Department of Hydrology, University of Bayreuth, Bayreuth Center for Ecology and Environmental Research (BayCEER), Universitaetsstrasse 30, 95440 Bayreuth, Germany.
Southern Cross GeoScience, Southern Cross University, Lismore New South Wales 2480, Australia.
Environ Sci Technol. 2021 Apr 20;55(8):4954-4963. doi: 10.1021/acs.est.0c08660. Epub 2021 Mar 12.
The environmental mobility of antimony (Sb) is controlled by interactions with iron (Fe) oxides, such as ferrihydrite. Under near-neutral pH conditions, Fe(II) catalyzes the transformation of ferrihydrite to more stable phases, thereby potentially altering the partitioning and speciation of associated Sb. Although largely unexplored, Sb itself may also influence ferrihydrite transformation pathways. Here, we investigated the impact of Sb on the Fe(II)-induced transformation of ferrihydrite at pH 7 across a range of Sb(V) loadings (Sb:Fe(III) molar ratios of 0, 0.003, 0.016, and 0.08). At low and medium Sb loadings, Fe(II) induced rapid transformation of ferrihydrite to goethite, with some lepidocrocite forming as an intermediate phase. In contrast, the highest Sb:Fe(III) ratio inhibited lepidocrocite formation, decreased the extent of goethite formation, and instead resulted in substantial formation of feroxyhyte, a rarely reported FeOOH polymorph. At all Sb loadings, the transformation of ferrihydrite was paralleled by a decrease in aqueous and phosphate-extractable Sb concentrations. Extended X-ray absorption fine structure spectroscopy showed that this Sb immobilization was attributable to incorporation of Sb into Fe(III) octahedral sites of the neo-formed minerals. Our results suggest that Fe oxide transformation pathways in Sb-contaminated systems may strongly differ from the well-known pathways under Sb-free conditions.
锑 (Sb) 的环境迁移性受与铁 (Fe) 氧化物（如水铁矿）相互作用的控制。在近中性 pH 条件下，Fe(II) 催化水铁矿向更稳定的相转化，从而可能改变相关 Sb 的分配和形态。尽管这方面尚未得到充分研究，但 Sb 本身也可能影响水铁矿的转化途径。在这里，我们研究了 Sb 对 pH 7 下不同 Sb(V) 负载（Sb:Fe(III)摩尔比为 0、0.003、0.016 和 0.08）条件下 Fe(II) 诱导的水铁矿转化的影响。在低和中 Sb 负载下，Fe(II) 诱导水铁矿快速转化为针铁矿，其中一些形成了纤铁矿作为中间相。相比之下，最高的 Sb:Fe(III) 比抑制了纤铁矿的形成，降低了针铁矿的形成程度，反而导致了大量的羟高铁石的形成，这是一种很少报道的 FeOOH 多晶型物。在所有 Sb 负载下，水铁矿的转化伴随着水溶液和磷酸盐可提取 Sb 浓度的降低。扩展 X 射线吸收精细结构光谱表明，这种 Sb 固定归因于 Sb 掺入新形成的矿物的 Fe(III) 八面体位置。我们的结果表明，Sb 污染系统中的 Fe 氧化物转化途径可能与 Sb 无的情况下的已知途径有很大的不同。
