Jungcharoen Phoomipat, Marsac Rémi, Choueikani Fadi, Masson Delphine, Pédrot Mathieu
Univ Rennes, CNRS, Géosciences Rennes - UMR 6118 F-35000 Rennes France
Department of Environmental Engineering, Faculty of Engineering and Research Center for Environmental and Hazardous Substance Management, Khon Kaen University Khon Kaen 40002 Thailand.
Nanoscale Adv. 2023 Jul 19;5(16):4213-4223. doi: 10.1039/d3na00240c. eCollection 2023 Aug 8.
Magnetite, a ubiquitous mineral in natural systems, is of high interest for a variety of applications including environmental remediation, medicine, and catalysis. If the transformation of magnetite to maghemite through the oxidation of Fe has been well documented, mechanisms involving dissolution processes of Fe in aqueous solutions have been overlooked. Here, the effect of dissolved organic ligands (EDTA (ethylenediaminetetraacetic acid), acetic, lactic and citric acids) on Fe solubility and on the stoichiometry (Fe(ii)/Fe(iii)) of magnetite-maghemite nanoparticles (∼10 nm) was investigated. These ligands were chosen because of their environmental relevance and because they are widely used as coating agents for nanotechnology applications. Results show an insignificant effect of 2 organic ligands (acetate and lactate) on the dissolution of Fe. By contrast, citrate and EDTA enhanced Fe solubility because of the formation of dissolved Fe(ii)- and Fe(iii)-ligand complexes. Both ligands selectively bound Fe(ii) over Fe(iii), but EDTA was much more selective than citrate. The combined effects of oxidation and H- and ligand-promoted dissolution of Fe from magnetite were predicted using a magnetite-maghemite solid solution model, accounting for the formation of dissolved Fe(ii)- and Fe(iii)-ligand complexes. Therefore, these results show that citrate and EDTA (i) enhance Fe solubility in the presence of magnetite nanoparticles and (ii) modify magnetite stoichiometry, which affects its environmental behavior and its properties for nanotechnology applications.
磁铁矿是自然系统中普遍存在的一种矿物，在包括环境修复、医学和催化等多种应用中备受关注。虽然磁铁矿通过铁的氧化转化为磁赤铁矿的过程已有充分记录，但涉及铁在水溶液中溶解过程的机制却被忽视了。在此，研究了溶解有机配体（乙二胺四乙酸（EDTA）、乙酸、乳酸和柠檬酸）对铁溶解度以及磁铁矿 - 磁赤铁矿纳米颗粒（约10纳米）化学计量比（Fe(ii)/Fe(iii)）的影响。选择这些配体是因为它们与环境相关，且被广泛用作纳米技术应用的包覆剂。结果表明，两种有机配体（乙酸盐和乳酸盐）对铁的溶解影响不显著。相比之下，柠檬酸盐和EDTA由于形成了溶解的Fe(ii) - 和Fe(iii) - 配体络合物而提高了铁的溶解度。两种配体对Fe(ii)的选择性结合都高于Fe(iii)，但EDTA比柠檬酸盐的选择性要强得多。利用磁铁矿 - 磁赤铁矿固溶体模型预测了铁从磁铁矿中氧化以及H - 和配体促进溶解的综合影响，该模型考虑了溶解的Fe(ii) - 和Fe(iii) - 配体络合物的形成。因此，这些结果表明，柠檬酸盐和EDTA（i）在存在磁铁矿纳米颗粒的情况下提高了铁的溶解度，并且（ii）改变了磁铁矿的化学计量比，这会影响其环境行为及其在纳米技术应用中的性质。
