Minerals Kaolinite Research Articles

Mineralogical, Geotechnical Characterization and Stability of the Cut Slopes of Widikum and its Surroundings (North-West Cameroon)

The Widikum highlands and its surroundings are located in the North West Region of Cameroon. These five last years, landslides are frequently affecting movement on this portion of the highway. An investigation for understanding the mechanism of these phenomena was recently performed to clarify and to propose suitable remediable solutions. The study included mineralogical and geotechnical characterization of the local soil materials. The X-ray diffraction mineralogical analysis on clay fractions reveals the presence of phyllitic minerals (kaolinite, gibbsite, montmorillonite, illite and biotite). Associated minerals are mainly represented by quartz. Montmorillonite has the small crystal and largest surface which aid in increasing its adsorptive capacity. Clayed minerals can cause swelling and consequently the change or variation of the mechanical characteristics of the materials. The natural water content of weathered products vary from 27 to 47.4% which are close or even lower than the liquid limit included between 59.4 and 71.9%, this justify their unstable character. In addition, the high plasticity index ranges between 17.9 and 29.3% and is indicative of plastic materials thus very sensitive to creep. Moreover, the saturation ratio is very high (60 - 96%) thus attesting to their quasi saturated state. It is advisable to reduce the height of the steps to 2.3m by opting for a bench of 3m and adopting an inclination angle of β = 37.5°. Building retaining structures as well as eucalyptus and vertiva grass planting is recommended to reduce landslide incidences.

Taxa de Dissolução do Plagioclásio em uma Bacia de Drenagem Granito-Gnáissica de uma Floresta Ombrófila Densa Montana

A 180 ha area in the headwater of Paquequer watershed, a drainage system located at the Teresopolis municipality, was selected for the evaluation of chemical weathering from collected river water samples in February and August 2013 in a granitic-gnaissic substrate free of direct anthropogenic influence for being located in a conservation unit (Serra dos Orgaos National Park). The study area has a native forest cover, an altitude range of 1100-1900 m and an average annual rainfall of 2800 mm. The dissolved elements (Na, Mg, Ca, K, Si, Al) were analyzed by inductively coupled plasma spectrometries and the anions Cl - and SO 4 2- , by ion chromatography. These results, combined with the concentration data of nitrogen and phosphorus compounds (Alvim, 2016), the atmospheric deposition (Rodrigues, 2006), and the litogeochemistry (Zorita, 1979; Tupinamba, 1999; Tupinamba et al., 2012) were used to generate the dissolution model of mineral, employing the PHREEQC software. The mass balance indicate Na as the main chemical specie due to weathering. Mineralogical data show plagioclase, quartz, k-feldspar and biotite as substrate’s most abundant minerals, among which only plagioclase has sodium in its composition. According to Goldich’s series (mineral stability to weathering), plagioclase was identified as the main weathered mineral in this assemblage, being consumed at a rate of 649 mol ha -1 year -1 and forming the minerals kaolinite and gibbsite, with the release of a minimum of 818 mols ha -1 year -1 and a maximum of 1490 mols ha -1 year -1 of dissolved silica in the river (measured value). Considering plagioclase as the main mineral responsible for Na flux in the basin, stoichiometric calculations in association with Si ratio, it was estimated that only from the plagioclase weathering, the soil should be composed by 14% of kaolinite and 86% of gibbsite in percentage relative of the two mineral phases. The quantitative analysis of the mineralogy (Rietveld method) confirmed the calculations, showing a soil composition 7% kaolinite e 93% gibbsite, and attested the importance of plagioclase weathering in fluvial hydrogeochemistry and soil composition.

Geochemical and mineralogical evidence for the supergene origin of kaolin deposits – Central Main Ethiopian Rift

The Belessa kaolin deposit in the western margin of the Central Main Ethiopian Rift was studied using geological, mineralogical, chemical and physical methods to understand its genesis and evaluate its potential suitability for different industrial applications. X-ray diffraction and Scanning Electron Microscopy were used to establish the mineralogical composition. Bulk chemical compositions were determined using ICP-MS and ICP-AES. The geology of the kaolin district is comprised of Miocene to Quaternary age rhyolite and pyroclastic tuff. The kaolin occurrence is located in the central part of the study area and is associated with rhyolite. The host rock is composed of quartz and alkali feldspar phenocrsyts set in a groundmass of very fine grained quartz, alkali-feldspar and plagioclase. The rhyolite is partially to completely altered to kaolin. The kaolin deposit is composed predominantly of kaolinite and quartz. The kaolinite minerals of the deposit have high structural order. The geological, mineralogical and geochemical studies indicate that supergene alteration played a major role in the formation of the Belessa kaolin deposit. The absence of quartz veining and alteration zones containing high temperature minerals precludes significant hypogene alteration. The Chemical Index of Alteration (CIA) and Chemical Index of Weathering (CIW) also show that the host rock experienced strong alteration and weathering. Furthermore, high Ce+Y+La values correspond to supergene-type alteration. The low P and high Cr+Nb concentrations also support a supergene origin. The physical properties, chemistry, mineralogy and crystal morphology indicate that the Belessa kaolin has potential applications for paper coating, filler (in paper, rubber, plastic and paint), ceramics, pharmaceuticals and cosmetics.

Impacts of Kaolin on the Thermal and Electrochemical Properties of Ternary Eutectic Molten Carbonate Electrolyte in the Direct Carbon Fuel Cell (DCFC)

Coal is the second largest energy resource used for electricity production in the world and is expected remain unchanged through 2030. The main problem of using coal in conventional combustion power plants is serious environmental pollution due to CO2 emissions. In this context, electrochemical conversion of solid carbon to generate electricity is one of the most efficient technologies using liquid electrolyte at high temperature which is environmentally friendly. Raw coal as a fuel has some advantages and disadvantages in terms of mineral impurities inhabited in the coal which affect the DCFC performance. Kaolin is a common mineral found in coal fuels which has an advantage over other impurities. It was demonstrated that clay impurities in the coal such as kaolin and montmorillonite react catalytically to enhance graphite oxidation in a half-cell set up DCFC and improve the cell performance [1]. Although other impurities such as alumina, anatase and pyrite have limited impacts on the electrochemical oxidation of graphite, quartz was presented a decline in the current density of electro-oxidation of graphite. Thermal investigation of different coal impurities into ternary eutectic carbonate mixture has been done to show the impacts of these impurities on the melting process and kinetics of the melting process [2]. However it isn’t obvious yet what the impacts of these impurities have on the electrochemical performance of the cell and which disruption or modification will happen with addition of them on eutectic carbonate mixtures. In this work different ratios of kaolinite mineral were purposely added to the ternary eutectic carbonate electrolyte to investigate the thermal properties of the mixture and its melting behaviour. Particularly, DTA data were analysed in terms of changing melting temperature of the mixture and the determination of activation energy using different heating rates to asses these effects. The effect of kaolinite on the half-cell performance of a DCFC was also examined by adding kaolinite with different ratios into the eutectic carbonate electrolyte. The OCP, current density and polarization performance have been measured for the half-cell set up and results compared for different ratios of kaolinite and pure eutectic. Reference: 1-Tulloch, J.; Allen, J.; Wibberley, L.; Donne, S. et al. Influence of selected coal contaminants on graphitic carbon electro-oxidation for application to the direct carbon fuel cell. J. Power Sources 2014, 260,140−14910.1016/j.jpowsour.2014.03.026 2-M.J. Glenn, J.A. Allen, S.W. Donne Thermal investigation of a doped alkali-metal carbonate ternary eutectic for direct carbon fuel cell applications Energy Fuels, 29 (8) (2015), pp. 5423-5433

Interaction Mechanism between Molybdenite and Kaolinite in Gypsum Solution Using Kerosene as the Flotation Collector

This paper aims to understand the fundamental interaction mechanism between molybdenite and kaolinite in gypsum solution using kerosene as collector. Micro-flotation tests were conducted to study the effect of gypsum solution on the flotation performance of mixed −74 μm molybdenite and −10 μm kaolinite mineral. The results showed that the recovery of molybdenite decreased from 86% to 74% while the gypsum solution concentration increased from 0 to 800 mg/L, indicating the detrimental effect of kaolinite on molybdenite flotation could be enhanced by gypsum solution. This is mainly caused by the slime coating of kaolinite on molybdenite through dissolved calcium ion of gypsum solution. In order to confirm the slime coating phenomenon, zeta potential distribution, scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements were used to investigate interaction characteristics and mechanisms. The zeta potential distribution results revealed that mixed samples had the value between signal molybdenite and kaolinite samples in gypsum solution, which proved the coating phenomenon of kaolinite on molybdenite. Moreover, the coating phenomenon was becoming more and more obvious with the gypsum solution concentration. The coating phenomenon of kaolinite on molybdenite surface was also directly observed from SEM results. The AFM results provided further evidence for the possibility of slime coating, as the adhesion force increased with the gypsum solution concentration, which means the aggregates of molybdenite and kaolinite were becoming more stable.

Clay minerals and isotopes of Pleistocene lacustrine sediments from the western Qaidam Basin, NE Tibetan Plateau

Abstract Since Singer (1984) reviewed clay minerals as they relate to paleoclimates, clay minerals have been used to reconstruct paleoclimates and environments. However, the paleoclimate information recorded by the paleo-clays in sediments will be overprinted or changed if the clay minerals undergo diagenetic transformations or post-depositional diagenetic changes, which are quite common. However, numerous studies still use clay minerals to reconstruct paleoclimates and paleo-environments. Uplift of the Tibetan Plateau since the Late Miocene has significantly impacted the sediments of the Qaidam Basin. However, due to the scarcity of fully dated sediment records, we know little about whether or not and/or how these clay minerals responded to this uplift. In order to understand their response to the uplift, in this study, we present the results of high-resolution profiling of the clay minerals from a 938.5-m borehole core (SG-1) from the Qaidam Basin (NE Tibetan Plateau). These clay minerals are mainly composed of illite, mixed layers of illite/smectite (I/Sm) and chlorite, with minor kaolinite and smectite. The clay minerals may have undergone early diagenesis. The δ18O-δD values of the interlayer water and the clay minerals imply the following. (a) The primary amounts of illite and chlorite were lower than those observed, while the primary amounts of smectite and kaolinite were higher than those observed; the amounts of clay minerals should be careful to be used to reconstruct paleo-environment singly; the changes in the illite “crystallinity” (Kubler Index) and chlorite “crystallinity” (Arkai Index) were related to changes in salinity and temperature. (b) Chemical weathering from 2.77 to 0.1 Ma was stronger than that at present. (c) The δ18O and δD of the interlayer water ranged from −11.8 to 82.95‰ and from −114.3 to 165.5‰, respectively, which was related to pore water and/or lake water undergoing strong evaporation. The isotopic composition of the interlayer water reflects variations in the pore water/lake water or of the reacting solutions, and records changes in environment. (d) The clay minerals recorded climate changes and uplift in the core, with a dramatic shift at 1.2 Ma and two different environment stages at 2.77–1.2 Ma and 1.2–0.1 Ma.

CONTAMINAÇÃO DE SEDIMENTOS DE FUNDO NAS BACIAS DE CAPTAÇÃO DE ABASTECIMENTO PÚBLICO DE CAXIAS DO SUL, RS

O presente estudo caracterizou a geoquímica dos sedimentos finos de fundo de arroios monitorados nas bacias de captação Faxinal e Maestra, Município de Caxias do Sul, RS, tendo como objetivo correlacionar os resultados de geoquímica multielementar com a rocha-fonte presente na área e a composição dos principais fertilizantes utilizados nas áreas agrícolas. Coletou-se amostras de sedimentos e de fertilizantes, que foram analisados por diferentes técnicas (granulometria, difração de Raios-X e ICP-MS). Os resultados obtidos foram interpretados com suporte de estatística descritiva e multivariada (Análise de Componentes Principais e Análise Fatorial), relacionando com o fator de enriquecimento. A granulometria indicou que os arroios possuem um sistema fluvial dinâmico com eventos de alta energia. A difração de Raios-X identificou a caolinita como argilomineral predominante. O fator de enriquecimento e os dados estatísticos sinalizaram discrepâncias geoquímicas para o Pb, Sn, Cr, Ni, Cu e Na. Os Elementos Terras Raras identificados nos sedimentos apresentaram razão média de (La/Lu)N = 5,39 e intervalo de variação IQR (La/Lu)N de 2,46 à 8,41. Os sedimentos de corrente dos córregos da bacia de captação Faxinal expõem contaminação e efeito acumulativo por metais pesados provenientes da aplicação de fertilizantes e fungicidas, enquanto que o excesso de sódio nos sedimentos da bacia de captação Maestra são resultantes da descarga direta de esgoto doméstico no recurso hídrico.

High-resolution clay mineral assemblages in the inner shelf mud wedge of the East China Sea during the Holocene: Implications for the East Asian Monsoon evolution

The inner shelf mud wedge of the East China Sea (ECS) is a high-sedimentation-rate fine-grained sediment unit that has preserved a continuous environmental evolution history since the last deglaciation. We present a high-resolution clay mineralogical study from Core MD06-3040 to semi-quantitatively evaluate terrigenous sediment contributions from various potential provenances throughout the Holocene. The results showed that the clay mineral assemblage is composed of dominant illite (34–49%), moderate smectite (16–41%) and chlorite (15–28%), and minor kaolinite (5–12%). Provenance analysis suggested that most fine-grained terrigenous sediments originated from the Yangtze River, with minor sediments derived from Taiwan island and negligible sediments from nearby Zhejiang and Fujian provinces. Time series variation in the contribution of the Yangtze source fluctuated in the range of 38–80%, whereas that of Taiwan island had a converse variation pattern from ~10% to ~55%, and the contribution of Fujian was relatively stable in the range of 7–11% throughout the Holocene. The fluctuations of clay mineral assemblages and variations of clay mineral contributions from different provenances of Core MD06-3040 were controlled by the variability of precipitation in the Yangtze drainage associated with periodic fluctuations in the East Asian monsoonal circulation.

Integration of SPOT-5 and ASTER satellite data for structural tracing and hydrothermal alteration mineral mapping: implications for Cu–Au prospecting

ABSTRACTThe integration of information extracted from the Syste`m Pour l’Observation de la Terre (SPOT) and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data, comprehensive field and mineralogy studies demonstrates that phyllic alteration zone associated with northwestern (NW)–southeastern (SE) structural fractures is a high potential zone for Cu–Fe–Au vein-type mineralisation in the Bajestan region, the Lut block, east Iran. The fractal pattern was calculated for fractures map using the Box-Counting algorithm to the SPOT-5 data. Statistical parameters of fractures, such as density, intensity and fractures’ intersection were also determined. Band composition, specialised band ratio and Spectral Angle Mapper (SAM) classification methods were implemented to the ASTER dataset for detecting hydrothermal alteration zones, such as propylitic, phyllic, argillic and gossan. Results indicate that the maximum value of the fractal dimension, intensity, density and the intersection of the fractures are concentrated in the NW and SE parts of SPOT image maps. In the other hand, phyllic alteration zone containing sericite, alunite, kaolinite and jarosite mineral assemblages was also identified in several zones of the NW and SE parts of the ASTER image maps. Integration of the results indicates the high potential zones for the occurrence of Cu–Fe–Au mineralisation in the Bajestan region.

Solvent-Kaolinite Interactions Investigated using the 3D-Rism-Kh Molecular Theory of Solvation

AbstractThe oil sands of western Canada represent the third largest hydrocarbon deposit in the world. Bitumen, a very heavy petroleum, is recovered from mined oil sands using warm water extraction followed by separation treatments to isolate the bitumen product. The high energy, water use, as well as tailings remediation challenges associated with the warm water extraction process raise major environmental concerns. Non-aqueous extraction using organic solvents at room temperature has been investigated extensively as an alternative to the warm water extraction process. The main challenge to the large-scale implementation of non-aqueous extraction is the retention of solvent in the tailings. The objective of this work was to present and validate a computational model for the interaction of solvents used in non-aqueous extraction with minerals, such as the abundant and adsorbent clay mineral kaolinite. The model system contained a periodically extended kaolinite platelet immersed in a solvent and all were treated at the atomic level using the 3D Reference Interaction Site Model with the Kovalenko-Hirata closure approximation (3D-RISM-KH) molecular theory of solvation. The solvent solvation free energy of interaction with kaolinite as well as site-specific adsorption energies and kinetic barriers for desorption were computed based on the solvent site density distribution functions. Moreover, the lateral and integrated density distributions were computed to analyze the organization of solvent at kaolinite surfaces. The integrated density distribution profiles were correlated with experimental adsorption isotherms. The results showed very strong adsorption of ethanol and weak adsorption of hydrocarbon solvents on kaolinite, which were in qualitative agreement with experimental solvent extraction reports. The model and these findings are valuable in understanding the mechanism of solvent retention in tailings after non-aqueous extraction and highlight the action of hydroxylated cosolvent additives to enhance extraction using nonpolar solvents.

Comparative analysis of physical and chemical characteristics of selected clays deposits found in Kebbi State, Nigeria

The intent of this paper was to explore the physical and chemical characteristics of clays in Kebbi State, Nigeria, and the clays were compared with standard clay which is considered with highest quality standard in casting. Clay’s deposits from Dukku River along River Rima, Jega River which is the tail end of River Niger and Yauri were investigated for their potentials as raw materials used for casting and ceramic industries. Samples were collected from three local governments’ areas at the bank of the Rivers. Chemical analyses of individual clay were determined by employing four different techniques as follows; Complexiometric Titration, Atomic Absorption Spectrophotometer (AAS), X-Ray Diffraction (XRD), and X-Ray Fluorescence (XRF). The data collected from the analyses revealed that the structures of clay minerals were mainly kaolinite, Smectite (bentonite), and illite, and non-clay minerals for the three places were mainly quartz, feldspars and gibbsite. The results obtained revealed high silicate clays and moderate alumina content with trace elements of oxides (Fe2O3, CaO, K2O, TiO2, MgO, MnO, Na2O) also present within acceptable limits. Physical tests results at 900°C and 1300°C were used to determine firing shrinkage, colour, and modulus of rupture, bulk modulus, apparent density, crack formation, apparent porosity, water absorption, and bulk densities. The modulus of rupture, bulk densities, and fired linear shrinkage of all the samples increase with increasing firing temperature. The findings of this work revealed that the clays minerals from Dukku and Yauri had the necessary properties for the foundry work and refractory applications, but clays from Jega, can be exploited for commercial purposes after beneficiation by reducing the level of iron, quartz and other impurities. Key words: Clay minerals, chemical analysis, firing characteristics, oxides.

Experimental investigation of thermomechanical behaviour of clay-rich sandstone at extreme temperatures followed by cooling treatments

The aim of this study is to investigate the influence of extreme temperatures (from 25° to 1000°C) followed by two cooling methods (both rapid and slow) on the mechanical behaviour of clay-rich Hawkesbury sandstone under uniaxial conditions. A separate set of samples was tested under continuous heating conditions without cooling to compare the results with those for cooled samples. The stress-strain behaviours were analysed, with simultaneous recording of the acoustic signals and the failure mode. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were also performed to understand the changes observed in the mechanical tests. According to the results, the mechanical, mineralogical and microstructural characteristics of clay-rich sandstones are largely dependent on the thermal field, and, regardless of the cooling method, the compressive strength, Young’s modulus, crack initiation stress and crack damage stress appear to increase when the preheating temperature increase from 25 °C to 600 °C and decrease with increasing preheating temperature for temperatures greater than 600 °C. The SEM results confirmed the transformation of the initial hexagonal kaolinite mineral structure into a fibre-like (needle-type) mineral structure, which is believed to be the reason for the strengthening phenomenon observed at preheated temperatures between 25 °C and 600 °C. Progressive dehydroxylisation of kaolinite in the sandstone cement at temperatures beyond 600 °C was found to be the main reason for the weakening and softening of the sandstone which was observed with increasing preheated temperature beyond 600 °C. Apart from these mineral degradations, induced inter-granular and intra-granular cracks at preheated temperatures beyond 600 °C also play a dominant role in the weakening of clay-rich sandstone.

Impact of interfacial Al- and Si-active sites on the electrokinetic properties, surfactant adsorption and floatability of diaspore and kaolinite minerals

The active sites of mineral surfaces play an important role in many industrial processes, such as mineral flotation and dewatering. This paper was aimed to investigate the effect of Al- and Si-active sites on the mineral crystal faces exposed to water on the electrokinetic properties, surfactant adsorption, and floatability of diaspore and kaolinite, which are, respectively, the valuable and gangue minerals in the processing of diasporic bauxite ores. Specifically, the acid treatment was used to change the physicochemical properties of diaspore and kaolinite minerals for their selective flotation. Microelectrophoresis method was used to determine the zeta (surface) potential of diaspore and kaolinite particles before and after the acid treatment as a function of pH. The change in the surface potential was analyzed applying the theory on the electrical double layers at the solid-solution interface. The proton donor–acceptor reactions occurring simultaneously on amphoteric alumina or/and silica sites of diaspore and kaolinite were considered. The mass balances were applied to link the surface active sites with the minerals charge and potential. Comparing the modeling with the experimental data revealed the significant decrease in the Al-active sites and increase in the Si-active sites by the acid treatment. Single mineral flotation and surfactant adsorption tests of diaspore and kaolinite before and after the acid treatment were carried out using sodium hexametaphosphate (HMP) and dodecylamine hydrochloride (DAH) as a depressant and a collector, respectively. After the acid treatment, the adsorption density of depressant on both diaspore and kaolinite decreased due to the reduced density of Al-active sites on the minerals surfaces. The changes of collector adsorption capacity and floatability of diaspore were very small while those of kaolinite were significantly increased. These changes were caused by decreasing the density of Al-active sites (covered by HMP and thereby preventing DAH adsorption) on both diaspore and kaolinite and increasing the density of Si-active sites of kaolinite (not covered by HMP and thereby facilitating DAH adsorption). The results clearly indicated that the acid treatment was shown to be conducive to changing the active Al- and Si-sites on diaspore and kaolinite and thereby improving their flotation separation.

A proposal for bauxite quality control using the combined Rietveld - Le Bail - Internal Standard PXRD method – Part 2: Application to a gibbsitic bauxite from the Paragominas region, northern Brazil

In the bauxite industry – exploration, beneficiation and refining – two main chemical parameters are used for quality control: available alumina (AvAl2O3) and reactive silica (RxSiO2) content. Both are determined using a wet chemistry procedure that simulates the Bayer process at laboratory scale. For gibbsitic bauxites, the subject of this study, the available alumina is associated with the ore mineral gibbsite, and the reactive silica is associated with the deleterious mineral kaolinite. A significant innovation for this industry would be to characterize bauxite ores using mineralogical parameters, i.e., the wt% of gibbsite and wt% of kaolinite via Powder X-ray Diffraction Analysis (PXRD), which has been employed elsewhere but has been time-consuming and imprecise. A recent proposal for quantification of the main mineral components of bauxite ores for quality control in bauxite mining was developed by Paz et al. (2018) using the combined Rietveld - Le Bail - Internal Standard PXRD method. In this work, the method is tested using a Brazilian bauxite ore from the Paragominas region (Pará state, northern Brazil), and the results are evaluated against those from traditional wet chemistry (AvAl2O3 and RxSiO2). The study concluded that the PXRD method was able to produce results that were directly comparable with those from tradition chemical methods, and with the advantage of requiring only a single analytical instrument.

Understanding Cationic Polymer Adsorption on Mineral Surfaces: Kaolinite in Cement Aggregates

We present a joint experimental and theoretical investigation into the adsorption of polycationic quaternary ammonium polymers on the clay mineral kaolinite. Within the cement and concrete manufacturing industries such polymers are used to improve the final product by inerting the adsorption capacity of the clay minerals for more expensive additives. The adsorption of the presently used polymer (FL22) was compared with both a similar variant, but without a hydroxyl group (Fl22mod) and uncharged polyvinyl alcohol (PVA). Experimental results show that adsorption of FL22 is higher than that of FL22mod at both pH 6 and at pH > 10 and that the adsorption of PVA is the highest. Theoretical density functional theory (DFT) results and simplified models consisting of the basal surfaces of kaolinite, with monomers of FL22, FL22mod and PVA gave monomer coverage per unit surface area of kaolinite, a comparison of the configurations of the relaxed models, formation energies and Mulliken charges. These results show that the polycationic polymers interact with the basal surfaces of kaolinite electrostatically, explaining the high affinity of these polymers for kaolinite surfaces in the experimental results. The hydroxyl groups of FL22 and PVA form hydrogen bonds with the basal surfaces of kaolinite in conditions of pH 6. The joint experimental and theoretical results suggest that, due to the presence of the hydroxyl group, the conformation of FL22 changes under pH, where at neutral pH it lies relatively flat to the kaolinite surfaces, but at higher pH, conformational changes of the polymer occur, thereby increasing the adsorbed quantity of FL22.

Calculation of Entropy of Adsorption for Small Molecules on Mineral Surfaces

We performed density functional theory calculations for small organic molecules adsorbed on calcite, quartz, and kaolinite mineral surfaces and calculated the entropy change as a result of adsorption. Our results demonstrate that the entropy contribution to the free energy is mainly independent of the mechanism of binding, but it is affected by surface coverage, molecule size, character, and degrees of freedom. Compared with experimental results for weakly bonded molecules, density functional theory calculations predict a higher loss of entropy as a result of adsorption, which can be used as the upper limit for estimating the entropy contribution for adsorption to a mineral surface. The study has demonstrated a linear relationship between the entropy of the adsorbed molecule and the gas phase entropy, which can be used to estimate the entropy contribution to the free energy of adsorption on minerals without explicit density functional theory calculations, which is an important step forward in predicting t...

Effects of minerals on steam distillation during thermal heavy-oil recovery: An experimental investigation

ABSTRACTAn experimental study was carried out to investigate the role of various clay and non-clay minerals present in reservoir formations on steam distillation process. Dead oil samples (100 g) of two heavy oil reservoirs with 30 g of water and 10 g of crushed rock mixed with different clay minerals were kept under steam pressure with 150, 200, and 250°C in a batch autoclave reactor for a period of 40 hours, and the results were compared with respect to the changes in the density, viscosity and chemical composition of remaining heavy oil. Three different clay minerals (bentonite, kaolinite, and sepiolite) were added to the crushed rock to observe their effects. Among these clay minerals, kaolinite had the greatest effect on steam distillation. Kaolinite has an inert surface compared to other clay minerals which can be considered as an catalytic effect to make easier the evaporation of the volatile components of heavy oil during steam distillation. On the other hand, bentonite which has a swelling property in the presence of water may not allow the entrance of oil molecules because of its low permeability has retard/decrease the evaporation of volatile components. In case of kaolinite addition, density and viscosity of remaining oil are the greatest comparing with the two other minerals added. In addition, the asphaltene content of the remaining oil after distillation increased compared to original oil sample for all added clay minerals.

Understanding Model Crude Oil Component Interactions on Kaolinite Silicate and Aluminol Surfaces: Toward Improved Understanding of Shale Oil Recovery

Shale oil is currently of interest for unconventional resource exploration and development. Understanding the mechanism of interaction between the complex mixture of organic compounds in shale oil and minerals making up the reservoir rock–oil interface will assist recovery. In this study, molecular dynamics simulation is used to study the adsorption characteristics of a model oil mixture within nanoscale intraparticle pores of kaolinite minerals, which form pore-filling structures in shale rock. To better understand the effects of oil composition, temperature, and pressure on the adsorption properties of the model oil mixture, a range of temperatures (298, 323, 348, and 373 K) and pressures (1, 50, 100, and 200 bar) representing up to reservoir conditions were used. This study shows that adsorption and arrangement of oil molecules is dependent on the surface of kaolinite and the distance away from it. The simulations show polar compounds are likely to be adsorbed on aluminol kaolinite basal surfaces, whil...

Минералы группы каолинита в нижнетриасовых отложениях севера Тимано-Печорской провинции

Минералы группы каолинита в нижнетриасовых отложениях севера Тимано-Печорской провинции

Green assembly of stable and uniform silver nanoparticles on 2D silica nanosheets for catalytic reduction of 4-nitrophenol

A facile, environment-friendly route is illustrated for the efficient assembly of stable and uniform silver nanoparticles (AgNPs) on the surface of two-dimensional (2D) silica nanosheets (SiNSs, derived from natural kaolinite mineral) via in-situ reduction using Sn(II) as reductant. Compared to the common reduction method using NaBH4 reductant, the loaded AgNPs on AgNPs/SiNSs nanocomposite showed higher purity, uniformity and stability (antioxygenation). The catalytic reduction of 4-nitrophenol (4-NP) over AgNPs/SiNSs nanocatalyst was almost complete within 40 s without stirring and the apparent kinetic rate constant kapp (80.19 × 10−3 s−1) is much higher than those of other substrate-supported Ag/Au nanocatalysts. The effects of support material and assembly approach of AgNPs on the catalytic performance were discussed in detail. The high turnover frequency (TOF) for AgNPs/SiNSs nanocatalyst (3.52 min−1) indicates that the high-density dispersion of uniform small-sized AgNPs on 2D SiNSs surface is responsible for the excellent catalytic property, which offer many active sites for effective contact with the reactants and fast interfacial electron transfer from the AgNPs surface to 4-NP. It exhibits the great potential of 2D silica nanosheets as support materials for the efficient assembly of uniform noble-metal nanoparticles. Moreover, the 2D AgNPs/SiNSs nanocomposite holds a stable catalytic efficiency (around 100%) over five reaction cycles. The high efficiency and convenience have been demonstrated by purifying the 4-NP polluted water in the “filtering and catalyzing” device, in which the polluted water could become colorless within 10 s.