Chemistry Department, University of Cyprus, P1678 Nicosia, Cyprus.
J Environ Radioact. 2010 Aug;101(8):601-5. doi: 10.1016/j.jenvrad.2010.03.006. Epub 2010 Mar 31.
The present study aims to assess the effect of redox conditions existing within the tailings dump on the stability of phosphogypsum (e.g. sulphate reduction) and uranium(VI). Phosphogypsum sampling and in-situ measurements were carried out at a coastal tailings dump in Vasiliko Cyprus, pH, E(H) and solubility experiments were performed in simulated laboratory systems and thermodynamic calculations using MINTEQA2. Generally, in the open tailings dump oxidizing conditions predominate stabilizing sulphur and uranium in their hexavalent oxidation states. On the other hand, after the application of a soil/vegetative cover and in the presence of natural organic matter, anoxic conditions prevail (E(H) < -70 mV) resulting in S(VI) and U(VI) reduction to S(-II) and U(IV), respectively. Although, the sulphide anion can form very insoluble compounds with heavy metal ions (e.g. Cd(II), Pb(II) etc.) and U(IV) oxide has very low solubility, partial reduction of sulphate to sulphide within gypsum may affect the stability of phosphogypsum resulting in enhanced erosion of the material by rain- and seawater and washing out of contaminants in particulate/colloidal form.
本研究旨在评估尾矿库内存在的氧化还原条件对磷石膏（例如硫酸盐还原）和铀（VI）稳定性的影响。在塞浦路斯瓦西利科的一个沿海尾矿库进行了磷石膏采样和现场测量，在模拟实验室系统中进行了 pH、E(H) 和溶解度实验，并使用 MINTEQA2 进行了热力学计算。一般来说，在露天尾矿库中，氧化条件占主导地位，将硫和铀稳定在其六价氧化态。另一方面，在施加土壤/植被覆盖层并存在天然有机质的情况下，缺氧条件占主导地位（E(H) < -70 mV），导致 S(VI) 和 U(VI) 分别还原为 S(-II) 和 U(IV)。尽管硫阴离子可以与重金属离子（例如 Cd(II)、Pb(II) 等）形成非常难溶的化合物，并且 U(IV) 氧化物的溶解度非常低，但石膏内硫酸盐的部分还原为硫化物可能会影响磷石膏的稳定性，导致材料因雨水和海水的侵蚀而加速侵蚀，并以颗粒/胶体形式洗出污染物。
