Aluminum Montmorillonite Research Articles

The sorption ability of humic acids of black alder fen peat on montmorillonite containing clays in the presence of heavy metal ions

It is determinate that the adsorption of humic acids by the different forms of montmorillonite increases with a decrease in pH. Maximum adsorption of humic acids is observed in the presence of zinc ions, which is associated with the formation of chelate complexes of humic acids with zinc ions. Organic mineral systems based on humic acids of black alder fen peat and aluminum montmorillonite form observe maximum adsorption of lead and zinc ions, which is associated with an increase in their specific surface and adsorption capacity, due to the formation of a layered-columnar structure and slit-shaped micropores.

Modified Rapeseed Oil/Al-Montmorillonite Composite Material: Preparation and Application in Leather Collagen

In this study, montmorillonite (MMT) was modified by aluminium sulfate via ions exchange method and aluminium-montmorillonite (Al-MMT) was obtained. Al-MMT was characterized by X-ray diffraction (XRD) and thermo gravimetric analysis (TGA). The results indicated that the interlayer spacing of MMT increased from 1.26 nm to 1.55 nm after being modified by Al3+. Then Al-MMT was introduced to modified rapeseed oil by an in-situ method. The results of TGA and XRD indicated that modified rapeseed oil (MRO) could smoothly enter the interlayer of Al-MMT and modified rapeseed oil/Al-montmorillonite (MRO/Al-MMT) composite material was prepared successfully. Finally, MRO/Al-MMT composite material was applied in the leather fatliquoring process of goatskin garment. Physical and mechanical properties and flame retardant performance of leather fatliquored by MRO/Al-MMT composite material were improved compared with those of leather fatliquored by MRO. And MRO/Al-MMT composite material was easily biodegradable compared with MRO.

Comparison of Adsorption of Phosphate, Tartrate, and Oxalate on Hydroxy Aluminum Montmorillonite Complexes

AbstractCompetitive adsorption between phosphate, tartrate and oxalate was studied on two hydroxy aluminum montmorillonite complexes (AlMt1.6 and AlMt6), which were prepared by adding a base to pH 5.5 to samples containing 1.6 and 6.0 mol Al per kg clay. The quantities of phosphate, tartrate and oxalate adsorbed were more closely related to the amount of OH-Al species coatings on the montmorillonite than to the surface area of the complexes. The adsorption capacity of phosphate was much greater than that of tartrate or oxalate for both samples. Adding molar amounts of oxalate and tartrate resulted in an oxalate/tartrate adsorption ratio (Rf) of ∼1. However, in the presence of phosphate, Rf values were <1.0, and the Rf values decreased with increasing amounts of added phosphate, indicating that tartrate competed with phosphate more effectively than oxalate. The presence of tartrate also reduced phosphate adsorption by the complexes. The efficiency of tartrate in reducing phosphate adsorption increased by increasing the initial tartrate/phosphate molar ratio and by adding tartrate 2 h before phosphate addition. Tartrate and oxalate added as a mixture in equimolar quantities were much more effective in inhibiting phosphate sorption than tartrate alone under the same organic ligand concentrations, probably because more sites with high affinity for both the organic ligands were occupied by tartrate and oxalate than by tartrate alone. The efficiency of tartrate alone, or combined with oxalate, in preventing phosphate adsorption was greater for the complex containing a lesser amount of OH-Al species coating the montmorillonite surfaces. This result may be attributable to a greater proportion of sites specific for organic ligands present on AlMt1.6 compared to AlMt6 complex.

Adsorption-desorption of 2,4-D by hydroxy aluminium montmorillonite complexes

Adsorption–desorption characteristics of 2,4-dichlorophenoxyacetic acid (2,4-D) on pure montmorillonite and synthetic chlorite-like complexes [Al(OH)x-montmorillonite complexes, obtained by coating montmorillonite surfaces with different amounts of Al(OH)x] were investigated. The equilibrium adsorption of 2,4-D was described by both Langmuir and Freundlich type isotherms. The extent of adsorption as well as the type of interaction between adsorbate and adsorbent was affected by the nature of incubation buffer and the charge characteristics of supports. At pH 5·6 and in acetate buffer, 2,4-D was negatively adsorbed by montmorillonite and herbicide adsorption capacity increased with increasing amounts of Al(OH)x species loaded on montmorillonite surfaces. When adsorption experiments were performed at the same pH but in phosphate buffer, strong reductions of both the amount of adsorbed pesticide and its affinity for the adsorbents were measured. Evidently, phosphate anions competed strongly with 2,4-D anions for the sorption site on chlorite-like complexes. Furthermore, desorption tests revealed that a large amount (about 60%) of the pesticide was firmly bound to the clay and was not removed even after repeated washings or 24 h exposure to desorption solution. Both electrostatic interactions between the negative COO- moieties of 2,4-D and the positive sites on clays, and ligand exchanges of COO- groups with -OH or water at the clay surface were probably involved in the adsorption process. ©1997 SCI

Adsorption–desorption of 2,4-D by hydroxy aluminium montmorillonite complexes

Adsorption–desorption characteristics of 2,4-dichlorophenoxyacetic acid (2,4-D) on pure montmorillonite and synthetic chlorite-like complexes [Al(OH)x-montmorillonite complexes, obtained by coating montmorillonite surfaces with different amounts of Al(OH)x] were investigated. The equilibrium adsorption of 2,4-D was described by both Langmuir and Freundlich type isotherms. The extent of adsorption as well as the type of interaction between adsorbate and adsorbent was affected by the nature of incubation buffer and the charge characteristics of supports. At pH 5·6 and in acetate buffer, 2,4-D was negatively adsorbed by montmorillonite and herbicide adsorption capacity increased with increasing amounts of Al(OH)x species loaded on montmorillonite surfaces. When adsorption experiments were performed at the same pH but in phosphate buffer, strong reductions of both the amount of adsorbed pesticide and its affinity for the adsorbents were measured. Evidently, phosphate anions competed strongly with 2,4-D anions for the sorption site on chlorite-like complexes. Furthermore, desorption tests revealed that a large amount (about 60%) of the pesticide was firmly bound to the clay and was not removed even after repeated washings or 24 h exposure to desorption solution. Both electrostatic interactions between the negative COO- moieties of 2,4-D and the positive sites on clays, and ligand exchanges of COO- groups with -OH or water at the clay surface were probably involved in the adsorption process. ©1997 SCI

Phosphate sorption by hydroxy-aluminium and hydroxy-iron (III) treated montmorillonites

Hydroxy aluminium montmorillonite and hydroxoacetatotris iron (III) montmorillonite were prepared and were studied as phosphate sorbents. These materials had lower Ba exchange capacities than the original clay, developed pH dependent charges, gave rise to reduced X-ray diffraction peaks, developed a high capacity for phosphate sorption and the sorption became pH dependent. The phosphate isotherm of Al-treated clay appeared as two connected isotherms, and phosphate sorption was accompanied by K uptake but without pH changes. A model based on a ligand exchange reaction involving phosphate anions and two types of hydroxyls was used to explain the results.

High conversion and selectivity for cracking of n-heptane on cerium–aluminium montmorillonite catalysts

The synthesis and catalytic properties of an aluminium pillared clay modified by inclusion of cerium are described; very high catalytic activity and selectivity for the cracking of n-heptane are observed.

Differences in reactivities of sedimentary hopane diastereomers when heated in the presence of clays

Mixtures of hopane diastereomers obtained by fractionation of the organic extract from an immature oil shale have been heated in the presence of clay-containing substrates. In experiments conducted at 250°C with an extracted source rock as the substrate, the relative amounts of 17β(H),21β (H)-hopanes were found to decrease with respect to the moretanes and 17α(H),21β(H)-hopanes in a manner parallelling that observed with increasing maturity in sediments. In this case however, the change was shown to be due to the selective removal of the 17β(H),21β(H)-hopanes, rather than conversion of these compounds into the other diastereomers. In order to assess whether the use of elevated temperatures was enhancing processes other than those which operate in natural systems, a second experiment was conducted in which the sample of immature hopanes was heated at 75°C with the very catalytically active substrate aluminum montmorillonite. In this experiment also, the changes in hopane composition was shown to be due to selective removal of 17β(H),21β(H)-hopanes rather than conversion into the corresponding compounds in the other two series of diastereomers. These results suggest that the observed relative depletion of 17β(H),21β(H)-hopanes in sedimentary rocks of increasing maturity may similarly be due to removal by selective catalytic processes, and not to interconversion processes associated with isomerisation at C-17 and C-21 as had previously been believed.

PH‐Dependent Boron Adsorption by Montmorillonite Hydroxy‐Aluminum Complexes

AbstractBoron adsorption by hydroxy aluminum and by hydroxy aluminum montmorillonite complexes was determined as a function of pH and boron concentration in solution. Data from both experiments were compared with results computed according to the fitted adsorption coefficient. The agreement between calculated values and experimental results indicates that the phenomenological equation suggested by Keren et al. (1981) can be used in a modified form to predict boron adsorption on hydroxy aluminum as a function of both the boron concentration and the pH. Boron adsorption by both the physical and chemical mixtures (hydroxy aluminum and montmorillonite) was greater than by montmorillonite alone, with the physical mixture adsorbing the largest amount of boron.

Dielectrophoresis in clay syspensions

An alternating, non-uniform electric field applied to suspensions of sodium, hydrogen, and aluminium kaolinites, aluminium montmorillonite, and aluminium bentolite, caused water to flow towards the more intense part of the field. The flow rates were generally proportional to the square of the voltage, the proportionality factor being greater for subsequent applications of the voltage. This appears to be the first demonstration of dielectrophoretic dewatering of aqueous dispersions. The rather weak dielectrophoretic effect increased for more strongly bound cations, whereas the much stronger electroosmotic effect (measured in the same apparatus using a direct voltage) decreased. Dielectrophoresis arises from the surface polarisation of elastically bound cations in the electric double layer, while relatively free cations are responsible for conductivity and electroosmosis. Only in the case of aluminium bentolite, where the clay particles were probably coated with positively charged hydroxy-aluminium species, was the dielectrophoretic effect appreciable compared with electroosmosis.

Degradation of adsorbed atrazine on an aluminum montmorillonite

Degradation of adsorbed atrazine on an aluminum montmorillonite

Stability of silver–thiourea complexes in montmorillonite clay

Ion exchange adsorption of a silver–thiourea complex into sodium-, calcium- and aluminum montmorillonite at 25°C has been studied. The reversible nature of the reaction is demonstrated and the standard free energy changes for the displacement of the three ions by the silver complex are calculated. The results are, in kJ equiv.–1: –20 (Na–Ag), –20.7 (Ca–Ag) and –19 (Al–Ag). These values are consistent with values for Na–Ca and Ca–Al exchanges, found in the literature. The free energy loss for adsorption of the silver complex exceeds that for the aqueous ion by some 19 kJ equiv.–1 The enhancement of the selectivity and the coordination values of adsorbed silver ions are consistent with the following free energy changes for the successive formation of the complexes: ΔG1=–59.5, ΔG1→2=–20.3 and ΔG2→3=–7.4 kJ mol–1. Relative to the free energies of formation of these complexes in solutions, these values correspond to stabilization of the complex containing one thiourea molecule and destabilization of that containing three.

Adsorption of Polysaccharides by Montmorillonite

AbstractAmylose and a dextran of MW 2 million were adsorbed by montmorillonite. However, two dextrans of lower MW did not adsorb on montmorillonite. It is suggested that entropy changes arising from changes in configuration of the macromolecules and the association of water molecules with clay and polymer control the adsorption behavior of uncharged polysaccharides. Poly (galacturonic acid) was adsorbed by aluminum montmorillonite but showed negative adsorption on sodium montmorillonite. The uronic acid components of a soil polysaccharide were adsorbed by montmorillonite if aluminum ions or hydroxy aluminum species were present on the clay; neutral sugar components were adsorbed irrespective of the exchangeable cations present or the pH.

Thixotropy and dilatancy

AbstractThe matric potential of water in gels of five-sixths neutralized aluminium montmorillonite (bentonite) and aluminium kaolinite changes during periods of shear and periods of rest. Shear increases the potential of water in bentonite gels, and in kaolinite gels containing little water, but decreases the potential in kaolinite gels containing more water. All these effects can be explained by changes in the curvature of water films at the gel-air interface. The difference between thixotropic and dilatant behaviour is the increasing and decreasing of the water potential on shearing. In dilatant pastes of silt-size particles, and for which the effects of electric charges are small, the pressure deficiency can reach large values after an increase in pore space, and this suffices to explain the characteristic features of dilatant behaviour.

A contribution on the Hector, California bentonite deposit

The unique Hector bentonite occurs along a northwest-trending fault zone for a distance of about five miles. Hot springs emanating along this fault during Pliocene (?) time deposited travertine in a then existing lake in which sand, marl and silicic pyroclastics also were being deposited. The tuff lying on the travertine benches was altered to saponite by solutions containing lithium and fluorine in the last stages of hot spring activity, with the magnesium being extracted from the lake water. Analcime, representing alteration of the tuff when the springs were inactive, is found below and above the bentonite bed. Clinoptilolite is present directly associated with the hot spring activity.The amount of travertine decreases to the northwest as do the contents of lithium, fluorine, and magnesium in the clay, which approaches an aluminum montmorillonite in composition. In a restricted basin where magnesium is available, acid solutions from hot springs apparently produce a chemical system that forms a trioctahedral bentonite preferentially to a dioctahedral variety even though the parent material approximates the chemical composition of an aluminum montmorillonite.Minor faulting and slumping have produced gouge zones and small downward displacements of the irregular bentonite lenses on the southwest side of the main fault. The deposit is located in a valley of low relief; the dominant structural feature is the high, developed by the deposition of sediments and pyroclastics on the travertine benches. River gravels and muds, and a basalt flow in places, unconformably overlie the series.