Self-assembly Processes in Hydrated Montmorillonite by FTIR Investigations.

Maria Teresa Caccamo,Letterio Mavilia,Salvatore Magazù,Giuseppe Mavilia,Domenico Lombardo

doi:10.3390/ma13051100

Abstract

Experimental findings obtained by FTIR and Raman spectroscopies on montmorillonite-water mixtures at three concentration values are presented. To get some insight into the hydrogen bond network of water within the montmorillonite network, FTIR and Raman spectra have been collected as a function of time and then analyzed following two complementary approaches: An analysis of the intramolecular OH stretching mode in the spectral range of 2700–3900 cm−1 in terms of two Gaussian components, and an analysis of the same OH stretching mode by wavelet cross-correlation. The FTIR and Raman investigations have been carried as a function of time for a montmorillonite-water weight composition (wt%) of 20–80%, 25–75%, and 35–65%, until the dehydrated state where the samples appear as a homogeneous rigid layer of clay. In particular, for both the FTIR and Raman spectra, the decomposition of the OH stretching band into a “closed” and an “open” contribution and the spectral wavelet analysis allow us to extract quantitative information on the time behavior of the system water content. It emerges that, the total water contribution inside the montmorillonite structure decreases as a function of time. However, the relative weight of the ordered water contribution diminishes more rapidly while the relative weight of the disordered water contribution increases, indicating that a residual water content, characterized by a highly structural disorder, rests entrapped in the montmorillonite layer structure for a longer time. From the present study, it can be inferred that the montmorillonite dehydration process promotes the layer self-assembly.

Highlights

Among various silico-aluminate precursors used for the preparation of geopolymers, we can certainly mention clays and in particular those characterized by cation exchange, such as montmorillonite
There are two types of phyllosilicates: Those having a 1:1 ratio, such as kaolin, in which each with a 2:1 ratio, such in which a single is formed bythe an phyllosilicates octahedral layer lamella is made up as bymontmorillonite, only two layers and interposed between two tetrahedral layers and, there is the presence of weak Van with a 2:1 ratio, such as montmorillonite, in which a single lamella is formed by an octahedral layerder
Pure powder montmorillonite purchased from Merck (Milano, Italy, surface area 250 m2 /g) and double distilled water were employed to prepare the samples

Summary

Introduction

Among various silico-aluminate precursors used for the preparation of geopolymers, we can certainly mention clays and in particular those characterized by cation exchange, such as montmorillonite. There are two types of phyllosilicates: Those having a 1:1 ratio, such as kaolin, in which each lamella is made up by only two layers (one octahedral and one tetrahedral) and the phyllosilicates. There are two types of phyllosilicates: Those having a 1:1 ratio, such as kaolin, in which each with a 2:1 ratio, such in which a single is formed bythe an phyllosilicates octahedral layer lamella is made up as bymontmorillonite, only two layers (one octahedral and lamella one tetrahedral) and interposed between two tetrahedral layers and, there is the presence of weak Van with a 2:1 ratio, such as montmorillonite, in which a single lamella is formed by an octahedral layerder. 1 shows, in a schematic way, the structure interposed between the twovarious tetrahedral layersFigure and, there is the presence of layered weak Van der.

Methods

Findings

Discussion

Conclusion