Marek Michalik

Fluid–mineral interactions and constraints on monazite alteration during metamorphism

Abstract Clasts of metamorphosed Cadomian granites from the ~50−60 Ma Carpathian flysch in Gródek near the Rożnowskie Lake (Silesian Unit, SE Poland) are studied. They are considered to represent the Silesian Ridge, one of the hypothetical, currently unexposed source areas that supplied Carpathian sedimentary basins with clastic material. The gneisses preserve several examples of corona textures that include cores of primary monazite surrounded by polygonal grains of secondary apatite with thorianite inclusions, with intermediate zones of lamellar grains of secondary monazite and outermost rims of clay minerals, or various combinations thereof. Preservation of the complete textures is rare with polygonal apatite with thorianite inclusions, lamellar grains of monazite and clay minerals being particularly prevalent. Locally, polygonal apatite with thorianite inclusions surrounded by allanite and REE-epidote corona with a bastnäsite-synchysite phase occurs also. The textures observed developed during primary monazite breakdown and replacement by secondary minerals. The variation in reaction products indicates that alteration was strictly dependent on the local chemical system.

Release of boron during conversion of MFI boralite to ammonium and hydrogen forms

Conversion of synthetic boralites with the MFI struture to ammonium and hydrogen forms is accompanied by release of skeletal boron — up to 50% of initial content — without changes in the crystallinity (determined by XRD). The deboronation level β of the hydrogen form is greater than that of the ammonium variety, and for both types it increases with increasing B/u.c., i.e., with decreasing SiO2/B2O3 molar ratio. As a result of hydrolysis, ammonolysis, and dehydroxylation reactions, boron vacancies occur that loosen the structure and cause the u.c. volume of the hydrogen forms to be greater than are the corresponding “as-made” boralites. Aluminium impurities (from the synthesis raw materials) are significant for the modified forms with B/u.c. ≤ 0.78 (SiO2/B2O3 ≥ 245) and can generate Bronsted acidity. The boron content (B/u.c.), the deboronation level (β), the content of vacancies per unit cell, and the unit cell content of the modified forms depends on a single synthesis parameter, viz. the SiO2/B2O3 of the reaction mixture.

Synthesis and characterization of boralites with the MFI structure

Crystallization of a boralite with the MFI structure from the reaction mixtures 30 Na20.60 TPABr·(100/nRM) B2O3·100 SiO2·6060[1 + (1/nRM)] H2O (5 ≤ nRM ≤ 100) at 438 K is reported. Incorporation of boron into the framework leads to a contraction in the volume of the orthorombic unit cell. It is estimated that under the synthesis conditions only 2.8 of the 96 Si atoms in the unit cell can be replaced by boron. The highest synthesis yield is ca. 30%. The main impurities from silica sol (0.1 Al/u.c., 0.08 Ti/u.c., 0.05 Fe/u.c.) become significant for boralites with the silicon module > 240. The size of the largest crystalline aggregates amounts to ca. 18 μm. The properties of boralite can be controlled by a single parameter of the synthesis — the molar ratio SiO2/B2O3 of the RM.

Changes in the structure of ZSM-5 zeolites during boron and aluminium substitution

XRD and chemical analysis reveal that the orthorhombic unit cell of zeolite ZSM-5 structure undergoes linear contraction or expansion with increasing substitution level of B or Al, respectively. Evidence for a full substitution of B or Al in the framework to ca. three heteroatoms per unit cell is also provided by the 11B MASNMR spectrum and a linear decrease in the framework vibration frequency with the increasing Al per unit cell, as observed in the IR spectra. Only the boralite with an analytical content of 3.7 B atoms per unit cell contained ca. 24% of extraframework B. The similar electronegativities of B and Si explain the structural vibration frequency in the IR region, which is independent of the amount of B per unit cell.

Montmorillonite intercalated with SiO2, SiO2-Al2O3 or SiO2-TiO2 pillars by surfactant-directed method as catalytic supports for DeNOx process

The intercalation of natural montmorillonite with SiO2, SiO2-Al2O3 or SiO2-TiO2 pillars by the surfactant-directed method resulted in the formation of high surface area porous materials; these were tested as catalytic supports for the process of selective catalytic reduction of NO (DeNOx). The incorporation of titanium or aluminium into the structure of the silica pillars significantly increased the surface acidity of the clay samples. Iron and copper were deposited onto the surface of the pillared clays mainly in the form of monomeric isolated cations and oligomeric metal oxide species. The contribution of the latter species was higher in the clay intercalated with SiO2-TiO2 pillars than in the samples modified with SiO2 and SiO2-Al2O3 pillars. The pillared clay-based catalysts were active in the DeNOx process but, in this group, the best results were obtained for the clay intercalated with SiO2-TiO2 pillars and doped with iron and copper. The catalytic performance of the samples is discussed in respect of their surface acidity and active forms of transition metal species deposited.

Prospective Catalytic Structured Converters for NH3-SCR of NOx from Biogas Stationary Engines: In Situ Template-Free Synthesis of ZSM-5 Cu Exchanged Catalysts on Steel Carriers

The main objective of this study is to develop highly active catalyst and its preparation method that would meet the requirements of steel carriers for short-channel structured converters for NOx abatement from stationary biogas engines. The in situ synthesis was applied to deposit a series of Cu-exchanged MFI zeolite (ZSM-5) on kanthal sheets. The samples differ in preparation conditions: organic template assisted and template-free synthesis, Si/Al ratio and catalyst carrier pretreatment (calcined vs. non-calcined). Dip-coating method was used as a reference to compare loading efficiency. In order to evaluate preparation quality and purity of resulting structure the samples were examined by XRD and SEM/EDS at various stages of preparation. For the assessment of mechanical endurance of the deposited catalyst layers the ultrasonication method was used. The results demonstrated high depositing efficiency of the in situ synthesis as well as high activity and selectivity of the Cu-exchanged MFI samples prepared without costly organic template.

The effect of hydrochemical conditions and pH of the environment on phyllosilicate transformations in the weathering zone of pyrite-bearing schists in Wieściszowice (SW Poland)

Abstract The influence of hydrological conditions and the pH of the environment on chlorite and mica transformations in the acidic weathering zone of pyrite-bearing schists was studied. Phyllosilicate transformations were investigated in the area of the abandoned pyrite open-pit mine in Wiéciszowice (Lower Silesia, SW Poland) using X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy and chemical methods. (Mg,Fe)-chlorite, micas (muscovite and paragonite), quartz, feldspars and pyrite were reported to be the most abundant minerals occurring in pyrite-bearing schists. Phyllosilicate transformations were significantly stronger in dry conditions than in wet ones. This conclusion was supported by the fact that the inherited phyllosilicates predominated in the clay mineral fraction of waterlogged saprolites, whereas the secondary swelling minerals were minor components. In dry and extremely acidic saprolites (pH < 3), trioctahedral chlorite was dissolved and transformed into clay minerals (e.g. smectite and kaolinite), whereas swelling clays (smectite mainly) were formed at the expense of dioctahedral micas. The pH of water is an important factor influencing phyllosilicate transformations in waterlogged conditions. The phyllosilicate alterations under the influence of extremely acidic waters (pH < 3) were more advanced than in moderately acidic ones (pH of 4.6), as the secondary clay minerals seemed to be represented exclusively by smectite in the former, whereas HIMs and mixed-layer minerals such as R0 I-S-Ch, R0 I-S, as well as R1 Ch-V and/or R1 Ch-S occurred in the latter.

Experimental designs applied to hydrothermal synthesis of zeolite ERI + OFF (T) in the Na2O-K2O-Al2O3-SiO2-H2O system. Part 1. Diagnostic study

Hydrothermal synthesis of zeolite T in the Na 2 O-K 2 O-Al 2 O 3 -SiO 2 -H 2 O system was examined with the use of 2 2 and 2 3 experimental plans. The numerical coefficients have been calculated expressing the influence of two orthree parameters of the synthesis on such features of the product as: content of zeolite T, yield, solubility, silicon module, and the contributions of sodium and potassium ions. The parameters selected for examination were those determining the chemical composition of the reaction mixture: silicon module, relative alkalinity, absolute concentration of hydroxide ions, and also crystallization temperature and alkali corrosion of the borosilicate glass. The methodology used and its advantages revealed during investigations are presented and discussed.

Fine and ultrafine TiO2 particles in aerosol in Kraków (Poland)

Abstract During single particle analysis of aerosol in Kraków (Poland) we noticed a new component, that is, aggregates of TiO2 particles. These aggregates are from 0.5 to 4 μm and are composed of individual particles whose size typically varies from between 100 and 350 nm. Smaller particles (below 100 nm) also occur. TiO2 particles are relatively abundant in the summer. The size distribution of the particles corresponds to “pigmentary” TiO2, which indicates that they could be derived from paints and building materials. TiO2 particles were not previously identified in aerosol samples in Kraków, and therefore this phenomenon is likely to be related to the common usage of new building materials and paints. A review of the literature suggests that TiO2 particles, especially within the nanosize range, could result in health and environmental impacts; however, evaluation of the actual threat is difficult.

CO2 fluid inclusions in mantle xenoliths from Lower Silesia (SW Poland): formation conditions and decompression history

Raman spectroscopy has been applied to determine the density and pressure of formation of CO2 fluid inclusions in mantle xenoliths, carried to the surface at Wilcza Gora in southwestern Poland by e ...