Tokunaga Kohei, Tanaka Kazuya, Takahashi Yoshio, Kozai Naofumi
Ningyo-Toge Environmental Engineering Center, Japan Atomic Energy Agency, Tomata, Okayama 708-0698, Japan.
Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan.
Environ Sci Technol. 2023 Feb 28;57(8):3166-3175. doi: 10.1021/acs.est.2c08939. Epub 2023 Feb 13.
Coprecipitation of radionuclides with barite has been studied to remove radionuclides from radioactive liquid waste because of its excellent removal efficiency; however, little information exists concerning the stability of the ions coprecipitated with barite. This study systematically investigated the stability of iodate, selenite, and selenate coprecipitated with barite via leaching tests. These oxyanions were gradually leached from the oxyanion-bearing barite into ultrapure water over time. Leaching of the oxyanions significantly increased in leaching solutions containing NaCl (pH 5.3), NaNO (pH 5.9), and NaSO (pH 5.7). Conversely, leaching of the oxyanions was suppressed in KHPO solution (pH 8.5), indicating that phosphate stabilized the oxyanion-bearing barite. The effect of phosphate treatment on oxyanion-bearing barite was further investigated. The results showed that the barite surface was modified with phosphate, and a thin surface layer of a barium phosphate-like structure was formed. The amount of oxyanions leached from the phosphate-treated samples into leaching solutions containing NaCl or NaNO was much lower than the amounts leached from the untreated barite samples into ultrapure water. The barite coprecipitation combined with subsequent phosphate treatment may be a promising method to efficiently remove iodate, selenite, and selenate from wastewater and stabilize them as barite coprecipitates.
由于重晶石对放射性核素具有出色的去除效率，因此人们对放射性核素与重晶石的共沉淀进行了研究，以从放射性废液中去除放射性核素；然而，关于与重晶石共沉淀的离子的稳定性，相关信息却很少。本研究通过浸出试验系统地研究了与重晶石共沉淀的碘酸盐、亚硒酸盐和硒酸盐的稳定性。随着时间的推移，这些含氧阴离子从重晶石中逐渐浸出到超纯水中。在含有氯化钠（pH 5.3）、硝酸钠（pH 5.9）和硫酸钠（pH 5.7）的浸出溶液中，含氧阴离子的浸出显著增加。相反，在磷酸二氢钾溶液（pH 8.5）中，含氧阴离子的浸出受到抑制，这表明磷酸盐使含含氧阴离子的重晶石更加稳定。进一步研究了磷酸盐处理对含含氧阴离子重晶石的影响。结果表明，重晶石表面被磷酸盐改性，形成了一层类似磷酸钡结构的薄表面层。从经磷酸盐处理的样品浸出到含有氯化钠或硝酸钠的浸出溶液中的含氧阴离子量，远低于从未经处理的重晶石样品浸出到超纯水中的量。重晶石共沉淀结合后续的磷酸盐处理可能是一种从废水中有效去除碘酸盐、亚硒酸盐和硒酸盐并将它们稳定地作为重晶石共沉淀物的有前景的方法。
