Dielectric behaviour and relaxation processes of montmorillonite clay nano‐platelet colloidal suspensions in poly(vinyl pyrrolidone)–ethylene glycol oligomer blends

BACKGROUND: Intercalated and exfoliated montmorillonite (MMT) clay structures in polymer matrices improve the thermal, mechanical, electrical and pharmaceutical properties of organic–inorganic materials. Poly(vinyl pyrrolidone) (PVP)–ethylene glycol oligomer (EGO) blends are biocompatible and non‐toxic materials. The dielectric characterization of MMT clay nano‐platelet colloidal suspensions in PVP–EGO blends is important in understanding the ionic conduction behaviour in many complex phenomena occurring in biological systems, and in selective membranes and their use in controlled drug release systems and in liquid electrolytes. RESULTS: An investigation using dielectric spectroscopy in the 20 Hz to 1 MHz frequency range of MMT clay nano‐platelet colloidal suspensions in PVP–EGO blends confirmed that the PVP segmental motion, ionic conduction relaxation time, electric double layer relaxation time and direct current electrical conductivity are significantly influenced by the clay concentration and EGO chain length. In these materials, ionic motion and PVP segmental dynamics are strongly coupled. Intercalation of EGO structures in clay galleries and exfoliation of clay platelets by adsorption of PVP–EGO structures on clay surfaces are governed by hydrogen bonding interactions between the carbonyl groups of PVP monomer units, the hydroxyl groups of EGOs and the hydroxylated aluminate surfaces of the MMT clay. CONCLUSION: The dielectric behaviour of intercalated and exfoliated structures of MMT clay nano‐platelet colloidal suspensions in PVP–EGO blends provides a convenient way to obtain liquid organic‐inorganic polymeric nanocomposite electrolytes with tailored ionic conduction properties. Copyright © 2009 Society of Chemical Industry     

Greek lignites as additives for controlling filtration properties of water–bentonite suspensions at high temperatures

The effectiveness of Greek lignites to control the filtration characteristics of water–bentonite suspensions and to minimize formation damage at high temperatures was studied. Twenty-six lignite samples from various peat/lignite deposits in Greece were used together with a commercial lignite product. The contents of humic and fulvic acids, humins, oxygen, ash and the cation exchange capacity of lignite samples were examined with respect to fluid loss of these suspensions. The results show that most samples provided very good filtration control of the water–bentonite suspensions after exposure to 177 °C with some being superior to the commercial product. Better performance was observed after addition of 3% w/v lignite. Total humic and fulvic acids as percentage of dry lignite matter and the organic matter as lignite percentage showed a weak inverse correlation with the fluid loss volumes.     

Geochemistry of the Muthurajawela peat deposit of Sri Lanka

The Muthurajawela peat deposit of Sri Lanka has been studied for its geochemical distribution of 20 elements. There were no significant positive correlations of the metals with organic carbon. However, most metals, in particular Be, Zr, Li and the majority of the transition series metals, exhibit strong positive correlations with K, Al, Fe and Mn. Owing to the common occurrence of the latter elements in clay particles, this feature indicates the strong association of metals with the clay particles rather than with humic acids of the organic matter. The low pH of the peat bog presumably aids the conversion of the metals to ‘free’ ions which are in turn adsorbed on to clay particles. At low pH values the metal-organic complexes have low stability which accounts for the low metal-organic carbon correlations. However, due to the presence of marine-based sediments in the peat deposit, the metals could have been mobilized as chloro-complexes which were reduced to the free ion state by the effect of the humic acids. The general metal content of the peat deposit does not show enrichment compared to the average black shale, and the source of the metals is considered to be the laterites bordering the eastern part of the deposit and also the lagoonal sediments comprising the top and bottom horizons. Depth-element variations showed that the bottom horizon with abundant clay matter contains the highest amounts of the metals.     

A combination of ESEM, EDX and XRD studies on the fabric of Dutch organic clay from Oostvaardersplassen (Netherlands) and its geotechnical implications

Fabric study, using an environmental scanning electron microscope (ESEM) with a specially designed cooling stage, combined with energy diffraction analysis of X-rays (EDX), has been carried out on organic and calciferous clay from Oostvaardersplassen in the Netherlands for geotechnical engineering research purposes. Three types of clay states have been used: natural, remolded and fractured. ESEM and EDX test results reveal that this clay consists mostly of organic colloid/tissue clothed silt, microfossils, biological remains. Clay minerals were found to be a small fraction. Attention was then drawn to the identification of micro-morphology of calciferous and organic matter present in this clay, by combining these different techniques: ESEM, EDX and optical microscopy. Results indicate the presence of colloid-like film pieces of organic matter throughout the clay which implies the geotechnical properties of this clay, such as strength, could be increased because of cementation.     

Preliminary comparative analyses of two Greek leonardites

Two leonardite benches occur in the lignite basins of Achlada (NW Greece) and Zeli (Central Greece). In this study, we present some initial results concerning chemical composition (C, H, N and S), kind of inorganic matter, contents of free-humic acids, and the petrological features. Both samples are classified as lignites and display similar values of carbon contents. The Zeli-sample displays higher hydrogen and lower sulphur contents than the sample from Achlada. Nitrogen in both cases remains below the detection limit. Increased silicate inorganic influx, consisting mainly of clay minerals, affected both benches. The organic matter is low to moderately gelified and intensely fragmented, with attrinite being the predominant maceral. Inertinites are almost absent, whereas liptinites occur with low values. Values of free-humic acids are similar, ranging up to 50 wt%.     

AN ULTRAMICROSCOPIC MOTION PICTURE STUDY OF THE RELATION OF COLLOIDAL CONTENT AND PLASTICITY IN CLAYS1

Many attempts have been made to account for the plasticity of clay on the basis of colloidal content. If these are warranted then one should find characteristic differences in the colloidal fractions of clay suspensions, when examined ultramicroscopically. Furthermore these differences should serve as an indication of the plasticity. Ultramicroscopic motion pictures were taken of the colloidal fractions of the aqueous suspensions of four clays having different plasticities. Marked differences were found in each instance, which indicated the relative order of the decreasing plasticity of the clays examined to be: English china clay; South Carolina kaolin; North Carolina kaolin; and fireclay semi-flint. These results tend to support the idea that a definite relation exists between the colloidal content of a clay and its plasticity. Suggestions with reference to the extension of this work are made.     

ACID AND BASE BINDING CAPACITIES AND VISCOSITY RELATIONS IN CERTAIN WHITEWARE CLAYS *

In studying the relationships between the chemical and the physical behavior of clay slips, correlations otherwise obscured are brought out if the clay is first carefully purified. Electrodialysis seems to be an effective method of removing interfering adsorbed electrolyte from clay in preparing it for such investigations. Electrodialyzed samples of several whiteware clays in wide use in the ceramic industry were found to behave chemically as weak acids and bases. The amount of Na-OH necessary to neutralize the “acids” coincided with the smallest amount sufficient to produce the minimum viscosity in suspensions of these clays. The pH of exchange neutrality of each clay agreed closely with a maximum in its pH-viscosity curve. At this point, the addition either of HCl or NaOH reduced the viscosity, although not equally. As further amounts of NaOH were added, two effects were recognized. Some clays continued to become more fluid until complete deflocculation, while other clays passed first through a range of concentration in which NaOH caused increasing Viscosity. Changes in viscosity were observed also in suspensions with increasing concentrations of HCl. A theory for these effects is presented.     

Low temperature air oxidation of n-alkanes in the presence of Na-smectite

This paper is the continuation of a study concerning the catalytic effects of clay on organic matter and especially n-alkanes during oxidation carried out at low temperature. The influences of clay minerals were investigated to understand their role better during natural oxidation of organic matter.n-Alkanes oxidation experiments in presence of Na-smectite were carried out at 100 °C during 512 h and reveal an important production of oxygen-bearing molecules to the detriment of initial n-alkanes. Thus, Na-smectite allows to initiate the auto-oxidation of n-alkanes due to its chemical (charged sheets) and/or physical (high specific area) properties. The evolution of oxygen-bearing molecules distribution enables to distinguish two competitive chemical pathways. On one hand, alcohols and ketones are produced with an aliphatic chain length similar to the starting n-alkanes. On the other hand, aliphatic chain cleavages occur and principally produce 1-alcohols, 2-ketones, carboxylic acids and 3-substitued γ-lactones. These oxygen-bearing compounds are more and more preponderant and evidence the fact that cleavage mechanisms become progressively dominant.     

FUNDAMENTAL STUDY OF CLAY: PREPARATION OF A PURIFIED KAOLINITE SUSPENSION,I*

A method of preparing clean clay suspensions is described. Organic matter is removed by hydrogen peroxide and sodium hydroxide digestion, followed by an electro-dialysis treatment to remove other inorganic salts and to prepare a clay-water suspension. After NaOH is added, viscosity and titration values are given for (a) a regular water-washed Florida clay, (b) the same clay after electrodialysis, and (c) the same clay after a thorough cleaning according to the method described. If the sample contains lignite, a clean clay exhibits rheopexy at certain concentrations of NaOH.     

Quality of soil organic matter and C storage as influenced by cropping systems in northwestern Alberta,Canada

Crop rotations and reduction in tillage are commonly recommended for sustained crop production and enhancing soil quality. Our objective was to evaluate the long-term effects of cropping systems (1968–1992) on soil structure, carbon storage and the quality of soil organic matter. The study was conducted on a silt clay loam soil (Typic Cryoboralf) near Beaverlodge, Alberta, The cropping systems were: (a) continuous barley (Hordeum vulgare L.) (CB); (b) continuous bromegrass (Bromus inermiss Leyess.) (CG); (c) continuous forage legume (Medicago sativa L. until 1977, and Trifolium pratense L. since 1978) (CL); and (d) 3 years of bromegrass-legume forage alternating with 3 years of barley (RF). Our data showed that the CG and CL treatments had more stable aggregates with greater mean weight diameter (MWD) than soil under continuous barley. Organic C, total N and the light fraction in soil under CG and CL were higher than those of the other two treatments. Soil under CG had the highest and CB the lowest amounts of acid-hydrolyzable monosacchrides (comprising glucose, arabinose, xylose, mannose and galactose). Higher galactose + mannose concentration in soil under CG indicated a higher soil microbiological activity. Microbial biomass C and N followed the trend among treatments in whole and light fraction organic matter, and total extracted sugars. Soil organic matter ¹³C-NMR spectroscopy showed that: (i) soil under CB contained the highest amounts of aromatic and the lowest content of aliphatic-C, (ii) soil under CL had the lowest phenolic-C and the least aromaticity, and (iii) soil under CG and RF had the highest amounts of aliphatic-C which includes labile substances such as amino acids and carbohydrates, indicating an improvement in the quality of organic matter. It is concluded that perennial forage crops can improve soil structure and soil organic matter quality and quantity as compared with cereal monoculture.     

Identification of clay minerals in coal and wastes from main coal washery, Zonguldak, Turkey

Identification of clay minerals present in coal and washery wastes is important in cleaning fine coal by froth flotation and in flocculation and dewatering. Therefore samples of wastes from jigs and the flotation cell at the Zonguldak main coal washery were collected and analyzed petrographically for their mineral matter content and by X-ray diffraction for their clay content. The “loss on ignition” method was carried out to determine their organic carbon and carbonates. The waste samples contain 48–68% clay minerals in addition to silicates, carbonates, sulfides and coal. Three clay minerals were identified, namely illite, kaolinite and chlorite. Illite seemed to be the dominant clay mineral in washery wastes. Loss on ignition indicated high percentages of organic matter in the fine jig tailings (21%) and flotation tailings (33%). 3%–6.5% of carbonates have also been found.     

Adsorption studies of fatty acids on montmorillonite‐based filler clay

Surface coating of montmorillonite‐based filler clay with stearic and oleic (9‐octadecenoic acid) acids was presented. Sedimentation measurements showed that the sedimentation rate and the sediment volume decreased sharply with the adsorbed amount of the acid up to a certain concentration and then became constant. The chemical analysis showed that the adsorbed amount of either acid by montmorillonite clay increased with the equilibrium concentration of the acid in the solution. The adsorption isotherm indicated the formation of a monolayer on the clay surface at a lower concentration of the acids followed by formation of multilayers of the acids on the clay surfaces at higher concentrations. XRD analysis indicated no intercalation of either acid in the lamella of the clay. We concluded the possibility of surface coating of montmorillonite clay with a monolayer of fatty acids that render the clay organophilic. The adsorption of either acid improved the dispersibility of the clay particles in organic or polymeric media. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2574–2580, 2002     

Photocatalytic degradation of humic acid in the presence of montmorillonite

Humic acids (HA) representing the major fraction of the naturally occurring humic substances (HS) are composed of highly functionalized carbon rich polydisperse organic fractions. Clay minerals which are responsible for the transport of inorganic and organic contaminants constitute the main component of the dispersed inorganic material in natural waters. The understanding of interactions between humic substances and clay minerals is an important task for the achievement of an effective water treatment performance. The aim of this research was to investigate the influence of montmorillonite as a representative clay mineral on the TiO₂ photocatalytic removal of humic acids as the model compound of natural organic matter. The interactions prevailing between humic acid, montmorillonite and TiO₂ surface were assessed prior to the application of photocatalysis in order to address the adsorptive and photolytic behavior of humic acids. The changes attained in humic acid were described by UV–vis spectroscopic i.e. color forming moieties (Color₄₃₆) and UV absorbing centers (UV₃₆₅ and UV₂₅₄), and dissolved organic carbon (DOC) contents. Application of the pseudo first order kinetic model revealed both an enhancement and retardation with respect to the applied montmorillonite dose. The overall effect of montmorillonite on the photocatalytic degradation of humic acid was also evaluated in terms of molecular size distribution profiles (0.45 μm filtered fraction, 100 kDa fraction, 30 kDa fraction and 3 kDa fraction) described by the specified and DOC normalized specific UV–vis parameters.     

Determination of residual organic matter in extracted oil sands using a low temperature ashing method

The application of a low temperature ashing method for estimating total residual organic matter (toluene insolubles) in oil sands is described. A linear correlation exists between organic carbon content and loss on ignition at 400 ± 10 °C of solvent extracted oil sands. The ratio between total organic carbon and the weight loss on ignition (CT/LOl) owing to the removal of residual organic matter is much lower than that obtained for toluene soluble bitumen fractions, indicating very different chemical composition for the residual organic matter. The measured carbon content of the residual organic matter in oil sands suggests that this material could be a mixture of various fractions contained in resins, asphaltenes, asphaltic acids and humic acids.     

Back to the future: Fatty acids,the green genie to design smart soft materials

Fatty acids are widely used in industries for various applications as soaps or in their crystalline form. Fatty acid soaps are used as surface-active agent to stabilize foams and emulsions, for detergency, and surface wetting. Fatty acid molecules in organic solvents are used as low-molecular-mass organic gelators. Currently, there is a renewed interest in using fatty acids in industrial applications instead of petrochemical surfactants since fatty acid soaps are green surfactants. Fatty acids exhibit also many advantages, including the design of responsive soft-materials. Fatty acid soaps are natural pH and thermoresponsive surfactants, which can lead to responsive foams and emulsions. In their crystalline form, fatty acid crystals in both aqueous and non-aqueous solvents stabilize liquid foams. These crystals are also efficient in the production of liquid marbles. Fatty acids are solvosurfactants with the ability to form microemulsions and capillary suspensions. In this review, we illustrate how fatty acid molecules can be used in the manufacture of multiresponsive soft-materials ranging from aqueous and non-aqueous foams, emulsions, nanoemulsions, microemulsions, liquid marbles and capillary suspensions.     

The blending of rockstone clay with peat for the production of sanitaryware in Guyana

The objective of this research is to improve the casting properties of Rockstone clay of Guyana in order to make it suitable for sanitaryware production. The clay is kaolinitic, has low plasticity, low modulus of rupture and is void of organic matter. Blending the clay with different amounts of peat can increase its plasticity and modulus of rupture by over 100%. Improved casting, draining, fettling and trimming properties are achieved with no fired color degradation. There is a slight increase in the fired shrinkage. With the addition of peat to Rockstone clay, sanitaryware products are successfully casted and fired on a laboratory scale.     

Solid state 13C nuclear magnetic resonance of heavy oil/bitumen-derived solids

Solid state ¹³C n.m.r. analysis of the insoluble organic matter associated with the clay mineral, silica, and heavy metal minerals of heavy oils/bitumen is reported. The conditions under which these measurements can be made are related to the concentration of organic matter found, the nature and amount of paramagnetic constituents, and contact times. The data are related to changes in hydrophilic/hydrophobic surface properties of the solids. The relationship with bitumen losses in recovery processes is also discussed.     

Humic acids from the sapropel of Lake Ochaul

The chemical composition of humic acids from the sapropel of Lake Ochaul in the Irkutsk oblast was studied by elemental analysis, IR spectroscopy, and ¹³C NMR spectroscopy. The amounts of the main functional oxygen-containing groups, structural fragments, and chemical bonds in the organic matter of humic acids were found. The sapropel organic matter and the chemical composition of humic acids separated from sapropel at various depths of occurrence were characterized.     

Processing–structure–properties relationships of mechanically and thermally enhanced smectite/epoxy nanocomposites

Mechanically reinforced and thermally enhanced smectite/epoxy nanocomposites were synthesized using “direct” (without solvent) and “solvent” processing techniques. The molecular dispersion of smectite clay in the epoxy resin was investigated for its role in the rheology, structure formation, and properties of nanocomposites. The effects of three types of organic modifiers on the dispersion structure were compared. The use of solvent during processing assists in the enhancement of clay exfoliation. Rheology was used as a method to compare the degree of clay delamination in the resin matrix, as well as to estimate the suspension structure. The critical volume fraction (Φ*) and maximal packaging of smectites were determined and used for prediction of the viscosity. The qualitative changes in the nanostructure of suspensions above Φ*, due to flocculation of exfoliated clay layers, were compared with the alteration of the properties of nanocomposites, related to the structure formation and morphology. The curing kinetics were found to depend on both the organic modifier and solvent, but the extent of curing was roughly equivalent for the pure epoxy resin and the nanocomposites. The structure of the nanocomposites, either intercalated or exfoliated, produced by the direct processing technique was controlled by the organic modifier. By using solvent processing, the effect of the solvent dominates that of the organic modifier, presumably leading to exfoliated nanocomposites. The mechanical and thermal properties are strongly enhanced above the Φ* of smectites, and they are significantly dependent on the type of nanocomposite structure and the use of solvent. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2499–2510, 2005     

Characterization of unextractable organic matter associated with heavy minerals from oil sand

Considerable quantities of organic matter are associated with heavy metal minerals recovered from Suncor aqueous sludge. This organic matter is not extractable with common organic solvents. Attempts were made to concentrate this organic matter by dissolving the mineral matter in acids. Various soluble fractions were also obtained by extraction with methanol/benzene (1:4) after each dissolution step. All these fractions were analysed by elemental analysis, infrared, proton and ¹³C nuclear magnetic resonance spectroscopy.