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Electron microscope images of a kaolin formed under weathering conditions. SEM images of vermicular aggregates of kaolinites (A) formed by planar and pseudohexagonal plates (B). TEM image of single pseudohexagonal plates of kaolinite (C).
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... usually show planar morphologies like the other kaolin minerals (nacrite and dickite) (Fig 4). However, some authors have suggested a relationship between the struc-tural iron and the kaolinite defects. There seems to be a decrease in crystallinity, and possibly in particle size, with an increase in iron substitution ( Herbillon et al., 1976;Mestdagh et al., 1980;Mestdagh et al., 1982;Cases et al., 1982). Balan et al. (2007) suggest that the proportion of Fe 3+ ions located near a stacking fault is similar to that occurring in normally stacked layers. This is an indication that the formation of stacking faults in kaolinite is not related to the occurrence of structural Fe 3+ ions as previously observed in other kaolinite samples (e.g. Brindley et al., 1986;Stone and Torres-Sánchez, 1988;Petit and Decarreau, 1990;Balan et al., 2000). More recently, high-resolution TEM research has shown that kaolinite crystals have a high density of stacking defects (Kogure & Inoue, 2005), and that the degree of stacking disorder varies among individual grains ( Kogure et al., 2010). Stacking faults are mainly caused by alternating t 1 and t 2 layer displacements and displacement of the octahedral vacancy, and/or by layer rotation. A high density of stacking defects in kaolinite produces lower ...
Citations
... Normalizing the adhesion force by the contact area to get the so called adhesion pressure (Pad) was proposed by Lau et al. to study the effect of cell maturation on biofilm-glass interaction of the P. aeruginosa strain (Lau et al., 2009). To the best of my knowledge, no efforts have been made so far to estimate the contact area between two interacting "non-ideal" systems, such as a single rod-shaped cell interacting with needlelike goethite particles (Huang et al., 2015), pseudo-hexagonal shaped kaolinite particles (Lázaro, 2015) or other particles with diverse shapes. ...
The wettability of soil particles defines important soil processes such as water infiltration in the soil and sorption of various substances on mineral surfaces. Soil water repellency (SWR) significantly impacts soil-water dynamics, often leading to reduced growth rates and crop yields. This phenomenon arises from hydrophobic coatings formed on soil particles by non-living organic compounds such as waxes, alkanes, fatty acids, free lipids and amphiphilic molecules.
While previous research on soil microorganisms mainly focused on their degradation activities, recent findings indicate a neglected aspect: the direct involvement of these microorganisms in hydrophobic interactions with soil particles modifying soil wettability. Specifically, it was found that the coverage of mineral particles by Gram-negative soil bacteria is associated with high water repellency of the produced cell-mineral association. Moreover, bacterial adaptation to drought stress increases cell surface hydrophobicity, suggesting a potential intensification of microbial induced SWR under changing environmental conditions. However, the mechanism, extent, and persistence of SWR caused by bacteria are poorly understood.
The aim of this work is thus to understand how a hypothesized increase of bacterial surface hydrophobicity, as an adaptation strategy to stress, affects cell adsorption onto mineral surfaces. My results are linked to scientific findings about cell growth processes under variations in soil moisture to estimate the short and long-term consequences of the drought stress on soil wetting properties. Key information at the single-cell level including cell size, stiffness, roughness and adhesion, obtained by improved atomic force microscopy (AFM) techniques, were linked to the stress induced changes of the bacterial surface hydrophobicity and surface composition obtained by contact angle and X-ray photoelectron spectroscopy (XPS) analyses, respectively. In addition, for the first time, a new AFM approach was developed to perform direct cell-mineral adhesion measurements taking the effect of contact area of these irregular materials into account. This helped to understand how cell growth environment and mineral type affect adhesion.
The findings of this study provide valuable contributions to both environmental sciences and biology by enhancing our understanding of soil-water dynamics. This knowledge helps to understand how the response of the ecosystem to environmental stress affects biological activities. In addition, it contributes to a broader understanding of soil processes such as the transport of fluids and the sorption of organic molecules and microorganisms on minerals surfaces. The results showed that stressed cells exhibit smaller size, higher stiffness and elevated protein content relative to unstressed cells. In addition, stress increases the contact angle in many strains, which indicates enhanced hydrophobicity due to the changes of the cell envelope structure. Such structural changes at the cell envelope also resulted to higher single-cell adhesion to hydrophobic than hydrophilic nanosurfaces (AFM tips) for stressed cells compared to unstressed cells. It is discussed that cell shrinkage induces protein crowding in the lipid bilayer while potentially releasing lipopolysaccharides (LPS) and lipids as membrane vesicles (MVs). The higher protein content increases the number of hydrophobic nanodomains per surface area, which enhances hydrophobic interactions and reduces affinity towards aqueous solution.
Considering that by stress the ability of water to spread on cell surfaces becomes weaker, it is addressed that, during drought conditions, cells tend to minimize exposure to the stressful medium (aqueous solution). This is confirmed by increased adhesion pressure of montmorillonite and goethite versus stressed compared to unstressed cells due to increased hydrophobic interactions. In other words, the cells shield themselves from the stressful medium by adsorption to the mineral phase. The role of hydrophobic interactions is evident by the absence of stress induced increase of adhesion pressure towards quartz. Hence, quartz with high hydrophilicity consistently exhibits surface wetting during separation from the cell surface regardless of cell condition. Nevertheless, the unexpected weaker adhesion pressure towards kaolinite under stress could not only be described by its wetting characteristics. The interfacial properties of this mineral are highly affected by the specific surface (basal, edge or both planes) interacting with the cell surface as discussed in the thesis.
Based on my findings and other research, a comprehensive model that elucidates bacterial behavior and function throughout a drying-rewetting cycle is introduced. In conclusion, a microbial induced soil hydrophobizing effect is suggested, albeit its persistence appears to be sensitive to drought periods, showing only transient impacts among frequent shifts in moisture content. Furthermore, the observed increase in cell surface hydrophobicity plays a critical role in enhancing bacterial survival, fostering dynamic “beneficial” interactions within the soil which maintain plant productivity under stress conditions. Nonetheless, extended periods of severe dehydration, surpassing seasonal fluctuations, could lead to the cumulation of hydrophobic materials in the soil matrix upon cell decay, which could feedback into persistent hydrophobizing effect. This emphasizes the importance of understanding the balance between the dynamics of soil microbes and the prolonged environmental stressors for sustaining soil health and productivity.
... Secondly, due to the specific properties of the filler, it was assumed that the basic performance parameters of the obtained foams would be improved, including the rebound elasticity or SAG factor. Previously conducted research on the use of plant biofillers has shown that their addition into the polyurethane matrix results in a decrease of functional properties [24]. Therefore, considering the need to develop more sustainable polyurethanes dedicated to the upholstery industry, the aim of this research was to obtain cheap nanocomposite flexible polyurethane foams with improved thermal and mechanical properties. ...
... Ultimately, choosing a comfortable mattress or piece of furniture is a subjec matter and always depends on individual preferences. These results show b improved performance properties than those obtained in a previously published stud agricultural industry waste [24]. This is mainly attributed to the specific propertie halloysite nanoclay. ...
... Ultimately, choosing a comfortable mattress or piece of furniture is a subjective matter and always depends on individual preferences. These results show better improved performance properties than those obtained in a previously published study on agricultural industry waste [24]. This is mainly attributed to the specific properties of halloysite nanoclay. ...
Nanocomposite flexible polyurethane foams (nFPUfs) were obtained by modifying the polyurethane formulation by adding a halloysite nano-filler in the amount of one to five parts by weight per hundred parts of used polyol (php). Flexible polyurethane (PU) foams with an open-cell structure and with a beneficial SAG factor were obtained. Premixes with nano-filler had a lower reactivity than the reference PU system. This favored the production of smaller cells, but with a more rounded shape in comparison with the REF foam without the nano-filler. During the study, the morphology and physical and mechanical properties were characterized, including apparent density, compressive stress, rebound flexibility, SAG factor, closed-cell content, and thermal stability, and compared with the properties of the unmodified reference foam. Scanning electron microscopy (SEM) showed that the cell structures of all prepared foams were open, and the cell size decreased with increasing nano-filler content. Apparent densities, SAG factors and rebound flexibilities of the foams increased with the increase of nano-filler content, while the resistance to permanent deformation showed the opposite trend. The proper selection of raw materials and optimally developed polyurethane formulations allow for obtaining environmentally friendly foams with favorable functional properties, taking into account price and the needs of sustainable development in the synthesis of flexible foams dedicated to the upholstery industry.
... Although the form of nanotubes are the most common morphology of halloysite. However it has also been reported that there are other various morphologies (spheroidal, platy, etc.) of halloysite from literature [44,45]. The platy halloysites (HNP) were also frequently reported [46][47][48][49]. ...
Polyurethane incorporated with nanofillers such as carbon nanotubes, basalt fibers, and clay nanoparticles has presented remarkable potential for improving the performance of the polymeric composites. In this study, the halloysite nanofiller-reinforced polyurethane elastomer composites were prepared via the semi-prepolymer method. The impact of different halloysites (halloysite nanotubes and halloysite nanoplates) in polyurethane composites was investigated. Scanning electron microscopy, X-ray diffraction, infrared spectroscopy, electronic universal tensile testing, and acoustic impedance tube testing were employed to characterize the morphology, composition, phase separation, mechanical properties, and sound insulation of the samples. The composite fabricated with 0.5 wt% of halloysite nanotubes introduced during quasi-prepolymer preparation exhibited the highest tensile strength (22.92 ± 0.84 MPa) and elongation at break (576.67 ± 17.99%) among all the prepared samples. Also, the incorporation of 2 wt% halloysite nanotubes into the polyurethane matrix resulted in the most significant overall improvements, particularly in terms of tensile strength (~44%), elongation at break (~40%), and sound insulation (~25%) within the low-frequency range of 50 to 1600 Hz. The attainment of these impressive mechanical and acoustic characteristics could be attributed to the unique lumen structure of the halloysite nanotubes, good dispersion of the halloysites in the polyurethane, and the interfacial bonding between the matrix and halloysite fillers.
... One difference is, kaolin has a plate-like structure, whereas HNT has a tubular morphology. Because of this morphology, HNT has a higher water content which includes a monolayer of water separating the unit layers in HNT 29 . ...
The development of a facile and efficient method for the fabrication of ceramic membranes fills a vital gap in the ceramic membrane manufacture research field. Ceramic membranes are relatively high in cost due to the cost of raw materials (metal oxides) as well as the energy required during the sintering stage of the fabrication process. In this study, a ceramic membrane made of low-cost halloysite nanotubular (HNT) clay is fabricated through a die press process and sintered at temperatures notably lower than those required of raw materials in commercial membranes. The features of the membrane were evaluated in terms of chemical properties, surface characteristics, hydrophilicity, durability, oil rejection performance, and antifouling properties. The pore size, porosity, and water permeability corresponding to the optimum membrane composition: halloysite: Al 2 O 3 : starch as 60:25:15 wt.% were found to be 230 nm, 62.4%, and 1040 LMH/bar, respectively. The membrane demonstrated to be superhydrophilic in air and superoleophobic underwater. The performance tests were conducted with oil emulsions. Oil-water rejection tests were conducted at different concentrations of oil-in-water emulsions (724 and 1014 mg/L) and oil rejection was observed to reach more than 99%. The flux recovery ratio (FRR) of the membrane in the first filtration cycle when treating the lower oil concentration emulsion was 54% greater than the FRR corresponding to the higher oil concentration emulsion. However, in the next filtration cycle, the FRR of the ceramic membrane was 30% greater for the higher oil concentration emulsion which could be attributed to the formation of an oil film, preventing further oil particle penetration in the membrane matrix. The testing with real produced water from gas extraction indicated that the novel HNTs-based ceramic membrane performed well in feed solutions with high total dissolved solids content and can be used for produced water pretreatment before reverse osmosis membranes if the produced water to be desalted. The results from this work show that the developed ceramic membrane is a promising, low-cost alternative to the ones existing in the current market for oily wastewater treatment.
... Otro elemento que tuvo un papel preponderante en la formación de los biomorfos, fueron los minerales presentes en la primera etapa de la Tierra. Se ha reportado que los minerales con alto contenido de silicatos, son el grupo de minerales de mayor abundancia en la corteza terrestre, además se encuentran relacionados con sucesos geológicos, y también se encuentran en suelos y rocas erosionadas hidrotermalmente 7,8 . Dentro de los minerales ricos en silicio se encuentra la lizardita, que forma parte de los filosilicatos, comúnmente denominados silicatos de hojas. ...
Entre los grandes misterios de la ciencia, el origen de la vida es uno de los más difíciles de descifrar. Para rastrear lahistoria de la vida en la Tierra, se recurre al estudio de las rocas buscando microestructuras que puedan ser restos de la vida primitiva. El precámbrico fue un periodo de grandes modificaciones geológicas, comenzando a surgir las formas de vida primarias. Debido a los avances, se ha confirmado que en las condiciones de la Tierra primitiva era común encontrar agua con pH alcalino, favoreciendo la autoorganización de pequeñas moléculas minerales formadas de silico-carbonatos de metales alcalinotérreos. Entre otras cosas, estas eran capaces de formar estructuras inertes que tienen una forma, textura y una simetría similar a las de los seres vivos, las cuales han sido denominados biomorfos. El objetivo del proyecto fue evaluar la síntesis de biomorfos sobre un mineral en diferentes condiciones atmosféricas.
... Otro elemento que tuvo un papel preponderante en la formación de los biomorfos, fueron los minerales presentes en la primera etapa de la Tierra. Se ha reportado que los minerales con alto contenido de silicatos, son el grupo de minerales de mayor abundancia en la corteza terrestre, además se encuentran relacionados con sucesos geológicos, y también se encuentran en suelos y rocas erosionadas hidrotermalmente 7,8 . Dentro de los minerales ricos en silicio se encuentra la lizardita, que forma parte de los filosilicatos, comúnmente denominados silicatos de hojas. ...
Entre los grandes misterios de la ciencia, el origen de la vida es uno de los más difíciles de descifrar. Para rastrear la historia de la vida en la Tierra, se recurre al estudio de las rocas buscando microestructuras que puedan ser restos de la vida primitiva. El precámbrico fue un periodo de grandes modificaciones geológicas, comenzando a surgir las formas de vida primarias. Debido a los avances, se ha confirmado que en las condiciones de la Tierra primitiva era común encontrar agua con pH alcalino, favoreciendo la autoorganización de pequeñas moléculas minerales formadas de silico-carbonatos de metales alcalinotérreos. Entre otras cosas, estas eran capaces de formar estructuras inertes que tienen una forma, textura y una simetría similar a las de los seres vivos, las cuales han sido denominados biomorfos. El objetivo del proyecto fue evaluar la síntesis de biomorfos sobre un mineral en diferentes condiciones atmosféricas.
... Kaolinite does not impact the mechanical and physical characteristics of the claystones [34], because it is rarely chemically active, unlike other clay minerals [35]. The presence of kaolin may also indicate near surface, freely draining environment [38], because it can be derived from primary minerals through dissolution process of primary minerals such as feldspars, biotite, and muscovite, under humid and temperate prevalent climatic conditions [37]. The process of kaolinitization requires intensive weathering under warm to tropical temperatures and high rates of fresh water percolation through feldspar and other minerals in [38] and [39]. ...
... The mineralogical data is well corroborated with the SEM data presented in 6aii, 6bii and 6cii respectively. The kaolinites usually show planar morphologies like the other kaolin minerals [37]. The platy grains of kaolinite are well shown in figure 6cii. ...
The claystones, with varieties of application, can be pivotal to boosting Nigerian economy. The Maastrichtian claystones of Enagi Formation at Share and Tshonga areas, Bida Basin, Nigeria were investigated to determine their mineralogy, geotechnical properties and their industrial applications. X-Ray diffractometry (XRD) and Scanning Electron Microscopy (SEM) were employed to determine their mineralogy. The particle size distribution (PSD), Atterberg limits, permeability and firing characteristics were probed. The claystones contain mainly kaolinite (20%-22%) while the main non-clay mineral is quartz (45%-62%). Other minerals include plagioclase (2%-15%), mica (5-15%), anatase (3%), pyrite (2%) and ilmenite (3%). PSD shows that sand ranges from 22% to 43%, while the clay ranges from 14% to 34% and silt varies from 46 to 56%. The Share claystones are more clayey while the Tsonga's are more sandy. The liquid limits, plastic limit, plastic indices and activity range from 43% to 71%, 17% to 31%, 25% to 40% and 0.6 to 2.0 respectively. The claystones have low to medium expansivity, and medium to high plasticity index which suggest suitability as attenuation layer. The Tsonga claystone has a higher coefficient of permeability of 5.826x 10-6 cm/sec than Share's (5.173x10-6 cm/sec). The low permeability may suit the claystones as attenuation layer. The firing test shows presence of expansive clays and increased level of mobile iron-bearing minerals with grey to yellow colour. The study concludes that the claytones can be used in paper making, barrier lining, bricks, pottery and ceramics which can add to increasing resource base of Nigeria.
... These include kaolinite, dickite, nacrite, halloysite, antigorite, chamosite, chrysotile and cronstedtite [6,7]. Kaolinite is of special geologic relevance because can be found abundantly in soils and hydrothermally eroded rocks [8,9]. The geologic origin of kaolinite has been inferred through studies that include geomorphologic context, the analysis of trace elements and the associated mineralogy. ...
The origin of life is associated with the existing environmental factors of the Precambrian Era of the Earth. The minerals rich in sodium silicates, in aluminum and in other chemical elements, such as kaolinite, were among the factors present at that time. Kaolinite is an abundant mineral on our planet, which indicates that it possibly had an essential role in the origin of the first blocks that constructed life on Earth. Evidence of this is the cherts, which are rocks with a high concentration of silica that retain the vestiges of the most ancient life on our planet. There are also inorganic structures called biomorphs that are like the cherts of the Precambrian, which take on a morphology and crystalline structure depending on the chemical molecules that make up the reaction mixture. To evaluate the interaction of kaolinite with DNA, the objective of this work is to synthesize biomorphs in the presence of kaolinite and genomic DNA that comes from a prokaryote and a eukaryote microorganism. Our results show that the difference between the prokaryote DNA and the eukaryote DNA favors the morphology and the crystalline phase of the calcium silica–carbonate biomorphs, while in the case of the barium silica–carbonate biomorphs, the environmental factors participate directly in the morphology but not in the crystalline phase. Results show that when a mineral such as kaolinite is present in genomic DNA, it is precisely the DNA that controls both the morphology and the crystalline phase as well as the chemical composition of the structure. This fact is relevant as it shows that, independently of the morphology or the of size of the organism, it is the genomic DNA that controls all the chemical elements toward the most stable structure, therefore allowing the perpetuation, conservation and maintenance of life on our planet (since the origin of the genomic DNA in the Precambrian Era to the present day).
... Halloysite is a silicate clay mineral that belongs to the Phyllosilicate group, as a dioctahedral type (1:1) (Berthier, 1826;Joussein et al., 2005;Bauluz, 2015), where each layer is composed of a tetrahedral plate (Si-O). The Al-OH octahedral sheet is similar to that of kaolinite, while the halloysite has an overall higher water content and anisotropy in the interlayer voids. ...
... The chemical formula for halloysite is AL2Si2O5 (OH) 4. nH2O when n = 0 for halloysite of type 7A° and n = 2 for halloysite of type 10A° (Joussein et al., 2005;Yuan et al., 2015;Ahmad and Kumar, 2020). In this paper, the terms halloysite (10A°) for the wet mineral, and halloysite (7A°) for the dry form are used as recommended by the AIPEA Nomenclature Committee (Joussein et al., 2005;Bauluz, 2015). ...
Nanotube halloysite prepared from Iraqi kaolin clay and kaolinite, were used as a filler in the manufacture of styrene-butadiene rubber (SBR) in order to improve its properties. Halloysite and kaolinite ratios added to the SBR components ranged between 20 - 100 Phr. The physio-mechanical tests showed that SBR matrixes with the nano-halloysite filler was more effective than with the kaolinite clay alone as a filler. The increase in tensile strength and elongation of SBR using nano-halloysite filler was 89% and 91% compared to that using kaolinite alone which gave 83% and 87%. Results of the scanning electron microscope (SEM) of nano-halloysite showed a regular distribution within the SBR, while it showed agglomerations and an irregular distribution of kaolinite within the SBR. These properties revealed weakness in the interfacial interaction between kaolinite and SBR. Thermogravimetric analysis (TGA) of SBR sample filled with nano- halloysite of 40 Phr showed higher thermal stability than the SBR sample filled with 40 Phr kaolinite..
... An illustrative and analytical example has been presented in Fig. 4. Kaolinite is a mineral with the chemical formula of Al 2 Si 2 O 5 (OH) 4 , containing ~ 13.9% OH. The internal crystal structure consists of the alternating of two-layers (at a 1:1 ratio), namely a tetraheral layer (consisting of SiO 2 ) and a hydrated octahedral layer (consisting of Al 2 O 3 ) 42 . These layers are close in proximity, not allowing for the water molecules to connect the octahedral/tetrahedral structures, which is possible in other clay minerals. ...
Metakaolin (MK) is one of the most sustainable cementitious construction materials, which is derived through a direct heating procedure known as calcination. Calcination process takes place substantially lower temperatures than that required for Portland cement, making it a more environmentally sustainable alternative to traditional cement. This procedure causes the removal of hydroxyl water from the naturally occurring kaolin clay (Al2Si2O5(OH)4 with MK (Al2O3.2SiO2) as its product. Kaolin naturally exists in large amount within 5̊29′N-5̊35′N and 7̊21′E-7̊33′E geographical coordinates surrounding Umuoke, Obowo, Nigeria. Alumina and silica are the predominant compounds in MK, which provide it with the pozzolanic ability, known as the 3-chemical pozzolanic potential (3CPP), with high potential as a cementitious material in concrete production and soil stabilization. Over the years, researchers have suggested the best temperature at which MK is derived to have the highest pozzolanic ability. Prominent among these temperature suggestions were 800̊C (3CPP of 94.45%) and 750̊C (3CPP of 94.76%) for 2 hours and 5 hours’ calcination periods, respectively. In this research paper, 11 different specimens of Kaolin clay obtained from Umuoke, Nigeria, were subjected to a calcination process at oven temperatures from 350̊C to 850̊C in an increment of 50̊C for 1 hour each to derive 11 samples of MK. The MK samples and Kaolin were further subjected to x-ray fluorescence (XRF), scanning electron microscopy (SEM) and x-ray diffraction (XRD) Brunauer–Emmett–Teller (BET)tests to determine the microstructural behaviour and the pozzolanic properties via the 3CPP as to exploit the best MK with the highest cementing potential as a construction material. The results show that the MK heated at 550̊C and 800̊C produced the highest pozzolanic potentials of 96.26% and 96.28%, respectively. The enhancement in pozzolanic potential at optimum calcination temperature is attributed to an increase in the specific surface area upon calcination of kaolinite confirmed by BET results. The SEM and XRD results further supported the above result with the strengthened crystal structure of the MK at these preferred temperatures. Generally, 550̊C is more preferred due to the less heat energy needed for its formulation during 1 hour of calcination, which outperforms the previous results, that suggested 750̊C and 800̊C in addition to longer hours of heat exposure.
