Thermal decomposition and X-ray diffraction of sulphate efflorescent minerals from El Jaroso Ravine, Sierra Almagrera, Spain

Two evaporite minerals from the El Jaroso Ravine, Spain have been analysed by thermogravimetry coupled with an evolved gas mass spectrometer. X-ray diffraction results proved the evaporite minerals were a mixture of sulphates including the minerals magnesiocopiapite, coquimbite and possibly alunogen. Thermal decomposition of the unoxidised samples showed steps at 52, 99 and 143 °C confirmed by mass spectrometric results and attributed to adsorbed water, interstitial water and chemically bonded water. This evaporite mineral rock showed two higher temperature decomposition steps at 555 and 599 °C with mass losses of 19.6 and 7.8%. Slightly different temperatures for the thermal decomposition of the oxadada sample were observed at 52, 64.5 and 100 °C. Two higher temperature mass loss steps at 560.5 and 651 °C were observed for the oxidised sample. By comparison of the thermal analysis patterns of halotrichite and jarosite it can be shown that the El Jaroso samples are mineral sulphates and not halotrichite or jarosite.     

Effects of solid acidity of clay minerals on the thermal decomposition of 12-aminolauric acid

In this study, the effects of four types of clay minerals on the thermal decomposition of 12-aminolauric acid (ALA) were investigated. The decomposition temperature of ALA in ALA–clay complexes was in the range of 200–500 °C. The derivative thermogravimetry results indicated that all clay minerals exhibited catalytic activity on the decomposition of ALA. Pure ALA decomposed at approximately 464 °C, a temperature higher than the decomposition temperature of ALA in the presence of clay minerals. The decomposition temperature of ALA in different ALA–clay complexes follows the order illite (452 °C) > kaolinite (419 °C) > rectorite (417 °C) > montmorillonite (400 °C). This order is negatively correlated with the amounts of solid acid sites in the clay minerals, indicating that ALA is catalyzed by the solid acid sites in these minerals.     

Thermal stability of artinite, dypingite and brugnatellite—Implications for the geosequestration of green house gases

The approach to remove green house gases by pumping liquefied carbon dioxide several kilometres below the ground implies that many carbonate containing minerals will be formed. Among these minerals the formation of dypingite, artinite and if the ferric iron is present brugnatellite are possible; thus necessitating a study of the thermal stability of such minerals. The thermal stability of two carbonate bearing minerals dypingite and artinite together with brugnatellite with a hydrotalcite related formulae have been characterised by a combination of thermogravimetry and evolved gas mass spectrometry. Artinite is thermally stable up to 352 °C. Two mass loss steps are observed at 219 and 355 °C. Dypingite decomposes at a similar temperature but over a large number of steps. Brugnatellite shows greater stability with decomposition not occurring until after 577 °C. The thermal decomposition of brugnatellite occurs over a number of mass decomposition steps. It is concluded that pumping liquefied green house gases into magnesium bearing mineral deposits is feasible providing a temperature of 350–355 °C is not exceeded to prevent escape of CO₂ towards the surface. In contrast, the water loss occurring at lower temperatures could have a positive effect on the geosequestration of CO₂ as it probably causes a decrease in the molar volume of secondary carbonate minerals and consequently an increase in aquifer porosity.     

Thermogravimetric analysis of selected group (II) carbonateminerals — Implication for the geosequestration of greenhouse gases

The precursors of carbonate minerals have the potential to react with greenhouse gases to form many common carbonate minerals. The carbonate bearing minerals, magnesite, calcite, strontianite and witherite, were synthesised and analysed using a combination of thermogravimetry and evolved gas mass spectrometry. The DTG curves show that as both the mass and the size of the metal cationic radii increase, the inherent thermal stability of the carbonate also increases dramatically. It is proposed that this inherent effect is a size stabilisation relationship between that of the carbonate and the metal cation. As the cationic radius increases in size, the radius approaches and in the case of Sr²⁺ and Ba²⁺ exceeds that of the overall size of the carbonate anion. The thermal stability of these minerals has implications for the geosequestration of greenhouse gases. The carbonates with the larger cations show significantly greater stability.     

Syntheses and spectroscopic characterization of uranium(VI) silicate minerals

In this study, the secondary uranium(VI) silicate minerals boltwoodite, sodium boltwoodite and uranophane were synthesized. Sodium boltwoodite was successfully obtained by the following new reaction procedure. Their analytical characterization was carried out by means of inductively coupled plasma mass spectrometry and atomic absorption spectroscopy, scanning electron microscopy, X-ray powder diffraction, differential thermal analysis combined with thermogravimetry and infrared spectroscopy. Furthermore, the fluorescence behaviour was measured using time-resolved laser fluorescence spectroscopy. Herewith, the fluorescence properties of the three silicious uranyl phases were determined at room temperature.     

Comparative study of three different kinetic models applied to the ageing of archaeological beeswax used as a paint medium

Kinetic evaluation of thermogravimetry data was used to understand the ageing behavior of beeswax used as an artists’ paint medium on ancient mummy shrouds and Fayum portraits. Individual components of beeswax were subjected to dynamic thermogravimetry to assess their evaporation rates, and three methods of kinetic analysis were evaluated for accuracy. The results showed that although it is impossible to accurately predict the volatility at room temperature for individual components of beeswax due mostly to their high molecular mass, relative trends and ranking of the volatility of the compounds can be obtained which may explain compositional changes over time.     

Effect of cerium, holmium and samarium ions on the thermal and structural properties of the HZSM-12 zeolite

The study of the incorporation of rare earth elements as additives in Y zeolites is a very interesting field of research, mainly by its potential application as additives in catalytic cracking process. In this work was studied the thermal and structural properties of cerium, holmium and samarium supported on HZSM-12 zeolite. The obtained materials were characterized by X-ray diffraction (XRD), infrared spectroscopy (FTIR), nitrogen adsorption, thermogravimetry (TG/DTG), differential scanning calorimetry (DSC) and differential thermal analysis (DTA). TG/DSC/DTA analyses showed that the dehydration temperatures of RE/HZSM-12 zeolites (RE=Ce, Ho, Sm) increase in relation to pure HZSM-12. The acid properties were investigated by pyridine thermo desorption via TG. The results showed two events of mass loss attributed to elimination of pyridine adsorbed on the weak+medium acid sites and on the strong acid sites.     

Nanoporous solvate of N,N-phthaloyl-glycine

N,N-phthaloyl-glycine is synthesized under microwave activation without solvent. Its nanoporous solvate is obtained by recrystallization. The solvate is studied by single crystal and powder XRD, thermogravimetry, and mass spectrometry. The crystals are composed of dimers that form a framework structure with infinite channels of about 4 ? in diameter, containing a non-stoichiometric amount of chloroform (the mole fraction is close to 0.35). The nature of the incorporated solvate molecules is determined by high-resolution mass spectrometry, and their quantity is found by thermogravimetry.     

Coupled thermogravimetry, mass spectrometry, and infrared spectroscopy for quantification of surface functionality on single-walled carbon nanotubes

We have successfully applied coupled thermogravimetry, mass spectrometry, and infrared spectroscopy to the quantification of surface functional groups on single-walled carbon nanotubes. A high-purity single-walled carbon nanotube sample was subjected to a rapid functionalization reaction that attached butyric acid moieties to the nanotube sidewalls. This sample was then subjected to thermal analysis under inert desorption conditions. Resultant infrared and mass spectrometric data were easily utilized to identify the desorption of the butyric acid groups across a narrow temperature range and we were able to calculate the degree of substitution of the attached acid groups within the nanotube backbone as 1.7 carbon atoms per hundred, in very good agreement with independent analytical measurements made by inductively coupled plasma optical emission spectrometry (ICP-OES). The thermal analysis technique was also able to discern the presence of secondary functional moieties on the nanotube samples that were not accessible by ICP-OES. This work demonstrates the potential of this technique for assessing the presence of multiple and diverse functional addends on the nanotube sidewalls, beyond just the principal groups targeted by the specific functionalization reaction.      

Characterization of precursor-ceramic conversion in Si-C-(O,N)-systems by thermoanalytical methods

On-line coupling of thermogravimetry (TG) with evolved gas analysis (EGA)/mass spectrometry (MS) was applied to characterize the organic-inorganic conversion of two synthesized polysilazanes to Si-C-N materials and of one commercial polysiloxane to Si-C-O materials.     

Adsorption of trimethyl phosphate on maghemite, hematite, and goethite nanoparticles

Adsorption of trimethyl phosphate (TMP) on well-characterized hematite, maghemite and goethite nanoparticles was studied by in situ DRIFT spectroscopy as a model system for adsorption of organophosphorous (OP) compounds on iron minerals. The iron minerals were characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), specific surface area, and pore size distribution. The minerals were found to consist of stoichimetrically and morphologically well-defined maghemite, hematite, and goethite nanoparticles. Analysis of in situ diffuse reflectance Fourier transform (DRIFT) spectroscopy shows that TMP bonds mainly to Lewis acid Fe sites through the O phosphoryl atom (-P═O-Fe) on hematite and maghemite. On goethite most TMP molecules bond to Br?nstedt acid surface OH groups and form hydrogen bonded surface complexes. The vibrational mode analysis and uptake kinetics suggest two main reasons for the observed trend of reactivity toward TMP (hematite > maghemite > goethite): (i) larger number of accessible Lewis acid adsorption sites on hematite; (ii) stronger interaction between the Lewis acid Fe sites and the phosphoryl O atom on TMP for hematite and maghemite compared to goethite with concomitant formation of surface coordinated TMP and dimethyl phosphate intermediates. As a result, on the oxides a surface oxidation pathway dominates during the initial adsorption, which results in the formation of surface methoxy and formate. In contrast, on goethite a slower hydrolysis pathway is identified, which eventually yields phosphoric acid. The observed trends of the reactivity and analysis of the corresponding surface structure and particle morphology suggest an intimate relation between the surface chemistry of exposed crystal facets on the iron minerals. These results are important to understand OP surface chemistry on iron minerals.     

Solvent-Polymer Interaction. II. Measurements of Liquid Solvent Molecules Associating with Polymer Sites and of Their Transport Behavior in Polymer Membrane by Thermogravimetry,GLC, and Mass Spectrometry

The measurement of sorption and diffusion behavior of liquid ethanol and water solvent mixtures in polyurethane membrane were made simultaneously by thermogravimetry. The individual amounts of sorbed water and ethanol in the polymer membrane were estimated by thermogravimetry and differentiated by mass spectrometry. In addition, from a single dynamic thermogravimetric experiment the activation energy for solvent molecules desorbing from the polymer membrane was also determined. The thermodynamic activity of ethanol vapor in equilibrium with the ethanol-water-polyurethane system was determined by gas-liquid chromatography. The clustering functions, the mean numbers of solvent molecules in the clusters, and those associating with polymer sites were evaluated by applying simplified mathematical derivatives using the experimentally determined values of activity and volume fraction of solvent molecules. It was found that at lower ethanol concentration the tendency for ethanol molecules to cluster together is high. At higher ethanol activity, ethanol-polymer site interactions predominantly occurred.

Similar results were observed for ethanol-water molecules. However, water molecules in this particular system did not exhibit a self-associating tendency nor interact with the polymer sites. It was concluded that the Zimm-Lundberg clustering theory can be adequately applied to the interpretation of sorption and diffusion behavior of liquid ethanol-water mixtures in the polymer membrane.     

Influence of phosphate modification on the surface properties of sulfated titania

The effect of increasing phosphate loading on the bulk and surface properties of sulfated titania was investigated by thermogravimetry, X-ray diffraction, laser Raman spectroscopy and FT-IR spectroscopy. The acid properties of the material were probed by low-temperature FT-IR spectroscopy of adsorbed CO. Monophosphate species in varying symmetries and protonation states were detected on the surface of the sulfated titania at low loadings. These condensed with formation of surface polyphosphates with increasing loading. Phosphate blocks weak Lewis acid sites and partially displaces sulfate groups. While the acid, properties of phosphate-free sulfated titania are dominated by Lewis acid sites, the phosphated samples also developed Brønsted acid sites due to the presence of POH groups on the surface.     

Mobility of 137Cs Related to Speciation Studies in Contaminated Soils of the Chernobyl Area

Chernobyl derived ¹³⁷Cs present in upper soil layers can still remain available to cation exchange and hence to downward migration. More than its physico-chemical deposit forms (fuel particles and/or condensed aerosols), radiocesium mobility is influenced by soil properties. Although all the soils studied contain illitic clay minerals, different ¹³⁷Cs fixation levels were observed due to: (1) the reactivity state of sorption sites with a low radiocesium content in soil, and (2) the presence, or absence, of organic matter complexes inhibiting cation sorption on clays.     

Thermal decomposition of bisphenol A-based polyetherurethanes blown with pentane: Part I—Thermal and pyrolytical studies

In this work thermal decomposition of ethoxylated 2,2-bis-(4-hydroxyphenyl)propane (BPA) and oxyalkylenated 2,6-toluyldiamine (TDA)-based rigid polyurethane (PU) foam, blown with pentane, is described. Thermogravimetry coupled with mass spectrometry (TG–MS) and thermogravimetry coupled with Fourier transform infrared spectroscopy (TG–FTIR) results of the evolution of volatile products during the degradation and gas chromatography coupled with mass spectrometry analysis of condensed products of PU foam pyrolysis (Py/GC–MS) are presented. Four temperature ranges of volatile products emission were detected under inert atmosphere—pentane used as blowing agent volatilizes in first range, the second one is dominated by dissociation reaction of urethane bonds by which first order amines, CO₂ and vinyl bonds, are formed, while complex reactions with formation of secondary amine and CO₂ occur in the third stage. Fourth stage is visible by further CO₂ evolution. Ethylene oxide and derivatives of dioxane, formed due to the presence of oxyalkylene chains, act as fuel during the burning of PU foam.     

Synthesis, crystal structure, vibrational spectra, and thermochemical transformations of tris(hydroxymethyl)aminomethane

A practically promising compound, tris(hydroxymethyl)aminomethane sulfate ((TRISH)₂SO₄, C₈H₂₄N₂O₁₀S) was synthesized and studied by a set of experimental methods (elemental analysis, IR and Raman spectroscopy, mass spectrometry, thermogravimetry).     

XPS and ToF‐SIMS study of a chalcopyrite–pyrite–sphalerite mixture treated with xanthate and sodium bisulphite

We present data from the surface analysis of a mineral mixture of chalcopyrite, pyrite, and sphalerite, elucidating surface reactions occurring during grinding and flotation. Flotation tests are also performed on the mixture, carried out in the presence of collector (SIBX) and also in the absence and presence of sodium bisulphite (NaHSO₃), a gangue sulphide mineral depressant. X‐ray photoelectron spectroscopy (XPS) studies on the ground mineral sample prior to flotation indicate that the mineral feed is heavily oxidised, especially the sphalerite in the mixture. Flotation recovery data clearly shows the effect of this oxidation, with the mineral recoveries of all three phases being lower than those observed in single mineral studies. In addition, the flotation recoveries show the effect of the inadvertent copper activation of pyrite and sphalerite, and the effect of bisulphite in reducing the flotation of sphalerite and pyrite in the mixture. Time of flight secondary ion mass spectrometry(ToF‐SIMS) data indicates that the depressing effect of bisulphite is due to the removal of copper and sulphur‐like species from the surface of pyrite and sphalerite and a consequent increase in the oxidation of these minerals. ToF‐SIMS data also indicates that the low recovery of pyrite and chalcopyrite in the absence of collector is most likely due to precipitation of zinc hydroxide on the surfaces of these minerals, formed in solution due to copper activation of sphalerite. Copyright © 2005 John Wiley & Sons, Ltd.     

Spectral, optical, and thermal studies of pure and Zn(II)-doped l-histidine hydrochloride monohydrate (LHHC) crystals

The influence of doping the transition metal Zn(II) on the growth, spectral, optical, and thermal properties of l-histidine hydrochloride monohydrate (LHHC) crystals grown by slow solvent evaporation method has been investigated. Structural characterizations of the grown crystals were carried out by single crystal X-ray diffraction analysis and it shows slight structural changes as a result of doping. The FT-IR spectral study reveals the presence of various functional groups and confirms the slight distortion of the structure of the crystals due to doping. The energy dispersive X-ray analysis reveals the incorporation of Zn(II) in the crystalline matrix of LHHC crystal. The UV?CVis spectral study was carried out to analyze the optical transmittance of the grown crystals and found that the transmittance is very high in the visible and UV regions for both pure and doped crystals. The second harmonic generation (SHG) for the grown crystals was confirmed by Nd:YAG laser. The scanning electron microscopy reveals the presence of defect centers and crystal voids. The thermal stability and purity of the grown crystals were analyzed by thermogravimetry, differential thermal analysis, and differential scanning calorimetry techniques.     

Thermal decomposition of jarosites of potassium,sodium and lead

Summary Jarosites are a group of minerals formed in evaporite deposits and form a component of efflorescence. As such the minerals can function as cation and heavy metal collectors. Thermogravimetry coupled to mass spectrometry has been used to study three Australian jarosites which are predominantly K, Na and Pb jarosites. Mass loss steps of K-jarosite occur over the 130 to 330 and 500 to 622°C temperature range and are attributed to dehydroxylation and desulphation. In contrast the behaviour of the thermal decomposition of Na-jarosite shows three mass loss steps at 215 to 230, 316 to 352 and 555 to 595°C. The first mass loss step for Na-jarosite is attributed to deprotonation. For Pb-jarosite two mass loss steps associated with dehydroxylation are observed at 390 and 418°C and a third mass loss step at 531°C is attributed to the loss of SO₃. Thermal analysis is an excellent technique for the study of jarosites. The analysis depends heavily on the actual composition of the jarosite.     

Thermal,structural and optical properties of Al2CoO4-Crocoite composite nanoparticles used as pigments

Novel zinc(II) complex compounds of general formula Zn(C₆H₅COO)₂·L₂ (where L=caffeine (caf) and urea (u)) were synthesized and characterized by elemental analysis and IR spectroscopy. The thermal behaviour of the complexes was studied during heating in air by thermogravimetry. It was found that the thermal decomposition of the anhydrous Zn(II) benzoate compounds with bioactive ligands was initiated by the release of organic ligands at various temperatures. On further heating of the compounds up to 400°C the thermal degradation of the benzoate anions took place. Zinc oxide was found as the final product of the thermal decomposition of all zinc(II) benzoate complex compounds heated to 600°C. Results of elemental analysis, infrared spectroscopy, mass spectroscopy and thermogravimetry are presented.