The present paper represents an extension of recent work that considered the partitioning response of binary solvents placed into contact with charged, expandable clays. Previous theoretical work yielded a model of partitioning by performing a thermodynamic analysis, involving the work of polarization, on a binary solvent, treated as a continuum and residing within the interlayer space of a layered aluminosilicate clay. Partitioning, or the tendency for sorbed and bulk phases to have different compositions, was shown to be sensitive to the dielectric properties of the 2 solvents of the binary mixture and to the surface charge density on the clay, among other factors. Although previous experimental work has helped to validate the theory, additional work is reported here that looks at hysteresis effects, the role of the exchangeable cation (usually organic), the prediction of adsorption isotherms and the contribution that partitioning, or sorption, makes to the disjoining pressure that develops in binary solvent systems. In this current study, 3 different organo-clays were considered: Cetyltrimethylammonium (CTMA), Isopropanolammonium (IPA), and Benzylammonium (BA) montmorillonite. Solvent systems under study included: acetone/chloroform (a-c), acetone/quadricyclane (a-q) and acetonitrile/chloroform (an-c). While partitioning of the a-c system on CTMA-clay follows theory quite well, theory tends to over-predict partitioning for the a-q system on the same clay and under-predict partitioning for the an-c system on all clays. Predicted adsorption isotherms range from highly nonlinear to nearly linear. Finally, the delamination and subsequent swelling processes of BA-clay in a water/acetonitrile binary solvent system are very sensitive to composition, a result that is directly linked to the partitioning process.

Various fractions, ranging in size from 5 to 0·05 μ of natural clays from Mexico and Wyoming, occurring as heterogeneous or multicomponent cationic systems, were studied under specific equilibrium conditions of salt concentrations in the range found in many drilling fluids and formation waters.

Glass electrodes were utilized in this study. A Tektite electrode was found to have specific sensitivity to divalent cations.

Clay minerals occur most commonly as constituents of sedimentary rocks and nearly all the clay mineral species, with the possible exception of nacrite, have been found in sediments. Different clay minerals occur in different kinds of sediments and may be used as one criterion for classifying sediments and interpreting their genesis.

At the Desmoinesian-Missourian disconformity in southeastern Kansas a fossil soil zone is recognized by variations in clay mineralogy in the uppermost Desmoinesian Holdenville shale, which underlies basal Missourian Hepler sandstone. The clay fraction of the overlying basal Missourian Hepler sandstone contains kaolinite, slightly hydrated illite, quartz, and vermiculite. Chlorite (rather than vermiculite) is present in shaly portions of the basal Hepler sandstone. Clay-size minerals of the typical Holdenville shale (marine) are predominantly illite, chlorite, quartz, feldspar, and a very small quantity of kaolinite. The clay-mineral assemblages in samples from the upper part of the Holdenville shale indicate hydration of illite, sporadic increase in kaolinite, possible decrease in feldspar, and progressive modification and destruction of chlorite resulting in production of mixed-layer minerals.

Ion-exchange modeling is used widely to describe and predict ion-adsorption data on clay minerals. Although the model parameters are usually optimized by curve fitting experimental data, this approach does not confirm the identity of the adsorption sites. The purpose of the present study was to extend to divalent cations a previous study on the retention of monovalent cations on Na-saturated montmorillonite (NaMnt) which optimized some of the model parameters using density functional theory (DFT) simulations. The adsorption strength of divalent cations increased in the order Mg2+ < Cd2+ < Ca2+ < Sr2+ < Ba2+. After adding adsorption of metal hydroxide species (MOH+), the three-site ion-exchange model was able to describe adsorption data over a wide pH range (pH 1–10) on NaMnt. X-ray diffraction (XRD) analyses were conducted to investigate the interlayer dimension of clay samples under various conditions. The cation retention strengths of divalent cations did not correlate with interlayer dimensions. The XRD analyses of the Mnt showed a d001 value of 19.6 Å when saturated with alkaline earth cations, 22.1 Å with Cd2+, 15.6 Å with Na+, and 15.2 Å with H+. In the case of Na+, the 15.6 Å peak decreased gradually and disappeared, and new peaks at 22.1 and 19.6 Å appeared when the percentages of Mg2+ and Ba2+ adsorbed increased on NaMnt. The peak shifted from 22.1 to 20.3 and 19.6 Å when the pH increased for all cations except Cd2+, which stayed constant at 22.1 Å. The coexistence of multiple d001 peaks in the XRD patterns suggested that the interlayer cations were segregated, and that the interlayer ion–ion interactions among different types of ions were minimized.

The employment of clay minerals in the transport of water, nutrients, and contaminants depends on a few factors, including permeability, hydration behavior, ion-exchange efficiency, and more. With the application of external stress, it is still difficult to understand how clay particles swell and collapse, how water is retained, how hydration heterogeneities are formed within crystallites, and how interlamellar space is organized. The present work studied the link between geochemical, thermal, kinetic constraints (established at the laboratory scale), and intrinsic clay features by exchanging Na-rich montmorillonite (SWy2) with Ni2+, Mg2+, or Zn2+ cations. By comparing the experimental 00l reflections with the calculated reflections obtained from the structural models, quantitative X-ray diffraction (XRD) analysis has enabled the building of a theoretical profile describing the layer stacking mode (LSM) and allowed the description of interlayer space (IS) configuration along the c* axis. Regardless of the type of the exchangeable cations (EC), XRD modeling revealed that all samples exhibited interstratified hydration behavior within the crystallite size, which probably indicates partial or incomplete saturation of the IS. This theoretical result was defined by the appearance of two hydration states (1W and 2W), which were unrelated to the strain strength creating a higher degree of structural heterogeneity. Using the theoretical decomposition of the observed XRD patterns, the identification of all distinct layer populations and their stacking mode was achieved. The segregated LSM are, therefore, obviously superior as a function of stress strength.

The electrical state of the interface between a kaolinite-dominated clay sample and aqueous electrolyte solutions was characterized using low-frequency conductance measurements. From these measurements, the ζ-potential and surface conductivity contributions from the diffuse and non-diffuse parts of the electrical double layer were obtained. The suspensions were studied as a function of volume fraction, electrolyte concentration, and electrolyte type (LiCl, NaCl, KCl, CsCl, CaCl2, SrCl2, and BaCl2). Interpretation in terms of the surface conductance revealed that a substantial part of the surface conductivity originates in the inner part of the double layer. Electrokinetic potentials and related diffuse double layer properties are highly dependent on the nature of monovalent counterions, whereas divalent counterions do not show such clear dependencies. Further presented was a simple way to estimate the order of magnitude of counterion mobilities in the inner part of the electrical double layer. All counterions were shown to have a substantial mobility in the inner part of the double layer. Finally, we suggest that the apparent ion-specific effects observed in the diffuse part of the double layer are at least in part related to the finite size of the counterions. Our findings are relevant to scenarios where fluid flow in porous media is accompanied by charged species transport, e.g., in electro-osmotic remediation, spectral-induced polarization, or permeability measurements.

Fe is a common substituent in palygorskites (Plg), but its effect on the microscopic properties is unclear. In the current study, molecular dynamics (MD) simulations were carried out to investigate the effect of Fe on the properties of the nano-pores in Plg. The structures and dynamics of water and Na+ ions in the pores were computed by analyzing the MD trajectories. The results revealed that for both Fe-containing and ordinary Plg, zeolitic water molecules can diffuse into the pores with very low mobility whereas Mg-coordinated water fails to escape. Na+ ions show no obvious diffusivity because they are fixed above the Si–Osix-membered rings. Detailed comparison indicates that Fe-substitution has no significant influence on the pore properties of Plg.

The exchange of Rh(NBD)(Pϕ3)2+, Rh(NBD)(PMe2ϕ)3+, Rh(COD)(Pϕ3)2+, and Rh(PMe2ϕ)4+ on hectorite was studied in methanol/dichloromethane, acetone, dimethylformamide, and acetonitrile. At low initial Rh+ concentration and short contact times, ion exchange was the predominant process, and its selectivity and maximum capacity were solvent-dependent. High initial Rh+ concentrations, long contact times, and the most polar solvents favored intersalation and salt precipitation. In all experiments monolayers of complex formed in the interlamellar space and were very tightly held. The complexes retained their integrity on the surface even after removal of all solvent molecules.

Recent mud sediments of Mississippi Sound, Mobile Bay and contributory rivers contain a clay mineral assemblage composed essentially of kaolinite and montmorillonite. Illite is present as a minor component.

The montmorillonite in these sediments appears to be at least partially complexed with organic material. This association is particularly evident in river and river mouth deposits and seems to be modified or partially destroyed in sea water. Organic material has been leached from river sediments with a sodium hydroxide solution and combined as a clay-organic complex with montmorillonite from Clay Spur, Wyoming.

The clay mineralogy of sediments from Mobile Bay and areas outside of the barrier island chain is very similar to that of the river sediments. Within Mississippi Sound an apparent increase in the montmorillonite-illite content of the sediments relative to kaolinite from east to west is attributed to the invasion of mud from the Mississippi Delta into the western part of the Sound.

Chemical analyses of these sediments along a section from fresh water to Mississippi Sound localities have shown a progressive increase in magnesium, potassium, and sodium, and a decrease in calcium.

The formation of typical bentonites occurs in two stages. The first stage comprises the development, transportation, and deposition of the volcanic ash, which determines the geometry and structure of the bentonite rock and influences the alteration of the ash during the second stage. The second stage encompasses the alteration of volcanic glass to montmorillonite and other minerals.

The distribution of ash particles in the bentonite beds of Wyoming is satisfactorily explained by a theoretical model based on equations similar to heat flow equations. An extended model, assuming a disk-shaped volcanic cloud containing ash particles, also accounts for the geometrical shapes and geographic variations of the textural parameters of the bentonite beds.

The alteration of Wyoming bentonite ashes to montmorillonite occurred undoubtedly at low temperatures in an aqueous environment. Petrologic evidence indicates that all of the Wyoming ashes and many ashes deposited elsewhere contained sufficient magnesium to form montmorillonite with no addition necessary from without. Also evidence indicates variations of pH of perhaps 5 to 8 made little difference in the alteration products of the ashes.

Laboratory evidence of the processes and products of alteration of ashes to bentonite accord with field observation. With simplifying assumptions, the formation of montmorillonite from volcanic glass may be elucidated from the viewpoint of the stability of montmorillonite with respect to other similar minerals. The results of theoretical calculations of the mineral stabilities will be presented. Three energy parameters will be considered: the Coulomb energy, Van der Waals’ repulsion, and the London energy Thermal motion of the atoms will be taken into account.

A purple-colored clay of 1M mica polymorph in association with lead-zinc ore was collected from an abandoned mine dump near Silverton. Colorado. Electron micrographs show that the crystallites of the clay are less than 2μ in size and have poorly developed hexagonal outlines. Differential thermal and i.r. absorption analyses indicate similarity with those of muscovite. The structural formula of the 1M mica polymorph is (K1.45 Na0.02) (Al3.75 Mg0.19) (Si6.90 Al1·10) O20 (OH)4. The purple color may be related to trace amounts of manganese in the clay.

Extinction bend contours, observed in Cs-treated mica-vermiculites by transmission electron microscopy, give information on the morphology and crystal orientation and continuity in individual particles of clay size. Interlayer Cs apparently stretches that part of the silicate sheet in closest proximity and when exchange by Cs is incomplete, warping of the particle occurs. Warping favors the appearance of bend contours in transmission electron microscopic images of the particles. These contours terminate at crystal boundaries within a particle. A specimen tilting stage is useful in bringing the contours into view and in “exploring” individual particles.

Two kaolins were given five successive processing steps designed to remove a number of impurities: (1) removal of nonclay and soluble fractions; (2) removal of organic material; (3) removal of iron oxides; (4) removal of allophane; and (5) removal of three- layer lattice minerals. After each of these steps, consistency curves were obtained for each of the clays at both 6.5 and 9.0 pH on slurries containing up to 50 weight % solids.

Photomicrographs and electron micrographs showed that Ka-7 from Bath, South Carolina, contained generally smaller particles than Ka-2 from Macon, Georgia. Lowering the pH from 9.0 to 6.5 in Ka-2 produced no change in plastic viscosity at the lower concentrations and a decrease of about 30 per cent at higher concentrations after processing step 1. A comparison of the same evaluations of step-1-treated Ka-7 showed that the decrease in pH reduced the plastic viscosity by 50 per cent at 5 per cent clay concentration and increased the plastic viscosity by 100 per cent at 35 per cent clay concentration. After complete processing, lowering the pH from 9.0 to 6.5 increased the plastic viscosity at all concentrations for both kaolins by 5–20 per cent. At a clay concentration of 30 per cent, complete processing decreased the plastic viscosity of Ka-2 from 0.4 to 0.02 poise and of Ka-7 from 0.4 to 0.06 poise. Ka-7 showed progressive viscosity changes due to the processing, while Ka-2 showed only a marked change in viscosity for processing step 5. The rheological changes of Ka-2 and Ka-7 with processing are supported by the X-ray diffraction data at the various processing stages. X-ray diffraction data confirm that processing step 5 effectively removed a three-layer lattice expandable mineral from Ka-2, while processing step 3 effectively removed a different three-layer expandable mineral from Ka-7.