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（Fe 3 O 4）纳米颗粒是由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（<50 nm）、高活性Fe（II）表面层和有机涂层。所有这些特性使得生物成因磁铁矿适合于潜在的修复策略。铁（II）氧化细菌通常不与磁铁矿的形成有关，而是铁（III）羟基氧化物，如针铁矿（α-FeOOH）和水铁矿（简化为Fe（OH）3）更常见。我们小组最近的工作表明，在微生物Fe（II）氧化过程中少量磁铁矿纳米颗粒的存在可以作为成核位点，并导致形成额外的磁铁矿。目前还不知道这种新的磁铁矿是由自发产生的核组成，还是由从增加的成核位点生长的较大颗粒组成。为了将微生物来源的生物磁铁矿用于修复目的，需要了解磁铁矿的形成机制及其反应性。因此，我们建议实验与Fe（II）氧化细菌详细研究成核位点的影响，与一些变量，包括比表面积和浓度的成核位点选择观察磁铁矿形成的速率和最终矿物相的变化。此外，我们提出了批量实验来测试生物磁铁矿的有毒金属（loid）的砷和铬的修复，以有效地锁定在磁铁矿的离子与沉积物从河流的潜流区。这将旨在制定战略，对全世界数百万人的健康构成严重威胁的受污染土地和水进行补救。

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.