Although fluorescence detection is a sensitive method in the field of pollutant analysis, its application is restricted due to the fluorescence shown by organic material being quenched after aggregation and to low photo-thermal stability. To address these issues, a novel mineral/dye composite material was prepared by intercalating a fluorescence molecule, Rhodamine (R6G), into the interlayer space of montmorillonite (Mnt). This composite material greatly enhanced the light stability and efficiency of R6G. After enhancement, the fluorescence lifetime of R6G-Mnt was eight times longer than originally and the luminous intensity was 20 times greater. Chromium at the mmol/L (mM) level can be detected by the naked eye when its enhanced fluorescent property is fabricated into a solid test paper, even though a fluorescence spectrophotometer should be used for detection at the 0.01 μmol/L level in the sensing range 0.01 μmol/L to 100 mmol/L. These results can provide new avenues as well as a theoretical and experimental foundation for the development of novel supramolecular luminescent material.

A common design of a high-level radioactive waste (HLW) disposal system consists of the waste canisters emplaced in tunnels or shafts, with the space between the heat-emitting canisters and the surrounding rock filled with a bentonite-based material. Understanding the behavior of this barrier, in particular the effect of prolonged heating on its properties, is important to assess the barrier’s long-term performance. The objective of the present study was to add to this understanding and to supply experimental data about the state of bentonite hydrated and heated for a long period of time. To that end, a 50 cm long column of Wyoming-type bentonite pellets was heated at its base at 140 °C (simulating the waste canister) while a synthetic sodium-chloride-rich groundwater including sulfate, calcium, and magnesium was supplied through its upper surface for almost 10 y. At the end of the experiment the upper half of the column was saturated, but in the lower half the water content decreased sharply toward the heater, where it was close to 0%. No relevant mineralogical changes occurred, and the main component of the bentonite continued to be a predominantly sodium montmorillonite with no structural changes with respect to the initial one. In the area where the temperatures were >60°C and the material very dry, however, the smectite was not able to completely develop the 1-layer hydrate after 48 h of stabilization at RH 55%, although its expandability was fully recovered when the smectite was hydrated with liquid water. The ions solubilized as a result of the water-content increase were transported toward the heater and concentrated in two distinct areas: sodium and calcium chlorides closer to the heater than calcium and sodium sulfates. At the heater contact, the bentonite microstructure was of dense packets with carbon and Na-S-coated cavities. Precipitation of calcite and calcium sulfates and possibly dissolution of silica minerals also took place close to the heater.

A viacomotrio study of dilute montnioritlonite dispersions, using lor tho most part dilution-typo capillary viscometers supplemented by a falling-head capillary viscometer, has involved a determination of the concentration dependence of viscosity of such dispersions in both distilled and electrolyte-containing water. The resulta of the study have been interpreted in terms of a theory of incremental viscosity, and of the Solmlz—Rlaschke (1941) equation. Use of this equation yields good extrapolations to zero concentration for the determination of limiting viscosity number, and permits calculation of “interaction indices” which are considered, for reasons discussed in detail, to be a measure of paitiele-particle interaction. These indices are related to the cationie heat of hydration of the electrolyte used, and relationship is demonstrated between the yield stress of a 3 percent montmorillonite—eleetrolyte—water system and such interaction indices. The recent work of Paekter (1956, 1957) is discussed, and the relation of the results of this investigation to the data of van Olphen (1956, p. 204) is noted.

Chromium-bearing members of the montmorillonite group have been reported heretofore only for Russian localities, where they have been related genetically to serpentines. A green mineral which occurs in high-angle fissures in the Morrison formation (Upper Jurassic) near Thompsons, Utah, contains about 2 percent Cr2O3. Data were obtained by optical and electron microscopy, x-ray powder diffraction, and gravimetric and spectroscopic chemical methods. The ultimate source of the chromium remains an unresolved geochemical question, as do the sources of vanadium and uranium in the Morrison sandstone.

Precise information on the location of charge in clay minerals and their charge density in smectite-dominant soils is rare. The present study was undertaken with three benchmark Vertisols to establish the relationship between the clay cation exchange capacity (CEC), charge density, as well as the location of charge in smectitic soil clay minerals and their relationship with potassium (K) fixation and release. Potassium fractions and their threshold levels in the Vertisols were determined by standard methods. Soils were segregated into silt, total clay and fine clay fractions for X-ray diffraction analysis and fine clay fractions were used to determine the CEC using standard methods. The Hofmann-Klemen effect (HK) and modified Greene-Kelly test was done with the fine clay to determine the CEC of the tetrahedral sheet. Subsequently, the CEC of the octahedral sheet was calculated as the difference between total CEC and the tetrahedral CEC. The results showed that ~60–64% of the total CEC is attributed to the tetrahedral layers. The tetrahedral CEC that is proportional to the tetrahedral charge density was significant and negatively correlated with K release threshold values and all fractions of K. The tetrahedral CEC contributed more toward the K fixation and release than the octahedral CEC. The study shows that the dominant presence of high-charge smectites in the fine clay fractions of these Vertisols contributed to the tetrahedral CEC and consequently to the charge density of these soils, which implied a tendency to fix K easily and release it with greater difficulty compared to soils with low-charge smectites.

The harm caused by mine tailings has become increasingly problematic in recent years, so efforts are needed to dispose of or reutilize them in environmentally friendly ways. The objective of the present study was to find out if the hydration properties of muscovite contained in mine tailings are suitable for it to be used as a pozzolan in cement, after undergoing mechanical activation. Aqueous suspensions of mechanically activated muscovite were blended with 10, 20, or 30 wt.% calcium oxide and then allowed to harden. The hardened paste samples were analyzed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) techniques. The results revealed that the mechanically activated muscovite exhibited pozzolanic reaction activity in the alkaline environment provided by calcium oxide, and the activated muscovite possessed a capacity to react with calcium hydroxide to form hydration products. The calcium oxide content affected significantly the quantities and kinds of hydration products, non-evaporable water content, and the compressive strength development of the paste samples. The hydration products of the 10% calcium oxide-activated, mechanically activated muscovite pastes were Al-containing hydrated calcium silicate (C-A-S-H) gel, stratlingite, and, upon addition of 20% and 30% calcium oxide, Ca-Al hydrotalcite-like (Ht) phases. The present study was helpful in evaluating the hydration properties of the mechanically activated muscovite and also provided a research basis for evaluating the hydration properties of mine tailings containing muscovite after mechanical activation. The results provided a theoretical basis for muscovite-containing mine tailings to be used as a cement additive, and was conducive to the large-scale utilization of mine tailings.

Supported silver nanoparticles (Ag NPs) have been used extensively as antibacterial agents in biomedicine, biotechnology, and environmental remediation. However, a facile and scalable method for preparing Ag NPs dispersed homogeneously on supports remains a challenge. In this study, a novel molten salt method was developed successfully to synthesize the supported, homogeneously dispersed Ag NPs on palygorskite. Abundant pores and ample surface hydroxyl groups of palygorskite served as anchoring sites, preventing the rapid growth, aggregation, and sintering of Ag NPs. Typically, palygorskite was mixed with AgNO3 (as a precursor) and NaNO3 (as a dispersant), and then the mixture was heated slowly. During the heating process, the AgNO3 decomposed gradually into Ag NPs and the molten NaNO3 with a high concentration of ions dispersed the newly formed Ag NPs. The Ag NPs were dispersed homogeneously on the palygorskite and had very small particle sizes (~5.8 nm) even for a significant loading amount (~9 wt.%). As antibacterial agents, the Ag/palygorskite nanocomposites showed enhanced antibacterial activity, compared with those synthesized without the introduction of molten NaNO3. In addition, the key effect of the surface hydroxyl groups of palygorskite on the characteristics of the loaded Ag and the corresponding antibacterial activity were also elucidated. As such, the present work provided a novel and facile strategy for the synthesis, without a chemical reductant or surfactant, of supported, highly dispersed Ag NPs on clay minerals and this could have potential in the scalable production and practical application of Ag-based antibacterial materials.

Examination of the silt and clay fractions of two northern Wisconsin soils, Omega loamy sand of the Brown Podzolic group and Ahmeek loam of the Brown Forest group, revealed considerable quantities of interstratified layer silicates. The two soils contained montmorin, vermiculite, chlorite, and illite both as discrete and interstratified components. Regularly alternating montmorin-illite structures, which registered a 28 Å first order diffraction peak, and vermiculite-illite structures, which yielded a 24 Å first order peak, were observed in the fine silt fractions of the Ahmeek loam A3 and B22 horizons, respectively. Weak diffraction peaks in general and lack of binary mixture average spacings was suggestive of ternary or quarternary interstratification of illite, chlorite, vermiculite, and montmorin in the medium and fine clay fractions of the Ahmeek loam horizons. Randomly interstratified vermiculite-chlorite and vermiculite-montmorin, as revealed by comparative basal diffraction peaks before and after heating potassium saturated samples, were evidenced in the fine silt and clay fractions of the Omega profile.

Mixed layer components in the Omega and Ahmeek soils originated from illite and chlorite in the? horizons with a progressive increase in proportions of first vermiculite and finally montmorin with proximity to the soil surface. The observed weathering transitions within the mixed layer structures illustrates the effects of accelerated leaching which has taken place in these coarse textured soil profiles, even though these soils are relatively young (late Pleistocene).

The i.r. spectrum of K depleted biotites (structural OH stretching range) has been studied with monocrystals equilibrated at various water contents. Prior to spectroscopic measurements, the samples were submitted to deuteration treatments which displaced the hydration water spectrum to the OD region and made it possible to observe the behaviour of the structural hydroxyls without interference from hydration water.

In these conditions it was shown that the high frequency absorption of K depleted biotites (N + I bands) is the sum of two absorptions: the first corresponds to the initial mica spectrum, the second corresponds to the hydrated phase in which component bands (according to Vedder and Wilkins) are shifted by 36 cm-1 towards low frequencies.

Simultaneously it was shown that low frequency bands (V bands) decreased in intensity. This unexpected observation has been explained by a partial deuteration of structural OH, which takes place during the preliminary contacts of the samples with D2O vapour.

The statistical techniques of multiple regression analysis have been used to obtain more reliable formulae relating the cell dimensions especially the b-axis) of layer-lattice silicates to their composition or structural formulae. This allowed the significance of each coefficient to be expressed precisely and so provided rigorous tests for certain structural concepts about the different factors affecting cell dimensions. More recently an explicit theory has been developed about the various forces controlling the layer-lattice silicate structures which (a) removes some anomalies, (b) explains many variations in accurate bond lengths and angles, and (c) has several interesting structural implications for properties such as polymorphism, composition limits, crystal morphology, and stability under weathering. This paper summarizes work now being published in extenso elsewhere.

The structural significance of micas with Na-K intermediate composition, and their chemical and structural evolution at increasing metamorphic grade have been investigated in Triassic rocks from the transition between the Maláguide and Alpujárride complexes (Internal zones of the Betic Cordillera, Spain). Micas were studied by X-ray diffraction (XRD) and by scanning and transmission electron microscopy (SEM/TEM). Three samples, belonging to the late diagenesis and to the low and medium anchizone, were selected for this study. Na-bearing mica appears as submicroscopic packets intergrown in parallel with K-mica, becoming more compositionally uniform with increasing grade. The diagenetic sample contains illite, minor paragonite, and two main populations of intermediate Na-K micas, with average compositions Ms60Prg40 and Ms35Prg65, respectively, where Ms represents muscovite and Prg, paragonite. The lattice-fringe images of mica packets with intermediate compositions suggest the presence of random mixed-layered paragonite-muscovite. Under low anchizonal conditions the amount of discrete paragonite increases and the Na-K intermediate mica has a mean composition of Ms40Prg60. The TEM images suggest that the packets with intermediate composition are solid solutions of paragonite and illite. Micas with Na-K intermediate composition are lacking in the sample with the highest metamorphic grade. In this sample, paragonite and muscovite coexist with mica, with composition intermediate between paragonite and margarite. The lattice-fringe images of these Na-Ca-bearing packets suggest that they consist of irregularly shaped domains enriched either in Na or in Ca.

Our data indicate that Na+K-bearing micas have several origins: detrital stacks of K- and Na-bearing micas coexist with authigenic phases, formed from dickite in the diagenetic, coarse-grained samples, and perhaps from smectite-bearing mixed-layers or detrital illite, in the fine-grained rocks. The changes observed at increasing metamorphic grade can be related to the influence of the lithology, the metamorphic grade, and the different geological settings. Intermediate Na-Ca mica appears to have grown from paragonite, with calcite as the source of Ca.

The adsorption of [M(bpy)3]2+ ions (M = Ru or Os) by clay films immersed in pure water and in electrolyte solutions was investigated by electrochemical quartz crystal microbalance (EQCM), UV-visible spectroscopy and powder X-ray diffraction. In water, the adsorption of the cations resulted in a decrease in the mass of the films. This decrease in mass is attributed to the expulsion of some 50 water molecules from the clay interlayer spaces for each cation adsorbed. Water is lost to make room for the large metal complex cations in the interlayer spaces, and because of decreases in the volume of the interlayer spaces during adsorption of the cations. In 0.05 M NaCl or 0.05 M Na2SO4, UV-visible measurements show a rapid initial adsorption of the cations by ion exchange, followed by a slower additional adsorption of the cations above the clay’s CEC, presumably as ion pairs with the electrolyte counter ions. The EQCM show initial reductions in the mass of the films that were two to three times larger in pure water. These initial mass decreases were followed by smaller mass ‘re-increases’ at longer times that were not observed in water. The larger initial mass losses are attributed to the loss of more water from the clay interlayer spaces. In 0.5 M Na2SO4 or 1.0 M NaCl, adsorption of the cations never exceeded the clay’s CEC. The initial decreases in mass upon addition of the cations all but disappeared, leaving only the smaller positive mass changes at longer times.

An unusual halloysite deposit occurs on the west side of the Lake Mountains in Utah County, Utah. A field and laboratory study was made of this Fox deposit to determine the paragenesis of the clay minerals, especially halloysite. Successive lenses of unaltered tuff, partially altered tuff, clay and travertine beds, indicate that the clays have resulted from alteration of siliceous volcanic tuffs in a Tertiary (?) calcareous hot spring environment. Clay minerals identified were montmorillonite, kaolinite, halloysite·4H2O (endellite) and halloysite·2H20. Montmorillonite, which developed in a zone of less intensive silica leaching farthest from the hot spring vents, is the predominant clay mineral. Irregularly distributed pockets of halloysite and kaolinite developed nearest the hot spring vents in a high-calcium environment. In the clay, or associated with it, are calcite as travertine, quartz as rounded carbonate-corroded grains, feldspar, tridy- mite, biotite and glass.

Experiments that approximate the chemical environment prevalent in the halloysite alteration zone were conducted on phase relations in part of the system lime—alumina- silica—water. Results suggest the formation of halloysite·4H2O in this kinetic system from intermediate calcium aluminate or calcium silicate hydrates with halloysite-type structures, or both.