<b>Phosphate effects on the transformation of Sb(V)-</b><b>bearing </b><b>ferrihydrite under microbial iron- and sulfate-reducing conditions</b>

Antimony (Sb) is a toxic metalloid that poses environmental risks in terrestrial and aquatic systems. Immobilization of the Sb(V) oxyanion, Sb(OH)₆^-, by ferric oxides can be influenced by competitive adsorption from other anions such as phosphate (PO₄^3-). This study investigated the unknown effect of PO₄^3- on Sb(V) behavior under Fe(III) and sulfate-reducing conditions. Anoxic reactors that contained Sb(V)-bearing ferrihydrite (Fh), varying PO₄^3- concentrations (0, 0.2, and 2 mM), and sulfate, were inoculated with a microbial community sourced from Sb-contaminated soil. Additionally, abiotic reactors with either Sb(V)-adsorbed to or Sb(V)-coprecipitated with Fh and different PO­₄^3- loadings (0–100 mM) were created to investigate the competitive adsorption mechanisms in the absence of microbial activity. Results from the abiotic reactors suggest that Sb(V) is likely incorporated into the Fh structure, with only minor amounts remaining surface-bound and extractable by PO₄^3-. In the biotic reactors, Fe(III) and sulfate reduction were more extensive in the presence of PO₄^3-. At 0.2 mM PO₄^3-, microbial activity transformed Fh into siderite and led to the complete reduction of Sb(V) to Sb(III) as stibnite (Sb₂S₃). At 2 mM PO₄³, the greater coverage by PO­₄^3- stabilized Fh and decreased the extent of both Fe(III) and Sb(V) reduction, and shifted the reduced products to mackinawite and Sb(III) adsorbed onto Fh, in addition to stibnite formation. This study demonstrates that while PO­₄^3- may not directly compete with Sb(V) for sorption sites, it can influence Sb mobility in Fe(III)- and sulfate-reducing environments by altering the mineralization pathways.

锑（Sb）是一种有毒准金属，可对陆地与水生生态系统造成环境风险。三价铁氧化物对含氧阴离子Sb(OH)₆⁻形态的五价锑（Sb(V)）的固定作用，可能受到磷酸根（PO₄³⁻）等其他阴离子的竞争吸附影响。本研究针对三价铁（Fe(III)）与硫酸盐还原环境中，PO₄³⁻对Sb(V)行为的未知影响展开探究。本研究设置厌氧反应器体系，体系内含负载Sb(V)的水铁矿（ferrihydrite, 下文简称Fh）、梯度浓度PO₄³⁻（0、0.2及2 mM）与硫酸盐，接种源自锑污染土壤的微生物群落。此外，构建两类非生物反应器：其一为Sb(V)吸附于Fh表面，其二为Sb(V)与Fh共沉淀，两类反应器均设置0~100 mM的不同PO₄³⁻负载量，用于解析无微生物活动下的竞争吸附机制。非生物反应器的实验结果显示，Sb(V)大概率嵌入Fh的晶体结构中，仅少量以表面结合态留存，且可被PO₄³⁻提取。在生物反应器中，PO₄³⁻存在时Fe(III)与硫酸盐的还原程度更为显著。当PO₄³⁻浓度为0.2 mM时，微生物活动将Fh转化为菱铁矿（siderite），并将Sb(V)完全还原为三价锑（Sb(III)），以辉锑矿（Sb₂S₃）的形式析出。当PO₄³⁻浓度为2 mM时，更高的PO₄³⁻覆盖度稳定了Fh晶体，降低了Fe(III)与Sb(V)的还原程度，除辉锑矿生成外，还原产物还转变为马基诺矿（mackinawite）与吸附于Fh表面的Sb(III)。本研究证实，尽管PO₄³⁻或许无法直接与Sb(V)竞争吸附位点，但可通过改变矿化途径，影响Fe(III)与硫酸盐还原环境中Sb的迁移性。

搜集汇总

背景与挑战

背景概述

该数据集研究了磷酸盐对含锑(V)水铁矿在微生物铁还原和硫酸盐还原条件下转化的影响。实验表明，磷酸盐不直接与锑(V)竞争吸附位点，但能通过改变矿物转化途径（如水铁矿转化为菱铁矿或马基诺矿）来影响锑的还原和迁移性，低浓度磷酸盐促进锑(V)完全还原为辉锑矿，而高浓度则稳定水铁矿并减少还原程度。