Cleaving of muscovite powder by molten lithium nitrate

Muscovite powder was cleaved along the (0 0 1) planes in molten lithium nitrate. The condition for optimal cleavage was 1 g muscovite with 17 g lithium nitrate at 350 °C for 12 h. The specific surface area of muscovite increased from 3.5 to 170 m²/g. IR spectroscopy and XRD confirmed that the structure of muscovite did not change. Reaction with some other alkaline nitrates did not markedly increase the specific surface area.     

The intercalation of cetyltrimethylammonium cations into muscovite by a two-step process: I. The ion exchange of the interlayer cations in muscovite with Li

A new method to prepare alkylammonium ions-intercalated muscovite is reported. It has been obtained in a two-step process: the first step is the inorganic ion exchange, which allows the ion exchange of interlayer cations in muscovite with Li⁺ in a melting condition of LiNO₃. It was found that in the LiNO₃ treatment process most of the interlayer cations were replaced by Li⁺, and a large amount of water entered the interlayer space of muscovite. Therefore the spacing of muscovite (001) plane d₍₀₀₁₎ was enlarged from 19.92 to 24.16 Å, which could allow for the intercalation of organic cations. SEM shows that the LiNO₃ treatments have little effect on the size of muscovite platelets. TEM and FTIR confirm that not only the chemical composition but also the structure of the aluminosilicate layer has not been changed by the LiNO₃ treatments.     

The intercalation of cetyltrimethylammonium cations into muscovite by a two-step process: II. The intercalation of cetyltrimethylammonium cations into Li-muscovite

The alkylammonium cations were successively intercalated into the interlayer of muscovite. It was achieved by inorganic-organic ion exchange in the hydrothermal reaction of the LiNO₃-treated muscovite with cetyltrimethylammonium bromide solution. One-dimensional Patterson plots and electron density calculations show that hydrated Li⁺ and CTA⁺ cations entered the interlayer of muscovite successively. The CTA⁺-intercalated muscovite was characterized by powder X-ray diffraction and elemental analysis, in conjunction with FTIR, nuclear magnetic resonance, X-ray photoelectron spectra, high-resolution transmission electron microscopy, etc. The experiments show that organo-muscovite composite with ordered structure has been obtained. The CTA⁺ headgroups are distributed in the interlayer uniformly. However, the arrangement and conformation of CTA⁺ chains are strongly dependent upon the reaction temperature. At lower reaction temperature, the chains of CTA⁺ ions adopt a little more disordered arrangement and have higher gauche/trans conformer ratio, resulting in the disturbance to the interlayer symmetry. Whereas at higher reaction temperature, the sample with paraffin-like arrangement of CTA⁺ chains could be obtained, in which the methylene chains of CTA⁺ adopt a fully stretched, all-trans conformation.     

Rare earth element patterns in biotite muscovite and tourmaline minerals

Rare earth element concentrations in the minerals biotite and muscovite from the mica schist country rocks of the Etta pegmatite and tourmalines from the Bob Ingersoll pegmatite have been measured by INAA and CNAA. The concentrations range from 10^–4 g/g to 10^–10 g/g. The REE patterns of biotite, muscovite and tourmaline reported herein are highly fractionated from light to heavy REE. The REE concentrations in biotite and muscovite are high and indigenous. The pegmatite tourmalines contain low concentrations of REE. Variations in tourmaline REE patterns reflect the geochemical evolution of pegmatite melt/fluid system during crystallization.Work supported by the U. S. Department of Energy under Contract DE-AC06-76RLO 1830.     

Dehydroxylation kinetic and exfoliation of large muscovite flakes

The thermal transformations of muscovite flakes are a key point in many applications because besides dehydroxylation a significant exfoliation process occurs. Dehydroxylation kinetic is experimented by isothermal TG analyses in the 700–850°C temperature range and described with the Avrami theory. Hydroxyl condensation predominates at the onset of the process, but water diffusion is the most important process when the transformed fraction is high. The progressive transition between the two transformation stages contrast with the more accentuated transition for a ground muscovite. The activation energy varies weakly (190–214 kJ mol⁻¹) in the whole transformation process that supports the co-existence of hydroxyl condensation and diffusion phenomena. Dehydroxylation kinetic increases strongly with temperature and decreases with the reaction advancement. Exfoliation is correlated with dehydroxylation kinetic and occurs in a narrow transformation and temperature ranges. An in-situ combination process of hydroxyls occurs and water vapor favors the layer expansion.     

Paradigms and Paradoxes:Estimation of the Enthalpies of Formation of Some Common,Solid-Phase Compounds of Considerable Theoretical Importance

The enthalpies of formation of the following solid-state species are estimated: calcium carbonate, muscovite, graphite, cellulose, and silicon, which, as found in chalk, slate, pencil lead, paper, and integrated circuits, are key reagents in numerous theoretical studies. Agreement between theory and experiment is within 40 kJ mol^–1.     

Determination of anisotropic surface characteristics of different phyllosilicates by direct force measurements

To fundamentally understand the electrokinetic behavior of clay minerals, it is necessary to study the anisotropic surface charge properties of clay surfaces. In this study, two 2:1 layer natural minerals, talc and muscovite, were chosen as representatives of magnesium and aluminum phyllosilicate minerals, respectively. The molecularly smooth basal planes of both platy minerals were obtained by cleavage along the basal planes, while suitable edge surfaces were prepared by an ultramicrotome cutting technique. Silicon nitride atomic force microscopy tip was used as a probe to study the interaction forces between the tip and clay basal/edge surfaces in aqueous solutions of various pH values. The measured interaction force profiles between the tip and clay basal/edge surfaces were fitted with the classical DLVO (Derjaguin-Landau-Verwey-Overbeek) theory, which allows direct determination of electrical surface potential of talc and muscovite surfaces. The surface potential of muscovite basal planes was found to be significantly more negative than the basal plane of talc, both being pH insensitive. In contrast, the surface potential of edge surfaces was highly pH-dependent, exhibiting a point of zero charge (PZC) at pH 7.5 and 8.1 for edges of muscovite and talc, respectively. The observed differences in surface potential of basal planes and edge surfaces for both talc and muscovite are closely related to their crystal structure and ionization characteristics. The protonation reactivity and the contribution of each surface group to the surface charging behavior are modeled using their protonation constants.     

Cu(II)-intercalated muscovite: An infrared spectroscopic study

Diffuse reflectance infrared spectroscopy (DRIFT) has proved to be a useful tool for the investigation of migration paths of intercalated metal cations within the layered structure of phyllosilicates like muscovite. While the fixation of small cations like lithium or copper in clay minerals and their migration paths have been studied extensively, they never have been reported for muscovite. Therefore, the aim of this study was to investigate the effects of a treatment with a supersaturated Cu-nitrate solution on the structure of muscovite. Additional X-ray diffractometric (XRD) data showed the formation of new d(0 0 l) and d(0 0 2) peaks, and thus proved that the new cations already were intercalated into the muscovite interlayers, although the concentration of the original interlayer cation potassium was nearly not affected. This suggested the simultaneous occurrence of both potassium and copper in the interlayers, resulting in an expansion along the c-axis and in a decrease of the a and b parameters. The spectroscopic investigations proved a migration of the cations deep into the tetrahedral sheets. As all bands which can be assigned to vibrations of the octahedral sheet (e.g. at 713 or 903 cm⁻¹) were strongly affected by the treatment, a fixation of Cu close to the OH-groups of the octahedral sheets was suggested.     

Adsorption of polymers with crown ether substituents on muscovite mica

Ultrahigh specific surface area muscovite with different ions at the surface (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Ca²⁺, Sr²⁺, Ba²⁺, Cu²⁺) was treated with aqueous solutions of low molecular weight crown ethers and polymers with crown ether substituents. The adsorption was assessed by UV analysis of the supernatant solution, and with TGA and IR spectroscopy of the mica solids. In contrast to other layered silicates, the low molecular weight crown ethers show no affinity to any of the muscovite surfaces. The polymers can adsorb, however, depending on the type of surface cation. The results indicate that at least some of the crown ether moieties are complexed to surface cations and that the diameter of the ions at the surface plays an important role in the adsorption process.     

Organothiol Monolayer Formation Directly on Muscovite Mica

Organothiol monolayers on metal substrates (Au, Ag, Cu) and their use in a wide variety of applications have been extensively studied. Here, the growth of layers of organothiols directly onto muscovite mica is demonstrated using a simple procedure. Atomic force microscopy, surface X‐ray diffraction, and vibrational sum‐frequency generation IR spectroscopy studies revealed that organothiols with various functional endgroups could be self‐assembled into (water) stable and adaptable ultra‐flat organothiol monolayers over homogenous areas as large as 1 cm². The strength of the mica–organothiol interactions could be tuned by exchanging the potassium surface ions for copper ions. Several of these organothiol monolayers were subsequently used as a template for calcite growth.     

The spectrophotometric determination of molybdenum and phosphorus by carminic acid method

A spectrophotometric method for the determination of molybdenum based on the use of carminic acid is proposed. Conformity to Beer's law was observed with an optimum concentration range of 1.5 to 8 ppm of molybdenum when absorbance measurements are made at 565 nm. The molar absorptivities for the determination of molybdenum are 1.4 × 10⁴ mol l⁻¹ cm⁻¹ at 565 nm and 5.1 × 10³ mol l⁻¹ cm⁻¹ at 336 nm. An indirect spectrophotometric procedure for the determination of orthophosphate based on the determination of the equivalent molybdenum in 12-molybdophosphoric acid was developed suitable for the determination of 0.03 to 0.18 ppm of phosphorus.     

Tailoring and investigation of surface chemical nature of virgin and ion beam modified muscovite mica

We report that the surface chemical properties of muscovite mica [KAl₂(Si₃Al)O₁₀(OH)₂] like important multi-elemental layered substrate can be precisely tailored by ion bombardment. The detailed X-ray photoelectron spectroscopic studies of a freshly cleaved as well as 12-keV Ar⁺ and N⁺ ion bombarded muscovite mica surfaces show immense changes of the surface composition due to preferential sputtering of different elements and the chemical reaction of implanted ions with the surface. We observe that the K atoms on the upper layer of mica surface are sputtered most during the N⁺ or Ar⁺ ions sputtering, and the negative aluminosilicate layer is exposed. Inactive Ar atoms are trapped, whereas chemically reactive N atoms form silicon nitride (Si₃N₄) and aluminum nitride (AlN) during implantation. On exposure to air after ion bombardment, the mica surface becomes more active to adsorb C than the virgin surface. The adsorbed C reacts with Si in the aluminosilicate layer and forms silicon carbide (SiC) for both Ar and N bombarded mica surfaces. Besides the surface chemical change, prolonged ion bombardment develops a periodic ripple like regular pattern on the surface.     

Determination of calcium and barium in steel by electrothermal atomic emission spectrometry

A simple and rapid method is described for the determination of 1–40 μg g^?1 calcium in steels by electrothermal atomic emission spectrometry. The sample is dissolved in nitric acid and does not need preconcentration. The use of a recessed platform is shown to improve reproducibility and sensitivity in the determination of calcium. A similar procedure for the determination of barium (< 1 μg g^?1 in steel is described.     

The application of the ph-stat method to metal ion-catalyzed reactions

The pH-stat method, which is well known in organic chemistry and biochemistry, is used for the kinetic determination of metal ion catalysts. Indicator reactions that involve protons can be followed by controlled addition of standard base or acid. This is illustrated by the following examples: determination of copper(II) (0.03–0.3 μg ml^-1) with the indicator reaction ascorbic acid—peroxydisulphate; determination of molybdenum(VI) (0.2–2.5 μg ml^-1) with the indicator reaction thiosulphate—hydrogen peroxide; determination of zirconium(IV) (0.2–2 μg ml^-1) with the indicator reaction iodide—hydrogen peroxide; and determination of vanadium(V) (0.2–2 μg ml^-1) with the indicator reaction iodide—bromate. For one example, the copper—ascorbic acid—peroxydisulphate reaction, it is shown that the pH-stat method has distinct advantages over closed systems, giving considerably better sensitivity for the determination of copper (0.5–5 ng ml^-1 ).     

Kinetics and mechanism of dehydration of kaolinite,muscovite and talc analyzed thermogravimetrically by the third-law method

Summary The third-law method has been applied to determine the enthalpies, Δ_rH_T⁰, for dehydration reactions of kaolinite, muscovite and talc. The Δ_rH_T⁰values measured in the equimolar (in high vacuum) and isobaric (in the presence of water vapour) modes (980±15, 3710±39 and 2793±34 kJ mol^-1, for kaolinite, muscovite and talc, respectively) practically coincide if to take into account the strong self-cooling effect in vacuum. This fact strongly supports the mechanism of dissociative evaporation of these compounds in accordance with the reactions (primary stages): Al₂O₃·2SiO₂·2H₂O(s)→Al₂O₃(g)↓+2SiO₂(g)↓+2H₂O(g); K₂O·3Al₂O₃·6SiO₂·2H₂O(s) →K₂O(g)↓+3Al₂O₃(g)↓+6SiO₂(g)↓+2H₂O(g) and 3MgO·4SiO₂·H₂O(s) →3MgO(g)↓+4SiO₂(g)↓+H₂O(g). The values of the Eparameter deduced from these data for equimolar and isobaric modes of dehydration are as follows: 196 and 327 kJ mol^-1for kaolinite, 309 and 371 kJ mol^-1for muscovite and 349 and 399 kJ mol^-1for talc. These values are in agreement with quite a few early results reported in the literature in 1960s.     

Preparation of muscovite with ultrahigh specific surface area by chemical cleavage

The specific surface area of a muscovite sample increases drastically after exposure to a LiNO₃ solution, e.g., from 3.4 m²/g, corresponding to platelets of ca. 200 silicate layers, to 295 m²/g (platelets of ca. 2–3 silicate layers) after treatment at 180°C under atmospheric pressure for 46 h. The efficiency of the cleavage process decreases with decreasing temperature (down to 50°C). The LiNO₃/H₂O weight ratio is also very important: at 130°C and a reaction time of 46 h, for instance, a value in the range of 1.7–1.8 leads to the highest specific surfaces. The cleaved products have the form of strong papers that disperse readily in water. During the cleaving procedure, not only the particle thickness, but also the diameter decreases. There is no evidence of damage or partial dissolution of the silicate structure after cleavage, by IR spectroscopy and yield. The use of LiCl also leads to an increase in specific surface area, but the effect is weaker than in the case of LiNO₃. Treatment with some other alkaline and alkaline earth nitrates and chlorides did not increase the specific surface area of muscovite significantly.     

Some observations on the solvent extraction and spectrophotometric determination of palladium using 3,4-dihydro-4,4,6-trimethyl-2(1H)-pyrimidine-thione as a selective reagent

A highly selective spectrophotometric method is described for the determination of palladium, using 3,4-dihydro-4,4,6-trimethyl-2(1H)-pyridinethione (DTPT). The intense yellow 1:2 complex is extractable in chloroform from aqueous solution of pH 5.5. The maximum absorption occurs at 420 nm, ε = 3.90 × 10⁴ liter/mol⁻¹ cm⁻¹ and the sensitivity of the determination is 0.023 μg/ml. Palladium can be determined over a range of 0.4–24.6 ppm. CN⁻ interferes in this determination and should be absent. The method is applied to the determination of palladium in hydrogenation catalysts.     

Sorption and desorption of UO2 2+, Th4+ and Ru3+ on the synthetic analogue of muscovite</p> </p>

Summary Sorption and desorption of UO₂²⁺, Th⁴⁺ and Ru³⁺ on the synthetic analogue of the mica mineral muscovite has been studied by a batch technique. The synthesized gel was characterized by XRD, EDXRFS, FTIR, TGA and SEM and was found to have a composition K_1.4Al_4.2(Si₆Al₂O₂₀)(OH)₄ ^. 2H₂O. Different parameters like acid concentration, contact time, amount of gel, composition of gel: OPC admixture, effect of temperature, desorption of metal ions from loaded muscovite and effect on crystal morphology due to loading of metal ions were studied. The results has been expressed in terms of distribution coefficient (K_d).</p> </p>     

Flow injection chemiluminescence determination of isoniazid with electrogenerated hypochlorite

A flow-injection chemiluminescence method for the determination of isoniazid based on the sensitizing effect of isoniazid on the chemiluminescence generating luminol-hypochlorite reaction is described. The hypochlorite was electrogenerated on-line by constant current electrolysis, thus, eliminating instability of hypochlorite solution prepared from commercially available sodium hypochlorite. The calibration graph is linear in the range 1 × 10^–8 to 1 × 10^–6 g mL^–1, and the detection limit is 6 × 10^–9 g mL^–1. The relative standard deviation for determination of 5 × 10^–8 g mL^–1 is 2.8%. The proposed method has been successfully applied to the determination of isoniazid in pharmaceutical preparations.     

Electrochemical reduction of tartrazine at multi-walled carbon nanotube-modified pyrolytic graphite electrode

Electrochemical reduction of tartrazine on multi-walled carbon nanotube-modied pyrolytic graphite electrode is investigated. A simple, sensitive and inexpensive method for determination of tartrazine in drinks is proposed. The accuracy and reproducibility of the determination method for various known amounts of tartrazine were evaluated. This method was satisfactorily applied for the determination of tartrazine in drinks. The reduction peak currents were proportional to tartrazine concentrations over two intervals in the range from 2.0 to 70.0 mg l⁻¹ and from 70.0 to 230.0 mg l⁻¹, and the detection limit for tartrazine is 0.5 mg l⁻¹.