kaolinite and illite

Phyllosilicate minerals are the important components in soils and an important source of activated aluminum (Al) during soil acidification. However, the mechanisms for Al activation in phyllosilicate minerals were not understood well. In this paper, the effect of phyllosilicate surface hydroxyl groups on Al activation during acidification was studied after the minerals were modified with inorganic and organic materials. After modification of kaolinite, montmorillonite, and illite with fulvic acid (FA-), iron oxide (Fe-), Fe combined with FA (Fe-FA-), and siloxane (Si-O-), the interlayer spaces were altered. For instance, when modified with Fe, Fe entered the interlayer spaces of kaolinite and montmorillonite and changed the interlayer spaces of both minerals but did not affect that of illite. Also, the other modification methods had significant effects on the interlayer space of montmorillonite but not on kaolinite and illite. It was observed that all the modification strategies inhibited Al activation during acidification by reducing the number of hydroxyl groups on the mineral surfaces and inhibiting protonation reactions between H

Topics: Adsorption; Aluminum; Aluminum Silicates; Bentonite; Clay; Hydrogen-Ion Concentration; Kaolin; Minerals; Soil

Heterogeneous reaction of NO

Topics: Aerosols; Arizona; Bentonite; Clay; Dust; Kaolin; Minerals; Nitrogen Dioxide

In this study, a combination of column experiments, interface chemistry theory and transport model with two-site kinetics was used to systematically investigate the effect of pH on the transport of polystyrene nanoparticles (PSNPs) in porous media. The porous media containing quartz sand (QS) and three kinds of clay minerals (CMs)-kaolinite (KL), illite (IL) and montmorillonite (MT), was used in column experiments to simulate the porous media in the soil-groundwater systems. Experimental results showed that the inhibitory effect of CMs on the transport of PSNPs is weakened as pH increases. The two-dimensional (2D) surface of the DLVO interaction energy (2D-pH-DLVO) was built to calculate the interactions between PSNPs and CMs under different conditions of pH. Results suggested the inflection point of PSNP-QS, PSNP-KL, PSNP-IL and PSNP-MT are 2.42, 3.30, 2.84 and 3.69, respectively. Most importantly, there was a significant correlation between the two-site kinetic parameters related to PSNPs transport and the DLVO energy barrier (DB). The contributions of the interactions of PSNPs-PSNPs and PSNPs-minerals were determined for PSNPs transport in porous media. The critical values of pH related to the migration ability of PSNPs in porous media could be determined by a combination of column experiments, 2D-pH-DLVO and PSNPs transport model. The critical values of pH were 2.95-3.01, 3.22-3.51, 2.98-3.02, 3.31-3.33 for the migration ability of PSNPs in QS, QS + KL, QS + IL and QS + MT porous media, respectively. The stronger migration ability of PSNPs under high pH conditions is attributed to the enhanced deprotonation of the media surface and increased negative surface charge, which increases the electrostatic repulsion between PSNPs and porous media (QS, CMs). Moreover, the agglomeration of PSNPs usually is weaker and the average particle size of agglomerates is smaller under the condition of high pH, thus leading to the stronger migration ability of PSNPs under high pH conditions.

Topics: Clay; Kaolin; Kinetics; Microplastics; Minerals; Polystyrenes; Porosity; Quartz; Sand

The sorption of antibiotics on soil minerals and their cotransport have been widely studied for the past few years; however, these processes in concentrated salt solutions (estuary-like conditions) are not fully understood. This study aims to determine the possible sorption of oxytetracycline (OTC) on various natural and synthesized microsized minerals (including haematite, goethite, kaolinite, bentonite, lateritic, kaolinitic and illitic soil clays) under conditions mimicking pure, fresh, brackish and sea waters. The sorption of OTC was found to decrease in surface charge (herein zeta potential), hence altering the colloidal properties of the materials used. The sorption capacities of soil clays for OTC follow the inequality illitic soil clay > kaolinitic soil clay > lateritic soil clay, and the sorption capacities were found to decrease at higher salt concentrations. Seawater can intensify the release of the sorbed OTC from soil clay surfaces while favouring the coaggregation of the remaining OTC with soil clays. This implies that the long-range transport of OTC or other similar antibiotics can be governed by the mineralogical composition/properties of the suspended particles. More importantly, increasing salt concentrations in estuaries may form a chemical barrier at which limited amounts of OTC/antibiotics can pass through, while the remaining OTC/antibiotics can be favoured to aggregate simultaneously with suspended mineral particles.

Topics: Adsorption; Aluminum Silicates; Anti-Bacterial Agents; Clay; Colloids; Kaolin; Minerals; Oceans and Seas; Oxytetracycline; Sodium Chloride; Soil

The regulation effect of Aspergillus niger to the sorption behavior of U(VI) on kaolinite and illite was studied through investigating the enrichment of U(VI) on kaolinite-Aspergillus niger and illite-Aspergillus niger composites. Kaolinite- or illite-A. niger composites were prepared through co-culturation method. Results showed that U(VI) sorption on kaolinite and illite in different pH ranges could be attributed to ion exchange, outer-sphere complexes (OSCs), and inner-sphere complexes (ISCs), while only the ISCs on the bio-composites. Moreover, micro-spectroscopy tests revealed that U(VI) coordinate with phosphate, amide, and carboxyl groups on illite- and kaolinite- A. niger composites. X-ray photoelectron spectroscopy (XPS) further found that U(VI) was partly reduced to non-crystalline U(IV) by A. niger in the bio-composites, occurring as phosphate coordination polymers or biomass-associated monomers. The findings herein provide further insight into the immobilization and migration of uranium in environments.

Topics: Adsorption; Aspergillus niger; Kaolin; Minerals; Uranium

Microplastics are widely detected in the soil-groundwater environment, which has attracted more and more attention. Clay mineral is an important component of the porous media contained in aquifers. The transport experiments of polystyrene nanoparticles (PSNPs) in quartz sand (QS) mixed with three kinds of clay minerals are conducted to investigate the effects of kaolinite (KL), montmorillonite (MT) and illite (IL) on the mobility of PSNPs in groundwater. Two-dimensional (2D) distributions of DLVO interaction energy are calculated to quantify the interactions between PSNPs and three kinds of clay minerals. The critical ionic strengths (CIS) of PSNPs-KL, PSNPs-MT and PSNPs-IL are 17.0 mM, 19.3 mM and 21.0 mM, respectively. Experimental results suggest KL has the strongest inhibition effect on the mobility of PSNPs, followed by MT and IL. Simultaneously, the change of ionic strength can alter the surface charge of PSNPs and clay minerals, thus affecting the interaction energy. Experimental and model results indicate both the deposition rate coefficient (k) and maximum deposition (S

Topics: Bentonite; Clay; Groundwater; Kaolin; Microplastics; Minerals; Plastics; Polystyrenes; Quartz; Sand; Soil

The mineral composition and surface physico-chemical properties, i.e., specific surface area (SSA), cation exchange capacity (CEC), and surface charge of recent sediments and their submicron mineral fractions from different sedimentological environments of the Eastern Adriatic were investigated. The influence of organic matter on these properties was also investigated. It was shown that illite and mixed-layered clay minerals (MLCM) were ubiquitous and showed no size-related preferences while the occurrence of smectites, chlorites, and kaolinites varied. The smectites content increased and the chlorites decreased slightly with decreasing particle size. The sediments from the carbonate-rich environment contained no smectites or chlorites and had the highest kaolinite content. For the first time, in the recent sediments of the Adriatic Sea the poorly- and the well-crystallised kaolinite (Kl and Kl

Topics: Calcium Carbonate; Cations; Clay; Environmental Monitoring; Geologic Sediments; Italy; Kaolin; Lakes; Minerals; Surface Properties; Water Pollutants, Chemical

In this study, microcystin-LR (MCLR) interactions with three representative silicate clays were studied using equilibrium batch experiments in order to provide insight into the role of clays on determining MCLR fate. The three tested clay minerals (kaolinite, montmorillonite and illite), saturated with sodium or calcium ions, were equilibrated with MCLR across a range of toxin concentrations at pH 5, 7 or 9. The results were fit to Freundlich and linear isotherm models, with the linear isotherm fits deemed most appropriate. In general, adsorption of MCLR was greater in the systems with Ca than in those with Na, however, regardless of the cation present, montmorillonite had the highest adsorption affinity for MCLR. Furthermore, except for Ca-montmorillonite, MCLR adsorption decreased with increasing pH. The pH-dependence of adsorption suggests the polar groups of MCLR, carboxylate associated with the glutamic acid and methylaspartic acid groups and amine associated with the arginine group, were more important in determining MCLR interactions with clays than the nonpolar ADDA group. Increased adsorption in systems enriched with calcium suggests Ca modified the clay interfacial properties and the availability of MCLR groups in a manner that increased MCLR affinity. Overall, the results suggest clays are capable of adsorbing MCLR from the aqueous phase, particularly at low pH and when saturated with Ca

Topics: Adsorption; Bentonite; Binding Sites; Calcium; Clay; Hydrogen-Ion Concentration; Kaolin; Marine Toxins; Microcystins; Minerals; Silicates; Sodium

The picloram (PCM) adsorption on nontronite, illite and kaolinite was studied at pH 3, 5 and 7. The adsorption isotherms had well-fitted to Langmuir and Freundlich models equations. The interactions of PCM with the clay mineral surfaces exhibited an anionic profile adsorption, with a decrease in adsorption when the pH increases. The PCM adsorption capacity increases in the following order: kaolinite < illite < nontronite. The X-ray diffraction (XRD) analysis of PCM-clay samples revealed that the picloram molecule does not enter into the clays basal space. The interaction of PCM with clays surface sites through nitrogen of the pyridine ring was confirmed by X-ray photoelectron spectroscopy (XPS). Due to the anionic form of PCM, the adsorption onto the external and edges surface sites of the clay minerals was proposed.

Topics: Adsorption; Clay; Herbicides; Hydrogen-Ion Concentration; Kaolin; Minerals; Photoelectron Spectroscopy; Picloram; X-Ray Diffraction

Proper and economical treatments of wastewater are among the important and potential solutions to increase the water budget. Although mineral ores are barriers of potentially toxic metal contaminants; however to what extent, can these ores stand successfully for decontaminating waters polluted with Cs or Sr is the question of the current study. Therefore a trial was carried out on some of these ores i.e. kaolinite, montmorillonite, and illite, to investigate their effects as decontaminants for waters polluted with either 50 μg Cs L

Topics: Adsorption; Bentonite; Cesium; Kaolin; Minerals; Strontium; Wastewater; Water Pollutants; Water Pollution; Water Purification

Iron-bearing clays are ubiquitously distributed as mineral dusts in the atmosphere. Bromophenols were reported as the major products from thermal decomposition of the widely used brominated flame retardants (BFRs). However, little information is available for the reactivity of iron associated with mineral dusts to interact with the atmospheric bromophenols and the subsequent toxic effects. Herein, three common clay minerals (montmorillonite, illite and kaolinite) were used to simulate mineral dusts, and the reactions with gaseous 2-bromophenol were systematically investigated under environmentally relevant atmospheric conditions. Our results demonstrate that structural Fe(III) in montmorillonite and Fe(III) from iron oxide in illite mediated the dimerization of 2-bromophenol to form hydroxylated polybrominated biphenyl and hydroxylated polybrominated diphenyl ether. The surface reaction is favored to occur at moisture environment, since water molecules formed complex with 2-bromophenol and the reaction intermediates via hydrogen bond to significantly lower the reaction energy and promote the dimerization reaction. More importantly, the formed dioxin-like products on clay mineral dust increased the toxicity of the particles to A549 lung cell by decreasing cell survival and damaging cellular membrane and proteins. The results of this study indicate that not only mineral dust itself but also the associated surface reaction should be fully considered to accurately evaluate the toxic effect of mineral dust on human health.

Topics: A549 Cells; Air Pollutants; Atmosphere; Bentonite; Cell Survival; Clay; Dust; Ferric Compounds; Halogenated Diphenyl Ethers; Humans; Kaolin; Minerals; Phenols; Surface Properties; Water

Topics: Adsorption; Aluminum Silicates; Clay; Kaolin; Minerals; Molecular Weight; Organic Chemicals; Water

The presence of kaolinite, montmorillonite, and illite in packed quartz sand inhibited the transport of graphene oxide to different degrees. Transport inhibition was exerted mainly by the presence of positively charged sites on clay edges (which served as favorable deposition sites), whereas the effects on the overall particle-collector interaction energy and flow path were small. Kaolinite exhibited the most significant transport-inhibition effects because of its high percentage of edge area. Environ Toxicol Chem 2017;36:655-660. © 2016 SETAC.

Topics: Bentonite; Graphite; Hydrogen-Ion Concentration; Hydrology; Kaolin; Minerals; Models, Theoretical; Nanoparticles; Oxides; Particle Size; Porosity; Silicon Dioxide; Solutions; Surface Properties

Polyacrylamides are polymers used in many fields and represent the main source of release of the highly toxic acrylamide in the environment. In this work, a simple, rapid, and sensitive analytical method was developed with HPLC/MS/MS and direct injection for acrylamide analysis in water and adsorption samples. AFNOR standards NF T90-210 and NF T90-220 were used for the analytical method validation and uncertainty estimation. Limit of quantification (LOQ) for acrylamide was 1 μg/L, and accuracy was checked at three acrylamide levels (1, 6, and 10 μg/L). Uncertainties were estimated at 34.2, 22, and 12.4 % for acrylamide concentrations at LOQ, 6 μg/L, and 10 μg/L, respectively. Acrylamide adsorption on clays (kaolinite, illite) and sludge was then studied as a function of pH, time, and acrylamide concentrations. Acrylamide adsorption on kaolinite, illite, and sludge was found to be very weak since adsorption percentages were inferior to 10 %, whatever the pH value and the initial acrylamide concentration. The low affinity of acrylamide for clays and sludge is likely due to its hydrophilic property, small size, and charge neutrality.

Topics: Acrylamide; Adsorption; Chromatography, High Pressure Liquid; Hydrogen-Ion Concentration; Hydrophobic and Hydrophilic Interactions; Kaolin; Minerals; Mining; Tandem Mass Spectrometry; Water

Based on the laser particle size and X-ray diffraction (XRD) analysis, 28 sediment samples collected from the inshore region of the Yellow River estuary in October 2013 were determined to discuss the influence of long-term implementation of the flow-sediment regulation scheme (FSRS, initiated in 2002) on the distributions of grain size and clay components (smectite, illite, kaolinite and chlorite) in sediments. Results showed that, after the FSRS was implemented for more than 10 years, although the proportion of sand in inshore sediments of the Yellow River estuary was higher (average value, 23.5%) than those in sediments of the Bohai Sea and the Yellow River, silt was predominated (average value, 59.1%) and clay components were relatively low (average value, 17.4%). The clay components in sediments of the inshore region in the Yellow River estuary were close with those in the Yellow River. The situation was greatly changed due to the implementation of FSRS since 2002, and the clay components were in the order of illite > smectite > chlorite > kaolinite. This study also indicated that, compared to large-scale investigation in Bohai Sea, the local study on the inshore region of the Yellow River estuary was more favorable for revealing the effects of long-term implementation of the FSRS on sedimentation environment of the Yellow River estuary.

Topics: Aluminum Silicates; China; Clay; Estuaries; Geologic Sediments; Kaolin; Minerals; Rivers; X-Ray Diffraction

Enteropathogens released into the environment can represent a serious risk to public health. Soil clay content has long been known to have an important effect on enteropathogen survival in soil, generally enhancing survival. However, clay mineral composition in soils varies, and different clay minerals have specific physiochemical properties that would be expected to impact differentially on survival. This work investigated the effect of clay materials, with a predominance of a particular mineral type (montmorillonite, kaolinite, or illite), on the survival in soil microcosms over 96 days of Listeria monocytogenes, Salmonella Dublin, and Escherichia coli O157. Clay mineral addition was found to alter a number of physicochemical parameters in soil, including cation exchange capacity and surface area, and this was specific to the mineral type. Clay mineral addition enhanced enteropathogen survival in soil. The type of clay mineral was found to differentially affect enteropathogen survival and the effect was enteropathogen-specific.

Topics: Aluminum Silicates; Bentonite; Clay; Escherichia coli O157; Ireland; Kaolin; Listeria monocytogenes; Minerals; Salmonella enterica; Soil; Soil Microbiology; Survival Analysis; X-Ray Diffraction

In this study, we examined various CO2 hydrate phase equilibria under diverse, heterogeneous conditions, to provide basic knowledge for successful ocean CO2 sequestration in offshore marine sediments. We investigated the effect of geochemical factors on CO2 hydrate phase equilibrium. The three-phase (liquid-hydrate-vapor) equilibrium of CO2 hydrate in the presence of (i) organic matter (glycine, glucose, and urea), (ii) phyllosilicates [illite, kaolinite, and Na-montmorillonite (Na-MMT)], and (iii) mixtures of them was measured in the ranges of 274.5-277.0 K and 14-22 bar. Organic matter inhibited the phase equilibrium of CO2 hydrate by association with water molecules. The inhibition effect decreased in the order: urea < glycine < glucose. Illite and kaolinite (unexpandable clays) barely affected the CO2 hydrate phase equilibrium, while Na-MMT (expandable clay) affected the phase equilibrium because of its interlayer cations. The CO2 hydrate equilibrium conditions, in the illite and kaolinite suspensions with organic matter, were very similar to those in the aqueous organic matter solutions. However, the equilibrium condition in the Na-MMT suspension with organic matter changed because of reduction of its inhibition effect by intercalated organic matter associated with cations in the Na-MMT interlayer.

Topics: Bentonite; Carbon Dioxide; Environment; Geologic Sediments; Kaolin; Minerals; Organic Chemicals; Phase Transition; Silicates; Sodium; Solutions; Solvents; Suspensions; Thermodynamics; Water; X-Ray Diffraction

Sorption to the phyllosilicate clay minerals Illite, kaolinite, and bentonite has been studied for a wide variety of organic cations using a flow-through method with fully aqueous medium as the eluent. Linear isotherms were observed at concentrations below 10% of the cation-exchange capacity (CEC) for Illite and kaolinite and below 1 mmol/kg (<1% CEC) for bentonite. Sorption to clays was strongly influenced by the electrolyte composition of the eluent but with a consistent trend for a diverse set of compounds on all clays, thus allowing for empirical correction factors. When sorption affinities for a given compound to a given clay are normalized to the CEC of the clay, the differences in sorption affinities between clays are reduced to less than 0.5 log units for most compounds. Although CEC-normalized sorption of quaternary ammonium compounds to clay was up to 10-fold higher than CEC-normalized sorption to soil organic matter, CEC-normalized sorption for most compounds was comparable between clays and soil organic matter. The clay fraction is thus a potentially relevant sorption phase for organic cations in many soils. The sorption data for organic cations to clay showed several regular trends with molecular structure but also showed quite a few systematic effects that we cannot explain. A model on the basis of the molecular size and charge density at the ionized nitrogen is used here as a tool to obtain benchmark values that elucidate the effect of specific polar moieties on the sorption affinity.

Topics: Adsorption; Aluminum Silicates; Bentonite; Cations; Clay; Electrolytes; Hydrophobic and Hydrophilic Interactions; Kaolin; Minerals; Molecular Weight; Organic Chemicals; Quaternary Ammonium Compounds; Salts; Soil Pollutants; Static Electricity

To investigate the mechanisms of tritium persistence in clay minerals, three types of clay soils (montmorillonite, kaolinite and illite) and tritiated water were used in this study to conduct the tritium sorption tests and the other related tests. Firstly, the ingredients, metal elements and heat properties of clay minerals were studied with some instrumental analysis methods, such as ICP and TG. Secondly, with a specially designed fractionation and condensation experiment, the adsorbed water, the interlayer water and the structural water in the clay minerals separated from the tritium sorption tests were fractionated for investigating the tritium distributions in the different types of adsorptive waters. Thirdly, the location and configuration of tritium adsorbed into the structure of clay minerals were studied with infrared spectrometry (IR) tests. And finally, the forces and mechanisms for driving tritium into the clay minerals were analyzed on the basis of the isotope effect of tritium and the above tests. Following conclusions have been reached: (1) The main reason for tritium persistence in clay minerals is the entrance of tritium into the adsorbed water, the interlayer water and the structural water in clay minerals. The percentage of tritium distributed in these three types of adsorptive water are in the range of 13.65% - 38.71%, 0.32% - 5.96%, 1.28% - 4.37% of the total tritium used in the corresponding test, respectively. The percentages are different for different types of clay minerals. (2) Tritium adsorbed onto clay minerals are existed in the forms of the tritiated hydroxyl radical (OT) and the tritiated water molecule (HTO). Tritium mainly exists in tritiated water molecule for adsorbed water and interlayer water, and in tritiated hydroxyl radical for structural water. (3) The forces and effects driving tritium into the clay minerals may include molecular dispersion, electric charge sorption, isotope exchange and tritium isotope effect.

Topics: Adsorption; Aluminum Silicates; Bentonite; Clay; Environmental Monitoring; Environmental Pollutants; Kaolin; Minerals; Porosity; Tritium

To ensure safe and efficient geologic CO(2) sequestration (GCS), it is crucial to have a better understanding of CO(2)-brine-rock interactions under GCS conditions. In this work, using biotite (K(Mg,Fe)(3)AlSi(3)O(10)(OH,F)(2)) as a model clay mineral, brine-biotite interactions were studied under conditions relevant to GCS sites (95 °C, 102 atm CO(2), and 1 M NaCl solution). After reaction for 3-17 h, fast growth of fibrous illite on flat basal planes of biotite was observed. After 22-70 h reaction, the biotite basal surface cracked, resulting in illite detaching from the surface. Later on (96-120 h), the cracked surface layer was released into solution, thus the inner layer was exposed as a renewed flat basal surface. The cracking and detachment of the biotite surface layer increased the surface area in contact with solution and accelerated biotite dissolution. On biotite edge surfaces, Al-substituted goethite and kaolinite precipitated. In control experiments with water under the same temperature and pressure, neither macroscopic fibrous illite nor cracks were observed. This work provides unique information on biotite-brine interaction under acidic hydrothermal conditions.

Topics: Aluminum Silicates; Carbon Sequestration; Ferrous Compounds; Hydrogen-Ion Concentration; Iron Compounds; Kaolin; Minerals; Pressure; Seawater; Spectrometry, X-Ray Emission; Surface Properties; Temperature

Clay-humic substance complexes play a major role in controlling the mobility of toxic metals in contaminated soils. However, our understanding of the underlying mechanisms is limited. Binding site analysis of clay and clay-mineral-humic composites, in this study, revealed an enhanced surface reactivity for the clay surface by the sorbed humic substances. Kaolinite and illite had three binding sites with pK(a) values ranging from ∼4.5 to 9.6 at Ca(2+) concentrations of 0.01 and 0.1 M respectively. In the presence of peat humic acid (PHA), four or five binding sites were observed for humics sorbed kaolinite surface at Ca(2+) concentrations of 0.01 and 0.1 M respectively. pK(a) values ranged from ∼4.4 to 9.6 for humic acid concentration of 0.01 and 0.1 mg/mL. For illite, four or five binding sites were found with pK(a)s ranging from ∼4.1 to 9.4. From zeta potential measurements of PHA-kaolinite or PHA-illite suspensions, the already negative potential decreased by 30 mV from pH 4 to 7, and by 10 mV for pH values greater than 7. For illite the initial negative surface potential decreased by 15 mV up to a pH of 9. Above this pH, the potential decrease diminished to 2 or 5 mV. These changes in surface potential confirm the adsorption of PHA to the clay mineral surface. FTIR measurements of clay samples were able to identify the kaolinite and illite phases. In addition, FTIR absorption bands found in the range of 1950-1800 cm(-1), suggest the interaction of PHA with kaolinite and illite surfaces. The results of this study indicate that the sorption of humic substances increases the availability of clay surface functional groups for deprotonation and potential sorption of toxic metal cations.

Topics: Adsorption; Aluminum Silicates; Binding Sites; Calcium; Clay; Humic Substances; Kaolin; Minerals; Surface Properties

Geophagy or deliberate ingestion of soils was observed among Asian elephants (Elephas maximus) in the Udawalwe National Park, Sri Lanka, for several years. The geochemical and mineralogical composition of the clayey soil layers which are purposefully selected and eaten by elephants in the park were studied, in order to identify the possible reasons for elephant geophagy. The concentrations of major and trace elements were determined by means of X-ray fluorescence spectrometry in 21 soil samples from eight geophagic sites and six soil samples collected from four non-geophagic sites. The mineralogical composition of selected soil samples was investigated using X-ray diffractometry (XRD). These geochemical analyses revealed that geophagic soils in the study areas are deeply weathered and that most of the elements are leached from the soil layers under extreme weathering conditions. The XRD data showed that the soils of the area consisted mainly quartz, feldspar, and the clay minerals kaolinite, Fe-rich illite, and smectite. Although no significant geochemical differences were identified between geophagic and non-geophagic soils, a clear difference was observed in their clay mineralogical content. Soils eaten by elephants are richer in kaolinite and illite than non-geophagic soils, which contain a higher amount of smectite. It is suggested that elephants in Udawalawe National Park ingest soils mainly not to supplement the mineral contents of their forage but to detoxify unpalatable compounds in their diet.

Topics: Animals; Antidiarrheals; Elephants; Enterosorption; Feeding Behavior; Inactivation, Metabolic; Kaolin; Minerals; Pica; Soil; Sri Lanka

Physicochemical simulation (pH, electrolytes and temperature) of three physiological media was carried out in order to follow the release of trace elements contained in seven edible clays (mainly kaolinite, illite, muscovite and quartz) collected from the West African countries of Côte d'Ivoire, Guinée and Sénégal. These clays are ingested by pregnant women for diverse reasons that are related to their condition. Simulated oral (6.5

Topics: Africa, Western; Aluminum Silicates; Clay; Diet; Electrolytes; Female; Gastrointestinal Tract; Humans; Hydrogen-Ion Concentration; Kaolin; Minerals; Pica; Pregnancy; Quartz; Soil; Temperature; Trace Elements

Adsorption of three surfactants of different nature, Triton X-100 (TX100) (non-ionic), sodium dodecylsulphate (SDS) (anionic) and octadecyltrimethylammonium bromide (ODTMA) (cationic) by four layered (montmorillonite, illite, muscovite and kaolinite) and two non-layered (sepiolite and palygorskite) clay minerals was studied. The objective was to improve the understanding of surfactant behaviour in soils for the possible use of these compounds in remediation technologies of contaminated soils by toxic organic compounds. Adsorption isotherms were obtained using surfactant concentrations higher and lower than the critical micelle concentration (cmc). These isotherms showed different adsorption stages of the surfactants by the clay minerals, and were classified in different subgroups of the L-, S- or H-types. An increase in the adsorption of SDS and ODTMA by all clay minerals is observed up to the cmc of the surfactant in the equilibrium solution is reached. However, there was further TX100 adsorption when the equilibrium concentration was well above the cmc. Adsorption constants from Langmuir and Freundlich equations (TX100 and ODTMA) or Freundlich equation (SDS) were used to compare adsorption of different surfactants by clay minerals studied. These constants indicated the surfactant adsorption by clay minerals followed this order ODTMA>TX100>>SDS. The adsorption of TX100 and ODTMA was higher by montmorillonite and illite, and the adsorption of SDS was found to be higher by kaolinite and sepiolite. Results obtained show the influence of clay mineral structure and surfactant nature on the adsorption capacity of surfactants by clays, and they indicate the interest to consider the soil mineralogical composition when one surfactant have to be selected in order to establish more efficient strategies for the remediation of soils and water contaminated by toxic organic pollutants.

Topics: Adsorption; Alkanes; Aluminum Silicates; Bentonite; Clay; Kaolin; Magnesium Compounds; Magnesium Silicates; Minerals; Octoxynol; Quaternary Ammonium Compounds; Silicon Compounds; Sodium Dodecyl Sulfate; Soil Pollutants; Spectrum Analysis; Surface-Active Agents

The effect of different rice cultivation periods on the properties of selected soils in alluvial plain were studied in Mazandaran province (north of Iran) in 2004. Soils were sampled form 0, 6, 16, 26 and over 40 years rice cultivation fields. In each treatment three soil profiles and six nearby auger holes were studied. The present study results indicated that continuous rice cultivation have changed soil moisture regime from xeric to aquic, soil color from brown to grayish, surface horizons from mollic to ochric epipedon and soil structure changed from granular or blocky to massive. Therefore, the soil order has changed from Mollisols to Inceptisols. No illuviation and eluviation of clay minerals occurred as a consequence of rice cultivation. X-ray diffraction analysis showed that clay minerals in non-rice cultivated field were illite, vermiculite, montmorillonite, kaolinite and chlorite, but in rice field were illite, montmorillonite, kaolinite and chlorite, respectively. In contrast of montmorillonite, the amount of illite and vermiculite have been decreased by increasing periods of rice cultivation. The pH values of the saturated soil surface in six weeks past plantation have shifted toward neutrality. While Eh value of non-paddy soils were about +90 mv, surface horizons of paddy soils at field conditions had Eh value about +40, -12, -84, -122 mv, respectively. The amounts of organic matter and available Fe, Mn, Zn and Cu were increased whereas available K was decreased in paddy soils.

Topics: Agriculture; Aluminum Silicates; Bentonite; Chlorides; Clay; Hydrogen-Ion Concentration; Iran; Kaolin; Minerals; Oryza; Potassium; Soil; Time Factors; Water; X-Ray Diffraction

This study was focussed on laboratory experiences of retention of radium from one thermal water on sand filters and adsorbents, trying to find an easy method for the elimination in drinkable waters polluted with this natural radio-nuclide. A thermal water from Cantabria (Spain) was selected for this work. Retention experiences were made with columns of 35 mm of diameter containing 15 cm layers of washed river sand or 4 cm layers of zeolite A3, passing known volumes of thermal water at flows between 4 and 40 ml/min with control of the retained radium by determining the amount in the water after the treatment. The statistical analysis of data suggests that retention depends on the flow and the volume passed through the columns. As additional adsorbents were used kaolin and a clay rich in illite. Jar-test experiences were made agitating known weights of adsorbents with the selected thermal water, with addition of flocculants and determination of radium in filtrated water after the treatment. Data suggest that retention is related to the weight of adsorbent used, but important quantities of radium seem remain in solution for higher amounts of adsorbents, according to the statistical treatment of data. The elution of retained radium from columns or adsorbents, previously used in experiences, should be the aim of a future research.

Topics: Adsorption; Filtration; Hot Temperature; Kaolin; Minerals; Radium; Silicon Dioxide; Water Pollutants, Radioactive; Water Purification; Zeolites

The present work investigates the adsorptive behavior of As(V) ions with kaolinite, montmorillonite and illite in aqueous medium as a function of As(V) concentration, pH, contact time and temperature. As(V) adsorption on studied clays were pH dependent and maximum adsorption were achieved in the pH range 2.0-5.0. The adsorption data gave good fits with Langmuir isotherm and yielded Langmuir monolayer capacity of 0.86, 0.64 and 0.52 mg As(V) /g of kaolinite, montmorillonite and illite, respectively. An increase in adsorption temperature resulted in a decrease in the amount of As(V) adsorbed. The results of leaching study showed that, kaolinite was very active clay constituent regarding both As(V) adsorption and mobility. The electrokinetic behavior of both the kaolinite and montmorillonite were modified in the presence of As(V). The shift in isoelectric point indicated that adsorption involves inner sphere surface complexation and strong specific ion adsorption. Kaolinite was successfully tested as an adsorbent for the removal of arsenic from two contaminated groundwater samples containing arsenic in the range 1.36-1.41 mg/L.

Topics: Adsorption; Arsenic; Bentonite; Isoelectric Point; Kaolin; Minerals; Temperature; Water Pollutants, Chemical

The objective of this work was to coat aluminosilicate clays on an inert silica support, and to characterize the properties and stability of the clay-silica coating. Two polymers, polyacrylamide (PAM) and polyvinyl alcohol (PVA), were used to bind kaolinite, illite, and smectite onto silica grains. The clay-polymer composites were studied by X-ray diffraction, FTIR, and electrophoretic mobility. Clay coatings on silica grains were characterized by mass coverage, scanning electron microscopy, specific surface area, and pH stability. Silica sand was successfully coated with clays by using the two polymers, but with PVA, the clay coating had a greater mass coverage and was more stable against pH variations. Less polymer was needed for the clay coating using PVA as compared to using PAM. Clay-polymer complexes and pure clay minerals had similar cation exchange capacities and electrophoretic mobilities, indicating that overall surface charge of the clays was little affected by the polymers. Some decrease in hydrophilicity was observed for illite and smectite when clays where coated with the polymers. The methodology reported here allows the generation of a clay-based porous matrix, with hydraulic properties that can be varied by adjusting the grain size of the inert silica support.

Topics: Acrylic Resins; Adsorption; Aluminum Silicates; Clay; Electrophoresis; Hydrogen-Ion Concentration; Ion Exchange; Kaolin; Microscopy, Electron, Scanning; Minerals; Particle Size; Polyvinyl Alcohol; Silicates; Silicon Dioxide; Spectroscopy, Fourier Transform Infrared; Surface Properties; X-Ray Diffraction

Sorption of the endocrine-disrupting chemical 17beta-estradiol (E(2)) from aqueous solutions to goethite, an iron oxide, and the clay minerals kaolinite, illite, and montmorillonite (K and Ca forms) was measured at 25 degrees C. The clay minerals sorbed more E(2) than the oxide, with sorption capacity increasing in the order goethite

Topics: Adsorption; Bentonite; Estradiol; Iron Compounds; Kaolin; Minerals; Soil

The adsorption and desorption behavior of tributyltin (TBT) from aqueous solution to clay-rich sediments was studied under various conditions (pH, salinity) using the batch technique. Sediments containing illite, kaolinite, and montmorillonite in different proportions were used as sorbent materials. Several physicochemical parameters of the sediments (e.g., Brunauer-Emmett-Teller [BET] surface area, cation exchange capacity [CEC], total organic carbon [TOC]) were evaluated to assess the influence of sediment characteristics to the adsorption capacity for TBT Adsorption isotherms were linear over the concentration range of 100 to 1,000 ng(Sn)/ml. The adsorption coefficient (Kd) values range from 29 to 70 at the pH value generally found in marine systems (pH 8). The adsorption capacity shows a maximum in the range of pH 6 and 7. Salinity is also an important factor in controlling TBT adsorption. The strongest adsorption was observed at salinity of 0/1000, and it strongly decreases with increasing salinity. The adsorption mechanism is controlled by the properties of the clay minerals as well as the aquatic chemistry of TBT. Desorption takes place over the studied pH range (4-8) when contaminated samples interact with TBT-free water at given experimental conditions.

Topics: Adsorption; Aluminum Silicates; Bentonite; Clay; Geologic Sediments; Hydrogen-Ion Concentration; Kaolin; Minerals; Seawater; Trialkyltin Compounds; Water Pollutants, Chemical

The heterogeneous decomposition of CHF2OCH2C2F5, a potential substitute for hydrofluorocarbons, over aluminosilica clay minerals in air, was confirmed to occur at 313 K in a closed-circulation reactor. HC(O)OCH2C2F5, the gaseous main product was produced through hydrolytic elimination of F atoms from the CHF2OCH2- group. CHF2OCH2CF3 also decomposed to HC(O)OCH2CF3 over the clay minerals. The pseudo-first-order rate constants were determined for the decompositions over eight types of clay minerals (19 samples). The various clay minerals had different abilities to decompose these hydrofluoroethers. The decomposition rates per Brunauer-Emmett-Teller surface area and the conversion ratios to HC(O)OCH2C2F5 or HC(O)OCH2CF3 for the reactions over kaolinite, halloysite, and illite were high in comparison to those for the same reactions over montmorillonite, hectorite, and nontronite. The dependence of this heterogeneous reaction on temperature and relative humidity indicates that, in the environment, the reaction could be important only in hot, dry regions. The results did not suggest that sunlight would directly accelerate the decay of CHF2OCH2CF3 or CHF2OCH2C2F5. In the presence of clay-containing soils in arid areas, this hydrolytic oxidation reaction may significantly affect both the lifetime and the degradation products of CHF2OCH2CF3 and CHF2OCH2C2F5 in the troposphere.

Topics: Aluminum Silicates; Clay; Environmental Pollutants; Ethers; Hydrocarbons, Fluorinated; Kaolin; Minerals; Sunlight

Although cyclodextrins are increasingly used in soil decontamination, little is known about their effects on soil physicochemical properties. In this work, the surface and pore properties of randomly methylated beta-cyclodextrin (RAMEB) and three typical clay minerals were characterized, and the effects of RAMEB concentrations on clay minerals were studied using water vapor adsorption-desorption and mercury intrusion porosimetry techniques. As compared to clay minerals, for pure RAMEB very large surface area and volume of nanometer-size pores (micropores) were determined. Energy of interaction with water vapor, volume of micrometer-size pores (mesopores), and fractal dimensions in both pore size ranges of RAMEB were lower than those of the minerals. When increasing amounts of RAMEB were added to the minerals, the surface area and micropore volume decreased and adsorption energy increased. The volume of mesopores decreased after RAMEB treatments for bentonite and kaolin and increased for illite. As deduced from the fractal dimensions increase, the pore structure of the minerals became more complex with RAMEB addition. The observed changes were in general contrary to these expected when RAMEB and minerals coexist as separate, nonreactive phases and suggested strong interaction of RAMEB with clay minerals.

Topics: Adsorption; Algorithms; Aluminum Silicates; Bentonite; Clay; Cyclodextrins; Fractals; Kaolin; Mercury; Minerals; Porosity; Soil; Surface Properties