The effect of heat treatments on the total charge and water adsorption by Ca-, Na- and Li-saturated kaolinite was studied using extraction techniques and thermal gravimetric analysis, respectively. Measurements of cation exchange capacity indicated that the total charge of Li-kaolinite was reduced by approximately 50% after heating to 110 or 130°C. In contrast, the total charge of Ca-kaolinite remained essentially constant while that of Na-kaolinite decreased slightly. Water adsorption and desorption on Ca- and Li-kaolinite following heat treatments at 150°C were consistent with the total charge of the respective kaolinites. Ion extraction of Li-kaolinite using NH4C1 revealed that only 6% of the Li remained exchangeable after heating, while Al and H were released. Thus, non-exchangeable Li ions not only reduced the total charge of the kaolinite but also displaced Al and H from the kaolinite structure. Infrared spectroscopy also indicated that Li migrated into the kaolinite structure and replaced a portion of the Al from the octahedral sheet. The results presented here indicate that Li-kaolinite represents a surface of reduced charge rather than a surface free of cation-hydration effects. Therefore, Li-kaolinite is not recommended as a reference for the study of vapor-phase adsorption, and conclusions based on such a reference material should be reevaluated.

Sedimentologic zones that are differentiated by changes in lithology, mineralogy, chemical composition, and crystal morphology observable in scanning electron micrographs occur in Missouri high-alumina clay deposits. These properties and changes suggest that the high-alumina materials originated from Pennsylvanian-age, paludal sediments deposited in depressions underlying Paleozoic carbonate rocks. Alumina was relatively enriched in zones of the deposits by leaching of silica and of alkali and alkaline earth metals from the sediments. The most intense leaching occurred on the highest parts of the Ozark Dome.

Diaspore is the predominant high-alumina mineral. Boehmite, although far less abundant than diapsore, may have paragenetically preceded diaspore in some deposits. Chlorite, presumably an Al-rich variety because the content of MgO is typically <0.5%, is also present. Li, which is sporadically present, is inferred to have accumulated in the chlorite which may be a proto-variety of cookeite. Because Li+ and Al3+ are similar in size, Li is inferred to have accompanied Al as a resistate element in contrast to K and Na which were leached from parent phyllosilicates.

The prevailing concept that positive-edge to negative-face attraction accounts for the rheological behavior of montmorillonite suspensions at low electrolyte concentration was investigated. In one experiment, Mg2+ released from Na-montmorillonite was measured at several NaCl concentrations; in a second experiment, the viscosity, η, and the extrapolated shear stress, θ, were measured at several clay concentrations, pHs, and NaCl concentrations; and in a third experiment, the absorbance, A, was measured at two wavelengths (450 and 760 nm) at different clay and electrolyte concentrations. The released Mg2+ decreased with increasing NaCl concentration until it became zero at a NaCl concentration between 0.01 and 0.02 M, depending on pH. Thereafter, it increased with increasing NaCl concentration. Both θ and η were highly correlated with the amount of released Mg2+. Also, A remained constant until the NaCl concentration corresponded to that at the minimum of θ. Thereafter, it increased and became linearly related to θ. These results suggest: (1) positive-edge to negative-face interaction cannot solely account for the rheological properties of montmorillonite at low electrolyte concentration, and (2) the release of octahedral Mg2+ from montmorillonite affects θ, because it reduces the negative charge on the particles and, thereby, the repulsive force between them.

Imogolite was synthesized at 25°C by aging partially neutralized solutions containing monomeric silicic acid and polymeric hydroxy-aluminum ions for 7 years. Solutions having an initial Si/Al molar ratio of about 0.5 and pHs of 4.0–4.5 produced the largest yields of imogolite, followed by those having an initial Si/Al ratio of about 1, although imogolite was not the principal product. Electron microscopic examination showed a small amount of imogolite fibers embedded in a noncrystalline gel-like substance. Traces of imogolite were detected in solutions having an initial Si/Al ratio of about 2, but no imogolite was found by electron microscopy in products from solutions having an initial Si/Al ratio of about 4. Only gibbsite formed from solutions having initial Si/Al ratios of <0.27. The diameter of the tubular structural unit of the imogolite produced in these experiments was 23 ± 2Å, close to that of natural imogolite.

Two kerolite and one garnierite samples were subjected to progressive heat treatments prior to their examination by infrared spectroscopy (IR) in the 1200-600-cm−1 and 3800-3000-cm−1 regions. The heat treatment of the garnierite (a mixture of nepouite and pimelite) selectively dehydroxylated the nepouite thus allowing an examination to be made of the OH-vibration bands due to the pimelite. Both the relative intensities of the 710-670-cm−1 doublet and of the different OH-stretching bands indicated the Ni content of this pimelite to be about 70%. The heat treatments did not modify the 1200-600-cm−1 region of the spectra of kerolites but caused a noticeable sharpening in the OH-stretching region. The relative intensities of the structural OH-stretching bands of dehydrated kerolites showed that they differ from Ni-talcs of similar composition in the distribution of Ni and Mg in the octahedral sites. These cations are randomly distributed in Ni-talc but are mainly segregated into Mg and Ni domains in kerolite. Changes in sharpness, intensity, and position of the structural OH-stretching bands of the kerolites as temperature increases and dehydration progresses are similar to those undergone by Mg- or Li-saturated trioctahedral smectites. Also thermal analysis curves of these minerals show similarities with those of Mg- and Ni-saturated smectites, and suggest that in kerolites too, the hydration water is associated with interlayer (though non-exchangeable) Ni and/or Mg cations.

The onset of the mobilization of fine particles of quartz (fines) in sandpacks was determined by comparing the theoretically calculated hydrodynamic and colloidal forces acting on a fines particle near a representative sand grain. The results show that the mobilization of fines depends strongly on the chemistry of fluids present in the reservoir. Specifically, a critical electrolyte concentration exists for mobilization, which depends on the pH. For large particles of fines and relatively high fluid velocity, the mobilization of fines may depend on the fluid velocity, but in a narrow range of electrolyte concentration. The types of interactions between the fines and sand grain surfaces were corroborated by direct visual observations using a traveling microcell pack.

The mobilization of fines in sandstones leads to a reduction of permeability (i.e., a reduction of the hydraulic conductivity).

Several hydrates can be synthesized from well-crystallized kaolinites; of importance to the present work are a 10-Å hydrate (called the QS-10 hydrate), an 8.6-Å hydrate, and two kinds of partially dehydrated mixed-layer hydrates. One kind is a series of unstable materials with d(001) varying continuously between 10 and 8.6 Å, and the other kind is stable with d(001) approximately centered at 7.9 Å. The 10- and 7.9-Å phases have been observed in halloysites by many workers using X-ray powder diffraction, and the 8.6-Å phase has been seen by others in selected area electron diffraction photographs. Infrared spectra reveal additional similarities between the synthetic hydrates and both halloysite(10Å) and partially dehydrated halloysites. Because of these similarities, the synthetic hydrates can be used to develop a model for the dehydration of halloysite(10Å).

Previous work on the 10- and 8.6-Å hydrates identified two structural environments for the interlayer water. In one, the water is keyed into the ditrigonal holes of the silicate layer (hole water), and in the other, the water is more mobile (associated water). Both types are found in the QS-10 hydrate and halloysite(10Å), whereas only hole water occurs in the 8.6-Å hydrate. In the QS-10 hydrate, stronger hydrogen bonding between hole water and the clay makes the hole water more stable than the associated water. This difference in stability is responsible for a two-step dehydration process. The first step is the loss of associated water which results in a material with d(001) = 8.6 Å. This stable hydrate must be heated to temperatures near 200°C to drive off the remaining hole water. The less perfect structure of halloysite and its common curvilinear morphology reduce the difference in stability between hole and associated water molecules, so that when halloysite(10Å) dehydrates, loss of hole water and associated water overlaps, and the d-spacing goes directly to 7.2–7.9 Å.

Unheated natural mixtures of manganite and secondary pyrolusite, from the same lateritic manganiferous sequence, were studied in different orientations by high-resolution transmission electron microscopy (HRTEM), electron diffraction, and energy-dispersive X-ray analysis (EDX) to determine the fine structure of these phases, their possible crystallographic relations, and the genetic processes that led to the formation of the pyrolusite. Typical palisadic texture was observed for both minerals. Characteristic cracks parallel t. (010) of the pyrolusite structure and in particular <210> microfissures in manganite were noted as signs of structural accommodation accompanying the transformation phenomenon between these two minerals. A previously unreported manganese oxide of the spinel-type (γ-Mn2O3 or Mn3O4) was also identified in the original mixture. This oxide gave pure microdomains as intergrowths with pyrolusite adjacent to manganite. This is the first report of a natural occurrence of γ-Mn2O3. The manganite-pyrolusite transformation process and an unsuspected γ-Mn2O3 (Mn3O4)-pyrolusite transition were directly illustrated in detail for the first time. Interfaces between the concerned phases were not sharp or smooth, but exhibited strong strain contrasts and interferential periodicities. Lattice images and microdiffraction patterns proved that both transformations were oriented, suggestive of topotactic relations. In addition, the principal minerals in the matrix (illite, kaolinite, and goethite) were examined for a better understanding of their role in Mn-oxyhydroxides transformations.

Sequential cation-exchange capacity (CEC) measurements were obtained from standard clays using a mechanized, variable-rate leaching device. The device consists of a motorized screwjack and as many as 24 leaching tubes coupled to 60-ml plastic syringes. Controlled withdrawal of the syringe plungers produces a vacuum that permits samples in the leaching tubes to be extracted at a uniform rate. A single, 8-hr leaching of clays with 35 ml of salt solution was found to be comparable to multiple saturations or displacements using a centrifuge. CECs consistent with published values were obtained for reference 2:1 clay minerals using both acetate and chloride salts of Na, Ca, and Mg. Potassium-exchange capacities were also successfully measured following in situ thermal treatment of samples in the leaching tubes. Variations in measured CECs for kaolin-group minerals due to salt intercalation were minimized by using chloride rather than acetate salts and by washing with a dilute aqueous solution of the saturating cation following initial saturation. The mechanical extractor significantly reduced the effort required to perform conventional CEC determinations without sacrificing analytical precision.

Mössbauer spectra of 15 hematites with Al substitutions between 0 and 10 mole % were taken at room temperature. X-ray powder diffraction indicated dimensions of these hematites in the c-direction to range upwards from 27 nm to crystals large enough to show no line broadening. The Mössbauer spectra showed that magnetic hyperfine fields decreased both with increasing Al-for-Fe substitution and with decreasing crystal size. These relationships indicate that hyperfine field variations cannot, as has been done in the past, be unequivocally related to Al substitution alone. Hyperfine field reductions were paralleled by Mössbauer line broadening due to hyperfine field distributions. Only the hematites heated to 1000°C showed a significant variation of quadrupole splittings with Al substitution. No dependence of quadrupole splitting on crystal size was observed, indicating no detectable distortion of coordination polyhedra in the particle size range studied.

1-4-diazabicyclo[2,2,2]octane dihydrochloride (DABCO·2HC1) was reacted with two vermic-ulite samples to produce intercalates which, at room temperature, had relatively sharp, single crystal X-ray diffraction patterns. At higher temperatures (250°C) the stacking order decreased, and consequently the 0kl reflections with k ≠ 3n became increasingly diffuse. The stacking order of previously heated samples returned when they were cooled. A superstructure was present in which DABCO cations occupied the corners and center of a cell 3a × b, compared with the standard vermiculite cell.

DABCO-intercalated Nyasaland vermiculite had the following monoclinic subcell (symmetry C1) parameters under ambient conditions: a = 5.341(2), b = 9.249(3), c = 14.50(1) Å, and ß = 96.98(5)°. Differential Fourier analyses and least-squares refinement led to a final R value of 12.6% for 1814 reflections. The crystal structure analysis showed that individual DABCO ions were not symmetrically positioned between the silicate layers. A network of inorganic cations and water molecules was also present and governed the interlayer separation. At 250°C the d value was 13.7 Å, consistent with a dehydrated structure, in which each organic pillar has one amino group keyed into a ditrigonal cavity and the other amino group riding on the basal oxygens of an opposite tetrahedron.

Regular vertical variations in mineralogy and chemistry indicate that underclay beneath the Herrin (No. 6) coal in southwestern Illinois has undergone in situ alteration. Alteration resulted from the downward movement of hydrogen ions, as indicated by the progressive leaching of acid-sensitive minerals adjacent to the coal. Mineralogical trends observed in the underclay with increasing depth below the coal include: (1) a decrease in the expandability of mixed-layer illite/smectite (I/S); (2) an increase in the amount of ordered I/S with respect to randomly interstratified I/S; (3) an increase in the amount of discrete illite with respect to expandable clays; and (4) an increase in chlorite and calcite. Ordered I/S is the dominant mixed-layer clay where calcite is present, but randomly interstratified I/S dominates where calcite is absent. The pH of the underclay also increases with depth. These trends are consistent with an origin by acid leaching of a preexisting mineral assemblage that included illite, chlorite, and calcite. Other acid-alteration trends may be expected for different precursor minerals and for different leaching intensities and durations.

The electron spin resonance (ESR) spectra and the natural and gamma-induced thermoluminescence (TL) glow curves of a series of variably cation-exchanged Fe-Ca-clays prepared from SWy-1 montmorillonite were examined. The ESR signal (g = 2) intensity associated with the surface Fe was found to increase linearly with surface Fe content up to a nominal concentration of 50% exchangeable Fe. At > 50% exchangeable Fe, no appreciable increase in the signal was noted. The TL intensity decreased linearly with increasing surface Fe up to 50% nominal exchangeable Fe. At > 50%, the signal was not appreciably further diminished. The natural TL showed only a high-temperature peak, but irradiation produced an additional low-temperature peak. One month after gamma-irradiation, the integrated TL signal was still 10–100 times higher than that from the non-irradiated material. Thus, (1) surface iron clusters may form above a certain critical Fe concentration; (2) the Fe clusters are probably less effective in quenching TL than are single Fe atoms, implying interaction between surface Fe and the stored energy content of the material; and (3) the electronic energy stored in the material as the result of gamma-irradiation is only slowly dissipated.

Clay minerals and zeolites, candidate backfill minerals for nuclear waste repositories, were treated with saturated NaCl brine and Mg-rich (Mg-Ca-Na-K) brine at 200°C and 300°C for 4 weeks under a confining pressure of 30 MPa. The Al concentrations released in NaCl brine were lower than those in Mg-rich brine at both temperatures indicating that the Mg-rich brine is more acidic than the NaCl brine under these hydrothermal conditions. The Si concentrations in both brines were low because of the relatively acidic conditions developed during the hydrothermal treatment. As determined by X-ray powder diffraction or by specific Cs and Sr sorption measurements, no alteration could be detected in clay minerals treated with NaCl brine at 200°C. Among the zeolites tested, only phillipsite and erionite altered to analcime in NaCl brine at 200°C. Zeolites and most of the clay minerals tested did not alter in the Mg-rich brine treated at 200°C. Vermiculite altered to randomly interstratified vermiculite/K-vermiculite (mica-like) by selective K uptake from the Mg-rich brine.

At 300°C, the clay minerals did not greatly alter, whereas the zeolites altered to analcime and/or albite in the presence of the NaCl brine. In the Mg-rich brine, Al-rich montmorillonite from Wyoming did not alter, whereas Al-poor montmorillonite from Texas altered to randomly interstratified montmorillonite/ illite at 300°C. Vermiculite collapsed to form K-vermiculite (~ 10.2 Å) by the selective uptake of K from the Mg-rich brine at 300°C. Most of the zeolites altered to smectites in the Mg-rich brine at 300°C because of the acidic conditions generated by the hydrolysis of Mg. The selective Cs-sorption Kd decreased from 11,700 for untreated phillipsite to 240 and 15 for the hydrothermally produced analcime/albite mixtures from the phillipsite at 200° and 300°C, respectively, in NaCl brine. These results suggest that montmorillonites and mordenites are relatively more resistant than vermiculite or other zeolites at elevated temperatures and pressures in concentrated hydrothermal brines expected in a salt repository.

Natural clays are often employed as substrates for heterogeneous catalysts. However, the direct use of raw clays as catalysts has received less research attention. The objective of the present study was to help fill this gap by investigating catalytic properties of raw pelagic clays (PC) collected from the Indian Ocean. The raw PC were discovered to be efficient catalysts in the reduction of 4-nitrophenol (4-NP) in the presence of NaBH4. The effects of parameters including pH values, dosages of PC, and initial concentration of 4-NP and NaBH4 on the conversion or degradation rate of 4-NP have been investigated. The 4-NP was observed to be completely degraded within 480 s under conditions of 0.10 mM 4-NP, 25.0 mM NaBH4, and 0.20 g/L PC at an initial pH value of 7.0. The apparent rate constant was evaluated to be 27.53 × 10–3 s–1. Unlike previous pseudo-first order kinetics experiments, the induction period and degradation stages were observed to occur simultaneously during the PC catalysis. The S-shaped kinetics for 4-NP conversion was found to be perfectly matched by Fermi's function, and the enzyme-like catalysis by PC was appointed to describe the kinetics. Species of Fe(III), Mn(IV), and Mn(III) in PC were found to be essential, and were partly reduced to Fe(0) and Mn(II) by NaBH4 in our reaction, contributing to rapid conversion of 4-NP to 4-aminophenol (4-AP). The raw PC was converted to magnetic PC (m-PC) particles, which made PC particles separate easily for cycling use. This discovery would also have applications in continuous flow-fluid catalysis.

Pillaring of montmorillonite and beidellite with aluminum polyhydroxypolymer takes place first by the saturation of the cation-exchange capacity by monomeric and/or dimeric aluminum hydroxide species and then the intercalation of the so-called Al13-polyhydroxypolymer. The clay slurry must have a solid concentration greater than 0.01% (w/w) to produce a basal spacing of about 18 Å. Sizeable clay tactoids must therefore exist in the slurry in order to produce a turbostratic structure ordered along the c axis. The main difference between pillared montmorillonite and pillared beidellite seems to be a more ordered distribution of pillars within the interlamellar space of the clays that are rich in tetrahedral substitutions. Recent 27Al and 21Si high-resolution nuclear magnetic resonance data suggest that this higher degree of ordering results from the reaction of the aluminic pillars and the clay sheet near the sites of the tetrahedral substitutions.