Baseline Studies of the Clay Minerals Society Source Clay Montmorillonite STx-1b

Abstract

For more than forty years, The Clay Minerals Society has dispensed a set of source clays which have enabled a large number of researchers to work on similar materials. Many of these source clays remained unchanged over the years but, conversely, other clays have gone out of stock and thus were replaced. This was the fate of montmorillonite STx-1a, which was replaced by STx-1b. Although STx-1a and STx-1b share many basic chemical and mineralogical features, some minor differences exist that can affect behavior. A baseline characterization of the source clay STx-1b, which was the objective of this study, was, therefore, necessary to provide researchers a tool useful not only for new investigation but also to compare new results obtained on STx-1b with literature data on STx-1a. This characterization was gained using traditional and advanced methods that included: 1) chemical composition (major and trace elements); 2) cation exchange capacity determination; 3) thermal analyses coupled with evolved gas mass spectrometry; 4) quantitative mineralogical characterization using powder X-ray diffraction and Rietveld- RIR (Reference Intensity Ratio) refinement; 5) X-ray absorption spectroscopy at the Fe K-edge; 6) diffuse reflectance ultraviolet-visible and infrared spectroscopies; and 7) 29Si, 27Al, and 1H magic-angle spinning nuclear magnetic resonance measurements. According to this multi-analytical approach, the chemical formula for STx-1b is [4](Si7.753Al0.247) [6](Al3.281Mg0.558Fe0.136Ti0.024Mn0.002) [12](Ca0.341Na0.039 K0.061)O20(OH)4.

A new material based on montmorillonite and Cu(II)-phenanthroline complex for effective capture of ammonia from gas phase

“…Montmorillonite STx-1b (Mt) from Gonzales County (Texas, USA) was obtained from the Clay Minerals Society, chemical formula: [4] (Si 7.753 Al 0.247 ) [6] (Al 3.281 Mg 0.558 Fe 0.136 Ti 0.024 Mn 0.002 ) [12] (Ca 0.341 Na 0.039 K 0.061 ) O 20 (OH) 4 , cation exchange capacity (CEC): 66.1 (±2.1) meq/100 g (Castellini et al, 2017). 1,10-phenanthroline monohydrate (Phen) and anhydrous NH 3 (>99 analytical grade purity) were purchased from Sigma Aldrich, CuSO 4 •5H 2 O (>99% analytical grade purity) from Carlo Erba.…”

Structural properties of adsorbent phyllosilicates rule the entrapping ability of intercalated iron-phenanthroline complex towards thiols

“…The UV-Vis spectra of Fe 3+ phen in solution, obtained at different concentrations, were reported by Bernini et al [20][21][22]. Fe charge-transfer transition) at λ = 356 nm and two additional bands at 223 and 266 nm attributable to the aromatic ligand.…”

“…Some previous studies dealing with the intercalation of lamellar layered silicates, such as montmorillonite, with cationic metal complexes, specifically Fe 3+ phenanthroline, showed that modifications by ion exchange reactions provide larger spacing between layers [20,21]. In these layer silicates, Fe…”

“…Al NMR spectra were obtained at 33 kHz MAS rates using single-pulse excitation with a 188 kHz spectral width, 2 s relaxation delay, 0.5 μs 45°pulse, 4k data points and 4k scans. All chemical shifts were referenced by adjusting the spectrometer field to the value corresponding to 38.48 ppm chemical shift for the deshielded line of the adamantane 13 C NMR signal, as previously reported [21]. Deconvolution of 29 Si, 27 Al, and 1 H NMR spectra was obtained with MNOVA 9.1.0 software.…”

Effect of Soil Solution pH during the Tetracycline Intercalation on the Structural Properties of a Dioctahedral Smectite: Microstructural Analysis

“…Montmorillonite is a natural nanomineral (layer thickness~1.0 nm) belonging to the smectite group. The intrinsic montmorillonite properties such as low permeability, high surface area, and cation exchange capacity (CEC) [11] promote its application in such context.…”