Preparation of Fe(II)-montmorillonite by reduction of Fe(III)-montmorillonite with ascorbic acid
Preparation of Fe(II)-montmorillonite by reduction of Fe(III)-montmorillonite with ascorbic acid
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DOI：
10.1016/j.clay.2008.02.005
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发表时间：
2008-12
影响因子：
5.6
通讯作者：
J. Manjanna
中科院分区：
文献类型：
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作者：
J. Manjanna
本文介绍了一种以铁（III）月为原料制备铁（II）蒙脱土（月）的简便新方法。用抗坏血酸（维生素C）溶液在70℃氩气中处理Fe(III)-mont ~12 h。所有吸附的铁（III）都被还原成Fe(II)-mont。在起始材料Fe(III)-月中存在任何伴生的Fe-氧化物相，都有利于达到化学计量的Fe(II)-月。从新鲜制备的Fe(II)-mont中提取的铁的Fe2+/ fetotal比接近统一。如果原料中有足够的铁（III），则在1 M NH4Cl中提取的铁总量相当于母蒙脱土（Kunipia F蒙脱土）的铁（II）阳离子交换容量。相对湿度（RH）为40%时，基间距为14.7 Å，为典型的二价层间阳离子蒙脱土。FTIR光谱显示粘土矿物基本结构无明显变化。通过Mössbauer室温（RT）光谱进一步证实了该结构。因此，本文所述的Fe(II)-mont制备方法在大气环境条件下非常方便地进行常规制备，也可用于大量制备。同时也证明了固态制备Fe(II)-mont的可行性。在部分脱氧条件下，证明了Fe(II)-mont在水中分散的稳定性。在室温和65℃条件下，层间Fe（II）离子在47天内氧化约30%和70%。因此，层间的Fe（II）离子逐渐被氧化（即，不像预期的那样迅速）。为了长期保存铁（II）月样品，必须保持脱氧，低RH（<40%）的条件下，不暴露在高温下。
A new and convenient method is described here to prepare Fe(II)-montmorillonite (mont) using Fe(III)-mont as the starting material. Fe(III)-mont was treated with ascorbic acid (vitamin C) solution at 70 °C for ~12 h in Ar atmosphere. All of the adsorbed iron(III) was reduced to form Fe(II)-mont. The presence of any associated Fe-oxide phase in the starting material, Fe(III)-mont, was rather advantageous to reach stoichiometric Fe(II)-mont. The Fe2+/Fetotalratio of the iron extracted from freshly prepared Fe(II)-mont was found to be close to unity. The total amount of iron extracted in 1 M NH4Cl was equivalent to the cation exchange capacity of the parent montmorillonite (Kunipia F montmorillonite) in terms of Fe(II), provided there was sufficient iron(III) in the starting material. The basal spacing at a relative humidity (RH) of 40% was 14.7 Å, typical of montmorillonite with divalent interlayer cations. FTIR spectra showed no significant changes in the basic clay mineral structure. The structure was further proved by Mössbauer spectra at room temperature (RT). Thus Fe(II)-mont preparation as described here was found to be highly convenient for routine preparation in the ambient atmospheric condition, also for large quantities. The feasibility of solid-state preparation of Fe(II)-mont was also demonstrated. The stability of Fe(II)-mont was proved in dispersion in water under partially deoxygenated condition. There was about 30% and 70% oxidation of interlayer Fe(II) ions in about 47 days at RT and 65 °C. Thus, the interlayer Fe(II) ions were gradually oxidized (i.e., not rapidly, as anticipated). For long-time preservation of the Fe(II)-mont sample, it is essential to keep deoxygenated, low RH (<40%) conditions and without exposing to elevated temperatures.