Showing papers in "Clays and Clay Minerals in 1976"

A Mössbauer and I.R. Spectroscopic Study of the Structure of Nontronite

Abstract: Mossbauer and i.r. spectra of a series of nontronites show that Fe3+ and Al3+ are distributed between tetrahedral and octahedral sites. The Mossbauer results have reaffirmed the occupation by Fe3+ of octahedral sites at which these ions are coordinated to pairs of OH groups in both cis and trans configurations. The distribution of Fe3+ between these two sites varies considerably but in all of the nontronites some Fe3+ occurs in the trans site in contrast to the all cis occupancy of the centro-symmetric structure proposed by Mering and Oberlin (1967). In one of the nontronites the distribution of Fe3+ between these two sites approaches that in the ideal non-centrosymmetric structure proposed for montmorillonite.

Interaction of petroleum heavy ends with montmorillonite

Abstract: Adsorption of asphaltenes and resins onto montmorillonite occurs rapidly and to a large extent irreversibly under near-anhydrous laboratory conditions. Factors which influence the adsorption are the exchangeable cation on the clay, the basic nitrogen components of the molecules, and the solvent. As a result of this adsorption, the physical and chemical properties of the clay are drastically altered. The fundamental principles revealed in this study lead to a better understanding of the physical and chemical behavior of clays in petroleum reservoirs.

Reduction and Oxidation of Fe3+ in Dioctahedral Smectites — 1: Reduction with Hydrazine and Dithionite

Abstract: Hydrazine and dithionite, both of which are strong reducing agents, react differently with various dioctahedral smectites. Both the nature of the reducing agent and the structure of the clay affect the course of the reaction. Hydrazine reduces octahedral Fe3+ efficiently if the mineral has a low tetrahedral charge. The reducing action of dithionite does not depend upon the charge. The results obtained by different physical methods of investigation suggest that reduction of iron is associated with protonation of an adjacent OH group. The Fe2+ formed is readily re-oxidised but the structural changes occurring on reduction are reversible only when Al-OH-Fe, but not when Fe-OH-Fe associations are involved. Reaction mechanisms are proposed and changes in the distribution of iron in the octahedral sites are discussed.

Scan electron micrographs of kaolins collected from diverse environments of origin; I

Abstract: Scan electron micrographs (SEM) show the textures of ball clay, plastic refractory clay, flint clay, and of kaolins from Cornwall, U.K., and Brittany, France. The texture of ball clay is a swirl and ragged-flake pattern. Plastic refractory clay shows a transition in texture from ball clay to plastic, semi-plastic, to semi-flint, and flint-clay. Flint-clay texture exhibits a matrix of tiny, compactly interlocked clay grains in which may be interspersed small, tight books and sheaves of kaolinite. The plastic to flint clays are interpreted to be sequential components of the flint-clay facies. In one sense they represent elements in clay diagenesis. Kaolins from the Cornwall district, U.K., and Brittany, France, show more similarity than dissimilarity in texture. Evidence from texture suggests that while hydrothermal action at Cornwall initiated alteration of the granite, the last significant process of kaolinization there was weathering.

Morphology of Zeolites in Sedimentary Rocks by Scanning Electron Microscopy

Abstract: In the nearly 2000 occurrences of zeolites in sedimentary rocks of volcanic origin about 15 zeolite minerals have been identified. The mode of occurrence of six of these, clinoptilolite, erionite, chabazite, phillipsite, analcime, and mordenite, is described, and their morphology is illustrated with scanning electron micrographs.

The Nature of TiO2 in Kaolinite

Abstract: SEM, TEM, and electron probe studies indicate that the anatase in Georgia kaolins, and probably anatase in general, consists of subspherical particles (TiO2 pellets) 0.05–0.1 µm dia. Some pure anatase aggregates may be pseudomorphic after ilmenite and have a tabular shape, but much of the anatase is formed from Ti that occurs as scattered ions in the octahedral sheets of biotite. When removed from the biotite this material forms TiO2 pellets. These pellets can occur as: single pellets; irregular aggregates; layered aggregates; spherical aggregates; mixed aggregates (with kaolinite); coated aggregates (with kaolinite). Physical energy can be used to break TiO2—kaolinite aggregates, separate single TiO2 pellets from kaolinite plates and remove kaolinite coatings from TiO2 aggregates. Al and Si are present in all TiO2 aggregates and the Si—Al ratio is lower in the aggregates than in the kaolinite. An amorphous Si—Al compound may be present and act as a cement. The anatase apparently is formed from Ti that is released from the parent mineral as Ti (OH)4. The Ti (OH)4 precipitates to form an amorphous hydrous oxide gel which dehydrates to form a granular aggregate of small anatase crystals.

Organomineral derivatives obtained by reacting organochlorosilanes with the surface of silicates in organic solvents

Abstract: Stable organomineral derivatives are formed by reaction of organochlorosilanes with certain phyllosilicates. Organosiloxyl functions are grafted on silanol groups present at external mineral sur- faces. Water molecules adsorbed on external mineral surfaces may cause hydrolysis of the reactant organo- silicon products, with liberation of HC1. This, in turn, may react with the silicate: octahedral cations are extracted from the lattice and fresh Si-OH groups, capable of further grafting, are formed on the mineral surface. On the other hand, when difunctional reagents such as methylvinyldichlorosilane are used and if the ratio of adsorbed water to added reactive is adequate, then polymeric species with polysiloxane chains are grafted on the mineral. Because of its high content of silanol groups, sepiolite forms organomineral compounds having a relatively high organic matter content. With chrysotile, the amount of organic matter grafted to the silicate, is considerably smaller, but it increases appreciably if water is added to the reacting products. This is attributed to hydrolysis of the organic reactant and subsequent destruction of external "brucitic" layers by acid attack.

Transformations of Micas in the Process of Kaolinitization of Granites and Gneisses

Abstract: Micas are described from the kaolin type Tertiary weathering crusts formed on granites and gneisses of Lower Silesia, Poland. In the weathering crust, large scale processes of transformation of micas (muscovite, biotite) take place. Weathering of micas is a gradual transformation of their structures by removal of the mobile cations Mg2+ Fe2+ Fe3+ and finally K +. Muscovite transforms into kaolinite through the intergrowths of two phases, mica and kaolinite. A degradation series, muscovite → mica/montmorillonite → montmorillonite → kaolinite also is observed. Biotite passes directly into kaolinite, but at higher concentrations of K and Al one observes the following sequence of biotite degradation: biotite → dioctahedral mica rich in Fe → dioctahedral mica poor in Fe → kaolinite. This process involves the exchange of Mg2+ and then Fe2+ of octahedral layers by Al3+ less mobile under weathering conditions. In the next stage of degradation, K + removal and kaolinite formation takes place. The micas representing different stages of this transformation, dark green, light-green, and silver-white, have been separated and investigated.

Effect of swelling on the infrared absorption spectrum of montmorillonite

Abstract: The i.r. spectra of mixtures of different Na-montmorillonites were determined at several water contents between 2 and 22 g of water/g of montmorillonite. It was found that Si—O absorption is represented by four closely-spaced bands, one of which is pleochroic. The pleochroic band appeared only at higher water contents. All of these bands, excepting that with the highest wave number, shifted in frequency with increasing isomorphous substitution. None of them shifted in frequency with increasing water content. The absorption coefficient for the principal Si—O absorption decreased with increasing isomorphous substitution but increased with increasing water content. Niether isomorphous substitution nor water content appeared to have any significant effect on absorption due to O—H stretching or H—O—H bending in the interlayer water. At a critical water content for each montmorillonite, an abrupt change occurred in the absorption coefficient for the principal Si—O absorption. This change was ascribed to a sudden rearrangement of the particles.

Experimental alteration of a chlorite into a regularly interstratified chlorite-vermiculite by chemical oxidation

Abstract: A IIb orthochlorite (brunsvigite), from the chloritic metabasalt in the Middletown Valley of Maryland, was altered to a regularly interstratified chlorite—vermiculite after four months reaction in saturated bromine water on the steambath. The artificial weathering product resembles the regularly interstratified chlorite—vermiculite in a soil in Adams County, Pennsylvania, that has developed in greenstone similar to the chloritic metabasalt in the Middletown Valley of Maryland. The results of this and previous investigations on artificial and natural weathering of chlorites indicate that oxidation of structural Fe2+ is an important reaction in the alteration of chlorites into vermiculitic products. The results also show that IIb orthochlorites, apparently structurally similar but having different Fe2+ contents may react differently under the same weathering conditions. For example the acid oxidation treatment altered a IIb chlorite (diabantite) directly into a vermiculite, whereas the same treatment altered another IIb chlorite (brunsvigite) into a regularly interstratified chlorite—vermiculite. Detailed investigations of the chlorite structures are probably necessary to determine whether or not these alteration processes are structurally controlled.

Reduction and Oxidation of Fe3+ in Dioctahedral Smectites—2: Reduction with Sodium Sulphide Solutions

Abstract: Reaction with Na2S solutions at high pH led to almost complete, reversible reduction of iron in montmorillonite, whereas the structural iron of nontronite persisted in the ferric form. Concentrated Na2S solutions caused severe corrosion of nontronite and extracted appreciable amounts of iron, which was precipitated as sulphides. In contrast the morphology of montmorillonite was preserved and only very minor amounts of iron were extracted. These differences were attributed to the high concentration of Fe-OH-Fe groups in nontronite, which are unstable on reduction. The difference between Na2S and other reducing agents is discussed.

Triethylene diamine-clay complexes as matrices for adsorption and catalytic reactions*

Abstract: Complexes of 1,4-diazabicyclo [2.2.2] octane (triethylene diamine) with smectite and vermiculite were made for the purpose of exposing the internal surfaces of the clays for adsorption of gases and possible catalytic activity. When the diprotonated form of the amine saturated the exchange sites, internal surfaces of the clays were found to be available to nitrogen, ethane, and 2,4-dimethyl pentane. Proton lability in the smectites was studied with NH3, D2O, and C6D6 experiments. Catalytic function was demonstrated in the conversion of acetonitrile to acetamide in the smectite.

Structural analysis of sepiolite by selected area electron diffraction; relations with physico-chemical properties

Abstract: The electron structural analysis of a Madagascar sepiolite (Ampandrandava) was carried out by selected area electron diffraction obtained from monocristals. Fourier projections, derived from the experimental intensity of Okl, hOl and hkO reflections, show that the Mg2+ cations on the edges of the sheets are distributed between two sites. Correlatively the water molecules bound to these Mg2+ occupy two distinct positions. These principal structural differences with the Brauner and Preisinger model explain details of the i.r. spectra during the desorption of water or the adsorption of polar molecules. The differences between the two models can be considered as a consequence of treating the mineral in vacuum.

Analysis of iron-bearing clay minerals by electron spectroscopy for chemical analysis (ESCA)

Abstract: Nontronite and biotite were analyzed by Electron Spectroscopy for Chemical Analysis (ESCA). Both minerals yielded ESCA spectra with well-defined peaks and the elements identified by the ESCA spectra were in good agreement with the molecular formulas. High resolution scans were made of the iron (2p3/2) and oxygen (1s) electron binding energies for oxidized and reduced forms of nontronite and biotite. Binding energies for Fe3+ were observed at 711.8 eV in dithionite-reduced nontronite and in oxidized biotite. Peaks for Fe2+ occurred at 710.0 eV for unaltered biotite, at 709 eV for oxidized biotite and at 708.6 eV for hydrazine-reduced and dithionite-reduced nontronite. The oxygen (1s) peak for unaltered nontronite was skewed to the high energy side of the 530.6 eV maximum, but became more symmetrical as the Fe2+ content increased.

Origin and position of exchange sites in kaolinite: an esr study

Abstract: Electron spin resonance (ESR) spectroscopy is used to investigate the nature of exchange sites on kaolinite. ESR spectra of exchangeable Cu2+ and Mn2+ on kaolinite indicate that divalent exchange ions are about 11–12A apart on kaolinite surfaces and that planar Cu (H2O) 4 2+ ions are oriented parallel to the surfaces. Solution-like spectra for exchangeable Cu2+ and Mn2+ are observed at high relative humidities, suggesting a high degree of mobility of exchange cations on kaolinite surfaces. The evidence seems to eliminate edge sites as being active in cation exchange at least in the acidic range of pH. Similar conclusions are derived from ESR studies of Cu2+-saturated talc and pyrophyllite. It is proposed that most exchange sites arise from ionic substitutions or mineral impurities in phyllosilicates.

Organic Derivatives of Attapulgite—I. Infrared Spectroscopy and X-Ray Diffraction Studies

Abstract: Highly significant differences are observed between the methyl derivatives of attapulgite, produced when this mineral is reacted with (CHz)zSi(OCzHs)2, the presence or in absence of HCI In the first case, the corresponding infrared spectra show characteristic absorption bands due to the Si(CH3)z radicals at 1260, 850 and 800cm -a as well as a shoulder at 960cm -t, the latter assigned to silanol groups The 850 cm-1 frequency which is usually exhibited by trimethylsilicon compounds is also detected when -O-Si(CH3) 2 radicals are grafted in the silicates, but only if HC1 is present in the reaction Neither this band nor the 960 cm- 1 shoulder appear in the spectrum of the derivative synthetized in absence of HC1 A comparative study by both ir spectroscopy and X-ray diffraction does not reveal structural modifications in attapulgite after it has been methylated in absence of HC1 However, although the ir spectra of the HCl-methylated derivatives, prepared at different periods, do not indicate substantial structural perturbations, X-ray diffraction patterns show a gradual weaken- ing of the peaks due to attapulgite, as reaction time increases; the intensity of the (110) order reflection is drastically reduced after a 165 hr attack The most viable mechanism for the grafting of the dimethylsi- loxy units in attapulgite is through the HCI induced silanol sites When the reaction is taking place in anh benzene medium (absence of HC1), dimethyldiethoxysilane may be hydrolyzed by a fraction of water contained in attapulgite; the hydrolysis products which do incorporate on the surface of the silicate are identified by ir spectroscopy

Microstructure, mineralogy and chemistry of Cambrian glauconite pellets and glauconite, central U.S.A.

Abstract: Glauconite pellets in the Cambrian of the central U.S.A. frequently contain two textural forms of glauconite–aggregate and oriented—which differ in both mineralogy and chemistry. The aggregate glauconite composes the bulk of most pellets and consists of crystals in a nearly random arrangement. The oriented glauconite occurs primarily as rims on the periphery of pellets. It has a honeycomb-like structure—the crystals are oriented with their c-axes tangent to the aggregate-textured cores. Scanning electron photomicrographs show that the aggregate and oriented textures grade one into the other. The aggregate glauconite has a 1 M structure and less than 5% expandable layers, whereas the oriented form has a 1 Md structure and ∼ 10% expandable layers. The aggregate glauconite contains 5–8% more total iron oxides and 2–3% less Al2O3 than the oriented glauconite. The b-cell dimension of individual samples increases nearly linearly with increasing octahedral Fe3+ + F2+ + Mg content. Chemical and crystallographic variations among various samples are, for the most part, related to the ratio of aggregate to oriented glauconite. The transition between the texture of the aggregate and oriented glauconite suggests that some glauconite pellets may form by concretionary growth. It is proposed that Cambrian glauconite pellets grew through the repetitive development of a smectite-like clay at the margin of pellets. The smectite was later altered, both chemically and texturally, first to the oriented and then to the aggregate-textured glauconite.

Interpretation of Infrared Spectra of Oxidized and Reduced Nontronite

Abstract: Infrared spectra of nontronite reveal shifts to lower wave, number in peaks located at 3570, 1030, and 821 cm-1, which are assigned to vibrational modes for O-H stretching, Si-Ob (basal oxygens) tetrahedral vibrations, and FeO-H deformation, respectively, as the Fe2+ content increases upon reduction. A pleochroic shoulder at 1110 cm-1 resulting from Si-Oa (apical oxygens) interactions appears to be unchanged with reduction. The absorption band at 848 cm-1 shifts to higher energy with reduction of structural iron, and persists at 840 cm-1 after complete deuteration of structural hydroxyls. The band is assigned to a Fe-OH mode where the OH moves as a unit. The shift in the Si-Ob mode to lower vibrational energy with reduction may indicate a decrease in stress forces between the tetrahedral and octahedral sheets.

Protonation of Organic Bases in Clay—Water Systems

Abstract: The extent of protonation of organic bases in clay—water systems depends upon the adsorptive properties of the organo-clay species involved, and upon the structure and degree of hydration of the clay system. Organic molecules that can disperse cationic charge over two or more condensed aromatic rings give rise to greater surface-induced protonation than do single-ring organic molecules with similar solution pKa. Protonation in clay suspensions is frequently far in excess of that predicted on the basis of electrolytic suspension pH and solution pKa of the organic base. For a given organic base, protonation in a clay film exceeds that in the suspended clay system. Protonation in an organo-clay film increases as the film moisture content decreases. The extent of protonation in organo—clay systems varies with cationic species, cationic saturation, and clay type.

Formation of phyllosilicates and zeolites from pure silica-alumina gels

Abstract: The hydrothermal aging of pure silica-alumina gels in presence of 10 ml of 0.1 N sodium hydroxide solution at 175, 150 and 130~ for 8-30 days led to the synthesis of zeolites and the phyllosili- cates, beidellite and kaolinite. The solution was neutralized by a partial hydrolysis of the gel which readily reorganized into a prezeolitic material. At pH values/> 9, with 300 or 600 mg of gel, it evolved towards the crystalline zeolites P and S, with low surface area (7-100 m2/g) but high exchange capacity (300-475 m-equiv./100 g). With gel amounts of 600-2400 mg, and pH values of 8-5.5, the prezeolitic material provided rows of O-Si-O-A1-OH which recombined to form the phyllosilicate structures. Surface area increased (170-325 m2/g) but exchange capacity decreased (100-250m-equiv./100 g). The results obtained by various techniques (XRD, DTA, IR) indicated a moderate degree of crystallinity of these phyllosilicates; in addition, X-ray powder diffraction suggested that hk bands were the first to develop. The positive results obtained with a 0.40 ratio A120 3 gel compared with the negative results obtained with 0.30 or 0.50 A120 3 gels indicate that the gel composition is very important for the formation of phyllosilicates under the experimental conditions.

The influence of crystallite size on the apparent basal spacings of kaolinite

Abstract: For very small crystallites diffraction theory shows not only broadening of powder lines, but generally also a shift of the line position, depending on the change of the structure factor over the range of broadening. For decreasing thickness of kaolinite crystals (less than 50 layers) an increasing shift of reflections is found: the lines (001), (002), (004) and (006) are shifted to apparently larger spacings, the lines (003) and (005) to smaller spacings, resulting in a nonintegral series. Presuming a known crystallite size, tables are given for evaluating true spacings from measured values of 2θ.

High Extraction Magnetic Filtration of Kaolin Clay

Abstract: A new magnetic separation technique combines high magnetic fields, extreme gradients, and controlled retention time to separate feebly magnetic mineral contaminants from kaolin. Extraction of pyrite, siderite, hematite, iron stained anatase, and mica by magnetic filtration of kaolin significantly upgrades brightness of many sub-marginal deposits and reduces consumption of reagents in processing.

Solubility Diagrams for Explaining Zone Sequences in Bauxite, Kaolin and Pyrophyllite-Diaspore Deposits

Abstract: Solubility diagrams defined by log (A13 +) and log (H,SiO,) are given for hydrous alumina or aluminum silicate minerals which appear in bauxite, kaolin and pyrophyllite

Scan electron micrographs of kaolins collected from diverse origins; III, Influence of parent material on flint clays and flint-like clays

Abstract: The nature of the parent material from which flint clay or flint-like clay is derived may modify the texture of the clay as observed by SEM. Flint clays occurring in Pennsylvanian-age swamp basins into which were transported residues weathered from sedimentary country rock exhibit a texture of interlocked kaolin pockets and sheaves. On the other hand, flint clay or flint-like clay derived by weathering of volcanic ash exhibits a texture resembling, on a micro-scale, the scalloped, “oak-leaf” pattern of montmorillonite. The interpretation is that an expanding clay having a transitional role between the ash and the kaolinite is the donor source of the micro-scalloped pattern inherited by kaolinite. X-ray powder diffractograms of the clays support the interpretation.

Interaction between Alkali-Halides and Halloysite: I.R. Study of the Interaction between Alkali-Halides and Hydrated Halloysite

Abstract: Halloysite was mechanically ground in the presence of NaCl, KCl, RbCl, RbCl and CsCl, and i.r. spectra were recorded after various periods of grinding, up to 10 min. Changes in the wave-numbers and sharpness of absorption bands were interpreted using assignments accepted for kaolinite. Diminution of absorption bands of OH groups and the appearance of new bands indicate formation of complexes of halloysite with KCl, KBr, RbCl, and CsCl. Water was essential in the complex formation, which may be formulated: The amount of the complex formed depended on the salt and the time of grinding. Complex formation requires that the cation be large enough to serve as a “structure breaker” of the interlayer water sheet. Complex formation also requires that the cation be a weak electron acceptor. Grinding also led to changes in the fine structure of the tactoid. The possibility of using the i.r. spectrum of halloysite as a finger print for identification of the mineral is discussed. It was concluded that NaCl is the most reliable dispersing agent to determine whether or not a mineral sample belongs to the kaolinite group. Disks in RbCl may be used to differentiate between kaolinite and hydrated halloysite.

Quantitative X-ray powder diffraction analyses of clays using an orienting internal standard and pressed disks of bulk shale samples

Abstract: Quantitative analysis of clay minerals by x-ray diffraction requires oriented clays in order to increase detection limits of the analyses. This is achieved commonly either by smear or sedimentation techniques; however, these techniques can lead to poor analytical precision when used with an internal standard because they often produce nonhomogeneous internal standard-clay mineral mixtures. Compaction of bulk shale material at 8000 psi in a hydraulic press produces preferred orientations comparable to that produced by smear or sedimentation. When used with a suitable platy internal standard which provides an estimate of clay mineral preferred orientation, excellent analytical precision is achieved routinely. Several lines of experimental evidence indicate that 1 to 5 m ..mu.. MoS/sub 2/ is an ideal orienting internal standard for use with compaction mounts.

Tosudite from the Hokuno Mine, Hokuno, Gifu Prefecture, Japan

Abstract: Tosudite was found in the Hokuno pottery stone mine, Gifu Prefecture, Japan. The pottery stone ore body, altered from the Cretaceous rhyolitic rock, is composed of tosudite, interstratified illite-montmorillonite, kaolinite and quartz. Prepared by normal sedimentation method, the specimen is composed of 75.6% tosudite, 24.0% kaolinite and 0.4% quartz. The chemical composition of the specimen is SiO2 45.09%, TiO2 tr., Al2O3 37.31%, Fe2O3 0.94%, MgO 0.41%, CaO 1.94%, Li2O 0.45%, Na2O 0.09%, K2O 0.44%, H2O(−) 1.50% and ignition loss 12.11%. After subtracting the compositions of the impurities, the structural formula of tosudite is given as; interlayer cations K0.23, Na0.07, Ca0.86 + nH2O; ‘gibbsite’ layer Li0.76, Mg0.35, \({\rm{Fe}}_{0.29}^{3 + }\), Al3.34 (OH)12.00; silicate layer Al8.00 [Si13.83 Al2.17] O40.00 (OH)8.00.