La relation entre la surface développée par les particules d'une poudre et leur paramètre de taille et de morphologie est abordée de façon théorique, rigoureuse et générale. A l'aide d'un nouveau choix des grandeurs mesurées, il est possible de ne prendre en compte qu'une seule distribution statistique, de l'un des paramètres, les autres paramètres n'apparaissant dans la formulation qu'à travers leurs moyennes arithmétiques. Dans le cas de plaquettes, le problème est analysé de façon théorique et expérimentale. La formulation est encore simplifiée et on voit que la formule la plus simple consistant à négliger surfaces latérales et distribution de taille est finalement parmi les meilleures, les deux approximations se compensant.

A set of fine-grained samples from a turbiditic sequence in a Southern Pyrenees foreland basin (Jaca Basin, Eocene) were studied to determine the influence of tectonics (Pyrenean Orogeny) on phyllosilicate recrystallization and infer the grade and basin maturity. The samples from four different outcrops were examined by X-ray diffraction (XRD) and by scanning (SEM) and transmission electron microscopy (TEM) with special emphasis on clay-mineral characterization (e.g.illitic phases). The analysed samples have simple mineral assemblages and consist of detrital quartz, albite and calcite, scarce clay matrix (mainly illite with chlorite), and calcite and dolomite cement. The lack of other phyllosilicates such as mixed-layer illite-smectite (I-S), pyrophyllite, Na-micas, or kaolin minerals is quite remarkable. On the SEM scale, samples (with marl composition) have poorly sorted textures and high detrital contents. In many cases they show bedding and/or cleavage, and in some cases neither is observed. Most of the clay-sized illites show very similar crystallinity and b0 values (determined by XRD) and distributions of crystallite thickness (measured by TEM) in all the outcrops, which is typical of late-diagenesis illites forming under low-pressure conditions. These illites are parallel (or subparallel) to bedding or randomly orientated. They are also characterized by disordered polytypes and low K contents. In some TEM images, a second type of illite has been observed. This secondary illite occurs parallel to cleavage, with thicker crystals (25–35 layers), K contents in the interlayer, and a 2M1 polytype. The pole figure analysis shows that most of the clays have (00l) planes parallel (or subparallel) to bedding although there are abundant clays with random orientation. There is no trend in the clay orientation/disorientation from the south to the north of the basin. All the data indicate that the strain rate associated with the Pyrenean Orogeny has not been recorded in the turbidite sequence controlling the relative orientation of clays, although anchizonal clay crystallization is favoured as a minor process.

Minerals studied by an equilibrium model with a single mineral are similar to those studied in solid-solution models with q end-members. After discussing solid-solution models with q end-members where the limits of this kind of models are specified, the mathematical relations between the two kinds of models are developed. These relations show that the equilibrium model with a single mineral is compatible with the geochemical assumption of solid-solution. A method for estimation of equilibrium between a single mineral and a homogeneous set of aqueous solutions is proposed.

The interaction of aminotriazole (AMT) at pH 4 on Wyoming montmorillonite (mainly with Na ions) and Mg-vermiculite has been studied by X-ray diffraction and infrared spectroscopy. The AMT is adsorbed on montmorillonite in the cationic form by cation exchange. The amount of pesticide adsorbed was 71 mEq/100 g, which comprises ∼91% of the CEC of this sample (78.2 mEq/100 g). Saturation was reached in 24 h, giving rise to a complex with basal spacing 12.5 Å. Vermiculite adsorbs 167 mEq/100 g, almost 20% greater than the CEC (141 mEq/100 g), and the basal spacing was stabilized at 13.68 Å after five weeks of treatment with AMT. A part of the AMT is adsorbed in cationic form, displacing a great part of the exchangeable Mg2+ cations. The rest is adsorbed in molecular form by coordination to the Mg2+ cations which remain in the interlamellar space, removing a great amount of water, and remaining in the interlamellar space of vermiculite after washing with water, probably because of a steric hindrance from the AMT cations adsorbed.

Samples of two lenticular clay bodies from a Cretaceous deposit near Padrão (Lousã basin) were characterized by INAA, XRD and Mössbauer spectroscopy. This clay is believed to be the raw material used to manufacture the Iron Age and Roman fine grey pottery from Conímbriga. The differences observed in the chemical and mineralogical compositions of the clay samples and of different size fractions are consistent with the high variance found in the compositional group corresponding to that archaeological site.

The effects of chemical treatment on the radiation-shielding properties of Philippine natural zeolites were investigated using EpiXS following the EPICS2017 library. The zeolites were studied using X-ray diffraction and energy-dispersive X-ray spectroscopy. The acid treatment eliminated Fe and Ca, having a negative impact on the cross-section of the HCl-modified zeolite. The mass attenuation coefficients of the raw, NaOH- and HCl-modified zeolites at 1332 keV were 0.0545, 0.0544 and 0.0548 cm2 g–1, respectively. At 100–10,000 keV, the linear attenuation coefficient depends on the density and increases in the order HCl-modified > NaOH-modified > raw zeolite. In the energy range of 100–16,000 keV, the mean free path and half-value layer values are in the order of HCl-modified < NaOH-modified < raw zeolite. The raw and NaOH-modified zeolites have comparable effective atomic numbers, whereas the HCl-treated zeolite has significantly lower such values.

A synthetic protonic magadiite was used as a silica source to prepare zeolitic material (PLS-1) in the presence of tetramethylammonium hydroxide and water. The conversion of the protonic magadiite to the PLS-1 phase was achieved at 150°C after 5 days, or at 170°C after 3 days for SiO2: TMAOH:H2O molar ratios of 2.54:1:4.4. The synthesis of the pure PLS-1 phase depended also on the amounts of tetramethylammonium hydroxide and water used. Analysis by 29Si magic angle spinning nuclear magnetic resonance spectroscopy confirmed the layered character of the PLS-1 phase with a resonance at −93 ppm, and its dehydroxylation-condensation process. The chemical formula of (TMA)2Si18O33(OH)6 for PLS-1 was refined with the Rietveld method and the tetrahedron-splitting model. The later model has been proposed to describe the presence of silanol defects in the layered structure of PLS-1. Upon calcinations of the PLS-1 phase at temperatures >400°C, the removal of TMA cations and dehydroxlyation of PLS-1 layers resulted in a three-dimensional structure phase identified as the CDS-1 phase, with a chemical formula of Si18O36. The CDS-1 phase exhibited a large specific surface area of 288 m2/g and microporous character, as indicated by the nitrogen adsorption isotherms. The temperature-programmed desorption profile of ammonia indicated that CDS-1 exhibited one weak type of acid sites, confirmed, by pyridine desorption studies, as weak Lewis acid sites.

The use of clays as industrial catalysts requires optimization of modification methods during their preparation. The objective of this paper was to improve the traditional method of bentonite impregnation using ultrasound. For this purpose, three series of samples with Fe3+/clay molar ratios of 0.6–11 mmol/g were prepared, which differed in terms of preparation procedure. The first batch of samples was subjected to the conventional method of impregnation, where total synthesis of catalysts took 4 h. The other two series of samples were prepared with impregnation improved by ultrasound: preparation of Fe-polycation (5 min) and then its incorporation with a clay suspension for 5 and 10 min. The effect of clay preparation method on the catalyst stability and efficiency in a heterogeneous Fenton process was studied on aqueous solutions of synthetic Reactive Blue 4 dye. The catalysts prepared by the conventional method and the improved ultrasound method achieved high efficacy (91–97%, respectively), but their stability was different in the Fenton process. The catalysts prepared using ultrasound for 10 min exhibited greatest stability in the Fenton process. The catalysts synthesized with different Fe loadings displayed an increase in specific surface area and mesoporosity. Samples prepared by the improved impregnation method are comparable in terms of their characteristics with their counterparts prepared by the conventional method. It is thus possible to reduce the time taken by traditional catalyst synthesis by using optimized exposure time to ultrasonic waves.

Novel composite materials with wide pores were synthesized by an in situ technique using kaolin, palygorskite and pseudoboehmite as raw materials. The characterization results indicated that the synthesis components and conditions influenced the micro-, meso- and macro-porosity of the composite materials. The composites contained 53.5% zeolite Y and had much larger specific surface areas and pore volumes as well as significant hydrothermal stability. Fluid catalytic cracking (FCC) catalysts were prepared based on the composite materials. The results indicated that the as-prepared catalysts possessed a unique pore structure which assisted in diffusion-controlled reactions. In addition, the attrition resistance, activity and hydrothermal stability of the catalyst studied were superior to those of a reference catalyst. The catalyst studied also exhibited excellent nickel and vanadium passivation performance, strong ‘bottoms upgrading’ selectivity and better gasoline and coke selectivity.

The ability of Na+-, Li+-, K+-, Ca2+- and Mg2+-exchanged sepiolites and acid-activated sepiolites to remove ethylene from storage environments was examined. The sepiolite from Sivrihisar deposit, Turkey, was treated with 1.0 M NaNO3, LiNO3, KNO3, Ca(NO3)2, Mg(NO3)2, HNO3 and H2SO4 solutions at 90°C for 4 h. The mineralogical, chemical and textural properties of the materials were examined using X-ray diffraction, X-ray fluorescence, cation-exchange capacity and nitrogen gas adsorption analyses. The main mineral phase present in the materials was sepiolite, with minor dolomite, and traces of quartz and feldspar minerals and amorphous matter. Adsorption isotherms of ethylene at 273 K were measured on sepiolite samples over a pressure range of 0–100 kPa. As a result of partial blockage of the sepiolite channels, the ethylene adsorption capacity on cation-exchanged sepiolite forms (0.376–0.907 mmol g–1) was less than that of acid-activated sepiolite forms (1.279 and 1.308 mmol g–1). The ethylene adsorption capacities of the sepiolite samples were compared with those of other clay-based materials (0.167–1.817 mmol g–1) reported in previous studies of ethylene removal.

A Pickering emulsion was prepared via synergistic stabilization of a lipase and palygorskite particles. The optimum conditions for the stabilization of the Pickering emulsion, such as the concentrations of the palygorskite particles and lipase, were explored. The morphology of emulsion droplets was examined using digital optical microscopy and polarizing optical microscopy. The palygorskite–lipase co-stabilized Pickering emulsions were investigated by determination of the adsorption rate, pH and zeta potential of the aqueous dispersion, as well as by determining the contact angle values of the lipase solution on a palygorskite disc that was immersed in toluene. The catalytic performance of the immobilized lipase in the Pickering emulsion was studied via the investigation of its thermal stability, storage stability and reusability. The immobilized lipase showed greater stability than the free lipase. The lipase immobilized by Pickering emulsion retained a high level of activity even after seven periods of recycling.

This study examined the incorporation of benzalkonium chloride into palygorskite and montmorillonite, assessing their potential as drug carriers. The aim was to evaluate the use of both clay minerals as viable options for antibacterial drug delivery. Various amounts (0.5, 1.0 and 2.0 times the cation-exchange capacity) of benzalkonium chloride were incorporated into both clay minerals, and the resulting materials were characterized using Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction and elemental analysis using both CHNS-O elemental analysis and energy-dispersive X-ray spectroscopy. The Fourier-transform infrared spectroscopy and elemental analysis results indicate that benzalkonium chloride was incorporated successfully into the clay minerals. The X-ray diffraction traces of organo-montmorillonite indicate that the d-value increased as benzalkonium chloride content increased, confirming the intercalation of benzalkonium chloride within the montmorillonite interlayer space. By contrast, this behaviour was not observed for palygorskite. For the benzalkonium chloride-release studies, an initial burst release was found within the first 5 h, followed by a sustained release of benzalkonium chloride during the remaining testing time (24 h). Drug-release profiles were similar for modified palygorskite or montmorillonite during the testing time (24 h). Both clay minerals modified with benzalkonium chloride are promising materials for use as antibacterial fillers for several applications, including in the dental care industry.

The formation of iron-rich phyllosilicates can occur at different natural or engineered settings. In this study, the influence of pH in the hydrothermal synthesis of iron-rich phyllosilicates was investigated in the pH range 8.50–12.10 after the ageing of the precursor. The synthesized samples were characterized by powder X-ray diffraction, Raman and Mössbauer spectroscopies and transmission electron microscopy. Three domains of pH were identified, and these correlated with silica availability and its speciation in the solution. The formation of 1:1-type FeIII/FeII phyllosilicate was observed between pH 9.67 and 10.75. Above pH 10.75, two types of phyllosilicate-like mineral phases were observed. In addition to 1:1-type FeIII/FeII phyllosilicate, 2:1-type FeIII/FeII phyllosilicate was observed. Below pH 9.67, mainly amorphous silica and iron oxides were observed. The findings show that pH governed the crystallinity and nature of the obtained phyllosilicate-like phases.

Nucleation is much more important for clay minerals than for other authigenic cements as clay crystals are very small, so that a very large number of clay crystals must be nucleated. The role of this difficult kinetic step in the diagenesis of sandstones has not been considered adequately as a ratedetermining process. The relationship between pore-fluid supersaturation and the rate of nucleation of a mineral is very different from the relationship between supersaturation and the rate of crystal enlargement; thus the two processes will act at very different rates. A diagenetic model that predicts claymineral formation but omits the nucleation stage may make unreliable predictions. This may account partially for the discrepancy between numerical simulations of CO2 injection that predict high degrees of reaction between the CO2 and the host rock, and the results of studies of natural analogues that have much lower degrees of reaction.

The methods used for identifying clay minerals at Göttingen are passed in review. Stress is laid on the use of several different methods, each one alone being liable to errors. In particular, the optical microscope can be very valuable. The phase contrast method has greatly increased the scope of this instrument, especially for determining small r.i. differences (photographs).