Intercalation of naphthalene and anthracene into alkyltrimethylammonium (CnH2n+1(CH3)3N+; n = 8, 12, 14, 16, and 18)-montmorillonites was carried out by novel solid-solid reactions at room temperature. Octyltrimethylammonium(C8)-montmorillonite did not form an intercalation compound with either naphthalene or anthracene. Naphthalene was intercalated into both dodecyltrimethylammonium(C12)- and octadecyltrimethylammonium(C18)-montmorillonites to give intercalation compounds. On the other hand, the solid-solid reaction between dodecyltrimethylammonium(C12)- or tetradecyltrimethylammonium(C14)-montmorillonite and anthracene gave only partly intercalated compounds while hexadecyltrimethylammonium(C16)- and octadecyltrimethylammonium(C18)-montmorillonites gave single phase intercalation compounds. The hydrophobic interactions between alkylammonium-montmorillonites and the aromatic compounds are thought to be the driving force for the solid-state intercalation. The extent of the increase in the basal spacing may also be involved in the different reactivity.

In this paper, we use the unequal radius modified Gouy-Chapman theory to evaluate the effect of the ionic size of the electrolyte on the swelling pressures (II) in different clay systems immersed in electrolytic solutions. First the model is applied to a 1:1 electrolyte to show that the coion size is only important at surface charge densities much lower than those found in typical clay systems. The swelling pressure is calculated and the results are compared with experimental data. Literature ionic radii values are used to show the dependence of the swelling pressure on the specific counterions present. Next the model is applied to a 1:1 and 2:1 electrolyte mixture with unequal-sized counterions to show the swelling pressure is highly dependent on both counterion sizes. The unequal and same-sized cases are compared.

Transmission electron microscopy (TEM) was utilized to determine the origins of berthierine and chlorite in the core of the footwall alteration zone of the Kidd Creek massive sulfide deposit, Ontario. TEM images show lamellar intergrowths of packets of berthierine, mixed-layer chlorite/berthierine, Fe-Mg chlorite, and relatively Fe-rich chlorite that contain dislocations, stacking faults, kink bands, and gliding along (001). Interstratification of packets of berthierine and chlorite with one to several tens of layers commonly is associated with terminations of a layer of chlorite by two layers of berthierine. Layers in adjacent domains of berthierine and chlorite are continuous across interfaces that transect their common {001} planes. High-strain zones that cut across cleavage planes, consisting of distorted layers and lens-shaped pores, are associated with stacking faults and gliding along cleavage planes in chlorite crystals. Similar features separate interstratified chlorite/berthierine of different structures and textures, implying development of such composite grains after deformation of chlorite. Electron diffraction patterns show that the chlorite is an ordered one- or two-layer polytype or a one-layer polytype with semi-random stacking, and that the berthierine is a one-layer polytype with semi-random stacking epitaxially intergrown with chlorite.

Coexisting chlorite and berthierine have nearly identical ranges of compositions, containing Si ≅ 5, Al ≅ 6, and Fe ≅ 6.5–8.5 pfu, and minor, variable Mg and Mn contents, in formulae normalized on the basis of 20 total cations. This implies polymorphism among Fe,Al-rich members of the serpentine and chlorite groups. In one of the samples, berthierine and mixed-layer chlorite/berthierine coexist with chlorite having two compositional ranges, including Fe-rich chlorite with a relatively wide range of Fe-Mg contents, and a dominant Fe-Mg chlorite. In another sample, compositionally homogeneous Fe-rich chlorite is associated with berthierine and mixed-layer chlorite/berthierine; Fe-Mg chlorite was not detected.

The microstructural relations and the presence of coexisting polymorphs, complex mixed layering, heterogeneous polytypism, and wide ranges of mineral compositions are consistent with replacement of chlorite by berthierine under non-equilibrium retrograde conditions, in contrast to the generally assumed prograde origin for other berthierine occurrences.

The effect of anions on clay dispersion and the hydraulic conductivity (HC) of clay-sand mixtures has received little attention. This study investigates the effect that adding small amounts of anions has on the dispersivity and HC of reference clays. Mixtures of 3 and 6 g 100 g−1 kaolinite, smectite, and illite with quartz sand were packed in columns. The columns were saturated with Ca and then leached with 1 molc m−3 of one of the following organic and inorganic Na salts: chloride, hydroxide, EDTA, silicate, citrate, formate, oxalate, hexametaphosphate, orthophosphate, tartrate, or humate. Changes in HC and clay concentration in the effluent were measured and clay dispersion was evaluated as a function of the various anions added. In the kaolinite clay-sand mixtures, a significant amount of clay was observed in the effluent for all anions tested, and the HC increased above its original value. The HC of smectite clay-sand mixtures decreased following the addition of the various anions. Dispersed clay appeared in the effluent only upon addition of citrate or hexametaphosphate. In the latter two cases, the HC started to increase once maximum clay concentration appeared in the effluent. Clay concentration in the effluent of smectite was one order of magnitude lower than that of kaolinite. Illite clay-sand mixtures showed dispersion behavior intermediate between smectite and kaolinite but behaved in the same way as kaolinite with respect to HC changes.

Calcite crystals exposed to clay volatiles react with some components of these volatiles, giving rise to a variety of surface morphologies. F, Cl, and S in different proportions were detected by electron microprobe analysis of the calcite surfaces. Under identical experimental conditions, volatiles from every clay mineral examined caused a specific morphology and chemical composition of the calcite surfaces, but these varied with temperature of the calcite. Changes in pH values and mass spectra of the volatiles after passage through calcite demonstrate that even on rapid heating some clay volatile-calcite reactions occur at temperatures as low as 150°C. Species other than those detectable by electron microprobe analysis also participate in the reactions in which CO2 is liberated.

Fe(II) and Fe(III) in various proportions were coprecipitated by NH3 at pH ≈ 11. The Fe(II)/Fe(III) ratio (x) was varied from 0.10 to 0.50. After stabilization by aging at pH ≃ 8 in anaerobic conditions, hydrous precipitates were characterized by electron microscopy, Mössbauer spectroscopy, and kinetics of dissolution in acidic medium. At any x value, all stable products exhibited the structure of (oxidized) magnetite. For x ≤ 0.30, two distinct species were coexisting: the one (“m”) was made up of ca. 4nm-sized particles with a low Fe(II) content (Fe(II)/Fe(III) ≈ 0.07), and the other (“M”) consisted of particles of larger, more or less distributed sizes, and composition Fe(II)/Fe(III) ≈ 0.33; “M” increased relative amount with increasing x. For x ≥ 0.35, “M” was the only constituent and its Fe(II)/Fe(III) ratio was equal to x. “M” is identified with (nonstoichiometric) magnetite, whereas “m” is likely to be an oxyhydroxide. Mechanisms of formation are discussed, and a phase diagram is proposed which schematizes the evolution of the coprecipitation products with x and with time. Addition of Fe(II) after the precipitation of Fe(III), instead of coprecipitation, yielded very similar results.

Authigenic chlorites and illites coexisting in clastic reservoir sandstones have been studied by energy dispersive X-ray spectroscopy (EDS) in the transmission electron microscope (TEM). All 16 samples studied are drill or sidewall cores from sandstones of relatively uniform age situated offshore Norway with burial depths ranging between 2400 m and 5000 m and representing temperatures between 90°C and 180°C. Chlorites and illites with authigenic equilibrium type texture and morphology were analyzed by EDS. Tetrahedral Al and octahedral Fe+Mg in chlorite increases with burial at the expense of Si and vacant octahedral positions in the chlorite structure. Illites show a clear increase in K. These factors indicate that a continuous chemical modification of these minerals takes place in the diagenetic interval studied through continuous dissolution and precipitation reactions.

The internal equilibrium status among chlorite-illite pairs has been evaluated through coupled substitution reactions. Compositional data of chlorites and illites from arenites at present burial temperatures between 90° and 180°C have been used to calculate end member activities and reaction quotients of the combined Tschermak reaction:

$Muscovite+Clinochlore=MgAl-celadonite+Amesite.$

The reaction quotient data in the 90° to 180°C temperature range have then been compared with the equilibrium curve for the same reaction, and found to be in reasonable agreement. This indicates that chlorites and illites in these arenites grow at near equilibrium conditions.

The data set has also been compared with chlorite-illite pairs from hydrothermally altered arenites of the Salton Sea area. For chlorite-illite containing assemblages, these data agree well with the diagenetic ones. The introduction of biotite at higher temperatures alters with the iron-magnesium distribution and breaks down the substitution relationship between chlorite and illite.

The model predicts an increasing stability of muscovite and clinochlore components with increasing temperature, while celadonite and amesite would be stabilized with increasing pressure. This is consistent with high pressure occurrences of phengite. However, at the low pressure region of diagenesis and hydrothermal alteration, the temperature effect is dominant.

One Tertiary and two Cretaceous gray kaolin sites in Georgia were examined using X-ray radiography of core sections to determine the processes of formation of the deposits. The Tertiary kaolin was oxidized in the upper 3 m of the deposit and reduced below that point. The two Cretaceous kaolins were reduced from the top of the deposit to an abrupt boundary with oxidized red kaolin below. Radiography of the first Cretaceous core revealed thin laminar bedding in the gray kaolin and in the underlying red kaolin. The laminae continue without interruption across the gray kaolin/red kaolin boundary. The laminae were not visible in the gray kaolin except in radiographs. Sedimentary bedding was not observed visually or radiographically at the Tertiary site nor in sections of the core from the second Cretaceous site where kaolinite was recrystallized to large vermiforms. The original sedimentary structure in the first Cretaceous kaolin was preserved possibly due to the inhibition of kaolinite recrystallization by a higher organic matter content. Recrystallization of kaolinite and iron compounds may have destroyed sedimentary structures in part or all of the other two kaolin cores. It is hypothesized that the first Cretaceous physical and biological mixing. The same hypothesis may apply to the other two kaolins but recrystallization after deposition has destroyed sedimentary structures.

The dehydration and migration of the interlayer cation of the synthetic beidellite Na0.7Al4.7Si7.3O20-(OH)4·nH2O, were studied with solid-state 23Na and 27Al MAS-NMR, heating stage XRD, and thermogravimetric analyses (TGA, DTA). The 23Na MAS-NMR of Na-beidellite at 25°C displays a chemical shift of 0.2 ppm, which indicates a configuration comparable with that of Na+ in solution. Total dehydration proceeds reversibly in two temperature ranges. Four water molecules per Na+ are gradually removed from 25° to 85°C. As a result, the basal spacing decreases from 12.54 Å to 9.98 Å and the Na+ surrounded by the two remaining water molecules is relocated in the hexagonal cavities of the tetrahedral sheet. The chemical shift of 1.5 ppm exhibited after the first dehydration stage illustrates the increased influence of the tetrahedral sheet. The high local symmetry is maintained throughout the entire first dehydration stage. During the second dehydration, which proceeds in a narrow temperature range around 400°C, the remaining two water molecules are removed reversibly without any change of the basal spacing.

A critical demand in environmental modeling and a desirable but elusive goal of research on the ion exchange properties of the charged solid surface has been to determine the selectivity coefficient from fundamental properties of the ions and surface. We developed a Hard and Soft Acid and Base (HSAB) Model to describe exchangeable cation selectivity on solid surfaces. Our previous work has shown that the model quantitatively describes alkali cation exchange on clay minerals in terms of the absolute electronegativity and softness of the exchangeable cations and two fitting parameters: α and β. This study was conducted to determine the relationship between α and β and surface charge characteristics of 2:1 clays. The layer charge and cation selectivity of seven smectites and one vermiculite were used. The regression of log Kvo against four combinations of charge properties was performed and the appropriate relationship between α, β, and surface charge was selected based on both statistical criteria (R2) and their consistency with the assumptions of the HSAB model. The selected model was then cross-validated using separate cation exchange data from the literature. It was found that α and β are linearly related to the amount of charge arising from mineral tetrahedral and octahedral sites, respectively. These results make it possible to predict the alkali cation selectivity of 2:1 clay minerals from their chemical composition data and the alkali cation properties.

A synergistic effect of reductant and complexant is observed in the dissolution of goethite by dithionite and citrate or EDTA. The rate data are interpreted using the surface complexation approach to describe the interface of the reacting oxide. Adsorption of both S2O42− (D) and complexant (L) generates three surface complexes that define the dissolution behavior: ≡ Fe-D, ≡ Fe-L, and dimeric surface complexes. The initial rate increases at lower pH values because of increased surface complexation conditional formation constants. At pH values below 4, however, the fast decomposition of S2O42− gives rise to a rapid depletion of reductant, and total dissolution is not observed. It is shown that for best analytical results in soil analysis, EDTA is a better complexant than citrate; the iron extracted in one dithionite-EDTA treatment at pH 5–6, under N2 at 315 K is not increased by increasing the number of extractions, and is equivalent to the total extractable iron found by previous procedures.

The sedimentation behavior of a fine kaolinite, comprising a substantial proportion of colloidal particles as well as non-colloidal ones, has been studied when fresh FeCl3 or F2(SO4)3 electrolytes are added. The sedimentation behavior depends on the pH and the nature of electrolytes and can be explained qualitatively, in our study, by the theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO theory). Fe helps also to aggregate the kaolinite particles in flocs. Two extreme kinds of qualitative sedimentation have been observed: flocculation-sedimentation and accumulation-sedimentation. However, the transition between the two kinds of sedimentation is quite progressive. The present results are discussed in reference to the DLVO theory and the hydrolysis behavior of Fe electrolytes.

X-ray photoelectron spectroscopy (XPS) has been used to characterize the bonding state of Cu2+, Si4+, Al3+, and O2− ions in structural (octahedral and interlamellar) or adsorbed position in phyllosilicates. Five smectites, 5 kaolinites, and 1 chrysocolla with Cu(II) in known positions (octahedral, interlamellar, or surface adsorbed) have been investigated. Their spectra were compared with those of pure Cu metal and of pure Cu(I) and Cu(II) oxides.

The line for Cu 2p3/2 (binding energy of 935.4 eV) and well-defined shake-up lines (binding energy of about 943 eV) observed after 1 hr of X-ray irradiation are characteristic of Cu(II) in phyllosilicate octahedral sites. But due to the photoreduction effect, they show Cu(I) oxidation states (Cu 2p3/2, binding energy of 933.2 eV and near absence of shake-up lines) for the phyllosilicates with adsorbed Cu or in interlamellar positions. The kinetics of photoreduction distinguishes octahedral from interlamellar positions, and the latter from a surface adsorbed position. The enlargement of the FWHM (full width at half maximum) of XPS lines has been used to describe crystallochemical parameters linked to local ordering around the probe cations. Crystallization produces decreasing O 1 s and Cu 2p (octahedral cation) line widths but has no effect on the Si 2p (tetrahedral cation) line width. The enlargement of FWHM for all ion lines of the lattice is linked to the nature (Cu > Mg > Al) and the number and amount of structural cations in the phyllosilicates.

Color variations from brown to yellow of synthesized goethite have been studied colorimetrically and spectroscopically. Goethite with various colors was synthesized at pH 13 and 40°C by varying the incubation time. Colorimetry revealed that the b* value (yellowish chroma) in L*a*b* color space was a quantitative indicator of color variations of the diluted samples. From UV-VIS-NIR spectra, the increase in the b* value was found to be caused by the increase in crystal field absorptions due to goethite formation around 500 nm. The b* value was a good indicator of the relative proportion of goethite in the precipitates including ferrihydrite. X-ray diffraction patterns and infrared spectra revealed that crystallization of goethite was associated with loss of water from the proto-ferrihydrite.

Evidence of chlorite weathering to halloysite appears to be limited. Trioctahedral ferruginous chlorite occurring in granitic rocks and in situ altered phases isolated from the horizons of two soils in southern Korea were studied by scanning and transmission electron microscope (SEM, TEM), chemical, and X-ray diffraction (XRD) techniques to determine the mechanism of alteration and nature of alteration products. Chlorites were entirely converted to halloysite, kaolinite, and Fe-oxyhydroxides in the thick Bt horizon. In the E and BC horizons, in addition to 1:1 silicate clays and Fe-oxyhydroxides, chlorite-like and intergradient vermiculite-kaolin minerals were also found. Total chemical analysis of chlorite flakes revealed losses of substantial amounts of Fe and Mg. Large parallel sets of galleries suggested extensive exfoliation and expansion of chlorite flakes. Tubular halloysite formed bridges between the walls of galleries. The SEM and TEM analyses showed very distinct coatings (0.2–0.3 μm thick) of Fe-oxyhydroxides above and below the surface of galleries that consisted of rounded, sub-rounded, elongated, ultramicrocrystalline particles (goethite and hematite). The 1:1 mineral species found in the thick Bt horizon had a tubular and crumpled lamellar morphology. The presence of Fe likely creates a misfit between tetrahedral and octahedral sheets and results in the morphology of the 1:1 clays observed under SEM and TEM. The presence of intergradient minerals between chlorite and 1:1-type clays in the surface and transitional BC horizon suggests that, in addition to losses of OH sheet -Fe and -Mg, the chlorite with mostly Al-octahedra is partly transformed to double 1:1 silicate clays and intergradient minerals.