State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China; School of Agriculture and Food, The University of Melbourne, Victoria 3010, Australia.
College of Agricultural Sciences and Engineering, Hohai University, Nanjing 210098, China.
J Environ Sci (China). 2022 May;115:308-318. doi: 10.1016/j.jes.2021.08.001. Epub 2021 Aug 19.
Antimony (Sb) is a recognized priority pollutant with toxicity that is influenced by its migration and transformation processes. Oxidation of Fe(II) to Fe(III) oxides, which is a common phenomenon in the environment, is often accompanied by the formation of Mn(III/IV) and might affect the fate of Sb. In this study, incorporated Mn(III) and sorbed/precipitated Mn(III/IV) associated with lepidocrocite were prepared by adding Mn(II) during and after Fe(II) oxidation, respectively, and the effects of these Mn species on Sb fate were investigated. Our results indicated that the association of these Mn species with lepidocrocite obviously enhanced Sb(III) oxidation to Sb(V), while concomitantly inhibiting Sb sorption due to the lower sorption capacity of lepidocrocite for Sb(V) than Sb(III). Additionally, Mn oxide equivalents increased in the presence of Sb, indicating that Sb oxidation by Mn(III/IV) associated with lepidocrocite was a continuous recycling process in which Mn(II) released from Mn(III/IV) reduction by Sb(III) could be oxidized to Mn(III/IV) again. This recycling process was favorable for effective Sb(III) oxidation. Moreover, Sb(V) generated from Sb(III) oxidation by Mn(III/IV) enhanced Mn(II) sorption at the beginning of the process, and thus favored Mn(III/IV) formation, which could further promote Sb(III) oxidation to Sb(V). Overall, this study elucidated the effects of Mn(III/IV) associated with lepidocrocite arisen from Fe(II) oxidation on Sb migration and transformation and revealed the underlying reaction mechanisms, contributing to a better understanding of the geochemical dynamics of Sb.
锑 (Sb) 是一种公认的优先污染物，其毒性受其迁移转化过程的影响。Fe(II) 氧化为 Fe(III) 氧化物是环境中常见的现象，通常伴随着 Mn(III/IV) 的形成，这可能会影响 Sb 的归宿。在这项研究中，通过在 Fe(II) 氧化过程中及之后添加 Mn(II)，分别制备了与针铁矿结合的 Mn(III)和吸附/沉淀的 Mn(III/IV)，并研究了这些 Mn 物种对 Sb 命运的影响。研究结果表明，这些 Mn 物种与针铁矿的结合明显促进了 Sb(III)向 Sb(V)的氧化，同时由于 Sb(V)的吸附容量低于 Sb(III)，因此抑制了 Sb 的吸附。此外，在 Sb 的存在下，Mn 氧化物当量增加，表明 Sb(V)是由 Sb(III)氧化 Mn(III/IV)形成的，这是一个连续的循环过程，其中 Sb(III)还原 Mn(III/IV)释放的 Mn(II)可以再次氧化为 Mn(III/IV)。这种循环过程有利于 Sb(III)的有效氧化。此外，由 Mn(III/IV)氧化 Sb(III)生成的 Sb(V)在过程初期增强了 Mn(II)的吸附，从而有利于 Mn(III/IV)的形成，这可以进一步促进 Sb(III)向 Sb(V)的氧化。总的来说，本研究阐明了 Fe(II)氧化产生的与针铁矿结合的 Mn(III/IV)对 Sb 迁移转化的影响，并揭示了潜在的反应机制，有助于更好地理解 Sb 的地球化学动力学。
