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Showing papers in "Clays and Clay Minerals in 1982"


Journal ArticleDOI
TL;DR: The adsorption of uncharged polymers by clays is largely "entropy-driven" as discussed by the authors, where polymer confor- mation changes from a random coil in solution to an extended form at the surface in which adsorbed polymer segments or trains alternate with loops and tails extending away from the surface.
Abstract: The adsorption of uncharged polymers by clays is largely "entropy-driven." Polymer confor- mation changes from a random coil in solution to an extended form at the surface in which adsorbed polymer segments or trains alternate with loops and tails extending away from the surface. Although the net inter- action energy, e, per segment-surface contact is small (--1 kT unit), the total energy of adsorption is large because the fraction of train segments, p, is commonly between 0.3 and 0.5. The adsorption isotherms are typically of the high-affinity type, and there is an apparent lack of desorption on dilution. Positively charged polymers (polycations) are adsorbed largely through electrostatic interactions between the cationic groups of the polymer and the negatively charged sites at the clay surface. Here e >> 1 kT unit and p > 0.7, leading to an almost complete collapse of the polymer chain onto the surface. Indeed, beyond a given level of adsorption charge reversal can occur in that the clay-polycation system effectively behaves as an anion exchanger. Little adsorption occurs with negatively charged polymers (polyanions) due to initial charge repulsion between the polymer and the clay surface. Acid pH, a high ionic strength, and the presence of polyvalent cations in the system enhance and promote polyanion adsorption. Uncharged polymers and polycations can enter the interlayer space of expanding 2:1 type layer silicates but polyanions generally fail to intercalate. The interactions of clays with biopolymers, such as proteins, nucleic acids, and polysaccharides, can be rationalized in similar terms. When intercalation occurs, the interlayer biopolymer is further stabilized against microbial (enzymatic) degradation giving rise to practical applications of clay-polymer complexes as flocculants and soil conditioners. Polyanions are effective as flocculants because of their large "grappling distance," whereas uncharged polymers are better suited as soil conditioners because they can spread over adjacent clay/soil particle surfaces like a coat of paint.

411 citations


Journal ArticleDOI
TL;DR: The boiling 5-M-NaOH treatment was found to aid in the identification and characterization of goethite and hematite by effectively concentrating the two Fe oxides in kaolinitic-gibbsitic soil clays as discussed by the authors.
Abstract: The boiling 5-M-NaOH treatment was found to aid in the identification and characterization of goethite and hematite by effectively concentrating the two Fe oxides in kaolinitic-gibbsitic soil clays. No transformations of goethite to hematite or hematite to goethite were detected, but poorly crystalline, highly Al-substituted goethite was found to dissolve and recrystallize into a more well-crystalline, less Al-substituted goethite in samples low in Si. The Si released from kaolinite was sufficient to block goethite dissolution and recrystallization in kaolinitic samples, but noncrystalline silica had to be added to samples rich in gibbsite to minimize this effect.

216 citations


Journal ArticleDOI
TL;DR: In this article, the authors compared experimental basal spacings with dL/n-plots to determine the average charge density of 25 vermiculites and found that the high-charged vermicules (≥ 0.8 eq/(Si,Al)4O10) with paraffin-type interlayers follow a straight line in the dL /n plots.
Abstract: The broad charge heterogeneity typical of nearly all smectites is not necessarily characteristic of vermiculites. In addition to vermiculites with pronounced heterogeneity, minerals with no or only limited charge heterogeneities are known. Layer charge and charge heterogeneity of 25 vermiculites were determined by alkylammonium ion exchange. The comparison of experimental basal spacings with dL/n-plots provided a simple determination of the average charge density. The spacings of high-charged vermiculites (≥0.8 eq/(Si,Al)4O10) with paraffin-type interlayers follow a straight line in the dL/n-plots. Lower-charged vermiculites were recognized by stepwise increasing spacings due to mono-, two-, or three-layer chain packings. Charge heterogeneity produced a superposition of the dL/n-curves for different charges, and the basal reflections of some of the alkylammonium derivatives became nonintegral.

183 citations


Journal ArticleDOI
TL;DR: In this paper, the adsorption of allophane, imogolite, and halloysite has been studied in relation to the surface structure of the mineral samples.
Abstract: The adsorption of sodium, chloride, and phosphate ions by allophane, imogolite, and halloysite has been studied in relation to the surface structure of the mineral samples. The high adsorption of phos- phate (>200/zmole/g) and chloride (10-30 meq/100 g at pH 4) by allophane is ascribed to the small particle size of allophane, its high surface area (-800 m2/g), and the presence at the surface of A1-OH-A1 groups and defect sites. In contrast, halloysite has a relatively large particle size and a Si-O-Si surface. Accord- ingly, the adsorption of phosphate (5-10/xmole/g) and chloride (1 meq/100 g) by halloysite is very much lower as compared with allophane. Phosphate adsorption by halloysite is also related to particle mor- phology and the number of edge sites. Thus, a sample consisting entirely of spheroidal particles adsorbed only 5/xmole/g at a solution concentration of 1  10 4 M, whereas the tubular types of comparable surface area adsorbed 7-10/zmole/g at the same concentration. This is because spheroidal halloysite particles have few, if any, edge sites at which phosphate can adsorb. The relative degree of order and hydration of hal- loysite, as indicated by infrared spectroscopy, also affects phosphate adsorption. However, this factor is apparently less important than particle morphology and surface structure. Although imogolite also has an A1-OH-A1 surface, it contains relatively few defect sites where phosphate can adsorb. Consequently, much less phosphate (120/zmole/g) was adsorbed as compared with allophane.

180 citations


Journal ArticleDOI
TL;DR: In this paper, a layered double hydroxide with a chemical composition (A12Li(OH)6)+X �9 nH20, where X is an interlayer anion, has been synthesized hydrothermally at 130~ from aluminum-tri-(sec-butoxide) and lith- ium carbonate.
Abstract: A layered double hydroxide with a chemical composition (A12Li(OH)6)+X �9 nH20, where X is an interlayer anion, has been synthesized hydrothermally at 130~ from aluminum-tri-(sec-butoxide) and lith- ium carbonate. Electron micrographs showed the product to have a platy morphology with distinct hex- agonal symmetry, which has been corroborated by selected area electron diffraction patterns corresponding to a projection of the structure on its (001) plane. Evidence for a superlattice with a = 5.32/~ was obtained, indicating cation ordering among octahedral sites. X-ray powder diffraction data also can be interpreted by reference to a hexagonal supercell with dimensions a = 5.32/~ and c = 15.24/~. The arrangement of the octahedral sites appears to be that of gibbsite, but with the vacancies filled with lithium cations. Anions must be present between the sheets to balance the charge. A complete assignment of the observed infrared lattice vibrations can be made for the anion (AlzLiOt) with the ideal D3d symmetry for motions within one octahedral sheet. The results show that (A12Li(OH)tl+X -- nH20 is a hydrotalcite-like compound with the octahedral cations largely ordered. The general formula for hydrotalcite-like compounds, (M2+i_xM3+x(OH)2)x+xm-x/m. nH20, should be extended to include the monovalent lithium cation.

173 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that the bonding behavior of oxyanions with freshly precipitated hydrous ferric oxides depends upon the nature of the anion and its hydration level, and the symmetry of the free anion has a significant role in determining the configuration of the resultant complex.
Abstract: Infrared analysis showed that the bonding habit of oxyanions with freshly precipitated hydrous ferric oxides depends upon the nature of the anion and its hydration level. Monovalent oxyanions adsorb through an electrostatic interaction with the hydrated hydrous oxide surface. All divalent oxyanions, with the exception of tellurate, coordinate directly with surface iron cations. Tellurate, an octahedral anion, apparently penetrates and incorporates in the hydrous oxide structure. The symmetry of the free anion has a significant role in determining the configuration of the resultant complex. For anions of the same charge, those with tetrahedral geometry (in uncoordinated states) show a higher degree of specificity for the surface than the trigonal planer anions. Without exception, each bidentate bridging complex forms by replacement of protonated and unprotonated hydroxyls. With the anion geometry and the charge being equal, the sus- pension pH determines the adsorption capacity of the hydrous oxide.

160 citations


Journal ArticleDOI
TL;DR: In this article, the viscosity and light-transmission measurements of dilute suspensions of montmorillonites having different exchangeable cations were used to calculate relative particle sizes as a function of cation com- position.
Abstract: Viscosity and light-transmission measurements of dilute suspensions of montmorillonites having different exchangeable cations were used to calculate relative particle sizes as a function of cation com- position, where particle size is expressed as the number of clay plates per tactoid relative to the number of plates per tactoid for Li-montmorillonite, after exchange of Li, Na, K, Cs, and Mg by Ca. Tactoid sizes increased in the order Li < Na < K < Mg < Ca, with the number of plates per tactoid relative to Li- montmorillonite varying from 1.5 for Na- to 6.1 for Ca-montmorillonite. The results for tactoid sizes derived from light transmission and those derived from viscosity data are in reasonable agreement with each other and with literature data for similar systems. Upon exchange of Ca-counterions for Li-, Na-, or K-coun- terions, a sharp initial decrease in tactoid size was observed over approximately the first 30% of cation exchange. Upon further exchange, tactoid sizes changed only slightly, but when Ca was exchanged for Cs or Mg, a much more gradual decrease in particle size was observed.

154 citations


Journal ArticleDOI
TL;DR: Berthierine (formerly chamosite) occurs as concretions, lenses, and bands in carbonaceous, kaolinitic shale of freshwater coal-swamp deposits in Paleogene and Upper Triassic coal measures of Japan as discussed by the authors.
Abstract: Berthierine (formerly chamosite) occurs as concretions, lenses, and bands in carbonaceous, kaolinitic shale of freshwater coal-swamp deposits in Paleogene and Upper Triassic coal measures of Japan. Textural relations in thin sections of the Triassic berthierine rocks and a siderite-kaolinite-berthierine-quartz assemblage in Paleogene rocks indicate that the berthierine formed by reaction of siderite with kaolinite. The transformation of siderite and kaolinite to berthierine and quartz occurs progressively under reducing conditions between 65° and 150°C and at burial depths of 2–5 km. Utatsu berthierine is an aluminous, low-Mg variety as compared with berthierine pellets in modern marine and estuarine sediments and in ancient marine ironstones. Fe is the dominant octahedral cation with Fe2+ ≫ Fe3+. The composition of the berthierine varies between different morphological types. Utatsu berthierine transformed to ferrous chamosite when kaolinite in the host shale changed to pyrophyllite. These transformations are estimated to have occurred at ∼160°C and at a burial depth of ∼3 km.

105 citations



Journal ArticleDOI
TL;DR: In this paper, a part or all of Si was substituted with Ge, and associated changes appeared in the X-ray powder diffraction patterns, suggesting that the substitution of Ge for Si caused a decrease in the curvature of the gibbsite sheet with which SiO- or GeO-tetrahedra are associated.
Abstract: Imogolites in which a part or all of Si was substituted with Ge were synthesized from solutions containing aluminum ion and silicic and/or germanic acid. The products were similar to natural imogolite in their tubular morphology, electron diffraction patterns, and differential thermal analysis curves. However, the external diameter of the tube increased with increasing Ge substitution up to about 33 A, and associated changes appeared in the X-ray powder diffraction patterns, suggesting that the substitution of Ge for Si caused a decrease in the curvature of the gibbsite sheet with which SiO- or GeO-tetrahedra are associated. Infrared absorption bands at 995 and 930 cm−1 in imogolite disappeared and new bands appeared at 910 and 810 cm−1 on substitution of Ge for Si, whereas those in the region between 700 and 300 cm−1 remained unchanged or changed little. The former two bands were assigned to Si-O vibrations and the latter bands to Al-O vibrations.

96 citations


Journal ArticleDOI
TL;DR: In the Amargosa Flat and Ash Meadows areas of the Ammarosa Desert as mentioned in this paper, the authors found that the mineral precipitation probably occurred during a pluvial period in shallow lakes or swamps fed by spring water from Paleozoic carbonate aquifers, and that modern spring water in the area can precipitate sepiolite, dolomite, and calcite following only minor evaporative concentration and equilibrium with atmospheric CO2.
Abstract: Deposits of sepiolite, trioctahedral smectite (mixed-layer kerolite/stevensite), calcite, and dolomite, found in the Amargosa Flat and Ash Meadows areas of the Amargosa Desert were formed by precipitation from nonsaline solutions. This mode of origin is indicated by crystal growth patterns, by the low Al content for the deposits, and by the absence of volcanoclastic textures. Evidence for low salinity is found in the isotopic compositions for the minerals, in the lack of abundant soluble salts in the deposits, and in the crystal habits of the dolomite. In addition, calculations show that modern spring water in the area can precipitate sepiolite, dolomite, and calcite following only minor evaporative concentration and equilibration with atmospheric CO2. However, precipitation of mixed-layer kerolite/stevensite may require a more saline environment. Mineral precipitation probably occurred during a pluvial period in shallow lakes or swamps fed by spring water from Paleozoic carbonate aquifers.

Journal ArticleDOI
TL;DR: In this paper, the nature of Cu 2+ adsorption by boehmite, gibbsite, and non-crystalline alumina was studied over a range of equilibrium pH (4.5-7.5) and Cu 2 § concentration (10 a-10 -8 M) by electron spin resonance (ESR).
Abstract: The nature of Cu 2+ adsorption by boehmite, gibbsite, and noncrystalline alumina was studied over a range of equilibrium pH (4.5-7.5) and Cu 2§ concentration (10 a-10 -8 M) by electron spin resonance (ESR). Available chemisorption sites at pH 4.5 were the most numerous for noncrystalline alumina (-1 mmole/100 g), less for boehmite, and least for gibbsite as indicated by the relative strength of the rigid-limit ESR signal attributed to Cu z+ adsorbed at discrete sites. The chemisorption process involved immobili- zation of Cu 2+ by displacement of one or more H20 ligands by hydroxyl or surface oxygen ions, with the formation of at least one Cu-O-AI bond. As the pH was raised from 4.5 to 6.0, essentially all of the solution Cu 2+ appeared to be adsorbed by the solids. However, the noncrystalline alumina and boehmite chemi- sorbed much of the total adsorbed Cu 2+ (10 mmole/100 g), whereas precipitation or nucleation of Cu(OH)~ in the gibbsite system was indicated. Precipitated Cu z+ was more readily redissolved by exposure to NH3 vapor than chemisorbed Cu 2+.

Journal ArticleDOI
TL;DR: The diffusion of exchanged Yb, Ho, and Eu from interlayer positions in montmorillonite was studied using infrared spectroscopy (IR), X-ray powder diffraction, and cation-exchange measurements.
Abstract: The diffusion of exchanged Yb, Ho, and Eu from interlayer positions in montmorillonite was studied using infrared spectroscopy (IR), X-ray powder diffraction, and cation-exchange measurements. Dehydration of exchanged montmorillonite between 100° and 280°C caused the ions to diffuse into the hexagonal rings of surface oxygens. Subsequent migration into vacant octahedral sites was small regardless of the radius of the cation. Considerable ion fixation in excess of the cation-exchange capacity of the clay was observed at 20°C in both water and a 1:1 water:95% ethanol mixture. Evidence for hydrolysis as a possible mechanism for cation fixation was obtained by observing frequency shifts for deuterated hydroxyl groups using IR spectroscopy. A major IR band centered at 2680 cm−1 was observed for all three lanthanide-exchanged montmorillonites studied and assigned to the OH-stretching frequency of a lanthanide hydroxide. This band intensified on heating at 300°C for 1 hr. An IR band between 690 and 710 cm−1 also was observed for all three lanthanide-exchanged montmorillonites and was assigned to a lanthanide-hydroxyl deformation mode. No hydrolysis was observed for Na-montmorillonite, as expected from the very low hydration energy of Na+.

Journal ArticleDOI
TL;DR: In this article, the effects of exchangeable Na and Ca and the ionic strength of NaC1 and CaC12 solutions on the boron adsorption by the Na and the Ca forms of montmorillonite and illite at pH 9 were studied.
Abstract: The effects of exchangeable Na and Ca and the ionic strength of NaC1 and CaC12 solutions on the boron adsorption by the Na and Ca forms of montmorillonite and illite at pH 9 were studied. The boron adsorption by montmorillonite was greater for the Ca form than for the Na form at any boron activity in solution and at any ionic strength. For example, the amount of boron adsorbed by Na- and Ca-montmo- rillonite was 2.9 and 4.3/zmole/g, respectively, at an ionic strength of 0.36 and a boron activity of 0.875 mmole/liter in equilibrium solution. The boron adsorption by illite was much greater than by montmoril- lonite. For example, the amount of boron adsorbed by Na-montmorillonite and Na-illite was 1.5 and 8.7 /zmole/g, respectively, at an ionic strength of 0.02 and a boron activity of 0.5 mmole/liter. However, the nature of the exchangeable cation had little effect on the boron adsorption by illite. The effect of the ionic strength on the boron adsorption by Na-montmorillonite was greater than that observed for either Ca- montmorillonite or illite. The data suggest that the negative electric field around the clay particles is one of the main factors controlling boron adsorption at alkaline pHs.

Journal ArticleDOI
TL;DR: In this paper, the authors used computer-simulated X-ray diffractograms to determine the percentage of expandable layers of mixed-layer clays composed of randomly interstratified kerolite/stevensite.
Abstract: Mixed-layer clays composed of randomly interstratified kerolite/stevensite occur as lake and/or spring deposits of probable Pliocene and Pleistocene age in the Amargosa Desert of southern Nevada, U.S.A. The percentage of expandable layers of these clays, determined from computer-simulated X-ray diffractograms, ranges from almost 0 to about 80%. This range in expandabilities most likely results from differences in solution chemistry and/or temperature at the time of formation. An average structural formula for the purest clay (sample P-7), a clay with about 70% expandable layers, is: $${\left[ {\left( {M{g_{2,72}}A{l_{0,07}}F{e_{0.03}}L{i_{0.09}}} \right)\left( {S{i_{3.96}}A{l_{0.04}}} \right){O_{10}}{{\left( {OH} \right)}_2}} \right]^{ - 0.21}}{\left[ {X_{0.21}^ + } \right]^{ + 0.21}}.$$

Journal ArticleDOI
TL;DR: Ferrihydrite prepared in different manners was kept under relative humidities ranging from 75 to 100% and at temperatures of 45° and 55°C for 180 days.
Abstract: Ferrihydrite prepared in different manners was kept under relative humidities ranging from 75 to 100% and at temperatures of 45° and 55°C for 180 days. Ferrihydrite transformed to hematite and goethite at relative humidities close to 100%, but at lower relative humidities the transformation was less pronounced and hematite was highly favored over goethite. Increasing temperature also favored hematite over goethite, and Al substitution completely prevented goethite formation. These results suggest that hematite can form in relatively dry, warm soils or sediments, although more slowly than in moister environments.

Journal ArticleDOI
TL;DR: In this paper, the authors describe the transformation of orthopyroxene to talc plus oxides through three sequential mineral reactions without the development of a non-crystalline phase.
Abstract: Orthopyroxene (En85) weathers initially by vacancy diffusion, and through this process hydration occurs and a sequence of biopyriboles develops, culminating in a talc-like layer silicate whose structure joins coherently to the orthopyroxene structure. Oxidation of Fe2+ to Fe3+ colors the altering pyroxene yellow. The ‘talc’ does not remain in structural coherence with the pyroxene after it has exceeded a few tens of nanometers in size; it is replaced by a mixture of talc and smectite. In some areas the mixture has an epitactic relation to the pyroxene, but commonly it fills faceted solution holes without crystallographic relation to the parent structure. Continued weathering extends the yellow zone at the periphery of the orthopyroxene, and the alteration product increases in smectite and decreases in ’talc’ During this stage of the reaction, MgO and SiO2 are released to form colorless true talc around the altering pyroxene. Eventually, the yellow alteration may become a smectite pseudomorph after orthopyroxene or it may be changed entirely to a mixture of vein talc and iron oxides. The complete conversion of orthopyroxene to talc plus oxides thus takes place through three sequential mineral reactions without the development of a noncrystalline phase. kw]Key Words—Biopyribole, Enstatite, Smectite, Talc, Transmission electron microscopy, Weathering.


Journal ArticleDOI
TL;DR: In this article, chemical compositions of coexisting biotite and chlorite determined by electron microprobe and wet chemical methods were used to evaluate chemical mass transfer during the alteration process.
Abstract: Abstraet~Hydrothermal chlorite replaces igneous biotite in the Gold Hill, Utah, quartz monzonite. Chemical compositions of coexisting biotite and chlorite determined by electron microprobe and wet chemical methods were used to evaluate chemical mass transfer during the alteration process, The mole ratio Mg/ (Mg + Fe) varies from 0.52 to 0.65 in the chlorite and from 0.51 to 0.60 in the parent biotite. The Mg content of the chlorite decreases systematically with increase in the volume percent replacement of biotite. Homogenization temperatures of fluid inclusions in nearby quartz microveinlets indicate that the chloritic alteration took place at approximately 200~ Textural relationships suggest that the alteration of biotite to chlorite is isovolumetric, but a comparison of mineral compositions and mineral assemblages with phase diagrams in which A1 or volume are conserved among solid phases suggests that the chlorite cq_mpositions are bes ~ explained:as a f!anciio~_~f~reaction progress in an Al-conservative s~stem. The chlorite composition changes in response to changes in solution ~omposition produced by the dissolution of successive small amounts of biotite. Representative mass balance for the alteration of all of the biotite to chlorite in 1 m 3 of rock containing 336 moles of biotite indicates that 74 moles of Mg, 35 moles of Fe 3+, 420 moles of H +, and 2 moles of Mn are added to the rock and that 311 moles of K, 54 moles of Fe 2+, 76 moles of Ti, 53 moles ofF, and 6 moles of C1 are lost to solution. The mass transfer for partially altered biotite is ll to 188 moles of K, 2 to 46 moles ofTi, 2 to 44 moles ofF, and 0.3 to 6 moles of C1 removed per cubic meter of rock and 1 to 26 moles of Fe 3§ and 20 to 347 moles of H + added. The mass transfer of Mg varies from 12 moles added to 32 moles removed per cubic meter of rock depending on mineral composition and extent of replacement.

Journal ArticleDOI
TL;DR: In this paper, the acid-catalyzed reaction between methanol and isobutene to give methyl-t-butyl ether was carried out using a cation-exchanged smectite as the catalyst.
Abstract: The acid-catalyzed reaction between methanol and isobutene to give methyl-t-butyl ether may be carried out using a cation-exchanged smectite as the catalyst. In 1,4-dioxan solvent at 60°C smectites exchanged with Al3+, Fe3+, or Cr3+ give yields of ∼60% after 4 hr, whereas smectites exchanged with Cu2+, Pb2+, Ni2+, Co2+, Ca2+, and Na+ give less than ∼8% yield. The reaction is efficient only when certain solvents are used, e.g., with Al3+-smectite the yield is ∼5% when using 1,2-dimethoxyethane, diethyleneglycol diethylether, n-pentane, tetrahydropyran, N-methylmorpholine, or tetrahydrofuran solvents compared with ∼60% using 1,4-dioxan solvent (4 hr). Moreover, the effective solvents depend somewhat on the clay interlayer cation. The use of tetrahydrofuran and tetrahydropyran gives ∼35% yields at 60°C (4 hr) with Fe3+- or Cr3+-smectites but ∼4% yield with Al3+-smectite.

Journal ArticleDOI
TL;DR: In this article, a survey of more than 150 different shale horizons indicates that the NH4+ content of the illites increases in proximity to the stratiform base metal mineralization.
Abstract: Naturally occurring ammonium illites have been discovered in black shales surrounding a stratiform base metal deposit in the DeLong Mountains, northern Alaska. Infrared spectra of the samples exhibit pronounced absorption at 1430 cm−1, the resonant-banding frequency for NH4+ coordinated in the illite interlayer. X-ray powder diffraction characteristics of the ammonium illites include an expanded d(001) spacing, with values as large as 10.16 A, and ratios for I001/I003 and I002/I005 of about 2. Infrared analyses of physical mixtures of NH4Cl with a standard illite, and comparisons with synthetic ammonium micas indicate significant substitution (>50%) of NH4+ for K+ in the illite interlayer position. Nitrogen determinations on two ammonium illites after removal of carbonaceous matter gave values of 1.48 wt. % NH4+ and 1.44 wt. % NH4+. A survey of more than 150 different shale horizons indicates that the NH4+ content of the illites increases in proximity to the stratiform base metal mineralization.

Journal ArticleDOI
TL;DR: The upper Pliocene sediments near Lebrija in southern Spain contain commercial deposits of palygorskite and sepiolite as mentioned in this paper, which are used to clarify and purify wine.
Abstract: The Upper Pliocene sediments near Lebrija in southern Spain contain commercial deposits of palygorskite and sepiolite. These sediments of continental origin consist chiefly of carbonate, marl, and clay resting on marine Pliocene quartzose sand. The lowest unit, the "Marly-Calcareous Bed," consists of sepiolite-rich marl associated with concretions and irregular layers of chert, <0.5 m thick, and local diatomite layers, as well as limestone, sandy limestone, marl, and clayey sandstones. This unit has a max- imum thickness of 30 m and contains three clay-mineral suites as follows: (1) bottom--sepiolite ___ paly- gorskite; (2) center--sepiolite and palygorskite _+ illite; (3) top--palygorskite and illite, _+ sepiolite and smectite. Sepiolite decreases and palygorskite and illite increase toward the top, reflecting the composition of detrital material supplied to the basin. Beds 0.5-1 m thick locally and containing 50 to 60% sepiolite have been called "Tierra del Vino" (wine earth) because the material formerly was used to clarify and purify wine. The sepiolite-rich beds are as much as 15 m thick in the eastern part of the area. The upper unit is called the "Palygorskite Bed" because certain layers, 0.3 to 3 m thick, contain 35 to 75% palygorskite. The palygorskite-rich layers are interbedded with limestone and marl, and the entire unit is 15 m thick. The total resource of palygorskite is estimated at about 9 million tonnes. The sediments are believed to have been deposited in a brackish, lacustrine environment. Originally, tectonic stability and an arid climate favored the formation of sepiolite at about pH 8. Later, after significant weathering of the source rocks, detrital illite was transformed to palygorskite in the Mg- and Si-rich waters. Here, palygorskite was also precipitated directly.


Journal ArticleDOI
TL;DR: In this paper, an electrostatic model for the stability of clay tactoids (stacks of parallel clay platelets at -10 A separation) in an aqueous solution has been developed.
Abstract: An electrostatic model for the stability of clay tactoids (stacks of parallel clay platelets at - 10 A separation) in an aqueous solution has been developed. The counter ions located in the interstitial water layers are assumed to be in equilibrium with the bulk solution. Generally, the counter-ion charge density is slightly different in magnitude from the platelet charge density. Approximating the discrete charges by homogeneously charged planes, a one-dimensional potential distribution can be calculated. From this the Gibbs energy of electrostatic interaction (using single platelets as a reference) can be computed. The model predicts that clay minerals with high (vermiculite, mica) and low (pyrophyllite, talc) degrees of cationic substitution form stable tactoids. For smectites, charge density, electrolyte concentration, and counter- ion species determine the swelling characteristics. At a particular charge density, lower valences of the counter ions and lower electrolyte concentrations lead to increased swelling. If tactoids are formed, the number of platelets is governed by a dynamic equilibrium between electrostatic forces, van der Waals forces, and external forces, such as shear forces due to hydrodynamic flow.

Journal ArticleDOI
TL;DR: In this paper, electron spin resonance (ESR) analysis of Cu2+-hectorite suspensions provides evidence for surface-induced hydrolysis of Cu(H2O)62+ at low pH and surface-inhibited hydrolyisation (or precipitation) at high pH.
Abstract: Electron spin resonance (ESR) analysis of Cu2+-hectorite suspensions provides evidence for the surface-induced hydrolysis of Cu(H2O)62+ at low pH and surface-inhibited hydrolysis (or precipitation) at high pH. Dehydration of the hectorite by heating to 110°C appears to promote hydrolysis in high pH clays further. Heating to even higher temperatures removes ligand water from Cu2+, allowing the metal ion to coordinate with silicate oxygen atoms. The planar Cu(H2O)42+ ion predominates in the interlamellar regions of hectorite that has been air dried or heated to temperatures of 110°C or lower, but more extreme thermal treatment changes the apparent orientation of the Cu2+-ligand axes as some or all of the four water ligands are removed, A loss in ESR signal intensity upon heating Cu2+-hectorite above 110°C is evidence for lowered symmetry of the dehydrated, surface-coordinated Cu2+ ion.

Journal ArticleDOI
TL;DR: In this paper, the authors show that underclay in southwestern Illinois has undergone in situ alteration due to the downward movement of hydrogen ions, as indicated by the progressive leaching of acid-sensitive minerals adjacent to the coal.
Abstract: Regular 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 US with respect to randomly interstratified US; (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 US 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.

Journal ArticleDOI
TL;DR: In this article, an iron-rich chlorite, ripidolite, was oxidized by air-heating at 480°F and subsequently reduced in hydrogen at the same temperature.
Abstract: An iron-rich chlorite, ripidolite, was oxidized by air-heating at 480~ i.e., below the dehydrox- ylation temperature and subsequently reduced in hydrogen at the same temperature. On the basis of chem- ical, differential thermal, infrared, MSssbauer, and X-ray powder diffraction analyses, Fe(II) seems to be present only in the 2:1 layer of the original chlorite in a type of site similar to that of Fe(II) in biotite, with OH in cis-positions. These data also suggest that octahedral A1 and Fe(III) are located in the hydroxide sheet of the original chlorite. The structural changes of the mineral due to the oxidation and the subsequent reduction appear limited to minor structural rearrangements and, perhaps, to the introduction of OH in both cis- and trans-positions. The results of the investigation are in agreement with a reaction of the form: (Fe(II)OH) + --~ (Fe(III)O) + + H(H + + e-).

Journal ArticleDOI
TL;DR: In this article, electron probe analyses of diagenetic illites in Eocene sandstones from Kettleman North Dome, California, along with analyses of coexisting interstitial waters were used to calculate apparent molal free energies of formation of the illites at the in situ conditions of 100°C and 150 bars.
Abstract: Electron probe analyses of diagenetic illites in Eocene sandstones from Kettleman North Dome, California, along with analyses of coexisting interstitial waters were used to calculate apparent molal free energies of formation of the illites at the in situ conditions of 100°C and 150 bars. Various triangular and rectangular compositional plots, once contoured for free energy, crudely indicate that the free energy decreases as the potassium content increases, decreases as the Al-for-Si substitution increases, and appears to be a minimum along a narrow composition valley having ~3% Fe2O3 of octahedral cations. Qualitatively, the shape of the free energy surface suggests only small departures from ideality.

Journal ArticleDOI
TL;DR: In this paper, the authors used the integral series of 00ℓ reflections in ethylene glycol-treated samples of air-fall tephra from several 1980 eruptions of Mount St. Helens.
Abstract: Phyllosilicates are major components of the <2-µm fraction (1–3 wt. % of most bulk specimens) in more than 50 samples of air-fall tephra from several 1980 eruptions of Mount St. Helens. In all samples, trioctahedral smectite is the major clay mineral. The integral series of 00ℓ reflections in ethylene glycol-treated samples indicates a lack of interstratification; absence of a peak near 5 Å after heat treatment, the 060 peak at 1.54 Å, and energy dispersive chemical analyses indicate that the smectite is a Mg- and Fe- rich, trioctahedral saponite. Minor mica and chlorite are present in the <2-µm fraction of most samples, and some samples show a peak near 12 Å after heating to 550°C which is probably due to the presence of an interstratifled chlorite/collapsed smectite or chlorite/collapsed vermiculite. The tephra contains glass and crystals originating from new magma and lithic fragments incorporated from the pre-existing cone. The clay minerals in the tephra are lithic components stripped from older, hydrothermally altered rocks during explosive ejection. Cleaned pumice fragments, which are new magmatic components, lack smectite, but contain rare biotite in xenoliths. Old, hydrothermally altered rocks from the volcano’s summit and from the debris-avalanche (former north flank) contain saponite together with chlorite and chlorite/smectite which may have formed from it. Saponite and zeolites that precipitated from neutral to alkaline hydrothermal solutions line cavities in some of these rocks. The saponite was probably not subjected to magmatic temperatures because heating this material for 5 min at 750°C collapses it irreversibly to 10 Å. Kaolinite, alunite, and opal, indicative of acid-sulfate alteration, were found only in the pre-1980 summit crater and the southwest thermal area, but were not evident in the lithic components of the 1980 deposits.РезюмеФиллосиликаты являются главными компонентами фракции размером <2 μM (1–3 весового % большинства основных типов) в более, чем 50 образцах из воздушно-осадочных тефр, изверженных при нескольких взрывах вулкана Горы Святой Елены в 1980 году. Трехоктаэдрический смектит является главным глинистым минералом во всех образцах. Полная серия отражений 00ℓ образцов после обработки в этиленовом гликоле указывает на отсутствие внутринапластования; отсутствие пика в поблизости 5 А после нагрева и присутствие пика 060 при 1,54 А, а также дисперсный химический анализ указывают на то, что этот смектит является Мg- и Ре-богатым трехоктаэдкическим сапонитом. Незначительные количества слюды и хлорита присутствуют во фракции размером <2 μм в большинстве образцов, и некоторые образцы имеют пик в поблизости 12 А после нагрева до 550°С, что, вероятно, связано с присутствием внутринапластованных хлоритов/опавших смектитов или хлоритов/опавших вермикулитов. Тефра содержит стекло и кристаллы, происходящие из новой магмы и литовых фрагментов из прежде существующего конуса. Глинистые минералы в вулканическом пепеле являются литовыми компонентами отделенными от древнейших пород, гидротермально измененных во время взрывов. Чистые фрагменты пемзы, которые являются новыми матовыми компонентами, не содержат смектит, но содержат редкий биотит в ксенолитах. Древние, гидротермально измененные породы из пика вулкана и из лавин (прежняя северняя сторона) содержат сапонит вместе с хлоритом и хлоритом/смектитом, которые могут образоваться из этих пород. Сапонит и цеолиты, которые осаждались от нейтральных до щелочных гидротермальных растворов залегают щели некоторых из этих пород. Вероятно, сапонит не подвергается магмовым температурам, потому что нагрев этого материала в течение 5 минут при 750°С изменяет его необратимо в 10 А минерал. Каолинит, алюнит, и опал, указывающие на присутствие кислотно-сульфатных изменений, были найдены только в кратере из извержаний перед 1980 годом и в южно-западной термической области, но не присутствовали в литовых компонентах осадков 1980 года. [Е.С.]ResümeePhyllosilikate sind die Hauptbestandteile der Fraktion <2 µm (1–3 Gew.-% der meisten Durchschnittsproben) in den mehr als 50 Tephraproben von mehreren Eruptionen des Mount St. Helens des Jahres 1980. In allen Proben ist ein trioktaedrischer Smektit das häufigste Tonmineral. Die Basis-Reflexe bei mit Äthylenglycol-behandelten Proben deuten darauf hin, daß keine Wechsellagerung vorhanden ist; das Fehlen eines Peaks bei 5 Å nach dem Erhitzen, der 060-Peak bei 1,54 Å und energiedispersive chemische Analysen zeigen, daß der Smektit ein Mg- und Fe-reicher, trioktaedrischer Saponit ist. Geringe Gehalte an Glimmer und Chlorit sind in den Fraktionen <2 µm der meisten Proben vorhanden. Einige Proben zeigen nach dem Erhitzen auf 550°C einen Peak bei 12 Å, der wahrscheinlich von einer Wechsellagerung Chlorit/kontrahierter Smektit oder Chlorit/kontrahierter Vermiculit herrührt. Die Tephraproben enthalten Glas und Kristalle, die vom neuen Magma stammen und Gesteinsbruchstücke die vom vorherigen Vulkankegel stammen. Die Tonminerale in den Tephraproben sind Gesteinsbestandteile, die von alten, hydrothermal veränderten Gesteinen stammen und wäharend des Ausbruches aufgenommen wurden. Frische Bimsfragmente, die neue magmatische Komponenten sind, enthalten keinen Smektit, doch enthalten sie etwas Biotit und Xenolithe. Alte, hydrothermal veränderte Gesteine vom Vulkangipfel und vonder Schuttlawine (ehemalige Nordflanke) enthalten Saponit zusammen mit Chlorit und Chlorit/Smektit, die sich daraus gebildet haben könnten. Saponit und Zeotithe, die aus neutralen bis alkalischen hydrothermalen Lösungen ausgefallen sind, treten in manchen dieser Gesteine als Hohlraumauskleidungen auf. Der Saponit kam wahrscheinlich nicht unter magmatische Temperaturen, da ein Erhitzen dieses Minerals auf 750°C für 5 Minuten zu einer irreversiblen Kontraktion auf 10 Å führt. Kaolinit, Alunit, und Opal, Indikatoren für eine Sulfat-saure Umwandlung, wurden nur im Gipfelkrater von vor 1980 und in den südwestlichen thermalen Gebieten gefunden, traten aber nicht als Gesteinsbestandteile der Ablagerungen von 1980 auf. [U.W.]RésuméDes phyllosilicates sont les composés majeurs de la fraction <2 µm (1–3% par poids de la plupart des échantillons en masse) dans plus de 50 échantillons de tephres tombant de l’air de plusieurs éruptions de 1980 du Mont St. Hélène. Dans tous les échantillons, la smectite trioctaèdrale est le minéral majeur. Les séries intégrales de reflections 00ℓ d’échantillons traités au glycol éthylène indiquent un manque d’interstratification; l’absence d’un sommet près de 5 Å après un traitement à la chaleur, le sommet 060 à 1,54 Å, et des analyses chimiques dispersant l’énergie indiquent que la smectite est une saponite trioctaèdrale riche en Mg et en Fe. Du mica et de la chlorite mineurs sont pérsents dans la fraction <2 µm de la plupart des échantillons, et quelques échantillons montrent un sommet près de 12 Å après échauffement à 550°C, ce qui est probablement dû à la présence d’une chlorite interstratifiée/smectite effondrée ou d’une chlorite/vermiculite effondrée. Les tephres contiennent du verre et des cristaux provenant de magma nouveau et des fragments tithiques incorporés du cone pré-existant. Les minéraux argileux dans les tephres sont des composés lithiques arrachés pendant l’éjection explosive de roches plus anciennes hydrothermalement alterées. Des fragments de pumice nettoyés, qui sont des composées magmatiques nouveaux, manquent de smectite, mais contiennent de la biotite rare dans les xénolithes. D’anciennes roches hydrothermalement alterées du sommet du volcan et de l’avalanche-débris (précédemment la côte nord) contiennent de la saponite ainsi que de la chlorite/smectite qui pourraient s’être formées à partir de cette première. Des saponites et des zéolites qui avaient précipitée de solutions hydrothermales neutres à alkalines recouvrent les cavités de certaines de ces roches. La saponite n’a probablement pas été soumise à des températures magmatiques puisqu’échauffer ce matériau pendant 5 min. à 750°C l’effondre irréversiblement à 10 Å. La kaolinite, l’alunite, l’opale, indiquant une altération sulphate-acide, n’ont été trouvées que dans le cratère pré-1980 et la région thermale du sud-ouest, mais n’étaient pas évidentes dans les composés lithiques des depôts de 1980. [D.J.]

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TL;DR: In this paper, the solubility of four different commercial hydrated aluminas, including a laboratory preparation, was measured at pH 4 from both over-and undersaturation with continuous agitation for 228 days.
Abstract: The solubility of four different gibbsite preparations was measured, including two commercial hydrated aluminas produced by Alcoa, a Fisher ACS-grade Al(OH)3, and a laboratory preparation. The Alcoa samples and the laboratory-prepared sample had been studied previously by other investigators but without using a long-term acid treatment. Scanning electron microscopy showed globular surface material that was removed by a 14-day, 0.1 M HCl treatment. Solubility was determined at pH 4 from both over-and undersaturation with continuous agitation for 228 days. The acid treatment correlated with a decrease in log*Kso[*KSO = (Al3+)/(H+)3] of about 0.5 units. The mean solubility of the three acid-treated commercial gibbsite samples was log*KSO = 7.55 ± 0.055 (*KSO = 3.5 × 107). The solubility of the acid-treated laboratory preparation was log*KSO = 7.86 (*KSO = 7.2 × 107). The greater solubility of the laboratory-prepared gibbsite is attributed to a greater concentration of structural defects in the crystals.