For more than forty years, The Clay Minerals Society has dispensed a set of source clays which have enabled a large number of researchers to work on similar materials. Many of these source clays remained unchanged over the years but, conversely, other clays have gone out of stock and thus were replaced. This was the fate of montmorillonite STx-1a, which was replaced by STx-1b. Although STx-1a and STx-1b share many basic chemical and mineralogical features, some minor differences exist that can affect behavior. A baseline characterization of the source clay STx-1b, which was the objective of this study, was, therefore, necessary to provide researchers a tool useful not only for new investigation but also to compare new results obtained on STx-1b with literature data on STx-1a. This characterization was gained using traditional and advanced methods that included: 1) chemical composition (major and trace elements); 2) cation exchange capacity determination; 3) thermal analyses coupled with evolved gas mass spectrometry; 4) quantitative mineralogical characterization using powder X-ray diffraction and Rietveld- RIR (Reference Intensity Ratio) refinement; 5) X-ray absorption spectroscopy at the Fe K-edge; 6) diffuse reflectance ultraviolet-visible and infrared spectroscopies; and 7) 29Si, 27Al, and 1H magic-angle spinning nuclear magnetic resonance measurements. According to this multi-analytical approach, the chemical formula for STx-1b is [4](Si7.753Al0.247) [6](Al3.281Mg0.558Fe0.136Ti0.024Mn0.002) [12](Ca0.341Na0.039 K0.061)O20(OH)4.

Sepiolite is a fibrous clay mineral and consists of 2:1 silicate blocks connected at the corners and separated by tunnels (channels on external surfaces) that extend in the direction of fiber length. The tunnels, 3.7 Å × 610.6 Å in cross-section, are responsible for the incorporation of organic and inorganic compounds. The present study aimed to examine the capacity of twelve different organic molecules, such as pyridine, indigo, methylene blue, and quaternary amines, to gain access to the tunnels of sepiolite using quantum chemistry techniques. The interaction energy computations performed at the B97-D/TZVP level showed that all of the considered organic molecules tend to access the tunnels of sepiolite if external water molecules are absent. This finding is in agreement with experimental studies that included pyridine, indigo, 2,2-bipyridyl, and methylene blue. Interestingly, 2,6-dimethyl pyridine preferred to remain in a tunnel rather than an external channel of the sepiolite.

Widespread alteration in the Miocene lacustrine volcanic/sedimentary rocks of the Ankara-Çankiri basin of central Anatolia has resulted in the formation of sizeable (economic) quantities of bentonite deposits. No detailed characterization of the geological, mineralogical, and geochemical properties or the depositional environments of these primary and secondary bentonite deposits has been carried out to date. The present study was undertaken to close this knowledge gap. Two possible hypothetical processes were examined to explain the genesis of the bentonites: 1) The bentonites were formed by the devitrification of volcanic glass in a lacustrine setting; and 2) The bentonites were formed by the chemical weathering of previously deposited volcaniclastic sediments and ophiolitic materials. The characteristics of the bentonites were examined using X-ray diffractometry, scanning and transmission electron microscopy, energy dispersive spectroscopy, and chemical analyses of major and trace elements. The Ankara-Çankırı bentonites are found gradationally interbedded with parent Miocene volcanic and volcaniclastic rocks. These bentonites were deposited in a shallow lacustrine setting based on observed desiccation cracks, locally enclosed coal seams, plant rootlets, gypsum lenses, yellow sulfate-like fracture infillings, and ferric iron oxide stains. Smectite resulted from the chemical weathering of feldspar and possibly also the weathering of biotite and hornblende. This smectite was precipitated in situ on partially dissolved glass and feldspar. The average major-element composition of the smectite-rich clay fractions yielded the following montmorillonitic smectite structural formula: (Na0.33Ca0.31K0.18) (Al2.35Fe0.80Mg0.78)(Si7.79Al0.21)O20(OH)4.

The interlayer cation occupancy in the smectite-rich clay fractions was based on the use of Na+/(Na++Ca2+) ratios and showed a composition between a Ca-smectite and a Na-smectite. The relative increases in several groups of elements according to the LREE/(MREE+HREE) ratio, Al2O3, the sum of Ni+Co+Cr, the sum of Fe2O3+MgO+TiO2, the positive correlation between Rb+Ba and Na2O+K2O, Sr and Rb, Rb/Sr and Zr, Zr/Sm and SiO2, the negative Eu anomaly, and the field and petrographic observations further showed that the Si, Al, Fe, and Mg required to form smectite were mainly supplied from the decomposition of feldspars, amphiboles, and volcanic glass from volcanic materials and were partially supplied from the chemical weathering of ophiolitic basement units. The bentonite deposits examined in this study are mainly primary bentonites derived from volcanics and local secondary bentonites from previously deposited volcaniclastic sediments and ophiolitic materials.

As one of the strongest inorganic oxidizers in natural environments, manganese oxides participate in the oxidation processes of dissolved sulfides, affecting their migration, transformation, and toxicity. The amount of and sites for Mn(III) influence significantly the oxidation activity of Mn(IV) oxides. As an easily formed Mn oxide in supergene environments, manganite consists of Mn(III)O6 octahedra; further study is needed of the interaction processes of manganite and dissolved sulfide. In the present study, the interaction mechanisms of dissolved sulfide and manganite were studied systematically. The influences of pH, temperature, and oxygen atmosphere were also investigated in detail. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the crystal structures, compositions, and micromorphologies of manganite and the intermediate products. The sulfide species were identified by visible spectroscopy, high-performance liquid chromatography, UV-visible (UV-Vis) spectroscopy, and ion chromatography during the reaction process. The results indicated that in a nitrogen atmosphere, elemental sulfur was formed as the main oxidation product of dissolved sulfide by manganite at the initial stage, and polysulfide ions were observed as the intermediates. Elemental sulfur was further oxidized slowly to S2O32−. The initial oxidation rate of dissolved sulfide by manganite increased with temperature from 20 to 40°C. The reaction rate increased at first and then decreased as the pH changed from 4.0 to 12.0, and the greatest oxidation rate was achieved at pH 8.0. In the presence of oxygen, S2O32− was the main product. The oxidation rate of dissolved sulfide decreased, and manganite exhibited significant catalytic activity and stability with respect to the oxidation of dissolved sulfide in the oxygenated aqueous systems. These findings are of fundamental significance in understanding the interaction and transformation of dissolved sulfide and manganese oxides in nature.

In order to understand the microscopic properties of alkylammonium-intercalated vermiculites, molecular dynamics simulations employing the clayff-CVFF force field were performed to obtain the interlayer structures and dynamics. The layering behavior of alkyl chains was uncovered. With the model used in the present study (1.2 e per unit cell), the alkyl chains formed monolayers with carbon-chain lengths of C6, bilayers from C7 to C10, and pseudo-trimolecular layers from C15 to C18. Intermediate states also existed between bilayer and pseudo-trimolecular layer states from C11 to C14. The ammonium groups had two locations: most ammonium groups were located over the six-member rings (~90%), and the rest above the substitution sites (~10%). The ammonium groups interacted with the vermiculite surface through H bonds between ammonium H atoms and surface O atoms. The ammonium groups were fixed firmly on surfaces and, therefore, had very low mobility. The alkyl chains were slightly more mobile. The similarities and differences between alkylammonium-intercalated vermiculites and smectites were revealed. The layering behaviors of alkyl chains were similar in alkylammonium-intercalated vermiculites and smectites: the alkyl chain behavior was controlled by both the amount of layer charge and the carbon chain length. The distributions of ammonium groups, however, were different, caused by the layer-charge distribution in vermiculites being different from that in smectites. The atomic-level results derived in the present study will be useful for future research into and the applications of organo-vermiculites.

Monochloroanilines and dichloroanilines are important reagents or chemical intermediates in the production of dyes, pharmaceuticals, and agricultural chemicals. These toxic compounds have a large tendency to accumulate in the environment and a low natural biodegradability, so improved methods to remove or sequester them are needed. Halloysite is used as an efficient adsorbent to remove toxic compounds, such as aniline, from aqueous solutions. The purpose of this study was to evaluate whether acid-activated halloysites from the “Dunino” (Poland) strip mine could be effective in the removal of not just aniline but also of its chloro-substituted forms from aqueous solutions. The composition, structure, and morphology of activated halloysites were characterized using the following methods: wavelength dispersive X-ray fluorescence analysis (WDXRF), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), and N2 adsorption-desorption analysis. The acidactivated halloysites had an increased ability to remove aniline and chloroanilines from aqueous solutions as the acid activation temperature was increased. This suggests that the acid activation temperature is an important factor that influences the ability of acid activated halloysites to adsorb aromatic amines (anilines) from water. The efficiency of aniline and chloroaniline removal by halloysite activated at 80°C reached maximum levels, especially for the removal of aniline and 4-chloroaniline. The adsorption isotherm data were best described by the Langmuir adsorption model. The values of the Langmuir adsorption constants were calculated using the inverse liquid chromatography method.

Iron-bearing K-dioctahedral 1M and 1Md micas are abundant in diverse geological environments and vary in composition from illite to celadonite through Fe-illite, Al-glauconite, and glauconite. The chemistry and structural features of these micas are complex and heterogeneous, reliable diagnostic criteria are lacking, and the conventional mineralogical nomenclature is ambiguous, which complicate the identification of these mica varieties. The objectives of the present study were to reveal the structural and crystal-chemical variability in Fe-bearing, K-dioctahedral 1M micas and to define composition ranges and identification criteria for the mica varieties in the series. A collection of samples of various compositions was studied using X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. Analysis of the relationships between unit-cell parameters and cation composition showed that the series included four groups, namely, Fe-bearing illites, Al-glauconites, glauconites, and celadonites and each group was characterized by a specific combination of unit-cell parameters and variation ranges. The illite group contained two distinct subgroups; Fe-bearing, Mg-rich illites and Feillites; which differ in the range of cation compositions and in FTIR characteristics. The boundary between Fe-illites and Al-glauconites occurs at a unit cell b value of ~9.05 Å and at ratios of octahedral Al to total trivalent octahedral cations that range between 0.60 and 0.65. The partially overlapping cation composition and cell parameter ranges may complicate the distinction between Al-glauconites and glauconites, which can still be unambiguously differentiated using FTIR data. The dramatically different XRD and FTIR characteristics confirmed that glauconite and celadonite should be treated as separate mineral species. The distinctive features of celadonite are relatively low csinβ values and reduced |ccosβ/a| values combined with b parameters lower than glauconites, but similar to Fe-illites. Celadonites also have distinct and sharp FTIR absorption bands at specific positions in the Si-O and OH stretching regions.

Although low density polyethylene (LDPE) has long been widely used in packaging applications, some limitations in its use still exist and are due to its relatively poor gas barrier properties and low mechanical strength which can restrict its extensive use for more advanced applications, such as electronic and pharmaceutical packaging. The purpose of this study was to investigate the possibility of using montmorillonite (MMT) nanoclay as a means to enhance the thermal, mechanical, and barrier properties of LDPE prepared via melt extrusion. The level of exfoliated dispersion of the MMT nanoclay in the prepared LDPE-MMT composite was confirmed using transmission electron microscopy (TEM). The relationship between the resulting morphology and the thermal, mechanical, and barrier properties as a function of the MMT content was evaluated. The results showed that incorporating >3 wt.% of MMT nanoclay produced significant changes in the morphology of the LDPE-MMT nanoclay composite in that the segregated matrix adopted an oriented arrangement of exfoliated clay platelets. Thermogravimetric analysis (TGA) showed that the thermal stability of LDPE improved significantly as a result of MMT nanoclay incorporation. Furthermore, differential scanning calorimetry (DSC) analysis indicated that increasing clay content above 3 wt.% effectively reduces the crystallinity of LDPE-MMT composites through the suppression effect. The tensile strength of LDPE increased gradually with an increased content of MMT nanoclay and the maximum value of 16.89 N/mm2 was obtained at 10 wt.% MMT content. This value represents a 40.87% increase relative to the tensile strength of the pristine LDPE. Barrier properties of LDPE and LDPE-MMT nanoclay composites were assessed by examining the permeability with respect to oxygen and water vapor. As the content of MMT nanoclay was increased to 10 wt.%, the permeability of the nanocomposite films to oxygen and water vapor notably decreased to 42.8% and 26.2%, respectively.

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.

Layers of volcanic ash and Andosol soils derived from the ash may play an important role in preserving snow and ice as well as in the development of permafrost conditions in (a) the immediate vicinity of volcanoes at high elevations or at high latitudes and (b) land areas that are often distant from volcanic activity and are either prone to permafrost or covered by snow and ice, but have been affected by subaerial ash deposition. The special properties of volcanic ash are critically reviewed, particularly in relation to recent research in Kamchatka in the Far East of Russia. Of special importance are the thermal properties, the unfrozen water contents of ash layers, and the rate of volcanic glass weathering.Weathering of volcanic glass results in the development of amorphous clay minerals (e.g. allophane, opal, palagonite), but occurs at a much slower rate under cold compared to warm climate conditions. Existing data reveal (1) a strong correlation between the thermal conductivity, the water/ice content, and the mineralogy of the weathered part of the volcanic ash, (2) that an increase in the amounts of amorphous clay minerals (allophane, palagonite) increases the proportion of unfrozen water and decreases the thermal conductivity, and (3) that amorphous silica does not alter to halloysite or other clay minerals, even in the Early Pleistocene age (Kamchatka) volcanic ashes or in the Miocene and Pliocene deposits of Antarctica due to the cold temperatures. The significance of these findings are discussed in relation to past climate reconstruction and the influence of volcanic ash on permafrost aggradation and degradation, snow and ice ablation, and the development of glaciers.

The Lower Pliocene lacustrine sediments of the Sakarya and Porsuk Formations in the Sivrihisar and Yunusemre-Biçer regions consist of claystone, argillaceous carbonate, carbonate, and evaporites. No detailed studies of paleoclimatic conditions have been performed previously. The present study aimed to determine the depositional environment and paleoclimatic conditions for the formation of these economically important sepiolite/palygorskite/carbonate/evaporite deposits based on detailed mineralogical, geochemical, and isotopic studies. Samples from various lacustrine sediments were examined using polarized-light microscopy, X-ray diffraction, scanning electron microscopy, and chemical and isotopic analysis methods. Dolomites are predominantly of micrite, which is partly recrystallized to dolomicrosparite/dolosparite close to desiccation fractures. The presence of ostracods and dacycladecean algae in the carbonates reflects a restricted depositional environment. The formation of sepiolite and palygorskite fibers, either as cement between/enclosing dolomite and/or as calcite crystals, reflects occasional changes in physicochemical conditions provided by fluctuations in the lake-water level and influx of groundwater in relation to climatic changes during and after dolomite precipitation. The positive correlations of ΣREE with Al2O3, Nb, high-field-strength elements, and transition elements are due to alteration of feldspar and hornblende in the volcanic units. The high values of Ba and Sr relative to Cr, Co, Ni, and V also indicate that felsic rather than ophiolitic rocks were the parent material. The crossplot of whole-rock SiO2vs. Al2O3+K2O+Na2O and V/Cr ratio suggests deposition of carbonate-dolomitic sepiolite-sepiolitic dolomite under arid climate and oxic conditions, whereas the Ni/Co and V/(V+Ni) ratios of the sediments indicate deposition of organic-bearing sepiolite/palygorskite under anoxic-dysoxic conditions. An enrichment in δ13C and δ18O values of dolomite with respect to calcite is probably due to differences in mineral fractionations. The δ34S and δ18O values and 87Sr/86Sr isotope ratios for gypsum suggest an intensely evaporitic lacustrine environment fed by an older marine evaporitic source. The Si, Al, Mg, Ca, and enhanced TOT/C required for periodic precipitation of organic-rich brown sepiolite/palygorskite characterize deposition in a swampy environment, while dolomitic sepiolite and sepiolitic dolomite formed in ponds by partial drying of the main alkaline lake.

Atomic force microscopy (AFM) is a novel method for measuring changes in clay swelling in situ at the tactoid level in an aqueous environment. While the swelling process has been directly observed at the mesoscale level for multi-tactoid aggregates and the associated pores, no method to date has allowed the direct observation of swelling dynamics at the nanoscale. In initial proof-of-concept studies, individual tactoids of a Na-exchanged nontronite (NAu-1) were imaged in a solution of 5 mM NaCl. When multiple line profiles were examined on the same tactoid, the changes in height varied and depended on which layers of the profile were transected, and demonstrated that AFM analyses can be used to directly probe intratactoid heterogeneity in the swelling process. To better visualize this heterogeneity, a method was developed to restrict AFM images to include only the portions of a tactoid above a threshold height. A comparison of the changes in these images for multiple threshold values revealed that swelling in one part of a tactoid may occur simultaneously with compression in another portion, which suggests that the encroachment of layers into intra-tactoid micropores can partially compensate for the overall volume change. Finally, to demonstrate the ability of this technique to monitor in situ swelling changes as the surrounding aqueous environment is modified, a tactoid of K-montmorillonite (SWy-2) was monitored during cation exchange as a KCl solution was replaced with NaCl. After exchange, a transition from the crystalline swelling regime to the osmotic regime was observed. Subsequent height profiles were unchanged for a period of several hours and indicated that the AFM measurements were stable in the absence of changes to the aqueous phase composition. Because this technique is the first method that allows the swelling of a single tactoid to be monitored in an aqueous solution, it complements the ensemble-averaged data obtained from diffraction and scattering techniques.

The reactivity and stability of the edge faces of swelling clay minerals can be altered by layer charge and the stacking structure; however, these effects are poorly understood due to experimental limitations. The structure and stability of the montmorillonite {110}, {010}, {100}, and {130} edge faces with a layer charge of either y = 0.50 or y = 0.33 (e−/Si4O10) were investigated using first-principles calculations based on density functional theory. Stacked- and single-layer models were tested and compared to understand the effect of stacking on the stability of montmorillonite edge faces. Most stacked layers stabilize the edge faces by creating hydrogen bonds between the layers; therefore, the surface energy of the layers in the stacked-layer model is lower than in the single-layer model. This indicates that the estimates of edge face surface energy should consider the swelling conditions. Negative surface energies were calculated for these edge faces in the presence of chemisorbed water molecules. A high layer charge of 0.50 reduced the surface energy relative to that of the low layer charge of 0.33. The isomorphic substitution of Mg for Al increased the stability of interlayer Na ion positions, which were stable in the trigonal ring next to the Mg ions. The lowest surface energies of the {010} and {130} edge faces were characterized by the presence of Mg ions on edge faces, which had a strong cation adsorption site due to the local negative charge of the edges. The coordination numbers of O atoms around cations adsorbed to these edge faces were small in comparison to interlayers without water.

The alignment of phyllosilicates in clays has received a lot of attention because it is a major cause of seismic anisotropy in the Earth’s crust. Thus far, all attention has been on shales where the orientation pattern has been attributed to compaction and observed to increase with burial depth and diagenetic processes. Here, for the first time, the same methods that were developed to quantify shale preferred orientation were applied to clays forming in surface environments, a seasonal streambed in Death Valley, California; a mudpool from mud volcanoes in Imperial Valley, California, close to the Salton Sea; and a glacial lake from Val Albigna in the Swiss Alps. Preferred orientation was analyzed quantitatively with high-energy synchrotron X-ray diffraction. All three samples showed strong alignment of phyllosilicates with (001) pole figure maxima 2–4 multiples of a random distribution, comparable to shales, and indicating that significant preferred orientation can be produced at surface conditions. The original alignment during sedimentation may be an important factor for the final microstructure in many shales.

Buckminsterfullerene (C60) is one of the most important carbon-based nanoparticles (CNPs). Industrial-scale production of C60 has reached the level of tons; release to the environment has been confirmed (Tremblay, 2002; Qiao et al., 2007). The present study was devoted to study of the effect of clay minerals on the migration process of C60. Molecular dynamics (MD) simulations were used to study the interaction of CNPS with clay minerals through study of the adsorption of C60 on various surfaces of kaolinite and pyrophyllite in vacuum and aqueous environments. Two kinds of surfaces, hydrophobic siloxane surfaces and hydrophilic hydroxyl surfaces, were investigated. C60 is mainly adsorbed onto the vacancy of the six-membered ring, composed of SiO4 tetrahedra or AlO6 octahedra, on clay-mineral surfaces. A single adsorption layer consisting of C60 molecules with an ordered hexagonal arrangement is presented for all surfaces in vacuum. In aqueous environments, however, the monolayer appears on the siloxane surfaces only, while a cluster of C60 molecules is formed on the hydroxyl surfaces. Free energies prove that the attachment of two C60 molecules is stronger than the adsorption of C60 onto the hydroxyl surface in water, which is the reason for unfavorable formation of C60 monolayer. On the other hand, the adsorption free energy is more negative on the hydrophobic siloxane surface, explaining the monolayer formation. The existence of water, which forms hydration layers on the surfaces of clay minerals, produces energy barriers, and reduces the adsorption affinity to some extent. Because clay minerals act as geosorbents in the environment, the present study is significant in terms of understanding the migration and fate of CNPS in nature.

The performance of bentonite barriers for high level radioactive waste (HLRW) disposal is currently being tested in various real-and up-scale disposal tests. One of the disposal tests, the ABM test (ABM = alternative buffer material), was conducted by SKB (Svensk Kärnbränslehantering) as a mediumscale experiment at the Äspö hard rock laboratory in Sweden. The present study deals with the second parcel (ABM-II), which was retrieved after 6.5 years with 2.5 years of water saturation and 3–4 years of heating up to 141°C. Nine different bentonites and two marine clays were tested to investigate the performance. The aim of the study was to provide a detailed characterization of the mineralogical and chemical changes that took place in ABM-II, compare the findings with ABM-I (the first of the six test parcels), and try to draw some general conclusions concerning the use of bentonites in such geotechnical barriers. The ABM-II test parcel revealed a set of reactions that a HLRW bentonite might undergo. The most prominent reaction was the rather complete exchange of cations, which was discussed in a second part to this publication (II — cation exchange; Dohrmann and Kaufhold, 2017). The corrosion of the Fe in metal canisters was observed, but no discrete corrosion product was identified. At the interface of bentonite and the metal canister, the formation of smectite-type trioctahedral clay minerals was observed. In contrast to the ABM-I test, anhydrite was present in many of the bentonite blocks of the ABM-II test. In most concepts used for HLRW disposal in crystalline rocks, a temperature below 100°C at the canister surface was applied to avoid boiling. In the ABM-II test, boiling of water was possibly observed. Throughout the experiment, a pressure/water loss was recorded in the upper part of the geotechnical barrier and water was added to maintain pressure in the bentonite. As a result of evaporation, NaCl crusts might have formed and the barrier was partly disintegrated. These results demonstrated that a reasonable assumption is that no boiling of water occurs in disposal concepts in which a pressure loss can occur.

The adsorption properties of clay minerals (e.g. montmorillonite and palygorskite) have been improved through chemical treatment methods. However, the addition of extra chemicals is often not friendly to the environment and powdered clay-mineral adsorbents are inconvenient for some applications. To overcome these drawbacks in the present study, granular montmorillonite-palygorskite adsorbents (GMPA) were successfully prepared using Na-alginate and thermal treatments to improve heavy metal removal from water. The properties of GMPA samples under different calcination temperatures were examined using thermogravimetric (TG) analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD), and specific surface area (BET). The results indicated that loss of mass by GMPA relative to the untreated montmorillonite-palygorskite was due to the loss of water, adsorbed Na-alginate, and mineral decomposition during thermal treatment. Changes in the morphology and crystallinity were significant at calcination temperatures from 500°C to 1000°C. The layered morphology totally disappeared after calcination at 1000°C, while transformation of the montmorillonite and palygorskite to a non-crystalline material was almost complete at 800°C and new crystalline phases appeared. Calcination temperature had a significant influence on the specific surface areas and pore volumes of GMPA. Both the changes in texture and chemical structure affected Pb2+ and Cu2+ removal. The GMPA sample produced at a 600°C calcination temperature was the most promising adsorbent for heavy metal removal from water.

Bentonites are candidate materials for encapsulating radioactive waste within barrier systems in crystalline rocks. In the ‘Alternative Buffer Material’ (ABM) test in the hard rock laboratory in Äspö, Sweden, six packages of eleven different buffer materials (mainly bentonites) with various exchangeable cation populations were packed vertically with an iron tube used as a heater in the center. After installation, the second ‘ABM package’ (ABM-II) was first allowed to saturate with water for approximately 2.5 years. The blocks were then exposed to a temperature of up to 141°C for approximately 3–4 years. The hypotheses for the present study were: (1) no horizontal gradient of the cation exchange population was present in the individual blocks of ABM-II because ABM-II had a longer reaction time in comparison to the ABM-I package, which did not have horizontal gradients; (2) the exchangeable cation Ca2+:Na+:Mg2+ ratio was equal in all blocks of ABM-II and was independent of block position in the package. As expected from ABM-I, all blocks in the ABM-II experiment showed large differences between the measured values of the reference materials and the reacted samples. The exchangeable Na+ and Mg2+ values in ABM-II were reduced by up to 55% to 59% in comparison to the reference material. Contrary to the first hypothesis, horizontal gradients were observed in ABM-II; and, contrary to the second hypothesis, the exchangeable cation ratios differed markedly in the different reacted buffer materials. The largest total Na+ loss was observed in the middle part (-67%), whereas Mg2+ values decreased by 79% in the upper part. The exchangeable Ca2+ values increased strongly in ABM-II, particularly in the upper part. The most useful parameter to distinguish between ion exchange equilibria of ABM-I and ABM-II was the Na+/Mg2+ ratio. This ratio was constant in ABM-I (3.0) and had a similar ratio (3.5) in the lower part of ABM-II; however, the ratio strongly increased (5–10) in the upper part of the ABM-II package. The large Na+/Mg2+ ratios in the upper part of ABM-II could possibly be explained by water loss into the rock (caused by a pressure drop and boiling) and subsequent water uptake.

In 2000, The Clay Minerals Society established a biennial quantitative mineralogy round robin. The so-called Reynolds Cup competition is named after Bob Reynolds for his pioneering work in quantitative clay mineralogy and exceptional contributions to clay science. The first contest was run in 2002 with 40 sets of three samples, which were prepared from mixtures of purified, natural, and synthetic minerals that are commonly found in clay-bearing rocks and soils and represent realistic mineral assemblages. The rules of the competition allow any method or combination of methods to be used in the quantitative analysis of the mineral assemblages. Throughout the competition, X-ray diffraction has been the method of choice for quantifying the mineralogy of the sample mixtures with a multitude of other techniques used to assist with phase identification and quantification. In the first twelve years of the Reynolds Cup competition (2002 to 2014), around 14,000 analyses from 448 participants have been carried out on a total of 21 samples. The data provided by these analyses constitute an extensive database on the accuracy of quantitative mineral analyses and also has given enough time for the progression of improvements in such analyses. In the Reynolds Cup competition, the accuracy of a particular quantification is judged by calculating a “bias” for each phase in an assemblage. Determining exactly the true amount of a phase in the assemblage would give a bias of zero. Generally, the higher placed participants correctly identified all or most of the mineral phases present. Conversely, the worst performers failed to identify or misidentified phases. Several contestants reported a long list of minor exotic phases, which were likely reported by automated search/match programs and were mineralogically implausible. Not surprisingly, clay minerals were among the greatest sources of error reported. This article reports on the first 12 years of the Reynolds Cup competition results and analyzes the competition data to determine the overall accuracy of the mineral assemblage quantities reported by the participants. The data from the competition were also used to ascertain trends in quantification accuracy over a 12 year period and to highlight sources of error in quantitative analyses.

Soil aggregates consist of sand, silt, and clay size particles. Many of the clay size particles in soils are clay minerals, which actively influence soil behavior. The properties of clay minerals may change significantly as soil particle size decreases to the nanoscale; however, little information is available about these properties for the Ultisols in China. In the present study, the clay mineral components and structural characteristics of four particle-size fractions (i.e., <2000, 450–2000, 100–450, and 25–100 nm) of two Ultisol samples (Ult-1 and Ult-2) were investigated using elemental analysis, X-ray diffraction, Fouriertransform infrared spectroscopy, and thermal analysis. The molar SiO2 to Al2O3 ratios were lower in the nanoscale particle-size fraction (25–100 nm) than in the 450–2000 and <2000 nm fractions. This indicates greater desilicification and allitization of the smaller Ultisol particles. Furthermore, the Fe oxide and Al oxide contents increased and reached a maximum level in the 25–100 nm fraction of the two Ultisols. Goethite was mainly found in the 100–450 nm and 25–100 nm fractions. The dominant clay minerals in the Ultisol 25–100 nm fraction were kaolinite and illite with a small amount of a hydroxy-interlayered mineral in Ult-1 and gibbsite in Ult-2. The kaolinite crystallinity decreased as particle size decreased. The low crystallinity of the kaolinite in the A horizon 25–100 nm fraction was attributed to a reduction in the thickness of coherent scattering domains, as well as to decreases in OH groups and the dimensions of octahedral AlO6 sheets. A determination of the chemical and mineralogic properties of the different size fractions of the Ultisols is important to understand the desilicification and Al and Fe oxide enrichment mechanisms during soil formation. The significance of these results can help to reveal the nanoscale transformations of clay minerals. Analysis of clay mineral compositions in nanoparticles can provide the additional data needed to understand the adsorption and mobility of nutrients and pollutants.