Low concentration of Fe(II) to enhance the precipitation of U(VI) under neutral oxygen-rich conditions
Low concentration of Fe(II) to enhance the precipitation of U(VI) under neutral oxygen-rich conditions
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中性富氧条件下低浓度 Fe(II) 促进 U(VI) 沉淀
DOI：
10.1016/j.scitotenv.2019.134827
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发表时间：
2019
影响因子：
9.8
通讯作者：
Kaixuan Tan
中科院分区：
文献类型：
--
作者：
Yanpei Xie;Qi Fang;Mi Li;Sainan Wang;Yingfeng Luo;Xiaoyan Wu;Junwen Lv;Wenfa Tan;Hongqiang Wang;Kaixuan Tan
利用自然界中普遍存在的亚铁离子（Fe（II））固定U（VI）被认为是一种有效的、环境友好的方法，可以延缓U（VI）在核环境和地表环境中的迁移。本文通过Fe-U共沉淀实验，研究了富氧条件下少量Fe（II）诱导铀（U）沉淀的机理和稳定性。实验结果表明，在中性富氧条件下，Fe（II）对U（VI）的沉降率大于96%，比不加Fe（II）时高36%，比无氧条件下高16%。Fe-U共沉淀物在微酸性至中性和富氧条件下保持稳定。Fe（II）主要以低结晶氧化铁氢氧化物的形式沉淀。U（VI）主要以三种形式沉淀：16-20%的U以氢氧化铀酰和变硫铅石的形式吸附在固体表面; 52-56%的U以不连续的铀酰相吸附在氧化铁氢氧化物的内孔中; 27-29%的U可能以U（V）和U（VI）的形式结合到FeO（OH）结构中。通过单电子还原生成的U（V）对O2的氧化和酸溶解有一定的抵抗力。此外，在0.01 M的盐酸溶液中，24 h内可萃取近70%的U和15%的Fe，表明低浓度Fe（II）与O2结合固定U（VI）在铀水溶液的分离和回收中具有潜在的应用价值。
Immobilization of U(VI) by naturally ubiquitous ferrous ions (Fe(II)) has been considered as an efficient and ecofriendly method to retard the migration of aqueous U(VI) at many nuclear sites and surface environments. In this study, we conducted Fe-U coprecipitation experiments to investigate the mechanism and stability of uranium (U) precipitation induced by a small quantity of Fe(II) under oxygen-rich conditions. The experimental results suggest that the sedimentation rates of U(VI) by Fe(II) under neutral oxygen-rich conditions are more than 96%, which are about 36% higher than those without Fe(II) and 16% higher than those under oxygen-free conditions. The Fe-U coprecipitates were observed to remain stable under slightly acidic to neutral and oxygen-rich conditions. Fe(II) primarily settles down as low-crystalline iron oxide hydroxide. U(VI) mainly precipitates as three forms: 16–20% of U forms uranyl hydroxide and metaschoepite, which is absorbed on the surface of the solids; 52–56% of U is absorbed as discrete uranyl phases at the internal pores of iron oxide hydroxide; and 27–29% of U is probably incorporated into the FeO(OH) structure as U(V) and U(VI). The U(V) generated via one-electron reduction is somewhat resistant to the oxidation of O2and the acid dissolution. In addition, nearly 70% of U and only about 15% of Fe could be extracted in 24 h by a hydrochloric acid solution with the H+concentration ([H+]) of 0.01 M, revealing that U(VI) immobilization by low concentration of Fe(II) combined with O2has potential applications in the separation and recycling of aqueous uranium.