Synthesis and characterization of analcime (ANA) zeolite using a kaolinitic rock

Analcime is nowadays an important component in dental porcelain systems, in heterogeneous catalysis, in the nanoelectronic feld, in selective adsorption and in stomatology (dental flling and prosthesis). Analcime synthesis from an impure, silica-rich kaolinite rock coming from Romana (Sassari, Italy) is here presented. A synthesis protocol is proposed that aims to make an improvement of synthesis conditions compared to the past. The hydrothermal treatment is in fact here achieved without aging times and without the use of sodium silicate or other additional silica source reported in the literature. Lower calcination temperature, synthesis temperature and crystallization time are verifed in this work. The kaolin is subjected to calcination at the temperature of 650 °C and then mixed with NaOH. The experiment is performed at ambient pressure and 170± 0.1 °C. The degree of purity of analcime is calculated in 97.57% at 10 h. Analcime is characterized by X-ray difraction, infrared spectroscopy, scanning electron microscopy, inductively coupled plasma optical emission spectrometry and thermal analysis. Density is also calculated. Cell parameters and the amount of amorphous phase in the synthesis powders is estimated with quantitative phase analysis using the combined Rietveld and reference intensity ratio methods. The experimental conditions make the synthesis protocol particularly attractive from an economic point of view. Also this work does not use a commercial kaolin but silica-rich impure kaolinitic rock from a disused quarry. This further reduces the costs of the experimental protocol. It also gives the protocol an added value, as the synthesis of a useful mineral is obtained through the valorization of an otherwise unused georesource. Both chemical and physical characterization of analcime is satisfactory making the experimental protocol very promising for an industrial transfe

Synthesis and characterization of wollastonite-2M by using a diatomite precursor

Solid phase reaction synthesis of wollastonite-2M by a natural rock precursor as the source of amorphous silica and CaCO3 is reported. Chemical treatments were carried out on a diatomitic rock from Crotone (Calabria, Italy) in order to measure its reactive silica and CaCO3 contents. Four series of synthesis were performed at 1000°C at ambient pressure by mixing, at different stoichiometry, the diatomitic rock with a natural limestone as a source of additive CaCO3, and sodium carbonate (Na2CO3) as triggering agent. Wollastonite-2M was characterized by chemo-physical, crystallographical and morphological-microtextural analyses. All these characterizations, together with infrared and nuclear magnetic resonance (29Si) responses provide values comparable to literature data. Estimation of the amorphous phase in the synthesis powders was performed through quantitative phase analysis using the combined Rietveld and reference intensity ratio methods, resulting in a final product of 96.3% wollastonite-2M

Synthesis and characterization of Leucite using a diatomite precursor

Leucite is nowadays an important component in ceramic restoration systems with particular suitability to dental porcelains. The leucite synthesis from a hydrothermally-derived precursor is here presented. A silicate solution was prepared by mixing a naturally derived amorphous silica (diatomitic rock from Crotone, southern Italy) with potassium hydroxide and an aluminate solution was obtained by mixing aluminium hydroxide and potassium hydroxide. Three mixtures of varying ratios of aluminate and silicate solutions were prepared and submitted to hydrothermal treatment at 150 °C for one hour. Subsequently these hydrothermal precursors were subjected to calcination at the temperature of 1000 °C for variable time intervals, thus resulting in 3 series of syntheses. The synthesis run 3 turned out to be the best from the point of view of temporal yield showing the crystallization of the leucite after only 15 hours of heat treatment. The products of synthesis run 3 were fully characterised by Powder X-Ray Diffraction, Inductively Coupled Plasma Optical Emission Spectrometry, Infrared Spectroscopy and Thermal Analysis. The amorphous phase in the synthesis powders was estimated by quantitative phase analysis using the combined Rietveld and reference intensity ratio methods. Density of leucite was also achieved by He-pycnometry. The use of a cost effective starting material such as a diatomite in the experimental route makes the process highly attractive for expansion to an industrial scale especially considering that both the chemical and physical characterizations of our leucite product are highly satisfactory. Last but not least we explain some inferences that can be obtained from this process of synthesis in order to a better understanding of some natural occurrences of leucite in geologic systems related to basaltic magmas

Synthesis and characterization of Na‑P1 (GIS) zeolite using a kaolinitic rock

This work focuses on the hydrothermal synthesis of Na-P1 zeolite by using a kaolinite rock coming from Romana (Sassari, Italy). The kaolin is calcined at a temperature of 650 °C and then mixed with calculated quantities of NaOH. The synthesis runs are carried out at ambient pressure and at variable temperatures of 65 and 100 °C. For the first time compared to the past, the Na-P1 zeolite is synthesized without the use of additives and through a protocol that reduces both temperatures and synthesis times. The synthesis products are analysed by X-ray diffraction, high temperature X-ray diffraction, infrared spectroscopy, scanning electron microscopy and inductively coupled plasma optical emission spectrometry. The cell parameters are calculated using the Rietveld method. Density and specific surface area are also calculated. The absence of amorphous phases and impurities in synthetic powders is verified through quantitative phase analysis using the combined Rietveld and reference intensity ratio methods. The results make the experimental protocol very promising for an industrial transfer

Myoepithelioma of the parotid gland: A case report with review of the literature

Myoepithelioma is a rare tumor of the salivary glands belonging to a distinct category of neoplasms according to World Health Organization. It represents about 1% of all tumors that develop in the salivary glands. Generally the majority of myoepitheliomas are benign but malignant transformation can take place in untreated or recurrent cases. We present a case of a rare myoepithelioma of the left parotid gland, with review of literature. Keywords: Parotid gland, Salivary glands myoepithelioma, Benign salivary glands tumors, Myoepithelioma, Spindle cells myoepitheliom

A Rare Case of Traumatic Ulcerative Granuloma with Stromal Eosinophilia of the Tongue (Tugse) in a Child: Diagnostic Problems and Differential Diagnosis

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Pyrometamorphism in calc-silicate xenoliths of the Monte Ulmus pyroclastic comenditic unit, SW Sardinia, Italy: mineralogical and isotopic characterization

Las rocas miocenas de la base de la unidad comendítica de Monte Ulmus (vitrófiro basal negro e ignimbrita rosa) han proporcionado una abundante y ubicua presencia de xenolitos de rocas carbonáticas pirometamorfizadas. La paragénesis presente sugiere un episodio progradante y uno retrogradante (siendo éste producido por el enfriamiento post-emplazamiento de las rocas piroclásticas) que dan una idea (en especial el retrógrado) de la (rápida) cinética de los procesos de reacción. Los datos de isotopía del Sr confirman, una vez comparados con los de los principales afloramientos del substrato de la región del Sulcis, que un protolito cámbrico está implicado en la génesis de los xenolitos en la parte superior de una cámara magmáticaThe Miocene pyroclastic rocks at the base of the comenditic Monte Ulmus unit (black vitrophyre and pink ignimbrite) have yielded a ubiquitous and abundant population of xenoliths of pyrometamorphosed calcareous rocks coming from the substrate. The paragenesis suggests a prograde and a retrograde episode (the latter clearly related to the postemplacement cooling of pyroclastic unit), and gives an idea of the (quick) kinetics of reaction processes. The Sr isotope data, by comparison to those of the main carbonatic outcrops of the Sulcis area, confirm that a Cambrian protolith is involved in the genesis of xenoliths at the upper part of a magmatic chambe

Improvement in the synthesis conditions and characterizations of the zeolite Li-A(BW) obtained from a kaolinitic rock

Crystallization of zeolite Li-A(BW) from kaolinite (Standard Porcelain by the IMERYS Minerals Ltd) through a conventional hydrothermal treatment is here achieved for the first time with no additives as reported in the literature. Moreover lower kaolin calcination temperatures and lower synthesis temperatures are tested and verified in this work. The synthesis process is rather simple as the reaction of kaolinite with alkali occurs very readily after calcination of at 650 °C. Metakaolin is mixed with calculated amount of aluminum hydroxide and lithium hydroxide and the experiment is performed at ambient pressure and 180 ± 0.1 °C. Li-A(BW) is characterized by powder X-ray diffraction, high temperature X-ray diffraction, scanning electron microscopy, inductively coupled plasma optical emission spectrometry, thermal analysis and infrared spectroscopy. Calculation of cell parameters (through Rietveld Refinement) and density, specific surface and pore size are also achieved. The amount of amorphous phase in the synthesis powders is estimated with quantitative phase analysis using the combined Rietveld and reference intensity ratio methods. The results become notably attractive in view of a possible industrial transfer of the synthesis protocol