Competitive Fe(II)–Zn(II) Uptake on a Synthetic Montmorillonite

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• 作者：Daniela Soltermann ; Maria Marques Fernandes ; Bart Baeyens ; Jocelyne Miehé-Brendlé ; Rainer D?hn
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：January 7, 2014
• 年：2014
• 卷：48
• 期：1
• 页码：190-198
• 全文大小：426K
• ISSN：1520-5851

文摘

The interaction of Fe(II) with clay minerals is of particular relevance in global geochemical processes controlling metal and nutrient cycles and the fate of contaminants. In this context, the influence of competitive sorption effects between Fe(II) and other relevant transition metals on their uptake characteristics and mobility remains an important issue. Macroscopic sorption experiments combined with surface complexation modeling and extended X-ray absorption fine structure (EXAFS) spectroscopy were applied to elucidate competitive sorption processes between divalent Fe and Zn at the clay mineral鈥搘ater interface. Sorption isotherms were measured on a synthetic iron-free montmorillonite (IFM) under anoxic conditions (O₂ <0.1 ppm) for the combinations of Zn(II)/Fe(II) and Fe(II)/Zn(II), where the former metal in each pair represents the trace metal (<10^鈥? M) and the latter the competing metal at higher concentrations (10^鈥? to 10^鈥? M). Results of the batch sorption and EXAFS measurements indicated that Fe(II) is competing with trace Zn(II) for the same type of strong sites if Fe(II) is present in excess, whereas no competition between trace Fe(II) and Zn(II) was observed if Zn(II) is present at high concentrations. The noncompetitive behavior suggests the existence of sorption sites which have a higher affinity for Fe(III), where surface-induced oxidation of the sorbed Fe(II) to Fe(III) occurred, and which are not accessible for Zn(II). The understanding of this competitive uptake mechanism between Fe(II) and Zn(II) is of great importance to assess the bioavailability and mobility of transition metals in the natural environment.