Analyses of samples of the Havensville Shale, collected from six localities in Kansas and northern Oklahoma, showed that the distribution of clay minerals and chemical variations in the clay minerals were related to changes in the sedimentary facies. The major clay minerals assemblages were: (1) illite, mixed-layer illite—montmorillonite, and regularly interstratified chlorite-vermiculite in the shaly facies of northern and central Kansas, (2) montmorillonite, illite and mixed-layer illite-montmorillonite in the calcareous shale and algal limestone facies of southern Kansas, and (3) kaolinite, illite and mixed-layer illite—montmorillonite in the sandy facies of northern Oklahoma. Differential settling and transportation of clay detritus were the major factors in the pattern of distribution of the clay minerals. Regional differences were noted in the abundance of 2m illite polymorphs, the K/Rb ratio and the illite 001/002 intensity ratio. Some structural variations and chemical differences among the clay minerals were consequences of modifications during deposition in different environments and diagenesis.

The flavonoid naringin is the main source of the undesirable bitter taste in some citrus juices. In commercial debittering processes, the naringin is adsorbed on non-ionic polymeric resins. Organo-clays (OCs), which have been used as sorbents for organic pollutants, could also have affinity for the naringin molecule, and thus potentially could serve as a debittering agent. The objective of the present study was to characterize the sorption capacity of a prepared OC to evaluate its ability to remove naringin from aqueous solutions, investigating the effect of adsorbent dose, initial concentration of naringin, temperature, contact time, and pH. The OC was prepared by the intercalation of cationic surfactant hexadecyltrimethylammonium bromide in a Mexican bentonite. The host clay and the OC were characterized by X-ray diffraction, Fourier-transform infrared, and nitrogen gas adsorption. The OC showed a surface area of 9.3 m2 g-1, 11.35 nm average pore diameter, and a basal spacing, d001, of 2.01 nm. The adsorbent removed naringin at the rate of 60-72% at 25°C and pH 3. The sorption capacity increased with pH and temperature. Experimental data were well fitted by both Langmuir and Freundlich adsorption models. Most of the sorption took place during the first 10 min and the equilibrium time was reached within 720 min. The rate of sorption was adjusted to pseudo second-order kinetics.

Hydrous phyllosilicate minerals exhibit many variations in unit-cell shape and symmetry, distortion due to cation ordering, polytypic repeats along Z, and lateral modulations that can affect the ease of indexing of X-ray powder diffraction patterns. In indexing the patterns of monoclinic and triclinic hydrous phyllosilicates it is important that the indices of all overlapping but nonequivalent lines be listed and used in the indexing program, with weights assigned according to their multiplicities. Deviations from orthogonal unit-cell geometry show up by a broadening or a splitting of nearly superimposed lines, as occurs also if the observed ß angle differs from that produced by a layer shift of ideal magnitude (e.g., a/3). Observed powder intensities should be correlated with those expected from the structure, and an index should not be assigned solely on the basis of the calculated d-value that is closest to that observed. Assigned indices should not violate space group extinctions. Multilayer structures show up in reflections of type k ≠ 3n for C-centered unit cells, not in 00/reflections.

Fourier syntheses have been used to establish the arrangement of organic molecules in the interlamellar regions of a 16.10 Å phase of ornithine-vermiculite and a 16.92 Å phase of 6-aminohexanoic acid-vermiculite. The organic cations form two layers parallel to the silicate surfaces in ornithine-vermiculite and in 6-aminohexanoic acid-vermiculite the organic cations form ascending and descending “stairs” from the silicate sheets.

Ornithine-vermiculite forms a true single layer polytype but by contrast 6-aminohexanoic acid-vermiculite is two-layered and has a true c axis of 34.09 Å. Since a two layered vermiculite was used as a starting material to prepare the organic complexes, exchangeable organic cations affect the stacking sequence of the silicate sheets.

Isomorphous substitutions of Mg and Fe for Al generally appear in the octahedral sheets of montmorillonite, whereas they are infrequent in kaolinite. Therefore, the release of Mg and Fe from the octahedral sheets probably happens during the transformation of montmorillonite into kaolinite, which could affect the migration of Mg and Fe from clay minerals into surrounding environments. The objective of the current study was to investigate the relationship between Mg and Fe release during the transformation of montmorillonite into kaolinite. The results showed that the d060 value of clay minerals decreased slightly, and the intensities of both the AlMg–OH and AlFe–OH bending vibrations also decreased gradually. In addition, the (Mg+Fe)/Al (major octahedral ions) atomic ratio of kaolinite was lower than that of montmorillonite, especially in identical hydrothermal products. These results indicated that Mg and Fe ions were released progressively from the octahedral sheets during the transformation of montmorillonite into kaolinite. Moreover, the changed relative concentrations of Mg and Fe ions in the supernatant solutions after hydrothermal reactions suggested a random distribution of Mg and/or Fe in the octahedral sheets of the montmorillonite. These results improve understanding of the release relationship between Mg and Fe during clay mineral evolution and of the distribution of these two ions in the octahedral sheets, as well as the chemical composition of clay minerals as an indicator of geological environments.

Previous work has shown that dimethyldioctadecyl ammonium montmorillonite is a very effective adsorbent in the gas phase for the separation of aromatic compounds from the paraffins, and for the separation of the disubstituted isomers of benzene. The present paper describes an investigation into this phenomenon.

For this purpose a method of calculating entropies of adsorption from gas chromatographic data was derived, and results are given for relevant organic vapours adsorbed on the quaternary ammonium derivative, and on octadecyl ammonium montmorillonite. These results throw considerable light on the basis of the selectivity shown by the quaternary ammonium derivative, and a possible explanation of the mechanism is given.

The effect of the method of preparation on the gas phase activity of this adsorbent is very large, and experimental work on the correlation of this with the structure of the derivative is described.

A Solution containing fluoride (0.4 n NH4F, 0.1 n HCl, n NH4Cl), permits the concentration of dioctahedral mica and dioctahedral vermiculite in mixed clay systems. Allophane, halloysite, kaolinite, and in particular, Mg-rich montmorillonite, biotite, and vermiculite of clay size, are destroyed in 24–48 hr at room temperature. A salt-free, NH4-saturated sample, weighing 80 mg, is shaken in 80 ml of the fluoride solution. The residue is washed with water and X-ray diffraction patterns made.

The method has use in characterizing some of the 2:1 layer silicates in clays. Anatase, if present, is also concentrated and is more positively identified by X-ray diffraction.

Hydrothermal solutions related to magmatic intrusions that occurred during the Oligo-Miocene resulted in advanced multi-stage alterations and, to varying degrees, kaolinization over a wide area of the Biga Peninsula. The most important formations in these kaolin deposits occurred along the NE–SW-trending Çan-Etili-Bayramiç fault zone. The Bahadırlı, Duman, and Çaltıkara quarries are well preserved kaolin deposits throughout these fault zones located within the Çan Volcanics. Mineralogical, geochemical, and isotopic analyses were performed to identify the environments of formation of kaolins and the origin of the hydrothermal solution that led to the formation of these deposits.

The mineralogical assemblages of each of the quarries differ from each other. The Bahadırlı kaolin quarry comprises kaolinite + alunite ± quartz ± smectite ± plagioclase ± K-feldspar. The Çaltıkara kaolin deposits consist of kaolinite + quartz + alunite ± iron-oxide and ore minerals. The Duman kaolin quarry was considered in two different slopes as a hanging wall block and a footwall block, and the blocks contain kaolinite + quartz + plagioclase ± smectite and kaolinite ± alunite ± smectite ± quartz ± plagioclase ± K-Feldspar ± gypsum, respectively. During petrographic investigations, it was observed that kaolinization occurred generally in K-feldspar and plagioclase phenocrysts and partially in the matrix. Mineralogical and micromorphological investigations revealed that the kaolin group includes the dioctahedral minerals kaolinite and halloysite. According to the trace element contents of the kaolinites, the Çaltıkara and Bahadırlı deposits had a hypogene origin, while the Duman deposit had a supergene origin. δ18O isotopic values of kaolinites ranged from +10.3 to +18.3‰. δ34S isotopic values ranged from –17.2 to +20.2‰ of alunite, galena, and pyrite minerals, which indicate different formation environments for the kaolin quarries. 40Ar/39Ar dating of alunite revealed that the timing of acid-sulfate alteration was compatible with the magmatic intrusions. All these data revealed the mineralogical, chemical, and isotopic differences caused by the effect of different hydrothermal processes in three kaolin deposits located on the same fault zone, close to each other and similar in age.

Selective sorption and/or fixation of cations with low hydration energies (e.g. K+, NH4+, Rb+, Cs+) by vermiculites is a well known phenomenon in soil science and it has been described by many investigators since the 1950s. Because most of the available studies deal with trioctahedral vermiculites, cation fixation in dioctahedral vermiculites is not as well understood as fixation by trioctahedral structures. The objective of the present study was to investigate the influence of NH4+ saturation on the structure of a natural dioctahedral vermiculite. Because no dioctahedral vermiculite standard reference material was available, two natural dioctahedral vermiculite-rich soil clay samples were used in the study. The clays were saturated with NH4+ using different protocols to simulate natural processes that likely take place in soils. The degree of NH4+ fixation by the dioctahedral vermiculite was evaluated using X-ray diffraction, elemental N analysis, and infrared spectroscopy. All the treatments that involved NH4+ saturation caused NH4+ fixation and irreversible collapse (i.e. contraction to ~10 Å) of at least a portion of the previously hydrated (vermiculitic) interlayers. Air drying of the NH4+-saturated samples greatly enhanced the degree of the collapse. The results indicated that the collapse of dioctahedral vermiculite leads to the formation of a NH4-illite-like phase that is likely to occur in some soils and sediments that are rich in organic matter. The formation of a NH4-illite-like phase by NHNH4+ fixation in vermiculitic interlayers needs to be taken into consideration in studies that deal with the clay mineralogy of sedimentary basins.

The present study presents a generalized procedure to accurately identify trioctahedral 1:1 layer silicates. The reciprocal space (RS) sections were obtained by the precession method by “unwarping” frames that were recorded using diffractometers with area detectors or from electron diffraction tomography (EDT) patterns. Distributions of subfamily reflections along the reciprocal lattice rows [21̄l]* / [11l]* / [1̄2l]* in (2hh̄lhex)* / (hhlhex)* / (h̄2hlhex)* RS planes were used to determine OD (Ordered — Disordered) subfamilies (Bailey’s groups A, B, C, D). The distributions along the [10l]* / [01l]* / [1̄1l]* rows in the (h0lhex)* / (0klhex)* / (h̄hlhex) RS planes allow determination of the polytypes. The use of traditional identification diagrams for the determination of OD subfamilies and polytypes was generalized in order to identify monoclinic and orthorhombic MDO (Maximum Degree of Order) polytypes. In these polytypes, the distribution of characteristic reflections along rows is different in RS sections that are perpendicular and diagonal to the symmetry plane of the polytype. The identification diagram of non-MDO polytype 6T2 is also presented. The method was applied to the identification of single crystals of cronstedtite that were synthesized during interactions of Fe metal with a natural claystone during experiments over a temperature range of 90-60°C. Conical and pyramidal crystals with a maximum size of a few micrometers were studied using electron diffraction tomography (EDT). The following polytypes were identified: 1M, 2M1, an apparently ninetuple polytype that was interpreted as triclinic 3A (group A), 1T (group C), and disordered crystals of group D. The 1M polytype was the most abundant. Some 1M crystals were twinned by reticular merohedry with a 120° rotation along the chex axis as the twin operation. The 2M1 occurred as isolated crystals as well as in mixed crystals. Intergrown 1T and 1M polytypes of the C and A group, respectively, were identified in one mixed crystal. The possible stacking sequence and the 3A polytype identification diagram was presented and discussed. Example RS sections of all polytypes were identified and demonstrated.

The radiogenic isotope systematics of clay minerals are complex because of the intimate mixture of minerals from different origins such as detrital and authigenic sources. An important aspect of dating clays is the primary sample preparation and disintegration method. In the present study, a sample of weakly deformed Opalinus claystone from the Mont Terri underground site (Switzerland) was investigated after disintegration by three different methods. The Opalinus Clay was sedimented in the late Toarcian and early Aalenian and reached maximum temperatures of ~85°C during burial in the Cretaceous. The present study reports data from a comprehensive investigation comparing the effects of disintegration by: (1) disc milling; (2) repeated freezing and thawing; and (3) high-voltage discharges. K-Ar age values of the finest clay (<0.1 µm) released by the different disintegration methods are indistinguishable, indicating that the high-voltage liberation method does not influence grains as small as 100 nm. The K-Ar age values of particle-size separates decreased with decreasing particle size. The age values of the 2–6 µm separates correspond to the Carboniferous Period, which reflects the dominance of Paleozoic detritus in that size range. The age values of the smallest separates (<0.1 µm), on average 213 ± 4 Ma, exceed the numerical age of the formation (~177−172 Ma), which show predominance of detrital grains over authigenic grains even in the finest illite. In summary, isotope geochronology data suggest that the high-voltage method can be applied reliably for disintegrating claystones.

Toxic dyes must be removed from waste water coming from the textile and paint industries. Adsorption is one possible method of removing dyes under ‘soft’ conditions, without the generation of secondary hazardous materials. The present study used the carbonate-containing layered double hydroxides (LDH), Mg-Al and Mg-Zn-Al (with a M2+/M3+ ratio of 3), as adsorbents to remove two industrial colorants, Astrazon Remazol Brilliant Blue and Direct Red, present in low concentrations in aqueous solutions. The physicochemical properties of adsorbents at the surfaces of LDH, as well as the properties of the solutions containing the dyes control how the colorants are removed. Both fresh and calcined LDH were effective in the removal experiments, with effectiveness ranging from 50 to 100%. Analysis of kinetic data demonstrated that the adsorption process fitted the pseudo-second-order model better than the pseudo-first order model, information which is useful for system design in the treatment of wastes from the textile industry. Parameters such as pH of solutions and concentration of dye in solution influenced mainly the initial adsorption rate.

For many purposes it is desirable to have a method for the determination of the cation exchange capacity of clay minerals based on principles as free from ambiguity as possible. Most of the many methods previously proposed have the drawback of entailing a great deal of work if one is to make sure that the mineral is completely saturated with the reagent in use, or that an excess of the reagent is absent. What might be called the complete chromatographic method by its very nature does not suffer from this difficulty. A known weight of clay is suspended on an appropriate inert filter aid (such as Gooch asbestos), packed into a glass tube, and the exchangeable ions eluted with a solution of cesium chloride traced with radioactive Cs 137. The effluent is collected in a series of appropriately sized samples, and the specific radioactivity of each of these determined. When the activity of the effluent has risen to that of the influent solution, one is certain that complete exchange has taken place. A simple computation gives the total cesium holdup of the column, and if the column was initially dry, the exchange capacity of the clay sample.

As a routine method, particularly when results of the highest precision are not needed, the effluent may be collected in only two samples, one large sample and finally one small sample to check for complete exchange. This procedure requires a minimum of work and attention but suffers from the disadvantage that the result depends upon the difference of the two counting rates measured and is thus subject to greater uncertainty.

These methods have been compared with the Bower-Truog method (Ind. and Eng. Chem., Anal. Ed., 12, 411 (1940)) on Chambers, Arizona, montmorillonite, a nontronite, and an attapulgite. Generally the Bower-Truog method gave more variable and somewhat lower results. Thus for the Chambers montmorillonite the Bower-Truog method gave 0.97 meq./gm.; the chromatographic method, 1.054 meq./gm.

The method has been further tested by initially saturating columns with manganous ion, determining the weight of solution held up in the column, and then eluting with traced CsCl. Effluent Mn was determined colorimetrically and the Cs in the Geiger counter. The results agreed within experimental error for the following clays of the API series: montmorillonites H19, H23, H24; illite H36; and nontronite H33b.

The physical and chemical interactions between organic amines and mineral surfaces are of considerable importance in many industrial applications. For example, the preparation of organophilic minerals often involves the adsorption of organic amines, or the ion exchange of the minerals with quaternary ammonium salts (Jordon, 1951; Miller and Faust, 1972). Chemical interactions occurring in these systems have been studied because of their relevance to an understanding of the chemical nature of the clay surface. A number of these studies have reported on the decomposition of adsorbed amines and alkylammonium-mineral complexes at elevated temperatures, usually in excess of 100°C (Chaussidon and Calvet, 1965; Weiss and Roloff, 1963; Durand, Pellet and Fripiat, 1972; Chou and McAtee, 1969). It is now well established that under these conditions the mineral may have potential strong-acidity, and these reactions have been explained in terms of acid-induced decomposition or rearrangement of the adsorbed amines or their derivatives. However, there have been few studies of the reactions of organo-mineral complexes at temperatures below 100°C, under conditions where retention of adsorbed water could be expected to moderate the mineral surface acidity.

In a study of “rana” soils of central Spain, hydroxy-interlayered 2:1 clay minerals were identified in the upper horizons and high-charge smectite in the lower horizons, with kaolinite the most abundant phyllosilicate. The high-charge smectite showed a basal spacing of 18 Å on Mg-saturation and glycerol solvation and 10 Å on K-saturation and air-drying. It is concentrated in the coarse fractions and appears to be basically a beidellite in the fine-silt fractions and a montmorillonite in the clay fractions. Pre-existing illite was probably transformed into hydroxy-interlayered 2:1 clays in the surface horizons, whereas high-charge smectite formed in the deeper horizons. These minerals, which were apparently not stable in the existing soil conditions, were the first stage in the degradation process of illite. The stable mineral in these soil profiles was kaolinite.

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.

Clay mineral associations in saprolite of two andesites from the Cascade Range of northeastern California were determined. Sesquioxidic allophane with a high CEC delta value dominates the clay fraction of the least weathered saprolite in each series (47% and 37% in hypersthene andesite and olivine andesite saprolites, respectively). With further weathering, the content of amorphous clay remains high (over 30% in all cases) but the CEC delta value of the clay drops markedly. The amorphous material in the more weathered saprolite has the properties of halloysitic allophane. Halloysite, present in all saprolites, is highest in concentration (over 30%) in the more strongly weathered members of each of the saprolite series. Formation of sesquioxidic allophane during early stages of weathering and its transformation to halloysitic allophane and halloysite during later stages of weathering are supported by X-ray diffraction, electron microscopic, DTA, elemental analysis, and CEC delta value data.

A series of experiments was set up, the purpose of which was to determine factors affecting long-term settling characteristics of some suspensions of clay-sized materials. Suspensions of approximately 8 g per 1. were prepared using Georgia kaolin, Mississippi bentonite, Wyoming bentonite, Iowa illite and finely ground quartz. In addition, 2 g and 16 g per 1. suspensions of kaolinite were prepared. All suspensions were observed for 2-week periods at constant temperatures of 19°C; kaolinite suspensions were also observed at 2°, 10°, 25° and 31°C.

After settling 3–4 days at 19°C, layering formed in all clay suspensions, and all the tops of the layers contained higher concentrations of suspensoid than bottoms. Tops and bottoms of the layers were parallel to liquid top surfaces.

At 2°C, no stratification developed in kaolinite suspensions. At 10°C, layering formed only in 2 g per 1. suspensions after 3 months of settling. At higher temperatures, layering formed after 3–4 days of undisturbed settling. Two grams per liter kaolinite suspensions formed five distinct layers; 8 g per 1., nine layers; and 16 g per 1. suspensions formed a many-layered, banded structure after approximately 2 weeks.

If layered suspensions were cooled, the layers were not disturbed. However, layering was very responsive to heating: they expanded and tilted downward away from the heat source. With prolonged heating, layering disappeared.

These experiments show that temperature and concentration markedly affect long-term settling characteristics of fine-grained suspensions. Layering forms most readily in water with relatively low viscosity and density. If such layered suspensions were formed in nature, such features as graded bedding, lamination, or varving probably would result after complete settling.

Large kaolin deposits developed by weathering on Precambrian granitic rocks have been discovered in the Caluquembe area, Huíla province, Angola. To determine accuracy of analysis and to evaluate the kaolinite grade, a full-profile Rietveld refinement by X-ray Powder Diffraction (XRPD) and Thermal Gravimetric Analysis (TGA) was used. Caluquembe kaolin is composed mainly of kaolinite (44–93 wt.%), quartz (0–23 wt.%), and feldspar (4–14 wt.%). The Aparicio-Galán-Ferrell index (AGFI), calculated by XRPD profile refinement, indicates low- and medium-defect kaolinite. Kaolinite particles show a platy habit and they stack together forming ‘booklets’ or radial aggregates; they also occur as small anhedral particles in a finer-grained mass. Muscovite-kaolinite intergrowths have also been found. Whole-rock chemical analysis included major, trace, and Rare Earth Elements (REE). Chondrite-normalized REE patterns show the same tendency for all samples, with a significant enrichment in Light Rare Earth Elements (LREE). Mineralogical and compositional features of the Caluquembe kaolin indicate that it is a suitable material for the manufacture of structural products, such as bricks, paving stones, and roofing tiles. In addition, the significant REE contents of the Caluquembe kaolin can be considered as a potential future target of mining exploration.

Intercalation of montmorillonites with a mixture of intercalates has not been studied extensively. The objective of the present investigation was to study the effects of phosphonium-based intercalate mixtures on the properties (organic loading and basal spacing) of montmorillonite. These phosphonium-intercalated montmorillonites are promising candidates as high-temperature stable nanofillers for application in clay polymer nanocomposites.

Two salts with different cationic heads and chain lengths were mixed in varying molar ratios and the mixtures were intercalated into the interlayer space of montmorillonite. Two sets were chosen based on the chain length and the cationic head-group structure of the two intercalated salts (referred to hereafter as set 1 and set 2). The resultant intercalated montmorillonite was characterized by thermogravimetric analysis, X-ray diffraction, and transmission electron microscopy. The organic loading of the intercalated montmorillonite increased with the proportion of longer carbon-chain intercalate in the mixture. The intensity of the characteristic XRD peak of each intercalate varied with the mole fraction percent of that intercalate in the solution mixture. No marked synergistic effect of the intercalate mixture on the basal spacing and organic loading properties of the intercalated montmorillonite was observed — the proportional influence of individual components was found to be more prominent.