Vermiculite Interlayer Research Articles

Effective stabilization of heavy metals in solid waste and sludge pyrolysis using intercalated-exfoliated modified vermiculite: Experiment and simulation study

Pyrolysis is effective in reducing the volume of solid waste and sludge, and produces less pollutants than incineration and landfill, but the process still suffers from heavy metal pollution. Four types of intercalated-exfoliated modified vermiculite (UIV, DIV, TIV and 3IV) were prepared using urea, dimethylsulfoxide, tributyl phosphate and 3-aminopropyltriethoxysilane as intercalators for the control of Cd, Cr, Cu, Pb and Zn in municipal sewage sludge (MSL), paper mill sludge (PML), municipal domestic waste (MWA) and aged refuse (AFE). The larger the interlayer spacing of the vermiculite, the more favorable the retention of heavy metals. 3IV was the most effective additive, with an average retention of more than 75 % of all heavy metals at 450 ℃ for the four raw materials. Cr, Cu, Pb and Zn were all at low potential ecological risk (Pr), while Cd was moderate or considerable Pr, and the addition of 3IV reduced the Pr. Distribution of intercalators between vermiculite interlayers was haphazard, and interlayer spacing results were close to those of the experiment (except for tributyl phosphate). The reactive electrons mainly flowed from the Highest Occupied Molecular Orbital (HOMO) of vermiculite flakes to the Lower Unoccupied Molecular Orbital (LUMO) of heavy metal chlorides. In contrast, the reactive electrons mostly flowed from the HOMO of heavy metal oxides to the LUMO of vermiculite flakes. Heavy metal oxides were more readily adsorbed on vermiculite flakes than heavy metal chlorides, and the adsorption capacity of Cr and Zn was stronger than that of Cd, Pb and Cu.

The evidence for survival of high-grade diagenesis by dioctahedral vermiculite, as exemplified by upper Triassic rocks of the Tomanová Formation, Tatra Mountains Poland

The aim of the present work was to study the clay mineralogy of the Tomanová Formation - a ∼ 65 m thick complex of inland freshwater mudstones and shales of the upper Triassic age occurring in the Tatra Mountains. The formation was chosen for the study because it was assumed that, even though it underwent high-grade diagenesis, it could contain dioctahedral vermiculite-bearing clays. The clays have unique properties concerning the selective adsorption and the fixation of Cs+. Samples used in the present study were collected from outcrops located within Czerwone Żlebki in the Tomanová Valley in the Polish part of the Tatra Mountains. Seven horizons rich in clays were selected for the detailed mineralogical study. Both bulk samples and the clay fractions were analyzed using X-ray diffractometry, Fourier-transform infrared spectroscopy, and optical microscopy. Layer charges of swelling clays separated from the samples were measured using the OD method.All studied samples contained dioctahedral R0 and R1 illite-vermiculite-smectite mixed layered minerals mixed layered minerals (hereafter I-V-S) rich in dioctahedral vermiculite interlayers, kaolinite, quartz, anatase, and rutile. Three of the studied samples contained also berthierine. The swelling clays' measured mean layer charge values were in the vermiculitic range (i.e. 0.64–0.68/O10(OH)2). The common presence of kaolinite having a “poor degree of ordering” in the studied rocks indicated that quite an intense chemical weathering likely occurred within the alimentation area. The vermiculite-bearing clays (i.e. I-V-S) identified in the studied rocks were most likely also the products of the paleo weathering. The I-V-S minerals survived the high-grade diagenesis most likely due to the potassium deficiency in the system preventing the clays from the illitization. Those findings may suggest that deposits of dioctahedral vermiculite-bearing clays can be found even within geological formations that underwent high-grade diagenesis, which is of exploration importance because dioctahedral vermiculite could be possibly used/utilized as a molecular sieve for 137-Cs immobilization in environmental applications.

Differential dissolution of interlayer, octahedral and tetrahedral cations of vermiculite in oxalic acid

AbstractPhysical and/or chemical changes such as refinement, component dissolution, exchange/adsorption, structural evolution and recombination of phyllosilicate minerals occur continuously in a naturally weakly acidic water environment. To compare the differential dissolution of cations that occupy various sites in vermiculite, trioctahedral vermiculite was dissolved in various concentrations of oxalate for 24 h and in 0.2 M oxalate for various durations. The concentration of ions in the leaching solution and the phase, structure and morphology of the original samples and acid-leached samples were analysed. Structural analysis showed that the 001 reflections of vermiculite gradually shifted to a higher angle and eventually disappeared after the dissolution of interlayer cations caused by acid leaching. The amount and rate of dissolution of each cation in the vermiculite showed that the octahedral cation Mg2+ is more soluble than Fe2+ and Fe3+. The dissolution rates of Al3+, Mg2+ and Ca2+ were greatest in the first 4 h and then decreased gradually. Amorphous silicon dioxide and calcium oxalate were formed during acid leaching, and calcium oxalate was formed in the first 4 h. After leaching with oxalate for various periods, the cation-exchange capacity (CEC) of the samples first increased and then decreased. Micromorphology analysis showed that the acid erosion process started from the edges. The results of this work contribute to our understanding of many natural geochemical processes, and they will be useful for several applications such as soil improvement, ecological restoration and environmental protection.

Structural and Сrystal-Сhemical Features of Mixed-Layer Illite-Containing Minerals from Diagenetically Altered Upper Jurassic Oil Source Rocks

Illite-smectite (I-S) minerals from the Upper Jurassic oil-bearing rock shales of Denmark and the North Sea were studied by a complex of diffraction and spectroscopic methods. Detailed structures were identified to reveal the mechanism of diagenetic transformation of these shales. Usually, in oil-bearing rocks of sedimentary basins, oil generation occurs simultaneously with the I-S diagenetic transformation. The results obtained demonstrate the relationship between these two reactions: NH3 molecules released from kerogen during ma-ximum oil formation are fixed as NH4 ammonium cations in smectite or vermiculite interlayers, forming mica or tobelite structural fragments. As a result of this solid-phase transformation, mixed-layer structures are formed, consisting of layers of illite, tobelite, smectite and vermiculite (I-T-S-V).

High-efficiency removal of Cs (I) by vermiculite/zinc hexacyanoferrate (II) composite from aqueous solutions

Aimed to solve the problems of low adsorption capacity, complex preparation and difficult recovery for reported cesium ion adsorbents, a novel high-efficiency Cs+ adsorbent of vermiculite/zinc hexacyanoferrate (II) (VMT/ZnHCF) composite was prepared via in situ synthetic method. The structure and properties of this composite were comprehensively characterized using XRD, FTIR, SEM, TEM, and TG-DTA. The maximum Cs+ adsorption capacity was recorded to be 378.79 mg/g, and this value was significantly higher than the values recorded for other absorbents. This spontaneous and exothermic adsorption behavior could be explained by the Langmuir isotherm model and the pseudo-second-order kinetic model. In addition, this composite exhibited excellent selective adsorption ability towards Cs+ even in solutions containing high concentrations of Na+, K+, Ca2+, and Mg2+. The Cs+ adsorption mechanism was analyzed by conducting ion exchange experiments and using XRD, SEM, and XPS techniques. The Cs+ adsorption of the VMT/ZnHCF composite was synergistically achieved through the ion exchange of Na+ in vermiculite interlayers and Zn2+ in zinc hexacyanoferrate (II) lattices. A high-efficiency and simple preparation of cesium ion adsorbent has been developed in application of cesium ion wastewater treatment. This work can provide theoretical guidance to realize the non-hazardous treatment of radioactive wastewater.

Essential role of the interlayer of montmorillonite, vermiculite, and illite for Ni(II) sorption

Essential role of the interlayer of montmorillonite, vermiculite, and illite for Ni(II) sorption

Collectable adsorbent based on the adsorption characteristics of sodium citrate-pretreated vermiculite for cesium ion in an aquatic environment

This study aimed to develop a collectable adsorbent for Cs using clay mineral and alginate gel. The adsorption capacity of vermiculite (Verm) for Cs increased from 97.1 mg/g to 119 mg/g after sodium citric treatment. The Verm used in this study has a partial chlorite structure, and the existence of interlayer material was considered. The adsorption sites of Verm for Cs increased because the interlayer material in the partly chlorite structure was removed via sodium citric treatment. The Langmuir adsorption isotherm described this adsorption phenomenon well, indicating that the adsorption of Cs by Verm after sodium citric treatment (Verm-Cit) is monolayer adsorption. Since a typical phenomenon was also observed in which the basal spacing became approximately 1.0 nm when Cs was adsorbed by the interlayer of vermiculite, the interlayer of Verm-Cit functioned as an adsorption site. Verm-Cit was encapsulated in alginate gel beads (AG-Verm-Cit) for accessible collection after adsorption. Although the equilibrium adsorption time of AG-Verm-Cit was extended from 10 min without encapsulation (Verm-Cit) to over 360 min, an adsorption capacity of 60.5 mg/g was obtained even after 30 min. The developed adsorbent requires time to reach equilibrium; however, the adsorption capacity was similar to or higher than reported in previous studies, even with a relatively shorter contact time. Additionally, the weight and volume of the adsorbent encapsulated in alginate gel beads can be decreased by air drying without heat. These properties can contribute to removing Cs from the aquatic environment and to the stable management of adsorbents with radionuclides.

Copper (Cu) speciation in organic-waste (OW) amended soil: Instability of OW-borne Cu(I) sulfide and role of clay and iron oxide minerals

The geochemistry of copper (Cu) is generally assumed to be controlled by organic matter in soils. However, the role of clay and iron oxide minerals may be understated. Soil density fractionation, X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS) were combined to assess the long-term behavior of Cu in an agricultural soil subject to organic waste application. Two unprecedented molecular environments of natural Cu (i.e. Cu inherited from the parent rock) in soils are reported: Cu dimer in the interlayer of vermiculite and Cu structurally incorporated within hematite. Moreover, the soil naturally containing Cu-vermiculite, Cu-hematite, but also Cu-kaolinite (Cutotal = 122 mg·kg−1) was amended over 11 years with Cu-rich pig slurry in which Cu was 100 % Cu(I) sulfide. Natural Cu associated with clay and iron oxide minerals persisted in the amended soil, but the exogenous Cu(I) sulfide was unstable. The increase in Cu concentration in the amended soil to 174 mg·kg−1 was accounted for the increase of Cu sorbed to kaolinite and Cu bound to organic matter. These results are important for better understanding the natural occurrence of Cu in soils and for assessing the environmental impacts of organic waste recycling in agricultural fields.

Adsorption of lead and antimony in the presence and absence of EDTA by a new vermiculite product with potential recyclability.

A new two-step modification method has been proposed where 1.8% HCl and 3.1% HNO3 were applied to modify the interlayer of vermiculite (VMT). This product was given 90 °C of heat in 30% H2SO4 solution that was used for Pb (II) and Sb (III) adsorption. The EDTA presence on the individual adsorption was assessed. X-ray diffraction revealed that the VMT inter-stratified reflection through acid intercalation within the interlayer decreased the parallel gaps between the atoms, witnessing on the outer-sphere adsorption. The driving force was found electrostatic, which fits well with pseudo-second-order kinetics and Langmuir isotherm. The Pb (II) and Sb (III) uptake followed descending order adsorption with increasing concentration of chelating EDTA. Three consecutive desorption cycles revealed that the prepared adsorbent was suitable that may be regarded as a good candidate for complex wastewaters.

Polyethylene/Organo-Inorgano Vermiculites and Their Antimicrobial Properties.

Clay mineral vermiculite was treated with silver and copper nitrate solutions and samples were subsequently modified with organic compound (dodecylamine) via solid-solid melt intercalation. Prepared organo-inorgano vermiculites were used as nanofillers to the polyethylene matrix. Mixtures of polyethylene with vermiculite nanofillers, prepared by melt compounding technique, were pressed into thin plates. Structure changes of prepared powder vermiculite nanofillers and polyethylene/vermiculite composites were studied by X-ray diffraction analysis. The X-ray diffraction patterns of vermiculite nanofillers confirm intercalation of dodecylamine into the vermiculite interlayer. Antimicrobial properties of powder vermiculite nanofillers were evaluated by the minimum inhibitory concentration of samples which is needed to completely stop the bacterial growth and polyethylene/vermiculite composites were evaluated by the number of colony forming units survived on surfaces of composite plates. Different bacterial strains were studied: (1) Gram-positive, represented by bacteria Staphylococcus aureus and Enterococcus faecalis, (2) Gram-negative, represented by bacteria Escherichia coli and Pseudomonas aeruginosa, and (3) yeast, Candida albicans. Powder vermiculite nanofillers and surfaces of polyethylene/vermiculite composites showed good antimicrobial effect against tested bacteria and yeast. Powder vermiculite nanofillers show antimicrobial effect already after 30 minutes of tested time. Composite plates exhibited decrease of colony forming units number about 5-7 logarithmic orders depending on bacteria after 24 hours of tested time.

Ni(II) sorption mechanism at the vermiculite-water interface: Effects of interlayer

In this study, the effects of interlayer on Ni(II) sorption at the vermiculite-water interface was investigated by combining batch technique, surface complexation model (SCM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and extended X-ray absorption fine structure (EXAFS) analyses. The results showed that alkali cations can enter the interlayer of vermiculite, and cause the collapse of vermiculite interlayer to different extent mainly due to the different ionic radii and hydrated energies. XRD patterns confirmed the order of collapse extent following the trend of Cs+ ≈ Rb+ > K+ > Na+. Subsequently, the sorption edges of Ni(II) on vermiculite were exhibiting the same trends as the interlayer collapse extents in different electrolytes. SCM confirmed that the sorption was mainly controlled by ion exchange (IE) in low pH region, while the inner-sphere complexes (ISCs) and surface-induced precipitates became the dominant species in high pH region. Both XPS and EXAFS analyses have confirmed that the formations of Ni-precipitates and NiAl layer double hydroxide (NiAl LDH) were indeed enhanced after the interlayer collapsed. Therefore, the sorption mechanisms of Ni(II) could be regulated by the interlayer of vermiculite. These findings are of great importance to understand the sorption mechanisms of heavy metals at the expandable clay-water interfaces and their environmental behaviors.

The Impact of pH and Ion Exchange on 133Cs Adsorption on Vermiculite.

Many studies have shown that the adsorption of ions like K and Cs on 2:1 clay minerals can prompt the collapse of their interlayers and render the adsorbing ions nonexchangeable. This study sought to better understand this unique adsorption mechanism through the generation of an adsorption envelope for Cs adsorption on vermiculite and the exploration of the kinetics of interlayer collapse. The collapse of the vermiculite interlayer was confirmed via X-ray diffraction (XRD), and the timing of interlayer collapse was determined by placing Cs in competition with K at different time intervals. The adsorption envelope for Cs on vermiculite showed that although H competition does affect the adsorption of Cs on vermiculite, the effect of this competition is quite limited, even at very low pH values. This hypothesis is supported by the fact that XRD demonstrated a significant decrease in interlayer dimension after Cs adsorption. Finally, kinetics experiments showed that the irreversible adsorption of K and the collapse of the interlayer may take place on a much longer time scale than previously considered.

Method to make nests of useful components by way of accumulation

Experimental evaluation is given for mineral preconcentration in a bed of a sorption collector in percolation of low concentration useful components from aqueous solutions of salts. Sorption collectors represented by interlayers of lignite, peat, marble and vermiculite are included in an evaporation barrier installed in subsurface zone of rock mass aeration. Accumulation properties of such geochemical sorption barriers are examined. Migrating solution was aqueous solutions of salts of cobaltous and nickelous nitrates. It has been found feasible to shape beneficiation zones under up-going capillary permeation of the solutions through the sorption barriers in the zone of aeration in rock mass.

Molecular Models of Cesium and Rubidium Adsorption on Weathered Micaceous Minerals

Understanding the adsorption mechanisms of metal cations onto soils and sediments is of critical importance in the protection of the environment, especially for the case of radioactive materials including the fission product (137)Cs. Mechanism-based adsorption models for the long-term interaction of chemical and radionuclide species with clay minerals are needed to improve the accuracy of groundwater reaction and flow models, as well as related simulations for performance assessment of waste sites and repositories. Toward this goal, molecular simulation using geometry optimization and molecular dynamics methods have been used to investigate the adsorption behavior of Cs(+) and Rb(+) cations at frayed edge wedges (a proxy for frayed edge sites, FES) and in the interlayer region formed as a result of the transformation of muscovite to Al-hydroxy interlayered vermiculite (HIV) during weathering and pedogenesis. Frayed edge wedges, formed both on individual smectite and illite phases and on the mica-HIV intergrade, have previously been recognized as significant sinks for the strong adsorption of Cs(+) and Rb(+). Atomic density profiles, interlayer adsorption site maps, radial distribution functions, and adsorption enthalpies derived from the equilibrated structural models are used to evaluate the optimal adsorption configurations and thermodynamics for Cs- and Rb-endmembers, a 50:50 Cs-Rb composition for the aqueous interlayer of vermiculite, and for the interlayer wedge zone as mica is transformed to HIV (i.e., HIV-mica wedge). Adsorption enthalpies for both cations are significantly larger for the frayed edge wedges (as represented by the HIV-mica wedge model) compared to values for the vermiculite and mica interlayers. Cesium cation binds more strongly than Rb(+) in the vermiculite interlayer, while Rb(+) binds more strongly than Cs(+) in the HIV-mica wedge. In all cases, the derived adsorption enthalpies for both cations indicate a preference for the wedge environment where electrostatic interaction is enhanced due to the presence of layer charge and the increased size of interlayer at the wedge accommodating cations larger than K(+).

Experimental aluminization of vermiculite interlayers: An X-ray diffraction perspective on crystal chemistry and structural mechanisms

Natural aluminization of swelling clay minerals is ubiquitous in acidic soils leading to the formation of hydroxy-interlayered (HI) minerals. This process has drawn special attention over the last 4–5 decades owing to the negative impact on soil fertility of the induced reduction of cation exchange capacity. Combination of chemical analyses and of X-ray diffraction profile modeling on a series of experimentally self-aluminized samples aimed at an improved description of HI minerals and more especially of their interlayer crystal chemistry. Both exchangeable alkali cations and hydroxy (Al, Fe) cations coexist within HI vermiculite interlayers. The latter form discontinuous gibbsite-like interlayer sheets with ~15% completeness, despite layer-to-layer distances similar to that of chlorite. From charge compensation considerations, the isolated hydroxy (Al, Fe) cation clusters bear ~1.5 positive charges per cation. Analysis of X-ray diffraction data indicates that aluminization of initially swelling interlayers is a layer-by-layer process leading to mixed layers composed of randomly interstratified swelling and aluminized layers, all aluminized layers likely hosting a similar number of hydroxy (Al, Fe) cations along the aluminization process. This model contradicts the widely accepted description of HI minerals as a solid solution between expandable 2:1 clay and aluminous chlorite end-members. As a consequence, the proportion of HI layers in the mixed layer is a robust estimate of aluminization progress and both the amount of extractible (Al, Fe) and the extent of CEC decrease are positively correlated to this essential parameter.

Interlayer water molecules in organocation-exchanged vermiculite and montmorillonite: A case study of tetramethylammonium

Organoclays, unlike natural clays with inorganic cations that often have a hydration shell of H 2 O molecules, are organophylic and less adsorptive of H 2 O. These clays, therefore, are potentially important to remove organic contaminants from water; they are of great interest in industry for herbicide manufacture and as the basis for nanocomposite development; and they are of general interest in agriculture and in understanding soils. However, nothing is known about the positions of H 2 O in the interlayer when these molecules intercalate along with medium-sized hydrocarbon molecules, such as tetramethylammomium (TMA) cations. Even the positions of the TMA cations in the interlayer have been questioned recently. To resolve these issues, the orientation and position of TMA and H 2 O in the interlayer of vermiculite and montmorillonite were investigated by using atomistic computational methods. Interlayer H 2 O content, layer charge, and location of layer charge were considered. For both vermiculite and montmorillonite and where the number of H 2 O molecules is sufficient, TMA cations are located alternating between two planes in the interlayer. Each TMA cation is located near a tetrahedral-ring cavity of a 2:1 layer bordering the interlayer, and the H 2 O molecules are disordered. In the absence of H 2 O, TMA cations occur in one plane at the center of the interlayer. The major difference between vermiculite and montmorillonite is that the center of the TMA molecule in montmorillonite is 0.87 A from the center of the interlayer as compared to 1.22 A in vermiculite. Thus, the TMA cation is located closer to the tetrahedral-ring cavity in vermiculite, and this is a result of the greater tetrahedral charge of vermiculite. In fluorohectorite, which is similar in layer charge and origin of layer charge as the montmorillonite composition studied, the position of the TMA is expected to be similar to the montmorillonite results. These computational models are consistent with single-crystal, X-ray diffraction experiments for hydrated TMA-exchanged vermiculite and dried fluorohectorite.

Characterization of Andosols in Yakushima Island

We examined soils derived from volcanic ash of Kikai-Akahoya tephra on Yakushima Island, Japan, and classified them according to the Unified Soil Classification System of Japan, 2nd Approximation (USCSJ 2nd) and the World Reference Base for Soil Resources (WRB). Five pedons with horizons showing high (>20%) volcanic glass content were investigated. Soils developed under evergreen broad-leaved forests had high acid oxalate-extractable aluminum (Alo) and acid oxalate-extractable silicon (Sio) concentrations, and low acid oxalate-extractable iron (Fe)/dithionite-citrate-extractable Fe ratio. This indicates a warmer climate and less severe leaching conditions compared with soils developed under coniferous forests dominated by Cryptomeria japonica and grasslands dominated by Pseudosasa owatarii. All soils contained considerable amount of hydroxyl-Al-interlayered 2:1 clay minerals. The surface horizons of the pedons developed under the cool-temperate C. japonica forests contained smectite as a result of podzolization. However, the surface horizon of the pedon developed under cool-temperate P. owatarii grasslands did not contain smectite. All pedons belonged to the Kuroboku soils great group (USCSJ 2nd) and Andosols (WRB). Pedons in mountainous areas did not contain horizons with more than 6 g kg−1 of Sio and hence were classified as non-allophanic Andosols. In mountainous areas, it was observed that allophane formation was inhibited by Al leaching due to intense rainfall (>10,000 mm year−1); Al consumption due to the formation of the Al-humus complex; and Al incorporation into the interlayers of vermiculite. The low soil water pH [pH(H2O)] and leaching of silicon (Si) in mountainous areas would support these anti-allophanic effects.

Synthesis and Properties of Vermiculite-Reinforced Polyurethane Nanocomposites

Natural vermiculite was modified by cation exchange with long-chain quaternary alkylammonium salts and then dispersed in polyether-based polyols with different structures and ethylene oxide/propylene oxide ratios. The dispersions were evaluated by X-ray scattering and rheology. In all polyol dispersions tested, polyols were intercalated into the vermiculite interlayers. Also, significant shear thinning behavior was observed. A large interlayer spacing of ∼90 Å was achieved in one polyol suitable for polyurethane elastomer synthesis. In polyurethane made with this polyol, clay platelets were extensively intercalated or exfoliated. The composites showed a >270% increase in tensile modulus, >60% increase in tensile strength, and a 30% reduction in N(2) permeability with a loading of 5.3 wt % clay in polyurethane. Differential scanning calorimetry and dynamic mechanical analysis revealed that the nanoclay interacts with the polyurethane hard segments.

Selective adsorption and chiral amplification of amino acids in vermiculite clay-implications for the origin of biochirality

Smectite clays are hydrated layer silicates that, like micas, occur naturally in abundance. Importantly, they have readily modifiable interlayer spaces that provide excellent sites for nanochemistry. Vermiculite is one such smectite clay and in the presence of small chain-length alkyl-NH3Cl ions, forms sensitive, 1-D ordered model clay systems with expandable nano-pore inter-layer regions. These inter-layers readily adsorb organic molecules. N-propyl NH3Cl vermiculite clay gels were used to determine the adsorption of alanine, lysine and histidine by chiral HPLC. The results show that during reaction with fresh vermiculite interlayers, significant chiral enrichment of either L- and D-enantiomers occurs depending on the amino acid. Chiral enrichment of the supernatant solutions is up to about 1% per pass. In contrast, addition to clay interlayers already reacted with amino acid solutions resulted in little or no change in D/L ratio during the time of the experiment. Adsorption of small amounts of amphiphilic organic molecules in clay inter-layers is known to produce Layer-by-Layer or Langmuir-Blodgett films. Moreover atomistic simulations show that self-organization of organic species in clay interlayers is important. These non-centrosymmetric, chirally active nanofilms may cause clays to act subsequently as chiral amplifiers, concentrating organic material from dilute solution and having different adsorption energetics for D- and L-enantiomers. The additional role of clays in RNA oligimerization already postulated by Ferris and others, together with the need for the organization of amphiphilic molecules and lipids noted by Szostak and others, suggests that such chiral separation by clays in lagoonal environments at normal biological temperatures might also have played a significant role in the origin of biochirality.

Investigation of Inorganic-Intercalated Vermiculite by X-Ray Diffraction

Vermiculite is a layer silicate with an interlayer spacing about 1-2nm. The interlayer of inorganic-pillared vermiculite inlaid with a large amount of nanometer particles and micropores. It isn’t suitable to characterize the structure of inorganic-pillared vermiculite by SEM and TEM. In this paper, the microstructure of inorganic-pillared vermiculites obtained at different steps is characterized by XRD method. The interlayer spacing of inorganic-pillared vermiculite is obtained by analyzing the diffraction peak position and intensity in XRD patterns. The results show that the inorganic component is successfully inserted into the interlayer of vermiculite. Pillared vermiculite show higher intrinsic thermal stability and intensity than crude vermiculite.