M. Adsorption and desorption reactions following the perturbation of initial states were complete within minutes to hours. Surface-solution exchange rates as measured by an isotope exchange method occur on an even shorter time scale. Although the uranium desorption rate was unaffected by the aging of uranium-goethite suspensions, the aging process appears to remove a portion of adsorbed uranium from a readily exchangeable pool. The distinction between sorption control and precipitation control of the dissolved uranium concentration was also investigated. In heterogeneous nucleation experiments, the dissolved uranium concentration was ultimately controlled by the solubility of a precipitated uranyl oxide hydrate. The X-ray diffraction pattern of the precipitate is characteristic of the mineral schoepite. Precipitation is kinetically hindered at low degrees of supersaturation. In one experiment, metastable sorption controlled dissolved uranium concentrations in excess of the solubility limit for more than 30 d.
铀在矿物表面的吸附作用会显著影响土壤和地下水中铀污染物的归宿与迁移。在pH值恒定为6、离子强度为0.1 M的条件下进行的批量实验中，评估了铀在合成针铁矿上的吸附和解吸速率。初始状态受到扰动后的吸附和解吸反应在数分钟至数小时内完成。通过同位素交换法测得的表面 - 溶液交换速率发生在更短的时间尺度上。虽然铀的解吸速率不受铀 - 针铁矿悬浮液老化的影响，但老化过程似乎从易于交换的池中去除了一部分吸附的铀。还研究了溶解铀浓度的吸附控制和沉淀控制之间的区别。在非均相成核实验中，溶解铀浓度最终由沉淀的铀酰氧化物水合物的溶解度控制。沉淀物的X射线衍射图谱是水磷铀矿矿物的特征。在低过饱和度下，沉淀在动力学上受到阻碍。在一个实验中，亚稳吸附控制溶解铀浓度超过溶解度极限达30多天。
