In this article, we provide a critical review on the occurrence, formation, structure and stability of schwertmannite – an enigmatic Fe(III) oxyhydroxy-sulfate mineral that is of widespread interest in the soil science, environmental geochemistry, hydrometallurgy and wastewater fields. We also review interactions between schwertmannite and selected, environmentally relevant oxyanions (arsenate, phosphate, antimonate, selenate, chromate, and molybdate). Schwertmannite is one of the most common minerals to form via direct precipitation of iron in acid sulfate waters at pH 2 – 4. As such, it has been found to occur in systems that are affected by acid mine drainage, acid sulfate soils, natural acid rock drainage, and hydrometallurgical settings involving oxidation of iron-sulfide minerals. Despite its official recognition as a new mineral almost 30 years ago, schwertmannite’s poor crystallinity, fine particle size, variable composition and metastability have constrained our ability to conclusively resolve its crystal structure, possibly polyphasic nature, and solubility/stability. Nevertheless, since the early 1990’s, there has been a steadily-growing body of literature showing that, in acid-sulfate systems, schwertmannite strongly impacts iron and sulfur cycling, acidity dynamics, and electron flow. In addition, interactions with schwertmannite also strongly influence the mobility and fate of co-associated oxyanionic species. In parallel, many oxyanions have themselves been found to also exert a powerful control on schwertmannite’s geochemical behavior and mineralogical stability. Schwertmannite-oxyanion interactions occur via adsorption to the schwertmannite surface, anionic exchange with sulfate in the schwertmannite tunnel structure, and co-precipitation by substitution for either structural sulfate or Fe(III) during schwertmannite formation. This array of distinct sorption mechanisms results in oxyanions being able to both stabilize and conversely destabilize schwertmannite. This distinction appears to reflect an interplay of kinetic and thermodynamic constraints, which depend heavily on the specific oxyanion, its concentration (i.e. level of loading on/in schwertmannite), and other background geochemical conditions (e.g. pH and presence of other ions). Resolving these complex interactions and their importance in controlling schwertmannite occurrence and stability represents a challenge for future research.

在本文中，我们对施韦特曼铁矿的发生、形成、结构和稳定性进行了批判性评论，这是一种在土壤科学、环境地球化学、湿法冶金和废水领域具有广泛兴趣的神秘 Fe(III) 羟基硫酸盐矿物。我们还回顾了施维特曼石与选定的、与环境相关的氧阴离子（砷酸盐、磷酸盐、锑酸盐、硒酸盐、铬酸盐和钼酸盐）之间的相互作用。Schwertmannite 是最常见的矿物质之一，通过在 pH 值为 2 – 4 的酸性硫酸盐水中直接沉淀铁而形成。因此，已发现它存在于受酸性矿山排水、酸性硫酸盐土壤、天然酸影响的系统中。岩石排水和涉及硫化铁矿物氧化的湿法冶金环境。尽管近 30 年前正式承认其为新矿物，但施维特曼石的结晶度差、粒度细、成分多变和亚稳定性限制了我们最终解析其晶体结构、可能的多相性质和溶解度/稳定性的能力。尽管如此，自 1990 年代初期以来，越来越多的文献表明，在酸-硫酸盐体系中，施维特曼石强烈影响铁和硫循环、酸度动力学和电子流。此外，与施维特曼石的相互作用也强烈影响相关含氧阴离子物质的迁移率和命运。同时，已发现许多氧阴离子本身也对施维特曼石的地球化学行为和矿物学稳定性施加强大的控制。Schwertmannite-oxyanion 相互作用通过对 Schwertmannite 表面的吸附、在 Schwertmannite 隧道结构中与硫酸盐的阴离子交换以及在 Schwertmannite 形成过程中取代结构硫酸盐或 Fe(III) 的共沉淀发生。这一系列不同的吸附机制导致氧阴离子能够稳定和相反地破坏施韦特曼石的稳定。这种区别似乎反映了动力学和热力学约束的相互作用，这在很大程度上取决于特定的氧阴离子、其浓度（即施威曼石上/中的负载水平）和其他背景地球化学条件（例如 pH 值和其他离子的存在）。解决这些复杂的相互作用及其在控制施维特曼石的发生和稳定性方面的重要性代表了未来研究的挑战。