Schwertmannite, ubiquitously found in iron and sulfate-rich acid mine drainage, is generated via biological oxidation of ferrous ions by Acidithiobacillus ferrooxidans (A. ferrooxidans). However, little information on the mechanisms of biogenic schwertmannite formation and crystal growth is available. This study deliberately investigated the relationships among mineral morphology, solution chemistry, and phase transformation of schwertmannite in A. ferrooxidans-containing ferrous sulfate solutions. The formation of schwertmannite could be divided into three stages. In the first nucleation stage, crystallites are presented as nonaggregative or aggregative forms via a successive polymerization process. In the second stage, ellipsoidal aggregates, which are identified as ferrihydrite and/or schwertmannite, are formed. In the third stage, needles appear on the surface of ellipsoidal aggregates, which is caused by the phase transformation of ferrihydrite or schwertmannite to lepidocrocite and goethite through a Fe²⁺ (aq) catalysis-driven pathway. After three stages, a typical characteristic “hedgehog” morphology finally appears. In addition, A. ferrooxidans could significantly speed up the mineral transformation. Solution pH affects the morphology of schwertmannite by acid leaching. The experimental results also reveal that the formation of schwertmannite depend on the content of hydroxyl complexes or the transformation of the monomers to polymers, which are greatly affected by the solution pH.

中文翻译：

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羟基，Fe ²⁺和酸性氧化亚铁细菌共同确定富含硫酸盐的酸性环境中Schwertmannite的晶体生长和形态

在富含铁和硫酸盐的酸性矿山排水中普遍发现的Schwertmannite，是通过酸性氧化硫硫杆菌（A. ferrooxidans）对亚铁离子进行生物氧化而生成的。然而，关于生物型斯沃特曼石形成和晶体生长机理的信息很少。这项研究专门研究了铁形态拟南芥中的矿物形态，溶液化学和schwertmannite相变之间的关系。含硫酸亚铁溶液。schwertmannite的形成可分为三个阶段。在第一个成核阶段，微晶通过连续的聚合过程以非聚集或聚集形式存在。在第二阶段中，形成了椭圆形聚集体，这些聚集体被确定为三水铝石和/或schwertmannite。在第三阶段，针状体出现在椭球形聚集体的表面，这是由于铁水合物或schwertmannite通过Fe ²⁺（aq）催化驱动的路径相转变为lepidocrocite和针铁矿而引起的。经过三个阶段，终于出现了典型的“刺猬”形态。此外，A。ferrooxidans可以大大加快矿物转化的速度。溶液的pH值会通过酸浸影响到Schwertmannite的形态。实验结果还表明，Schwertmannite的形成取决于羟基络合物的含量或单体向聚合物的转化，这受溶液pH值的影响很大。