Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI 48109, United States.
Water Res. 2011 Nov 1;45(17):5727-35. doi: 10.1016/j.watres.2011.08.026. Epub 2011 Aug 26.
Iron sulfide (FeS) has been demonstrated to have a high removal capacity for arsenic (As) in reducing environments. However, FeS may be present as a coating, rather than in nanoparticulate form, in both natural and engineered systems. Frequently, the removal capacity of coatings may be different than that of nanoparticulates in batch systems. To assess the differences in removal mechanisms between nanoparticulate FeS and FeS present as a coating, the solid phase products from the reaction of As(III) with FeS-coated sand and with suspensions of nanoparticulate (NP) FeS were determined using x-ray absorption spectroscopy and x-ray photoelectron spectroscopy. In reaction with NP FeS at pH 5, As(III) was reduced to As(II) to form realgar (AsS), while at pH 9, As(III) adsorbed as an As(III) thioarsenite species. In contrast, in the FeS-coated sand system, As(III) formed the solid phase orpiment (As(2)S(3)) at pH 5, but adsorbed as an As(III) arsenite species at pH 9. These different solid reaction products are attributed to differences in FeS concentration and the resultant redox (pe) differences in the FeS-coated sand system versus suspensions of NP FeS. These results point to the importance of accounting for differences in concentration and redox when making inferences for coatings based on batch suspension studies.
硫化亚铁（FeS）已被证明在还原环境中对砷（As）具有高去除能力。然而，在自然和工程系统中，FeS 可能以涂层的形式存在，而不是纳米颗粒形式。通常，涂层的去除能力可能与批处理系统中纳米颗粒的去除能力不同。为了评估纳米颗粒 FeS 和作为涂层存在的 FeS 之间的去除机制差异，使用 X 射线吸收光谱和 X 射线光电子能谱确定了 As(III)与 FeS 涂层砂和纳米颗粒（NP）FeS 悬浮液反应的固相产物。在与 NP FeS 在 pH 5 下反应时，As(III)被还原为 As(II)形成雄黄（AsS），而在 pH 9 时，As(III)作为 As(III)硫代砷酸盐物种吸附。相比之下，在 FeS 涂层砂系统中，As(III)在 pH 5 下形成固相雄黄（As(2)S(3))，但在 pH 9 下作为 As(III)砷酸盐物种吸附。这些不同的固相反应产物归因于 FeS 浓度的差异以及 FeS 涂层砂系统与 NP FeS 悬浮液之间的氧化还原（pe）差异。这些结果表明，在基于批处理悬浮研究对涂层进行推断时，考虑浓度和氧化还原差异非常重要。
