Pure Clay Minerals Research Articles

Insecticidal Activity of the Toxins from Bacillus thuringiensis subspecies kurstaki and tenebrionis Adsorbed and Bound on Pure and Soil Clays

The release of transgenic plants and microorganisms expressing truncated genes from various subspecies of Bacillus thuringiensis that encode active insecticidal toxins rather than inactive protoxins could result in the accumulation of these active proteins in soil, especially when bound on clays and other soil particles. Toxins from B. thuringiensis subsp. kurstaki and B. thuringiensis subsp. tenebrionis, either free or adsorbed at equilibrium or bound on pure clay minerals (montmorillonite or kaolinite) or on the clay size fraction of soil, were toxic to larvae of the tobacco hornworm (Manduca sexta) and the Colorado potato beetle (Leptinotarsa decemlineata), respectively. The 50% lethal concentrations (LC(inf50)) of free toxins from B. thuringiensis subsp. kurstaki were higher than those of both bound and adsorbed complexes of these toxins with clays, indicating that adsorption and binding of these toxins on clays increase their toxicity in diet bioassays. The LC(inf50) of the toxin from B. thuringiensis subsp. tenebrionis that was either free or adsorbed on montmorillonite were comparable, whereas the toxin bound on this clay had higher LC(inf50) and the toxin bound on kaolinite had lower LC(inf50) than when adsorbed on this clay. Results obtained with the clay size fraction separated from unamended soil or soil amended with montmorillonite or kaolinite were similar to those obtained with the respective pure clay minerals. Therefore, insecticidal activity of these toxins is retained and sometimes enhanced by adsorption and binding on clays.

Vibratory Extraction of Clay Fines from Subsurface

This paper presents results from laboratory investigations on utilizing ultrasonic and subsonic vibrations to facilitate removal of fine clay particles from the subsurface. A sonicator and a laboratory vibrator were used to vibrate mixtures of sand and pure clay minerals as well as a sample of natural soil from New Jersey. In column experiments, particle extraction resulted in an enhancement in the hydraulic conductivity. Effluent slurries from kaolinite mixtures contained more fine particles than those from montmorillonite mixtures. When subsonic vibrations were applied after ultrasonic treatment, additional quantities of fines were extracted. Abrasion and/or fracturing of sand‐ and silt‐sized grains occurred near the vibrating source. The formation of low‐permeability layers because of particle migration and accumulation may have occurred in the experiments. Experiments conducted in 90‐cm‐ and 120‐cm‐diameter tanks showed that the zone of influence of vibrations extended as far as the tank walls. These results suggested that in‐situ implementation of localized vibrations to enhance hydraulic conductivity of clayey soils, and to facilitate controlled mobilization of clay fines and the associated contaminants, may be feasible.

Clay dispersion as influenced by pH and net particle charge of sodic soils

The effect of changing pH on the dispersion of clay from sodic soils was investigated in relation to changes in net charge on clay particles. A positive relationship was obtained between pH and the percentage of dispersible clay for each soil clay. The percentage increase in net negative charge was also positively correlated with pH. However, the slopes of these relationships varied between soil clays. In general, the net negative charge was the primary factor in clay dispersion and the pH affected clay dispersion by changing the net charge on clay particles. In comparing the values for pure clay minerals quoted in the literature with soil clays having similar mineralogy, it was found that soil clays had higher flocculation values. This is shown to be due to higher net negative charge on soil clays than the corresponding values for pure clay minerals found in the literature. The effect of soil organic matter in enhancing the net negative charge probably contributes to the higher charge on soil clays. The critical dispersion concentration for clay dispersion from soil aggregates was lower than the flocculation values observed for the separated soil clays. The separated soil clays had high negative charge due to exposure of surfaces which were originally bonded in the aggregates. The dispersive potential of a number of Alfisols, Oxisols, Aridisols (calcareous soils) and Vertisols collected from different parts of Australia was highly correlated with soil pH. The relationship with CEC was poor because CEC was estimated at a pH different to the natural pH of the soil. This study has brought out the importance of pH in the management of dispersive soils.

Mechanisms determining separation of phosphatic clay waste by selective flocculation

An accurate knowledge of the interactions among mineral particles and between such particles and dissolved and precipitated species is important in developing efficient separation processes. In this investigation, interactions relevant to dispersion and selective reagent adsorption (the two main prerequisites for selective flocculation) within Florida phosphatic clay waste were studied. Initial studies with artificial slimes, consisting of pure clay and phosphate minerals, showed dispersion of artificial slimes to be relatively easy. The problems that were encountered during selective flocculation of the artificial slimes were due to unselective polyacrylic acid adsorption on clay, which was caused by the presence of multivalent calcium ions on the exchangeable cation positions on the clay surfaces. This problem could be solved by exchanging calcium for sodium, which reduces the interaction between the polymer and the clay surface. This procedure, however, was not successful for mineral mixtures. Natural slimes were found to be much more difficult to disperse. This was attributed to the presence of cementing materials such as humic substances and Al and Fe (hydr)oxide precipitates. Selective removal of these cementing materials resulted in good dispersion and partial separation. A further increase in the separation of natural slimes is most likely determined by the presence of calcium on the clay surfaces, as was found for the artificial mixtures.

Ammonium fixation by soil and pure clay minerals

Abstract Fixation of the ammonium ion (NH4 +) by clay minerals is an alternate way of building the nitrogen (N) pool in soil to optimize N crop recovery and minimize losses. Clay minerals (illite, montmorillonite, and vermiculite) and an illitic Portnoeuf soil were used to compare NH4 + fixation abilities. Total N determination and X‐ray diffraction analysis were performed on each of the minerals and the Portnoeuf soil controls, and NH4 + saturated batches were subsequently desorbed by potassium chloride (KCl) after 4096 hours. Total N was determined for each employing either Kjeldahl digestion only, or pretreating with hydrofluoric‐hydrochloric acid (HF‐HCl) before the Kjeldahl digestion. The total N for the soil was 38% more after pretreatment with HF‐HCl. The total N determined after pretreatment with HF‐HCl for the NH4 + saturated and subsequently KCl desorbed minerals was found to be highest in vermiculite. The cation exchange acapacity (CEC) of each of the minerals was determined, and highest CEC wa...

Acid Neutralization by Gulf Coast Sediments

AbstractThe capacity of sandstone to neutralize injected acid was determined for material from a waste disposal well in Jefferson Parish, Louisiana. Injection zone sandstone was found to neutralize approximately 1.51×10−3 grams H+ ions per gram of sand. Kinetics parameters were determined for reactions of acid with confining layer shale material. Reaction rate coefficients and activation energies of acid‐shale systems agree with values previously determined for reactions of acids with relatively pure clay minerals.

Selenite fixation by soil particle‐size separates

SUMMARYThe fixation of selenite by clay‐ (< 2 μm), silt‐ (2–20 μm) and sand‐size (20–2000 μm) separates from two arable soils was examined in solutions of 75Se‐labelled sodium selenite using a Se/sample ratio of 1/106. Size separates were isolated by ultrasonic dispersion and gravity sedimentation. Selenite fixation was determined after equilibration periods ranging from 5 min to 26 h. Hydrogen peroxide‐treated samples were included to examine the effect of organic matter on selenite fixation capacity.The relative distribution of native Se, C, dithionite/citrate‐extractable Fe and Al between size separates was similar. Concentrations in clay were four to nine times higher than in whole soils, silt showing two to five times higher concentrations and sand being very low in Se, C, Fe and Al.After 1 h, clay, silt and sand fixed 64–65%, 45–61% and <5% of the selenite added, respectively. The fixation on whole soils was 14–18%. After 1 day, fixation on clay, silt, sand and whole soil increased to 78–87%, 67–79%, 3–14% and 31–39%, respectively.Hydrogen peroxide‐treatment reduced the selenite fixation capacity of whole soil, silt and sand to very low levels. Fixation on peroxide‐treated clay was in accord with values for pure clay minerals reported in the literature. Generally, the fixation capacity of peroxide‐treated natural clay and pure clay minerals was only half that observed for intact clay‐size separates, demonstrating the importance of organic matter in soil selenite fixation capacity.

EXCHANGE AND APPARENT FIXATION OF LITHIUM IN SELECTED SOILS AND CLAY MINERALS

Relatively few data exist on the exchange reactions of Li in soils; rather, the bulk of the literature has dealt with simple ion exchange reactions on ideal exchangers, usually synthetic resins or pure clay minerals. Occasional observations of anomalous exchange of Li have been reported, without any

Temperature and pH controls over isotopic fractionation during adsorption of boron on marine clay

The variation of adsorption constants and isotope fractionation with pH and temperature during the adsorption of B from seawater onto marine clay have been examined. The controls over adsorption are similar to those exhibited by pure clay minerals ( Bassett, 1976; Keren and Mezuman, 1981). The isotope fractionations are the result of equilibrium processes, not kinetic effects. Variations in the measured fractionation factor with pH arise from the differences between the isotope fractionation associated with adsorption of B(OH) 3 and B(OH) 4 − and the pH dependence of B speciation. The implications of these results for the distribution of B isotopes in seawater and sediment porewaters are briefly discussed.

Role of the mineral matrix during kerogen pyrolysis

Much is known about the important interactions existing, during pyrolysis of rocks, between minerals and the hydrocarbon compounds coming from the cracking of organic matter (kerogens). Clay minerals have been shown to be the most active in “retaining” the heaviest hydrocarbon compounds and in promoting their coking as the temperature rises. Under pyrolysis conditions of the Rock-Eval type, this paper investigates the interactions between different pure clay minerals and the hydrocarbons coming from the cracking of an organic matter of marine origin (type II). For this, different methods were used to analyse the volatile compounds issuing from pyrolysis (hydrocarbons, hydrogen, CO 2, CO) and the carbon residues coming from the hydrocarbon compounds retained on the minerals. These methods included gas chromatography, mass spectrometry, Raman spectroscopy, electron microscopy and oxidation with temperature programming. The results show that: (i) The amount of hydrocarbons “adsorbed” increases with the specific surface area of the argillaceous minerals investigated. (ii) Montmorillonite of type Ca 2+ (Camp Berteaux montmorillonite) reveals “catalytic” activity which enhances the formation of light hydrocarbons, with a predominance of aromatics to the detriment of the heaviest adsorbed compounds. In this case, the carbon residue formed on the mineral locally reveals the appearance of “pre-graphitic” structures. (iii) The same is not true for other minerals, such as illite and attapulgite. Despite their high retention power, such minerals do not show any catalytic activity, and the carbon residues they form seem to have a less polycondensed structure (easier combustion of these residues, higher H/C ratio).

Volume Change Behavior of Desiccated Soils

Little information exists regarding the volume change behaviour of desiccated soils which are widespread in occurance. This paper reports a study on a few such soils and relates their behaviour with the known behaviour of pure clay minerals. The modified effective stress concept is exploited to mechanistically classify the volume change behaviour of desiccated soils. Previous experimental work indicated that repeated desiccation results in interparticle bonding which is also chemical in nature. Such bonding results in increased resistance to compression and greater permeability in such soils. Depending on the degree of bonding, an expansive soil may display either reduced expansiveness or even behave as a non-expansive soil in the undisturbed condition.

Comparative study of moisture release behaviour of soils, soil clays and pure clays

The moisture release curves of a black cotton soil and a lateritic soil, their clay fractions and two pure clays (bentonite, kaolinite) containing mineral species similar to those in the clay fractions were studied in relation to clay mineral composition. While the dominant clay mineral did not solely govern the moisture characteristic curve of a soil, there was a strong similarity between the curves of a pure clay mineral and a soil clay dominated by that mineral. This similarity may be used to identify the dominant mineral constituent of an unknown soil clay.

Complex formation between humic acid and clays as revealed by gel filtration and infrared spectroscopy

Complex formation between pure silicate clay minerals and humic acid (HA) extracted from a Eustis loamy sand (Psammentic Paleudult) was investigated by i.r. spectroscopy and Sephadex G50 and G25 gel filtration. Gel filtration of humic acid after treatment with clay resulted in the separation of normal amounts of high m.w., but reduced concentrations of low m.w. HA. This observation suggested that only the low m.w. fraction of HA was adsorbed by silicate clays. As compared to i.r. spectrograms of original HA, humic acid remaining in solution after interaction with clay exhibited i.r. curves with new bands at 940 and 840 cm −1 for O-Al-OH vibrations and increased absorption in the 1050, 1400 and 1620 cm −1 regions for Si-O and COO − stretching vibrations, respectively. The absorption band for Si-O was retained by the i.r. spectrum of the high m.w. fraction of HA, and the O-Al-OH absorption by that of low m.w. HA. The latter showed in addition the strong band for COO − stretching vibrations.

Untersuchungen über die SO 2-oxydation in verschiedenen böden

The SO 2-oxidation capacity of different soils, clay minerals and other materials has been studied. It was noted that in different soils the content of sulfate increased at concentrations already subletal to the plants. The ability for sulfite oxidation was highest at 40% w.c. (water capacity of soil). An attempt was made to understand the high SO 2-oxidation capacity of the soils induced by an atmosphere predominantly SO 2. The results are in a range 238–2,919 p.p.m. S. A possible reason for this result may be the different saturation of the soils with bases, whereby the mineral derivation of the soil could play an important role. This presumption will be supported by the result, that the oxidation capacity of the soils, being reduced to 1/6 of its first value by repeated extractions with HCl, could be raised to its original value by addition of the leached bases. In a similar manner the oxidation capacity of pure clay minerals, Al(OH) 3 and SiO 2, was increased. Beside this, a pure composition of alkaline and earth alkaline elements, without addition of soils, shows an increased SO 2-oxidation capacity, which is, pH-distinction excepted, proportional to the concentration of bases.

POTASSIUM‐CALCIUM EXCHANGE EQUILIBRIA IN SOILS: THE LOCATION OF NON‐SPECIFIC (GAPON) AND SPECIFIC EXCHANGE SITES

SummarySeveral studies (e.g. Bolt et al., 1963; Beckett, 1964a) of the exchange equilibria between K and Ca on soil colloids or pure clay minerals have drawn attention to the presence of sites with different affinities for K. There is so far no evidence to indicate the location of sites with the highest affinity, though several workers (e.g. van Schouwenburg and Schuffelen, 1963) have assumed that they lie on the edge‐faces of stacks of clay plates, or in the spaces between the expanded leaves of partially weathered stacks of clay plates.Earlier work has resolved the K: Ca exchange isotherms of soils and clays into a curved part at low values of aK/√aCa, attributed to exchange at sites with a high specific affinity for K, and an upper linear part commonly described by the Gapon equation and attributed to non‐specific sites.The present work on soil clays and clay minerals shows that Na hexametaphosphate or changes in pH affect the curved but not the linear part; cetyl trimethyl ammonium bromide and changes in the amount or charge of exchangeable Al affect the linear but not the curved part of the isotherms. At low pH, the linear but not the curved part of the kaolinite isotherm obeys Schofield's Ratio Law. Grinding has more effect on the curved than on the linear part. So the specific sites are attributed to the edges or peripheral interstices of stacks of clay plates, and the non‐specific sites to their planar surfaces.The specific sites take up K more slowly from solution than the non‐specific sites. The isotherms of completely dispersed bentonites have no curved part. The specific sites are attributed to the wedge‐shaped interstices opened between clay plates by weathering, from which exchange is diffusion‐controlled.Added organic cations reduce the numbers of both kinds of site; peroxide treatment increases them.This paper confirms that the exchange sites with highest affinity for K are indeed associated with the edges, rather than the faces, of stacks of clay plates.

Sedimentation Volume and Viscosity of Pure Clay Minerals and their Mixtures as Influenced by the Addition of Quaternary Ammonium Compounds

Sedimentation Volume and Viscosity of Pure Clay Minerals and their Mixtures as Influenced by the Addition of Quaternary Ammonium Compounds

Sedimentation Volume and Viscocity of Pure Clay Minerals and their Mixtures as lnfluenced by the Addition. of Quaternary Ammonium Compounds

Sedimentation Volume and Viscocity of Pure Clay Minerals and their Mixtures as lnfluenced by the Addition. of Quaternary Ammonium Compounds

Clay Mineralogy

The structures of the clay minerals are reasonably well known, but greater detail and more precision are needed if the properties of clays and soils are to be fully understood. For example, the selective adsorptive and catalytic properties and the reaction with organic materials vary with the character of the clay mineral, but the structural factors that control such properties are not well understood. Research is urgently needed on the structure of pure clay minerals and on the reactions of pure clay minerals with organic and inorganic materials. Much past research on clay-mineral reactions has little fundamental value because the clay that was used was composed of a mixture of minerals which were not well characterized. It is not a simple matter to find pure samples of many of the clay minerals, and to a considerable extent progress depends on finding such pure minerals or preparing them in the laboratory.

Measurements of the Acoustic Properties of Sediments. I. Acoustic Velocity

Work has begun on the measurements of the acoustic properties of uncompacted sediments. This paper describes some of the preliminary work on the measurement of the velocity of sound in sediments. A pulse technique is used and measurements have been made over the frequency range from 50 to 200 kc/sec. Results are reported for several artificial sediments containing a wide range of particle sizes and for sediments composed of relatively pure clay minerals. Velocity measurements in these sediments were made as a function of frequency and as a function of particle concentration. A slight dispersion has been measured and this dispersion is compared to existing theoretical predictions. (This work is supported by the Bureau of Ships.)

Equilibrium studies on natural ion-exchange minerals—III: Caesium, sodium and ammonium ions

Isotherms and values of thermodynamics equilibrium constants have been derived for exchange within the system Cs +Na + and Cs +NH 4 + upon lower greensand soil; solid phase activity coefficients have also been calculated. The results are compared with those of other workers on pure clay minerals; as in the case of the Cs +Sr 2+ exchange, it is found that the equilibrium is less favourable towards Cs than for pure montmorillonite, but more so than for attapulgite, confirming the intermediate position of the mixed-clay mineral in the case of the soil.