The immobilization of antimicrobial drugs can be used to expand the application of antibacterial properties to consumer products. The purpose of this study was to stabilize an antimicrobial agent, levofloxacin (LVX), for sustained antibacterial activity by immobilizing the drug molecules in a layered double hydroxide (LDH) and embedded in a polyurethane substrate. As-prepared MgAl-LDH was calcined at 400°C and reconstructed with LVX for intercalation. The X-ray diffraction patterns and cross-sectional transmission electron microscopy images showed lattice expansion along the crystallographic c axis upon LVX intercalation, suggesting successful loading of the drug. Fourier-transform infrared spectra revealed that the structure of LVX was well preserved between LDH layers. Elemental analysis indicated that the loading capacity of LVX in the hybrid was 41.7%. Bacterial-colony forming inhibitory assay on Bacillus subtilis exhibited ~100% antibacterial activity of both LVX alone and LVX-LDH hybrid (LL). To determine sustainability of antibacterial activity by the hybrid, either LVX alone or LL hybrid was loaded in the polyurethane (PU) substrate for which antibacterial activity was evaluated before and after immersion in a phosphate-buffered saline for 3 days. The LVX-composited PU showed a dramatic decrease in antibacterial activity, down to 0% after buffer treatment; LL-composited PU still contained antibacterial activity (~34% of colony suppression) after phosphate-buffered saline immersion.

Infrared analyses of clay mineral samples are usually performed by transmission techniques. While transmission measurements are easy and inexpensive, the sample preparation plays a critical role in the quality of the data. Alternatively, attenuated total reflection (ATR) provides a powerful and often simpler analysis method. However, the ATR spectra reveal significant differences when compared to transmission spectra sometimes leading to confusion in the interpretations. Indeed, optical effects play a prominent role in the ATR spectral profile and their identification is mandatory for obtaining quantitative information regarding molecular/particle orientation or film thickness. The objective of the present study was to perform exact spectral simulations of montmorillonite films by making use of optical theory, including the determination of the anisotropic optical constants from the experimental reflectance spectra by Kramers-Kronig (KK) transformation. This methodology was used: (1) to choose the appropriate optical conditions for advanced and reliable characterization of clay minerals; (2) to extract quantitative information such as the estimation of the film thickness; and (3) to discriminate optical phenomena (optical interferences) from chemical/structural features of the sample.

Cis-1,4-polyisoprene latex (IRL) is the best alternative to natural rubber latex (NRL), and can help to avoid human allergic reactions caused by proteins in NRL. The mechanical properties of IRL are inferior to those of NRL, however. To address this issue, a novel strategy was developed using an in situ solution emulsification to prepare a latex composite incorporating sodium montmorillonite (Na-Mnt). The properties of the latex film prepared were investigated. The dispersion state of the Mnt in the latex composites and the morphology of the resulting composite films were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, the mechanism of Mnt reinforcement of IRL is described comprehensively. The results showed that the Mnt/IRL latex composites prepared were stable and excellent films were formed, similar to those of NRL. The current research provided an effective method for preparing high-performance composite films suitable for use in high-end medical applications.

Edible clays are consumed by diverse groups of people, especially of African descent, living in Africa and abroad, in a behavior known as geophagy. The clays are used topically as an emollient and drying agent and internally to control diarrhea. Scientific information concerning the chemical constituents and toxicity of edible clays is scarce. The aims of the present study, therefore, were to ascertain the chemical composition of white edible clays (WEC) and gray edible clays (GEC); to determine their toxicity profiles using analytical chemical methods; to test the acute and sub-acute toxicity of edible clays in their natural form as consumed; and to compare the raw and processed clays, and also to compare the latter to a proprietary drug known as ‘Mist kaolin’ (Moko®) which contains some clay along with other chemicals. Atomic absorption spectroscopy (AAS) and gas chromatography/mass spectrometry (GC/MS) were used to determine the elements present. White female Wistar mice and rats were used for the acute and sub-acute toxicity analyses, respectively. The results from AAS showed the presence of heavy metals and metalloids in both GEC and WEC, and the GC/MS revealed the presence of contaminants such as indomethacin and ethyl benzene, but quantities were below human toxicity levels. Doses of 100–500 mg/kg of either clay type could be harmful to the digestive system, but all of the tests revealed that edible clay is not toxic to humans unless very large amounts (500–1000 mg/kg of body weight) are consumed.

The imbibition of liquid by argillaceous rocks containing predominating kaolinite, illite, “open” illite, and montmorillonite with the use of absorption apparatus is described. Results of the following studies are given: (1) imbibition by pulverized and freely poured samples; (2) imbibition by specimens pressed (30 atm) into the form of small cylinders having a base of 100 mm2; (3) the course of imbibition by artificial aggregates of kaolin from Sedlec, Bohemia, pressed under different pressures (20, 30, 40 atm); and (4) imbibition by natural, oriented, ground, flat sections of the same samples which were prepared in the form of rectangular prisms, with a base of 100 mm2.

The constant k in the sorption equation, which is dependent on the form of clay particles and the tortuosity of pores in argillaceous aggregates under particular working conditions, has been computed. This constant has been calculated for water (polar liquid) and tetraline (nonpolar liquid).

A new quantitative diagram for identification of clay minerals by the imbibometric method has been constructed. In it, not only the time of imbibition and the qualitative features expressing themselves on the ground, flat section—such as swelling and nature of contours (Konta, 1961)—are taken into consideration, but also the area occupied by a drop of water and a drop of ethylene glycol and the wettability ratio Pegl/aq.

The refractory shales of the Purgatoire and Dakota formations in central Colorado were studied to determine the genesis of the kaolinite. The compositions of the shales were similar, with variation only in relative amounts and grain size of the component minerais. The shales consist primarily of kaolinite, subangular to subrounded quartz, and hydro-muscovite, with minor amounts of feldspar, montrcorillonite, mixed-layer clays, and occasional traces of gypsum and zeolites.

An inverse relation between the kaolinite and hydromuscovite contents suggests that hydromuscovite was an intermediate mineral in the formation of the kaolonite. Derivation of vermicular kaolinite from feldspar and mica was evident from examination of thin sections.. The thinly banded interfingered lenses of montmorillonite suggest a detrital origin rather than alteration in situ of a volcanic ash to bentonite.

Genesis of the kaolinite probably is similar to that proposed recently by Kesler for the Cretaceous clays of Georgia and South Carolina whereby feldspathic sands deposited in a near-shore environment were subsequently weathered to produce residual kaolinite. Winnowing of some of these clays and redeposition in downstream lagoons formed the fine-grained, carbonaceous, “flint” clays, whereas the plastic clays were formed by introduction of detrital montmorillonite.

A new technique for the x-ray analysis of soil colloids is proposed based on the finding that the interlayer swelling of montmorillonite persists in the presence of salt solutions and that the x-ray reflection representing the d(001) spacings becomes intensified in salted gels. The technique consists in flocculating the colloid from a suspension with sodium chloride, removing the “free” Fe2O3, Al2O3, and SiO2 by means of a solution of sodium citrate and sodium hydrosulfite, separating the cleaned colloid from the solution as a salted paste, and as such subjecting it to x-ray analysis. The method is not only more rapid than other recommended methods for x-ray analysis of soil colloids, but also — and which is of the utmost importance — yields a much more accurate picture of the mineralogical composition, particularly with respect to the content of the mica and the montmorillonite-type clays.

The composition of clay mineral suites derived from Triassic argillite and shale were compared with those of the consolidated parent sediments. Lockatong argillite, near the weathered zone, is composed mainly of illite, chlorite, and feldspar. In the clay horizon immediately above it, illite replaces the feldspar and kaolinite increases with distance from the contact until, near the top of the weathered zone, it is almost the only clay mineral present. A similar study was carried out on Brunswick shale. Here the parent rock consists mainly of illite, and some kaolinite, montmorrilonite, quartz, and feldspar. The kaolinite increases gradually as one progresses upward through the weathered zone, montmorillonite decreases, but approximately 30 per cent illite is still found in the top layers. Chlorite in the argillite near the weathered zone is randomly oriented while illite shows strong preferred orientation, probably indicating that chlorite formed in place during weathering. Illite in the Brunswick shale shows strong preferred orientation.

These two Triassic sediments are less than 5 miles apart and one may assume that they had a similar post-depositional environment. The difference in diagenetic development is striking and must be attributed mainly to the chemical composition and lithology of the parent sediment.

The orientation of clay particles in the solid rock was studied with the aid of an X-ray diffraction technique based on the analysis of cylindrical samples. Three-dimensional intensity data thus obtained were presented by vectors whose ends form a surface which is characteristic of the orientation of the particles. Generally the vectors generate hemispherical normal distributions whose principal vector coincides with the normal to the bedding plane.

Diagenesis of the Holocene-Pleistocene volcanogenic sediments of the Mexican Basin produced, in strata of gravel and sand, 1H2O- and 2H2O-smectite, kaolinite, R3-2H2O-smectite (0.75)-kaolinite, R1-2H2O-smectite (0.75)-kaolinite, R3-kaolinite (0.75)-2H2O-smectite and R1-1H2O-smectite (0.75)-kaolinite. Smectite platelets were formed from volcanic glass by loss of Si4+. Partially-formed platelets have Si4+ between 4.55−4.10 a.p.f.u., Mg+Mn and the interlayer charge are relatively uniform while VIAl+Fe3++Ti varies between 0.98 and 1.63 a.p.f.u. Almost fully transformed platelets have Si4+ of 4.08−4.04 a.p.f.u.; Mg+Mn and the interlayer charge decrease proportionally to increasing VIAl+Fe3++Ti. Smectite-kaolinite mixed layers have octahedral occupancies of 2.01–2.15 a.p.f.u., IVAl3+ 0.09–0.55 a.p.f.u. and interlayer charges about half that of smectite; structural formulae corresponding to smectite (0.75–0.80)-kaolinite indicate octahedral occupancy of 2.50 a.p.f.u., tetrahedral replacement 0–0.31 a.p.f.u., and interlayer charge 0.24–0.51 equivalents, some indicating interstratifications of beidellite. Kaolinite is presumed to have formed from K-feldspar; smectite-kaolinite interstratifications sustain the transformation of kaolinite to smectite in an increasingly siliceous high-cation environment. In the mudstones of low-hydraulic conductivity and practically stagnant alkaline fluids, glass was transformed to 2H2O-smectite lamellae of IVAl between 0 and 0.47 a.p.f.u., octahedral occupancy 1.70–2.00 a.p.f.u. and interlayer charge of 0.23–1.21 equivalents, some corresponding to beidellite. The interlayer charge increases with IVAl and decreasing occupancy of the octahedral sheet; the abundance of Mg+Mn is inverse to that of VIAl+Fe3++Ti.

Clay suspensions containing 1H2O- and 2H2O-smectite, kaolinite and R3-2H2O-smectite (0.75)-kaolinite lead to low-energy edge-to-edge particle associations, non-Newtonian pseudoplastic behavior, and maximum apparent viscosity of 180 Pa s at 0.008 s−1 followed by rapid descent. Clay fractions with slightly larger 2H2O-smectite contents and smaller kaolinite contents reach maximum viscosity of 3611 Pa s at a shear rate of 0.0018 s−1 and of 3300 Pa s at 0.0024 s−1. They denote two high-energy face-to-face particle associations, followed by slow descent of the apparent viscosity under viscous flow. Suspensions change from elastic to viscous behavior at shear stresses of 1.03 and 5.91 Pa, respectively. Clay suspension vibrated at a frequency of 1 Hz develops a shear storage dynamic modulus greater than the shear dynamic loss modulus or the energy is preferentially stored, whereas at 5 Hz more energy is dissipated than stored.

This paper deals with the dehydroxylation reactions of clay minerals and allied substances such as lamellar hydroxides, serpentine minerals, and amphiboles. Probably in all cases, these reactions occur topotaxially, that is, there is a three-dimensional similarity between the crystal structures of starting material and product, as a result of which each crystal of the starting material is changed into something approaching a single crystal of the product. Many investigators have studied the orientation relationships between starting materials and products, and their results have provided the main experimental foundation for hypotheses about the reaction mechanisms. These hypotheses have, however, rested also on assumptions, of which until recently three have usually been made. These are (i) loss of water occurs more or less uniformly from all parts of the crystal; (ii) the Si-O parts of the structure are more stable than the metal-oxygen parts; and (iii) the silica-rich material often presumed to be formed as a subsidiary product is pure SiO2. Recent work suggests, however, that none of these assumptions is securely based, and the purpose of this paper is to suggest an alternative approach to the problem.

The high temperature reactions of clay minerals are perhaps best understood by treating the latter as assemblies of close packed, or nearly close packed, oxygen ions with cations in the interstices. From this point of view, one might expect that the relatively small cations, such as Si4+, Al3+, Mg2+, and especially H+ would move more easily than the oxide ions. One would not expect the oxygen atoms that are lost as water to be necessarily those present initially as OH- groups; they are more likely to be those that can most easily escape from the structure, e.g. from near external surfaces or grain boundaries. On this hypothesis, a typical dehydroxylation reaction involves three types of process:

1. Loss of oxide ions from exposed or “donor” regions, and their combination with H+ ions from all regions, to form water. The donor regions are changed into pores.

2. Cation migrations. These may be of two kinds. Firstly, all cations other than H+ migrate from the donor regions into the remaining or “acceptor” regions, and H+ ions migrate in the opposite direction. Secondly, within the acceptor regions themselves, further migrations may cause differentiation into Si-rich and Si-poor parts to occur.

3. Changes in the type of oxygen packing in the acceptor regions, to complete the formation of the crystalline products. These last changes may occur throughout the acceptor regions, or only in certain parts of them.

Kaolinitic, montmorillonitic, illitic, and mixed-layer clay minerals are found in mud springs and mud pots of Yellowstone Park. A sequence of alteration is proposed as Phase I, alteration of bedrock and sediments by hot spring waters to produce three-layer clay minerals (including mixed layer species) and kaolinite-group minerals; Phase II, further alteration to produce a mud composed predominantly of kaolinite and some form of silica.

The exchange of [Co(NH3)6]3+ from its vermiculite complex has been carried out with a number of inorganic and alkyl quaternary ammonium ions of varying ionic sizes. The distribution and selectivity coefficients of the desorbing ions increase in the order: Li<Na<NH4<K<Rb<H<Cs for the monovalent, Ca<Mg for the bivalent and (C2H5)4N<(CH3)4N≪CTA (cetyl trimethyl ammonium) <CP (cetyl pyridinium) for the organic ions. The ΔG° values of some of the cation exchange reactions have been calculated by an equation of Kielland (1935).

Quantitative X-ray diffraction analysis of minerals can most readily be performed on dry powdered samples. Current methods for determination of expandable clays require either wet oriented samples treated with glycerine or glycol or dry, randomly oriented samples treated with amines. Trimethylamine has been used to expand the montmorillonite structure to a 13.3 Å basal spacing. Unfortunately, this spacing is subject to considerable peak interferences.

We therefore undertook a review of amine-montmorillonite complexes for more suitable reagents. The formate and acetate salts of tri-n-hexylamine and of dimethyl-benzylamine meet our requirements. The peak positions are the same as for glycerine complexes, while the physical properties are the same as for trimethylamine.

Detailed studies of tri-n-hexylammoniura ion absorption suggest single layers of ammonium ions lying parallel to the crystal basal plane, double layers in similar orientation, and a single layer with molecules on end. The most useful orientation is the latter, which occurs in the presence of an excess of the ammonium salt and gives a montmorillonite spacing 18 Å in dry powdered samples.

Linear calibration curves with a standard deviation of about 5 per cent of the amount measured can be prepared using the conventional internal standard techniques. Minimum detectable amount of montmorillonite with rate-meter techniques is 0.4 per cent and 0.2 per cent with scalar techniques.

Several thousand analyses using tri-n-hexylammonium ion have demonstrated its effectiveness for expanding a wide variety of sediments.

Batch data for the sorption of Eu and Th on pelagic sediments may be represented by equations of the form: ln M = A ln Cs + B/T + D, where M = concentration of sorbate on sediment, Cs = concentration of sorbate in solution, T = absolute temperature, and A, B, and D = constants. Thermodynamic interpretation of this equation leads to an expression for the true thermodynamic equilibrium constant of K = m/CsA and for the enthalpy change, ΔH, of d ln(M/CsA)/d(1/T) = −ΔH/R, where R = universal gas constant.

Experimentally, the sorption of Eu onto clay-rich sediments was very rapid in the first few seconds and slowed over an interval of minutes to hours. Rate curves were similar in shape to those of α-iron hydroxide, rather than of the oxalate-extracted residual sediment, indicating the importance of oxyhydroxide-like phases in the uptake of Eu onto red-clay sediments. For clay-rich sediments, numerical modeling reproduced the general features of a series of diffusion experiments. To a first approximation, the penetration of Eu into a sediment proceeded by saturation of the sediment to the depth of penetration and produced a sharp drop-off in sorbed + dissolved Eu concentration at the diffusion front. Higher partition coefficients (Kp) resulted in greater sorbed + dissolved concentrations, but reduced penetration. For calcareous sediments, however, Eu concentrations at the surface were much higher than at depth, presumably due to the formation of an insoluble carbonate.