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Concrete is the favored construction material, with more than 7 billion cubic meters manufactured annually. Aggregates constitute the crucial component of its structure and quality, responsible for its exceptional characteristic features. The characteristics of aggregates determine the mechanical durability and radiation performance of concrete. In this investigation, fabricated concrete specimens were generated by replacing sand and aggregate sizes with pyrophyllite in 10%–20%–30%–100% proportions. The study investigated the mechanical properties of concrete specimens using both pressure and ultrasound methods, as well as their durability under freeze–thaw and high-temperature (200°C–1,000°C) conditions. In addition, the microstructure and radiation permeability properties were examined over a 7–28–90-day period. Notably, the use of pyrophyllite sand and aggregate significantly increased the compressive strength of the specimens by 21%–63% when compared to the reference concrete after 7–28–90 days, while also reducing mass loss by up to 4.6% during freeze–thaw cycles. After subjecting the specimens to high temperatures, it was discovered that those with an air-cooling regime achieved a compressive value 45% higher than the reference concrete. Microstructure images revealed the formation of C─ S─ H, CH, and portlandite hydration products over 90 days, supporting the observed compressive strength values. The study also has an effective linear attenuation coefficient (LAC) for radiation-shielding properties. According to some radiation-shielding parameters calculated through LAC values, it was revealed that these concrete samples were suitable shielding materials. Pyrophyllite-reinforced specimens have demonstrated potential for high-strength concrete production, suitability for use in high-temperature environments, and effectiveness as shielding in areas with radiation sources. [ABSTRACT FROM AUTHOR]

The widespread use of clay minerals and clays in environmental engineering, industry, medicine, and cosmetics largely stems from their adsorption properties and surface charge, as well as their ability to react with water. The dissolution and growth of minerals as a function of pH are closely related to acid–base reactions at their surface sites and their surface charge. The vivid tapestry of different types of surface sites across different types of clay minerals generates difficulties in experimental studies of structure–property relationships. The aim of this paper is to demonstrate how a mesoscale stochastic kinetic Monte Carlo (kMC) approach altogether with atomistic acid-base models and empirical data can be used for understanding the mechanisms of dissolution and surface charge behavior of clay minerals. The surface charge is modeled based on equilibrium equations for de/protonated site populations, which are defined by the pH and site-specific acidity constants (pKas). Lowered activation energy barriers for these sites in de/protonated states introduce pH-dependent effects into the dissolution kinetics. The V-shaped curve observed in laboratory experiments is reproduced with the new kMC model. A generic rate law for clay mineral dissolution as a function of pH is derived from this study. Thus, the kMC approach can be used as a hypothesis-testing tool for the verification of acid–base models for clay and other minerals and their influence on the kinetics of mineral dissolution and growth. [ABSTRACT FROM AUTHOR]

Mullite ceramics with high purity and toughness were prepared by hot‐press sintering of pyrophyllite at 1300°C using AlOOH nanomaterials with different sizes and morphologies (nanoparticles, nanorods, nanoflakes, and micro‐sized sea urchin–like) as additives. Among the four types of AOOH additives, the incorporation of nanoflakes and sea urchins resulted in the formation of a relatively uniformly distributed and tightly packed microstructure within the ceramics, which significantly improved the density and mechanical properties of the ceramic materials. Compared to nano‐sized AlOOH, the addition of micron‐sized sea urchin–like AlOOH could produce mullite ceramics with best purity and flexural strength. The flexural strength and fracture toughness of ceramics prepared from micro‐sized sea urchin–like AlOOH and pyrophyllite reach 427.34 ± 1.99 MPa and 4.68 ±.31 MPa m1/2, respectively. During the ball milling process, the originally micron‐sized sea urchin–like AlOOH particles were broken down into micro‐ and nano‐sized AlOOH particles. The resulted micron and nanoscale AlOOH particles exhibited synergistic and multi‐scale effects with pyrophyllite, which contributed to the formation of uniformly sized and densely arranged mullite crystals within the ceramics. Additionally, the bridging between the mullite crystals further improved the mechanical properties of the mullite ceramic material. [ABSTRACT FROM AUTHOR]

In this study, the effect of different beneficiation methods on aluminum recovery from pyrophyllite ore was investigated. Flotation method was used due to the naturally hydrophobic structure of pyrophyllite, and Attrition Scrubbing (AS) methods was used due to the difference in fragility. As a result of the beneficiation, concentrated samples were leached with HCl, and the amount of Al transferred to the solution as a result of the leaching was compared and evaluated. As a result of the beneficiation of the pyrophyllite ore with the AY method, a concentrate with a grade of 27.44% Al2O3 with a recovery of 54.79%, and a concentrate with a grade of 28.05% Al2O3 with a recovery of 30.49% by the flotation method. Accordingly, it was determined that the attrition scrubbing method was more efficient in terms of beneficiation efficiency, while the flotation method was more efficient in terms of leaching efficiency. When the final alumina amount and purity according to the raw ore were evaluated together, it was determined that the values of direct leaching and AY concentrate were close to each other. As a result, it is considered that it would be more accurate to determine the appropriate method by performing detailed economic analysis for the production of alumina from pyrophyllite ore. [ABSTRACT FROM AUTHOR]

Pyrophyllite is an important layered phyllosilicate material that is used in many fields due to its beneficial physicochemical and mechanical properties. Due to the presence of multiple defects in pyrophyllite, an in-depth investigation was conducted using density functional theory to explore the effects of Na(I), K(I), Mg(II), Ca(II) and Fe(II) doping on the atomic structure, electronic properties and mechanical characteristics of pyrophyllite. The results demonstrated that, among the studied defects, K(I) doping had the most pronounced effects on the lattice constants and bonding lengths of pyrophyllite, while the least significant effects were observed in the case of Fe(II) doping. Moreover, the partial and total densities of states and band structures of the five kinds of doped pyrophyllite also changed significantly due to the redistribution of electrons. Finally, the elastic constants of the doped pyrophyllite were lower than that of the undoped pyrophyllite. Doping with Na(I), K(I), Mg(II), Ca(II) and Fe(II) reduced the deformation resistance, stiffness and elastic wave velocity but increased the degree of anisotropy in pyrophyllite. The observed effects on the mechanical properties of pyrophyllite followed the order: Mg(II) > Fe(II) > Ca(II) >K(I) > Na(I). [ABSTRACT FROM AUTHOR]

High‐toughness mullite ceramics were fabricated through hot‐press sintering (HPS) of pyrophyllite and AlOOH, which were wet‐milled and well mixed using a planetary ball mill. The impacts of sintering temperatures and contents of AlOOH on mullite phase formation, densification, microstructure and mechanical properties in ceramic materials were investigated through XRD, SEM and mechanical properties determination. The results indicated that high‐toughness mullite ceramics could be successfully prepared by HPS at temperatures higher than 1200°C for 120 min. Increasing the sintering temperature from 1000 to 1300°C significantly enhanced the flexural strength and fracture toughness of samples. The highest flexural strength of 297.97±25.32 MPa and fracture toughness of 4.64±0.11 MPa⋅m1/2 were obtained for samples sintered at 1300°C. Further increase of temperature to 1400°C resulted in slight decrease of flexural strength and fracture toughness. Compared with the mullite ceramics prepared only using pyrophyllite as raw material, incorporation of AlOOH into raw material significantly increased the mechanical properties of final mullite ceramics. And stoichiometric AlOOH and pyrophyllite as starting material gave the best performance in fracture toughness. The high‐toughness of mullite ceramics were ascribed to the high mullite phase content, fine mullite whiskers and in situ formed, intertwined three‐dimensional network structure obtained through HPS at a low temperature of 1300°C. [ABSTRACT FROM AUTHOR]

Clays, inorganic materials with layered crystal structure, are widely used as a pharmaceutical excipients and active substances. The pyrophyllite, Al2Si4O10(OH)2, is an aluminosilicate mineral, that together with talc belongs to a specific sub-clay group. In this study, we examined some aspects of the use of pyrrophylite as a talc substitute. In this study, two pyrophyllite modifications have been investigated: the original pure pyrophyllite (labeled as PYRO), and that modified by incorporation of nanodispersed silver (labeled as PYRO/Ag). For pyrophyllite application in medicine, its thermal stability is of great importance. As an accelerated study of thermal stability, we employed simultaneous thermogravimetry and differential thermal analysis (TG/DTA) methods in dynamic (non-isothermal) regime in inert (N2) atmosphere. Pyrophyllite clay decomposition has been proved to proceed in two steps: moisture removal (I stage) and dehydroxilation (II stage). It must be stressed that these two degradation stages are not strictly separated. The kinetic parameters of decomposition reactions were examined by both isoconversional and model-fitting analytical procedures. The isoconversional Friedman model amounted activation energy (Ea) value on 65 kJ mol−1 and 214 kJ mol−1 for vaporization and dehydroxilation process, respectively. Fitting procedure revealed that vaporization process is of the n-th order (with activation energy, frequency factor and reaction order Ea = 66.6 kJ mol−1, A = 3.05 × 108 s−1, n = 3, respectively), while the dehydroxilation process, is best described with distributed activation energy models (Discrete: Ea = 232.2 kJ mol−1 (50.1%), with initial minimum frequency factor 3.66 × 109 s−1 and initial maximum frequency factor 3.66 × 1011 s−1). In addition to thermal properties, antimicrobial activity of pure (PYRO) and modified pyrophyllite (PYRO/Ag) were tested. Modified PYRO/Ag showed excellent antimicrobial properties, providing sterile conditions against Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922. The minimum bactericidal concentration (MBC) of Ag was found to be 25 mg L−1. [ABSTRACT FROM AUTHOR]

Nanocomposites of TiO2-clay were synthesized by the sol–gel route. The materials were characterized by XPS, XRD, UV–Vis DRS and BET surface area. Photocatalytic activity under UV irradiation (λmax ≈ 365 nm) was investigated by means of the phenol oxidation reaction. It was observed that the UV-photocatalytic property of TiO2-clay nanocomposite (SG) (Egap = 3.17 eV, SBET = 16.58 m2 g−1) for the phenol photodegradation was higher than that of commercial AEROXIDE® TiO2 P25. The activity of SG was greatly improved after silver photodeposition; in fact, the silver-photodeposited into SG highly enhanced the phenol degradation and mineralization efficiencies. The optimization of different experimental parameters, such as the photocatalyst amount, pH, temperature or hydrogen peroxide concentration on the phenol photodegradation under UV irradiation was studied with photodeposited catalyst 1.5%Ag/SG (Egap = 3.12 eV, SBET = 12.16 m2 g−1) based on the response surface methodology selecting composite central design as statistical model. Based on the ANOVA analysis, simulations explained a good fit to the experimental data involving a second-degree polynomial model with a model F-value of 73.31 and coefficient of determination (R2) value of 0.9959. Optimal experimental conditions were found to be a photocatalyst amount of 2 g L−1, solution pH of 5, temperature of 40 °C and hydrogen peroxide concentration of 8 mmol L−1. Under these optimized conditions, total degradation, 91% mineralization and non-toxicity were found, at 50 mg L−1 phenol during 120 min of reaction. Overall, pyrophyllite clay is very attractive as a natural and low-cost mineral for elaborating efficient photocatalysts. [ABSTRACT FROM AUTHOR]

The abnormal corrosion of hot iron ladles was investigated. The performance, the composition and the structure of bricks for hot iron ladles were analyzed. The results show that (1) compared with the alumina-silicon carbide-carbon bricks for the ladle bottom, those for the ladle wall have more pyrophyllite and the AI203 content of 36.32 mass%; their bulk density, apparent porosity and cold compressive strength are lower than the requirement of industry standard; they have poor anti-oxidation performance and are oxidized to form a porous layer during service, which loosens the brick lining structure thus leading to fracture, local wear and structural damage of bricks; (2) without preheating, steel scraps are not completely melted, resulting in slag or steel attachment at the mouth or the bottom of ladles thus increasing damage of ladles; (3) and the residual bricks react with the attached slag to form low melting point phases affecting their hot properties. The refractories for the lining of hot iron ladles must be improved in combination with process changes, not entirely by raw materials replacement to reduce costs. [ABSTRACT FROM AUTHOR]

In recent years, wide-bandgap semiconductor materials such as nano-TiO 2 and nano-ZnO have been extensively utilized in UV protection. However, there are some nonnegligible disadvantages, such as agglomeration and low transparency, which limit their applications. It is urgent to develop new UV shielding materials for UV-radiation protection. In the present study, a new ZnO/pyrophyllite nanocomposite was synthesized by a solid-state reaction method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence spectrometry (XRF) and UV–vis spectrophotometry. The photocatalytic activity test of the synthesized ZnO/pyrophyllite nanocomposite was also performed to analyse the application prospect of the nanocomposite. The results suggest that the ZnO/pyrophyllite nanocomposite's UV shielding rate is greater than 99% and is superior to that of conventional nano-ZnO. Moreover, the nanocomposite has better transparency than nano-ZnO in the visible light region. The degradation rate of methylene blue by the nanocomposite reached 92.1% after 150 min of UV radiation. The strong photocatalytic activity enables the nanocomposite to be a promising self-cleaning material. These results indicate that the synthesized ZnO/pyrophyllite nanocomposite could be a promising candidate for use in UV-protective and self-cleaning textile finishing industries. [ABSTRACT FROM AUTHOR]

Pyrophyllite (Prl), an aluminosilicate with a balanced mineral structure and extremely small particle size, appears to be an ideal filler but is rarely used in polymers. Herein, a method for the application of pyrophyllite in polymers is reported. A multifunctional filler is prepared by epoxy‐modified pyrophyllite and incorporated into poly(latic acid) (PLA) to enhance its processability and crystallization properties. Results show the effectiveness of epoxy‐modified Prl in composite film with a significant reduction in glass transition temperature, and noteworthy increment in crystallinity and spherulite growth rate. Water vapor barrier properties of PLA composite films increase over 30% with a range of Prl Loading. Furthermore, an enhancement of the tensile strength is increased by 30% and strain at break by 337.1% for PLA composite films compared to neat PLA. This work provides a new idea to prepare the functionalized pyrophyllite fillers and a theoretical basis to develop the application of pyrophyllite for polymers. [ABSTRACT FROM AUTHOR]

The majority of phenol-containing liquid industrial wastes are discharged into natural waters. As a result, several investigations, such as catalytic wet peroxide oxidation (CWPO), have been conducted to remediate these effluents. Copper-supported heterogeneous catalysts were prepared by an impregnation technique and tested in CWPO of phenol. Both the raw pyrophyllite clay and its zeolite form were used as supports. The samples were characterized by BET specific surface area analysis, X-ray diffraction, X-ray fluorescence, and X-ray photoelectron spectra. The effect of temperature (25–70 °C), the concentration of hydrogen peroxide (2–10 mmol·L−1), and the amount of catalyst (0.5–3 g·L−1) were selected for optimization of the catalytic system H2O2-2.5% Cu/ZP using the response surface methodology based on central composite design. The catalyst (2.5% Cu/ZP), with support of synthesized hydroxysodalite zeolite form, showed the best catalytic activity in comparison to that based on raw pyrophyllite support (2.5% Cu/RP). The maximized degradation was 100% after 4 h at optimum conditions (T = 50 °C, [H2O2] = 6.39 mmol·L−1, catalyst amount = 1.82 g·L−1) with 87.73% of mineralization. [ABSTRACT FROM AUTHOR]

Samples from the pyrophyllite reserves in the Malatya-Pütürge region, used in the production of the whitest cement in Europe, were beneficiated using flotation. The mineralogical composition of the natural pyrophyllite, as determined using X-ray diffraction, includes pyrophyllite, kaolinite, quartz, illite-mica and feldspar. The chemical composition of pyrophyllite contains 69.75% SiO2 and 23.04% Al2O3. The pyrophyllite percentage (40-45 wt.%) of the natural sample increased to 60-80 wt.% after flotation. In flotation experiments, the effects of reagent amounts, types and their mixtures were investigated. Methyl isobutyl carbinol (MIBC) and pine oil as frothers and kerosene as a collector were used in the flotation studies. The use of reagents as mixtures has a positive effect on the beneficiation compared to use on their own. The best result was obtained for a mixture of MIBC with kerosene, which is a non-ionic hydrocarbon oil, yielding a concentrate containing 26.63% Al2O3. Improved results were also observed for kerosene plus frother mixtures after flotation cleaning circuits. The bubbles formed during flotation were photographed and the bubble diameters were measured using the ImageJ program. The Al2O3 content was evaluated by correlating the bubble diameters. In general, selectivity decreased during experiments in which bubble diameters were reduced. [ABSTRACT FROM AUTHOR]

The present work is a review concerning the previous investigations on the vitrification behaviour of clays containing kaolinite, feldspars, muscovite (illite/sericite) and pyrophyllite. These clays are silico-aluminous and have interesting properties as raw materials for structural ceramics. The mineralogical and chemical composition were determined. Then, the vitrification in these clay samples using pressed bodies was investigated by few researchers in the temperature range 800–1350 °C with 0.5–5.5 h of soaking times. The effect of heat treatments on the degree of vitrification in these clays was characterized by bulk densities of the ceramic bodies at the fired stage. It was found some variations of bulk density values for all these clays fired in the range 1000–1150 °C, with marked decreases of the values obtained at 1200 °C and 1300 °C. A first order reaction kinetics was applied to the analysis of vitrification of the ceramic bodies under isothermal heating. The method is based on experimental data of bulk densities, being proposed for the estimation of the relative degree of vitrification resulting from different firing schedules. The analysis considered the temperature dependence of the rate of vitrification following Arrhenius behaviour. Thus, the vitrification activation energy can be obtained. The activation energies for the physical process of vitrification in these clays ranged from 45 to 151 kJ/mol. The relative rates of vitrification or degree of vitrification attained during heating and soaking were calculated. The results suggested that the contribution of vitrification due to heating in all these clays was relatively small compared to the vitrification during soaking. However, it was evidenced that the influence of the particle sizes in the thermal behaviour of these clays cannot be neglected. The vitrification rate equations, as deduced in these previous studies, can be useful tools to estimate the optimum firing conditions of these clays, allowing the extension of this method to other clay types. [ABSTRACT FROM AUTHOR]

Layered clay materials have been used to incorporate transition metal (TM) contaminants. Based on first-principles calculations, we have examined the energetic stability and the electronic properties due to the incorporation of Cd and Hg in layered clay materials, kaolinite (KAO) and pyrophyllite (PYR). The TM can be (i) adsorbed on the clay surface as well as (ii) intercalated between the clay layers. For the intercalated case, the contaminant incorporation rate can be optimized by controlling the interlayer spacing of the clay, namely, pillared clays. Our total energy results reveal that the incorporation of the TMs can be maximized through a suitable tuning of vertical distance between the clay layers. Based on the calculated TM/clay binding energies and the Langmuir absorption model, we estimate the concentrations of the TMs. Further kinetic properties have been examined by calculating the activation energies, where we found energy barriers of ~20 and ~130 meV for adsorbed and intercalated cases, respectively. The adsorption and intercalation of ionized TM adatoms were also considered within the deprotonated KAO surface. This also leads to an optimal interlayer distance which maximizes the TM incorporation rate. By mapping the total charge transfers at the TM/clay interface, we identify a net electronic charge transfer from the TM adatoms to the topmost clay surface layer. The effect of such a charge transfer on the electronic structure of the clay (host) has been examined through a set of X-ray absorption near edge structure (XANES) simulations, characterizing the changes of the XANES spectra upon the presence of the contaminants. Finally, for the pillared clays, we quantify the Cd and Hg K-edge energy shifts of the TMs as a function of the interlayer distance between the clay layers and the Al K-edge spectra for the pristine and pillared clays. [ABSTRACT FROM AUTHOR]

The efficient removal of Ethidium Bromide (EB), a toxic yet widely used chemical in biochemical industries and laboratories, is crucial to avoid its detrimental effect on human health, aquatic life, and the environment. One effective method is adsorption onto inert surfaces, but the choice of adsorbents is critical for the success of the removal protocols, primarily because of the limitations such as low adsorption capacity, high cost, limited availability, and a lack of understanding of the adsorption mechanism. In this work, Pyrophyllite Nanoclay (PNC), a naturally abundant aluminosilicate is explored as a promising adsorbent for EB. The adsorption process follows the Freundlich isotherm and displays pseudo-second-order kinetics. Under the optimized condition, PNC demonstrates nearly quantitative adsorption of EB and the maximum adsorption efficiency obtained from experiment was 6.53 mg/g (0.017 mmol/g) at room temperature under optimized condition. Through thermodynamic, kinetic analysis coupled with characterization techniques, the mechanism of adsorption is proposed. The adsorbent proves to be reusable, maintaining its performance over three cycles. The utility of the process is further validated and optimized using Response Surface Methodology (RSM). The present work focuses on the performance of PNC as adsorbent and elucidates distinctive surface adsorption mechanism (in comparison to other nanoclays), thus emphasizing the significance of structural, experimental, mechanistic and validation studies in choosing the right adsorbent for the removal toxic chemicals. [Display omitted] • Adsorption of Ethidium bromide on Pyrophyllite nanoclay (PNC) is investigated for the first time. • Kinetic and thermodynamic studies supported by characterization techniques reveal surface adsorption mechanism. • PNC is recyclable for at least three times. • Response Surface Methodology (RSM) optimization is conducted to validate the process. [ABSTRACT FROM AUTHOR]

Phyllosilicate clay minerals have been proposed as a possible buffer material to be used in deep geological repositories containing high-level waste and used nuclear fuel. This work precisely characterizes ion interactions with two types of adsorption sites present in these clays: Mg Al ' substitutions and undercoordinated edge surface atoms. A number of unique structural models were considered to represent the diverse local environments that ions in these systems are likely to encounter. Using molecular dynamics simulation with the CLAYFF potential, the spatial distribution, interlayer composition, and residence times of Na+ and Cl− ions as radionuclide analogs in pyrophyllite and montmorillonite clay models were investigated to identify the most favorable conditions for sequestration. The most significant factor impacting ion adsorption was found to be the localization of charge density at substitution sites. In a montmorillonite system in which substitution sites were distributed evenly to produce a low charge density, sequestration performance was found to be comparable to pyrophyllite. • MD simulation of phyllosilicate edge surfaces in NaCl solution reveal favorable adsorption sites. • Arrangement of Mg Al ' substitution sites can impact interlayer ion content and residence time. • Local charge density is the primary driver in determining adsorption site favorability. • Unhealed edge surfaces promote ion sequestration in the absence of Mg Al ' substitutions. • Evenly distributed Mg Al ' substitutions exhibit low interlayer residence time. [ABSTRACT FROM AUTHOR]

This paper analyzes the extreme application conditions of high temperature, high thermal shock and strong erosion of Al2O3-SiC-C refractories for molten iron ladles. It is considered that the main damage mechanism of the refractories is chemical corrosion of oxides (high contents of CaO, FeO and MnO) in the materials, reaction melting erosion, oxidation or decomposition of C or SiC in the materials, melting erosion at high temperatures, and damage under high thermal shock. The analysis results show that the low carbon and low silica Al2O3-SiC-C materials with high oxidation resistance should be used. The ratio of Al2O3 to SiO2 in the materials should be greater than 2.5, and the andalusite or pyrophyllite with microcracks, Al2O3 or Si3N4 with in-situ particles or fibers, and the clay or metal with ductility at high temperatures should be added to improve the high temperature corrosion resistance and thermal shock resistance. [ABSTRACT FROM AUTHOR]

We investigated the effect of fluorination of a nanocomposite photocatalyst on phenol photodegradation. We synthesized a new photocatalyst (SG750, SBET = 16.58 m2 g−1) by a sol–gel route, using titanium (IV) tetrabutoxide- and pyrophyllite-type clay, respectively, as precursor and support. The samples were characterized by FTIR, XRD, BET, SEM and DRS UV–Vis techniques. A fluorinated photocatalyst (F-SG750, SBET = 13.32 m2g−1) was synthesized with properties unlike other fluorinated photocatalysts reported in the literature. The results obtained prove that, contrary to other investigations in which the generation of free hydroxyl radicals (·OHfr) was increased with the fluorinated photocatalysts, in F-SG750 it resulted from the generation of surface hydroxyl radicals (·OHsf), which considerably increased. Consequently, the title photocatalyst gave rise to a higher photodegradation rate constant of phenol (kapp) than SG750. The response surface methodology (RSM) was used to optimize the operational parameters in the phenol photodegradation under UV light with F-SG750 based on the composite central design (CCD). Optimal operational parameters were found to be a solution pH of 5, photocatalyst amount of 2.5 gL−1, hydrogen peroxide concentration of 8 mmol.L−1, temperature of 40 °C. Operating at optimized parameters, total degradation, 91% mineralization and non-toxicity were found, at 50 mgL−1 phenol during 2 h of degradation. [ABSTRACT FROM AUTHOR]

Deformation of phyllosilicate can control the dynamics of the Earth's crust. The phenomenological relationship between stress and deformation is known for some typical phyllosilicates; however, the underlying physics originating from the crystal structures is poorly understood. In this study, the deformation mechanism of pyrophyllite along basal planes was revealed through density functional theory calculations and atomic-scale theory of friction. The stable and metastable interlayer structures formed by interlayer slide were consistent with the experimental results reported previously by high-resolution transmission electron microscopy. The difference in potential energies between stable and metastable interlayer structures can be interpreted as the diference in the stacking of dioctahedral sheets between the adjacent layers. The estimated friction coefficient of the pyrophyllite between adjacent layers was consistent with the results of atomic force microscopy, suggesting that atomic-scale friction can be adequately estimated by this method. The calculated shear stress in our simulations has a linear relationship with the normal stress and has no significant crystallographic dependence on sliding direction along the basal planes. The crystallographic isotropy of interlayer friction is explained by the absence of interlayer cations in pyrophyllite, while muscovite showed crystallographic anisotropy as observed in previous studies. The macroscopic friction of a single crystal of pyrophyllite was estimated from atomic-scale friction by using the area of contact. The macroscopic friction coefficient of ideal interlayer sliding was estimated to be 0.134, which was smaller than a reported value (0.276) in shear experiments conducted for wet polycrystalline gouge layers. This diference can be primarily explained by the degree of orientation of pyrophyllite particles in the gouge layers. The friction coeficient estimated by a simple model of randomly oriented pyrophyllite gouge layer was 0.203 ± 0.001, which was similar to the reported value of 0.276 and clearly smaller than the values (0.6–0.85) of common minerals estimated by the empirical Byerlee's law. These results indicate that weak interlayer friction of phyllosilicates has a large effect on the low frictional strength of gouge layers in natural faults. Our methodology and results are useful for understanding the physics behind the phenomenological friction laws of phyllosilicate gouge. [ABSTRACT FROM AUTHOR]

The paper presents the results of testing the effect of pyrophyllite shale (pyrophyllite) on the quality of maize plant silage, primarily on the production of organic acids, pH value, quality assessment and microbiological safety. The ensiling was done in plastic containers which allowed the storage of 10 kg of chopped green mass. Tested pyrophyllite doses were: 0% in the control treatment (I), 0.5 and 1.0% in experimental treatments (II and III, respectively). Granulated pyrophyllite (100 µm), originating from Parsovići, Konjic site, AD Harbi Ltd., Sarajevo, Bosnia and Herzegovina, was manually incorporated. The chopped green mass of the maize plant came from FAO 600 hybrids. The green mass containing 37.17% of dry matter (final waxy ripening phase) was compressed in the same manner in all three treatments during the filling of the vessels. The containers were then covered with nylon foil (0.2 mm) above which a layer of fine sand (approx. 5 cm) was placed in toward the silage protection from air passage. The silages were opened after 7 weeks and organoleptic, chemical and microbiological analyses were performed. The organoleptic properties of silages (colour and odour) were better in silages containing 0.5 and 1.0% pyrophyllite. The silage temperature at the moment of opening of the containers was lower in the treatments with 0.5 and 1.0% added pyrophyllite (13.7 and 13.2 °C, respectively) while in the control treatment it was 14.6 °C. The addition of pyrophyllite to silage affected the production of volatile fatty acids (p ≤ 0.05). The highest amount of lactic acid was found in the silage sample without the addition of pyrophyllite, and acetic acid in the silage treated with 0.5 and 1.0% of pyrophyllite. The lowest amount of butyric acid was determined in the silage with the addition of 1% pyrophyllite. Based on the content and interrelationship of lactic, acetic and butyric acid, as well as the pH values, all three silages were rated as the highest (I) class. The number of aerobic mesophilic bacteria, as well as the number of yeasts, was lower in the silages with the addition of 0.5 and 1.0% pyrophyllite. In future, particular attention should be paid on the possibility of pyrophyllite enrichment (e.g. with nitrogen) and more appropriate physical formulation (e.g. granules) that would allow more efficient practical application. [ABSTRACT FROM AUTHOR]

In this study, a clay sample recovered from an archaeological excavation from the Krobo Mountains in Ghana was examined for its potential to decolorize and adsorb cationic methylene blue. The raw and calcined clay samples were characterized with XRD, SEM, FTIR and EDX. The supernatant obtained by washing the raw clay with 70% ethanol solution decolorized methylene blue. The decolorization of methylene blue was independent of calcination temperature up to 300°C. The clay material subjected to calcination temperature at 600°C showed strong adsorption towards cationic methylene blue. The equilibrium adsorption data fitted well with the Freundlich isotherm indicating adsorption unto heterogeneous surface with the interaction between the adsorbed molecules which is not restricted to the formation of a monolayer. The data also fitted well with the Weber and Morris model which described the rate-controlling steps. The intra-particle diffusion was controlled by pore and surface diffusion. In addition, the adsorption data followed a pseudo-second-order kinetic model, indicating a chemisorption process. The results highlight a unique property of the clay material as an effective decolorizing and adsorption agent for the removal of water-soluble dyes from contaminated water bodies. [ABSTRACT FROM AUTHOR]

The water diffusion in four different, highly compacted clays [montmorillonite in the Na- and Ca-forms, illite in the Na- and Ca-forms, kaolinite, and pyrophyllite (bulk dry density ρb=1.85±0.05 g/cm3)] was studied at the atomic level by means of quasielastic neutron scattering. The experiments were performed on two time-of-flight spectrometers and at three different energy resolutions [FOCUS at SINQ, PSI (3.65 and 5.75 Å), and TOFTOF at FRM II (10 Å)] for reliable data analysis and at temperatures between 27 and 95 °C. Two different jump diffusion models were used to describe the translational motion. Both models describe the data equally well and give the following ranking of diffusion coefficients: Na-montmorillonite≤=Ca-montmorillonite≤Ca-illite≤Na-illite=Na-montmorillonite>Ca-illite>Na-illite>=kaolinite>pyrophyllite>=water, in both jump diffusion models. For clays with a permanent layer charge (montmorillonite and illite) a reduction in the water content by a factor of 2 resulted in a decrease in the self-diffusion coefficients and an increase in the time between jumps as compared to the full saturation. The uncharged clay kaolinite exhibited no change in the water mobility between the two hydration states. The rotational relaxation time of water was affected by the charged clay surfaces, especially in the case of montmorillonite; the uncharged clays presented a waterlike behavior. The activation energies for translational diffusion were calculated from the Arrhenius law, which adequately describes the systems in the studied temperature range. Na- and Ca-montmorillonite (∼11–12 kJ/mol), Na-illite (∼13 kJ/mol), kaolinite and pyrophyllite (∼14 kJ/mol), and Ca-illite (∼15 kJ/mol) all had lower activation energies than bulk water (∼17 kJ/mol in this study). This may originate from the reduced number and strength of the H-bonds between water and the clay surfaces, or ions, as compared to those in bulk water. Our comparative study suggests that the compensating cations in swelling clays have only a minor effect on the water diffusion rates at these high densities, whereas these cations influence the water motion in non-swelling clays. [ABSTRACT FROM AUTHOR]

Phyllosilicate materials (e.g., smectite) have been proposed to act as a waste barrier within long-term deep geological repositories. Aside from longevity, these clay materials must also limit the mobility of radionuclides, which is achieved through intermolecular interaction involving clay basal planes and edge surfaces. We aim to contribute to the fundamental knowledge of clay edges by investigating surface reconstruction in a dehydrated context. Using density functional theory, surface reconstruction, charge redistribution, and formation energies have been explored for pyrophyllite edges resulting from thirteen terminations. Three primary reconstruction mechanisms were identified: (1) the displacement of Al into the tetrahedral layer, (2) proton shift, and (3) sub-surface reconstruction involving sub-surface -OH or apical O and surface Si. Reduction in overall relative bond deficiency and charge redistribution to becoming more bulk-like were found to be the main driving force for reconstruction. Formation energies were also determined with dispersion correction for dehydrated and hydrated surfaces. The presence of water terminating agents reduced energetic costs by approximately one order of magnitude and the inclusion of dispersion correction resulted in indistinguishable formation energies between different hydrated surfaces. Linear regression models were also explored to predict surface formation energies based on relative bond deficiency and charge. These models were able to identify the key contributions to the surface energy; however, due to the small dataset they were not found to be predictive. • DFT calculations on dehydrated pyrophyllite edges fundamentally study surface reconstruction. • Inherent pyrophyllite edge surface reconstruction occurs via three major mechanisms. • Relative bond deficiency and charge distribution drive edge reconstruction in phyllosilicate clays. • Machine learning model can be used to identify key contributors to surface formation. • Presence of water terminating agent lowers surface formation energy by ∼1 order magnitude. [ABSTRACT FROM AUTHOR]

Analysis on suppression effect of depressant on naturally hydrophobic gangue minerals is of great importance for both industrial applications and theoretical research. In this work, the role of glucan in the flotation separation of pyrite and pyrophyllite was studied and the selective depression mechanism of glucan on pyrophyllite was discussed. The flotation tests indicate that pyrophyllite is a naturally hydrophobic mineral. Using glucan as a depressant can achieve flotation separation of pyrite from pyrophyllite at the natural pH of the pulp. This is attributed to greater adsorption and stronger depression effect of glucan on pyrophyllite than that of pyrite. According to Zeta-potential, Fourier transform infrared, X-ray photoelectron spectroscopy and molecular dynamics simulation results, glucan would selectively absorb on the pyrophyllite surface by chemical and physical adsorption between the OH hydrophilic group in glucan molecule and the Al/Si atom on pyrophyllite surface. Al O chemical complexation is considered as the main adsorption mode. The adsorption models of glucan molecule on (a) pyrophyllite (001) plane and (b) pyrite (010) plane. Easier adsorption of glucan caused a stronger depression effect on pyrophyllite than pyrite. Unlabelled Image • Glucan exhibits selective depression for pyrophyllite. • Flotation separation pyrite and pyrophyllite is obtained using glucan as depressant. • Selective adsorption of glucan on pyrophyllite occurs by Al O chemical complexation. [ABSTRACT FROM AUTHOR]

We explored the effects of gas emission by mixtures undergoing alkali-activation of municipal solid waste incineration fly ash (MSWIFA) and pyrophyllite (the mixtures included dehydrated pyrophyllite, MSWIFA, 14 mol/L aqueous sodium hydroxide, and sodium silicate; curing proceed at 105 °C for 24 h). We measured the compressive strengths of the derived solid composites. The causes of gas emission, and the physical and chemical properties of products created under controlled gas emission, were investigated. Hydrogen was emitted after mixing MSWIFA and alkali. The compressive strength of products prepared when gas emission was complete was 2–3.4-fold greater than that of products prepared when gas emission was incomplete. X-ray micro-tomography and mercury intrusion porosimetry showed that products formed during complete gas emission tended to have smaller pores. X-ray diffraction and nuclear magnetic resonance (27Al and 29Si) indicated that the aluminum substitution levels in tectosilicate differed under such conditions, although the minerals were identical. Thus, complete gas emission after mixing improved ultimate products. Image 1 • Reporting strength improvement of alkali-activated MSWIFA/pyrophyllite-based systems. • Effect of gas emission from the system on products' compressive strength was studied. • Complete gas emission before curing the system paste reduced porosity in product. • The strength correlated negatively with the proportion of large pores. • NMR found that more Q4(3Al) and Q4(2Al) in a product with better mechanical property. [ABSTRACT FROM AUTHOR]

Highlights • Commonly depressants suffer disadvantages of limited availability and high cost. • Xanthan gum is an excellent depressant for pyrophyllite suppression. • Xanthan gum molecule prefers to pyrophyllite (1 0 0), (0 1 0) surface. • Adsorption of xanthan gum on pyrophyllite is through its COO− groups. Abstract Pyrophyllite is the most common hydrophobic mineral encountered in Fengshan iron sulfide ore, China. Commonly depressants for separation of pyrophyllite suffer the disadvantages of limited availability and high cost. To solve this problem, a novel polysaccharide xanthan gum (XGM) was proposed for the suppression of pyrophyllite. The flotation response and depression mechanism were examined by flotation tests, adsorption and Fourier transform infrared spectra (FTIR), and molecular dynamics simulation (MDS) as well as scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). The flotation and adsorption tests showed that the floatability of pyrophyllite became weaker after adding the polysaccharide XGM compared with the conventional depressant guar gum (GG) and carboxymethyl cellulose (CMC). Meanwhile, the greater adsorption amount of XGM on the pyrophyllite surface was obtained than that of GG and CMC. Fourier transform infrared spectra, scanning electron microscope and molecular dynamics simulation were conducted to reveal the depression mechanism. The XGM molecule preferred to pyrophyllite surface, and anionic XGM strongly absorbed on pyrophyllite (1 0 0), (0 1 0) surfaces by COO− groups in its molecular structure. After treating with XGM, the oxygen atom was enriched and sodium atom was found on the pyrophyllite surface, which caused a strong chemisorption between XGM and pyrophyllite. On the whole, the polysaccharide XGM is an excellent depressant for pyrophyllite suppression. [ABSTRACT FROM AUTHOR]

Pyrophyllite-TiO2 nanocomposite PTi750 was successfully synthesized using a sol-gel method at ambient temperature based on exfoliation of the pyrophyllite layered clay by incorporation of the TiO2 precursor titanium(IV) t-butoxide. PTi750 exhibited higher photocatalytic activity in phenol degradation compared with commercial TiO2 Aeroxide P25. Ag-photodeposited PTi750 was more photoactive than PTi750, exhibiting detoxification, total degradation, and good mineralization of polluted solution and excellent stability after five reuses at optimal conditions in terms of the parameters pH, H2O2 concentration, and photocatalyst amount. The nanocomposites were investigated using several techniques, viz. diffuse-reflectance ultraviolet-visible (UV-Vis) spectrophotometry, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction analysis, X-ray fluorescence spectroscopy, Fourier-transform infrared spectroscopy, and Brunauer-Emmett-Teller (BET) specific surface area measurements. [ABSTRACT FROM AUTHOR]

Highlights • Spatial fragmentation reduces fire size and increases seed dispersal. • Spatial aggregation reduces the resilience of fire sensitive communities. • Spatial aggregation favors both persistence and resilience of fire prone communities. • The dynamics of dichotomous landscapes are driven by processes that affect the edge between communities. • We defineresiliense of dichotomous landscapes as their capacity to favor long-term coexistence of competing communities. Abstract Contagious processes such as fire and seed dispersal may affect landscape structure, composition and dynamics, and are in turn modulated by structural landscape attributes. Vegetation-fire self-reinforcing processes that lead to the dominance of either pyrophyllic or pyrophobic vegetation are well documented worldwide, but it remains unclear how the interaction between spatial aggregation and contagious processes influences the dynamics of dichotomous landscapes. We subjected landscapes composed by patches of pyrophyllic and pyrophobic cells to increasing frequencies of random ignitions to assess which spatial configuration may promote long-term coexistence (i.e. resilient landscapes), and which ones may lead to dominance by either community (i.e. alternative states). Our results indicate that aggregation favors the persistence and resilience of pyrophyllic communities, whereas the resilience of pyrophobic ones is enhanced by landscape fragmentation. Aggregation promotes larger fires whereas fragmentation favors seed dispersal, these two processes being related to total pyrophyllic core area, and total pyrophobic edge respectively. We propose that highly fragmented landscapes may facilitate the recovery of pyrophobic communities from fire events by affecting both the dynamics of fire and colonization: large numbers of pyrophobic patches function as an immolating network of partial firebreaks that reduce fire size, providing more opportunities for colonization and facing a lower individual risk of patch destruction through fire. Landscape attributes that reduce flammability at the local scale, such as rocky outcrops, creeks, wetlands and roads may fragment pyrophyllic communities thereby enhancing the resilience of pyrophobic ones. The resilience of pyrophyllic communities, on the other hand, will mainly depend on the size of their largest patches, even at low ignition frequencies. [ABSTRACT FROM AUTHOR]

Abstract There is an urgent need to dispose safely of the municipal solid waste incineration fly ash (MSWIFA) contaminated by cesium (Cs) released from the Fukushima Daiichi nuclear power plant accidents. This study investigated the relationship between quantitative Cs speciation and Cs immobilization in composite product from alkali-activated pyrophyllite and MSWIFA, with added stable cesium chloride and cesium carbonate. Cesium speciation was determined using X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS), while Cs immobilization was evaluated by a leaching method. Twenty-four composite products, with different Cs leaching properties, were prepared under various conditions. The XRD analysis of six composite products with different Cs leaching properties qualitatively identified a crystalline pollucite in the two products with the least Cs leaching. The quantitative speciation determined using XAFS revealed a strong negative correlation between the pollucite content in the 24 products and their Cs leaching ratio. Cesium species with a Cs O bond were found in all products. These were at least two Cs species with different leaching properties. These results indicate that the change from a Cs species to pollucite in the product increased the Cs immobilization level in the system. Graphical abstract Image 1 Highlights • Quantitative speciation and leaching properties of Cs in 24 products were studied. • Alkali-activated MSWFA with CsCl/Cs 2 CO 3 and pyrophyllite-based systems were used. • Pollucite and compounds with Cs O bond were determined as dominant species by XAFS. • Correlation between pollucite amount and the leaching property was strongly negative. • Changing Cs species to pollucite was a key to Cs immobilization in the system. [ABSTRACT FROM AUTHOR]

Abstract Many important properties of the clay minerals such as montmorillonite (Mt) arise from their surface chemistry especially when this material is submitted to an acid activation process which will result in materials catalytically active for a variety of reactions. The acid activation preferentially occurs on the edge surfaces, in this sense ab initio calculations were performed in order to determinate the most probable models for (010) and (110) surfaces in both pyrophyllite and Mt clay minerals, the edge stability, the initial stages of the acid activation process and the main acid sites present in the structures. The calculations predicted that the (110) edge surface is more stable than the (010) edge surface at pyrophyllite, on the other hand, at Mt the (010) surface has shown to be more stable, thus the pyrophyllite edge surfaces should not be used as representative models of Mt edge surfaces. The microstructural evolution of the Mt during the acid activation was investigated by 29Si and 27Al SSNMR simulations and these calculations could assist in the correct assignment of the silicon and aluminum chemical environments. The reactivity of the surfaces was evaluated and the calculations indicate that the acid character of the acid-activated Mt mainly comes from the H sites present in silanol and aluminol groups. These sites might be responsible for the catalytic activity of these materials. Highlights • Important properties of the clay minerals arises from their surface chemistry. • DFT calculations of the initial stages of the Mt. acid-activation process. • Pyrophyllite edge surfaces should not be used as representative of Mt. edge surfaces. • Microstructure of the acid-activated Mt. was investigated by 29Si and 27Al SSNMR. [ABSTRACT FROM AUTHOR]

Reports on the pressure dependence of the thermal conductivity of pyrophyllite. Value of thermal conductivity; Details of the thermal conductivity measurements; Configuration of the pyrophyllite cube, line source and placement of the thermocouple junctions.

• The adsorption and diffusion of CO 2 in pyrophyllite slit pores are investigated. • Interlayer water can increase the adsorption amount of CO 2 in pyrophyllite when the water content is less than 30 wt%. • Water can inhibit CO 2 diffusion in pyrophyllite slits. • CO 2 is mainly adsorbed on the pore surface of pyrophyllite in parallel configuration. Understanding the microscopic process of adsorption and diffusion of CO 2 in clay minerals is important for geological storage of CO 2. In this study, Grand Canonical Monte Carlo (GCMC) and Molecular Dynamics (MD) simulations are used to obtain the adsorption and diffusion behavior of CO 2 in pyrophyllite slit pores. The influence of split pore size, temperature, pressure, and water content were analyzed in detail. The adsorption characteristics of CO 2 in pyrophyllite were revealed by discussing the distribution of CO 2 density profile, adsorption capacity, isosteric heat of adsorption, interaction energy, mean square displacement, self-diffusion coefficient, and molecular orientation distribution. It shows that the excess adsorption isotherm of CO 2 in pyrophyllite slit pores demonstrate significant supercritical adsorption characteristics. Surface attractions originating from both pore walls overlap in the middle of pore, leading to an enhanced adsorption capacity of CO 2 in pyrophyllite slit pores when pore aperture is lower than 3 nm. In pyrophyllite pores, the presence of water has an enhancing effect on CO 2 adsorption when the water content is below 30 wt%. A maximum value of CO 2 adsorption amount is reached at the water content of 10 wt%, while negative growth occurs at 35 wt%. At low water content, water molecules form a weak adsorption layer due to the weak attraction of pyrophyllite to water. As water content increases, the self-diffusion coefficient of the CO 2 decreases, and the diffusion capacity decreases. The adsorption state of the CO 2 molecule on the mineral surface is primarily a parallel configuration, while the water molecule has no clear orientation. Our calculated results can provide guidance for further study of clay-water-adsorbate interface reaction of hydrophobic minerals. [ABSTRACT FROM AUTHOR]

Exceptionally preserved plant fossils from St. Clair, Pennsylvania, have long been part of museum and private collections. Fossil leaf fragments and stems from the underclay of the Buck Mountain Coal (Reading Anthracite Company quarry), lowest Llewellyn Formation (late Pennsylvanian, Virgilian), combine outer layers of coalified organic material (phytoleim) with strikingly white kaolinite, quartz, and the low-grade metamorphic mineral pyrophyllite in the interior. The surficial dark, coalified material appears to preserve the dense outer layers (cuticle, epidermis, and palisade layer) and some cells of the spongy mesophyll in the fossilized leaves. XRD spectra of separated phytoleim contain graphite peaks. Raman spectra with peaks near 1600 and 1320 cm−1 indicate that the phytoleim is composed of disordered graphitic material. I D /I G ratios from ca. 0.3 to 0.45 are consistent with greenschist facies metamorphic conditions forming the anthracite coal. The interior pyrophyllite is highly crystalline, with large crystals often oriented perpendicular to leaf surfaces. Hydrothermal formation of pyrophyllite requires relatively limited groundwater flow conditions and temperatures between ca. 275 and 350 °C. Although many fossil leaves are compressed, some are near their original thickness. We infer that the remains were replaced prior to significant burial and compression of the sediment by an early-forming mineral phase, possibly pyrite, which was in turn replaced by kaolinite and then pyrophyllite at higher temperature and pressure. Woody structures such as cuticle and veins, which had resisted replacement by the initial low temperature phase, were coalified at higher temperatures. • Distinctive fossils from St. Clair, Pennsylvania are composed of pyrophyllite, kaolinite, and pyrite. • Fern fossils may be only slightly compressed and must have formed by a multi-stage process. • Pyrophyllite in the fossils indicates a low-grade metamorphic origin, consistent with the formation of anthracite coal. [ABSTRACT FROM AUTHOR]

It is shown that the amount of aluminum-containing nanotechnogenic raw material based on non-ferrous metallurgy and pyrophyllite has a large effect on the structure and rheological properties of ceramic bodies in the production of acid-resistant materials. The use of nanotechnogenic raw material increases the physical and mechanical properties of ceramics for acid-resistant materials. Studies have shown that the presence of pores with isometric shape and oval closed porosity, unlike elongated (slit-shaped) pores, in ceramic materials impart mechanical strength to them. [ABSTRACT FROM AUTHOR]

A pyrophyllite [Al2Si4O10(OH)2] ore as an alternative source for alumina (Al2O3) was intensively milled for mechanical activation to increase aluminum extraction by acid leaching method. For this purpose, unmilled and milled ore samples were compared to reveal the changes caused by intensive milling. The samples were also leached in HCl solutions to determine whether mechanical activation increased the alumina extraction or not. The milling considerably disrupted XRD peak intensities of the clay minerals found in the ore, except quartz. After milling just for 30 min, peaks of the minerals were not distinguished, suggesting that all are amorphous. Dehydroxylation of the minerals in the unmilled ore was realized to occur at lower temperature ranges and energy consumed for dehydroxylation significantly reduced with prolonged milling. While aluminum recovery by leaching of the unmilled ore was about 12%, it increased to 73.09% as a result of milling the ore for 50 min. It was concluded that as the milling time is extended, energy needed to undergo dehydroxylation due to amorphization continues to decrease and aluminum recovery reaches higher values, suggesting that the clay minerals in the ore can be converted to mechanically activated state. [ABSTRACT FROM AUTHOR]

This paper addresses the effects of processing technique on the synthesis of mullite from pyrophyllite and alpha-alumina powder. The influence of firing temperatures were examined in order to optimize the fabrication process to achieved a suitable mechanical properties. Feedstock powders, with stoichiometric composition, were wet milled in an Attritor mill. The dried powders were consolidated using spark plasma sintering (SPS) in the temperatures range 1400 °C to 1700 °C under pressure of 50 MPa, with a heating rate of 100 °C/min at different holding times. Densities of 3.25 g/cm 3 and 3.17 g/cm 3 were obtained for the samples sintered at 1400 °C and 1600 °C respectively, with a 10-min holding time. The XRD and SEM/EDS were employed to characterize the firing transformation and microstructure of the samples. The SEM micrograph of samples, sintered at 1600 °C with 10 min holding times, revealed that the sample retained its equiaxed grain structure. The XRD results show a reduction in alpha-alumina content after the sample was fired. Hardness and fracture toughness values up to 11.73 GPa and 1.99 MPa•m 1/2 respectively were obtained. [ABSTRACT FROM AUTHOR]

The results of a physical and chemical investigation of pyrophyllite from the Kul'-Yurt-Tau deposit in the Republic of Bashkortostan (Russia) are presented. The features of the strengthening process, the structure, and the hardening kinetics were determined for the refractory composite based on quartz-pyrophyllite raw material. [ABSTRACT FROM AUTHOR]

Submerged ceramic membrane reactor treating industrial wastewater was combined with granular activated carbon (GAC) particles to control membrane fouling and organic removal efficiency. The GAC particles were suspended along the membrane surface under bulk recirculation only through the reactor without any gas sparging. Membrane support coated with Al 2 O 3 layer (CPM) and uncoated one (UPM) was compared at constant flux mode of filtration. The membrane support consisted of 80% of pyrophyllite and 20% of alumina. Under up-flow velocity of 0.031 m s −1 through bulk recirculation only without GAC particles, the fouling rates were observed as 0.011 and 0.013 bar h −1 for the CPM and UPM, respectively. With suspension of GAC particles, fouling mitigation was enhanced considerably and this effect was more pronounced with CPM than UPM under the same upflow velocity (90 vs. 57%). In addition, the GAC suspension increased critical flux by 46% higher with CPM than that observed without the carbon particles. The organic removal efficiency of the UPM was lower than that of CPM while the fouling rate was much greater probably due to pore blocking caused by organic dye compounds. For the both membranes, suspension of GAC particles along the membrane surface increased organic removal efficiency higher than 90%. The organic removal efficiency was enhanced by increasing permeate flux, but it became lower as upflow velocity was higher. [ABSTRACT FROM AUTHOR]

Abstract Minerals and elements in coal are derived from the processes associated with peat accumulation and rank advance, as well as possibly a range of epigenetic processes, and thus can provide information on the depositional conditions and geologic history of coal beds and coal-bearing sequences, as well as perhaps on regional tectonics. This paper investigates the petrology, mineralogy, and geochemistry of anthracites and their host rocks (partings, roof, and floor strata) from two coal deposits (Hongmao and Luocheng) in Guangxi Province, southern China. Samples collected from these deposits were analyzed using optical microscopy, scanning electron microscopy plus energy-dispersive X-ray spectrometry, low-temperature ashing, X-ray diffraction, X-ray fluorescence spectrometry, and quadrupole-based inductively coupled plasma mass spectrometry. The anthracites from the two deposits are medium- to high-sulfur coals. The rare earth elements in the Luocheng anthracites are characterized by distinct positive Eu anomalies and medium- and heavy-REE enrichment types. The minerals in the Hongmao anthracites are characterized by the occurrence of K-illite, paragonite, and ammonian illite, which, however, are absent in the Luocheng anthracites. The paragonite, ammonian illite, and chlorite resulted from the alteration of pre-existing kaolinite by hot solutions containing Na+, NH 4 +, and Fe2+ respectively. The partings in the Luocheng anthracite seams contain pyrophyllite that was formed by reactions between kaolinite and quartz during injection of high-temperature solutions. The mineralogical and geochemical characteristics of the anthracites in the two deposits indicate that the coals were subjected to high-temperature (>250 °C) solutions that also elevated the coal rank to anthracite grade. The assemblage of K-illite-paragonite-NH 4 -illite in the coals of the Hongmao deposit was formed under greater hydrothermal but less tectonic influence compared to the Luocheng deposit; by contrast, the pyrophyllite-illite-chlorite assemblage of the Luocheng deposit reflects a greater tectonic but lesser hydrothermal influence. Highlights • Rare earth elements in the anthracites have distinct positive Eu anomalies and medium- and heavy-REE enrichment types. • The minerals in the anthracites are characterized by the occurrence of K-illite, paragonite, and ammonian illite. • Paragonite and ammonian illite resulted from the alteration of kaolinite by hot solutions containing Na+ and NH 4 +. • Pyrophyllite in partings of coalbed formed by reactions between kaolinite and quartz during injection of high-T solutions. • The mineralogical and geochemical characteristics of the anthracites indicate the injection of high-T (>250 °C) solutions. [ABSTRACT FROM AUTHOR]

Thermal analysis of some sericite clays, from several deposits in Spain, which are not exploited at this time, has been studied. The samples have been previously characterized by mineralogical and chemical analysis. Sericite clays have interesting properties, with implications in ceramics and advanced materials, in particular concerning the formation of mullite by heating. According to this investigation by differential thermal and thermogravimetric analysis (DTA-TG), the sericite clay samples can be classified as: Group (I), sericite-kaolinite clays, with high or medium sericite content, characterized by an endothermic DTA peak of dehydroxylation of kaolinite with mass loss, which overlapped with dehydroxylation of sericite, and Group (II), sericite-kaolinite-pyrophyllite clays, with broader endothermic DTA peaks, in which kaolinite is dehydroxylated first and later sericite and pyrophyllite with the main mass loss, appearing the peaks overlapped. X-ray diffraction analysis of the heated sericite clay samples evidenced the decomposition of dehydroxylated sericite and its disappearance at 1050 °C, with formation of mullite, the progressive disappearance of quartz and the formation of amorphous glassy phase. The vitrification temperature is ~ 1250 °C in all these samples, with slight variations in the temperatures of maximum apparent density (2.41-2.52 g mL−1) in the range 1200-1300 °C. The fine-grained sericite content and the presence of some mineralogical components contribute to the formation of mullite and the increase in the glassy phase by heating. Mullite is the only crystalline phase detected at 1400 °C with good crystallinity. SEM revealed the dense network of rod-shaped and elongated needle-like mullite crystals in the thermally treated samples. These characteristics are advantageous when sericite clays are applied as ceramic raw materials. [ABSTRACT FROM AUTHOR]

Diasporic bauxite represents one of the major aluminum resources. Its upgrading for further processing involves a separation of diaspore (the valuable mineral) from aluminosilicates (the gangue minerals) such as kaolinite, illite, and pyrophyllite. Flotation is one of the most effective ways to realize the upgrading. Since flotation is a physicochemical process based on the difference in the surface hydrophobicity of different components, determining the adsorption characteristics of various flotation surfactants on the mineral surfaces is critical. The surfactant adsorption properties of the minerals, in turn, are controlled by the surface chemistry of the minerals, while the latter is related to the mineral crystal structures. In this paper, we first discuss the crystal structures of the four key minerals of diaspore, kaolinite, illite, and pyrophyllite as well as the broken bonds on their exposed surfaces after grinding. Next, we summarize the surface chemistry properties such as surface wettability and surface electrical properties of the four minerals, and the differences in these properties are explained from the perspective of mineral crystal structures. Then we review the adsorption mechanism and adsorption characteristics of surfactants such as collectors (cationic, anionic, and mixed surfactants), depressants (inorganic and organic), dispersants, and flocculants on these mineral surfaces. The separation of diaspore and aluminosilicates by direct flotation and reverse flotation are reviewed, and the collecting properties of different types of collectors are compared. Furthermore, the abnormal behavior of the cationic flotation of kaolinite is also explained in this section. This review provides a strong theoretical support for the optimization of the upgrading of diaspore bauxite ore by flotation and the early industrialization of the reverse flotation process. [ABSTRACT FROM AUTHOR]

The aim of this study has been to analyse the mineralogical and textural transformations of a set of aluminium-rich shales of interest for refractory and ceramic uses, fired from 800 °C to 1300 °C. To that end, raw and fired samples were analysed by X-ray diffraction, transmitted light microscopy, field emission scanning electron microscopy, and transmission electron microscopy. Raw samples comprise variable proportions of illite, pyrophyllite, orthoclase, quartz, kaolinite, mixed-layer I-Sm, and organic matter. At temperatures below 800 °C, kaolinite, mixed-layer I-Sm, and organic matter are destabilized, indicating that they are the least stable phases in the firing process. Illite, pyrophyllite, and orthoclase remain until 1000 °C and show a broader stability field during firing than in natural environments. Quartz persists throughout the entire firing process, although it is partly replaced by vitreous phase. Hematite crystallizes at 900 °C. Vitrification begins at 1000 °C, marking the first significant textural change. From 1000 °C mullite starts to crystallize from the Si- and Al-rich vitreous phase. The mullite composition is not stoichiometric and probably as temperature increases Si is partially replaced by Al, Fe and Ti in the structure. Nevertheless, with the increase of the firing temperature, the mullite composition is closer to the theoretical composition and also to that of natural mullites. Furthermore its crystal thickness increases with temperature up to 70 nm. [ABSTRACT FROM AUTHOR]

Microstructures, mineralogical composition and texture of selected landslide samples from three landslides in the southern part of the Gansu Province (China) were examined with optical microscopy, transmission electron microscopy (TEM), x-ray diffraction (XRD) and synchrotron x-ray diffraction measurements. Common sheet silicates are chlorite, illite, muscovite, kaolinite, pyrophyllite and dickite. Other minerals are quartz, calcite, dolomite and albite. In one sample, graphite and amorphous carbon were detected by TEM-EDX analyses and TEM high-angle annular dark-field images. The occurrence of graphite and pyrophyllite with very low friction coefficients in the gouge material of the Suoertou and Xieliupo landslides is particularly significant for reducing the frictional strength of the landslides. It is proposed that the landslides underwent comparable deformation processes as fault zones. The low friction coefficients provide strong evidence that slow-moving landsliding is controlled by the presence of weak minerals. In addition, TEM observations document that grain size reduction in clayey slip zone material was produced mainly by mechanical abrasion. For calcite and quartz, grain size reduction was attributed to both pressure solution and cataclasis. Therefore, besides landslide composition, the occurrence of ultrafine-grained slip zone material may also contribute to weakening processes of landslides. TEM images of slip-zone samples show both locally aligned clay particles, as well as kinked and folded sheet silicates, which are widely disseminated in the whole matrix. Small, newly formed clay particles have random orientations. Based on synchrotron x-ray diffraction measurements, the degree of preferred orientation of constituent sheet silicates in local shear zones of the Suoertou and Duang-He-Ba landslide is strong. This work is the first reported observation of well-oriented clay fabrics in landslides. [ABSTRACT FROM AUTHOR]

Zeolite synthesis has been achieved by alkaline treatment of a local clay, pyrophyllite. The chemical, textural and structural characteristics of the modified clay were evaluated and compared to those of the raw clay. The samples were characterized by X-ray fluorescence, nitrogen adsorption-desorption studies, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and thermoanalysis (TG-DSC). The pyrophyllite was converted to porous hydroxysodalite (HS), nearly pure, which has a surface area of 19.56 m2 g-1 with a spherical structure and cubic system. [ABSTRACT FROM AUTHOR]

The coal from the Jincheng Coalfield, Qinshui Basin, is a medium- to low-ash yield anthracite. The mineral assemblage in the anthracite is dominated by NH 4 -illite and kaolinite; with varying proportions of pyrophyllite, chlorite, pyrite, and calcite; and minor anatase, rutile, diaspore, florencite, and synchysite. Kaolinite formed during early diagenetic and epigenetic processes has been largely altered to other phyllosilicates by processes associated with the different stages of coal rank advance. The formation of NH 4 -illite in the Jincheng coals is the result of illitization of an early diagenetic kaolinite precursor by interaction of kaolinite with nitrogen derived from organic matter. This reaction may have occurred at the latest stage of bituminization (subbituminous to bituminous transition). Pyrophyllite was produced by the interaction of kaolinite and quartz formed by metamorphic processes associated with anthracitization. Cookeite is relatively common in the studied coals. It may have been derived from the reaction of kaolinite with Li ions, although the source of Li is not yet clearly understood. Minerals in the non-coal samples (partings and floor strata) appear to have responded differently to the metamorphic conditions than those in the adjacent coals. Possible mechanisms for the formation of NH 4 -illite in the Jincheng non-coal rocks at least involve isomorphous substitution of NH 4 for K in the K-illite structure. The well-crystallized K-illite in the non-coal rocks probably formed from detrital K-illite, and wasrecrystallized with the coal rank advance. Absence or minor proportions of pyrophyllite in non-coal samples may be due to a lack of epigenetic kaolinite in the non-coal horizons. Pyrophyllitization occurred during a late stage of metamorphism. The general absence of chlorite in the thick non-coal interval is probably due to the low permeability of that horizon, which resulted in a lack of infiltrating Fe- and Mg-bearing fluids. [ABSTRACT FROM AUTHOR]