Vibrational spectroscopy of acid treated vermiculites

The natural vermiculites from different localities (Bulgaria, Brazil, and South Africa) after acid treatment were used for this study. Differently acidified vermiculite samples were prepared from the natural vermiculite sample using different concentrations of hydrochloric acid (0.5 M and 1 M) and different reaction time (2 h and 4 h) at 80 °C. Natural vermiculites and acid treated vermiculites were analyzed by elemental analysis, X-ray diffraction (XRD) analysis and studied using Fourier transform infrared (FTIR) spectroscopy and dispersive Raman spectroscopy. According to the XRD analysis vermiculites are interstratified structures created in the different two-one-zero sheet hydrated phases. Ratio of intensities of spectrally deconvoluted bands at 1075 cm−1 and 1000 cm−1 (stretching vibration of Sisingle bondO bonds of vermiculites and stretching vibration of Sisingle bondO bonds of amorphous silica, respectively) was used to determine the content of amorphous silica in acid treated vermiculite samples. Study of the infrared and Raman spectra of the acidified vermiculites enable a comparison of these two spectroscopic data that have not yet been performed.Web of Science70696

Analysis of clay minerals with high content of intercaled elements by X-ray fluorescence spectrometry

Import 29/09/2010Tato diplomová práce se zabývá vývojem metody pro přesné stanovení stříbra v jílových minerálech (vermikulit a montmorillonit) interkalovaných stříbrem metodou rentgenové fluorescenční spektrometrie. Vzhledem k nedostupnosti referenčních materiálů jílových minerálů s vysokým obsahem Ag musely být připraveny vlastní referenční materiály. Byla použita metoda tavenin vzorků s tetraboritanem litným. Pomocí těchto referenčních materiálů byly sestrojeny dva kalibrační modely pro XRFS, které vykazovaly lineární průběh. Poté byly pomocí nových kalibračních modelů proměřeny reálné vzorky interkalované stříbrem a bylo zjištěno, že nově vytvořené metody jsou vhodné pro stanovení stříbra ve vzorcích.This diploma thesis deals with development of method for precious determination of silver content in clay minerals (vermiculite, montmorillonite) intercalated with silver. To analyze all prepared samples was used x-ray fluorescence spectrometry. Due to the unavailability reference materials of clay minerals with a high silver content were prepared by their own highly homogenous reference materials. Method was used to melt the samples with di-lithium tetraborate. With those of reference materials were constructed two calibration models for XRFS. Using the new calibration models were measured real samples intercalated with silver and was demonstrated, that newly created methods for determination of silver are suitable for determination of silver content in samples.615 - Katedra analytické chemie a zkoušení materiáluvýborn

Identifikace a stanovení sulfokyselin v odpadních vodách po nitraci

Import 31/07/2008Prezenční615 - Katedra analytické chemie a zkoušení materiáluNeuveden

Role of vermiculite and zirconium-vermiculite on the formation of zircon-cordierite nanocomposites

The Zr4 +–vermiculites were studied in their new role of the zircon precursor in the clay minerals mixtures which were prepared for firing of the zircon–cordierite nanocomposites. Currently there is a lack of data available about the structure of Zr4 +–vermiculites, on which this study was performed. The modeling of the arrangement of interlayer material in the Zr4 +–vermiculite led to new findings that water molecules are attracted more strongly by Mg2 + cations than by Zr-tetrameric cations, and that both the tetrameric cations [Zr4(OH)14(H2O)10]2 + and [Zr4(OH)8(H2O)16]8 + may be present in the interlayer space of the Zr4 +–vermiculites. Vermiculites from two different localities Czech Republic (Verm1) and from Brazil (Verm2) were intercalated using the zirconyl chloride (ZrOCl2–30% solution in HCl) and the prepared Zr4 +–vermiculites were designated as Zr4 +–Verm1 and Zr4 +–Verm2, respectively. Influence of the Zr4 +–Verm1 and Zr4 +–Verm2 in the mixtures of clay minerals on the properties of zircon–cordierite nanocomposites were investigated by their comparison with the properties of the zircon–cordierite nanocomposites, which were prepared using saturation of the clay minerals mixtures containing Verm1 and Verm2 with the zirconyl chloride (ZrOCl2–30% solution in HCl). The zircon–cordierite nanocomposites fired from the clay mineral mixtures containing Zr4 +–Verm1 and Zr4 +–Verm2 showed a maximum porosity of P = 58 and 60%, skeletal density SD = 3.2 and 3.6, and the smallest pores with a median pores diameter MDP = 18 and 15 μm, respectively, in comparison with the zircon–cordierite nanocomposites fired from the clay mineral mixtures containing Verm1 and Verm2 and saturated with zirconyl chloride solution. The type of vermiculite Verm1 or Verm2 in the clay mineral mixtures did not affect the contents of the crystalline mineral phases in cordierite and zircon–cordierite nanocomposites.Web of Science75-7610810

Cordierite composites reinforced with zircon arising from zirconium-vermiculite precursor

The paper aimed with four forms of cordierite and cordierite–zircon ceramic composites prepared via sintering of the pre-ceramics clay mineral mixtures containing vermiculite (V) and zirconium–vermiculite (Zr–V) without the use of long-term grinding procedures. Precursor of zircon in cordierite was Zr–V prepared from V and zirconium salt solution via cation exchange. Cordierite composites containing pure cordierite phase were sintered from the clay mineral mixtures. Cordierite composites composed of spinel and enstatite or forsterite at the expense of cordierite were prepared from the clay mineral mixtures and Al2O3 or MgO. The additives contributed to the development of pores that size about 5 μm. Zircon crystals with a size ranging from 150 nm to 1 μm were irregularly distributed on the cordierite matrix surface. Cordierites reinforced with zircon in comparison to their parent cordierites showed a lower porosity and higher hardness values.Web of Science8016115

Structural characteristics of cordierite/steatite ceramics sintered from mixtures containing pore-forming organovermiculite

The preceramic mixtures appropriate to the composition of cordierite are composed of talc, kaolinite and vermiculite (Ver), and/or organovermiculite (Ver-org) as a pore-forming agent. The preceramic mixtures for sintering at 1300 °C were prepared in two different ways, loosely in crucibles and compressed into pellets. Structural characterization of cordierite/steatite ceramic was performed using X-ray powder diffraction (XRD), FTIR spectroscopy, scanning electron microscopy analysis and porosity measurement. The ceramic samples showed (1) bimodal meso-macropore size distribution and unimodal macropore size distribution, when the preceramic mixtures included Ver and Ver-org, respectively, and (2) higher porosity when sintering mixtures occurred in crucibles in comparison with pellets. The XRD patterns and quantitative XRD phase analysis revealed cordierite/steatite ceramics in the composition of indialite (IND) and two orthorhombic forms of enstatite: protoenstatite (PEN) and orthoenstatite (OREN). All cordierite/steatite samples contained a greater amount of PEN than OREN and a slightly higher quantity of IND when sintered in crucibles compare to pellets. The ceramic samples prepared from the preceramic mixtures with twice the amount of Ver-org contained a high quantity of IND (91 vol%), PEN (about 9 vol%) and no OREN. The unit cell parameter c in comparison with the pure IND was about 0.001–0.003 nm shorter at all INDs. The pore-forming Ver-org supports structural substitution of cations during crystallization of IND with the substitution Ca0.50Mg1.50–Ca0.25Mg1.75. The IR spectra in the 400–1600 cm−1 region confirmed the presence of cordierite and steatitWeb of Science4010157251571

Structural variability of high purity cordierite/steatite ceramics sintered from mixtures with various vermiculites

The cordierite/steatite ceramics were prepared from the pre-ceramic clay mineral mixtures containing talc, kaolinite and unconventionally used vermiculite. The aim was to characterize cordierite/steatite ceramics in relation to the vermiculites in the pre-ceramic mixtures and compare the influence of their sintering, loosely in crucibles and pressed into pellets. Quantitative X-ray diffraction (XRD) analysis revealed approximately a 5 vol% lower content of indialite (IND) sintered in pellets than in crucibles, and protoenstatite (PEN) slightly prevailing over orthoenstatite (OREN) at all ceramic samples. All ceramic samples showed linear dependency of porosity on the increasing content of potassium and sodium in structure of vermiculites. Highest porosity, 55%, was detected for sample in crucible made of vermiculite admixture from Letovice region (CR) and the smallest porosity 0.25% was in a sample in pellets made of vermiculite admixture from the Xinlong deposit (China).Web of Science4068498848