The island-arc volcanics situated in the eastern part of the Căpîlnaş-Techereu nappe (South Apuseni Mountains, Romania) were studied to evaluate the temperature, fluid properties, and mineral chemistry during low-temperature metamorphism. Detailed observations of metamorphic mineral assemblages were conducted using powder X-ray diffraction and electron microprobe. The metamorphism involved albitization of plagioclase feldspar and the formation of mafic phyllosilicates, zeolites, and other hydrous Ca-Al-silicate minerals. Mafic phyllosilicates consisted of transitional dioctahedral-trioctahedral smectites, mixed-layer chlorite-smectite (C/S, 6–96% chlorite), and discrete chlorite. The zeolites were analcime, stilbite ± stellerite, heulandite, laumontite, epistilbite, and mordenite. Also present, as secondary minerals filling amygdales and veins, are prehnite, pumpellyite, and secondary amphibole. Two mineral assemblages were identified which provide important information about metamorphic conditions (temperature, reaction progress, and fluid properties): (1) heulandite + analcime + quartz; and (2) laumontite + albite + quartz + prehnite + pumpellyite ± amphibole. The types of and relations between minerals in the first assemblage suggest the occurrence of low-temperature hydrothermal metamorphism in the zeolite facies at ~125°C, whereas the second assemblage was metamorphosed at 200°C. The composition and variability of the mineral assemblages in the study area suggest that, due to slow reaction rates, the low-temperature transformations and mineral assemblages were influenced not only by temperature but also by local rock composition, fluid-rock ratio, and fluid chemistry.

Hydrous Al-silicate deposits are found to the south of Pütürge in Malatya city, Turkey. The surrounding rocks consist of mylonitic granitic gneiss overlain by muscovite gneiss with kyanite-bearing metabasic schist lenses on top which are cut by silica veins containing prismatic tourmaline and speculante. Pyrophyllite is found within kyanite gneisses overlying the granitic gneisses. Fibrous, platy pyrophyllite is developed along the edges and cleavage planes of kyanite, whereas platy bunches of dickite occur as replacements of the relict kyanites as well as crack- and pore-fillings. Rocks forming the hydrous Al-silicate deposit contain 2M1 pyrophyllite, alunite, topaz, paragonite, dravite, dumortierite, chlorite and epidote as early hypogene minerals, and 2M1 dickite, diaspore, gibbsite, speculante, goethite and crandallite/goyazite as late hypogene minerals. On the basis of fluid inclusion and stable isotope data, it is estimated alterations to pyrophyllite and kaolinite occurred at temperatures are of 150 and 100°C, respectively, the minerals being formed by meteoric waters interacting with metamorphic rocks. Trace and REE variations are highly distinctive in terms of enrichment of most trace elements in pyrophyllite, whereas REEs are clearly abundant in dickite, indicating different conditions during formation such as early and late hypogene processes. The pyrophyllitic alteration took place in the late Cretaceous (69–71 Ma), whereas kaolinization occurred later.

The immobilization of antimicrobial drugs can be used to expand the application of antibacterial properties to consumer products. The purpose of this study was to stabilize an antimicrobial agent, levofloxacin (LVX), for sustained antibacterial activity by immobilizing the drug molecules in a layered double hydroxide (LDH) and embedded in a polyurethane substrate. As-prepared MgAl-LDH was calcined at 400°C and reconstructed with LVX for intercalation. The X-ray diffraction patterns and cross-sectional transmission electron microscopy images showed lattice expansion along the crystallographic c axis upon LVX intercalation, suggesting successful loading of the drug. Fourier-transform infrared spectra revealed that the structure of LVX was well preserved between LDH layers. Elemental analysis indicated that the loading capacity of LVX in the hybrid was 41.7%. Bacterial-colony forming inhibitory assay on Bacillus subtilis exhibited ~100% antibacterial activity of both LVX alone and LVX-LDH hybrid (LL). To determine sustainability of antibacterial activity by the hybrid, either LVX alone or LL hybrid was loaded in the polyurethane (PU) substrate for which antibacterial activity was evaluated before and after immersion in a phosphate-buffered saline for 3 days. The LVX-composited PU showed a dramatic decrease in antibacterial activity, down to 0% after buffer treatment; LL-composited PU still contained antibacterial activity (~34% of colony suppression) after phosphate-buffered saline immersion.

Hydrothermal solutions related to magmatic intrusions that occurred during the Oligo-Miocene resulted in advanced multi-stage alterations and, to varying degrees, kaolinization over a wide area of the Biga Peninsula. The most important formations in these kaolin deposits occurred along the NE–SW-trending Çan-Etili-Bayramiç fault zone. The Bahadırlı, Duman, and Çaltıkara quarries are well preserved kaolin deposits throughout these fault zones located within the Çan Volcanics. Mineralogical, geochemical, and isotopic analyses were performed to identify the environments of formation of kaolins and the origin of the hydrothermal solution that led to the formation of these deposits.

The mineralogical assemblages of each of the quarries differ from each other. The Bahadırlı kaolin quarry comprises kaolinite + alunite ± quartz ± smectite ± plagioclase ± K-feldspar. The Çaltıkara kaolin deposits consist of kaolinite + quartz + alunite ± iron-oxide and ore minerals. The Duman kaolin quarry was considered in two different slopes as a hanging wall block and a footwall block, and the blocks contain kaolinite + quartz + plagioclase ± smectite and kaolinite ± alunite ± smectite ± quartz ± plagioclase ± K-Feldspar ± gypsum, respectively. During petrographic investigations, it was observed that kaolinization occurred generally in K-feldspar and plagioclase phenocrysts and partially in the matrix. Mineralogical and micromorphological investigations revealed that the kaolin group includes the dioctahedral minerals kaolinite and halloysite. According to the trace element contents of the kaolinites, the Çaltıkara and Bahadırlı deposits had a hypogene origin, while the Duman deposit had a supergene origin. δ18O isotopic values of kaolinites ranged from +10.3 to +18.3‰. δ34S isotopic values ranged from –17.2 to +20.2‰ of alunite, galena, and pyrite minerals, which indicate different formation environments for the kaolin quarries. 40Ar/39Ar dating of alunite revealed that the timing of acid-sulfate alteration was compatible with the magmatic intrusions. All these data revealed the mineralogical, chemical, and isotopic differences caused by the effect of different hydrothermal processes in three kaolin deposits located on the same fault zone, close to each other and similar in age.

A detailed stratigraphic and facies reconstruction of a bentonitized acid-tuff succession, deposited within the transgressive systems tract of the Upper Miocene-Sarmatian Ser-3 eustatic cycle, at Sajóbábony, northern Hungary, was performed via petrographic, mineralogical and geochemical analyses. The purpose of the work was to analyze the degree of alteration of the volcanogenic sediments, as an indicator of the relative volcanic sedimentation rate. This may have an important role in indicating volcanic periods synchronous with sedimentation or reconstructing the volcanosedimentary paleoconditions. Sample pairs were collected from each bentonite and tuff layer, and, to facilitiate microstratigraphic relations, samples were collected every 10 cm within bentonite layers. Mineralogical analyses were performed by X-ray diffraction and geochemical analyses by inductively coupled plasma-mass spectroscopy.

The CaO/K2O and Eu/La ratios correlate with each other and with a montmorillonite/X-ray-amorphous phase ratio, reflecting Ca and Eu incorporation associated with devitrification and smectite formation. In accordance with the current literature, these mineralogical and geochemical proxies can be related primarily to the weathering processes. Considering vertical distributions in a sequence-stratigraphic context, the Ca content and Eu/La values show that local peaks and Eu anomalies characteristic of acid tuffs show minima at flooding surfaces (FS). Within a bentonite layer, representing a single transgressive period, the repeated events of dust-tuff accumulations have been determined by K2O/CaO and La/Eu peaks, confirmed also by the Eu anomalies in the rare earth element (REE) patterns, thus leading to the conclusion that the level of alteration is closely correlated with the elimination of terrigenous input and a minimum in volcanic sedimentation rate allowing more intensive alteration of the deposited volcanic material. In the case of fine tuff beds, Eu anomalies on REE patterns reflect limited alteration at the bottom and more intensive alteration in the upper parts of the beds, reflecting the effect of infiltration of sea water into the pores.

Palygorskite-rich mudstone interbedded with gypsum occurs in the Neogene Baiyanghe Formation in the Yangtaiwatan basin, northwest China, but the genesis of palygorskite in the mudstone is unclear. The objective of the present study was to clarify the manner by which the palygorskite evolved by analyzing the mineralogical and geochemical characteristics of the mudstone. The mineralogical composition of bulk-rock mudstone consisted of clay minerals, quartz, feldspar, dolomite, calcite, and gypsum. Palygorskite is dominant in the clay fraction together with illite and accessory chlorite and kaolinite. The interwoven rod-like palygorskite aggregates and delicate palygorskite particles indicated an authigenic origin. The bulk rock of palygorskite-rich mudstone was rich in the trace elements Cs, U, B, Li, Sb, Bi, and As, which, together with REE, all showed very positive correlation with major element oxides Al2O3, Fe2O3, MgO, K2O, and TiO2 of the mudstone, indicating that the REE and trace elements occurred mainly in the clay minerals. The detrital illite, chlorite, and kaolinite were the main original host of the REE and enriched trace elements. Statistical analyses showed that the authigenic palygorskite had strong affinity to such elements compared to the detrital clay minerals. In addition, the chondrite-normalized REE of the bulk mudstone showed essentially the same pattern irrespective of the proportions of detrital illite, kaolinite, chlorite, and authigenic palygorskite present in the samples. Thus, the conclusion reached was that palygorskite was generated from the dissolution of detrital clay minerals. The REE and enriched trace elements in authigenic palygorskite were inherited from the detrital clay minerals.

The mineralogical evolution of di- and trioctahedral smectites (i.e. montmorillonite and saponite) exposed to high-pH environments has been studied to determine the influence of compositional differences on clay dissolution and the formation of new phases. The present study helps to gauge the effects of highly alkaline solutions on the swelling capacity of smectitic clays and experimental results are extrapolated to predict the behavior of smectite-rich soils in various technical applications such as nuclear-waste storage and architectural conservation. The present study revealed extensive dissolution of montmorillonite in 5 M NaOH or 5 M KOH solutions and the neoformation of various zeolites, thereby reducing the clay’s swelling capacity significantly. Saponite, in contrast, experienced less pronounced changes, including transformation into a randomly interstratified saponite-chlorite and a Si-rich amorphous phase. These changes only provoked a partial reduction in swelling capacity. The results imply that under repository conditions (e.g. alkaline environment caused by hyperalkaline fluids released during concrete leaching), the slow and limited transformation of saponite into corrensite-type minerals would be beneficial for preserving the clay’s swelling capacity and, therefore, its effectiveness as a sealing material. Conversely, the loss of swelling capacity as a result of zeolite formation in montmorillonite observed in the present experiments would limit the clay’s effectiveness as a sealing material in waste repositories. In the case of earthen architecture conservation, alkaline consolidation treatments aimed at reducing the soils’ swelling capacity and, thereby, improving water resistance, would only be effective for treating earthen structures made of soils rich in dioctahedral smectites. Soils containing trioctahedral smectites, in contrast, are not likely to improve their water resistance because the swelling capacity will only be partially reduced.

Optical absorption spectroscopy has the potential to uncover many characteristics of Fe-bearing, redox-active smectites that have heretofore been hidden. The purpose of this study was to exploit this technique to reveal the temperature dependence of the spectra and to characterize the behavior of octahedral and tetrahedral Fe(III) under various stages of reduction. The Uley nontronites, NAu-1 and NAu-2, were compared using optical spectroscopy, which probed the crystallographic-site distribution of Fe in the clay structures as well as the resulting differences in the reduction process in the two minerals. All of the major differences in the spectra of the two minerals in the wavelength range 450–950 nm are due to the presence of a significant amount of tetrahedral Fe(III) in NAu-2. In situ observation of the optical spectra of NAu-1 suspensions as a function of the degree of reduction reveals a steady increase in the dominant intervalence charge transfer (IVCT) band and the resulting blue-green color as the Fe(II) content of the octahedral sheet increases. Although the spectrum of NAu-2 at ∼50% reduction looks nearly identical to the spectrum of NAu-1 at a similar state of reduction, the spectra corresponding to the initial stages of reduction are quite different. Stepwise reduction of NAu-2 causes a rapid decrease in the absorbance features due to crystal-field transitions of tetrahedral Fe(III) before the IVCT band appears, suggesting that tetrahedral Fe(III) is preferentially reduced before the octahedral Fe(III). The intensity of the absorbance features due to tetrahedral Fe(III) also exhibit an inverse temperature dependence, suggesting that they are enhanced due to exchange-coupling with Fe(III) ions in neighboring sites. Spectra of NAu-1 at liquid nitrogen temperature, therefore, allowed the identification of a small amount of tetrahedral Fe(III) in NAu-1 that had not been noted previously.

Glycerol is a byproduct of biodiesel synthesis by transesterification of triglycerides with short-chain alcohols in the presence of solid base catalysts. Because hydrotalcite is a potentially useful basic catalyst for the transesterification reaction, the interaction of glycerol with hydrotalcite is the focus of this work. Glycerol was intercalated into Mg-Al hydrotalcite with a Mg/Al molar ratio of 4 under elevated temperatures of 4432/503 K in the absence and presence of NaOH. The resulting materials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and N2 adsorption. The amount of glycerol incorporated into hydrotalcite increased with increasing temperature of intercalation. However, the brucite-like sheets of hydrotalcite partially decomposed during the intercalation process at the highest temperature. The presence of NaOH stabilized the hydrotalcite layers against decomposition under high temperature (503 K). The intercalated materials exposed large surface areas ranging from 142 to 663 m2 g−1, depending on the preparation conditions. The glycerol-intercalated hydrotalcites were less catalytically active than hydrotalcite with OH− counterions for the transesterification of tributyrin with methanol. The lower reactivity of glycerol-intercalated hydrotalcite was probably the result of a strong interaction between the intercalated glycerolate (HOCH2-CHOH-CH2O−) and the partially decomposed brucite-like sheets.

Bentonite is used as a catalyst in the removal of olefins from aromatic compounds and the present study was designed to investigate how its performance might be improved by various treatments. Bentonite from Semnan mine, Iran, was used in the study following initial characterization. In order to investigate the effect of acid and thermal treatments on the removal of olefins from aromatic compounds, bentonite samples were modified using HNO3 at different concentrations (0.15, 0.3, 0.5, 0.7, 1, and 2 M) and were also at temperatures between 100 and 340°C for 3 h. To examine the catalytic activity of bentonite-based catalysts, the samples were evaluated after running batch and continuous experiments. The optimum catalyst was characterized using thermo-programmed desorption (TPD) of NH3 to examine the acidic sites. Scanning Electron Microscopy (SEM) images, nitrogen adsorption-desorption isotherms (BET analysis), and X-ray diffraction (XRD) patterns were used to study the structural changes of the bentonite produced by the acid and thermal activation. The removal of olefins by the catalysts in batch and continuous systems revealed that the sample modified with 0.3 M Nitric acid at 150°C had superior catalytic activity, with olefin conversion remaining at >50% for up to 20 h. Nitrogen adsorption-desorption isotherms showed that acid treatment can produce a mesoporous structure. On the other hand, the TPD analysis indicated that during weak acid treatment, some cations, such as Al3+ and Fe3+, were leached from octahedral sheets and the interlayers of the clay mineral resulting in weak acid sites being generated. Finally, a novel method was proposed and tested for measuring the Bromine Index (BI) using potentiometric titration.

Copper(II) triethylenetetramine [Cu(trien)]2+ is an agent suitable for the 1-step determination of the cation exchange capacity (CEC) of many geomaterials using a procedure much less laborious than other, commonly used methods. It is also suitable for the determination of the composition of original exchangeable cations. In contrast to other common ions used for CEC analysis, the Cu(II) complex with triethylenetetramine, [Cu(trien)]2+, is specific for expandable clay minerals. The robustness of [Cu(trien)]2+ analysis was verified using reference clays, ion-exchanged reference clays, sediments, and soils. The [Cu(trien)]2+-based CEC of expandable clay minerals is not influenced significantly by ferrihydrite, goethite, manganite, birnessite, calcite, and gypsum. Birnessite, calcite, and gypsum admixtures affect the composition of the evolved cations. [Cu(trien)]2+ does not recover the entire CEC of soils (but rather that of the clay minerals only) which contain components other than clays which contribute to the CEC, e.g. soil organic matter. In a series of loess with buried paleosols and recent soils the [Cu(trien)]2+-based CEC ranged from 30 to 110% of total CEC obtained by traditional BaCl2 methods. The relative ratio of Ca to Mg, the prevailing exchangeable cations in soils and sediments in exogenic environments, are similar after [Cu(trien)]2+ and conventional BaCl2 treatments. The Ca/Mg ratio in the exchangeable fraction was used successfully for chemostratigraphic correlation of paleolacustrine sediments from a large lake in the Upper Carboniferous basins of eastern equatorial Pangaea and a series of recent flood plain sediments of the meandering Morava River in the Czech Republic. The Ca/Mg ratio obtained by [Cu(trien)]2+ analysis is proposed as a novel tool for the chemostratigraphic correlation of sediment series containing expandable clay minerals.

Waste kaolinite from a fertilizer industry was intercalated with n-methylformamide (NMF) under ambient conditions. The complex was washed, characterized and then reacted with benzamide (dissolved in ethanol) under similar conditions. Using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and differential thermal analysis (DTA), clear evidence of benzamide intercalation was observed after a reaction time of 48 h. The FTIR and DTA analysis also confirmed that the ethanol was not involved in the intercalation and that both NMF and benzamide are present in the interlayer region.

Development of an effective sorbent for diesel fuel spill remediation remains an important challenge in the field of synthesis due to the potential capacity of sorbents to efficiently purify contaminated sites. Fly ash, a coal combustion by-product, was used as a raw material to synthesize two inexpensive zeolites (SZ-1 and SZ-2) for oil spill remediation using an alkali fusion approach prior to hydrothermal treatment. The sorbents were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and N2 adsorption/desorption. Diesel fuel sorption was used to examine the potential capacity of the synthetic zeolites to sorb oil and other petroleum products. Diesel fuel viscosity and density were determined at room temperature using a viscometer and a pycnometer, respectively. The synthetic zeolites exhibited a higher diesel fuel sorption capacity than fly ash. The SZ-1 zeolite sorbed approximately 1.43 g·g−1 and SZ-2 sorbed approximately 1.9 g·g−1. The sorption was mainly a physical process and mesopore filling seemed to play the dominant role. Sorbent textures were, therefore, vital for the sorption of petroleum products.

Dioctahedral micas are composed of two tetrahedral sheets and one octahedral sheet to form TOT or 2:1 layers. These minerals are widespread and occur with structures differing by (1) the layer stacking mode (polytypes), (2) the location of vacancies among non-equivalent octahedral sites (polymorphs), and (3) the charge-compensating interlayer cation and isomorphic substitutions. The purpose of the present study was to assess the potential of parallel-illumination electron diffraction (ED) to determine the polytype/polymorph of individual crystals of finely divided dioctahedral micas and to image their morphology. ED patterns were calculated along several zone axes close to the c*- and c-axes using the kinematical approximation for trans- and cis-vacant varieties of the four common mica polytypes (1M, 2M1, 2M2, and 3T). When properly oriented, all ED patterns have similar geometry, but differ by their intensity distribution over hk reflections of the zero-order Laue zone. Differences are enhanced for ED patterns calculated along the [001] zone axis. Identification criteria were proposed for polytype/polymorph identification, based on the qualitative distribution of bright and weak reflections. A database of ED patterns calculated along other zone axes was provided in case the optimum [001] orientation could not be found. Various polytype/polymorphs may exhibit similar ED patterns depending on the zone axis considered.

Micron-grade natural vermiculite was modified by several physical and chemical treatments in order to increase the adsorption capacity of this material for B. A thermal exfoliation (T = 600°C) of pristine material, a chemical exfoliation through reaction with hydrogen peroxide (H2O2 35%), or grafting of a specific B complexant (i.e. N-methyl-D-glucamine: NMDG) led to an increase in the uptake of B at low initial concentrations of the aqueous solutions ([B] ≈ 5 mg L−1). The more efficient material is the NMDG-grafted clay, for which the adsorption uptake is four times greater than that of raw vermiculite, and reaches 0.04 mmol g−1. For all modified materials, the effect of the pH on B adsorption and the adsorption kinetics were studied and compared to raw vermiculite. Adsorption isotherms were also plotted and fitted well with the Freundlich equation.