High Resolution Electron Microscopy Structural Studies of Organo-Clay Nanocomposites

Abstract

Engineering of clay nanocomposite materials by modification of their surfaces can enable the control of retention, transport, and persistence of toxic chemicals in the geosystem. The properties and interactions of clay nanocomposites have been widely studied, but little information exists on their microstructure at a range of scale extending down to atomic dimensions. The pairing of Na-montmorillonite clay with organic cations as well as with the herbicide fluridone, chosen as a model for an organic pollutant, was studied. Three organic cations were selected: hexadecyltrimethylammonium, benzyltrimethylammonium, and benzyltriethylammonium at 0%, 60%, and 100% of cation exchange capacity (CEC) loadings. A detailed microstructural analysis of the organo-clay nanocomposites and of the fluridone nanocomposites was undertaken by high-resolution transmission electron microscopy (HRTEM) and X-ray energy-dispersive spectroscopy (EDS). Morphological observations and chemical analyses were performed simultaneously on the same sample. The combined HRTEM and EDS measurements strongly suggest (a) heterogeneous local intercalation of the organic cations manifested by a range in the measured d001 spacing, implying random expansion of the clay layered structure with increased loading of the organic cations; (b) intercalation within the external layers, which is thoroughly influenced by local defect microstructure and/or edge availability of the montmorillonite nanoparticles as well as by the molecular structure of the intercalating organic cation. Additional intercalation of fluridone molecules did not affect the structure (d001 spacing) of the organo-clay nanocomposites.

The effects of processing and organoclay properties on the structure of poly(methyl methacrylate)–clay nanocomposites

“…Likewise, these values are in line with the mean platelet lengths of between 75 and 82 nm determined for a Cloisite organoclay melt compounded in nylons of medium and high molecular weights [5]. The range of platelet lengths is also consistent with the 50e400 nm diameter tactoids observed by Yaron-Marcovich et al [70] during TEM characterisation of organoclays. This basic agreement provides support for the accuracy of the platelet-length data collected for bentonite and Cloisite clays used in this work.…”

Microbial effects in promoting the smectite to illite reaction: Role of organic matter intercalated in the interlayer

“…The d 001 layer spacing of 14.02 Å appears to be low for NAu-2 (Keeling et al 2000). Yaron- Marcovich et al (2005) observed the layer spacing of 16 to 19 Å for HDTMA-intercalated montmorillonite (Swy-1), with the layer spacing depending on the specifi c loading of HDTMA and thus different mechanisms of its interactions with expandable clay mineral. It is possible that the layer spacing may be as low as 14.02 Å when the loading of HDTMA is lower than 60%.…”

New strategies for submicron characterization the carbon binding of reactive minerals in long-term contrasting fertilized soils: implications for soil carbon storage

“…However, NanoSIMS cannot determine the morphology, elemental composition, and mineral species. High-resolution transmission electron microscopy (HRTEM) combined with selected area electron diffraction (SAED) is also a promising technique that can determine the morphology and provide detailed information on organo-mineral surfaces, as well as changes in their surface chemistries (Wen et al, 2014a;Yaron-Marcovich et al, 2005). Although direct observations of organo-mineral complexes by NanoSIMS and HRTEM have been previously described (Ramos et al, 2013;Vogel et al, 2014;Rumpel et al, 2015), few studies have reported the effects of fertilization practices on the organo-mineral complexes in soil colloids.…”