The Antalya Unit, one of the allochthonous units of the Tauride belt, is of critical, regional tectonic importance because of the presence of rifting remnants related to the break-up of the northern margin of Gondwana during Triassic time. Paleozoic — Mesozoic sedimentary rocks of the Antalya Unit consist mainly of calcite, dolomite, quartz, feldspar, and phyllosilicate (illite-smectite, smectite, kaolinite, chlorite, illite, chlorite-smectite, and chlorite-vermiculite) minerals. Illite-smectite (I-S) was found in all of the sequences from Cambrian to Cretaceous, but smectite was only identified in Late Triassic-Cretaceous sediments. R0 I-S occurs exclusively in early-diagenetic Triassic—Cretaceous units of the Alakırçay Nappe (rift sediments), whereas R3 I-S is present in late-diagenetic to low-anchimetamorphic Cambrian—Early Triassic units of the Tahtalıdağ Nappe (pre-rift sediments). Kübler Index (KI) values and the illite content of I-S reflect increasing diagenetic grades along with increasing depth. Major-element, trace-element, rare-earth-element (REE), and stable-isotope (O and H) compositions were investigated in dioctahedral and trioctahedral smectites and I-S samples from the pre-rift and rift-related formations. Both total layer charge and interlayer K increase, whereas tetrahedral Si and interlayer Ca decrease from smectite to R3 I-S. Trace-element and REE concentrations of the I-S are greater in pre-rift sediments than in rift sediments, except for P, Eu, Ni, Cu, Zn, and Bi. On the basis of North American Shale Composite (NASC)-normalized values, the REE patterns of I-S in the pre-rift and rift sediments are clearly separate and distinct. Oxygen (δ18O) and hydrogen (δD) values relative to SMOW (Standard Mean Oceanic Water) of smectite and I-S reflect supergene conditions, with decreasing δ18O but increasing δD values with increasing diagenetic grade. Lower dD values for these I-S samples are characteristic of rift sediments, and pre-rift sediments have greater values. On the basis of isotopic data from these I-S samples, the diagenesis of the Antalya Unit possibly occurred under a high geothermal gradient (>35ºC/km), perhaps originating under typical extensional-basin conditions with high heat flow. The geochemical findings from I-S and smectites were controlled by diagenetic grade and can be used as an additional tool for understanding the basin maturity along with mineralogical data.

Enhancement of the physico-chemical properties of elastomers can be achieved by the addition of fillers, such as silica, but the search for less expensive alternative materials continues. The objective of this study was to investigate natural or organically modified clay minerals as such an alternative. Organo-clays modified by quaternary ammonium cations with three methyl groups and longest alkyl chains of different lengths were prepared by ion-exchange reaction of the commercial product JP A030 (Envigeo, Slovakia) based on Jelšový Potok bentonite with organic salts: tetramethylammonium (TMA) chloride, octyltrimethylammonium (OTMA) bromide, and octadecyltrimethylammonium (ODTMA) bromide. Physico-chemical characterizations of the organo-clays used as fillers in rubber nanocomposites and their mechanical properties were measured using Fourier transform infrared (IR) spectroscopy, which provided information on the chemical composition of the mineral and on the amount of organic moieties adsorbed. X-ray diffraction analysis (XRD) was used to monitor the arrangement of organic chains in galleries of montmorillonite and showed that the longest-chain alkylammonium ODTMA+ ions were intercalated between layers, adopting a pseudotrimolecular conformation, while OTMA+ and TMA+ were in monomolecular arrangement. Surface areas were measured by sorption of N2 and ethylene glycol monoethyl ether. Natural rubber-clay nanocomposites were prepared by melt intercalation, in some cases also with addition of silica, a conventional reinforcing filler. The microstructure of montmorillonite in these composites was characterized by XRD analysis. The effect of clay and organo-clays loading from 1 to 10 phr (parts by weight per hundred parts of rubber) on stress at break, strain at break, and Modulus 100 (M100) was investigated by tensile tests. Filler ODTMA-JP A030 appears to be the most effective among the organoclays; surprisingly similar values of composite elongation and strength were obtained with unmodified bentonite JP A030.

The adsorption of hexadecyltrimethylammonium (HDTMA) in smectite was studied by adsorption isotherms, X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Smectites that had reacted for 48 h with HDTMA cations equivalent to 0.2–3.0 times the cation exchange capacity (CEC) were converted to HDTMA-exchanged smectites with various d-spacings. Study of HDTMA-smectites by HRTEM suggests that the HDTMA adsorption results in interlayer expansion with various d-spacings and irregular wavy layer structures. We believe that HDTMA loading beyond the CEC of smectite affects the structure of clay by the additional adsorption of HDTMA-Br− via hydrophobic bonding. Surfactant orientation probably depends on the quantity of surfactant in the interlayer. Our TEM study shows that the structure of the adsorbed HDTMA layer in the interlayers of smectite depends on the charge distribution and chemical composition of smectite.

In recent years KAlSiO4 polymorphs have become minerals of interest from an industrial point of view; they have various applications in technological and medical fields. The costs of synthesis processes are often significant and so, in the present study, an attempt was made to develop a new synthesis protocol using a widely available and inexpensive, natural starting material. The KAlSiO4 polymorphs synthesized here were kalsilite and KAlSiO4-01 — 01 refers to the high-temperature polymorph of KAlSiO4 (Cook et al., 1997; Gregorkiewitz et al., 2008; Kremenovic et al., 2013). KAlSiO4 polymorphs were synthesized using kaolin; the effects of time and temperature on the synthesis process were investigated. A solid-state synthesis protocol was developed which required the mixing of the calcined kaolin with K2CO3 in stoichiometric proportions at temperatures of 700 and 800°C at atmospheric pressure. Crystallization of kalsilite at 700°C was demonstrated while that of KAlSiO4-01 was revealed at 800°C. Synthetic kaliophilite H2 was found in both of the experiments as a metastable phase. The products of synthesis were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma optical emission spectrometry (ICP-OES), infrared spectroscopy (IR), and 29Si magic-angle spinning solid-state nuclear magnetic resonance spectroscopy (29Si MAS NMR). Calculation of cell parameters (through Rietveld refinement) and the density and specific surface area of the phases synthesized was also achieved. The amount of amorphous phase in the synthesis powders was estimated by means of quantitative phase analysis using the combined Rietveld and reference intensity ratio methods. In particular, the results of the spectroscopic, chemical, and morphological characterizations are in agreement with the data available for these minerals in the literature, thus confirming the effectiveness of the experimental protocol. The quantitative phase analysis (QPA) also indicated the high purity of the powders synthesized, thus allowing for industrial applications.

A modified procedure for bentonite purification and a new method for the quantitative characterization of bentonite using smectite content are reported. Bentonite found in a drill core of Tsunagi Mine, Niigata, Japan was evaluated by the new method to demonstrate the substantial increase in smectite content from 40% in the original bentonite to 75% after purification using a new procedure. Powder samples were prepared by putting blocks of bentonite into acetone to remove water without mechanical crushing. The powdered, acetone-dried bentonite was purified by a dispersion-sedimentation method in water after cation exchange of the interlayer Ca2+ ion with Na+ ion by the reaction of raw bentonite with aqueous NaCl. The purification was evaluated using X-ray diffraction and thermogravimetric analyses (TG). The raw bentonite contained feldspar, quartz, and cristobalite, and feldspar and quartz were removed by the new purification procedure. The purification was evaluated quantitatively by comparing the TG data before and after the purification. The purified bentonite swelled in water to give a stable aqueous suspension and 3 g of purified bentonite dispersed in 60 mL of water was stable for several days. The replacement of interlayer sodium with dibehenyldimethylammonium gave an organophilic clay, which swelled in toluene. The bentonite has potential practical uses as a purified bentonite and an organophilic bentonite.

The conventional cauliflower-like shape of magadiite imposes serious limitations on its applications in adsorption, catalysis, ion exchange, etc. To overcome this problem, a method to prepare it with plate-like structures was developed. This novel approach is based on an interface-controlled heterogeneous nucleation process. Zirconia grinding balls with diameters of 2.0 mm were dispersed in the starting solution to provide solid-liquid interfaces. Then the starting solution with a SiO2:NaOH:H2O molar ratio of 9:2:75 was subjected to hydrothermal treatment at 433 K for 96 h. The presence of the solid-liquid interface improved the crystallization yield and controlled the morphology and specific surface area of the crystals. With the zirconia balls, the yield and sizes of the plate-like magadiite were 52 wt.% and 1–3 μm, respectively. In the absence of zirconia balls, the yield was smaller (45 wt.%) and magadiite shaped like cauliflower was formed. The plate-like magadiite had a specific surface area of 66 m2 g−1 and a pore-size distribution between 4 and 5 nm, compared with a surface area of 28 m2 g−1 for the cauliflower-like magadiite. In addition, the plate-like magadiite was a more effective ion exchanger than the cauliflower-like magadiite with a cation exchange capacity of 64.5 mmol/100 g (compared to 53.8 mmol/100 g for the cauliflower-like form) and it had a faster sorption rate for calcium ions.

The configuration of hydroxyl groups around the octahedral cations of 2:1 phyllosilicate minerals has long been an important question in clay science. In the present study, 27Al multiple quantum (MQ) magic angle spinning nuclear magnetic resonance (MAS NMR) was applied to the local structural analysis of octahedral Al positions in a purified Na-montmorillonite. Three octahedral Al sites ([6]Ala, [6]Alb, and [6]Alc) are distinguished by 27Al 5QMAS NMR, whereas these sites are not differentiated by 27Al MAS and 3QMAS NMR. The isotropic chemical shift (δcs) and the quadrupolar product (PQ) were estimated to be 5.8 ppm and 2.6 MHz for [6]Ala, 6.2 ppm and 3.0 MHz for [6]Alb, and 6.7 ppm and 3.7 MHz for [6]Alc, respectively. The three Al sites originated from geometric isomers with cis and trans structures, which have mutually different configurations of the OH groups around the central Al3+ ions. From the view point of symmetry for the OH groups, [6]Ala and [6]Alb in the upfield region were assigned to cis sites, and [6]Alc in the downfield region was assigned to a trans site. The occurrence of multiple Al sites implies that Na-montmorillonite used in the present study has cis-vacant structure in the octahedral sheet. This is a reasonable insight, supported by the chemical composition and the differential thermal analysis data of the Na-montmorillonite.

Palygorskite and sepiolite are fibrous clays that occur mostly in agricultural soils of arid regions. Although many investigations have examined the environmental conditions for the formation and stability of these clays, information on the transformation of these clays in the root zone (or rhizosphere) of agricultural crops is limited. In this study, changes in palygorskite and sepiolite within the rhizosphere of selected agricultural crops were determined and the ability of plants to extract Mg from these minerals compared. Alfalfa, barley, and canola were cultivated in pots under controlled conditions in a growth chamber using growth media that consisted of a mixture of Ottawa sand and clay-sized Florida palygorskite (PFl-1) or Spanish sepiolite (SepSp-1). After 100 days of cultivation, the biomass of plant roots and shoots were determined and Mg uptake measured by inductively coupled plasma analysis of the plant biomass after microwave oven digestion. The clay fraction in each pot was separated from the sand and analyzed using X-ray diffraction (XRD) and examined using transmission electron microscopy (TEM). The XRD reflection at 0.718 nm clearly indicated kaolinite in the rhizosphere after growth of the three crops. Furthermore, hexagonal kaolinite particles were observed, using TEM, and the amount of Mg extracted by the three crops was significantly greater for sepiolite than for palygorskite. Palygorskite and sepiolite kaolinization in the rhizosphere was apparently due: (1) to high acidity in the rhizosphere caused by root activity and organic matter decomposition; and (2) to fibrous clay destabilization caused by Mg uptake by plants. This study shows that kaolinite in agricultural soils of arid and semi-arid regions might be partly due to neoformation after fibrous clay dissolution and not entirely inherited from parent materials, as has been suggested in earlier literature.

An experimental program was conducted to investigate the water-vapor sorption characteristics of smectite and kaolinite mixtures. End-member smectite and kaolinite were slurry-mixed together at mass-controlled ratios corresponding to 0%, 20%, 50%, 70%, 80%, 90% and 100% smectite. Vapor desorption isotherms for the mixtures were measured at 24°C for relative humidity (RH) ranging from ∼95% to 0%.

Results show that the amount of water adsorbed by the clay mixtures at a given RH increases systematically with increasing smectite content. Derivative analysis of the sorption isotherms shows evidence of transitions between the two-, one- and zero-layer hydrate-states for the smectite-rich mixtures. The transitions become less apparent as the smectite content decreases. Monolayer coverage, specific surface area, and heat of adsorption were estimated from the isotherms using BET theory. It is shown that monolayer coverage and specific surface for the clay mixtures can be reasonably approximated by weighted averaging of the end-member clay properties. General methodologies are presented for predicting the sorption behavior (i.e. soil-water characteristics) and effective specific surface area from measurements of the end-member sorption isotherms.

The phosphate adsorption properties of three clay samples, with kaolinite as the dominant mineral, from different deposits in the Ivory Coast have been investigated. The clays contain varying amounts of crystalline Fe oxides and kaolinite with structural Fe. All measurements were made in dilute suspension under controlled conditions of temperature, pH, ionic strength and saturating cation. Data have been fitted to Langmuir adsorption isotherms. Both P adsorption and surface area measurements have been made on samples before and after chemical removal of Fe oxides. The samples have large P adsorption capacities, which are not entirely explained by their large specific surface areas. The presence of Fe oxides makes a strong contribution to the surface area and enhances the adsorption capacities. There is little evidence that structural Fe makes a strong contribution to the enhanced P adsorption capacity.

Sets of replicate hydraulic conductivity tests were conducted using 100 mM KCl and 20 and 40 mM CaCl2 solutions to evaluate how changes in hydraulic conductivity are related to changes in the exchange complex and physical properties (water content and free swell) of prehydrated and non-prehydrated bentonite used for geosynthetic clay liners (GCLs). Essentially no change in hydraulic conductivity and water content (or void ratio) occurred during tests with the 100 mM KCl solution even though K+ was replacing Na+ on the exchange complex. In contrast, for the CaCl2 solutions (20 mM and 40 mM), the hydraulic conductivity increased and the free swell and water content decreased as exchange of Ca2+ for Na+ occurred. Faster changes in hydraulic conductivity and the exchange complex occurred in the tests with the 40 mM CaCl2 solution and the non-prehydrated bentonite (i.e. the hydraulic conductivity changed more rapidly when exchange occurred more rapidly). Even though exchange of Ca2+ for Na+ was essentially complete at the end of testing, the hydraulic conductivity obtained with the 20 mM CaCl2 solution was less and the water content greater than obtained with the 40 mM CaCl2 solution (2.6 × 10−8 cm/s vs. 6.7 × 10−8 cm/s, 122% vs. 111%, and 3.2 vs. 2.9). Similarly, the prehydrated bentonite had lower hydraulic conductivity (1.9 × 10−8 cm/s vs. 6.7 × 10−8 cm/s) and greater water content (167% vs. 111%) than the non-prehydrated bentonite at the end of testing, even though Ca-for-Na exchange was essentially complete.

Humic acid (HA)-clay complexes are well known for their contribution to soil structure and environmental processes. Despite extensive research, the mechanisms governing HA adsorption are yet to be resolved. A systematic study was conducted to characterize the adsorption of a soil-derived HA to seven clay minerals. Clay surfaces affected HA adsorption directly due to structural differences and indirectly by altering solution pH. The following order of HA removal was obtained for the clay minerals at their natural pH: illite ≫ palygorskite > kaolinite > sepiolite > montmorillonite = hectorite ≫ talc. Removal of HA (precipitation and adsorption) by kaolinite and illite was attributed to the low pH they induce, resulting in protonation of the clay and HA surfaces. In spite of the low pH, the zeta potential for HA remained negative, which promoted HA adsorption to the protonated clay surfaces by ligand exchange. Ionic strength did not affect HA adsorption to clay minerals with low zeta potentials, indicating that charge screening is not a major mechanism of HA adsorption for these minerals, and supporting the suggestion that ligand exchange is the main adsorption mechanism to pH-dependent sites. The increase in ionic strength did, however, promote HA adsorption to clay minerals with high zeta potentials. At pH 8–9 the order of HA affinity for clay minerals was: palygorskite >>sepiolite > montmorillonite = hectorite > kaolinite > illite > talc, emphasizing strong HA interactions with the fibrous clays. This strong affinity was attributed to their large surface areas and to strong interactions with OH groups on these clay surfaces. Results indicated that HA did not enter the intracrystalline channels of the fibrous clays but suggested that their macro-fiber structure facilitates HA adsorption. The sorption of HA to kaolinite further increased in the presence of Cu2+, and the sorption of Cu2+ increased in the presence of HA, due to a number of synergistic effects. This study emphasizes the diverse effects of clay structure and solution chemistry on HA adsorption.

Field and experimental studies were performed to understand the formation conditions of the Nettetal zeolite deposit, Laach volcanic area, Germany. This deposit shows pronounced small- (cm) and large-scale (tens of meters) variations of zeolitization, despite the same phonolitic precursor glass throughout the occurrence. Zeolitization of the pyroclastic ash flow is restricted to three distinct layers that are 0.15 to 10 m thick and separated by fresh ash. The glassy matrix is altered to chabazite, phillipsite, analcime and K-feldspar in various combinations, whereas the pumice clasts are altered predominantly to chabazite. Mass changes during zeolite formation appear to be small, and Ca enrichment in chabazite and phillipsite may have occurred after their formation by cation exchange.

The zeolites and zeolite assemblages observed in the Nettetal deposit were experimentally reproduced by reacting the phonolitic glass at 100–200°C with distilled water and 0.01 M alkaline solutions as well as with varying solid/liquid ratios and grain-sizes. Chabazite and phillipsite represented metastable transition phases with respect to analcime and K-feldspar. A high solid/liquid ratio accelerated the conversion of glass to zeolites.

None of the classic models of zeolite formation is fully applicable to the Nettetal deposit. The most probable environment for zeolitization in this deposit is the stagnant fringe water zone immediately above the groundwater table. In this zone, representing a relatively closed system, favorable solution compositions for zeolite formation could have been developed rather quickly by glass-water interaction, which is not possible within the more thoroughly flushed deeper parts of the groundwater system. The three distinct zeolite layers are probably the result of temporarily changing groundwater levels.

Diagenetic illite growth in porous sandstones leads to significant modifications of the initial pore system which result in tight reservoirs. Understanding and quantifying these changes provides insight into the porosity-permeability history of the reservoir and improves predictions on petrophysical behavior. To characterize the various stages of diagenetic alteration, a focused ion beam – scanning electron microscopy (FIB-SEM) study was undertaken on aeolian sandstones from the Bebertal outcrop of the Parchim Formation (Early Permian Upper Rotliegend group). Based on 3D microscopic reconstructions, three different textural types of illite crystals occur, common to many tight Rotliegend sandstones, namely (1) feldspar grain alterations and associated illite meshworks, (2) tangential grain coats, and (3) pore-filling laths and fibers. Reaction textures, pore structure quantifications, and numerical simulations of fluid transport have revealed that different generations of nano-porosity are connected to the diagenetic alteration of feldspars and the authigenic growth of pore-filling illites. The latter leads to the formation of microstructures that range from authigenic compact tangential grain coatings to highly porous, pore-filling structures. K-feldspar replacement and initial grain coatings of illite are composed primarily of disordered 1Md illite whereas the epitaxially grown illite lath- and fiber-shaped crystals occurring as pore-filling structures are of the trans-vacant 1Mtv polytype. Although all analyzed 3D structures offer connected pathways, the largest reduction in sandstone permeability occurred during the initial formation of the tangential illite coatings that sealed altered feldspars and the subsequent growth of pore-filling laths and fibrous illites. Analyses of both illite pore-size and crystallite-size distributions indicate that crystal growth occurred by a continuous nucleation and growth mechanism probably controlled by the multiple influx of potassium-rich fluids during late Triassic and Jurassic times. The detailed insight into the textural varieties of illite crystal growth and its calculated permeabilities provides important constraints for understanding the complexities of fluid-flow in tight reservoir sandstones.