To acquire a better understanding of the influence exerted by the presence of Cd2+ during the process of transforming ferrihydrite to goethite, the morphological and structural changes of several samples obtained by the addition of Cd2+ to a suspension of nascent goethite were explored, and their chemical reactivity in acid media assessed. The samples (series Gi) were obtained by adding, at different times during the synthesis process, Cd2+ ions to ferrihydrite (Fe5HO8.4H2O) formed in alkaline media. The suspensions were aged for 5 days at 70°C, and the amorphous materials were extracted using a HCl solution (series GHCl-i). The X-ray diffraction (XRD) patterns showed that a goethite-like phase was formed, and chemical analyses indicated that the Cd content, xCd, increased with the earlier addition of the Cd2+ ions to the Fe oxyhydroxide suspension. Lattice parameters and cell volume, obtained by the Rietveld simulation of XRD data, indicated an enlargement of the cell parameters of goethite in line with the Cd-for-Fe substitution. In order to determine the influence of oxalate ions on the non-extracted solids, a second set of samples was also prepared that was kept in contact with an ammonium oxalate solution for 4 h (series Gox-i). The dissolution behavior of two series of Cd goethites and of a third series, obtained from coprecipitation of Fe3+ and Cd2+ ions in alkaline media, was observed. Kinetics measurements in 4 M HCl showed that the initial dissolution rate of samples Gox-i decreased with aging time, while the opposite effect was observed for series GHCl-i. Dissolution–time curves were well described by the Kabai equation, and activation energies were calculated using the Arrhenius equation. The results indicate that the presence of Cd during the crystallization process of goethite leads to the formation of a Cd goethite with modified morphology, structural parameters, and chemical reactivity.

The problem to be solved is whether Al is a necessary component of Fe-Mg chlorites. Very unusual Al-depleted and Fe-enriched trioctahedral chlorites with the empirical formulae Na0.05Ca0.05(Fe2+3.01Mg2.01Ti0.14Fe3+0.04)Σ6.00[(Si3.53Fe3+0.41Al0.06)Σ4.00O10](OH)8·nH2O (Sample 1) and Na0.05Ca0.01(Fe2+3.26Mg1.97Fe3+0.75Mn0.01Ti0.01)Σ6.00[(Si3.16Fe3+0.75Al0.09)Σ4.00O10](OH)8 (Sample 2) have been discovered in Al-depleted dolomite carbonatites of the Kovdor complex of ultramafic, alkaline rocks and carbonatites, Kola Peninsula, Russia. The presence of substantial amounts of Ti in Sample 1 is another unusual feature of this mineral. In both samples, chlorites are intimately intergrown with cronstedtite-1T which is an indication of a low stability of chlorite structure in the absence of aluminum in the tetrahedral sheet. The crystal structure of chlorite in Sample 1 was solved by the Rietveld method. The mineral is triclinic (IIb-4-module), space group C-$1$, a = 5.4153(4), b = 9.3805(7), c = 14.5743(12) Å, α = 90.137(5)°, β = 96.928(5)°, γ = 90.043(6)°, V = 734.95(10) Å3, and Z = 2. A problem to be solved is how stable are Al-free chlorites belonging to the clinochlore–chamosite solid-solution series and whether their existence in natural mineral assemblages is possible. The results obtained indicate that even though Al-depleted chlorites belonging to the clinochlore–chamosite solid-solution series exist in Nature as metastable phases, these minerals are extremely rare and much less stable than Al-poor serpentines.

Zearalenone (ZEA), a common contaminant in food and feedstuffs, threatens human and animal health. The present study aimed to investigate the protective effects of modified palygorskite (MPal), a ZEA-targeted adsorbent, on broilers (young chickens) fed a ZEA-contaminated diet. Broilers were subjected to one of three treatments for a period of 42 days: a basal diet (control group), a ZEA- contaminated diet, and a ZEA-contaminated diet supplemented with 1 g/kg of MPal. Blood was collected for serum metabolite assay, and liver and kidney were sampled to determine ZEA residue and antioxidant-related parameters, using commercial spectrophotometric kits. Compared with the basal diet, the ZEA- contaminated diet resulted in compromised growth performance (reduced daily gain and feed intake during finisher period), disordered relative liver weight (decreased at 21 days but increased at 42 days), increased ZEA residue in liver and kidney, abnormal serum metabolites (decreased total protein content but increased alanine aminotransferase activity at 21 and 42 days, reduced albumin content at 21 days, and elevated aspartate aminotransferase activity at 42 days), and disrupted antioxidant capacities of broilers (increased total superoxide dismutase (T-SOD) activity in liver at 21 and 42 days, decreased T-SOD activity in kidney at 21 and 42 days, and in serum at 42 days, greater malondialdehyde accumulation in liver and kidney at 42 days, and lower glutathione content in kidney at 21 days). The adverse consequences resulting from the ZEA-contaminated diet were relieved by the supplementation of MPal (except albumin concentration in serum and T-SOD activity in liver at 21 days), with the values of growth-performance parameters, liver weight, renal ZEA accumulation, total protein content, transaminase activity at 42 days, and antioxidant indexes being similar to those in the control group. These results suggested that MPal supplementation could promote growth performance, attenuate liver damage, and improve the antioxidant abilities of broilers fed ZEA-contaminated diet by reducing ZEA accumulation.

Palygorskite in Miocene mudstones, palustrine limestones and calcretes from the Esquivias locality (Madrid Basin, Spain) has been analyzed by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and analytical electron microscopy to determine its characteristics and chemical composition. Other palygorskites from the literature are used as references. The mean structural formula obtained from the analysis of isolated particles is (Si7.87Al0.13)O20($({\text{Al}}_{1.04}{\text{Fe}}_{0.20}^{3+}{\text{Mg}}_{3.11}{\square }_{0.65})$)(OH)2(OH2)4(Ca0.02K0.05Na0.08). This palygorskite has the largest Mg content reported in the literature, and it seems that, chemically, it fills the ‘compositional gap’ existing between sepiolite and palygorskite. Infrared spectroscopy reveals the absence of trioctahedral Mg and therefore the possibility of the existence of magnesic clusters in the ribbons is discounted. An homogeneous distribution of the octahedral cations (Al, Fe3+ and Mg) along the ribbons is proposed.

Enzymes adsorbed on clay minerals and soil colloids may exhibit lower activities compared to those of free enzymes. A particular toxic metal may affect the activity of the adsorbed enzyme less critically than that of the free form, however. This information is necessary for predicting catalytic performances of clay-immobilized enzymes in natural soils as well as in food, pharmaceutical, and chemical systems. The objective of the present study was to find out how adsorption on palygorskite and sepiolite minerals modifies the catalytic activity and the Michaelis–Menten kinetics of alkaline phosphatase (ALP). Inhibition kinetics of adsorbed ALP by Cd was also compared to that of the free enzyme. The results revealed that the affinity to the substrate and the maximum reaction velocity of ALP decreased upon adsorption on the fibrous clay minerals. The ALP adsorbed maintained a reasonably high activity recovery (AR) compared to the free enzyme. The AR of the adsorbed ALP ranged from 76.9 to 92.5% for palygorskite and from 71.2 to 90.2% for sepiolite, depending on the substrate concentration applied. The presence of Cd decreased the affinity to the substrate of both the free and the adsorbed ALP, while the maximum reaction velocity remained nearly unchanged, indicating that the inhibitory effects of Cd on both the free and adsorbed ALP activities were competitive in nature. The adsorbed enzyme, however, was inhibited less severely by Cd compared to the free enzyme. The adsorption of ALP on the fibrous clay minerals, therefore, maintains the ALP activity to a great extent and provides more resistance for the enzyme against the inhibitory effects of Cd.

To further elucidate adsorption-to-partition transitional mechanisms which have been proposed previously for organo-bentonites with different surfactant loadings, the structural characteristics of interlayer surfactant aggregates on organo-bentonite with different surfactant cetyltrimethylammonium bromide loading levels (0.20–2.56 times cation exchange capacity, CEC) have been investigated by in situ X-ray diffraction (XRD) and Fourier TransformInfrared (FTIR) spectroscopy. The sorption properties and the structure of the clay interlayers changed according to the type of surfactant, the surfactant loading level, and the state of hydration in the clays. Based on the sorption of nitrobenzene, phenol, and aniline to organobentonites, the contaminant sorption coefficients (Ksf), normalized with the organic carbon content, show a remarkable dependence on surfactant loading levels. The Ksf values first increased with surfactant loading until reaching a maximum at 1.0 to 1.2 times the CEC, and then decreased. According to the theoretical calculation of the volume fractions relating to the interlamellar space, the interlamellar microenvironment became a more hydrophobic medium, contributing to the dissolution of organic contaminants, as the surfactant loading increased from 0.20 to 2.56 times the CEC. However, the increase in packing density (ρ) for the intercalates, and induced steric hindrances both affect the result in terms of a reduction in the accessible free space where the organic contaminants can be located, which might be a negative factor in the sorption capacity.

Strong gas-mineral interactions or slow adsorption kinetics require a molecular-level understanding of both adsorption and diffusion for these interactions to be properly described in transport models. In this combined molecular simulation and experimental study, noble gas adsorption and mobility is investigated in two naturally abundant zeolites whose pores are similar in size (clinoptilolite) and greater than (mordenite) the gas diameters. Simulated adsorption isotherms obtained from grand canonical Monte Carlo simulations indicate that both zeolites can accommodate even the largest gas (Rn). However, gas mobility in clinoptilolite is significantly hindered at pore-limiting window sites, as seen from molecular dynamics simulations in both bulk and slab zeolite models. Experimental gas adsorption isotherms for clinoptilolite confirm the presence of a kinetic barrier to Xe uptake, resulting in the unusual property of reverse Kr/Xe selectivity. Finally, a kinetic model is used to fit the simulated gas loading profiles, allowing a comparison of trends in gas diffusivity in the zeolite pores.

A comprehensive study of clay minerals should include determination of the vacancy pattern of the dioctahedral sheet. The purpose of this report is to consider the advantages and limitations in various diffraction and non-diffraction methods for the determination of the layer types in clay minerals. Identification of trans-vacant (tv) and cis-vacant (cv) clay minerals reported here is based on powder X-ray diffraction (XRD) patterns calculated for different polytypes consisting of either tv or cv layers, on the simulation of experimental XRD patterns corresponding to illite or illite fundamental particles in which tv and cv layers are interstratified, and on the semi-quantitative assessment of the relative content of the layer types in the interstratified structures by generalized Méring’s rules. A simple and effective method for identification of tv and cv layers in dioctahedral 2:1 layer silicates employs thermal analysis and is based on different dehydroxylation temperatures for tv and cv illite and smectite layers.

Crystal chemical analysis of various dioctahedral 2:1 layer silicates consisting of tv and cv layers indicates that compositional control is present in the distribution of octahedral cations over trans- and cis-sites. In dioctahedral smectites the formation of tv and cv layers is related to the layer composition and local order-disorder in the distribution of isomorphous cations. Dioctahedral 1M micas with abundant Fe3+ and Mg occur only as tv varieties. In contrast, 1M-cv illite, as well as cv layers in illite fundamental particles of I-S, can form only as Fe- and Mg-poor varieties. In illites and illite fundamental particles of I-S consisting of tv and cv layers, cv layers prevail when the amounts of Al in octahedra and tetrahedra are >1.55 and >0.35 atoms per O10(OH)2, respectively.

The main factors responsible for the stability of cv and tv illites have been established. Monomineral cv 1M illite, its association with tv 1M illite, and interstratified cv/tv illite occur around ore deposits, in bentonites, and in sandstones mostly as a result of different types of hydrothermal activity. The initial material for their formation should be Al-rich, and hydrothermal fluids should be Mg- and Fe-poor.

Tv and cv smectites of volcanic origin differ in terms of octahedral cation composition and distribution of isomorphous octahedral cations. Mg-rich cv smectites have random distribution of isomorphous octahedral cations, whereas in Mg-bearing tv smectites octahedral Mg cations are dispersed so as to minimize the amount of Mg-OH-Mg arrangements.

Layered metal hydroxides exhibit non-uniform broadening of lines in their X-ray powder diffraction (XRPD) patterns, which cannot always be explained on the basis of crystallite size effects. In the case of hexagonal solids such as nickel hydroxide, DIFFaX simulations of the XRPD patterns show that: (1) stacking faults and turbostratic disorder at low (<30%) incidence selectively broaden the h0l reflections; (2) turbostratic disorder at high (>40%) incidence causes asymmetric broadening of the hk0 reflections and a complete extinction of the hkl reflections while leaving 00l unchanged; (3) interstratification selectively broadens the non-hk0 reflections; and (4) cation vacancies reduce the relative intensity of the 100 reflection. In contrast, a reduction in the thickness of the crystallites along the stacking direction of the layers selectively broadens the 00l reflections while a reduction in the disc diameter causes the progressive broadening and extinction of the hk0 reflections. Comparison with experimental data shows that several kinds of disorders have to be invoked to account for the observed broadening. DIFFaX simulations enable the quantification of the different kinds of disorder.

The structures of Fe-rich chlorite and berthierine and the formation mechanisms of 7 Å–14 Å interstratified minerals were not previously fully understood owing to the difficulties in analyzing them by X-ray diffraction (XRD). The present study characterizes Fe-rich chlorites in quartz veins of epithermal to xenothermal vein-type ore deposits without later structural modifications, based on high-resolution transmission electron microscopy (HRTEM) along with XRD examination and chemical analysis. Samples have a wide range of Fe/(Fe+Mg) ratios from 0.38 to 0.98 and tetrahedral Al substitution for Si from 0.94 to 1.44 atoms per formula unit (apfu). The variation in Fe content nearly parallels the tetrahedral Al content. The formation temperatures estimated by chlorite geothermometry range from 190°C to 320°C. In HRTEM, most of the samples showed interstratification between 7 Å, 14 Å, and/or (in some samples) smectite layers. Chlorites with relatively low Fe contents (Fe/(Fe+Mg) ≈ 0.4) were characterized by mostly 14 Å periodicity with the polytype IIbb. In contrast, interstratification of 7 Å and 14 Å layers predominated with increasing Fe content and the proportion of 7 Å layers exceeds 80% in Fe-rich samples with Fe/(Fe+Mg) > 0.9. The 7 Å component layer approximated Fe-rich berthierine based on the chemical composition. Layer stacking structures in the Fe-rich samples were complex, and characterized by disorder of 7 Å and 14 Å layers, differences in the polarity of the tetrahedral sheets, variations of the slant of the octahedral sheets, and positional disorder between octahedral and tetrahedral sheets involving the hydrogen bonding, as indicated from HRTEM observations along the Yi directions of the phyllosilicates. The complex stacking structures observed in Fe-rich samples suggest that irregularity was controlled by neither the Fe/(Fe+Mg) ratio nor the formation temperature; stacking was controlled by kinetic factors in the process of mineral precipitation under disequilibrium conditions.

The paper re-examines the parable of the king pondering about engaging in war with a more powerful enemy (Luke 14.31–2), focusing on questions commonly asked in antiquity and still relevant today with respect to war and suing for peace. These regard the cause of the war and the reasons for fighting, the tension between bravery and wisdom, the circumstances that may contribute to the defeat of a superior army and the costs of peace making. I explore this parable in the context of other Lukan passages touching on the topic of war and peace. I challenge the assumption that Luke was a pacifist, and I argue that the parable cannot provide answers to contemporary questions about the ethics of peace and war.

Factors controlling the crystal structure of phlogopite have been widely investigated; but the role of electrostatic interactions, for example, has received much less attention than other factors. The purpose of the present study was to peform a single-crystal refinement of an Al-saturated phlogopite and to use that refinement to supplement crystal-chemical analyses. The phlogopite investigated was from the Rumford quadrangle, Maine, and has the following chemistry: ${\left({\text{K}}_{0.81}{\text{Na}}_{0.03}\right)}_{\Sigma =0.84}{\left({\text{Mg}}_{1.84}{\text{Fe}}_{0.52}^{2+}{\text{Al}}_{0.45}{\text{Mn}}_{0.02}{\text{Ti}}_{0.07}^{4+}\right)}_{\Sigma =2.90}{\left({\text{Si}}_{2.78}{\text{Al}}_{1.22}\right)}_{\Sigma =4}{\text{O}}_{10}{\left({\text{OH}}_{1.81},{\text{F}}_{0.05}\right)}_{\Sigma =1.86}$\$\end{document}. The sample is a 1M polytype with C2/m symmetry and cell dimensions of a = 5.3220(4), b = 9.2170(7), c = 10.2511(8) Å, and β = 100.081(1)°. Hydrogen atoms were located and the crystal structure was refined to give parameters R1 = 0.0301 and weighted R2 = 0.0887. The octahedral M1 site was larger than the M2 (average M1—O: 2.079 Å, average M2—O: 2.062 Å) and the electron counts were equal (M1 = M2 = 14.8 e−); based on bond distances, which are more accurate than electron counts in determining occupancy; this result is consistent with a slight preference of Mg for M2 and Fe2+ for M1.

Thirty-five Al-rich, natural phlogopite-1M samples that are of (1) high metamorphic grade, and that have (2) total Al contents ⩾ 1.27 atoms per formula unit (a.p.f.u.), (3) Fe3+ contents ⩽ 0.11 a.p.f.u., and (4) Mn contents ⩽0.10 a.p.f.u. along with the newly described phlogopite, exhibited crystal chemical trends related to increasing Al content. Octahedral substitutions of smaller, high-charge cations (i.e. Al) apparently decrease distortions in the octahedral sites and produce longer M2—O4 distances. In addition, VIFe-F avoidance apparently occurs in high Al-content samples, which are generally high in VIFe. The data set also shows that these samples have limited ordering among M sites (Fe2+ in M1 and Al in M2), an increase in β (99.96° to 100.32°) possibly caused by cation ordering and therefore size differences of M1 and M2, and interlayer (A) sites with A—Oouter distances that increase and A—Oinner distances that decrease with increasing Ti content.

Computer models were used to simulate electrostatic interactions in phlogopite structures with variable Al concentrations utilizing Pauling’s electrostatic valency principle, which considers first-coordination electrostatic interactions. The model results were compared to the maximum Al concentrations in natural and synthetic phlogopite samples. Model results revealed no indications (e.g. a limit reached or a sudden change occurred) that charge saturation/undersaturation of the apical oxygen atoms at Al contents equal to the maximum in natural and/or synthetic samples causes instability that could not be balanced by bond-length variation. However, a cation of higher charge substituting at M1 (or M2) may result in higher electrostatic repulsions between the other octahedral sites. Thus, the Al3+ content in the octahedral sites may reach a maximum, with Fe2+ for Mg substitutions favored.

We discuss a variant, named ‘Rattle’, of the product replacement algorithm. Rattle is a Markov chain, that returns a random element of a black box group. The limiting distribution of the element returned is the uniform distribution. We prove that, if the generating sequence is long enough, the probability distribution of the element returned converges unexpectedly quickly to the uniform distribution.

The morphology, dehydroxylation, and dissolution properties of single- and multi-metal (Cr, Zn, Cd, and Pb)-substituted goethites prepared using hydrothermal methods are reported. The crystal morphology varied with the nature and the number of metals present in the system. The presence of Cr produced broader crystals while Zn, Cd, and Pb produced narrower crystals than pure goethite. The presence of multiple metals retards the crystal growth of the mineral. Metal substitution caused changes in the unit-cell parameters and the infrared (IR) spectra of the samples. The IR spectra were also sensitive to the morphology of the crystals. The separation of γO and δOH bending frequencies increased with increase in area and aspect ratio of the (100) crystal face. The dissolution-kinetics studies (1 M HCl, 40ºC) of single-metal-substituted goethite provided the following dissolution rate order: Zn- > Pb(II)- ≥ Pb(IV)- > unsubstituted > Cd- > Cr-goethite. More complex results were obtained for the multi-metal-substituted samples. In the di-metal-substituted goethites, incorporation of Cr suppressed the dissolution rate of Zn-substituted goethite by 85% and Cd suppressed the dissolution rate of Zn-substituted goethite by 53%. Similarly, incorporated Cr and Cd suppressed the dissolution rate of Pb(II)-substituted goethite by 50%. The dissolution rates of multi-metal-substituted goethite were linearly related to the steric strains derived from the lattice parameters of the mineral. Dissolution studies also showed that Cr, Zn, Cd, and Pb(IV) were distributed homogeneously throughout goethite crystals while Pb(II) was enriched in the near-surface regions of the crystals. Incorporation of Cr and Pb(II) increased, while Zn and Pb(IV) decreased the dehydroxylation temperature of single-metal-substituted goethites. Incorporation of Zn suppressed the effect of Cr on the dehydroxylation temperature in multi-metal-substituted goethites.

A method for extracting Ni and other metals from lateritic ores by means of shock heating has been investigated. Shock heating releases some of the metal from its goethitic host. Even though the transformation of pure goethite to hematite is known to occur via intermediate hydroxylated phases, the effect of other metals such as Ni substituting for Fe in goethites on this thermal transformation to hematite is unknown. The purpose of this study was to fill this gap, with the hope that the results will lead to more energy-efficient extraction methods and/or a better understanding of Fe geochemistry in thermally activated soils. X-ray diffraction, transmission electron microscopy with EDS, and thermal analysis were used to investigate mineralogical changes in nickeliferous goethites from five oxide-type lateritic nickel ore deposits that had been subjected to shock heating at temperatures in the range 220–800°C. Acicular, nano-sized goethite was the main constituent of the samples with minor to trace amounts of quartz, talc, kaolinite, chromite, maghemite, and Mn oxides. Goethite was partially dehydroxylated to OH-hematite at 340–400°C and had completely altered to well ordered hematite at 800°C. The OH-hematite was characterized by broad XRD peaks for reflections associated with the Fe sublattice. The goethite unit-cell a and b lengths remained almost constant with increasing preheating temperature up to 300°C, while the size of the c axis dimension contracted. The neoformed hematite crystals were larger than the precursor goethite crystals due to development, by sintering and surface diffusion, of regularly ordered hematite domains. The increase (1.5–2.6 fold) in surface area with increasing heating temperature (up to 340–400°C) reflected the development of slit-shaped micropores (∼300°C), which further developed into elliptically shaped micropores (∼400°C) in OH-hematite. With increased heating temperature, well ordered hematite formed with only a few micropores remaining. Such results may contribute to the development of more efficient procedures for extracting Ni from lateritic nickel ores, as the rate of dissolution of goethite in acid in ‘heap and pressure’ leach facilities will be enhanced by the increases in surface area and microporosity. The results may also provide valuable information on the probable effects of natural heating on pedogenic Fe oxides.

This paper discusses the hitherto virtually unknown Byzantine cave monastery in the Ilgarini mağarası in the district of Pınarbaşı/Kastamonu based on its building remains, graffiti (mostly crosses), burials and notable finds. The remains were recorded during two brief surveys in 2012 and 2022. To shed light on the history of the site, an attempt is made to contex- tualise it within the mountainous regions of Middle Byzantine Paphlagonia, as well as with Middle Byzantine texts that relate to monasticism and might refer to the site. Research produces tentative evidence that the Ilgarini mağarası may be identified with the Chryse Petra known from several Byzantine texts, most prominently the Life of St Nikon Metanoite.