Green chemistry is one of the preferred environmental approaches to protect the planet and human health, as it is based on the use of natural compounds such as pigments, clays, and bio-hybrids. The aim of the present study was to synthesize new colored biohybrids obtained from betalains (extracted from Opuntia, commonly known as prickly pear) and a purified smectite. The mineralogical composition and the chemical properties of the hybrids synthesized were determined using a variety of analytical methods. The maximum concentration of betalains adsorbed on the clay, as determined by UV spectroscopy, was 30.80 mg L-1. The change of the position and intensity of the infrared H-O-H stretching bands from 3405 to 3315-3352 cm-1 indicated that the adsorption of the betalains took place in the interlayer space of the clay. The amount of betalains intercalated did not affect the texture of the clay, as the particle size of the clay was unchanged. Fluorescence analysis revealed the characteristic emission and excitation peaks of the betalain compounds. Successful synthesis of bio-hybrids was achieved, increasing the potential for their possible use in cosmetic or industrial applications.

The objective of this manuscript was to test the drug-loading and delivery properties of Tunisian clays to demonstrate their potential as low-cost excipients in pharmaceutical formulations. Raw kaolinite, purified smectite, and organophilic smectite were studied for the adsorption and desorption of 2-amino-5-chlorobenzophenone (2A-5BC) as a drug model molecule. The adsorption and desorption properties of these clay samples were investigated under different pH conditions, including those emulating the intestinal and gastric fluids from human body. DFT calculations were performed to characterize the atomic interactions involved in the adsorption mechanism. The adsorption and desorption properties of these clays were correlated with their main physicochemical properties and textural parameters. The maximum 2A-5BC adsorption (i.e., 48.2 mg/g) was achieved using smectite functionalized with HDTMA. Electrostatic forces and hydrogen bonds played a relevant role during 2A-5BC adsorption. The desorption of 2A-5BC from clay samples was effective at 37 degrees C and pH similar to the intestinal and gastric fluids, thus reaching desorption efficiencies of up to 93 %. 2A-5BC desorption data were modeled with the Korsmeyer-Peppas equation and the results indicated the presence of a non-Fickian mass transport. Tunisian smectite functionalized with HDTMA presented promising performance and can be considered as a potential excipient in pharmaceutical formulations.

The experiments presented here are based on the reconfiguration of an ancient medicine, Lemnian Earth (LE) (terra sigillata, stamped earth, sphragis), an acclaimed therapeutic clay with a 2500-year history of use. Based on our hypothesis that LE was not a natural material but an artificially modified one involving a clay-fungus interaction, we present results from experiments involving the co-culture of a common fungus, Penicillium purpurogenum (Pp), with two separate clay slurries, smectite and kaolin, which are the principal constituents of LE. Our results show: (a) the leachate of the Pp+smectite co-culture is antibacterial in vitro, inhibiting the growth of both Gram-positive and Gram-negative bacteria; (b) in vivo, supplementation of regular mouse diet with leachates of Pp+smectite increases intestinal microbial diversity; (c) Pp+kaolin does not produce similar results; (d) untargeted metabolomics and analysis of bacterial functional pathways indicates that the Pp+smectite-induced microbiome amplifies production of short-chain fatty acids (SCFAs) and amino acid biosynthesis, known to modulate intestinal and systemic inflammation. Our results suggest that the combination of increased microbial diversity and SCFA production indicates beneficial effects on the host microbiome, thus lending support to the argument that the therapeutic properties of LE may have been based on the potential for modulating the gut microbiome. Our experiments involving reconfigured LE open the door to future research into small molecule-based sources for promoting gut health.

Montmorillonite, a ubiquitous clay mineral, has been engineered into a variety of porous and nanostructured catalysts, owing to its peculiar layered structure with characteristic surface and intercalation chemistry. Such a class of catalysts have continuously received considerable attention in both science and industry. This review examines recent advance in engineering montmorillonite into metal ion-exchanged montmorillonite catalysts, acid-activated montmorillonite catalysts, organo-montmorillonite catalysts, pillared interlayered montmorillonite catalysts and montmorillonite-supported catalysts. The former two types of montmorillonite-based catalysts have been used in the catalytic cracking, dehydration, hydrolysis, esterification, polymerization, alkylation, and Fischer-Tropic synthesis. The introduction of oxide pillars in the interlayer space of montmorillonite and the immobilization of metal oxides or zero-valent metals on the surface of montmorillonite allow montmorillonite to be used in the catalytic oxidation, reduction, isomerization and coupling reactions. Currently, the role of montmorillonite in acid catalysis, redox catalysis, and free radical catalysis have been partly revealed. The effect of the structures and the active sites of modified montmorillonite on its catalytic performance need to be investigated in more detail. Future work is suggested to focus on solving engineering problems and exploring novel catalytic applications of montmorillonite, in particular exfoliated montmorillonite nanolayers.

Tephrochronology provides a powerful tool to date and correlate the sedimentary sequence. However, the recognition of tuff and tuffinite in Cenozoic sequences is challengeable because of modification and alteration during diagenesis. In this contribution, we studied samples from the Cenozoic Lunpola basin on the central Tibetan Plateau to explore the potential provenance and distinction of pyroclastic materials from clastic sediments and to recognize the source-to-sink process of pyroclastic rocks and their deep geodynamic implications. The bulk mineralogical compositions and major and trace elements and Sr-Nd-Hf isotopic compositions of the pyroclastic rocks and clastic sediments in the Lunpola Basin were determined and compared with those of contemporary volcanic rocks in the Lhasa terrane. It is suggested that Th/U-Rb/Sr and (La/Yb)N-Na2O/Al2O3 discrimination plots might be used to distinguish pyroclastic from clastic sedimentary rocks in terms of source, transportation and diagenesis. According to the trace element and Sr-Nd and Hf isotope signatures, the 23.5 Ma pyroclastic rocks in the Lunpola Basin may originate from the Xungba ultrapotassic magmatism, and the - 21-15 Ma pyroclastic rocks may have been supplied by corresponding adakitic magmatism. The spatial distributions of the ultrapotassic and potassic as well as adakitic volcanic rocks in the Lhasa terrane may reveal that the west Lhasa terrane mantle lithosphere was detached and the east Lhasa terrane lower crust was thickened along with the India-Asia plate convergence.

Layer charge is an important property of 2:1 phyllosilicates originating from isomorphic substitutions in the structure, from vacancies in the octahedral sheet and from unsatisfied bonds at the edges of the crystals. It is of particular interest in the case of smectites because it affects important properties of this mineral. Several methods have been proposed for determining the layer charge of smectites, namely the structural formula method (SFM), the alkylammonium method (AAM), the NH4-method, the K-saturation method, and the O-D method. Most of these methods have been used extensively in the past and they all have advantages and shortcomings. The SFM and the AAM are based on different principles and are considered as primary methods. They have been used for a long time but they are time consuming and they provide contrasting layer charge values, with the AAM yielding consistently lower layer charge values than the SFM, especially for low-charge smectites. The remaining methods have been developed more recently and have been calibrated over their primary counterparts. They are applied easily and are capable of producing a large amount of data within a short time. In this sense they can be used both for geological interpretations and for assessment of bentonite deposits at an industrial scale.

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This article studies the geological structure, mineralogical composition, genesis and industrial properties of bentonite of the 10th Khutor deposit (Republic of Khakassia, Russia). The deposit is confined to the coal-bearing formation of Carboniferous age and is one of the main sources of bentonite for the metallurgical and foundry industries in Russia. The samples were collected during several field seasons and were studied with XRD, SEM, DTA, XRF, FTIR, BET and CEC analysis. The deposit consists of 6 productive layers with montmorillonite of alkaline-earth type varying in content from 38 to 72%. The formation of bentonites is associated with the alteration of volcanic ash of rhyodacite and dacite composition in zones of shallow sea water - bays and lagoons. The specific conditions of the formation, like an evaporitic depositional environment with high concentrations of soluble salts and burial diagenesis, as evidenced by seams and packs of hard coal, affected the textural and surface properties of the bentonite and caused the observed low microporosity and limited illitization.

Mineral compounds, as pigments and therapeutics, appeared regularly in the technical and medical texts of the Greco-Roman (G-R) world. We have referred to them as 'G-R medicinal minerals' and we suggest that despite their seeming familiarity, there are actually many unknowns regarding their precise nature and/or purported pharmacological attributes. Earth pigments are part of that group. This paper presents a brief overview of our work over the past twenty years relating to: a. the attempt to locate a select number of them in the places of their origin; b. their chemical/mineralogical characterization; c. the study of their ecology via the identification of the microorganisms surrounding them; d. their testing as antibacterials against known pathogens. In the process, and to fulfil the above, we have developed a novel methodological approach which includes a range of analytical techniques used across many disciplines (mineralogy, geochemistry, DNA extraction and microbiology). This paper focuses on a select number of earth pigments deriving from the island of Melos in the SW Aegean, celebrated in antiquity for its Melian Earth, a white pigment, and asks whether they might display antibacterial activity. We demonstrate that some (but not all) yellow, green and black earth pigments do. We also show that the manner in which they were dispensed (as powders or leachates) was equally important. The results, although preliminary, are informative. Given their use since deep time, earth pigments have never lost their relevance. We suggest that the study of their ecology/mineralogy and potential bioactivity allows for a better understanding of how our perception of them, as both pigments and therapeutics, may have evolved.

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10th Khutor deposit is located in the Republic of Khakassia and confined to the coal-bearing formation of Carboniferous age within the development of continental tuff-sandy-argillaceous sediments. In terms of mineral composition, bentonites are mainly composed of Al-rich montmorillonite. The content of montmorillonite reaches a maximum of 70-75%, with an average content of 55 to 70%. It is one of the main sources of bentonite for the metallurgical and foundry industries in Russia. One of the distinctive features of bentonites from the 10th Khutor deposit is that despite the age of the deposit, about 350 million years, and the presence of an initial phase of metamorphism, as evidenced by the formation of hard coal, these bentonites retained the ability to swell and have high thermal stability. The formation of bentonites is associated with the decomposition of volcanic ash of rhyodacite and dacite composition in zones of shallow seawater - bays and lagoons. The properties of bentonite were influenced by the initial stage of metamorphism. The main purpose of this work was to establish the conditions for the formation of this deposit, as well as to study the features of the mineral composition and physicochemical properties of these raw materials. In addition to fundamental issues, the aim of the work was applied research on the properties and quality of bentonites.

Smectites affecting water and soil exchangeable cations, especially potassium and ammonium related to plants, are common swelling clay minerals in sediments and paleosols that can record paleoenvironmental and paleoclimatic information. Paleoenvironmental and paleoclimatic interpretations are potentially ambiguous, because smectite minerals may have either detrital or pedogenic origins. This study analyzes smectites in Lower Eocene paleosols of the Qaidam Basin, China, with the goal of determining their origin and paleoclimatic significance. Twelve smectite-rich vertisol samples were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), inductively coupled plasma-mass spectrometry (ICP-MS), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) in the Dahonggou (DHG) section of the Lulehe Formation. The samples from DHG section contained predominant dioctahedral smectites (60?65%) in the <2 ?m clay fractions. Minor dioctahedral illites, dioctahedral interstratified illite-smectite (I-Sm), kaolinite, and traces of dioctahedral chlorites and palygorskites were present. The chemical data and FTIR spectra revealed both tetrahedral substitutions (i.e., Al for Si) and octahedral substitutions (i.e., Mg and minor Fe for Al) in the dioctahedral smectites. Montmorillonite comprised the dominance of the fine-clay fractions (< 0.2 ?m) with minor contributions of beidellite, as determined by the Greene-Kelly test (GK-test), geochemical and FTIR analyses. SEM observations revealed two morphological types of dioctahedral smectites, the less abundant one with typical ?honeycomb? structure, interpreted as neoformed, and the other occurring as thin, well-defined plates and irregular masses considered to be detrital. DSC revealed two dehydroxylation temperatures (500?550 ?C and 600?700 ?C), indicating the presence of trans-vacant (tv) and cis-vacant (cv) layers, respectively. The cv layers were attributed to montmorillonite originating as catchment-delivered detritus, as the study Lulehe Formation exhibited no evidence of volcanic ash layers or diagenesis that would have promoted formation of montmorillonite with high dehydroxylation temperatures. The tv layers represented pedogenic beidellite formed via solution crystallization in a floodplain pedogenic environment. The accumulation of abundant inherited montmorillonite and neoformed beidellite in paleosols of the Lulehe Formation was probably promoted by a relatively warm climate with alternating wet-dry seasons during the Early Eocene. Admixture of detrital montmorillonite makes paleoclimatic reconstructions based on bulk-smectites concentrations and isotopic compositions unreliable, showing that integrated clay mineralogical analyses of the type undertaken in this study are necessary to identify the provenance and paleoclimatic significance of smectites in sediments.

A great variety of fine grained industrial rocks, which are valued by the industry contain variable amounts of amorphous or poorly crystalline matter, which is not easily detectable by the conventional mineralogical analysis methods based on X-ray diffraction (XRD). The quantification of amorphous matter in industrial rocks is a major task because it provides a thorough characterization of the raw materials and assists to interpret their reactivity. Among the most reliable methods used for quantification of amorphous matter, are those which are based on Rietveld refinement. In this study we prepared 1:1 mixtures of synthetic or natural calcite and quartz with 5-80% glass flour and added corundum (α-Al2O3) internal standard and applied the Autoquan2.80 © software based on the BGMN computer code to quantify the amorphous matter content. The mixtures with synthetic minerals yielded results with minimum absolute error due to the similar particle size of the minerals, the internal standard and the glass. By contrast, the mixtures with natural minerals displayed greater relative error due to the particle size difference between the minerals on the one hand and the internal standard and the glass on the other, due to the microabsorption effect. Moreover, preferred orientation was important in the case of natural calcite, due to perfect cleavage plane. Mixtures containing up to 25% amorphous matter did not display the characteristic hump at 20-30 °2θ, suggesting that the lack of the hump is not a safe criterion for the recognition of amorphous matter.

The Westerwald region is one of the major ceramic clay mining areas of Germany. The mined clays were deposited on the weathered Rhenish massif during Eocene and Oligocene and were protected from erosion by a large alkaline basalt cover. Two Fe-rich bentonite layers exposed in quarries of the Eastern part of the Westerwald were investigated with X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, optical microscopy, scanning electron microscopy, chemical analyses and cation exchange capacity (CEC). In both bentonite layers, the main mineral is a high-charge Fe-rich beidellite containing exchangeable Ca and Mg. Even if they both derive from mafic volcanic rocks, the difference in accessory minerals and trace element content leads to the conclusion that they have a different precursor. The lower bentonite layer also contains talc, saponite, halloysite, goethite and anatase. It is part of the Paleozoic bedrock and results from the weathering of a Lower Carboniferous metabasalt. The upper bentonite layer has Upper Oligocene age and has been derived from the alteration of tuffite with a composition ranging from alkali basalt to trachyte. This bentonite is linked to the first eruptions of the intraplate Cenozoic volcanic activity of the Westerwald.

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Ethnopharmacological relevance: Medicinal Earths (MEs), natural aluminosilicate-based substances (largely kaolinite and montmorillonite), have been part of the European pharmacopoeia for well over two millennia; they were used generically as antidotes to 'poison'. Aim of the study: To test the antibacterial activity of three Lemnian and three Silesian Earths, medicinal earths in the collection of the Pharmacy Museum of the University of Basel, dating to 16th-18th century and following the methodology outlined in the graphical abstract. To compare them with natural clays of the same composition (reference clays) and synthetic clays (natural clays spiked with elements such as B, Al, Ti and Fe); to assess the parameters which drive antibacterial activity, when present, in each group of samples. Materials and methods: a total of 31 samples are investigated chemically (ICP-MS), mineralogically (both bulk (XRD) and at the nano-sized level (TEM-EDAX)); their organic load (bacterial and fungal) is DNA-sequenced; their bioactivity (MIC60) is tested against Gram-positive, S. aureus and Gram-negative, P. aeruginosa. Results: Reference smectites and kaolinites show no antibacterial activity against the above pathogens. However, the same clays when spiked with B or Al (but not with Ti or Fe) do show antibacterial activity. Of the six MEs, only two are antibacterial against both pathogens. Following DNA sequencing of the bioactive MEs, we show the presence within of a fungal component, Talaromyces sp, a fungus of the family of Trichocomaceae (order Eurotiales), historically associated with Penicillium. Talaromyces is a known producer of the exometabolite bioxanthracene B, and in an earlier publication we have already identified a closely related member of the bioxanthracene group, in association with one of the LE samples examined here. By linking fungus to its exometabolite we suggest that this fungal load may be the key parameter driving antibacterial activity of the MEs. Conclusions: Antibacterial activity in kaolinite and smectite clays can arise either from spiking natural clays with elements like B and Al, or from an organic (fungal) load found only within some archaeological earths. It cannot be assumed, a priori, that this organic load was acquired randomly and as a result of long-term storage in museum collections. This is because, at least in the case of medicinal Lemnian Earth, there is historical evidence to suggest that the addition of a fungal component may have been deliberate.