Understanding the role of Zn2+ in surfactant-free layered silicate delamination: Exfoliation of magadiite
Understanding the role of Zn2+ in surfactant-free layered silicate delamination: Exfoliation of magadiite
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DOI：
10.1016/j.micromeso.2019.03.048
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发表时间：
2019-07
影响因子：
5.2
通讯作者：
A. Okrut;Nicolás A. Grosso‐Giordano;Christian Schöttle;S. Zones;Alexander Katz
中科院分区：
文献类型：
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作者：
A. Okrut;Nicolás A. Grosso‐Giordano;Christian Schöttle;S. Zones;Alexander Katz
我们研究了Zn 2+处理对层状硅酸盐麦羟硅钠石剥离的影响，作为模型系统，以更好地理解锌在无表面活性剂沸石剥离中的作用。采用Zn（NO3）2溶液对麦羟硅钠石和球磨麦羟硅钠石样品进行剥离处理，并通过粉末X射线衍射、氮气物理吸附、高角环形暗场扫描透射电子显微镜和红外光谱对所得材料进行表征。Zn ~（2+）处理使麦羟硅钠石的比表面积增加了40%，而Zn ~（2+）处理使球磨麦羟硅钠石的比表面积增加了109%。酸洗去除Zn（O）x（OH）y胶体并进一步增加外表面积，导致Zn 2+处理和酸洗后的麦羟硅钠石的总表面积增加150%，并且Zn 2+处理和酸洗后的球磨麦羟硅钠石的总表面积增加182%，通过暴露在Zn 2+处理后由于孔堵塞而不可接近的表面积。我们提出了一种剥离机制来解释这些表面积的增加，这涉及到Zn（O）x（OH）y胶体的生长和迫使层选择性地在晶界分开。球磨不仅使现有的晶界更容易接近，而且还产生新的晶界，从而导致更有效的剥离。
We investigated the effect of Zn2+treatment on the exfoliation of layered silicate magadiite, as a model system, to better understand the role of zinc in surfactant-free zeolite exfoliation. Samples of magadiite and ball-milled magadiite were exfoliated via treatment with aqueous Zn(NO3)2solution, and the resulting materials were characterized via powder X-ray diffraction, nitrogen physisorption, high-angle annular dark-field scanning transmission electron microscopy, and infrared spectroscopy. Zn2+treatment of magadiite increases its external surface area by 40%, while Zn2+treatment of ball-milled magadiite increases its external surface area by 109%. Acid-washing removes Zn(O)x(OH)ycolloids and further increases external surface area, leading to a total surface area increase of 150% for magadiite after Zn2+treatment and acid-washing, and 182% for ball-milled magadiite after Zn2+treatment and acid-washing, by exposing surface area that was not accessible after Zn2+treatment due to pore blocking. We propose a mechanism of exfoliation to account for these surface-area increases, which involves the Zn(O)x(OH)ycolloids growing and forcing layers apart selectively at the grain boundaries. Ball milling not only makes existing grain boundaries more accessible, but it also creates new grain boundaries, resulting in more efficient exfoliation.