bluuebunny/crossref_metadata_2025 huggingface dataset:
Mineral reactions at grain contacts in early stages of granite weathering
Authors: Meunier A. , Velde B.
Published: December 2006

Two outcrops were studied which showed granite in the early stages of weathering. Reactions between specific mineral species were observed, and especially the formation of an illite-like phase which is similar to that of sedimentary illite. This phase has a composition distinct from that of the initial micas in the rocks, notably in its iron and magnesium content. This suggests solution-solid equilibria which involve ionic transfer beyond the grain bondary region where the mineral is found.
Weathering of clay minerals in a Navarre andosol (Spain)
Authors: Barragan E. , Iñiguez J.
Published: December 2006

The evolution of clay minerals in a Navarre Andosol (Spain) is investigated. The results indicate formation of allophane, evolution of trioctahedral mica to dioctahedral illite and the appearance of 10:14 A interstratified mineral in the lower layer. In the top horizons the interstratified mineral changes into vermiculite. The mineral distribution in the profile is indicated.
Zur Mineralogie, Kristallchemie und Geochemie Kretazischer Glaukonite
Authors: Kohler Ewald E. , Koster Heinrich M.
Published: December 2006

Glaukonitglimmer von 10 kretazischen Gesteinen werden mineralogisch und chemisch untersucht. Die von den Glaukonitkòrnern und Glimmern der Kolloidtonfraktion errechneten Strukturformeln der Glaukonitglimmer bestàtigen die Glaukonitglimmer als exakt dioktaedrische Minerale. Die Strukturformeln geben nur Mittelwerte der Verteilung der chemischen Hauptbestandteile und der Kationenladung der Glaukonitstruktur an. Innerhalb des Konzentrationsdreieckes Muskowit-Seladonit-Pyrophyllit deckt sich das Areal der Glaukonite mit dem der Illite, wenn auf den Seiten des Dreieckdiagrammes die Kationenladungen der Tetraeder-, Oktaeder- und Zwischenschichten aufgetragen werden. Entsprechend der iibereinstimmenden Verteilung der Kationenladungen in der Glaukonit- und Illitstruktur kònnen die Glaukonite als die eisenreichen Àquivalente der Illite angesehen werden. Der Gehalt an Spurenelementen in Glaukoniten ist, abgesehen vom Bor, deutlich geringer als in Biotiten und Muskowiten. Die chemische und strukturelle Inhomogenitat der Glaukonite in den Gesteinen wird am besten durch eine Entstehung der Glaukonite aus Gelen im Sediment erklàrt.
Influence des substances humiques sur les propriétés des argiles
Authors: Chassin Pierre , Le Berre Brigitte , Nakaya Norio
Published: December 2006

Après avoir rappelé l'importance du mode de préparation des associations montmorillonite-acides humiques sur leurs propriétés d'hydratation, nous présentons les résultats obtenus par adsorption d'azote.

L'ensemble des résultats obtenus sur ces associations indique que la localisation de la matière organique dans l'espace poral de l'argile joue un grand rôle, localisation qui varie avec le mode de préparation des échantillons et la teneur en carbone.

On donne une interprétation générale des courbes représentant la variation des quantités d'eau fixées par ces associations, quand la teneur en carbone augmente.
The location and content of iron in natural biotites and phlogopites: a comparison of several methods
Authors: Sanz Jesus , Meyers Jacques , Vielvoye Léon , Stone William E. E.
Published: December 2006

Mössbauer spectra have been obtained at room temperature on a series of phlogopites and biotites which have also been characterized by chemical analyses, I.R. and N.M.R. The distribution of the Fe2+ ions on the two possible octahedral sites is on the average nearly random. A clear example of tetrahedrally coordinated Fe3+ ions in a natural phlogopite is given. This phlogopite has a very high vermiculitization ability. The Fe3+ content of the samples has been determined by two different chemical methods and it is shown that even when precautions are taken to minimize oxidation, the agreement with Mössbauer spectra is poor.
Calculated X-ray diffraction curves for the interpretation of a three-component interstratified system
Authors: Cradwick P. D. , Wilson M. J.
Published: December 2006

Three-component interstratification of layer silicate minerals in the clay fractions of soils and sediments is probably more common than is generally realized. However, interpretation of the proportion and arrangement of the various components from experimentally recorded X-ray diffraction curves is difficult and in this paper a series of calculated diffraction patterns are presented which illustrate the types of diffraction patterns obtained from interstratified mica-vermiculite-montmorillonite systems.
An occurrence of polymorphic halloysite in granite saprolite of the Bayerischer Wald, Germany
Authors: Wilke B.-M. , Schwertmann U. , Murad E.
Published: December 2006

XRD, DTA and IR patterns showed clay veins filling fissures in a granite of the Bayerischer Wald (eastern Bavaria) to consist mainly of hydrated halloysite of low crystallinity with traces of gibbsite, 2:1 (mixed layer) clay minerals and iron oxides. The halloysite forms thin plates which exhibit varying degrees and types of enrolment, resulting in platy, tubular and spheroidal crystals within the same sample. Concentrations of the trace elements Rb, Sr, Ba, Zr, Y, Ce, Pb, Zn and Cu indicate halloysite formation to have taken place via an aqueous phase under the influence of vadose waters circulating in fissures.
The effect of Fe-for-Si substitution on the b-dimension of nontronite
Authors: Russell J. D. , Clark D. R.
Published: December 2006

A survey of 060 spacings of dioctahedral smectites has shown that for nontronites with only iron on octahedral sites, a linear relationship exists between the b-axial dimension and the number of atoms of tetrahedrally coordinated Fe3+ per unit cell containing O20(OH)4. The slope, 0·0497 Å/Fe3+, is steeper than that for the increase in b resulting from Fe3+ on octahedral sites, 0·0377 Å/Fe3+, demonstrating the greater importance of tetrahedral substitution in influencing b. Factors that take account of the number of Fe3+ atoms on tetrahedral sites have been incorporated in existing formulae for calculating b-axis cell dimensions for smectites, but these are usually less successful in predicting b than a new formula involving only tetrahedral and octahedral iron contents.
Étude des facteurs influencant l'evolution structurale de la montmorillonite k et sa réversibilité
Authors: Gaultier J.-P. , Mamy J.
Published: December 2006

La rétention du K par la montmorillonite est liée à une modification de l'ordre de superposition des feuillets élémentaires apparaissant au cours des cycles d'humectation et de dessiccation (HD). A ce sujet deux questions sont évoquées:

(1)

L'importance relative des facteurs expérimentaux mis en jeu: température de séchage et hydratation. Pour un nombre donné d'HD la quantité de K fixé ainsi que les diagrammes de diffraction X et électronique sont indépendants de la température. Le facteur essentiel de la transformation est donc le mouvement de l'eau au niveau interfeuillet.

(2)

Les conditions de libération du K de la montmorillonite et les conséquences de cette libération sur la structure acquise.

L'eau ne pénètre plus dans les espaces interfeuillets de la montmorillonite ayant subi plus de 100 HD; cependant l'éthylène glycol provoque encore une ouverture presque complète à 17 Å, sans pour autant perturber la structure tridimensionnelle.

Des essais d'extraction par différents cations ont montré qu'une fraction importante du K demeure à l'état non échangeable. Mais lorsque la quantité de K extraite atteint 70%, la structure tridimensionnelle est détruite, et l'on revient à un empilement turbostratique.
Preparation et étude spectrometrique de complexes silicates phylliteux colorants azoïques
Authors: Siffert B.
Published: December 2006

Une méthode de synthèse directe de complexes entre un silicate phylliteux et des pigments azoïques a été mise au point. L'étude des complexes obtenus montre que le mécanisme d'interaction entre le feuillet phylliteux et le colorant azoïque fait intervenir des réactions de transfert de charges. On a pu mettre en évidence des phénomènes d'oxydo-réduction et des réactions acide-base. Le mécanisme d'interaction dépend du mode de préparation du complexe. Suivant les conditions de pH du milieu, la fixation du colorant s'effectue soit par une simple ‘précipitation’ dans la structure, soit par échange d'ions. La molécule de colorant subit généralement une protonation au cours de son incorporation avec formation de cations à structure quinonique. La protonation peut se faire soit à partir de protons, cations échangeables du minéral, soit à partir de protons provenant d'une ionisation de groupements structuraux AlMgOH. Le phénomène de protonation apparait prédominant vis-à-vis des réactions d'oxydo-réduction. La présente étude montre également qu'il est difficile de savoir si les phénomènes d'oxydo-réduction ont lieu par l'intermédiaire des atomes d'aluminium ou de fer de la structure ou par des cations Al3+ et de l'alumine eventuellement formés au cours de l'attaque du réseau.
Hydration and dehydration characteristics of synthetic water-swelling fluoromicas: comparisons between silicates and germanates
Authors: Kitajima K. , Daimon N. , Kondo R.
Published: December 2006

Solid solutions of fluoromicas WMg2Li(Si4−x GexO10)F2 (W = K, Na, Li. 0 ≦ x ≦ 4), which were closely related to taeniolite, were synthesized and the effect of the isomorphic substitution Ge for Si and also the interlayer cations Li, Na and K respectively upon hydration and dehydration were studied by X-ray diffraction, infrared and thermal analysis. The Na- and Li-series exhibit swelling with water, whereas the K-series does not. The increase of tetrahedral germanium substitution reduces hydration and also lowers the dehydration temperature of hydrates in both the Na- and Li-series. The reasons for such tendencies are discussed. Repulsion between interlayer cations and tetrahedral cations seems to play the dominant role. K in opposition to the smaller interlayer cations Li and Na respectively fits in the interlayer sites of the mica structure and lowers repulsion. By increasing the substitution Ge for Si interionic distances become greater and repulsion also decreases.
Beidellite crystallization from plagioclase and amphibole precursors: local and long-range equilibrium during weathering
Authors: Proust D. , Velde B.
Published: December 2006

A comprehensive study of weathering in plagioclase-hornblende rock (amphibolite) from La Roche-l'Abeille, Massif Central, using optical and classical methods of clay mineralogy and electron microprobe determinations demonstrates the mineral reactions which can occur as amphibole and plagioclase weather. Both minerals decompose ultimately into beidellitic smectites but of different lattice compositions. It appears, depending on the host mineral, that an aluminous ‘intergrade’ mineral, similar to a hydroxy-complexed vermiculite, forms first, recrystallizing into the beidellites. Exchangeable ion composition of the beidellites suggests that all smectites were in equilibrium with waters of similar chemical activity for Ca and Mg ions at equivalent depths in the profile. The activities of the exchangeable interlayer ions of the newly-formed smectites are similar, regardless of the host mineral. Very local chemical potentials evidently dictate the lattice composition of the phases, ferribeidellite formed from amphiboles, aluminous beidellite formed from plagioclases, but longer range equilibria (centimetric) dictate the type of phase which will crystallize, i.e. smectite.
Reactions of salts with kaolinite at elevated temperatures. I
Authors: Heller-Kallai L.
Published: December 2006

On heating at temperatures below 600°C kaolinite reacts with salts of alkali metals according to the equation

2SiO2 · Al2O3 · 2H2O + 2nMX → 2SiO2 · Al2O3 · nM2O + 2nHX + (2−n)H2O

The reaction commences with the dehydroxylation of the clay and is favoured by high solubility of the salt and small size of the alkali ion.

It appears that on dehydroxylation the clay becomes reactive and, concurrently, the water liberated dissolves adjacent salt particles and catalyses the reaction.

Infrared spectra indicate that alkali ions are incorporated directly into the aluminosilicate structure, without the formation of metakaolinite as a detectable intermediate. The initial product is disordered, but as n approaches 1, crystalline phases tend to be formed.
Infrared spectra of muscovites as affected by chemical composition, heating and particle size
Authors: Sayin Mahmut , Graf von Reichenbach H.
Published: December 2006

Nine muscovite samples from different localities were analysed for all major chemical elements and examined by infrared spectroscopy in the range of 4000–250 cm−1. Iron in the octahedral positions was found to cause an intensity decrease and shifting of some absorption bands. Other structural cations were found not to be effective in producing intensity and frequency changes due to the narrow variations in their amounts. Heating studies indicated that at about 800°C muscovite transforms into a dehydroxylated phase which is stable at least up to 1000°C. Particle size studies showed that 5 µm is the upper size limit for a representative spectrum.
Contribution au mécanisme d'adsorption des α-amino-acides par la montmorillonite
Authors: Siffert Bernard , Kessaissia Saliha
Published: December 2006

L'étude de l'adsorption des α amino-acides à leur point isoélectrique par la montmorillonite saturée en cations minéraux de valences différentes montre que la quantité fixée dépend de la réactivité de l'acide aminé pour le cation minéral saturant la smectite. La fixation des α amino-acides est plus forte avec les cations bivalents qu'avec les cations monovalents; elle s'accompagne d'une libération des cations minéraux (échange).

Nous avons pu mettre en évidence l'existence de relations linéaires entre les quantités d'amino-acide fixé et les quantités de cations incorporés dans le minéral. Ces relations permettent de connaître à priori le comportement d'un acide aminé donné vis-à-vis de la montmorillonite saturée en un cation donné. Elles permettent de classer les amino-acides en trois familles: (1) les amino-acides qui sont incorporés sous une forme cationique simple par échange d'ions; (2) les amino-acides qui forment des sels et/ou des complexes de coordination avec les cations métalliques; (3) les amino-acides qui présentent un comportement compliqué et dont l'incorporation dans la smectite se conjugue avec une polycondensation.
Mode d'empilement des feuillets dans les vermiculites hydratées à ‘deux couches’
Authors: De La Calle C. , Suquet H. , Dubernat J. , Pezerat H.
Published: December 2006

Pour les hydrates à ‘deux couches’ des vermiculites issues des phlogopites 1 M, saturées par Li, Na, Ca, Mg ou Ba, nous avons rencontré quatre modes d'empilement des feuillets. Un seul (VIII) présente une structure ordonnée tridimensionnellement. Les trois autres (VI, VV et VVII) sont des structures semi-ordonnées.

Nous avons défini les translations entre feuillets pour chaque empilement ainsi que les domaines d'existence en fonction du cation et de l'humidité relative.

Pour l'édifice ordonné VIII calcique la structure de la couche interfoliaire est décrite (deux types de polyèdres d'eau plus de l'eau de liaison entre polyèdres).

Les diffèrents facteurs conditionnant, pour une vermiculite donnée, le ‘choix’ d'un mode d'empilement sont discutés : facteurs propres à la couche interfoliaire (nature des cations et degré d'hydratation); facteurs propres au feuillet (densité et localisation des charges, disposition des oxygènes de surface); facteurs liés à la texture.
Étude de l'eau dans la palygorskite à l'aide des analyses thermiques
Authors: Mifsud Amparo , Rautureau Michel , Fornes Vicente
Published: December 2006

Les analyses thermiques (A.T.P. et A.T.D.) de la palygorskite ont été réalisées entre 20 et 900° La palygorskite contient trois types d'eau nettement différenciés par leur rôle dans la structure. Cependant, les analyses thermiques indiquent un chevauchement des domaines de température où ces diverses molécules d'eau sont éliminées. L'interprétation des enregistrements à partir de la zone de plus haute température (qui correspond aux plus fortes énergies de liaison des molécules d'eau éliminées) permet d'obtenir un bon accord entre les résultats expérimentaux et ceux calculés à partir du modèle dioctaédrique du minéral.
Flint clays, tonsteins and the kaolinite clayrock facies
Authors: Loughnan F. C.
Published: December 2006

The characteristic structural, textural and compositional features of the various kaolinite-rich clayrocks known as flint clay, toasted clay, kaolinite tonstein and bauxitic clay are briefly reviewed together with their mode of occurrence. It is considered that these rocks have much in common; sufficient to warrant their grouping in a single sedimentary facies. The origin of these clayrocks is discussed and it is concluded that whereas some modifications apparently took place within the depositional area, the concept of development in Situ for the bulk of the material is difficult to substantiate. Rather, the evidence appears consistent with an essentially allochthonous origin.
Alteration of mica surfaces by water and solutions
Authors: 't Serstevens A. , Rouxhet P. G. , Herbillon A. J.
Published: December 2006

Samples of muscovite and phlogopite of particle sizes varying from less than 5 µm to 500 µm were allowed to stand in distilled water and in several NaNO3 solutions. The modifications of their surface were determined by thermovolumetric measurements of the extra-water associated with the altered rim.

Phlogopite undergoes congruent dissolution due to protonic action at low pH and vermiculitization by sodium under other conditions. Muscovite ground and aged in water suffers potassium hydrolysis and silica dissolution both of which contribute to the accumulation of aluminium on the surface. The altered rim, which develops on basal surfaces as well as on the edges, has an extra-water content of about 1·2 H2O molecules per accumulated Al atom; the surface can be cleaned by a treatment at low pH.
Contribution a l'étude des interactions vermiculite-colorants cationiques
Authors: Saehr D. , Dred R. Le , Hoffner D.
Published: December 2006

Une vermiculite-M (M = Na,K) sous la forme de macrocristaux gonflés à l'eau, de 1 à 4 mm2, adsorbe par échange d'ions des colorants cationiques en solution aqueuse. La sélectivité de cette vermiculite-M pour ces cations est très faible et sa teneur ne dépasse pas 7% de la capacité d'échange de cations.

Les spectres d'absorption visible des vermiculite-(M,colorant) obtenues, comparés à ceux des cations colorant en solution aqueuse, montrent dans le cas des cations bleu de méthylène, bleu de Nil A et vert brillant un déplacement de l'ordre de 25 nm de l'une des bandes. Du fait de l'adsorption, la charge des cations colorant adsorbés est plus localisée, soit sur leurs hétéroatomes centraux (bleu de méthylène), soit sur leurs hétéroatomes périphériques (vert brillant). La spectrométrie infrarouge ne contredit pas ces résultats.

Les vermiculite-(M,colorant) ne sont pas des pigments colorés et l'utilisation de la vermiculite comme support de colorants est très limitée.
Étude par diffusion brownienne de la fixation de l'acide glutamique dans les systèmes eau-montmorillonite et eau-kaolinite
Authors: Salha Cl. , Chanal J. L. , Bontoux J.
Published: December 2006

Les auteurs ont étudié, par la technique de la diffusion brownienne l'interaction existant entre l'acide-L-glutamique et les systèmes eau-kaolinite et eau-montmorillonite, ainsi que l'influence du pH sur les coefficients de diffusion.

Il nous a été possible d'éliminer les facteurs mécaniques d'allongement de parcours en étudiant la diffusion de l'eau dans le système eau-argile.

Les résultats montrent une plus faible diffusion de l'acide glutamique dans le système eau-kaolinite que dans le système eau-montmorillonite.

L'effet du pH est discuté.
Adsorption of herbicide-derived anilines in dilute aqueous montmorillonite suspensions
Authors: Moreale A. , Van Bladel R.
Published: December 2006

Adsorption isotherms of aniline and p-chloroaniline were determined from very dilute solutions on montmorillonite saturated with different cations (i.e. Na+, K+, Ca2+, Mg2+, Cu2+, Fe3+ and Al3+).

In all cases p-chloroaniline was absorbed to a greater extent than aniline. The shapes of the isotherms depend on the adsorbate and on the exchangeable cation and are interpreted in terms of adsorption mechanisms.

For aniline, the solvation of the adsorbate and the electronegativity of the saturating cation seem to be the main factors, whereas for p-chloroaniline the polarizing power of the exchange cation plays an important part. In the case of the Fe3+ ion the oxidizing power seems also be involved.

The enthalpy changes (ΔH°), calculated from the temperature coefficient of the equilibrium constant are exothermic but less exothermic as the polarizing power of the exchange cation increases. The adsorption of the amines on Na-, K- and Ca-, Mg-montmorillonite gives rise to an entropy loss which is higher for the divalent cations. This result is in good agreement with desorption curves obtained after several washings which indicated for the nature of the organo-clay complexes the decreasing order of stability, viz Mg2+ > Ca2+ > K+ > Na+.
Infrared spectroscopy of ferrihydrite: evidence for the presence of structural hydroxyl groups
Authors: Russell J. D.
Published: December 2006

IR spectroscopy has shown that adsorbed water is almost completely removed from ferrihydrite by evacuation at room temperature. Absorption bands at 3615 and 3430 cm−1 appearing thereafter are interpreted as arising from OH groups located respectively at the surface and deeper in the structure. These groups are readily converted to OD on treatment with D2O vapour and this has allowed the OH deformation vibration to be identified at 800 cm−1. It is proposed that OH groups in ferrihydrite are about half as numerous as those in akaganéite (β-FeOOH) and that they may occur in environments similar to those in this mineral. The formula for ferrihydrite proposed by earlier workers, 5 Fe2O3.9H2O, should thus be amended to Fe2O3. 2 FeOOH.2·6H2O in order to indicate the presence of structural OH groups. A re-appraisal of the ferrihydrite structure appears desirable.
The influence of Al on iron oxides. Part III. Preparation of Al goethites in M KOH
Authors: Lewis D. G. , Schwertmann U.
Published: December 2006

Aluminium substituted goethites (Fe, Al)OOH were synthesized from Fe(III), Al systems (ferrihydrites) in m KOH at room temperature. A linear correlation existed between degree of Al substitution and log[Al] in solution. Incorporation of up to 12 mole % Al was obtained. The rate of conversion of ferrihydrite to goethite decreased as [Al] increased. The goethite consisted of thin elongated plates approximately 0·1 µm long with serrated edges and reduced growth in the crystallographic X-direction. The presence of salts and the nature of the starting material either an Al-ferrihydrite or a ferrihydrite in aluminate solution did not influence the degree of substitution, but only the rate of formation of the goethite.
An infrared spectroscopic study of the interaction of nontronite and ferruginous montmorillonites with alkali metal hydroxides
Authors: Russell J. D.
Published: December 2006

IR spectroscopy has been used to study the interaction of alkali metal hydroxides with dioctahedral smectites having iron contents of 0·7% (montmorillonite) to 22% (nontronite), in connection with the alkali-stabilization of soils. The results have shown that the alkalis (LiOH, NaOH, KOH and CsOH) deprotonate hydroxyl groups co-ordinated to octahedral ferric iron, causing distortion of tetrahedral and octahedral layers. This concept of distortion is supported by a striking change in Mössbauer spectra and a large increase in b cell dimensions. The perturbation of the smectite structure, shown by shifts in the Si-O and O-H stretching vibrations, is greater for Na, K and Cs than for Li, suggesting that the larger cations interact with surface oxygens around the hexagonal hole. IR spectra suggest that the effect of NaOH on nontronite is substantially reversed by treating the smectite with CO2 or acetic acid vapour or by washing it with dilute salt solution, although Mössbauer spectroscopy and XRD indicate that the structure of the regenerated smectite is more disordered than that of the original.
Natrojarosita en la base de la formacion utrillas en nuevalos (Zaragoza) aspectos mineralogicos y geneticos
Authors: Perez del Villar L. , Rodriguez-Gordillo J. , Fenoll Hach-Ali P.
Published: December 2006

En el miembro basal de la Formación Utrillas, que aflora en las cercanias de Nuévalos, se ha localizado un nivel constituido por ilita, montmorillonita, natrojarosita, caolinita, cuarzo y materia carbonosa.

Se aportan datos de análisis químico, termodiferencial, termogravimetrico, microscopico y de difraccion de rayos X de la natrojarosita.

Se le atribuye a dicho sulfato un origen sedimentario por precipitación en un medio de aguas estancadas, desarrollado sobre materiales margo-yesiferos del Keuper. El hierro aportado al medio, la materia orgánica, y los iones procedentes de la disolución de las evaporitas Triasicas, provocaron las condiciones fisico-quimicas necesarias para la precipitación de la natrojarosita.

Los minerales de la arcilla son heredados, a excepcion de la montmorillonita que se la podria considerar paragenetica con la natrojarosita.
Etude comparee de l'evolution des montmorillonites biioniques K-Ca de Camp-Berteaux et du Wyoming sous l'effet des cycles d'humectation et de dessiccation
Authors: Mamy J. , Gaultier J-P.
Published: December 2006

La fixation du potassium par la montmorillonite sous l'effet des cycles d'humectation et de dessiccation est un phénomène bien connu. On ne peut cependant considérer ce dernier comme responsable de la rétrogradation du K dans les sols que si cette fixation peut se produire même en présence d'autres cations. Chaussidon (1963) avait étudié dans ce but l'évolution de la montmorillonite de Camp-Berteaux K-Ca soumise à des cycles d'humectation et de dessiccation, et avait observé aussi, dans ce cas, une fixation du K. Depuis, les auteurs de la présente communication ont pu proposer un mécanisme de fixation du K par la montmorillonite. A la lumière de ces résultats (aussi les résultats de Glaeser & Mering (1954)) l'étude de l'évolution de la montmorillonite biionique K-Ca sous l'effet des cycles d'humectation-dessiccation a pu être reprise et interprétée. Les résultats de Chaussidon sur la montmorillonite de Camp-Berteaux et ceux qui ont été obtenus sur celle du Wyoming permettent d'établir une comparaison entre les deux minéraux. Le mécanisme de fixation du K est identique et une interprétation des différences observées est proposée.
X-ray and infrared investigations of a synthetic dioctahedral vermiculite saturated with alkali and alkaline earth cations
Authors: Sayin Mahmut , Von Reichenbach H. Graf
Published: December 2006

A synthetic dioctahedral vermiculite was saturated with Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr and Ba, and examined by X-ray diffraction and infrared spectroscopy under various dehydration conditions. Cations which were larger than the ditrigonal hole (Cs, Rb, Ba) increased the b-dimension by forcing the oxygen triads open. With small cations the b-dimension decreased as a function of the residual water content rather than of cation size. The OH stretching vibration did not change in position, probably due to the inclined orientation of OH groups. The cations perturbed the lattice vibrations when they caused a change in the tetrahedral rotation angle, i.e. in b-dimension. With the small cations Be, Li and Mg, librations below 450 cm−1 shifted towards higher frequencies indicating cation migration into the empty octahedral sites.
Adsorption of alcohols by smectites: I. Distinction between internal and external surfaces
Authors: Annabi-Bergaya F. , Cruz M. I. , Gatineau L. , Fripiat J. J.
Published: December 2006

The desorption of methanol and isopropanol by a series of charge-deficient Ca-montmorillonites (prepared by a partial Li-saturation and subsequent heat treatment of Camp-Berteau material) has been monitored gravimetrically and by XRD. The results indicate that about half the total adsorbed molecules do not occur within the interlamellar space of the montmorillonite but are occluded in micropores between particles.
Etude des interactions entre montmorillonites et agents organiques complexants
Authors: Guignard J. , Pezerat H.
Published: December 2006

On a étudié les interactions de différents ligands (cryptands et composés couronne) qui ont la propriété de complexer un grand nombre de cations en solution, avec des montmorillonites saturées par différents cations (Li+, Na+, K+, Ca2+, Cu2+).

Les résultats obtenus montrent qu'il y a bien ‘encagement’ des cations interfoliaires de la montmorillonite dans ces complexants. Ces cations complexés peuvent d'ailleurs s'échanger ultérieurement contre des cations simples.

Suivant la nature du cation complexé on obtient un gonflement à 14·5–15 Å ou à 16–17 Å. Ces ouvertures sont discutées en relation avec les encombrements des cations complexés.
Etude du systeme eau-vermiculite dans le proche infrarouge
Authors: Fornes V.
Published: December 2006

On étudie l'influence des cations compensateurs sur le spectre P.I.R. d'une vermiculite hydratée à deux couches. La définition d'un paramètre IR permet de quantifier cet effet. On conclue que l'énergie d'hydratation du cation est en relation avec la rigidité de la couche interfoliaire.
Mössbauer and X-ray data on β-FeOOH (akaganéite)
Authors: Murad E.
Published: December 2006

β-FeOOH (akaganéite) was prepared by slow hydrolysis of an FeCl3 solution. X-ray diffraction measurements gave refined unit-cell parameters of a=10·535 Å, c=3·030 Å.

Two doublets with δ(Fe)=0·39, ΔEQ=0·95, and δ=0·38, ΔEQ=0·55 mm s−1, respectively, can be fitted to the Mössbauer spectrum taken at room temperature.

Magnetically split Mössbauer spectra were registered at 135 and 4°K. These can be resolved into at least three superimposed sextets, corresponding to different Fe3+ sites in the β-FeOOH structure. At 4°K a three sextet model gives parameters of δ=0·36, ΔEQ=0·90, Hi=473; δ=0·35, ΔEQ=0·30, Hi=479; and δ=0·37, ΔEQ=−0·05 mm s−1, Hi=486kOe, respectively.

The complexity of the Mössbauer spectra of β-FeOOH limits the usefulness of this method as a tool for the identification of akaganéite in composite natural samples.
Interaccion de isocianatos con sepiolita
Authors: Fernandez Hernandez M. N. , Ruiz Hitzky E.
Published: December 2006

Se estudia la interacción del isocianato de butilo y del isocianato de fenilo con sepiolita, utilizando las técnicas de espectroscopía IR y anáilisis químico. En determinadas condiciones experimentales se produce un injerto de grupos orgánicos sobre la superficie mineral por formación de enlaces tipo uretano ≡ Si-O-CO-NH-R. Se ha puesto de manifiesto que el agua adsorbida sobre la superficie mineral, tiende a formar ureas simétricamente disustituídas como sub-producto de la reacción.
Adsorption and oxidation of aniline and p-chloroaniline by montmorillonite
Authors: Cloos P. , Moreale A. , Broers C. , Badot C.
Published: December 2006

The adsorption of aniline (ANL) and p-chloroaniline (PCA) from 0·02 M methanol and chloroform solution on air-dried montmorillonite is determined by the conjunction of several factors: (i) basicity of the solute, (ii) complexing ability, Brönsted and Lewis acidity of the exchangeable cation, (iii) polarity and Lewis basicity of the solvent. The principal adsorption mechanisms, inferred from infrared data, are direct or indirect coordination and protonation of the adsorbate. They take place simultaneously and to a relative extent depending mainly on the exchange cation.

On Fe-, Al- and H(Al)-montmorillonite ANL and PCA give rise to type II complexes, characterised by an intense charge-transfer band in the infrared region and by the formation of radical cations, evidenced by ESR spectroscopy. This oxidation process occurs on heating in air, but with Fe3+ in vacuo also and even at ambient temperature in methanol solution. On Cu-montmorillonite ANL, contrary to PCA, does not give a type II complex; however, radical species are produced in air and in vacuo and their production is enhanced by heating.
Iron-bearing kaolinite in Venezuelan laterites: I. Infrared spectroscopy and chemical dissolution evidence
Authors: Mendelovici E. , Yariv Sh. , Villalba R.
Published: December 2006

Fe substitution for Al in kaolinite (from Venezuelan laterites) is proved by infrared spectroscopy and chemical techniques. The location of Fe in the octahedral sheet is characterized by two absorption bands, at 865–875 and 3607 cm−1, assigned as δ Al-OH-Fe and v OH respectively. The detection of the 865 cm−1 band requires the use of CsCl for the preparation of the disks heated to 270°C so that the clay delaminates as a result of a kaolinite-CsCl-H2O complex formation. The 3607 cm−1 absorption is detected when KI disks are prepared. These two characteristic frequencies persist after either thermal decomposition or selective chemical dissolution of free iron and aluminium hydroxides.

Selective chemical dissolutions by consecutive treatments for; (1) the removal of free iron oxides, (2) gibbsite removal and (3) extractions of Fe and Al from kaolinite, give additional evidence about the occurrence of this solid solution.
Magnesium-ferric iron replacement in smectite during aeration of pyritic sediments
Authors: van Breemen N.
Published: December 2006

Chemical and mineralogical data on Holocene coastal plain soils from Thailand suggest that during formation of pyrite in tidal swamps Fe(III) is extracted from smectite and replaced by Mg. During drainage of these sediments pyrite oxidizes and the reaction is reversed. Replacing Fe(III) by Mg in clay minerals stores alkalinity that can neutralize three-quarters of the acidity released during oxidation of pyrite, and thus lowers the potential acidity of pyritic sediments. Possible causes for variation in the amounts of Mg taken up during pyrite formation are discussed.
Montmorillonite-asulam interactions: I. Catalytic decomposition of asulam adsorbed on H- and Al-Clay
Authors: Fusi P. , Ristori G. G. , Malquori A.
Published: December 2006

The adsorption of the Asulam herbicide (4-aminobenzensulphonyl-methyl-carbamate) by Al- and H-montmorillonite has been studied by IR spectroscopy, thin layer chromatography and chemical analysis. This compound is adsorbed from CCl4solution at room temperature through protonation of the NH2functional group by the ‘acidic’ water coordinated to the interlayer cation of the clay. After heating the complex at 75°C for 20 h, a hydrogen-bond between the C=O group of the Asulam and the water is established and the organic molecule decomposes to sulphanilic and carbamic acids. If the complex is equilibrated at 100% relative humidity, the carbamic acid becomes unstable, and the IR spectrum shows only the bands typical of the acidic montmorillonite-sulphanilic acid complex. The catalytic properties of the clay surface are demonstrated by comparison with the transformations occuring in the organic molecule on heating in concentrated mineral acids.
Clay mineralogy of a sequence of andesitic tephra beds of western Taranaki, New Zealand
Authors: Kirkman J. H.
Published: December 2006

The clay mineralogy of a sequence of 36 andesitic tephra and associated paleosols dating from 320 to > 100,000 years BP has been studied using XRD, IR, DTA and TEM techniques. The mineralogy and weathering sequence is compared with that of rhyolitic tephra of central North Island, New Zealand.
X-ray photoelectron studies of titanium in biotite and phlogopite
Authors: Evans S. , Raftery E.
Published: December 2006

X-ray photoelectron diffraction data from single crystals of a biotite containing ∼1% Ti show that although this element is located entirely in octahedral sites, the Ti sites are not precisely equivalent to those of Mg and Fe. Comparisons of Ti 2p X-ray photoelectron spectra from two biotites and from two titaniferous phlogopites (∼0·3–·5% Ti) with those from Ti(II), Ti(III) and Ti(IV) oxides indicate that this element is present as Ti(III) rather than Ti(IV) in all four micas.
Adsorption of alcohols by smectites: II. Role of the exchangeable cations
Authors: Annabi-Bergaya F. , Cruz M. I. , Gatineau L. , Fripiat J. J.
Published: December 2006

Calculations previously used to distinguish between methanol adsorbed in micropores between clay microcrystals (external) and that present in the interlamellar space (internal) of variable charge Ca-montmorillonites have been extended to homoionic Li-, Na- and Bamontmorillonites. It is shown that both the shape and the magnitude of the internal isotherms are in good agreement with X-ray diffraction data. Furthermore, the apparent molecular packing of methanol in the interlamellar space is related specifically to the nature of the charge balancing cation.
Adsorption of alcohols by smectites: III. Nature of the bonds
Authors: Annabi-Bergaya F. , Cruz M. I. , Gatineau L. , Fripiat J. J.
Published: December 2006

In previous papers of this series it was shown that it is possible to determine both the amount of methanol adsorbed in the interlamellar space of charge-deficient Ca-montmorillonite or of homoionic clays and the amount of methanol occluded in a system of micropores between clay particles. This paper deals with the distinction between methanol molecules in the cation coordination shell within the interlamellar space from those not directly influenced by the cation. An OH stretching band at about 3520 cm−1 or an OD stretching band in the 2600–2650 cm−1 region permits this distinction. At 35°C and at relative methanol vapour pressures between 0·1 and 0·9, one molecule of CH3OD is influenced directly by Na+, 2 molecules are influenced by Ba2+, 1·3–1·8 molecules by Li and 4 molecules by Ca2+. Thus, only 20–50% of the adsorbed alcohol molecules may be within the coordination shell of the cation in the interlamellar space.
Pedogenetischer Palygorskit in einem Lössprofil bei Stillfried an der March (Niederösterreich)
Authors: Schwaighofer B.
Published: December 2006

Kurzreferat

Im klassischen Lössprofil von Stillfried an der March wurden in der oberen Humuszone des Stillfrieder Komplexes Mineralbestand und Mikrogefüge mittels Röntgendiffraktometeranalyse und Rasterelektronenmikroskopie untersucht. In der Schluffund Tonfraktion fand sich neben anderen Tonmineralen Palygorskit, der vor allem in Form feinstrukturierter Mineralanhäufungen über Karbonatknollen auftritt.

Die charakteristische Morphologie der dünnstengeligen und faserförmigen Einzelkristalle sowie die Bildungsbedingungen bei alkalischem Milieu und hohem Mg-Gehalt der Bodenlösung sprechen für eine pedogenetische Neubildung des Palygorskit.
Synthese de peptides: Preparation de l'acide hippurique par reaction des complexes montmorillonite-glycine avec l'acide benzoique
Authors: Kessaissia S. , Siffert B. , Donnet J.-B.
Published: December 2006

En milieu organique, la formation de l'acide hippurique par contact d'un complexe montmorillonite-glycine avec de l'acide benzoīque est relativement facile. Dans ces conditions le peptide formé n'est pas hydrolysé. En milieu aqueux, par contre, l'activité catalytique de l'argile est insuffisante pour préparer l'acide hippurique à température ambiante. Une température minimale de 60°C est alors indispensable. Le rendement de la réaction qui est toujours faible dépend principalement de la nature du cation échangeable de l'argile. Les meilleurs résultats sont obtenus avec les montmorillonites contenant des éléments de transition tels que le cuivre, le nickel ou le zinc. Un phénomène d'activation faisant intervenir un complexe de coordination entre la glycine et le cation échangeable de l'argile constitue vraisemblablement l'étape intermédiaire dans la formation du peptide.
Factors influencing retention of lanthanide ions by montmorillonite
Authors: Bruque S. , Mozas T. , Rodriguez A.
Published: December 2006

A method for the preparation of Ln-montmorillonite (Ln = La, Ce, Sm, Gd, Er and Y) that ensures saturation of the CEC is described and the most favourable equilibrium conditions are discussed. The H+- Ln3+ exchange rate in acid montmorillonite and the effect of concentration and pH on the retention of Ln3+ ions by the clay are also investigated. The presence of montmorillonite modifies the pH value at which precipitation of hydroxides begins, a process that actually occurs at pH ∼ 5.
The behaviour of a synthetic57Fe-doped kaolin: Mössbauer and electron paramagnetic resonance studies
Authors: Cuttler A. H.
Published: December 2006

The thermal behaviour of a ferrous doped kaolin has been studied by Mössbauer spectroscopy and electron paramagnetic resonance spectroscopy. From the observations it is concluded that the iron substitutes trioctahedrally as Fe2+in the ‘gibbsite-like’ sheet in place of dioctahedral aluminium. The g = 2 EPR signal is shown to be associated with these ferrous ‘cells’ which appear to occur in clusters. It is suggested that these ferrous cells are trapped within the normal dioctahedral aluminium structure. Dehydroxylation of the ferrous iron cells takes place between 623 and 673 K leading to the formation of an iron-rich pyroxene and, by 723 K, a ferric oxide. At temperatures > 723 K the pyroxene itself oxidizes to a second ferric oxide. The EPR signal changes at 623 K and disappears at 723 K. The signal is attributed to a trapped hole induced by X-irradiation, located near a silicon atom on the boundary between normal dioctahedral cells and trioctahedral Fe2+cells. It is possible to extend the model to explain some puzzling features concerning the g = 2 EPR signals reported by other authors and to propose other effects which might result from the presence of these cells.
Swelling minerals in a basalt and its weathering products from Morvern, Scotland: I. Interstratified montmorillonite-vermiculite-illite
Authors: Bain D. C. , Russell J. D.
Published: December 2006

The main clay mineral in weathered basaltic rubble has been shown by X-ray diffraction, chemical, infrared and differential thermal methods to be an interstratification of montmorillonite, vermiculite and illite in the approximate ratio 2:1:1, the montmorillonite having some degree of segregation and the vermiculite and illite being randomly interstratified. All three components are dioctahedral, the swelling ones having a high tetrahedral charge, a large aluminium content, and very little iron. Despite the 50% montmorillonite content of the mineral, its infrared absorption pattern is generally illitic in character.
A mathematical model to distinguish the members of the dioctahedral smectite series
Authors: Brigatti M. F. , Poppi L.
Published: December 2006

Statistical (Q-mode) analysis of the chemical compositions of 122 dioctahedral smectites obtained from the literature have enabled the main solid solution ranges (montmorillonite, beidellite and nontronite) to be distinguished on a triangular diagram. In the montmorillonite area, the Wyoming, Tatatilla, Otay, Chambers and Non-Ideal montmorillonite compositional ranges are identified. Certain crystallochemical features of the smectites may be correlated with different genetic environments.
Regularly interstratified dioctahedral mica-smectite from Roseki deposits in Japan
Authors: Matsuda T. , Nagasawa K. , Tsuzuki Y. , Henmi K.
Published: December 2006

XRD, DTA, IR, chemical and electron microscopic data are presented for three specimens of regularly interstratified 25 Å minerals from Roseki deposits in Japan. The layer charges of these dioctahedral mica-smectites originate mainly from tetrahedral Al-for-Si substitution. The non-expandable interlayers are occupied by relatively large amounts of Ca and K as well as Na. The expansion characteristics of the expandable interlayers are montmorillonitic in spite of the beidellitic composition of the 2:1 layers.
Activación de una sepiolita con disoluciones diluidas de NO3H y posteriores tratamientos termicos: I. Estudio de la superficie específica
Authors: López González J. de D. , Ramírez Sáenz A. , Rodríguez Reinoso F. , Valenzuela Calahorro C. , Zurita Herrera L.
Published: December 2006

Una sepiolita procedente de Toledo (España) se ha activado por tratamiento con disoluciones 0·25, 0·50 y 0·75 n de NO3H, seguido de calentamiento durante 10 h a 110, 200, 300, 400 y 500°C. Para cualquier concentración ácida, un calentamiento de 110, 200 y, a veces, 300°C, produce un aumento del número de poros mientras que las temperaturas superiores significan un cierre de los mismos tanto mayor cuanto más elevada es la temperatura de tratamiento. El máximo desarrollo de la superficie accesible al N2 tiene lugar con una disolución 0·50 n de NO3Hy 200°C (449 m2/g, método de BET); la superficie específica de la sepiolita natural es de 321 m2/g.
Montmorillonite-Asulam interactions: II. Catalytic decomposition of Asulam adsorbed on Mg-, Ba-, Ca-, Li-, Na-, K- and Cs-clay
Authors: Ristori G. G. , Fusi P. , Franci M.
Published: December 2006

Asulam (p-aminobenzenesulphonylmethylcarbamate) is adsorbed by alkaline and alkaline-earth cation saturated montmorillonites at room temperature either by protonation or by physical forces. On heating it decomposes to different products depending on the polarizing power of the exchange cation. On Mg–clay, sulphanilic and carbamic acid are obtained; the latter decomposes after equilibration at 100% relative humidity. In Ba– and Ca–systems, sulphanilamide and sulphanilic acid are produced with minor amounts of p–aminobenzenesulphonylcarbamate anion. Sulphanilamide is the main decomposition product in Na–, K–and Cs–systems. On Li–clay, decomposition of the Asulam results in the formation of p–aminobenzenesulphonylcarbamate anion and p–aminobenzenesulphonylcarbamic acid, probably as a consequence of the intermediate polarizing power of this cation.
Mechanism of montmorillonite structure degradation by percussive grinding
Authors: Číčel Blahoslav , Kranz Günther
Published: December 2006

The processes taking place during decomposition of montmorillonite by percussive grinding have been studied by IR, X-ray and DTA methods. Destruction can be described as a series of parallel changes in the montmorillonite structure which proceed at various rates. The fastest is a change in status of the exchangeable cations followed by that of the hydroxyl groups. The slowest degradation process is the separation of tetrahedral and octahedral sheets. Degradation of the structure proceeds by delamination of particles, breaking of layers, crushing of layers by shocks perpendicular to the ab-direction, rearrangement of coordination polyhedra and transfer of protons within the structure. The relative importance of each of these processes is evaluated. It is assumed that the matrix resulting from complete breakdown of the montmorillonite structure consists mainly of the residue of tetrahedral sheets and deformed incomplete tetrahedra and octahedra, or of individual atoms held together in clumps either by Van der Waals forces or possibly, in some cases, by newly formed chemical bonds.
An occurrence of interstratified kaolinite-smectite minerals in a red-black soil toposequence
Authors: Herbillon A. J. , Frankart R. , Vielvoye L.
Published: December 2006

Interstratified kaolinite-smectite minerals form the major part of a pedon transitional between ‘red’ kaolinitic and black smectitic soils in a soil toposequence derived from basalt in Burundi, Central Africa. These interstratified kaolinite-smectites have many X-ray, morphological and chemical features in common with ‘tabular halloysite’. Modifications to the 00l spacings of these minerals brought about by thermal and chemical treatments, however, show that they are not halloysite but consist of a mixture of ∼70% kaolinite and 30% smectite randomly interstratified. Field evidence indicates that these clays can be considered as a transient stage in the overall reaction smectite→kaolinite + iron oxides, which takes place in this landscape whenever the slope gradients give rise to better drainage conditions.