Geopolymers have the potential to function as an environmentally friendly substitute for ordinary Portland cement, with up to 80% less CO2 emission during production. The effect is best utilized for geopolymers prepared with amorphous silica instead of waterglass (Na2xSiyO2y+x) to adjust the Si:Al ratio. The reactivity of the precursors with the alkaline activator affects the final mineralogical properties of the binder. The purpose of the present study was to investigate the amount of different phases formed during geopolymerization and to understand the quantitative evolution of carbonation during geopolymer synthesis by determining the solubility of metakaolinite and amorphous SiO2 in NaOH at various concentrations. The solubility was studied by ICP-OES measurements. X-ray diffraction was used for qualitative and quantitative phase analysis of the geopolymers. The solubility of the precursors increased with calcination temperature of metakaolinite, reaction time for amorphous SiO2, and at higher NaOH concentrations. Partial dissolution resulted in free Na+, which is a source for the formation of carbonates in the geopolymers. Thermonatrite occurred prior to trona formation in all samples.

In order to obtain nanopatterned surfaces, natural allophane particles originating from Japanese soils were immobilized as single particles on Si wafer substrates.When derived from aqueous suspensions, only a few nanoparticles were deposited and detected on the surface due to the weak adsorption of allophanes on the substrate. The amount of immobilized allophane was increased significantly, however, by using an organic solvent in combination with a micelle-based technique to suspend the allophane particles. The micelles were formed from a tailored, aliphatic diblock copolymer that was dissolved in toluene and contained several allophane particles. A cleaned silica chip was used as a substrate on which a monolayer of micelles was immobilized equidistant from each other by dip coating. To remove the polymer from the substrate and to produce free, single allophane nanoparticles, ultraviolet (UV) irradiation was used. After UV treatment, single allophane particles formed ring-shaped deposition patterns with a high surface density. Transmission electron microscopy (TEM) was used to verify the presence of single allophane nanoparticles in the Japanese samples which came from natural sources. The single allophane particles as well as the allophane-containing di-block copolymer micelles, both immobilized on Si substrates and TEM sample grids, were imaged by atomic force microscopy and TEM. In this way, the diameters of the single allophane particles, as well as the distances between the immobilized micelles and the particles and their topography on the substrates, were determined.

A survey of the lichen genus Pseudopyrenula in India is presented, with morphotaxonomic accounts of all six accepted species. Two species, P. himalayana and P. megaspora, are new to science. Both species resemble P. staphyleae but have a lichenized thallus and eccentric ostiole. Furthermore, P. himalayana differs from P. staphyleae in having immersed perithecia and narrower ascospores, while P. megaspora differs in the larger ascospores. Detailed descriptions of the new species are presented, together with notes on their chemistry, distribution, ecology and taxonomy. A key to all known species of Pseudopyrenula from India is also presented.

Altered basaltic tephra from Haleakala, Maui, are characterized using multiple techniques in order to identify the minerals formed under a variety of conditions and to understand the soil formation processes here. We collected samples that are representative of typical bulk weathered material in the crater, as well as solfataric alteration in a hydrothermal environment. For this study X-ray diffraction, electron probe microanalysis, scanning electron microscopy and transmission electron microscopy are coupled with spectroscopic techniques including Mössbauer, visible-infrared reflectance, transmission infrared, and thermal infrared emission spectroscopies to analyze these samples. The unaltered tephra are composed of feldspar, glass, pyroxene and olivine. Observed alteration products include Fe oxides, phyllosilicates and sulfates, as well as SAED amorphous Al-Si-bearing material. These samples are potential analogs for altered volcanic material on Mars as the pedogenic influences and contact with plants and animals are minimal. Results from this study may help to determine spectral signatures of these samples that could be used for identification on Mars of the minerals observed here.

The modern discipline of New Testament Studies has subjected the various components of the New Testament to close scrutiny, yet it persistently fails to ask critical questions about the New Testament considered as a whole. In its familiar twenty-seven book form, the New Testament may be seen as a fourth-century anthology of early Christian writings based on earlier collections or sub-collections (the fourfold gospel, the Pauline letter collection), yet innovative in establishing a sharply defined boundary between included and excluded texts. An analysis of contributions to this journal over a recent five-year period demonstrates the pervasive influence of this fourth-century construct in determining the scope and priorities of (so-called) ‘mainstream’ scholarship. Greater attention to the contingencies of canon-formation will enable us to locate the texts that came to form the New Testament within a wider early Christian literary landscape.

The stability, dispersion, and rheological properties of clay suspensions are important in the process of drilling. Organic clays were obtained traditionally by cation exchange, which is thermally unstable due to weak electrostatic interaction between the cationic surfactant and clay minerals. The purpose of the present study was to yield a stable and well dispersed organic bentonite (OBent) as a rheological additive for oil-based drilling mud. The co-modified method was used to modify bentonite by a cationic surfactant (cetyltrimethoxyammonium bromide: CTAB) and a silane coupling agent (hexadecyltrimethoxysilane: HDTMS). Firstly, the basal spacing of bentonite was enlarged by intercalation of CTAB, and the thermal stability of bentonite was improved by covalent bonds of HDTMS onto the bentonite platelets. The as-prepared OBent was characterized by infrared analysis, X-ray diffraction analysis, thermogravimetric analysis, and scanning electron microscopy. The hydrophobicity, solubility, viscosity, and tribological performance of the OBent were also recorded. The test results showed that the hydrophobicity of the co-modified bentonite was improved significantly, and was greater than that of bentonite modified with single surfactant CTAB or HDTMS. The bentonite modified by the surfactant together with the silane coupling agent had stable rheology and a lower coefficient of friction than the single surfactant-modified bentonite because more HDTMS entered into the interlayer spaces and formed chemical bonds at the inner surface of platelets.

This Comment, based substantially on a lecture delivered to the Ecclesiastical Law Society on 5 July 2023, will explore how bishops engage with the legislature, comparing the example of Bishop George Bell in the last century with a rather different example in the present century, namely Pope Benedict XVI and his address to members of Parliament in Westminster Hall in 2010. The comparison will, I hope, indicate some historic dimensions to the issues of episcopacy, law and government that are pertinent today.

Layer charge reduction of selected homoionic swelling clay minerals upon heating is reviewed. This phenomenon is known for Li+-montmorillonites as the Hofmann-Klemen effect. Aspects covered in the review include: mechanism of the charge reduction caused by the irreversible migration of small cations into the mineral layers; final sites of the fixed cations in the octahedral and/or tetrahedral sheets, as deduced on the basis of structural and spectroscopic data obtained in several studies; effects of octahedral and tetrahedral components of the layer charge; properties of the exchangeable cations; and the chemistry and structure of the mineral on charge reduction. Current knowledge has been summarized on the changes of various mineral properties connected with charge reduction, including the loss of swelling and the decrease in the cation exchange capacity, the most important change upon cation fixation. Also discussed are the preparation, properties, and advantages of uses of series of reduced-charge montmorillonites (RCMs) in research; interactions of RCMs with alkylammonium cations and organic cationic dyes, with some examples on the interactions with organic polymers and other organic compounds. Properties of organo-complexes and composite materials prepared from RCMs are also included in this review.

Polycyclic aromatic hydrocarbons (PAHs) are a large class of organic compounds which are commonly mentioned and have been shown to be highly carcinogenic and to persist in the environment for many years. An inexpensive remediation method has yet to be found, so the current study was undertaken to test the use of sepiolite, a fibrous clay mineral, as a potentially inexpensive and effective solid-phase adsorbent for sequestering PAHs. Pyrene was chosen as a model PAH due to the specific volatility, miscibility, and relatively soluble properties of the compound. A sepiolite of Turkish origin was then investigated to explore its potential to adsorb hydrophobic organic compounds from aqueous solution. The microstructure and morphology of the sepiolite were characterized using elemental analysis, X-ray diffractometry (XRD), Fourier-transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FE-SEM), and specific surface area from N2 adsorption isotherms. The pyrene adsorption isotherms were closely fitted to the Langmuir model and the coefficients of determination (RP2) were higher than 0.999. The results indicated that the high affinity of pyrene for sepiolite surfaces was dominated by the structural channels and the large number of Si-OH groups located on the basal surfaces. The intracrystalline interactions of pyrene with the sepiolite were, however, more favorable than pyrene interactions with sepiolite surface Si-OH groups, which can react directly with pyrene to form true covalent bonds (chemical interactions). Finally, the FE-SEM images initially revealed that, after sepiolite was loaded with adsorbed pyrene, a fairly straight and rigid arrangement of fibers occurred due to the aggregation of laths to form rods and the increased amounts of adsorbed pyrene.

Sudoite from diagenetic to very low-grade metaclastites of the Betic Cordillera was studied by X-ray diffraction and transmission/analytical electron microscopy. Sudoite formed directly from dickite, the assemblage dickite + sudoite + illite being replaced at increasing metamorphic grade by the assemblage pyrophyllite + sudoite + illite. Sudoite ranges in composition from Mg-rich to Fe-rich chemistries. In addition, a wide variety of mixed-layered structures (illite-sudoite, pyrophyllite-sudoite, and dickite-sudoite) was also identified. Mg-rich sudoite shows a mean chemical composition of (Al2.91Fe0.252+Mg1.80)(Si3.10Al0.90)O10(OH)8, and a IIb ordered structure with b = 9.055 Å. Intermediate Fe-Mg sudoite exhibits a very variable composition, the Fe-rich phases having a mean composition of (Al2.09Fe0.613+Fe0.872+Mg1.44)(Si3.31Al0.69O10(OH)8. These are disordered polytypes with b values ranging from 9.070 to 9.101 Å. Fe occurs in both octahedral sheets, according to two types of substitutions: Fe3+ for Al in the dioctahedral sheet and Fe2+ for Mg in the trioctahedral sheet. Sudoite with such a composition has not been described previously.

There has been limited research on clay mineral transformation in serpentinitic soils under humid tropical conditions. In this study, four soil pedons were selected along a toposequence from the summit (Entisol), shoulder (Vertisol), backslope (Alfisol) to footslope (Ultisol) positions to explore the contributions and the significance of landscape and weathering status of serpentinitic rock with regard to clay mineral transformations in eastern Taiwan. Experimental results indicated that the large amount of dithionite-citrate-bicarbonate-extractable Fe (Fed) and clay in the subsurface horizon were mainly caused by the strong leaching potential from intensive rainfall and weathering of the fine-grained parent rocks. The clay mineralogy reflected the clear weathering trend of the soils along the toposequence: (1) the soils on the summit and shoulder contained smectite and serpentine, which are predominant in the young soils derived from serpentinitic rocks; and (2) vermiculite gradually increased in the relatively old soils on backslope and footslope. The mineralogical transformations observed along the toposequence indicated that chlorite and serpentine, initially present in the Entisol on the summit, weather into smectite and interstratified chlorite-vermiculite in the intermediate soil on the shoulder under strong leaching and oxidizing conditions. Furthermore, vermiculite formed as the major weathering product of chlorite and smectite in the soil developed on the backslope. In addition to vermiculite, kaolinite and quartz formed in the soils on the footslope with the greatest concentration of Fed along the toposequence.

In this paper, a complete introduction to the dead reckoning navigation technique is offered after a discussion of the many forms of navigation, and the benefits and drawbacks associated with each of those types of navigation. After that, the dead reckoning navigation solution is used as an option that is both low-cost and makes use of the sophisticated equations that are used by the system. Moreover, to achieve the highest level of accuracy in navigation, an investigation of navigation errors caused by dead reckoning is calculated. Employing the suggested dead reckoning navigation system, the final position of an underwater vehicle can be established with a high degree of accuracy by using experimental data (from sensors) and the uncertainties that are associated with the system. Finally, to illustrate the correctness of the dead reckoning navigation process, the system error analysis as uncertainty that was carried out using experimental data using the dead reckoning navigation technique is compared with GPS data.

Clays are used in various cosmetic formulations, such as sunscreens, toothpastes, deodorants, creams, hair cosmetics, makeups, nail polish, facial masks, and shampoos, among others, to improve the organoleptic and physicochemical characteristics, to increase the stability, or to facilitate elaboration. Together with their technological functionalities, clays are cosmetologically active ingredients with cleaning, anti-aging, anti-wrinkling, and sun-care functionalities. Talc, kaolinite, mica, and some smectites are the clay minerals used most frequently in cosmetic products, but several other phyllosilicates as well as modified and synthetic clays are also used. Sometimes, clays are useful in the design of cosmetics just because they are made of rigid, small, and anisometric particles. Kaolinite and mica are made of hard prismatic particles which are lightly abrasive over the skin, teeth, or hair. Electric charges in smectites result in ion-exchange capacities useful in the loading of active cosmetics but also adsorbing and cleaning waste substances. Intermediate net negative charges of smectites result in layer expansion in polar media and specific rheological properties that are very useful in cosmetic formulations. The absence of charged particles in talc and kaolin make them flow easily resulting in lubricant effects. Protection against radiation from the sun by clay particles and decorative effects complete the possibilities of clays in cosmetics. The nomenclature for clays used as ingredients in cosmetics follows historical use and the names of commercial products, rather than following strict compositional principles. In this sense, an effort was made here to correlate the names of the minerals that make up each of the clay-based cosmetic ingredients.

Many studies of the chemical composition of sepiolite and palygorskite have been carried out using analytical electron microscopy (AEM). According to the literature, a compositional gap exists between sepiolites and palygorskites, but the results presented here show that they may all be intermediate compositions between two extremes. The results of >1000 AEM analyses and structural formulae have been obtained for the samples studied (22 samples of sepiolite and 21 samples of palygorskite) and indicate that no compositional gap exists between sepiolite and palygorskite. Sepiolite occupies the most magnesic and trioctahedral extreme and palygorskite the most aluminic-magnesic and dioctahedral extreme. Sepiolite and palygorskite with intermediate compositions exist between the two pure extremes: (1) sepiolite with a small proportion of octahedral substitution; (2) palygorskite with a very wide range of substitution (the pure dioctahedral extreme is unusual); and (3) intermediate forms, Al-sepiolite and Mg-palygorskite with similar or the same chemical composition. The chemical compositions of the intermediate forms can be so similar that a certain degree of polymorphism exists between Al-sepiolite and Mg-palygorskite.

The reduction of structural Fe in smectite is mediated either abiotically, by reaction with dithionite, or biotically, by Fe-reducing bacteria. The effects of abiotic reduction on clay-surface chemistry are much better known than the effects of biotic reduction. Since bacteria are probably the principal agent for mediating redox processes in natural soils and sediments, further study is needed to ascertain the differences between biotic and abiotic reduction processes. The purpose of the present study was to compare the effects of dithionite (abiotic) and bacteria (biotic) reduction of structural Fe in smectites on the clay structure as observed by infrared spectroscopy. Three reference smectites, namely, Garfield nontronite, ferruginous smectite (SWa-1), and Upton, Wyoming, montmorillonite, were reduced to similar levels by either Shewanella oneidensis or by pH-buffered sodium dithionite. Each sample was then analyzed by Fourier transform infrared spectroscopy (FTIR). Parallel samples were reoxidized by bubbling O2 gas through the reduced suspension at room temperature prior to FTIR analysis. Redox states were quantified by chemical analysis, using 1, 10-phenanthroline. The reduction level achieved by dithionite was controlled to approximate that of the bacterial reduction treatment so that valid comparisons could be made between the two treatments. Bacterial reduction was achieved by incubating the Na-saturated smectites with S. oneidensis strain MR-1 in a minimal medium including 20 mM lactate. After redox treatment, the clay was washed four times with deoxygenated 5 mM NaCl. The sample was then prepared either as a self-supporting film for OH-stretching and deformation bands or as a deposit on ZnSe windows for Si-O stretching bands and placed inside a controlled atmosphere cell also fitted with ZnSe windows. The spectra from bacteria-treated samples were compared with dithionite-treated samples having a similar Fe(II) content. The changes observed in all three spectral regions (OH stretching, M2-O-H deformation, and Si-O stretching) for bacteria-reduced smectite were similar to results obtained at a comparable level of reduction by dithionite. In general, the shift of the structural OH vibration and the Si-O vibration, and the loss of intensity of OH groups, indicate that the bonding and/or symmetry properties in the octahedral and tetrahedral sheets changes as Fe(III) reduces to Fe(II). Upon reoxidation, peak positions and intensities of the reduced smectites were largely restored to the unaltered condition with some minor exceptions. These observations are interpreted to mean that bacterial reduction of Fe modifies the crystal structures of Fe-bearing smectites, but the overall effects are modest and of about the same extent as dithionite at similar levels of reduction. No extensive changes in clay structure were observed under conditions present in our model system.

The Allou Kagne (Senegal) deposit consists of different proportions of palygorskite and sepiolite, and these are associated with small quantities of quartz and X-ray amorphous silica as impurities. No pure palygorskite or sepiolite has been recognized by X-ray diffraction. Textural and microtextural features indicate that fibrous clay minerals of the Allou Kagne deposit were formed by direct precipitation from solution. Crystal-chemistry data obtained by analytical/transmission electron microscopy (AEM/TEM) analyses of isolated fibers show that the chemical composition of the particles varies over a wide range, from a composition corresponding to palygorskite to a composition intermediate between that of sepiolite and palygorskite, but particles with a composition corresponding to sepiolite have not been found. Taking into account the results from selected area electron diffraction and AEM-TEM, fibers of pure palygorskite and sepiolite have been found but it cannot be confirmed that all of the particles analyzed correspond to pure palygorskite or pure sepiolite because both minerals can occur together at the crystallite scale. In addition, the presence of Mg-rich palygorskite and very Al-rich sepiolite can be deduced.

It is infrequent in nature that palygorskite and sepiolite appear together because the conditions for simultaneous formation of the two minerals are very restricted. The chemical composition of the solution controls the formation of the Allou Kagne sepiolite and palygorskite. The wide compositional variation appears as a consequence of temporary variations of the chemical composition of the solution.

The influence of organics on the crystallization of Al precipitates has been well documented. However, the effects of organics and ageing on the transformation and structural configuration of Al precipitates in relation to their surface and charge properties are not fully understood. This study investigated the structural, microporous and surface properties of Al precipitates formed under the influence of tannate and ageing. The Al precipitates were synthesized at an initial Al concentration of 7 × 10−3 M, an OH/Al molar ratio (MR) of 3.0, and initial tannate/Al MRs of 0, 0.001, 0.01 and 0.1, and aged for 1, 10 and 40 days. As indicated by a decrease in gibbsite and bayerite and an increase in the oxalate-extractable Al contents, the non-crystalline precipitates increased with the increase of the initial tannate/Al MR. This observation is in accord with the X-ray diffraction and Fourier transform infrared (FTIR) data. The impact of tannic acid on the nature of the Al precipitates is also reflected in the increase of the contents of the pyrophosphate-extractable Al, which is indicative of organically bound Al. This observation is in agreement with the increase in the intensity of characteristic FTIR absorption bands of tannate and the organic C and adsorbed water contents. The decrease in the crystallinity of Al precipitates with increase in the tannate/Al MR resulted in the development of microporosity, increase in BET specific surface area and decrease of the average pore diameter and point of zero salt effect (PZSE). The FTIR absorption bands characteristic of tannate of the Al precipitates became weaker with ageing, in accord with the ageing-induced decrease in the contents of organic C and pyrophosphate-extractable Al. Ageing drastically decreased the BET specific surface area of the Al precipitates formed in the absence of tannate but this effect was less conspicuous for the products formed at the tannate/Al molar ratio of 0.1. The ageing-induced change in the PZSE of the Al precipitates formed both in the absence and presence of tannate was not significant. The results accomplished in this study are of fundamental significance to our understanding of the combined effects of organics and ageing on structural configuration of hydrolytic precipitates of Al in relation to their microporosity, surface and charge properties in the environment.