The Mobility of Mo during Microbially Mediated Ferrihydrite Phase Transformation

• Published in: Environmental science & technology 2024-12, Vol.58 (49), p.21653-21661
• Main Authors: Zhang, Jing, Zhu, Mengqiang, Lloyd, Jonathan R., Shaw, Samuel, Coker, Victoria S., Xie, Jinxin, Wen, Ke, Lee, Sungsik, Goût, Thomas L., Hao, Jingyue, Ma, Lin, Hu, Yandi, Pan, Bo
• Format: Article
• Language: English
• Subjects: Adsorption; Biogeochemical Cycling; environmental science; Ferric Compounds - chemistry; ferrihydrite; Genetic transformation; Geobacter - metabolism; Geobacter sulfurreducens; Goethite; Iron; iron oxyhydroxides; Magnetite; Molybdenum; Molybdenum - chemistry; Nanoparticles; Nutrient concentrations; Oxidation-Reduction; phase transition; Phase transitions; Siderite; toxicity
• ISSN: 0013-936X; 1520-5851; 1520-5851
• DOI: 10.1021/acs.est.4c09144

Molybdenum (Mo) is an essential nutrient for almost all organisms. However, at high concentrations, it can be toxic to animals and plants. This study investigated the interactions of Mo­(VI) with iron oxyhydroxides during ferrihydrite bioreduction in the presence of Fe­(III)-reducing Geobacter sulfurreducens. Here, we showed that Mo concentration controlled ferrihydrite phase transformation, leading to Mo release. With the biotic reduction of ferrihydrite and Fe­(II) production, Mo­(VI) reduction and Mo­(IV)­O2 formation were observed for the first time, which further immobilized Mo after surface adsorption of Mo­(VI). At low Mo levels (Mo/Fe molar ratios of 1–2%), sufficient Fe­(II) adsorption onto ferrihydrite resulted in its transformation into magnetite nanoparticles (>80%, ∼25 nm), which catalyzed the reduction of Mo­(VI) to form Mo­(IV)­O2 and immobilized Mo. Contrastingly, at high Mo concentrations (Mo/Fe molar ratios of 5–10%), Mo­(VI)­O4 2– adsorption onto ferrihydrite limited Fe­(II) adsorption; subsequently, less magnetite (15 and 100 nm, respectively) and siderite (∼20–30%, width and length >100 and 200 nm, respectively) with larger particle sizes formed instead, causing Mo­(VI) release due to lower Mo adsorption. This study provides a comprehensive understanding of the interaction mechanisms among Geobacter sulfurreducens, Mo­(VI), and iron oxyhydroxides, enabling predictions and controls of long-term Mo mobility and Fe mineral transformation under a variety of biogeochemical scenarios.