Suspensions Of Clay Minerals Research Articles

Phase-equilibrium characteristics of methane hydrate in clay mineral suspensions: Differential scanning calorimetry experiments and density functional theory studies

The investigation of methane hydrate equilibrium conditions is crucial for comprehending the occurrence of methane hydrate in marine sediments. In this study, the liquid-hydrate-vapor equilibrium condition of methane hydrate in montmorillonite and kaolinite suspensions in the presence of glycine was investigated through differential scanning calorimetry experiments. The results indicated that glycine inhibited the phase equilibrium of methane hydrate. The phase equilibrium conditions of methane hydrate in kaolinite suspension closely resembled those in pure water. In contrast, calcium montmorillonite hindered the phase equilibrium of methane hydrate owing to the presence of Ca2+. The phase equilibrium conditions of methane hydrate in kaolinite suspension with the addition of glycine were similar to those in glycine solution. The inhibitory effect of calcium montmorillonite on the phase equilibrium condition of methane hydrate intensified with the addition of glycine. Furthermore, density functional theory simulations indicated that glycine significantly reduced the binding energy between montmorillonite layers and Ca2+, potentially mitigating the inhibitory effect of Ca2+ on methane hydrate formation under suitable glycine concentrations. The diverse equilibrium conditions of methane hydrate, influenced by the types of clay minerals, salt ions, and organic matters, may play a critical role in the formation and occurrence of natural gas hydrates in marine environments, warranting exploration in future studies.

Methane hydrate formation in clay mineral suspensions containing glycine: Experimental study and molecular dynamics simulation

Understanding the effects of clay minerals and amino acids on methane hydrate (MH) formation is essential for elucidating the occurrence of MH in marine sediments. In this study, kinetic experiments and molecular dynamics simulations of MH formation in montmorillonite and kaolinite systems with the presence of glycine were investigated. The experimental results showed that the addition of 5 wt% montmorillonite and 5 wt% kaolinite inhibited and promoted MH formation, respectively. Adding 1.5 wt% glycine to the montmorillonite suspension shortened the nucleation time and reduced the amount of MH; it also weakened the facilitating effect of the kaolinite suspension. The simulation results showed MH nucleation in the bulk solution due to the hydration properties of Ca2+ on the external surface of montmorillonite. However, the addition of glycine reduced the inhibitory effect of Ca2+ on MH formation due to the electrostatic interaction between the Ca2+ and COO– groups. Adsorbed methane molecules on the kaolinite siloxane surface formed clathrate-like structures. In addition, glycine also abnormally incorporated into the MH structure to inhibit MH nucleation. These findings imply that the clay mineral had a significant effect on the distribution of amino acids, causing the formation of MH in clay mineral suspension to be different from pure water. Therefore, these interactions should be fully considered when studying the occurrence mechanism of natural gas hydrate when clay minerals and amino acids coexist in marine sediments.

The filtration of aqueous clay mineral suspension in the presence of bitumen

Typical mine tailings can be dewatered by filter press to filter cakes containing >=85 wt% solids that are ready for reclamation, but Alberta oil sands tailings could only reach about 60 wt% solids using the same technology, even when the dominant particle sizes are similar. In this work, the effects of residual bitumen, one of the distinguishing features of oil sands tailings, were investigated. The residual bitumen in the oil sands tailings exists in the forms of bulk bitumen, emulsified bitumen, and adsorbed bitumen. The roles of the three forms of bitumen were investigated in the filtration of primarily a model mineral kaolinite mineral slurry supplemented by rutile, quartz and montmorillonite slurries. Generally, bulk bitumen was found not to affect filtration significantly, emulsified bitumen facilitated filtration possibly by mopping the ultrafine particles, while bitumen adsorbed on mineral surfaces had more complex effects: a thin bitumen coating improved filtration because of the induced surface hydrophobicity, while a thick bitumen coating impeded filtration due to its mobile and deformable nature. The poor filterability of oil sands tailings may be partly caused by the mobile and deformable bitumen coating on the sands/clay mineral surfaces. This study elucidated the effects of a third deformable organic phase on the filtration of an aqueous mineral slurry, providing insights for solid–liquid separation in the presence of a mobile third phase.

Coaggregation assisted by cationic polyelectrolyte and clay minerals as a strategy for the removal of polystyrene microplastic particles from aqueous solutions

This study aims to test the removal of polystyrene microplastics (PSMPs) from aqueous solution by using the cationic polyelectrolyte polydiallyldimethylammonium chloride (polyDADMAC) to stimulate coaggregation of PSMPs and clay minerals with different shape and surface charge properties, namely kaolinite, montmorillonite, and palygorskite. Colloidal stability, aggregation kinetics and surface charge properties were evaluated simultaneously. For this purpose sedimentation experiments in test tubes were run together with measurements on the course of the hydrodynamic diameter over time by dynamic light scattering and linked with particle charge analyses. In the pH range from 4 to 8, negative surface charge of all clay minerals introduced as well as PSMPs can be neutralized by the addition of polyDADMAC. When being introduced into suspensions of PSMPs and clay minerals, the long-chain poly-DADMAC acts as a bridge to structuralize a matrix of PSMPs and clay particles, by which coaggregation is favoured. The efficiency to remove PSMPs from aqueous solution, follows the order: palygorskite > montmorillonite > kaolinite. Although these clay minerals have been used in water purification for decades, our findings with the amendment of an organic polycation illustrate their extended ability, particularly for palygorskite, to efficiently remove emerging pollutants such as microplastics.

Cadmium adsorption to clay-microbe aggregates: Implications for marine heavy metals cycling

Interactions between microorganisms and clay minerals influence the transport and cycling of metal contaminants in both marine and terrestrial environments. The present study was conducted to quantify the adsorption of dissolved cadmium, Cd(II), under seawater-like conditions to the marine cyanobacterium Synechococcus sp. PCC 7002, three common clay minerals (kaolinite, montmorillonite and illite), as well as cell-clay aggregates. We show here that the Synechococcus-only experiments removed the most Cd above pH 5.5, followed in decreasing order by aggregates of 50% cells:50% individual clays, aggregates of cells and all 3 clays, and individual clays. Electron microscope imaging showed that clays associated in a tangential edge-on orientation to the cells in Synechococcus-clay mineral aggregates. A non-electrostatic surface complexation modeling approach was used to fit Cd adsorption onto Synechococcus cells and individual clay minerals. The resulting Cd binding constants were then used in consort with surface functional group pKa values and site concentrations to accurately predict the extent of Cd adsorption onto the Synechococcus-clay mineral aggregates using the component additivity (CA) approach. We observed that the addition of cyanobacterial cells to clay mineral suspensions led to significantly larger mean aggregate sizes of clay minerals, enhancing the clay sedimentation rate. Although specifically focused on Cd, our study indicates that the ratio of bacterial plankton to clay minerals is an important determinant in terms of understanding the rate with which metals are transferred from the water column to the seafloor.

Phototransformation of perfluorooctane sulfonamide on natural clay minerals: A likely source of short chain perfluorocarboxylic acids

In this study, a new phototransformation pathway for perfluorooctane sulfonamide (FOSA) and underlying degradation mechanisms are described. Phototransformation of FOSA in a natural clay mineral (montmorillonite) suspension was compared to that in an aqueous solution. Results showed that the presence of montmorillonite can significantly promote the transformation of FOSA to perfluocarboxylic acids (increasing rate). The phototransformation reaction was found to be initiated by the activation of adsorbed oxygen molecules on the surface of montmorillonite, which generate superoxide anion and hydroxyl radicals. Hydroxyl radicals can then attack FOSA adsorbed onto the surface of montmorillonite, promoting the transformation process. In this reaction, clay minerals played a dual role: providing hydroxyl radicals and concentrating FOSA on their surfaces. This helped to promote the contact and reaction between FOSA and hydroxyl radicals. This study provides the first evidence that heterogeneous oxidation of FOSA at the surface of natural clay minerals may act as an important source of perfluocarboxylic acids (PFCAs), especially short chain PFCAs (i.e. trifluoroacetic acid, TFA).

Abiotic Degradation of Chlorinated Solvents by Clay Minerals and Fe(II): Evidence for Reactive Mineral Intermediates.

For decades, there has been evidence that Fe-containing minerals might contribute to abiotic degradation of chlorinated ethene (CE) plumes. Here, we evaluated whetherFe(II) in clay minerals reduces tetrachloroethene (PCE) and trichloroethene (TCE). We found that structural Fe(II) in both low (SWy-2) and high (NAu-1) Fe clay minerals did not reduce PCE or TCE under anoxic conditions. There was also no reduction of PCE or TCE after adding 5 mM dissolved Fe(II) to the clay mineral suspensions. In the presence of high Fe(II) concentrations (20 mM), however, PCE and TCE reduction products were observed in the presence of low Fe-content clay mineral SWy-2. Mössbauer spectroscopy results indicate that a mixed-valent Fe(II)-Fe(III) precipitate formed in the reactive SWy-2 suspensions. In contrast, in suspensions containing 20 mM Fe(II) alone or Fe-free clay mineral (Syn-1), we observed a purely Fe(II)-containing precipitate (Fe(OH)2) and also PCE and TCE reduction products. Interestingly, the amount of CE products decreased in the order of Fe-free clay mineral Syn-1 > Fe(OH)2 > low Fe-content clay mineral SWy-2, suggesting that clay mineral Fe controlled the formation of the reactive mineral phase. Additional experiments with hexachloroethane (HCA) revealed that faster HCA reduction occurred withdecreasing clay mineral Fe content. Kinetic modeling yielded invariable second-order rate constants and increasing concentrations of reactive Fe(II) as the Fe(II)/Fe(total) content of the precipitates increased. Our data suggest that clay mineral Fe(III) is a sink for electrons from added Fe(II) that otherwise might have reduced the CEs. Furthermore, our findings are consistent with the hypothesis that active precipitation of Fe(II)-containing reactive mineral intermediates (RMI) may be important to CE reduction and suggest that RMI formation depends on clay mineral presence and Fe content.

Aridisols in the Southern Permian Basin of Lithuania: a key to understanding clay cement distribution

The change from fossil to geothermal energy supply includes the necessity to re-evaluate gas reservoirs in the Southern Permian Basin of NW Europe, as higher permeability reservoirs are needed for the exploitation of geothermal energy than natural gas. A key reservoir risk in Permian sandstones in the Southern Permian Basin is the presence of clay cement. The distribution of the clay cement is not properly understood. The negative effect can be attributed to complex grain coatings formed by tangential clay directly around the detrital grains followed by authigenic clay rim cement, both being genetically related. This study presents new results on the origin of the tangential and the authigenic clay. The Southern Permian Basin in Lithuania was a marginal area of the basin with low accommodation rates and extensive aridisol development. Here, sandstones of the Perloja Formation contain abundant clayey matrix in the form of grain and void coatings. The limited burial depth of a few hundreds of metres ensured that the original internal fabric and mineralogy of the clay coatings remained well preserved. Thin section microscopy revealed that the clay coatings are cutans that formed by post-depositional mechanical infiltration (illuviation) of suspensions of clay minerals, iron hydroxides and some clay to silt-sized quartz. Other pedogenic features are the development of nodular calcrete, rootlets, and of infiltrated clay. Aridisols were recurrently eroded by fluvial or aeolian activity causing wide-scale dispersion of siliciclastic grains with more or less complete clay cutans and also carbonate (calcrete) clasts in certain stratigraphic intervals.

Experimental Deposition of Carbonate Mud From Moving Suspensions: Importance of Flocculation and Implications For Modern and Ancient Carbonate Mud Deposition

Abstract Flume experiments with fine-grained carbonate particles (< 62.5 µm) show that they form floccules that travel in bedload, form current ripples, and deposit laminated sediments. In order to compare our flume experiments to work on sand transport, we ran flume experiments with medium sand and observed that the velocities at which sand grains started to move and form ripples were in the same range as those where floccules move and form ripples. These ripples are in essence identical to those formed by clay-mineral floccules or sand grains under similar conditions. In light of previous experiments with clay minerals, these results indicate that, of the key controls on mud deposition, flocculation and suspended-sediment concentration are more important than particle mineralogy or water chemistry, and are about as important as bottom shear stress for deposition. Suspensions of carbonate mud show the same pattern of flocculation, ripple formation, and bed accretion as observed previously in experiments with clay-mineral suspensions. The resulting carbonate mud deposits show internal low-angle (2–5 degrees) laminae, and in plan view a pattern of ripple foresets that is identical to rib-and-furrow structure in sandstones. Just as previously assumed for terrigenous muds, there has been a long-standing notion that accumulation of abundant carbonate mud reflects quiescent conditions of offshore and deeper-water environments. These experiments demonstrate unequivocally that carbonate muds can also accumulate in energetic settings. In the sedimentary record of carbonate rocks, interbedded grainstones and lime mudstones may thus not necessarily reflect shifts in depositional energy (or water depth), but alternatively may imply a shift in supplied sediment type. The observations we report suggest that published interpretations of ancient lime muds and derived paleoceanographic conditions may need to be reevaluated.

Interactions of clay minerals in copper–gold flotation: Part 1 – Rheological properties of clay mineral suspensions in the presence of flotation reagents

Clay minerals are often associated with copper, gold and other valuable minerals and place a widespread problem in mineral flotation. This paper is one of a series addressing the problem caused by clay minerals in copper–gold flotation. This study seeks to understand the rheological behaviour of kaolinite and bentonite suspensions at natural pH and how the pH modifier, collector and frother normally used in copper–gold flotation affect the rheological properties. It was found that kaolinite and bentonite suspensions may follow Newtonian flows or non-Newtonian flows with pseudoplastic characteristics depending on the solid concentration. Bentonite has a stronger effect on the viscosity of suspensions than kaolinite. The pH modifier, collector and frother have a potential to alter the rheological behaviour of kaolinite and bentonite suspensions and the effect of the pH modifier is more pronounced.

Rheological Study of Two-Dimensional Very Anisometric Colloidal Particle Suspensions: From Shear-Induced Orientation to Viscous Dissipation

In the present study, we investigate the evolution with shear of the viscosity of aqueous suspensions of size-selected natural swelling clay minerals for volume fractions extending from isotropic liquids to weak nematic gels. Such suspensions are strongly shear-thinning, a feature that is systematically observed for suspensions of nonspherical particles and that is linked to their orientational properties. We then combined our rheological measurements with small-angle X-ray scattering experiments that, after appropriate treatment, provide the orientational field of the particles. Whatever the clay nature, particle size, and volume fraction, this orientational field was shown to depend only on a nondimensional Péclet number (Pe) defined for one isolated particle as the ratio between hydrodynamic energy and Brownian thermal energy. The measured orientational fields were then directly compared to those obtained for infinitely thin disks through a numerical computation of the Fokker-Plank equation. Even in cases where multiple hydrodynamic interactions dominate, qualitative agreement between both orientational fields is observed, especially at high Péclet number. We have then used an effective approach to assess the viscosity of these suspensions through the definition of an effective volume fraction. Using such an approach, we have been able to transform the relationship between viscosity and volume fraction (ηr = f(φ)) into a relationship that links viscosity with both flow and volume fraction (ηr = f(φ, Pe)).

Aqueous Suspensions of Natural Swelling Clay Minerals. 2. Rheological Characterization

We report in this article a comprehensive investigation of the viscoelastic behavior of different natural colloidal clay minerals in aqueous solution. Rheological experiments were carried out under both dynamic and steady-state conditions, allowing us to derive the elasticity and yield stress. Both parameters can be renormalized for all sizes, ionic strength, and type of clay using in a first approach only the volume of the particles. However, applying such a treatment to various clays of similar shapes and sizes yields differences that can be linked to the repulsion strength and charge location in the swelling clays. The stronger the repulsive interactions, the better the orientation of clay particles in flows. In addition, a master linear relationship between the elasticity and yield stress whose value corresponds to a critical deformation of 0.1 was evidenced. Such a relationship may be general for any colloidal suspension of anisometric particles as revealed by the analysis of various experimental data obtained on either disk-shaped or lath- and rod-shaped particles. The particle size dependence of the sol-gel transition was also investigated in detail. To understand why suspensions of larger particles gel at a higher volume fraction, we propose a very simplified view based on the statistical hydrodynamic trapping of a particle by an another one in its neighborhood upon translation and during a short period of time. We show that the key parameter describing this hydrodynamic trapping varies as the cube of the average diameter and captures most features of the sol-gel transition. Finally, we pointed out that in the high shear limit the suspension viscosity is still closely related to electrostatic interactions and follows the same trends as the viscoelastic properties.

Aqueous Suspensions of Natural Swelling Clay Minerals. 1. Structure and Electrostatic Interactions

In this article, we present a general overview of the organization of colloidal charged clay particles in aqueous suspension by studying different natural samples with different structural charges and charge locations. Small-angle X-ray scattering experiments (SAXS) are first used to derive swelling laws that demonstrate the almost perfect exfoliation of clay sheets in suspension. Using a simple approach based on geometrical constraints, we show that these swelling laws can be fully modeled on the basis of morphological parameters only. The validity of this approach was further extended to other clay data from the literature, in particular, synthetic Laponite. For all of the investigated samples, experimental osmotic pressures can be properly described by a Poisson-Boltzmann approach for ionic strength up to 10(-3) M, which reveals that these systems are dominated by repulsive electrostatic interactions. However, a detailed analysis of the Poisson-Boltzmann treatment shows differences in the repulsive potential strength that are not directly linked to the structural charge of the minerals but rather to the charge location in the structure for tetrahedrally charged clays (beidellite and nontronites) undergoing stronger electrostatic repulsions than octahedrally charged samples (montmorillonites, laponite). Only minerals subjected to the strongest electrostatic repulsions present a true isotropic to nematic phase transition in their phase diagrams. The influence of ionic repulsions on the local order of clay platelets was then analyzed through a detailed investigation of the structure factors of the various clay samples. It appears that stronger electrostatic repulsions improve the liquidlike positional local order.

Transport of organic matter and clay minerals in estuaries of the Arctic sea (Experimental and Field Observations)

The behavior of clay minerals under different salinity conditions was studied during model experiments using clay mineral suspensions (bentonite and kaolinite) and organic substance solutions (chitosan, humic acids). It was shown that the kaolinite suspension was more stable and may migrate through the river-sea barrier, while the bentonite suspension coagulated even under 1–2‰ salinity. The influence of the organic matter’s nature on the stability of clay mineral suspensions and their ability to migrate through the marginal filter was discussed.

Stratigraphic controls on water quality at coal mines in southern New Zealand

Water quality at four coal mines in southern New Zealand can be related directly or indirectly to the geology and mineralogy of the stratigraphic sequence in which the coal mines occur. The Late Cretaceous Taratu Formation of the Kaitangata coalfield formed in a marginal marine setting during regional marine transgression, and marine incursions punctuated coal formation. Abundant authigenic and remobilised pyrite at the Wangaloa mine (typically 4 wt%S in coal) in the Kaitangata coalfield has oxidised and caused acidification of mine waste rocks (to pH 1) and mine waters (to pH 3). Similar or even greater amounts of pyrite occur locally at the nearby Kai Point mine, although the mined seam typically has <2 wt%S. However, dissolution of carbonate concretions in marine sediments immediately overlying the mined seam at Kai Point mine ensures that acid generated by pyrite oxidation is neutralised, and the site generally has substrates and waters with near‐neutral or alkaline pH. The close stratigraphic association between coal and marine sediments at Kai Point mine has resulted in high B contents in coal (up to 500 mg/kg) about 10 times higher than at the nearby Wangaloa mine. Both mines have elevated dissolved B contents in mine waters (up to 6 mg/L at Wangaloa). The Late Cretaceous coal‐bearing sequence at Ohai is entirely nonmarine, pyrite is rare or absent, and no environmental acidification occurs. Likewise, the Miocene coal‐bearing strata at Newvale coal mine have negligible pyrite and no acidification occurs from these rocks. However, iron sulfide cements have formed in Pliocene gravels from groundwater derived from rain with marine aerosols. Oxidation of this sulfide material has caused localised acidification at Newvale mine. Acidification has caused localised and generally short‐term elevation of dissolved trace elements at Wangaloa and Newvale mines, with dissolved Al up to c. 2.5 mg/L at Newvale. Suspensions of clay minerals cause turbidity at all mines. Well‐washed, coarse (>1 μm), detrital kaolinite at Kai Point, Wangaloa, and Newvale mines settles readily (within days). Chlorite from disaggregated labile clasts in overlying Pliocene gravels dominates longer term turbidity at Newvale, but the turbidity decreases rapidly on a time‐scale of months. Fine‐grained (including sub‐micrometre) poorly sorted authigenic kaolinite from labile clasts in the coal‐bearing strata at Ohai causes long‐term turbidity, with negligible setting over 9 months. The stratigraphically controlled processes quantified in this study can be used to predict the nature and scale of potential water quality changes in new coal mines in southern New Zealand.

Formation of Carbon Dioxide Hydrate in Soil and Soil Mineral Suspensions with Electrolytes

We have identified the effects of solid surface (soil, bentonite, kaolinite, nontronite, and pyrite) and electrolyte (NaCl, KCl, CaCl2, and MgCl2) types on the formation and dissociation of CO2 hydrate in this study. The hydrate formation experiments were conducted by injecting CO2 gas into the soil suspensions with and without electrolytes in a 50 mL pressurized vessel. The formation of CO2 hydrate in deionized water was faster than that in aqueous electrolyte solutions. The addition of soil suspensions accelerated the formation of CO2 hydrate in the electrolyte solutions. The hydrate formation times in the solid suspensions without electrolytes were very similar to that in the deionized water. We did not observe any significant differences between the hydrate dissociation in the solid suspension and that in the deionized water. The pHs of clay mineral suspensions decreased significantly after CO2 hydrate formation and dissociation experiments, while the pH of the soil suspension slightly decreased by less than pH 1 and that of pyrite slightly increased due to the dissolution of CO2 forming carbonic acid. The results obtained from this research could be indirectly applied to the fate of CO2 sequestered into geological formations as well as its storage as a form of CO2 hydrate.

Novel method for transmission infrared analysis of clay minerals using silicon wafer substrates

AbstractA novel method for the analysis of clay minerals using Fourier transform infrared spectroscopy is presented. Clay mineral suspensions are dried on a Si wafer substrate for transmission infrared (IR) analysis. Four natural Source Clays from the Source Clays Repository of The Clay Minerals Society, SWy-2, SAz-1, SHCa-1 and KGa-1b, as well as the synthetic hectorite, Laponite RD, were analyzed using the described method with signal to noise (s/n) ratios in excess of 100,000 for the strongly absorbing Si-O stretching frequency. Scanning electron microscopy (SEM) images show that the mineral films possess suitable uniformity and low surface roughness for transmission IR measurements that is confirmed by minimal deviations in the baseline of collected IR spectra. The IR spectra are generated and peak locations are compared to previously reported values, generated from KBr pellet and attenuated total reflectance methods.

Selective adsorption and reactivity of dipeptide stereoisomers in clay mineral suspension

Preferential adsorption of dipeptide diastereomers (dialanine, Val-Ala) on clay mineral surfaces was observed. Significantly higher adsorption of dipeptides composed from only one type of enantiomer of amino acid units in comparison to those containing both L- and D-type of amino acid units in their molecules, was experimentally proven. This selectivity was explained in terms of different hydrophobic properties of diastereomers, which are probably controlled by intramolecular interactions between nonpolar and polar parts of dipeptide molecules affected by their stereochemistry. A significantly higher reactivity of stereoisomers composed from the same type of amino acid enantiomers to form amide bonds was proven as well. Theoretical study could distinguish different properties of the diastereomers. The results of the calculations indicate possible effects of molecular stability in the stereoselectivity during the adsorption and reactions of Ala 2 diastereomers.

Influence of sodium chloride, carbonates, and iron hydroxides on the viscosity of aqueous suspensions of clay minerals

The influence of sodium chloride solutions containing carbon dioxide on the viscosity of a maximally destroyed structure of suspensions of hydromica, kaolinite, natural iron-containing polymineral carbonate clay, iron oxides, and freshly prepared and dried montmorillonite is studied. The effect of physicochemical transformations of finely dispersed carbonates on the surface structure of a dispersed phase in suspensions of clay and iron oxide particles is considered. On the basis of the obtained results, a colloidochemical model for the destruction of ground barriers of storage ponds for mineralized water under the conditions of catastrophic phenomena is specified.

Influence of sodium chloride, carbonates, and iron hydroxides on the viscosity of aqueous suspensions of clay minerals

Influence of sodium chloride, carbonates, and iron hydroxides on the viscosity of aqueous suspensions of clay minerals