Heated Montmorillonite: Structure, Reactivity, and Dissolution
Heated Montmorillonite: Structure, Reactivity, and Dissolution
复制标题
加热蒙脱石：结构、反应性和溶解
DOI：
10.1007/978-94-017-9939-3_15
复制
发表时间：
2015
影响因子：
11.4
通讯作者：
J. Skibsted
中科院分区：
文献类型：
--
作者：
N. Garg;J. Skibsted
主要的1：1粘土高岭石的脱羟基形式，称为偏高岭土，已经在其结构和反应性方面进行了广泛的研究。然而，在这方面缺乏关于丰富的2：1粘土蒙脱石脱羟基的详细信息。用固体~（29）Si MAS NMR对三种不同温度焙烧的蒙脱石进行了表征。脱羟基作用（600 - 800 °C）导致SiO 4四面体逐渐变形，随后在较高温度下惰性稳定相结晶。结构上纯的蒙脱石，SAZ-2，在两个不同的温度下煅烧的溶解动力学被发现是在很好的协议，其火山灰反应性建立在早期的研究。还发现，在800 °C的最佳煅烧温度下煅烧的SAz-2在溶解一天后在0.1 M NaOH溶液中经历不一致溶解，达到3.7的Si/Al摩尔比。它已被重申，脱羟基化的程度和结构相的类型（Q3/Q4）有一个显着的影响煅烧蒙脱土的反应性。通过固态NMR清楚地识别惰性相和反应位点可能不仅对蒙脱石而且对其他煅烧粘土的利用具有重要意义。
The dehydroxylated form of the principal 1:1 clay, kaolinite, known as metakaolin, has been widely studied in terms of its structure and reactivity. However, detailed information on the dehydroxylation of the abundant 2:1 clay, montmorillonite, is lacking in this respect. Three montmorillonites, calcined at various temperatures have been characterized by solid-state 29Si MAS NMR. The dehydroxylation (600 – 800 °C) results in progressive distortion of the SiO4 tetrahedra, followed by crystallization of inert, stable phases at higher temperatures. The dissolution kinetics of a structurally pure montmorillonite, SAz-2, calcined at two different temperatures are found to be in good agreement with its pozzolanic reactivity established in an earlier study. It is also found that SAz-2, calcined at its optimum calcination temperature of 800 °C, undergoes incongruent dissolution reaching a molar Si/Al ratio of 3.7 in a 0.1 M NaOH solution after one day of dissolution. It has been reaffirmed that both the degree of dehydroxylation and the type of structural phases (Q3/Q4) have a significant impact on the reactivity of the calcined montmorillonite. The clear identification of inert phases and reactive sites by solid-state NMR may have major implications in the utilization of not only montmorillonites but also other calcined clays.