零价铁对奥奈达希瓦氏菌还原U(Ⅵ)的影响及机制

Effect and mechanism of zero-valent iron on reducing U(Ⅵ) by S.oneidensis

采用现代分析方法探讨零价铁（ZVI）与奥奈达希瓦氏菌（S.oneidensis）MR-1还原U（Ⅵ）的效果与机制。结果表明：ZVI与S.oneidensis均能够还原U（Ⅵ）;在厌氧条件下,ZVI与S.oneidensis还原U（Ⅵ）存在协同作用。当p H为7、温度为30℃、U（Ⅵ）的初始浓度为20 mg/L、ZVI的投加量为1.0 g/L时,24 h S.oneidensis对U（Ⅵ）还原率达到96.9%;在0.5～2.0 g/L范围内,U（Ⅵ）的还原率随ZVI投量的增加而上升;在U（Ⅵ）初始浓度5.0～50.0mg/L内,U（Ⅵ）的还原率与其浓度正相关。ZVI、Fe3O4和Fe2O3均能明显促进U（Ⅵ）的还原,而可溶态的Fe（Ⅲ）对U（Ⅵ）的还原具有明显的抑制作用。其他离子Cu2＋、Ca2＋、Mn2＋和NO3-对U（Ⅵ）的还原存在抑制作用,以Cu2＋的影响最大,Ca2＋的影响次之,SO42-对U（Ⅵ）的还原影响较小。XPS分析结果表明,ZVI表面吸附和沉积了U（Ⅵ）和U（Ⅳ）两种价态的U元素,反应后的铀大部分形成了稳定的UO2。

The effects and mechanism of U（Ⅵ） reduction by Shewanella oneidensis （S.oneidensis） MR-1 with zero-valent iron（ZⅥ） were evaluated. The results show that either ZⅥ or bacteria can reduce U（Ⅵ） in the solution and under anaerobic conditions, a cooperative action of ZⅥ and the bacteria S.oneidensis is observed in reducing process of U（Ⅵ）. Under condition of pH 7.0, temperature 30 ℃, the initial concentration of U （Ⅵ） 20 mg/L and ZⅥ addition 1.0 g/L, the reduction rate of U（Ⅵ） reaches 96.9% by S.oneidensis reduction for 24 h. The reduction rate of U（Ⅵ） is improved with increasing amount of ZⅥ in the range of 0.5-2.0 g/L, and the reduction rate of U（Ⅵ） is positive correlated with its initial concentration in the range of 5.0-50.0 mg/L. Fe304, FeEO3 and ZⅥ are effective accelerators for bioreduction of U（Ⅵ）, and soluble Fe（Ⅲ） can remarkably inhibit U（Ⅵ） bioreduction. The other coexistence ions, such as Cuz＋, Ca2＋, Mn2＋ and NO3-, show a remarkable negative effect on U（Ⅵ） reduction, and among these ions, the negative effect of Cu2＋ is the greatest and that of Ca2＋ is the second. SO42- has less influence on U（Ⅵ） bioreduction. XPS results indicate the deposition of U element are in forms of U（Ⅵ） and U（IV） on iron filings surface, and the reduction product U（IV） is most likely to be in the form of UO2.