Clay Minerals Kaolinite Research Articles

Visible-light-driven photodegradation of organic pollutants by simply exfoliated kaolinite nanolayers with enhanced activity and recyclability

The need for abundant photocatalyst in wastewater treatment is currently a must. A simple intercalation process was utilized to exfoliate Kaolinite clay mineral structure Al2Si2O5(OH)4 into two-dimensional nanostructured separated layers operated in visible light range. The intercalating agents were hydrazine hydrate and urea. Detailed characterization confirmed the nanolayered structures of kaolinite hexagonal nanosheets (NK). In addition, Bandgap energy was reduced based on intercalating agents from 3.45 to 2.48 eV as revealed by light absorption spectra. The quenching of PL spectra for the nK has also been ascribed to the suppression of charge carrier recombination. The exfoliated nK was utilized to photodegrade Rhodamine B dye (RhB) and P-nitrophenol (PNP) as industrial pollutants in wastewater. The results showed 92.3% and 99.7% photodegradation of RhB and PNP within 180 min of visible-light irradiation utilizing the exfoliated NK by urea. We denote the boosted photocatalytic performance of this NK to the uncovered, low bandgap metal oxide inclusions on the exterior of NK besides the nitrogen doping due to exfoliation with urea. This simple exfoliation has modified abundant and stable clay nanolayers that are a promising alternative for the eminent nanostructured oxide photocatalysts to overcome the organic pollutants in wastewater at a high scale.

Improvement of Geo-engineering Properties of Expansive Clayey Soil by using Sodium Chloride and Bagasse Ash

Expansive soils contain minerals such as smectite clays that are capable of absorbing water accompanied by shrink and swell behavior and thus change in volume. The swell–shrink behavior of these soils could lead to instability of the structures found on them, specifically the light-weight structures and pavements. Expansive clay soil is encountered in most parts of Egypt. A comprehensive study was made in Sixth of October city to investigate the impact of lime sludge and bagasse ash as an industrial solid waste from sugar-cane factory and sodium chloride salt on geotechnical engineering properties of expansive soil. The macrostructural properties are quantified through laboratory testing for Free swell index, Plasticity index and infiltration tests. The microstructural aspects of the treated soil are observed through X-ray diffraction studies and SEM micrographs. The laboratory results showed that by increasing the lime sludge, Bagasse ash and NaCl concentrations the liquid limit decreased from 100% to 60% while the plastic limit increased from 100% to 90% respectively. In addition, the infiltration tests showed an increase in the infiltration rate from 10% to 80% when LS and Bagasse ash were added to the soil also the free swell decreased from 100% to 70 % sufficiently. XRD patterns showed the formation of new kaolin cementitious compound as the change of montmorillonite to kaolinite mineral took place due to the reaction of high amount of calcium ions produced from the stabilizer, the cation exchange took place between the calcium cation of the lime associated with the surfaces of the clay particles. The effect of cation exchange and attraction causes clay particles to became close to each other, this process is called flocculation which is accompanied by a series of pozzolanic reactions resulting in the formation of clay aggregates that are bound together by the new cementitious products such as calcium aluminate. Scanning Electron Microscopic images (SEM) and SEM micrographs determined the formation of organized dense clay matrices of aggregations that showed the reduction of Montmorillonite clay mineral peak intensities and an increase in kaolinite clay mineral peak intensities due to the change of expansive soil texture and reduction of interplanar spacing of the treated soil.

Physicochemical characterization of biogenic silica of the upper Numidian babouchite siliceous rocks, northwestern Tunisia

Physicochemical features (surface area, structural functional groups, thermal behavior), of the babouchite siliceous rocks from the upper Numidian formation, were explored in order to determine their possible uses. A suite of twelve-powder and fragments form were taken from Tabarka and Babouch areas, northwestern of Tunisia. The properties of the studied biogenic silica was measured using several techniques such as Scanning Electron Microscopy (SEM), Nitrogen physisorption measurements (N2-sorption), Fourier Transform Infrared Spectroscopy (FTIR) and Simultaneous Thermal Analysis (TGA-DSC). The studied siliceous rocks exhibited finely parallel-layered surfaces of microcrystalline quartz. Furthermore, the textural parameters of the babouchite samples showed the presence of mesopores with dissimilar size and distribution, which is demonstrated by SEM micrographs of the different fragments indicating pores with a size up to 4 μm. As well, the structure of the resulting adsorbents was characterized by specific surface area between 25 and 30 cm2g-1 and the average pore volume (V) is around 0.08 cm3g-1. The FTIR spectroscopy has clearly showed the predominance of quartz phase by the characteristic spectral bands of SiO2 crystal, mostly located between 1400 and 400 cm−1. Thermally, at above 900 °C, the babouchite siliceous rocks have a high thermal stability due to the dehydroxylation of kaolinite and other clay minerals minerals contained in these siliceous rocks.

Experimental Investigation into the Performances of Water Adsorption in Kaolinite Clay: Implications for Occupational Pneumoconiosis Prevention and Treatment

Pneumoconiosis is a systemic disease mainly caused by diffuse fibrosis (scar) of lung tissue due to long-term inhalation of productive mineral dust in occupational activities and retention in the lungs. The mineral dust concentrration can be effectively controlled using water-based mineral dust reduction technique. Therefore, the investigation into water-clay mineral dust interaction is useful for pneumoconiosis prevention and treatment. In this study, the adsorption performances for water molecules in kaolinite clay mineral were investigated. The findings reveal that the performances of water molecules adsorption in kaolinite clay mineral can be divided into primary adsorption and secondary adsorption. Under the lower vapour pressure, water molecules are primarily fixed in primary sites. At the higher vapour pressure condition, the secondary adsorption sites become the utilizable main adsorption centers. Primary adsorption is monolayer adsorption, while water molecules adsorption in secondary adsorption centers is occurred by the formation of water clusters.

Removal of toluidine blue from water using 1:1 layered clay minerals

Extensive use of color dyes in modern society resulted in their potential release into the environment. Dye removal often involved in sorption or reaction. For sorptive removal, materials with low cost and high efficiency are of great potential. In this study, the removal of toluidine blue (TB), a cationic dye, by 1:1 layered clay minerals kaolinite (KAO) and halloysite (HNC) was systematically studied under different physicochemical conditions. The TB removal was fast and equilibrium could be reached within an hour. The TB removal capacities were 47 and 149 mmol/kg by KAO and HNC slightly larger than their cation exchange capacity (CEC) of 37 and 120 meq/kg. The results indicated that both the CEC and specific surface area (SSA) of the minerals played a critical role in TB removal. Equilibrium solution pH and ionic strength had less effect on TB removal, suggesting preferred affinity of TB over other inorganic cations for mineral surfaces. X-ray diffraction data showed no interlayer expansion, indicating TB sorption sites were on the external surfaces of both minerals. The FTIR results indicated participation of N+ on the dimethyl group for TB sorption on negatively charged mineral surface. At the sorption capacities, TB may form a condensed monolayer on KAO surfaces, and a dimer or bilayer coverage on HNC surfaces, as suggested by molecular dynamic simulation. The results from this study suggest that clay minerals of high CEC and large SSA values would be good candidates for the removal of cationic dyes form water.

The effectiveness of the kaolin clay towards Monilia fructigena and Alternaria solani under laboratory conditions

Kaolin appears as odorless white to yellowish or grayish powder. Contains mainly the clay mineral kaolinite (Al2O3(SiO2)2(H2O)2), a hydrous aluminosilicate. It is used in the manufacture of china and porcelain and is also widely used in the production of paper, rubber, paint, drying agents, and many other products. It has a role as an excipient and an antidiarrhoeal drug and as an absorbent and filler including in some pesticide formulations. In this study, kaolin was tested under in vitro conditions against Monilia frucidena and Alternaria solani. The conducted tests have shown that it can be а potentially preventive fungicide against these plant pathogens. The substance was able to achieve full blocking of the germination of conidiophores and а growth of mycelium of Monilia frictigena at 0.1 % (m/v) concentration and at 0.3-0.5 % (m/v) towards conidiophores and mycelium of Alternaria solani.

Kaolin group minerals under pressure: The study of their structural and electronic properties by DFT methods

Kaolinites have a wide impact in many technological applications, and also are promising for their potential new uses in the future. Because these clay minerals naturally exist as fine particles, there are difficulties in making measurements of their bulk structural and electronic properties. Also, the occurrence of stacking faults and the presence of structural defects at the nanoscale, make these clay minerals quite complex systems to propose accurate models at the crystallographic scale.This work presents a study of six different kaolin group polytypes using calculations based on the Density Functional Theory (DFT), and includes the naturally occurring clay minerals kaolinite, dickite, and nacrite, and also other three pressure-induced polytypes that have been experimentally observed. The idealized structures were optimized using DFT methods, and their responses to hydrostatic pressure were theoretically analyzed from energy vs. volume and enthalpy vs. pressure data. From these, the bulk modulus for each polytype was predicted, and their relative stability and the potential transformations between structures were discussed. Finally, the electronic density of states for each polytype was calculated and compared to each other.The results indicate that although structurally these polytypes present significant differences between each other that lead to different elastic responses, from the perspective of the electronic properties they may be indistinguishable. The analysis performed in this work can be helpful as guidance and for interpretation in future experiments.

STUDY OF THE PROCESS OF OBTAINING ALTERNATIVE MOTOR FUELS USING VEGETABLE OILS

The growing shortage of oil resources makes it necessary to find alternative energy sources. The leading place among them today belongs to biofuels, both due to sufficient and affordable resources, and relatively advanced technologies for their production. The requirements of modern standards for the quality of the resulting gasolines limit the content of aromatic hydrocarbons in them to no more than 42% by mass. (Euro-3), and 35% of the mass. (Euro-4 and Euro-5). Therefore, studies on the involvement of vegetable raw materials in the processes of obtaining gasoline fractions are aimed either at obtaining highly aromatic gasoline with its subsequent compounding, or at searching for catalytic systems that make it possible, if any, to reduce the content of aromatic hydrocarbons in the composition of the resulting gasolines during joint cracking of the mixture of oil and vegetable raw materials. In this work, using the model oleic acid as an example, the mechanism of the conversion of fatty acids of vegetable oils during their catalytic conversion into hydrocarbons of the gasoline series was studied. The process was studied using a mixture of vacuum gas oil with vegetable oils as cracking catalysts, industrial cracking catalysts Omnikat-210P and Tseokar-600 in pure form and in their mixture with natural halloysite nanotubes. Halloysites belong to the family of kaolinite clay minerals with a high Al/Si ratio as compared to other aluminosilicates and have a predominantly hollow tubular structure and consist of layers of aluminum and silicon oxides that are rolled into tubes. The process of catalytic cracking of vacuum gas oil with the involvement of vegetable oils (waste vegetable oils taken from the Chudo-Pechka chain of stores) in the amount of 5 wt % was studied.

X-ray diffraction studies of onshore mud volcanoes in parts of the Upper Benue Trough, northeastern Nigeria

The mineralogical studies of clay from the onshore mud volcanoes discovered in parts of the Upper Benue Trough of Nigeria provide a clue about the geological formation from which the extruded mud originates. The study area is a part of the Cretaceous Upper Benue Trough filled with Early Cretaceous continental deposits and Late Cretaceous marine deposits, having a history of magmatism dating from the Albian to the Pleistocene. The study approach involves integrated inorganic geochemical analysis of the samples to reveal their composition and origin. The results of XRD analysis of the fresh clays from the mud volcano revealed the presence of quartz, kaolinite, and other clay minerals (illite-smectite), feldspars, and in much lower quantities, other accessory minerals including muscovite, evaporites, calcite and dolomite, trona, barite, goethite. The saprolite samples are composed mainly of quartz, kaolinite, smectite-illite associations, and feldspars, traces of goethite, calcite, and evaporate minerals (sylvite, halite). The presence of calcite, dolomite, sylvite, and halite suggests the marine origin of the rocks, while trona mineral is a non-marine evaporate. The coexistence of these minerals in some of the analyzed samples suggests the deposition of sediments in a transitional environment of deposition. Traces of marine minerals are present in some of the samples but completely absent in others collected from another site. This suggests that the source rock formations from which the material originated are within the Upper Bima Sandstone interpreted as being deposited in a non-marine environment or the Yolde Formation, which is known as a transitional unit (transitional between the outcropping continental Upper Bima Sandstone and marine Pindiga Formation).

Major ion chemistry and silicate weathering rate of a small Western Ghats river, Sharavati, southwestern India

Tropical, small mountainous rivers draining granite/granitic gneiss exhibit intense weathering rates and associated carbon dioxide sequestration, which has implications on the global CO2 budget. However, there is paucity of data from these catchments. This study aimed to understand silicate weathering rates (SWR) and CO2 sequestration rates (CCR) in a small tropical mountainous river, Sharavati in the southwestern India. Bicarbonates, Cl−, Na+, Ca2+ and silica, are predominant in the river, indicating their source from catchment rocks and atmosphere. Groundwater shows a similar abundance of major ions, indicating identical sources. Intense chemical weathering due to hot and humid climate, heavy monsoonal rains and associated river discharge are the main controlling factors of major ion chemistry in the Sharavati river. The presence of clay mineral kaolinite in the catchment corroborates with the above controlling factors. The calculated silicate weathering rate (SWR) is 27 t km−2. y−1 and associated carbon dioxide consumption rate (CCR) is 3.9 × 105 mol km−2. y−1. When compared to other small tropical river basins having similar climate and lithology, CCR of Sharavati is comparable to Jiuhua Mountain rivers, (South China) and twice that of Sorocaba River (Brazil). CCR is 3.9 times higher than the global average on account of the peculiarity of the terrain. It can be concluded from a comparative study of small tropical rivers, that rainfall and runoff are the main parameters controlling the weathering rates irrespective of catchment lithology.

Amending Potassic Fertilizer with Charcoal and Sago (Metroxylon sagu) Bark Ash to Improve Potassium Availability in a Tropical Acid Soil

In Ultisols and Oxisols, potassium (K) in the soil solution is leached from the rhizosphere before it interacts with soil colloids, or exchanged with other cations at the exchange sites of the soils because of the abundance of kaolinite clay minerals. These soils are highly weathered, low in organic matter, and low in pH, but high aluminium (Al) and iron (Fe) ions. Hence, K becomes unavailable for plants, and this compromises crop production and farmers’ profitability. The pH neutralizing effects of sago (Metroxylon sagu) bark ash and the ability of charcoal to chelate Al and Fe could be utilized to improve soil pH, reduce soil acidity, and improve K availability. The objective of this study was to determine the effects of amending muriate of potash (MOP) with charcoal and sago bark ash on selected soil chemical properties in a tropical acid soil (Typic Paleudults) over 90 days in a laboratory incubation. The proportions of charcoal and sago bark ash were varied at 20%, 40%, 60%, 80%, and 100%, but the MOP was fixed at 100% of the recommended rate. Selected soil chemical properties before and after incubation were determined using standard procedures. Results revealed that co-application of the soil amendments with MOP increased soil-exchangeable K compared with conventional practice. Moreover, amending the acid soil with charcoal and sago bark ash positively enhanced the availability of other base cations and soil cation exchange capacity (CEC). This was possible because the amendments increased soil pH and reduced exchangeable acidity, exchangeable Al3+, and exchangeable Fe2+. However, there was no significant improvement in water-soluble K (WSK) in the soil with or without charcoal and sago bark over the 90 days laboratory study. The findings of this study suggested that increasing soil pH could potentially improve soil K sorption capacity. Thus, the optimum rates of charcoal and sago bark ash to increase K availability were found to be 80% charcoal with 80% sago bark ash, 60% charcoal with 60% sago bark ash, and 80% charcoal with 40% sago bark ash, because these rates improved soil-exchangeable K+ and CEC significantly, besides minimizing soil-exchangeable acidity.

Co-Application of Charcoal and Wood Ash to Improve Potassium Availability in Tropical Mineral Acid Soils

Potassium (K) is a macronutrient required by plants for energy production, enzyme activation, formation of cell wall, production of protein, and photosynthesis. However, K in the soil solution is leached from the rhizosphere before it interacts with soil colloids because of the abundance of kaolinite clay minerals in mineral acid soils such as Ultisols and Oxisols. These soils are highly weathered, low in organic matter, low in pH, but high aluminium (Al), and iron (Fe) ions. As a result, K becomes unavailable for plants, and this affects crop production and farmers’ profitability. This problem has steered the attention to the application of amendments to minimise K loss. Animal manures, plant residues, and composts applications are some of the corrective measures taken to improve the K availability in tropical acid soils. However, there is dearth of information on co-application of charcoal and wood ash as soil amendments to improve the K availability and the changes they cause to the dynamic equilibrium of K in mineral acid soils. Hence, this review discusses the dynamics, availability of K, and proposed mechanisms involved when charcoal and wood ash are used to amend tropical acid soils. The optimisation and understanding of the role of charcoal and wood ash co-application as soil amendments have potential benefits to improve the K availability and physicochemical properties of mineral acid soils.

Wastewater Treatment from Heavy Metal Ions

The article is devoted to the sorption treatment of industrial effluents, which contain heavy metal ions (HMI) by the natural clay mineral kaolinite - an activated adsorbent. The main sources of HMI receipts are revealed - industrial and agricultural production. The influence of heavy metals on human health is considered. The results of studies of wastewater treatment using filtration through an activated adsorbent of Ni2+, Cu2+, Zn2+, Cr6+, ions, mixed waste are presented. Dolomite and magnetite were chosen as activators. The optimal composition of activators has been determined. When using the proposed method of wastewater treatment, separation into streams of chromium-containing and acid-base wastewater is excluded. The high quality of purified water with an activated adsorbent makes it possible to use it in closed water use systems. The cheapness and availability of natural clay adsorbents, high performance properties, allow us to offer it as an industrial sorbent.

Desorption Studies for Methylene Blue Dye Removal by Kaolinite

In wastewater treatment, the reusability of an adsorbent strongly relies on the feasibility of contaminant desorption from the spent adsorbent. This research aims to investigate the Methylene Blue (MB) release from the spent kaolinite clay mineral against a variety of desorbing eluent in an aqueous solution. Malaysia’s kaolinite was characterised using Scanning Electron Microscopy (SEM), surface area analysis, and Fourier Transform Infrared (FTIR) Spectroscopy. The MB desorption was performed using eluents of distilled water, solutions of HCl, NaOH, and NaCl (0.01 M and 0.1 M), and ethanol: water mixtures (30:70, 50:50, and 70:30 v/v ratios). It was found that the MB desorption only occurs in 0.1 M NaOH (pH 12.7). A 4.2% MB desorption was recorded in 1 hour and was increased to 19.5% within 24 hours desorption time. The pH change measurement also reveals the favorability for highly alkaline conditions for MB desorption. The overall finding indicates that the MB retention towards kaolinite is strong, and its adsorption occurs via electrostatic and hydrophobic interaction, as suggested by the FTIR analysis. Kaolinite is a good scavenger for removing the MB dye from contaminated water but requires a strong eluent in the desorption process for its future reusability process.

WHITE CLAY DEPOSITS AT DIFFERENT AREAS OF MADHABPUR AND BAHUBOL UPAZILA, HABIGONJ DISTRICT, BANGLADESH

A detail geological investigation was carried out in order to explore white clay deposite at 10 square kilometer areas of Madhabpur and 0.5 square kilometer areas of Bahubal Upazilas in Habiganj District of Bangladesh using hand auger and shallow drilling method. The whole surveyed area was identified for white clay deposits from qualitative as well as quantitative aspect. These deposits were marked at depths from 0.2 meter to 8.0 meter below the surface. Average thickness of white clay at Madhabpur and Bahubol area are 4.0 meter and 5.0 meter, respectively. The estimated reserve of white clay at Madhabpur area is about 68 million tons and that at Bahubal area is 2.8 million tons. Geological investigation suggests that the source rock near Tripura ranges was weathered, transported and deposited as feldspathic sandstone surrounding the present deposition of white clay. Later the sandstone was exposed and much of its feldspar content were weathered to the clay mineral (Kaolinite). Along with white clay peat, peaty clay, sticky clay and silica sand were also observed at depths ranging from 1.5 to 8 meter. Collected white clay samples are yellowish grey to light grey in color and highly compact in dry condition but pasty in wet condition. The dry white clay is soapy to feel, slakes in water, moderately sticky and plastic in nature. Al2O3 content ranged from 25.51 to 27.61% while average SiO2, and Fe2O3 content were found 54.58 and 3.872% respectively. Considering the physical and chemical properties the white clay of the studied area can be considered as moderate to good in quality. This white clay can use in ceramics and other industries. Therefore, this deposit of white clay may help to meet the current national demand and consequently to increase the economic growth.

Insights into the nano-structure of oil-brine-kaolinite interfaces: Molecular dynamics and implications for enhanced oil recovery

Oil-brine-clay minerals interactions play an important role in in-situ reservoir wettability, which govern the fluid flow during enhanced oil recovery, CO2 geosequestion and water remediation at subsurface. Kaolinite clay minerals are widely existed in subsurface reservoirs. Therefore, it is of vital importance to understand how kaolinite controls the in-situ wettability through the nanostructure of oil-brine-kaolinite interfaces. In this context, molecular dynamics (MD) simulation was therefore performed to compare the nanostructures at kaolinite surfaces as a function of brine salinity in the presence of organic materials. Acid component (decanoic acid) and base component (quinoline) were incorporated to evaluate their adsorption on kaolinite surface as a function of salinity. The density distribution and radial distribution function (g(r)) were calculated in high salinity water and low salinity water.The density distribution profile showed that the aluminol layer was decanoic acid wet while the siloxane layer was insensitive to both decanoic acid and quinoline regardless of salinity. The g(r) of Al and Si atoms in clay structure revealed that more water accumulated adjacent to the aluminol layer in low salinity water and screened out the ions and functional groups adsorption on the surface. However, less water accumulated around Si atoms in low salinity water than in high salinity water. The more accumulated water on aluminol layer than siloxane layer can explain the wettability (adsorption) differences between the aluminol layer and the siloxane layer. Furthermore, the MD results revealed that the decanoic acid was more responsive to salintiy variations than quinoline, which confirmed that acid component was the primary element in oil to determine wettability alteration. This work sheds light on the significant influence of mineral surface chemical species on oil-minerals adhesion as a function of ionic strength at molecular scale. This work also provides an overall practical framework, which predicts the wettability alteration with applications in enhanced oil recovery, CO2 geosequestration and water remediation.

Assessing Lignin Decomposition and Soil Organic Carbon Contents Across a Tropical Savannah-Rainforest Boundary in Guyana

The soils beneath the rainforest of Guyana have the potential to hold, and release, large stores of carbon under land use and climate change. Little is known about soil carbon stocks or molecular dynamics in this region. This study therefore aims to elucidate differences in the molecular (lignin and tannin) and bulk soil organic carbon (SOC) stocks in different ‘sub-environments’ along a rainforest-savannah boundary, setting a framework for further investigation into the soil carbon dynamics of the region. Bulk SOC analysis shows that Gleysols have the highest stocks, particularly those under rainforest vegetation (swamp and island forests surrounded by savannah), whereas Plinthosols have significantly lower SOC stocks. Texture and soil water content analysis indicates that predominantly clay soils play a role in high SOC stocks, whilst predominantly sandy soils prevent SOC stocks from accumulating. Clay and sand are present in both Gleysols and Plinthosols, to different extents. Analysis of lignin and tannin in surface soils of the sub-environments reveals clear differences in molecular composition. Heavily degraded lignin signatures in rainforest Gleysols suggests a surrounding physio-chemical environment which promotes their degradation. Conversely, Plinthosols beneath woodland within the savannah have the greatest amount of lignin and tannin products. The presence of the clay mineral kaolinite and iron oxide strengite in these soils indicates a low ability for protection or complexing of organic matter. Therefore, water content and microbial activity may play a more important role in the degradation of lignin and tannin, as well as the SOC stock. With the potential for future deforestation due to land use or climate change, the high lignin degradation of Gleysols indicates a vulnerability to savannah encroachment. Forest Islands isolated from the main forest biome are the most vulnerable to change, and could lose a significant proportion of their SOC stock in a transition to savannah.

Release of aggregation pheromone rhynchophorol from clay minerals montmorillonite and kaolinite

Release of aggregation pheromone rhynchophorol from clay minerals montmorillonite and kaolinite

Solid bitumen in shales from the Middle to Upper Jurassic Sargelu and Naokelekan Formations of northernmost Iraq: implication for reservoir characterization

Petrographic, organic, and inorganic geochemical analysis of the solid bitumen and host shales from the Middle and Late Jurassic-age Sargelu and Naokelekan Formations of the Banik section, northernmost Iraq, was undertaken. The aim was to understand their derivation and preservation, as well as examine the carbon and oxygen isotopes, and paleoredox proxies under which the solid bitumen and host sediments were deposited. Petrographic analysis of both formations revealed the presence of solid bitumen high reflectance (first phase) and solid bitumen low reflectance (second phase). The equivalent vitrinite reflectance indicates that the solid bitumen of the two formations probably accumulated within the shale reservoirs following oil migration from source rocks located within the same formations. Mineralogical study (XRD and SEM - EDX) revealed that the shales hosting the solid bitumen also contain clay minerals (illite, rectorite, chlorite, montmorillonite, and kaolinite) as well as carbonate minerals, quartz, alkali feldspar, and pyrite. Carbon and oxygen isotope data along with paleoredox indicators suggest that both the solid bitumen sources and host shales in both formations formed within a shallow-marine setting, most probably under anoxic conditions where water circulation was restricted.

A density functional theory (DFT) investigation of how small molecules and atmospheric pollutants relevant to art conservation adsorb on kaolinite

The physio-chemical properties of the clay mineral kaolinite – the main component of porcelain – play a vital role in understanding how a porcelain object interacts with its environment. Understanding these interactions is imperative for the development of non-destructive yet effective conservation methods to preserve, treat, and restore porcelain objects of cultural heritage importance. To gain insight into the surface properties and behavior of kaolinite across a wide range of environments, we use density functional theory (DFT) to probe how a representative set of small molecules and atmospheric pollutants interact with a native kaolinite (001) surface, both in vacuum and with explicit hydration. By investigating selected atmospheric pollutants, acids, and sodium salts under different conditions, we identify the scenarios that are most disruptive to the native kaolinite surface. Specifically, we demonstrate that protic acids and sodium salts generally interact with the surface more strongly than common small molecule pollutants. Our results also indicate that adsorbates containing a central sulfur atom with a positive oxidation state are particularly deleterious to the kaolinite surface. Furthermore, to explore the interactions between a fired or partially fired porcelain object and relevant chemicals, we also model a partially dehydrated kaolinite surface and probe its interactions with three selected adsorbates. The trends elucidated throughout this study allow us to suggest a series of guidelines for the care of porcelain objects.