Bayer Timm, Wei Ran, Kappler Andreas, Byrne James M
Geomicrobiology Group, Department of Geoscience, University of Tuebingen, Schnarrenbergstrasse 94-96, 72076 Tuebingen, Germany.
Environmental Systems Analysis, Department of Geoscience, University of Tuebingen, Schnarrenbergstrasse 94-96, 72076 Tuebingen, Germany.
ACS Earth Space Chem. 2023 Oct 9;7(10):1837-1847. doi: 10.1021/acsearthspacechem.2c00394. eCollection 2023 Oct 19.
Heavy metal pollutants in the environment are of global concern due to their risk of contaminating drinking water and food supplies. Removal of these metals can be achieved by adsorption to mixed-valent magnetite nanoparticles (MNPs) due to their high surface area, reactivity, and ability for magnetic recovery. The adsorption capacity and overall efficiency of MNPs are influenced by redox state as well as surface charge, the latter of which is directly related to solution pH. However, the influence of microbial redox cycling of iron (Fe) in magnetite alongside the change of pH on the metal adsorption process by MNPs remains an open question. Here we investigated adsorption of Cd and Cu by MNPs at different pH values that were modified by microbial Fe(II) oxidation or Fe(III) reduction. We found that the maximum adsorption capacity increased with pH for Cd from 256 μmol/g Fe at pH 5.0 to 478 μmol/g Fe at pH 7.3 and for Cu from 229 μmol/g Fe at pH 5.0 to 274 μmol/g Fe at pH 5.5. Microbially reduced MNPs exhibited the greatest adsorption for both Cu and Cd (632 μmol/g Fe at pH 7.3 for Cd and 530 μmol/g Fe at pH 5.5 for Cu). Magnetite oxidation also enhanced adsorption of Cu but inhibited Cd. Our results show that microbial modification of MNPs has an important impact on the (im-)mobilization of aqueous contaminations like Cu and Cd and that a change in stoichiometry of the MNPs can have a greater influence than a change of pH.
环境中的重金属污染物因其污染饮用水和食品供应的风险而受到全球关注。由于混合价态磁铁矿纳米颗粒（MNP）具有高比表面积、反应活性和磁回收能力，通过吸附这些金属可实现其去除。MNP的吸附容量和整体效率受氧化还原状态以及表面电荷的影响，而表面电荷与溶液pH值直接相关。然而，磁铁矿中铁（Fe）的微生物氧化还原循环以及pH值变化对MNP金属吸附过程的影响仍是一个悬而未决的问题。在此，我们研究了在微生物Fe（II）氧化或Fe（III）还原作用下不同pH值时MNP对Cd和Cu的吸附情况。我们发现，对于Cd，最大吸附容量随pH值升高而增加，从pH 5.0时的256 μmol/g Fe增至pH 7.3时的478 μmol/g Fe；对于Cu，从pH 5.0时的229 μmol/g Fe增至pH 5.5时的274 μmol/g Fe。经微生物还原的MNP对Cu和Cd的吸附量最大（pH 7.3时对Cd为632 μmol/g Fe，pH 5.5时对Cu为530 μmol/g Fe）。磁铁矿氧化也增强了对Cu的吸附，但抑制了对Cd的吸附。我们的结果表明，MNP的微生物改性对Cu和Cd等水体污染物的（去）迁移具有重要影响，并且MNP化学计量比的变化可能比pH值变化产生更大的影响。
