Talc Samples Research Articles

An Early Neoproterozoic Accretionary Prism Ophiolitic Mélange from the Western Jiangnan Orogenic Belt, South China

AbstractThe Neoproterozoic Jiangnan orogenic belt delineates the suture zone between the Cathaysia and Yangtze blocks of the South China Craton. The western part of the belt, in the Longsheng region, consists of a disrupted mafic-ultramafic assemblage of pillow basalt, gabbro, diabase, and peridotite along with siliceous marble, ophicalcite, and jasper mixed with basalt. Significant talc deposits occur on the margins of the ultramafic bodies as well as in the transition zone between marble and basalt. Primary rock relations are largely overprinted by pervasive shearing, resulting in disruption of the assemblage into series of discontinuous blocks within a phyllite matrix. West-dipping thrust faults mark the eastern contact of blocks, and the overall succession has the appearance of a tectonic melange. U-Pb zircon age data from the gabbros and diabases yield crystallization ages of 867 ± 10, 863 ± 8, and 869 ± 9 Ma, with positive eHf(t) values. The gabbro, basalt, serpentinite, and some talc samples displa...

The Art of Talc Flotation for Different Industrial Applications

Talc has found a steadily increasing number of uses such as cosmetics, steatite and cordierite ceramics, for pitch control in the paper industry and as a reinforcing filler in rubber, etc. In this research, the amenability of some Egyptian carboniferous finely disseminated talc ores to beneficiation by flotation was investigated on laboratory scale. The original talc sample is characterized by low MgO content (25.40%), low SiO2 (45.71%), high CaO content (6.32%) and high L.O.I. (11.35%), indicating its low grade. Attrition scrubbing of the crushed ores was found to be an unconventional process, not only for fine talc production, but also for proper separation of the harder carbonaceous gangue. Talc pre-concentrates, less than 0.074 μm, were prepared by attrition scrubbing in the laboratory having 8.40% L.O.I. with a yield reaching 74.70%. Cleaner talc concentrate with L.O.I. content averaging 6.70% was obtained by flotation in the presence of Aerofroth 71 with a yield reaching 64.71%. This was relatively improved by the use of a selective (quaternary amine) talc collector and in presence of a selective carbonate depressant (soda ash). Flotation of the fine ground talc (less than 22 μm) produced a talc concentrate assaying 6.90% L.O.I. with a yield recovery of 62.91%. However, different talc concentrates obtained by just natural floatability or by the use of small dose of Aerofroth 71, or by the application of quaternary amine in presence of carbonate depressant, satisfy the requirement of paper coating, ceramics production, functional filler, and pharmaceuticals applications. Tailings could also be used in carpets, roofs, and tiles production industries.

Local and Extended-Order Evolution of Synthetic Talc during Hydrothermal Synthesis: Extended X-ray Absorption Fine Structure, X-ray Diffraction, and Fourier Transform Infrared Spectroscopy Studies

Synthetic talc is a new filler of industrial interest due to its submicron size, its chemical and mineral purity, and its hydrophilic character. To develop this filler on a preindustrial scale, this work aimed to understand the mechanisms of transformation from the amorphous talc precursor to crystalline synthetic talc. X-ray diffraction, Fourier transform infrared spectroscopy, and extended X-ray absorption fine structure at Ni–K edge techniques were used to study a Ni-talc series composed of a talc precursor sample and talc samples synthesized at 100, 200, and 300 °C for 1 or 6 h. As soon as the Ni-talc precursor precipitated, a tetrahedral–octahedral–tetrahedral-type structure appeared that was characterized by 2–3 Ni-octahedra distanced 3.07 A from each other and by 3–4 Si tetrahedra distributed on the top and bottom of the octahedral “sheet” and distanced 3.29 A from Ni. Simultaneously following the synthesis temperature, the octahedral sheet grew, and the tetrahedral sheet expanded; the distances Ni...

Thermoplastic starch/talc bionanocomposites. Influence of particle morphology on final properties

This work analyzed the effect of talc morphology on structural characteristics and final properties of thermoplastic corn starch (TPS). In this sense, composite films based on TPS containing talc nanoparticles were obtained by melt-mixing and thermo-compression. Talc samples with different morphological characteristics (platy-microcrystalline and blocky-macrocrystalline), derived from their formation process, were used. Platy and blocky morphology was distinguished by Scanning Electron Microscopy performed on composites films. Microcrystalline morphology induced smaller TPS crystallites than macrocrystalline one, indirectly evidenced by X-Ray Diffraction and Differential Scanning Calorimetry. Crystalline character of talc particles also affected visible and UV barrier capacity of TPS films. Blocky morphology of mineral filler led to the highest reduction of TPS water vapor permeation. Both talc samples acted as matrix reinforcement agents. However, macrocrystalline particles induced the major changes on elastic modulus and tensile strength, without affecting films ductility.

Effects of mechanical activation on the parameters of talc quality for ceramics production – Chemometric approach

Talc is broadly used in the ceramic materials industry, either as a basic raw material, or as filler, due to its chemical inertia, fragmentation proneness, thermal stability, and refractoriness. The mechanical activation is frequently employed in the direct enhancement of talc properties, and thereby in the design of talc based composites with advanced performances. The differences in the set of the process parameters measured before and after talc activation via ultra-centrifugal mill Retsch ZM-1, and their influence on the grain-size distribution related characteristics have been investigated. The mechanical treatments are energetically unsustainable procedures, therefore the talc activation was optimized on basis of assessment of the process variables (number of rotor revolutions, current intensity, activation period, circumferential rotor speed and mill capacity) effect on the final quality of product parameters (mesh sizes, cumulative oversizes, average grain size, level of micronization kinetics, mesh size appropriate to 95% micronized product cumulative undersize and specific surface area). The activated product parameters in all experimental sequences were obtained by the analytical procedure based on Rosin-Rammler-Sperling equation. Response surface method, standard score analysis and principal component analysis were used as a means of the optimization. Developed models showed r2 values in the range of 0.714–0.908 and they were able to accurately predict quality parameters in a wide range of process parameters. Standard score analysis highlighted that the optimal sample was obtained using sieve mesh of 120 μm set of processing parameters (SS = 1.0). Multiple comparison tests revealed that the optimal variation in the processing parameters could reduce the negative effect of talc samples inherent properties on the final score and improve the activation procedure energetic and economic sustainability.

Size-dependence hydrophobicity in nanocrystalline talc produced by high-intensity planetary ball milling

ABSTRACTMicron-size talc samples were ground using a high-intensity planetary ball mill at different milling times as an attempt to reduce particle size and study the effect on the corresponding hydrophobicity. XRD and SEM results confirmed the decrease in the particle size. FTIR spectroscopy analyses revealed the talc characteristic bands centered on 669 cm-1 for the O-H bonds and 1018 cm-1 for the Si-O bonds, as well as a degradation in the talc structure for prolonged milling times. BET results indicate an increase of specific surface area, which also confirms particle size reduction, reaching a maximum at 1 h, after which the particles agglomerate. Contact angle measurements show a decrease in the hydrophobicity of talc after milling. Although talc retains its hydrophobicity after short milling periods, prolonged grinding causes the mineral to have a more hydrophilic character.

Talc as raw material for cementitious products formulation

This study reports the characterization of a talc from Cameroon as a possible source material for cement formulation. To that end, the talc sample was characterized and mixed with a solution of sodium polyphosphate to formulate the cementitious products. Addition of magnesia (MgO) was done to analyze the effect of available MgO on the products. Fourier transform infrared, X-rays diffraction, linear shrinkage, compressive strength and scanning electron microscopy were used to analyze the products. The compressive strength increased with addition of MgO and the linear shrinkage decreased. All the analyses indicate that talc is a raw material of interest in cementitious products formulation; however, the inclusion of the MgO is a key factor for a better performance of the products.

Comparative analysis of cyanobacteria inhabiting rocks with different light transmittance in the Mojave Desert: a Mars terrestrial analogue

AbstractThe Mojave Desert has been long considered a suitable terrestrial analogue to Mars in many geological and astrobiological aspects. The Silver Lake region in the Mojave Desert hosts several different rock types (talc, marble, quartz, white carbonate and red-coated carbonate) colonized by hypoliths within a few kilometres. This provides an opportunity to investigate the effect of rock type on hypolithic colonization in a given environment. Transmission measurements from 300 to 800 nm showed that the transmission of blue and UVA varied between rock types. The wavelength at which the transmission fell to 1% of the transmission at 600 nm was 475 nm for white carbonate and quartz, 425 nm for red-coated carbonate and talc and 380 nm for marble. The comparative analysis of the cyanobacterial component of hypoliths under different rocks, as revealed by sequencing 16S rRNA gene clone libraries, showed no significant variation with rock type; hypoliths were dominated by phylotypes of the genusChroococcidiopsis, although less abundant phylotypes of the genusLoriellopsis, LeptolyngbyaandScytonemaoccurred. The comparison of the confocal laser scanning microscopy-λ (CLSM-λ) scan analysis of the spectral emission of the photosynthetic pigments ofChroococcidiopsisin different rocks with the spectrum of isolatedChroococcidiopsissp. 029, revealed a 10 nm red shift in the emission fingerprinting for quartz and carbonate and a 5 nm red shift for talc samples. This result reflects the versatility ofChroococcidiopsisin inhabiting dry niches with different light availability for photosynthesis.

Investigation of the Thermal Decomposition of Talc

AbstractDifferent changes in the structural and thermal properties of various types of talc have been reported in the literature which have made comparison of analytical results difficult. The objective of the present study was to obtain some fundamental insights into the effects of the thermal behavior of talc and to carry out kinetic analyses of the decomposition of talc under high temperature. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetry-differential scanning calorimetry (TG-DSC) were used to study the thermal decomposition mechanism. The Coats-Redfern decomposition model was used to determine the decomposition mechanism of talc samples. The results showed that the decomposition of talc commenced at ~800°C, peaking at ~895°C, with the formation of enstatite and amorphous silica. An isothermal treatment at 1000°C caused the complete dehydroxylation of talc. The XRD and FTIR results indicated that the enstatite and amorphous silica phases were transformed into clinoenstatite and paracrystalline opal phases, respectively, after the decomposition stage at 1200°C. Good linearity in the Coats-Redfern model was observed from room temperature to 1300°C and the activation energy was calculated to be 69 kcal/mol.

Quantitative analysis of trace level asbestos in pharmaceutical talc by powder X-ray diffraction

As a traditional Chinese medicine and excipient, talc is widely used in medical and pharmaceutical fields. It may be contaminated with asbestos (including tremolite and chrysotile). Asbestos is known to be a carcinogen and it can cause lung cancer. Therefore, it is important to determine the concentration of asbestos in talc. This paper reports the use of powder X-ray diffraction (PXRD) technology to establish a trace level concentration detection of asbestos in traditional medicinal talc at 0.3 to 0.8%. The results show that the method is reliable, sensitive and suitable for its intended use of detecting trace levels of asbestos in the talc. Among the fifty-four talc samples, nine of them were found to contain asbestos and were disqualified. The passing rate of the test is 83.3%, which means it is necessary to establish an effective method to determine trace level asbestos in talc.

Comparative kinetic study of mechanical activation process of mica and talc for industrial application

Mica and talc have wide areas of application as a raw material in a number of industrial branches. Mechanically activated mica has specific applications such as: capacitors, insulators, and pearlescent pigments. Talc is widely used as either a basic raw material or as filler. This paper presents a comparative analysis of mechanically activated samples of mica and talc in ultra-centrifugal mechano-activator “Retsch ZM-1”. The following mechano-activator parameters were variable: number of rotor revolutions (rpm); sieve mesh size (μm); current intensity (A). In addition, the following parameters were monitored: duration of mechanical activation, t (min); circumferential rotor speed, v (m/s); capacity of mechano-activator, Q (kg/h); and specific energy consumption, We (kWh/t). It was observed that effect of mechanical activation of mica and talc increased with an increase of the load and rotor revolution of ultra-centrifugal mechano-activator. Both mica and talc were successfully treated by mechanical activation procedure. In the processing of mica, mechanical activation is suggested to be applied as a post-treatment, and in the talc processing as a pre-treatment, as the high quality talc is obtained by means of hydrometallurgical concentration method.

Use of talc as low-cost clarifier for wastewater

Talc is proposed as a low-cost mineral for wastewater clarification. In this sense, adsorption of methylene blue (MB) from aqueous solutions was studied comparatively by using sepiolite (qualified as very good adsorbent) and two talc samples with different particle size and purity degree. The MB adsorption was assessed by determining remnant dye in the supernatant using UV-vis spectroscopy and by detecting dye adsorbed on mineral samples through thermogravimetric analysis and infrared spectroscopy. Both isothermal curves and kinetic studies demonstrate that talc is a good dye adsorbent. Particularly, with dye concentrations similar to those of textile wastewater, talc was demonstrated to adsorb the same dye content of sepiolite at similar times. Natural talc could be employed as a low-cost alternative in wastewater treatment for the removal of cationic dyes.

Kinetic features of the adsorption of sodium oleate on talc

Kinetic features of the adsorption of sodium oleate on dispersed talc samples of Onotskoe deposit are studied. It is shown that adsorption proceeds in two steps with different rate constants of adsorption ka and desorption kd. It is found that at the first step, lasting for nearly one hour under experimental conditions, the process is characterized by high ka and kd values (1.23 × 10−2 m2/(mol min) and 1.06 × 10−5 m2/(L min), respectively). It is concluded that the final stage associated with the rearrangement of molecules on a talc surface lasts for a long time with ka = 2.12 × 10−3 m2/(mol min) and kd = 1.82 × 10−6 m2/(L min).

Influence of talc morphology on the mechanical properties of talc filled polypropylene

Injected polypropylene (PP)/talc composites were studied to evaluate the influence of different talc morphologies on their final mechanical properties. Talc genesis is responsible for type and content of associated minerals, crystalline degree, particle size distribution, and specially, morphology. Consequently, when talc is incorporated into PP, differences in the genesis mean differences in particle morphology and may influence the composite properties. Two talc samples having predominant macro and microcrystalline morphologies were used to prepare two composite sets to be tested. Thermal and mechanical properties of each PP/talc composites set were measured, analyzed and discussed comparatively. The results reveal that the main influences of talc morphology are given on modulus, yield strength and elongation at break of PP/talc composites. Macrocrystalline morphology of talc induces better composite mechanical properties than microcrystalline one. This behavior could be explained by talc characteristics as lamellarity, crystalline character and crystallinity degree.

Pneumoconiosis and malignant mesothelioma in a family operated metal casting business that used industrial talc from New York state

The United States is second only to the People's Republic of China in annual talc production. U.S. talc is used in the production of ceramics, paint, paper, plastics, roofing, rubber, cosmetics, flooring, caulking, and agricultural applications. A number of U.S. talc deposits consistently contain talc intergrown with amphiboles such as tremolite and/or anthophyllite. It has long been recognized that miners and millers of talc deposits are at risk for pneumoconiosis and it has recently been reported that it is prudent, on the balance of probabilities, to conclude that dusts from New York State talc ores are capable of causing mesothelioma in exposed workers. This is a report of the diagnosis of pneumoconiosis and mesothelioma in a husband and wife who operated a small metal casting business that used industrial talc from New York as a parting agent. Case reports, including medical records and exposure histories, were provided by an attorney who had also commissioned laboratory investigation of the industrial talc product used in the factory. Mrs X was diagnosed with pneumoconiosis characterized by interstitial fibrosis and heavily calcified pleural plaques. Mr X had calcified pleural plaques and developed a fatal pleural mesothelioma. Samples of the industrial talc contained fibrous tremolite and anthophyllite. The author concludes that end users of industrial talc from New York State may be at risk of pneumoconiosis and malignant disease. End users of talcs from other regions of the United States, where talc formation arose from processes driven by regional metamorphism, might also be at risk.

Zenginleştirilmemiş Talkin Duvar Karosu Massesinde Kullanilabilirliğinin Araştirilmasi

In this study, the talc sample obtained from Domanic (Kutahya) region of Turkey together with the raw materials used for making fast and single-fired wall tile are studied by the use of various prescriptions concerning the effects on the technical features of several properties. The samples prepared under laboratory conditions are shaped with pressing method and fired at 1130 °C. The chemical compositions, granule dimensions and moisture content of talc and spray dried granules are determined. Thermo gravimetric and differential thermal analysis of the powder of these materials which were prepared based on the prescriptions are done. Water absorption, fired strength, fired shrinkage, true density, X-Ray diffraction analysis and scanning electron microscope analysis of sintered samples are done. To sum up, it was observed that the fired strength of the wall tile bodies with 15 % talc addition was increased by 1.07 times whereas water absorption value was decreased by 16.22 %. In this respect, it is apparent that these values are well-matched and in accordance with TS EN 14411:2008

Phase transformations of a talc ore under heated chlorine atmosphere

The effect of Cl2 on the phase transformations of the minerals present in a talc (Mg3Si4O10(OH)2) unpurified with clinochlore (Mg5Al2Si3O10(OH)8), magnesite (MgCO3), dolomite (MgCa(CO3)2), hematite (Fe2O3) and pyrite (FeS2) was studied with the purpose of deferricating the mineral and obtaining protoenstatite (MgSiO3), which is the basic component of steatite ceramics. Isothermal and non-isothermal assays in N2 and Cl2–N2 atmospheres were performed using a thermogravimetric device at temperatures between 600 and 980°C. The reagents and the products were analyzed by differential thermal analysis (DTA), X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Results obtained showed that the following phenomena were produced in Cl2: (a) The transformation of vitreous silica (SiO2), from the chlorination reaction of talc, into enstatite (MgSiO3) started at about 700°C, being dolomite the mineral that favored this reaction. At 800°C, more enstatite was formed as a result of the reaction between vitreous silica not transformed, MgCl2 and O2 derived from the chlorination of dolomite and magnesite; then, polymorphic transformation of enstatite into protoenstatite was produced. (b) At about 950°C, CaCl2 produced as a result of dolomite chlorination led to the destruction of the protoenstatite structure, and to the subsequent formation of cristobalite, with release of O2 and gaseous MgCl2. (c) The elimination of iron as FeCl3(g) takes place in all the temperature interval investigated. The most favorable chlorination temperature was 900°C, since protoenstatite structure was destroyed at higher temperatures and an efficient elimination of iron present in the talc sample was not possible at lower temperatures.

The effect of impurities and cleavage characteristics on talc hydrophobicity and polymer adsorption

We have investigated three natural talc samples from different geographical locations (Rhode Island (USA), Delaware (USA), and Flinders Range (Australia)) to determine the effect of impurities and cleavage characteristics on hydrophobicity and polymer adsorption. Bulk (electron microprobe) and surface (X-ray photoelectron spectroscopy) composition measurements have indicated that the Rhode Island and Delaware talcs have the lowest level of Al atoms substituted within the talc structure (0.008%), and detectable at the cleaved basal plane surface (1.5 and 1.7%), and that the Flinders Range talc has the highest level of Al atoms (8.5% bulk; 8.2% surface). Contact angle measurements have highlighted the role of Al atom substitution and step-edge density (as revealed by AFM imaging) on the measured hydrophobicity of the cleaved surfaces, with the Flinders Range talc and the Rhode Island talc having significantly lower contact angles than the Delaware talc (65° and 83°, respectively, versus 90° for the Delaware). In addition, we have characterised the adsorption of two polysaccharide polymers on the three talc samples (CMC and Dextrin TY) using in situ tapping mode AFM. CMC adsorbs with the same morphology on all three talc samples, whereas Dextrin TY presents three different morphologies on the talc surfaces. The potential implications of the observed variation in adsorption behaviour on mineral flotation are discussed.

Production of Nano Talc Material and Its Applicability as Filler in Polymeric Nanocomposites

In the present work, focus is on the production of nano-sized talc particles in a stirred ball mill and their nano talc particles incorporated in the polyamide-6 polymer matrix to form polyamide/talc nanocomposite. The results show that enhancement in the polyamide/talc nanocomposite strength properties such as flexural and tensile strength. The production of nano talc particles is difficult process in wet grinding system; however, the minimum achievable particle size is strongly influenced by the suspension stability. Hence, prior to the wet milling, it is imperative to conduct the ζ potential measurements on the talc sample in order to find out at which pH range a strong repulsive force between the given talc sample particles exists. The desired electrostatic repulsion force is maintained by the adjustment of pH 11 in wet milling. The experiments are conducted at pH 11 conditions which were maintained constant throughout the experiments and nanosized talc particles are obtained consequently.

Hydroxyl stretching in phyllosilicates at high pressures and temperatures: an infrared spectroscopic study

The hydroxyl stretching frequencies of four phyllosilicates have been measured at high pressures and temperatures using an externally heated diamond-anvil cell and synchrotron infrared spectroscopy. Spectra were measured up to 26, 31, 21 and 8 GPa at room temperature for samples of talc, pyrophyllite, muscovite and 10-A phase, respectively. Spectra were also measured in the range 273–500 K at ambient pressure for all samples and at 8–9 GPa for talc and pyrophyllite. The frequency of the Mg3OH band in talc increases with pressure due to the absence of hydrogen bonding. The different orientation of the hydroxyl group in pyrophyllite and muscovite leads to hydrogen bonding and a decrease in the frequency of the Al2OH band with pressure. 10-A phase is approximately equivalent to talc with the addition of interlayer H2O. In a spectrum of a sample synthesised for 143 h, two hydroxyl stretching bands are clearly resolved on compression. One is the same as the Mg3OH band in talc, indicating the presence of intra-layer hydroxyl in a talc-like environment with no hydrogen bonding. The other, which separates from the talc-like band at 1 GPa, is associated with intra-layer hydroxyl that is hydrogen bonded to interlayer H2O. There are equivalent bands in high-pressure spectra of a sample of deuterated 10-A phase, synthesised for 400 h. This sample shows a greater extent of hydrogen bonding at ambient pressure than the 143 h sample. For all of the phases studied, increasing temperature leads to a decrease in frequency for every hydroxyl stretching vibration, both at low and high pressures. The shifts in frequency with temperature are an order of magnitude greater than the shifts with pressure when normalised to previously measured structural parameters.