State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang, People's Republic of China.
School of Nuclear Science and Engineering, East China University of Technology, Nanchang, 330013, China.
Environ Sci Pollut Res Int. 2022 Aug;29(38):57466-57478. doi: 10.1007/s11356-022-19931-3. Epub 2022 Mar 30.
Tantalum-niobium ore belongs to associated radioactive ore, which is accompanied by a certain amount of radioactive uranium and thorium. The remaining slag is enriched with a large number of radionuclides; after weathering, natural rainfall, and surface water scouring, radioactive elements such as uranium, thorium, and some heavy metal elements are exposed or washed into the soil, which poses a threat to the ecological environment and human health. In this study, for characterization analysis during, before, and after leaching, dynamic simulation experiment was carried out on a Ta-Nb slag sample in Jiangxi, China. From SEM analysis, the soluble substances adsorbed on the slag surface dissolve into the solution after leaching in simulated rainfall, and the remained slag becomes smooth with different particle sizes. The XRD diffraction analysis of the sample showed that after leaching in simulated rainfall, the existing forms of elements are different. pH of the leachate of Ta-Nb slag is 1.79; Ta-Nb slag contains many rare metal elements, nonmetal elements, radioactive elements, and some salt compounds; and the content of thorium is higher than that of uranium by EDS analysis. The release of uranium and thorium is obviously affected by the amount of leachate and pH. Under the lower pH of leaching solution, the release of uranium and thorium is more effective. The results of Fick diffusion theory and Elovich equation show that the release and migration mode of uranium and thorium in Ta-Nb slag are mainly surface elution; under acidic conditions, the release and migration of uranium and thorium are faster. This study provides basic data and scientific information for solving the key problems of pollution control of associated radioactive waste in environmental protection.
钽铌矿属于伴生放射性矿，伴生一定量的铀、钍放射性元素。尾矿中赋存大量的放射性核素；经风化后，自然降雨、地表水冲刷，铀、钍等放射性元素以及部分重金属元素暴露或被冲刷进入土壤中，对生态环境和人体健康构成威胁。本研究采用动态模拟实验，对江西某钽铌渣样进行了浸出前、浸出时及浸出后特性分析。从 SEM 分析来看，浸出过程中渣样表面吸附的可溶性物质溶解到溶液中，渣样表面变得粗糙，粒径大小不一。浸出后样品的 XRD 衍射分析表明，元素的存在形式不同。钽铌渣浸出液的 pH 值为 1.79；钽铌渣中含有多种稀有金属元素、非金属元素、放射性元素和一些盐类化合物；经 EDS 分析，钍的含量高于铀。铀、钍的释放受浸出液量和 pH 值的影响明显。在较低 pH 值的浸出液中，铀、钍的释放效果更明显。Fick 扩散理论和 Elovich 方程的结果表明，铀、钍在钽铌渣中的释放和迁移方式主要是表面溶出；在酸性条件下，铀、钍的释放和迁移速度更快。本研究为解决环境保护中伴生放射性废物污染控制的关键问题提供了基础数据和科学信息。
