Inducing magnetite formation by microbial Fe(II) oxidation in the presence of mineral nucleation sites: Evaluating a novel approach to heavy metal remediation in the environment.

生物磁铁矿(Fe3O4)纳米粒子是由Fe(III)还原细菌在环境中产生的Fe(II)/Fe(III)混合矿物，具有小尺寸(&lt；50 nm)、高活性的Fe(II)表面层和有机涂层。所有这些特性使生物磁铁矿适合于潜在的修复策略。铁(II)-氧化菌通常不与磁铁矿的形成有关，相反，更常见的是铁(III)氧化氢氧化物，如针铁矿(α-FeOOH)和氢氧化铁(简称Fe(OH)3)。我们小组最近的工作表明，在微生物Fe(II)氧化过程中，少量的磁铁矿纳米颗粒的存在可以作为成核位置，并导致额外的磁铁矿的形成。目前尚不清楚这种新的磁铁矿是由自发形成的核组成，还是由添加的成核位生长出来的更大的颗粒组成。为了将微生物来源的生物成因磁铁矿应用于修复目的，需要了解磁铁矿的形成机理及其反应活性。因此，我们建议用Fe(II)氧化菌进行实验来详细研究成核位的影响，选择包括比表面积和成核位浓度在内的一些变量来观察磁铁矿的形成速度和最终产生的矿物相的变化。此外，我们建议进行批量实验，以测试用于修复有毒金属(Loid)S砷和铬的生物磁铁矿，以有效地将离子锁定到带有河流潜流带沉积物的磁铁矿中。这将旨在制定修复对世界各地数百万人构成严重健康威胁的受污染土地和水的战略。

Biogenic magnetite (Fe3O4) nanoparticles are mixed Fe(II)/Fe(III) minerals produced in the environment by Fe(III)-reducing bacteria with small size (<50 nm), a highly reactive Fe(II) surface layer and an organic coating. All of these properties make biogenic magnetite suitable for potential remediation strategies. Fe(II)-oxidizing bacteria are not ordinarily found associated with the formation of magnetite, instead Fe(III) oxyhydroxides such as goethite (alpha-FeOOH) and ferrihydrite (simplified as Fe(OH)3) are more commonly produced. Recent work by our group has shown that the presence of small amounts of magnetite nanoparticles during microbial Fe(II) oxidation can act as nucleation sites and lead to the formation of additional magnetite. It is not known if this new magnetite consists of spontaneously created nuclei or larger particles growing from the added nucleation sites. To apply microbially derived biogenic magnetite for remediation purposes, the mechanism of magnetite formation and its reactivity need to be known. We therefore propose experiments with Fe(II)-oxidizing bacteria to study the impact of nucleation sites in detail, with a number of variables including specific surface area and concentration of nucleation sites chosen to observe changes in the rate of magnetite formation and in the final mineral phases produced. Additionally, we propose batch experiments to test the biogenic magnetite for remediation of the toxic metal(loid)s arsenic and chromium to effectively lock-in the ions into the magnetite with sediment from the hyporheic zone of a river. This will be aimed towards developing strategies for remediation of contaminated land and water that pose serious health risks to millions of people around the world.