Fluorohectorite Clay Research Articles

Temperature Dependence Study of Water Dynamics in Fluorohectorite Clays Using Molecular Dynamics Simulations

We have carried out molecular dynamics (MD) simulation techniques to study the diffusion coefficient of interlayer molecules at different temperature. We have focused on the translation dynamics of water in bihydrated states within the context of water dynamics in clays. We concentrated on temperatures between 293 and 350 K, i.e., the range important to daily life wastewater handling. A natural clay has been modified as a synthetic clay called fluorohectorite clay, and the properties are studied using MD simulations, the result of which allows us to understand the determining parameters through a comparison with experiment values. The activation energyEais determined by our simulation to be between [0.09−0.17] eV per particle. The calculated diffusion constants are in the order of 10−5 cm2s−1. The simulation results are in a good agreement with experiments for the relevant set of conditions, and give insight into the origin of the observed dynamics.

Intercalation of CO2 Selected by Type of Interlayer Cation in Dried Synthetic Hectorite.

Clay minerals are abundant in caprock formations for anthropogenic storage sites for CO2, and they are potential capture materials for CO2 postcombustion sequestration. We investigate the response to CO2 exposure of dried fluorohectorite clay intercalated with Li+, Na+, Cs+, Ca2+, and Ba2+. By in situ powder X-ray diffraction, we demonstrate that fluorohectorite with Na+, Cs+, Ca2+, or Ba2+ does not swell in response to CO2 and that Li-fluorohectorite does swell. A linear uptake response is observed for Li-fluorohectorite by gravimetric adsorption, and we relate the adsorption to tightly bound residual water, which exposes adsorption sites within the interlayer. The experimental results are supported by DFT calculations.

Large bandgap insulating superior clay nanosheets

One can find conductive, semiconducting, and insulating single nanosheets with unique electronic properties that are tied to their two-dimensional (2D) structure. Here, we report on wide-bandgap 2D insulator nanosheets obtained by delamination of a synthetic 2D fluorohectorite clay mineral showing one of the largest bandgap insulators in the world. The bandgap was determined experimentally to be up to 7.1–8.2 eV measured by electron energy-loss spectroscopy in a high-resolution transmission electron microscope. The experimental data were supported by DFT calculations giving a bandgap of 5.5 eV. The single fluorohectorite clay crystalline nanosheets are 0.95-nm, and they can be synthetized with high-aspect ratios and lateral dimensions up to dozens of microns. These properties render these nanosheets promising candidates for practical applications in manually assembled or self-assembled electronic heterostructures, potentially serving as insulating nanosheets in graphene or various (semi)conductive 2D material-based devices.Impact statementProperties of the synthetic fluorohectorite clay presented in this article render these 0.95-nm-thin nanosheets promising candidates for practical applications in manually assembled or self-assembled electronic heterostructures, potentially serving as insulating nanosheets in graphene or various (semi)conductive 2D material-based devices.The information provided in this work can be essential for the growing community focused on the study of 2D materials and their wide range of applications.Graphical abstract

A nano-silicate material with exceptional capacity for CO2 capture and storage at room temperature

In order to mitigate climate change driven by the observed high levels of carbon dioxide (CO2) in the atmosphere, many micro and nano-porous materials are being investigated for CO2 selectivity, capture and storage (CCS) purposes, including zeolites, metal organic frameworks (MOFs), functionalized polymers, activated carbons and nano-silicate clay minerals. Key properties include availability, non-toxicity, low cost, stability, energy of adsorption/desorption, sorbent regeneration, sorption kinetics and CO2 storage capacity. Here, we address the crucial point of the volumetric capture and storage capacity for CO2 in a low cost material which is natural, non-toxic, and stable. We show that the nano-silicate Nickel Fluorohectorite is able to capture 0.79 metric tons of CO2 per m3 of host material - one of the highest capacities ever achieved - and we compare volumetric and gravimetric capacity of the best CO2 sorbent materials reported to date. Our results suggest that the high capture capacity of this fluorohectorite clay is strongly coupled to the type and valence of the interlayer cation (here Ni2+) and the high charge density, which is almost twice that of montmorillonite, resulting in the highest reported CO2 uptake among clay minerals.

Ciprofloxacin intercalated in fluorohectorite clay: identical pure drug activity and toxicity with higher adsorption and controlled release rate

We present the use of the synthetic clay fluorohectorite (Fh) as a drug delivery system of the antibiotic ciprofloxacin. The adsorption capacity is very high, and Fh promotes controlled drug release without changing drug effectiveness and toxicity.

Electric field nematic alignment of fluorohectorite clay particles in oligomeric matrices

Abstract

Dipolar structuring of organically modified fluorohectorite clay particles

This report focuses on both the characterization of organically modified fluorohectorite (Fh) clay particles and their electric-field-induced alignment when suspended in a non-polar liquid (silicone oil). Thermal decomposition temperatures of the surfactant molecules adsorbed on the clay surfaces and those being intercalated between clay crystalline layers were measured by thermal gravimetric analysis (TGA). Zeta potential measurements confirmed the successful modification of the clay surfaces. Optical microscopy observations showed that the sedimentation of modified particles was much slower compared to that of the non-modified system. It was shown that organic modification has a significant effect on colloidal stability of the system, preventing particles from forming large aggregates when suspended in a non-polar liquid. There are also signs of a slight increase in overall alignment of the clay particles when exposed to in an electric field, with the nematic order parameter (S(2)) being higher for the organically modified particles, compared to that of the non-modified counterparts. This behaviour is mainly a result of the formation of smaller and more uniform aggregates, in contrast to the large aggregate structures formed by non-modified clay particles.

ChemInform Abstract: Characterization of Copper(II)-Substituted Synthetic Fluorohectorite Clay and Interaction with Adsorbates by ESR, ESEM, and IR Spectroscopies.

ChemInform Abstract: Characterization of Copper(II)-Substituted Synthetic Fluorohectorite Clay and Interaction with Adsorbates by ESR, ESEM, and IR Spectroscopies.

Phase behavior of platelet-shaped nanosilicate colloids in saline solutions – a small-angle X-ray scattering study

A study of polydisperse suspensions of fluorohectorite clay in saline solutions is presented. The suspended clay colloids consist of stacks of nanosilicate sheets several tenths of a nanometre thick. They are polydisperse both with respect to the number of stacked nanolayers and with respect to their extension along the sheets. Due to this polydispersity, a spontaneous gravity-induced vertical segregation occurs in the sample tubes and results in the presence of up to four different phases on top of each other. Precise characterization of the phase diagram of the samples as a function of salt concentration and vertical position in the tubes, based on small-angle X-ray scattering data, is presented. The vertical positions of the phase boundaries were monitored by analyzing the eccentricity of elliptic fits to iso-intensity cuts of the scattering images. The intensity profiles along the two principal directions of scattering display two power-law behaviors with a smooth transition between them and show the absence of positional order in all phases.

Mesoscopic structure of dry-pressed clay samples from small-angle X-ray scattering measurements

Weakly hydrated samples of platelet-shaped nano-particles obtained by dry-pressing suspensions of the synthetic Na fluorohectorite clay are studied. The particles consist of stacks of several tens of 1 nm-thick nanosilicate platelets. They form a compound of quasi-two-dimensional particles whose average director is aligned with the direction of the uniaxial stress applied at dehydration. Small-angle X-ray scattering images from these samples are either isotropic or anisotropic, depending on the sample orientation with respect to the X-ray beam. From anisotropic images, changes in the scattering objects' orientation distribution probability (ODP) function are investigated as the temperature is lowered, thus triggering swelling of the individual particles by water intercalation. This is done, on the one hand, by inferring the width of the ODP function from the eccentricity of quasi-elliptic iso-intensity cuts of the small-angle scattering images, and, on the other hand, by obtaining the ODP function from azimuthal profiles of the images. The decays of the scattering intensity as a function of momentum transfer along the two principal directions of the images exhibit power law behaviors. A crossover scale between two power law regimes is observed on the profiles recorded along the horizontal axis; it corresponds to the typical pore size along the direction of the initially applied load. These results are compared with a previous study of similar systems.

Dynamics of water intercalation fronts in a nano-layered synthetic silicate: A synchrotron X-ray scattering study

We performed synchrotron X-ray scattering studies of the dynamics of the water intercalation front in a Na–Fluorohectorite clay. Like other smectite clays, fluorohectorite particles can swell due to intercalation of successive water layers. Monitoring the intensities of Bragg peaks of the known 1- and 2-water-layer hydration states at different positions in the sample enabled spatial and temporal measurement of the proportions of the different hydration states. From experiments with controlled temperature and an imposed humidity gradient on a quasi one-dimensional powder sample, we were able to localize the intercalation front and demonstrate that the width of this front was smaller than 2 mm after penetrating 9 mm into the sample. The speed at which the intercalation front advanced through the sample during the diffusion process was shown to decrease with time. The diffraction signature of random water intercalation in the vicinity of the intercalation front also provided information on the changes in the water content of the mesopores around clay particles.

Synchrotron x-ray scattering studies of water intercalation in a layered synthetic silicate.

Synchrotron x-ray diffraction studies were performed on a synthetic layered silicate Fluorohectorite clay. Diffraction patterns along the stacking direction were obtained in surface reflection and bulk transmission geometries on bulk pressed samples under controlled temperature and relative humidity. One-dimensional structure factors modeling the positions of the intercalant atoms have been obtained for three stable hydration states. From the narrow (00l) peak widths we conclude that well-crystallized domains consist of stacks of about 100 platelets, forming crystallites of the order of 0.1 microm thick. These crystallites have an orientational angular distribution of about 24 degrees around the stacking direction and represent the solid framework for microporosity in these samples.

Heterostructured Fluorohectorite Clay as an Electrochemical Sensor for the Detection of 2,4-Dichlorophenol and the Herbicide 2,4-D

A mixed-ion, amphiphilic fluorohectorite heterostructure, wherein the galleries are regularly interstratified by hydrophilic inorganic ions (Na + ) and lipophilic onium ions, is shown to be an efficient electrochemical sensor for the specific determination of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and the pollutant 2,4-dicholorophenol (2,4-DCP) when incorporated at the 5 wt % level into a carbon paste electrode (CPE). The clay-modified electrode was substantially less sentive to herbicides that lack the aromatic hydroxyl groups needed for oxidation to a quinone (e.g., Illoxan and Furore). Conventional homoionic organoclays with all galleries exclusively occupied by an onium ion surfactant exhibited a lower electrochemical response to 2,4-D and 2,4-DCP oxidation when incorporated into a CPE. Similarly, low current responses were observed for a CPE modified with a homostructured mixed-ion montmorillonite clay with both inorganic ions and organic onium ions cooccuping each clay gallery. The electrochemical response observed for the mixed-ion fluorohectorite heterostructure was attributed to the ability of this unique clay intercalate to achieve electrical neutrality upon oxidation of the dichlorophenoxy moiety through the facile ejection of sodium ions from the segregated inorganic galleries.

Clay Nanolayer Reinforcement of a Silicone Elastomer

A synthetic fluorohectorite clay in which the exchange cations have been replaced by hexadecyltrimethylammonium ions, abbreviated C16FH, has been shown to readily intercalate linear poly(dimethylsi...

A functionalized porous clay heterostructure for heavy metal ion (Hg 2+) trapping

A heavy metal ion adsorbent that binds Hg 2+ ions from solution to a capacity of 0.74 mmol/g has been prepared by grafting 3-mercaptopropyltrimethoxysilane to the intragallery framework walls of a porous fluorohectorite clay heterostructure (PCH). Up to 67% of the immobilized thiol groups are accessible for Hg 2+ trapping. This represents a significant improvement over previously reported clay-based ion adsorbents in which pore blockage limits the access of metal ions to fewer than 10% of the complexing sites. The uniform open-framework mesoporosity of PCH materials greatly facilitates access to most of the reactive sites attached to the pore walls. The possible use of PCH materials in future environmental remediation efforts is briefly discussed.

Characterization of copper(II)-substituted synthetic fluorohectorite clay and interaction with adsorbates by electron spin resonance, electron spin echo modulation, and infrared spectroscopies

Characterization of copper(II)-substituted synthetic fluorohectorite clay and interaction with adsorbates by electron spin resonance, electron spin echo modulation, and infrared spectroscopies