scholarly journals The smectitic minerals in a bentonite deposit from Melo (Uruguay)

Clay Minerals ◽  
2003 ◽  
Vol 38 (1) ◽  
pp. 25-34 ◽  
Author(s):  
L. Calarge ◽  
B. Lanson ◽  
A. Meunier ◽  
M. L. Formoso
Keyword(s):  
Cation Exchange ◽  
Cation Exchange Capacity ◽  
Total Surface Area ◽  
Exchange Capacity ◽  
X Ray Diffraction ◽  
Interlayer Cation ◽  
Cation Composition ◽  
High Charge ◽  
X Ray ◽  
Diffraction Patterns

AbstractA nearly monomineralic 1.5 m thick bentonite bed sampled in Melo (Uruguay) appears to be a pure high-charge montmorillonite: [Si3.94Al0.06](Al1.40Fe3+0.11Ti0.02Mg0.49Mn0.01)O10 (OH)2Na0.01K0.08Ca0.18. However, contrasting swelling behaviours have been demonstrated by fitting the experimental X-ray diffraction patterns which were recorded on oriented preparations of the same sample in different saturation states. According to the expandability of the layers in the Ca-, K- and K-Ca-saturated (i.e. saturated first with K+ and subsequently with Ca2+) states, three ‘layer types’ were defined. Low-, intermediate-, and high-charge layers are fully, partly, and not expandable, respectively, after K-saturation. Collapse of high-charge layers is not reversible after subsequent Ca-saturation, probably because of tetrahedral substitutions. These three different layer types are segregated in two distinct randomly interstratified mixed-layer phases. Total surface area and cation exchange capacity are shown to depend on the interlayer cation composition.

Alteration of smectites induced by hydrolytic exchange

Clay Minerals ◽  
2005 ◽  
Vol 40 (1) ◽  
pp. 15-24 ◽  
Author(s):  
S. Ramirez ◽  
D. Righi ◽  
S. Petit
Keyword(s):  
Infrared Spectroscopy ◽  
Cation Exchange ◽  
Cation Exchange Capacity ◽  
Relative Increase ◽  
Exchange Capacity ◽  
Capacity Analysis ◽  
Soluble Salts ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mixed Layers

AbstractHydrolytic exchange was performed experimentally on four smectitic clays to evaluate the extent of clay alteration induced by this process and the associated ‘auto-transformation’ of H+ clays. Clay samples were Na-saturated and submitted to 10, 50 and 100 wetting-drying (WD) cycles and characterized after treatment using X-ray diffraction (XRD), infrared spectroscopy (FTIR) and cation exchange capacity analysis. Evidence for hydrolytic exchange was given by increasing amounts of exchangeable Mg2+ and precipitation of Na soluble salts for samples subjected to 100 WD cycles. Results indicated a decrease in the interlayer charge after 10 WD cycles but no further decrease was observed after 50 and 100 WD cycles. For one sample, XRD data indicated a decrease in the proportion of the smectite phase and a relative increase in the concentration of illite-smectite mixed layers also present in the sample. The results suggested that the reaction induces first a decrease in the layer charge and then a partial dissolution of some smectite layers.

scholarly journals Composition variation of illite-vermiculitesmectite mixed-layer minerals in a bentonite bed from Charente (France)

Clay Minerals ◽  
2004 ◽  
Vol 39 (3) ◽  
pp. 317-332 ◽  
Author(s):  
A. Meunier ◽  
B. Lanson ◽  
B. Velde
Keyword(s):  
Cation Exchange Capacity ◽  
Exchange Capacity ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hydration Behaviour ◽  
Composition Variation ◽  
Ash Layer ◽  
Diffraction Patterns ◽  
Aquitaine Basin ◽  
Low Charge

AbstractMineralogical and chemical variations were studied in the upper half of a 1 m thick discontinuous bentonite bed interlaminated in the Lower Cenomanian sedimentary formations of the northern Aquitaine basin (France). X-ray diffraction patterns obtained from the <2 mm fraction in the Ca and K-saturated states were decomposed and compared to those calculated from decomposition parameters. They revealed the presence of two highly expandable illite-expandable (I-Exp) mixedlayer minerals (MLMs). The relative proportions of the two MLMs evolve steadily with depth leading to the decrease of the cation exchange capacity and of the (Na + Ca) content towards the centre of the bentonite bed. However, the system is essentially isochemical and Mg, Al, Si, K and Fe are roughly constant in the bulk samples. It is thought that the mineralogical zonation results from the initial stages of the smectite formation in an ash layer.In the Ca-saturated state, the expandable component of these MLMs was for the most part homogeneous with the presence of 2 sheets of ethylene glycol molecules in the interlayer. However, the heterogeneous hydration behaviour of these expandable layers was enhanced by the K-saturation test. From this test, the presence of three layer types with contrasting layer charge was evidenced from their contrasting swelling abilities. The C12-alkylammonium saturation test applied to samples in which the octahedral charge had previously been neutralized (Hofmann-Klemen treatment) showed that the tetrahedral charge is located on specific layers. These layers are responsible for the heterogeneous hydration behaviour. Low-charge smectite layers are mostly octahedrally substituted, whereas for intermediate- and high-charge layers this montmorillonitic charge is complemented by additional tetrahedral substitutions (0.30 and 0.35–0.40 charge per O10(OH)2, respectively).

Influence of Alkaline Activation over Swelling and Cation Exchange Capacity on Bentonites

2010 ◽  
Vol 660-661 ◽  
pp. 1064-1069 ◽  
Author(s):  
Jeane A. Rosário ◽  
Laura A. Silva ◽  
Gabriel Beraldi G. Moura ◽  
Marivone Gusatti ◽  
Raquel B. Lima ◽  
...  
Keyword(s):  
Cation Exchange ◽  
Cation Exchange Capacity ◽  
Sodium Content ◽  
Exchange Capacity ◽  
X Ray Diffraction ◽  
X Ray ◽  
Different Types ◽  
Methylene Blue Test ◽  
Bentonite Clays ◽  
Mechanochemical Reactions

The performance of the alkaline processes on the properties of cation exchange capacity (CEC) and swelling was studied in three different types of bentonite from Brazil, Argentina and Mozambique. Alkaline activations were performed by means of mechanochemical reactions with solutions of NaOH and Na2CO3, to increase the sodium content of bentonite clays and, thus, improve the properties above. Clay samples were characterized by X-ray diffraction, to obtain the constituent phases. Activated samples were evaluated according to their cation exchange capacity – determined by the methylene blue test, and swelling index – measured by the Foster’s method. Results showed that the activation improved the properties of all bentonite types, especially the Brazilian clay, which achieved the most significant raises. There was also an indication that the type of clay affect the processing.

Powder x-ray diffraction study of a cryptomelane-type manganic acid and its alkali cation exchanged forms

1993 ◽  
Vol 8 (12) ◽  
pp. 3145-3150 ◽  
Author(s):  
Masamichi Tsuji ◽  
Sridhar Komarneni
Keyword(s):  
Cation Exchange ◽  
Cation Exchange Capacity ◽  
Lattice Parameter ◽  
Exchange Capacity ◽  
Alkali Cation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Steep Decrease ◽  
Exchange Properties ◽  
Good Agreement

Cryptomelane-type manganic acid (CMA), H2Mn8O16 · 2.4H2O, with a theoretical cation exchange capacity of 2.70 meq/g, was prepared and its cation exchange properties were studied as a function of XM which is defined by the ratio of uptake in meq/g to the theoretical capacity. Plots of the corrected selectivity coefficients log KHM vs the fractional exchange M for alkali metal ions on a 2 × 2 type tunnel-structured manganic acid showed a gradual decrease in small XMM regions and a steep decrease in large XMM) were 0.92 for Li+, 0.74 for Na+ and K+, 0.67 for Rb+, and 0.44 for Cs+. These maximums have been attributed to steric limitation as well as a limit on the expansion of the crystal lattice. Some x-ray diffraction (XRD) data of alkali cation exchanged forms were in good agreement with the XRD data of synthetic alkali CMA phases as given in the cards by the Joint Committee on Powder Diffraction Standards (JCPDS). The lattice parameter a0 has been found to depend on the exchanged amounts and the nature of the cations involved, while the c0 value remained almost the same irrespective of the amount of exchange or the nature of the cations.

Organo-bentonites with improved cetyltrimethylammonium contents

Clay Minerals ◽  
2014 ◽  
Vol 49 (5) ◽  
pp. 683-692 ◽  
Author(s):  
F. Kooli
Keyword(s):  
Cation Exchange ◽  
Cation Exchange Capacity ◽  
Interlayer Spacing ◽  
Exchange Capacity ◽  
Organic Cations ◽  
Basal Spacing ◽  
Water Mixture ◽  
X Ray Diffraction ◽  
X Ray

AbstractOrgano-bentonites were prepared using a bentonite and an aqueous cetyltrimethylammonium hydroxide solution. The ratio of the surfactant (in mmoles) to the cation exchange capacity varied from 0.5 to 20, with 20 being the highest ratio ever reported in the literature. At high surfactant to cation exchange capacity ratios, the interlayer spacing increased to 3.75 nm due to the formation of a paraffin-type bilayer of surfactant cations, which was shown to be mainly in gauche conformations using solid state 13C CP/NMR. When the exchange reaction was carried out in a methanol-water mixture, the expansion of the organo-bentonites depended on the concentration of methanol (% by volume). The decomposition temperatures of the organic cations depended on the basal spacing of the organo-bentonites, and in situ X-ray diffraction revealed that the basal spacing of our organo-bentonites was stable up to 210°C. Above this temperature, the basal spacing shrunk to 1.47 nm due to decomposition of the surfactants.

REACTIONS OF PHOSPHATE WITH ALUMINUM AND WYOMING BENTONITE

1969 ◽  
Vol 49 (2) ◽  
pp. 231-240 ◽  
Author(s):  
M. D. Webber ◽  
J. S. Clark
Keyword(s):  
Cation Exchange ◽  
Cation Exchange Capacity ◽  
Major Part ◽  
Aluminum Phosphate ◽  
Exchange Capacity ◽  
X Ray Diffraction ◽  
X Ray ◽  
Aluminum Complexes ◽  
Phosphate Phase ◽  
Wyoming Bentonite

Reactions between phosphate, Al and Wyoming bentonite in aqueous suspensions were studied under two conditions: (1) H3PO4 was added after interlayer hydroxy aluminum complexes had been formed by the addition of Ca(OH)2 to AlCl3 + bentonite suspensions; and (2) H3PO4 was added to AlCl3 + bentonite suspensions before the addition of Ca(OH)2. The suspensions were aerated and maintained at 25 °C.When H3PO4 was added after the formation of hydroxy aluminum complexes, the results were not significantly different from those when Ca(OH)2 was added to suspensions containing both AlCl3 and H3PO4. Phosphate was removed from solution and an interlayer hydrous aluminum phosphate was formed which increased the d(001) spacings of the bentonite. The amount of phosphate removed from solution increased to a maximum with increasing amounts of H3PO4 added and over this range there was no change in cation exchange capacity (CEC). Large amounts of H3PO4 increased the CEC of the bentonite. A major part of the reaction was completed within 24 hours and the values of pH changed only slightly from 1 to 120 days.Values of the (Al) (OH)2(H2PO4) ion product measured after aging for 14 days were larger than would have been maintained by crystalline variscite, but X-ray diffraction studies showed no evidence for formation of a separate crystalline phosphate phase.

Characteristics of variably saturated granular bentonite after long-term storage at near-field relevant temperatures

Clay Minerals ◽  
2013 ◽  
Vol 48 (2) ◽  
pp. 343-361 ◽  
Author(s):  
M. Valter ◽  
M. Plötze
Keyword(s):  
Physicochemical Properties ◽  
Cation Exchange ◽  
Surface Area ◽  
Cation Exchange Capacity ◽  
Elevated Temperatures ◽  
Near Field ◽  
Exchange Capacity ◽  
Hydraulic Permeability ◽  
Cation Composition ◽  
Retention Capacity

AbstractBentonite is a potential material for use in the engineered barrier of radioactive waste repositories because of its low hydraulic permeability, self-sealing capability and retention capacity. It is expected that bentonite would react at the elevated temperatures accompanying the radioactive decay in the nuclear waste. The presented study was started in order to improve understanding of the coupled influence of temperature and (pore) water on the physicochemical and mineralogical properties of bentonite during thermal treatment under near-field relevant conditions. Granular Na-bentonite MX-80 was differently saturated (Sr = 1–0.05) and stored at different temperatures (50–150°C) in a closed system. Upon dismantling after different periods of time (3 to 18 months), mineralogical characteristics, cation exchange capacity and content of leachable cations, as well as physicochemical properties such as surface area and water adsorption were investigated.The results showed a high mineralogical stability. A slight conversion from the sodium to an earth alkali form of the bentonite was observed. However, considerable changes in the physicochemical properties of the bentonite were observed, particularly by treatment above the critical temperature of 120°C. The cation exchange capacity decreased during heating at 150°C by approximately. 10%. The specific surface area dropped by more than 50%. The water uptake capacity under free swelling conditions showed a slight tendency to lower values especially for samples heated for more than 12 months. The water vapour adsorption ability in contrast drops by 25% already within three months at T = 120°C. These changes are mostly related to the variations in the interlayer cation composition and to smectite aggregation processes. The observed alterations are rather subtle. However, temperatures ⩾ 120°C had a remarkable negative influence on different properties of MX-80.

A lithium-bearing aluminian regular mixed layer montmorillonite-chlorite from Huy, Belgium

Clay Minerals ◽  
1974 ◽  
Vol 10 (3) ◽  
pp. 135-144 ◽  
Author(s):  
G. Brown ◽  
P. Bourguignon ◽  
J. Thorez
Keyword(s):  
Mixed Layer ◽  
Cation Exchange Capacity ◽  
Structural Formula ◽  
Exchange Capacity ◽  
X Ray Diffraction ◽  
X Ray ◽  
Saturated Clay ◽  
Bluish Green ◽  
Image Position ◽  
Green Clay

AbstractA bluish-green clay found in veins cutting across brecciated slates of the Llanvirnian stage at Huy, Belgium, is shown by X-ray diffraction and chemical analysis to be a lithium-bearing, aluminium-rich, regular mixed layer montmorillonite-chlorite with associated pyrophyllite, nacrite and quartz and smaller amounts of calcite and ankerite. The cation exchange capacity of the purified air-dry magnesium saturated clay is 49 mEq/100 g and its structural formula isThe problem of the nomenclature of regular mixed layer montmorillonite-chlorites is discussed.

SEM, XRF, XRD, Nitrogen Adsorption, Fosters Swelling and Capacity Adsorption Characterization of Cloisite 30 B

2012 ◽  
Vol 727-728 ◽  
pp. 1591-1595 ◽  
Author(s):  
Aline Cadigena Lima Patrício ◽  
Marcílio Máximo da Silva ◽  
Anna Karoline Freires de Sousa ◽  
Mariaugusta Ferreira Mota ◽  
Meiry Glaúcia Freire Rodrigues
Keyword(s):  
Quaternary Ammonium ◽  
Cation Exchange Capacity ◽  
Nitrogen Adsorption ◽  
Exchange Capacity ◽  
X Ray Diffraction ◽  
Oil And Grease ◽  
X Ray ◽  
Quaternary Ammonium Cations ◽  
Cloisite 30B

Cationic surfactants, such as quaternary ammonium cations, have been used, in order to ameliorate the oil sorption capacity of inorganics materials, such as clays. Clays modified with quaternary ammonium cations (organoclays) have better performance in sorption, remove oil and grease from water at seven times the rate of activated carbon, as well as they can be used like perforation fluids of oil wells to the oil base, lubricants, among others industries. This work aims characterize the Cloisite 30B using various techniques: X-Ray Diffraction (XRD), Specific Surface Area (BET) and Cation Exchange Capacity. Different organic solvents, namely gasoline, diesel and kerosene were used in order to investigate the clays compatibility after orgophilization.

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