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Abstract: Kaolinite was successfully intercalated by urea in a static and sealed condition at 95°C for 3.5h. The urea-intercalated kaolinite was applied for paper coating. The high shear rate rheologies were used to study the flowing properties of them and to stimulate the realistic coating paper at ultra high shear rate. The structure, morphology, chemical constitution, particle size distribution and rheological properties of the samples were measured by XRD, SEM, ICP-MS, particle size analyzer and by rheometer, respectively. The particle size of urea-intercalated kaolinite became finer with the growth of intercalation ratio. The rheological properties of slurries were changed from pseudo plastic behavior to complex flow and the solid content of slurries at the viscosity of 500mPa·s increased from 70.84 % to 74.09 % due to intercalation of urea. The urea-intercalated kaolinite improved slightly the properties of papers, while the better rheology could enhance the process of coating paper with ultra high speed. [Copyright &y& Elsevier]

Abstract: This work reports the project of thermal effects in mineralogy and texture of the paper sludge to employ them as pozzolanic material. For this reason, the chemistry and mineralogical composition has been studied, as well as its morphology by XRD, SEM and EDX. The initial sludge has been treated to 700, 750 and 800 °C during 2 and 5 h being observed that initial kaolinite becomes metakaolinite and that its pozzolanic activity with a paper sludge treated to 700 °C for 2 h is comparable to that of a commercial metakaolinite. The transformation of kaolinite after the dehydroxylation is to convert in amorphous metakaolinite. At the temperature mentioned above, calcite from the initial sludge is maintained active. It is concluded that the pozzolanic activity of metakaolinite is strongly related to the crystallinity of the original kaolinite. Well-ordered kaolinite is transformed into more reactive metakaolinite. [Copyright &y& Elsevier]

Abstract: In Spain, the paper industry recycles large amounts of waste paper in the new paper production process. Paper sludge thermal activation (calcination at 700 °C for 2 h) is an environment-friendly alternative source for metakaolinite (MK) to be used for the manufacture of blended cements or cement based materials. This paper could contribute to standardization of the use of new pozzolanic products in cement based materials and its use mixed with saturated lime dissolution. In this process are obtained zeolite, CSH gel, hydrotalcite-like compounds, hydrated aluminate tetracalcium and stratlingite. These materials are formed in different times of pozzolanic reaction. [Copyright &y& Elsevier]

Abstract The use of industrial waste as a cement addition often changes the composition and development of the hydrated phases and with them matrix performance and durability, in particular at later ages. The effect of the presence in blended cement of 20% to 50% kaolinite based activated carbon waste (ACW) on paste hydration has been characterized by means of XRD, SEM/EDX, TG/DTG, NMR and FTIR to identify and monitor the mineralogical phases forming in materials at ages of up to 180 d. The results showed that the main reaction products forming in the first 7 d included C-S-H gels, C 4 ACH 12 and C 4 AH 13 (hydroxy-AFm). Whilst monocarboaluminate (Mc) content declined with rising percentages of ACW, the amount of hexagonal phase hydroxy-AFm rose. Then microstructure of the C-S-H gels developing in the OPC and the 50% additioned paste differed. Compact C-S-H gel plates, and phyllosilicate-like laminar spongy microplates with high polymerised C-S-H gel formed in the blended cement paste. Highlights • The present paper shows new knowledges in low clinker cement manufacture • This paper studies the influence of high contents of clay waste in the mineralogy of cement pastes cured up to 180d. • ACW favoured the formation of C 4 AH 13 over C 4 AcH 12 • ACW favoured the compact C-S-H gel plates, and phyllosilicate-like laminar spongy microplates. [ABSTRACT FROM AUTHOR]

Alkali leaching is an effective desilication method for improving the alumina-silica mass ratio (A/S) of bauxite. The paper aims to study the kinetics of kaolinite dissolution and hydrosodalite precipitation during alkali leaching of kaolinite-rich diasporic bauxite. Alkali leaching of bauxite in NaOH solutions was studied at Na 2 O concentrations of 200–260 g/L, temperatures of 90–105 °C, and times of 30–150 min. The leached bauxites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) techniques. The rate equations describing kaolinite dissolution and hydrosodalite precipitation were derived by fitting the Avrami model. The results show that kaolinite with finer particle sizes was preferentially dissolved during alkali leaching, providing a material basis for the precipitation of hydrosodalite. Hydrosodalite was heterogeneously nucleated on the dissolved edges of some kaolinite and grew in both one- and two-dimensions, presenting acicular and lamellar morphology. The dissolution rate of kaolinite and the crystallization mechanism of hydrosodalite were primarily influenced by Na 2 O concentration and temperature. Both kaolinite dissolution and hydrosodalite precipitation were controlled by chemical reactions with activation energies of 70.152 (± 1.429) kJ/mol and 289.089 (± 2.063) kJ/mol, respectively, and the orders of reaction with respect to Na 2 O of 0.733 (± 0.070) and 7.165 (± 0.047), respectively. The kinetic equations describing kaolinite dissolution, hydrosodalite precipitation and even the leaching of SiO 2 were eventually modeled with Na 2 O concentration, temperature and time as variables. • The preferential dissolution of kaolinite occurs on particles with finer sizes. • Hydrosodalite is heterogeneously nucleated on the dissolved edges of kaolinite. • Hydrosodalite presents both one- and two-dimensional growth. • The kinetic equation for the leaching of SiO 2 is derived using the Avrami model. • The Avrami exponent is linearly related to temperature and Na 2 O concentration. [ABSTRACT FROM AUTHOR]

Managing clay-containing slurries during drying process remains a persistent challenge in various industries. Despite challenges of drying clay-containing-slurries, limited information is available. The aim of this study is to explore the drying performance of slurries containing kaolin and bentonite and gain insights into the underlying drying mechanisms. The research presented integrates drying experiments, rheology measurements, settling experiments, zeta potential measurements, FTIR, TGA/DTA, and SEM analysis. Bentonite-containing slurries retained more moisture due to their high-water adsorption capacity, with higher bentonite percentages extending drying times. The addition of Ca2+ ions reduced moisture content by replacing Na+ ions with smaller Ca2+ ions, making the slurries less viscous. The addition of Ca2+ disrupted the gel-like structure of bentonite as confirmed by SEM and FTIR. In contrast, kaolin-containing slurries maintain lower moisture levels owing to the non-swelling structure of kaolinite. SEM showed the formation of agglomerates for kaolin when Ca2+ was added The addition of Ca2+ ions had a subtle impact on drying rates, despite a slight increase in slurry viscosity probably due to the agglomeration of kaolinite particles. Both slurries exhibited three drying phases: rapid drying due to high moisture, a moderate phase with reduced rates, and a final phase of slowed drying as tightly bound moisture was harder to remove. This paper demonstrated the significance of understanding the drying processes of clay-containing slurries to enhance the overall drying efficiency. • Detrimental effect of clays on drying of clay-containing ores was observed. • Three different drying regions were observed for kaolin and bentonite slurries. • The addition of Ca2+ disrupted the gel-like structure of bentonite. • SEM showed the formation of agglomerates for kaolin when Ca2+ was added. • Ca2+ ions significantly improved drying of bentonite slurries but not kaolin slurries. [ABSTRACT FROM AUTHOR]

Coal gangue (CG) contains abundant rare earth elements (REEs), which is a potential REE resource. REEs are mainly present in clay minerals as hydrates. The adsorption, desorption, and diffusion of REEs-hydrates on the surface of clay minerals are the key to regulating the leaching effect of REEs. The paper focuses on the typical clay minerals kaolinite and REEs-hydrates and combines quantum mechanics and molecular dynamics methods to systematically study the adsorption, desorption, and dynamic diffusion behavior of REEs-hydrates in acid solution. The research results indicate that stable REEs-hydrates La(H 2 O) 9 and Y(H 2 O) 7 are formed, with ion bonds between REEs and water molecules. La(H 2 O) 9 and Y(H 2 O) 7 mainly interact with the kaolinite (001) surface through hydrogen bonding. Competitive adsorption is formed between water molecules, hydrated hydrogen ions, and REEs-hydrates. Water molecules and hydrated hydrogen ions occupy the adsorption active sites of REEs-hydrates and form a dense water molecular layer on the surface. The distance between H 3 O+ and REEs-hydrates and the number of H 3 O+ in the solvent layer affect the desorption and diffusion behavior of hydrates. The bonding law, dynamic desorption, and diffusion mechanism of REEs-hydrates can provide meaningful references for selective leaching of REEs from CG. [Display omitted] • Adsorption, desorption, dynamic diffusion of REEs-hydrates are investigated by DFT and MD simulations. • REEs-hydrates are adsorbed in pores of the Al O six-membered rings. • Hydrogen bonds are formed between REEs-hydrates and kaolinite surface. • Competitive adsorption occurs between H 2 O, H 3 O+, and REEs-hydrates. • Number and distance of H 3 O+ both affect adsorption and desorption of hydrates. [ABSTRACT FROM AUTHOR]

Abstract: In the past, different investigations have focused on waste containing kaolinite as an alternative source for recycled metakaolinite. However, it is well known that the activation conditions play an important role in the characteristics of the final product. This research presents an exhaustive study about the evolution of the mineralogical phases during the pozzolanic reaction of two metakaolinite by-products obtained from different activation processes: activation of paper sludge at lab scale (700°C and 2h) and at industrial scale (720–740°C and 20–30min) with a fluidized bed combustion system. It is shown that both metakaolinite by-products exhibit a different pozzolanic behavior, suggesting a direct influence on the subsequent performance of new blended cement matrices. The metakaolinite by-product obtained at lab-scale (MWL), generates an additional phase (carbonate/metakaolinite type structures) as predominant crystalline phase in the pozzolan/Ca(OH)2 system up to 28days of reaction. Stratlingite (C2ASH8) also appeared as minor stable phase after 7days of reaction. On the other hand, the metakaolinite by-product from industrial process (MWI) favors the formation of C4AH12 phase, whereas stratlingite was not identified. [Copyright &y& Elsevier]

Abstract The increasing of aluminum demand globally raises the interest in developing alternative technologies to produce alumina from non-bauxitic sources, especially clays. This paper studies the extraction of alumina from the kaolin ore excavated from the Irkutsk region, Russia through the leaching process, using aqueous solutions of sodium carbonate as a leaching agent. Before the leaching process, the kaolin ore and limestone charge was sintered. The sintering process achieves the dehydroxylation of the kaolinite, which is the main mineralogical phase in the kaolin and activates its transformation to metakaolin. Metakaolin is an amorphous Al Si phase, from which alumina could be easily leached. The annealed sintered material transform into dust that is suitable for the leaching process without any additional grinding. The sintering process was taken place in the temperature range 800-1400 °C for 1 h. The effect of briquetting pressure and sintering temperature on the recovery of alumina from kaolin, were studied. About 87% of the alumina in the kaolin was extracted at 1360 °C and briquetting pressure of 5 MPa. Highlights • In this work, the extraction of alumina from kaolin using the lime sinter process was investigated. • The effect of briquetting pressure and sintering temperature on the recovery of alumina were studied. • The interaction mechanism between the leaching agent and the sintered kaolin was also studied. [ABSTRACT FROM AUTHOR]

Abstract: This paper proposes a multi-level approach to data clustering and provides a novel approach to characterisation of clay soils by, effectively, looking at the same clay sample from different angles. It is shown that using this approach can help avoid detection of spurious clusters or skipping vital natural grouping in data. Muscovite, illite and kaolinite were identified by X-ray diffraction (XRD) in <4μm fraction of soil samples obtained from the periphery of an abandoned manganese oxide mine and semi quantified as major, minor and trace. Based on information inherent in the data attributes, useful rules for grouping the samples were generated and with the aid of multiple data clustering, applied to characterize the clay minerals occurrences in the soils. The paper found that the presence of large quantities of illite and kaolinite heavily influence the formation of clusters. When the most influential variables—LJ and KJ were taken out, the resulting model showed that muscovite traces play a vital role in initial cluster building and the importance matrix of inputs suggested inter-dependence between muscovite, kaolinite and illite traces as well as between them and minor quantities of illite. Dwelling on aspects of clay mineralogy and modelling sciences, the paper marks a significant departure from the conventional approaches to clay characterisation by showing how effectively data mining methods can be adopted in the area. For a successful approach to characterisation of clay minerals in African soils, the paper recommends to set-up data repositories that will provide scientific data sources and forums in a multi-disciplinary environment. This is particularly important as capturing interesting patterns requires expert knowledge describing the emerging natural groupings. [Copyright &y& Elsevier]

Kaolin available in Deopani, Assam of northeastern region of India was characterized by FTIR, XRD, DTA and by wet chemical analysis methods. The major impurities in the clay are quartz and siderite. Wet sieving of the clay by −53-μm sieve removes almost all the quartz and a major amount of Fe bearing impurities. The iron content of the clay may be reduced further by treating with wet high intensity magnetic separator (WHIMS) or leaching with organic acids. The effectiveness of various leachants follows the order: Oxalic>Oxalic+EDTA>Malonic>Citric acid. Almost all the nonstructural iron may be removed at room temperature by using 0.4 M oxalic acid solution. The leached clay may find use as a ceramic raw material and filler material for paper and other materials. [Copyright &y& Elsevier]

The mechanical behaviour of sands and clays subject to "normal" (plastic) compression are very similar, albeit at different stress levels, despite the differences in inter-particle interactions (Hertzian normal contact forces or similar for sand) and electro-chemical forces for clays. However the hysteretic behaviour of clay is very different to sand with clays exhibiting "springy" hysteresis loops and ratchetting volumetric compaction. This paper aims to show that whereas the "plastic" compression arises from degradation of macro particles, the "quasi-elastic" unload-reload behaviour is consistent with an increase in the number of platelet edge contacts as clay "stacks" rearrange and compact. [ABSTRACT FROM AUTHOR]

The development of thermal insulation materials with superior comprehensive properties is crucial to building energy conservation. This paper presents a kaolinite-based porous geopolymer type composite thermal insulation material through alkali activation, room temperature foaming technology, and the rock wool fiber reinforcement. The effects of rock wool fiber contents and heat treatment on the comprehensive properties of the kaolinite-based porous geopolymer were investigated. The addition of rock wool fiber can enhance the mechanical properties of kaolinite-based porous geopolymer, while heat treatment can generate a hierarchical porous structure, resulting in a dramatical improvement in thermal insulation performance. With a rock wool fiber content of 15 wt%, the sample exhibits a porosity of ∼90%, density of 0.118 g/cm3, thermal conductivity of 0.057 W/(m·K), and a maximum compressive strength of 0.66 MPa, increased by ∼22% compared to samples without addition of rock wool. Additionally, the optimized thermal insulation material followed waterproofing treatment exhibits excellent hydrophobicity with a contact angle of up to 98.5°. Therefore, this novel thermal insulation material not only has a simple manufacturing process and eco-friendly properties, but also showcases properties including lightweight construction, high strength, and low thermal conductivity. Consequently, it holds immense potential in the area of building energy conservation. [Display omitted] • Rock wool fibers were firstly used to reinforce the strength of kaolinite based porous geopolymer. • Optimized material exhibits a low thermal conductivity of 0.057 W/(m·K) • Compressive strength improved by 22% with addition of rock wool. • Simulations to evaluate the thermal insulation effects were compared. [ABSTRACT FROM AUTHOR]

One inconvenience presented by the thermal activation of kaolinite-based wastes is their low content of metakaolinite, a highly pozzolanic product listed in current standards for the manufacture of commercial cements. The addition of a chemical activator during the thermal activation process is a priority line of research to increase the reactivity of the recycled metakaolinite. In this paper, an additional chemical activator, ZnO, is studied and its effect on both pozzolanic properties and the evolution of mineralogical phases in the thermal activation of coal waste with a reaction time of up to 90 days in the pozzolan/lime system. To do so, activation temperatures of between 550 °C/650 °C were selected and additions of chemical activator (ZnO) in percentages of between 0.0% and 3.0% by weight of coal waste, because it is an activator with a positive effect on a 100% natural kaolinite. The results showed that the incorporation of ZnO inhibited the reactivity of the recycled metakaolinite and in consequence, the capacity of the metakaolinite to react with the surrounding lime; even more so when the content of added chemical activator was raised, albeit with some exceptions, in the samples activated at 550 °C and 650 °C with 0.5% of chemical activator. In none of the cases under analysis was the chemical activator able to improve the properties of the metakaolinite in comparison with the properties of the reference sample activated only with temperature. The hydrated phases that appeared in the pozzolanic reaction were tetracalcium aluminate hydrate, stratlingite, monosulfoaluminate hydrate and LDH (phyllosilicate/carbonate). [ABSTRACT FROM AUTHOR]

For over a century, zeolite has been synthesized and widely employed in fields such as environmental protection, petrochemical production and petroleum refining, owing to its unique structure and exceptional physical/chemical properties. In light of modern production and green chemistry, the trend is to develop green approaches for zeolite production. Natural clay, featuring abundant reserves, diverse properties and low cost, possesses the required elements and comparable structural units necessary for zeolite synthesis. As a result, natural clay holds distinct advantage as a raw material for green zeolite production. This paper introduces recent advances in the synthesis of zeolites using natural clays including kaolinite, bentonite, illite, attapulgite, and diatomite. The activations of clays and the synthesis methods of zeolites are discussed, and the future development trends for clay-based zeolite are anticipated. To advance the field, scientists must delve deeper into the synthesis mechanism and discover more energy-efficient, effective and environmentally sustainable solutions, which can be achieved through the continuous optimization of the clay activation and zeolite synthesis methods. • Natural clays are promising in eco-friendly zeolite production. • A comprehensive overview of common clays for zeolite synthesis. • Analyzing the impact of activation and synthesis methods on zeolite properties. • Identifying issues and potential future directions for clay-based zeolite synthesis. [ABSTRACT FROM AUTHOR]

The flow of water along discontinuities, such as fractures or faults, is of paramount importance in understanding the hydromechanical response of an underground geological disposal facility for radioactive waste. This paper reports four experiments conducted on kaolinite gouge on a 30° slip-plane and on realistic fractures created in Callovo-Oxfordian mudstone (COx) from France. Test histories were conducted that initially loaded the gouge material in step changes in vertical stress, followed by unloading of the sample in similar steps. This loading-unloading history showed considerable hysteresis in hydraulic flow, with only partial recovery of fracture transmissivity. This demonstrates the importance of stress history on fracture flow; consideration of just the current stress acting upon a fracture or fault may result in inaccuracies of predicted hydraulic flow. The stress dependency of fracture flow in both kaolinite and COx can be described by a power-law or cubic relationship, which is likely to be dependent on the fracture roughness, thickness of gouge material, saturation state, permeability of the host material, and clay mineralogy (i.e. swelling potential). The observed response of fracture transmissivity to normal stress in COx is a complex superposition of mechanical response of the fracture and the swelling of clay in the fracture surface. The stress-dependency of flow was also seen to be dependent on orientation with respect to bedding. A fracture perpendicular with bedding accommodates greater compression and results in a lower transmissivity. The orientation dependence is related to the anisotropic swelling characteristics of COx. [ABSTRACT FROM AUTHOR]

Differential settlements due to alkali contamination in the foundation soil and the deformations in superstructures were well documented. The influence of alkalis on clay minerals has been the subject of many studies for decades. However, studies on the role of mineral content, type of alkali and volume of the interacting solution on the dissolution of clay minerals and formation of new minerals at hydrothermal condition are scanty for a particular duration and concentration of alkali. Thus, in this paper micro level investigations were carried out to clearly understand the influence of alkalis with the varying volume of interaction on the new mineral formation along with the dissolution of the actual mineral. Two soils, namely, natural red earth and commercial kaolin with varying kaolinite content were selected for this study. The mineralogical and the morphological aspects involved in alkali treatment of these soils have been investigated using XRD, SEM, FTIR, and TG-DTA. The results showed that both red earth and kaolin treated with alkali solutions (4N NaOH and 4N KOH) at 110 °C showed the complete dissolution of mineral at higher volume of interaction. However, at given thermal condition, complete dissolution of mineral in red earth occurred at a lesser volume of interaction compared to kaolin. Furthermore, the dissolution of the original mineral and the intensity of new mineral formations varied with mineral content, volume of interacting solution and the type of alkali. Thus, the detailed analysis of the results clearly brought out that the disintegration of the actual mineral and the formation of new minerals greatly depend on the mineral content and volume of interaction [ABSTRACT FROM AUTHOR]

The synthesis and characterization of new kaolinite nanohybrid materials derived from pyridinium based ionic liquids with different functionalities located at the para position are described in this paper. Four ionic liquids (1-(2-hydroxyethyl)-4-methylpyridinium chloride (Mepyr), 1-(2-hydroxyethyl)-4-ethylpyridinium chloride (Ethpyr), 1-(2-hydroxyethyl)-4-(tert-butyl)pyridinium chloride (Tbutpyr) and 1-(2-hydroxyethyl)-4-benzylpyridinium chloride (Benzpyr)) were grafted on the aluminol interlayer surfaces of kaolinite by a melt intercalation method. The molecular structure of the grafted compounds was kept, as demonstrated by 13 C CP-MAS NMR and FTIR spectroscopies. The grafted moieties have similar orientations in the interlayer space, as evidenced by a linear relationship between the observed d-value and the size of the ionic liquids (R 2 > 0.99). This study highlights how it is possible to control, tune and functionalize the interlayer spaces of modified kaolinite. Pyridinium ionic liquids are particularly suitable for that purpose. Their substituents in the para position are the main agents of control of the rigidly fixed interlayer distance. Their choice permits also to tune the functionality of the interlayer space. Preliminary applications (adsorption of 2,4-dichlorophenoxyacetic acid(2,4-D) and electrochemical detection of thiocyanates ions) confirm the anion exchanger nature of these modified kaolinite. They confirm also that the spatial and functional controls of the interlayer environment drive the sequestration of the anions. [ABSTRACT FROM AUTHOR]

Reliability of core measurement and analysis can be highly dependent on the humidity of measurement environment. However, impact of humidity on core measurements is often assumed to be negligible. This paper quantified the influence of relative humidity on the hydration of clay minerals (i.e., montmorillonite, illite, chlorite, and kaolinite) using nuclear magnetic resonance (NMR) and thermogravimetric analysis (TGA). The influence of clay hydration on the assessment of fluid volume in organic-rich mudrocks was also investigated. The NMR T 2 (spin-spin relaxation) magnetic decay of the clay samples showed existence of water even after the samples were dried in an oven at 95 °C. The TGA measurements in clay minerals confirmed the weight loss between 95 °C and dehydroxylation temperature, which is approximately the same volume as that recorded by NMR measurement in dried samples. This recorded water volume corresponded to desorption of water molecules bound to interlayer cations (i.e., interlayer water). In the case of the hydration water, the NMR-based water vapor adsorption experiments showed that the volume of water accumulated on the surface of clay minerals increased significantly as the relative humidity increased. The cation exchange capacity (CEC) measurements of clay minerals demonstrated that the volume of hydration water was strongly related to the CEC. The volume of interlayer water was, however, not related to the CEC. In the case of organic-rich mudrocks, water vapor adsorption experiments showed > 250% change in water volume when relative humidity varies in the range of 0% to 95%, which further verified the significant impact of humidity on core measurements and the necessity of applying corrections for such an impact. [ABSTRACT FROM AUTHOR]

This paper deals with the effects of lime addition on clay materials properties, in terms of mechanical and physico-chemical evolution. A coupling between these two aspects was undertaken in order to explain the mechanical behaviors of lime-treated clay materials. The study was performed on two different clays, a kaolin and a Ca 2 + -bentonite. Lime addition leads to an increase of mechanical properties of these clays. These improvements are faster with Ca 2 + -bentonite, even if at long term the performance reached for kaolinite is higher. The coupling between macroscopic and physico-chemical aspects shows that these improvements are linked to the development of secondary compounds such as calcium silicate hydrates, hydrogarnet and calcium carboaluminate hydrate phases. [ABSTRACT FROM AUTHOR]

This paper evaluates the potential of water treatment sludge ash (WTSA) as high-reactivity pozzolan using strength tests in mortars and techniques to evaluate the calcium hydroxide consumption in pastes with hydrated lime. The sample was dried in an oven and then calcined at 600, 700, and 800 °C in a muffle. A high-reactivity metakaolin sample was used as a pozzolan reference. The properties of the samples assessed were fineness (Blaine), density (Le Chatelier), and chemical and mineralogical composition using X-ray diffraction (XRD), X-ray fluorescence (XRF), and thermogravimetric analysis (TG). The assessment of the pozzolanic properties employed standardized tests such as compression tests with hydrated lime (NBR 5751) and Portland cement (NBR 5752) in mortars. Also, non-standardized techniques, such as XRD, TG, and electrical conductivity, were utilized to evaluate the consumption of calcium hydroxide in pastes and solutions with hydrated lime and pozzolan. The standardized tests showed that mortars with metakaolin (MK) presented higher compressive strength values, while mortars with ash calcined at 600 °C (SA600) obtained the lowest values among WTSA. This behavior occurred because the preparation of mortars was strongly influenced by their consistency, affecting the compressive strength. However, analyzing the consumption of calcium hydroxide in pozzolan-hydrated lime pastes, SA600 presented higher values. Unlike tests on mortars, consistency is not affected in preparing the pastes, allowing a better development of pozzolanic reactions. Based on Ca(OH) 2 consumption, it was concluded that the samples of WTSA studied could be used as high-reactivity pozzolans. • The kaolinite content in raw WTS measured by Rietveld refinement was 66.4% • Temperature calcination range from 600 to 800 °C is suitable to obtain high-reactivity pozzolan from water treatment sludge. • WTSA samples presented higher calcium hydroxide consumption than metakaolin. • Calcium aluminosilicate hydrates were produced from the reaction of WTSA and calcium hydroxide. [ABSTRACT FROM AUTHOR]

Kaolinite is a typical silicate impurity in microcrystalline graphite ore. Removal of kaolinite from graphite ores is important to achieve high purity graphite product. Alkali-acid leaching is effective to remove silicate impurity in microcrystalline graphite. For in-depth understanding of phase transformation of kaolinite in microcrystalline graphite purification process, dissolution behavior and mechanism in alkali-acid leaching process were studied in this paper. As shown in alkali-acid leaching tests and analyses (FTIR, XRD, and SEM-EDS), silicon extraction of kaolinite was mainly affected by sodium hydroxide concentration, alkali-leaching temperature, and alkali-leaching time. The dissolution mechanism of kaolinite was regarded as a three-stage process: kaolinite firstly dissolved in alkaline solution in form of soluble silicate and aluminate. Dissolved silicate and aluminate in alkaline solution then reacted with each other and aluminosilicate transient phase with Si/Al ≈ 1 precipitated when silicon ion concentration exceeded its equilibrium concentration. Finally, the aluminosilicate precipitate composed of nepheline and sodalite dissolved in hydrochloric acid solution. As a consequence, kaolinite dissolved completely in alkali-acid leaching process. [ABSTRACT FROM AUTHOR]

The aim of this paper is the characterization of pure tobelite synthesized in the system (NH 4 ) 2 O-Al 2 O 3 -SiO 2 -H 2 O, which is a first, indispensable step for accurately interpreting the data obtained in more complex chemical systems. Tobelite has been synthesized at hydrothermal conditions (200 ± 3 °C), using a solid:solution ratio (in weight) = 1:15, and reaction times from 1 to 90 days and has been characterized by X-ray diffraction; infrared and Raman spectroscopy; differential thermal analysis and thermogravimetry; and transmission-analytical electron microscopy. The average chemical composition of tobelite formed after 90 days run time, determined by combining the analytical electron microscopy data with nitrogen determination in the solid products of the reaction by elemental analysis, was [NH 4 Al 1.98 (Si 3.07 Al 0.93 )O 10 (OH) 2 ]. The refinement of the X-ray diffraction patterns indicated that the 1 M polytype predominates, and the determined cell-parameters were: a = 5.219 (0.004) Å; b = 9.021 (0.007) Å; c = 10.556 (0.009) Å; β = 101.41° (0.08); V = 487.23 (0.69) Å 3 . The infrared spectra indicated the presence of two υ 4 bands (at 1403 and 1435 cm − 1 ), which can be related to the presence of two main tobelite populations with mean particle sizes of 400 × 60 and 2000 × 200 Å. The thermal study by means of differential thermal analysis and thermogravimetry, combined with X-ray thermodiffraction suggested that the mechanisms of NH 4 loss were different in the two differently-sized tobelite populations: the thinner particles showed a low thermal stability (between 380° and 440 °C) and the NH 4 loss was coupled with dehydroxylation, leading directly to the decrease of the tobelite content. Loss of NH 4 from the thicker particles occurred between 440° and 500 °C, causing a gradual contraction of the basal spacing, which was followed by dehydroxylation. There were no previous data of Raman spectroscopy of tobelite and this study presents its most characteristic features. [ABSTRACT FROM AUTHOR]

Kaolinite layers get curled up into one-dimensional nanoscrolls automatically when they are exfoliated in methanol after intercalation with alkyltrimethylammonium salts. The intercalated molecules weaken the hydrogen bonding significantly, and provide space for kaolinite to roll up after their deintercalation. A mismatch of Si O tetrahedral sheet and Al O(OH) octahedral sheet of kaolinite leads to rolling up of the layer until reaching a stable morphology. During the intercalation and exfoliation processes, the kaolinite layer goes through a morphological evolution sequence i.e., from 3-dimensional particles to 2-dimensional lamella and then to 1-dimensional scroll (3D → 2D → 1D). The inner diameter of kaolinite nanoscroll varies between 10–35 nm, while the outer diameter is about 35 nm but most of them are smaller than 100 nm. The length of kaolinite nanoscroll is determined by the initial particle size. This paper presents a systematic analysis of morphological changes of kaolinite minerals and proposes the concept of self-adaptive deformation of minerals. [ABSTRACT FROM AUTHOR]

The sludge generated in the treatment of surface water for human consumption represents an environmental hazard which can be mitigated by the valorisation of this solid waste. This paper presents an analysis of the process parameters and physicochemical mechanisms involved in the elaboration of a glass-ceramic foam using clay and the sludge generated in a drinking water plant. Optimisation of the process conditions was performed by a 3 3 experimental design. For structural purposes, compression strength is the optimising parameter; if used as a catalytic support or filtering medium, porosity and permeability have to be maximised. An open cellular structure can be obtained when the materials are fired in a mould which allows the coexistence of solid, liquid and gas phases. The latter are responsible for foaming and were identified as CO 2 , SO 2 and H 2 O. Thermogravimetric analysis coupled to mass spectrometry and Mössbauer spectroscopy show that CO 2 was generated mainly from pyrolysis, SO 2 was generated from aluminium sulphate used as a coagulant in the drinking water treatment but H 2 O resulting from the decomposition of lepidocrocite at high temperature is likely to be the main agent for the foaming effect. [ABSTRACT FROM AUTHOR]

Per - and polyfluoroalkyl substances (PFAS) have been detected in ecosystems globally and pose a serious threat to human health. Clay minerals are promising adsorbents for PFAS removal from contaminated water, thus it is crucial to understand the interactions between PFAS and clay minerals. This paper performed molecular dynamics simulations to reveal the complex behaviors and fundamental mechanisms of the adsorption of perfluoroalkyl sulfonic acids (PFSA) on the siloxane and hydroxyl external basal surfaces of kaolinite. The results demonstrate that adsorption is favorable on both the surfaces; however, their mechanisms are distinct. On the hydroxyl surface, PFSA anions exhibit a steady "point adsorption" mode, with the diffusion coefficients considerably lower than those in bulk aqueous solution. The terminal sulfonate groups form hydrogen bonds with the surface hydrogen atoms like a "three-pin plug", with a matching molecular geometry. The molecular force and molecular electrostatic potential analyses suggest that the Coulomb electrostatic attraction force from kaolinite to the terminal sulfonate groups of PFAS anions is the predominant driving force of adsorption for the hydroxyl surface. The potential of mean force (PMF) calculations show that the PFSA anions have to go over an energy barrier, which is induced by hydration of the hydroxyl surface, to reach the stable adsorption position. On the siloxane surface, PFSA anions exhibit a mobile "surface adsorption" mode, with a relatively high freedom along the plane parallel to the surface. The diffusion coefficients of the PFSA anions adsorbed on the siloxane surface are slightly lower than those in bulk aqueous solution. The non-polar CF chains lie flat above the siloxane surface due to the hydrophobic interaction, while the terminal sulfonate groups stay relatively far away from the siloxane surface. A greater van der Waals repulsive force from the outer water molecules to the CF chains is the predominant driving force of adsorption, and pushes PFSA anions to the siloxane surface as PFSA anions approach kaolinite. The minimum values of the PMF of adsorbed PFSA anions on the siloxane surface are lower than those on the hydroxyl surface, indicating that adsorption stability is higher for the siloxane surface. [Display omitted] • PFSA exhibits a point adsorption mode on kaolinite hydroxyl surface via electrostatic attraction. • PFSA exhibits a surface adsorption mode on kaolinite siloxane surface via hydrophobic interaction. • Adsorption stability of PFSA on kaolinite siloxane surface is higher than on hydroxyl surface. • Diffusion coefficient of the adsorbed PFSA on kaolinite is lower than in bulk aqueous solution. • Van der Waals repulsive force from outer water pushes PFSA towards kaolinite siloxane surface. [ABSTRACT FROM AUTHOR]

The defected kaolinite is common in sedimentary kaolin, but its structure and disorder mechanism remains unclear. In this paper, three different size distributions of kaolinite particles: 0–300 nm, 200–1000 nm, and 500–2000 nm, were separated and classified from high-defect sedimentary kaolin, collected from Quaternary sedimentary kaolin in Guangxi Zhuang Autonomous Region of China. The three particle sizes of kaolinite have been monitored by particle size analyzer, high-resolution magic-angle spinning NMR (MAS NMR), small and wide-angle X-ray scattering (SAXS and WAXS), X-ray diffraction (XRD), BET surface analyzer, nitrogen gas-adsorption, scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). The results revealed that the smallest particle size of kaolinite exhibited high degrees of broken Al-O-Al and Si-O-Si bonds, more disordered structure, and elevated specific surface area. The degree of the structural disorder of kaolinite increases as the particle size decreases, which can be attributed to the more aluminum substituted for silicon in tetrahedron sheet in the finer kaolinite crystal, compared to the coarser kaolinite crystals. • Kaolinite particles were separated into three parts, <300 nm, 200–1000 nm, and 500–2000 nm. • The degree of the disorder increases as the kaolinite particle size decreases. • The smallest particle size of kaolinite showed high degrees of broken Al-O-Al and Si-O-Si bonds. [ABSTRACT FROM AUTHOR]

The aim of this paper is to investigate the effects of co-calcining kaolinite and montmorillonite clay blends with alkali and alkali earth metal (AAEM) hydroxides as a route to enhance the reactivity of the clay blends. NaOH, KOH, and Mg(OH) 2 were added in different dosages (0–20%) to the clay blend and calcined together at 750 °C. When NaOH and KOH added at a dosage <10%, this co-calcination promoted amorphization, increased non-bridging oxygen per tetrahedron (NBO/T), increased dissolution of Si, and therefore improved reactivity. At a higher dosage, these additives decreased reactivities. These clay blends were utilized as a precursor in a seawater-cured lime-pozzolana binder system. The evolution of the microstructures was monitored using XRD, FTIR, 29Si solid-state NMR, 27Al solid-state NMR, ICP-OES, and SEM-EDS for up to 90 days. The maximum compressive strength came from the 5% Mg(OH) 2 batch which was 22.1 MPa at 90 days. The 5% dosages of all the AAEM hydroxides showed better performance than that of the control batch. The mineralogy showed the presence of hydrocalumite, ettringite, gehlenite, hydrogarnet, and calcium aluminum silicate hydrate (C-A-S-H) in seawater cured paste samples. The SEM-EDS revealed the presence of plate and needle like C-A-S-H in the seawater cured samples. • Co-calcination with NaOH & KOH at 5% dosage increased the amorphous content. • Co-calcination with NaOH & KOH reduced polymerization of the aluminosilicate. • Co-calcination with Mg(OH) 2 did not alter the aluminosilicate network. • Co-calcination with NaOH & KOH changed Al coordinate in aluminosilicate network. • The maximum compressive strength was from the 5% Mg(OH) 2 sample. [ABSTRACT FROM AUTHOR]

Sources of raw materials and identification of the provenance of ancient ceramics as well as the estimation of the firing temperatures of ceramic findings are two principal problems archaeologists solve with material scientists. These two problems are closely interconnected. This paper is focused on the identification of clay mineral kaolinite in a ceramic body of archaeological ceramic idol in comparison with a reference kaolinitic raw material. Kaolinite identified in studied ceramic samples can be from a primary source or a product of rehydroxylation of metakaolinite of the ceramics. The rehydroxylation process is simulated here in laboratory conditions in an autoclave by modifications of standardized test methods. The rehydroxylation process was studied on a kaolinitic raw material and the acquired results were then applied to evaluate samples of a unique archaeological object from the Late Bronze Age — a moon-shaped ceramic idol, which was found at an archaeological site near Prague in the Czech Republic. XRF, XRD, TG-DTA, TG-DSC and IR analyses were used to study this process. XRD and TA proved the presence of the clay mineral kaolinite in its end parts. A small amount of kaolinite was also detected in the central part, but only by TA. It was proved that kaolinite in the end parts originated from raw material and that its presence in the central part was caused by the rehydroxylation of the metakaolinite. It was probably due to the use of the moon-shaped ceramic idol as an andiron in an open fireplace. [ABSTRACT FROM AUTHOR]

The aim of this paper is to demonstrate that morphological particle properties inside the polymer matrix are responsible for the variability of mechanical properties (elasticity, strength, resilience) and fire retardancy properties. Ultrafine kaolinites were modified and employed to obtain composites of polyamide. These composites were characterized by means of mechanical (tensile static and dynamic tests) and fire retardancy properties (cone calorimeter). Their morphological properties differed significantly according to the aspect ratio and surface treatment of the kaolinites. These morphologies, characterized by the particle dispersion (interparticle distance ID) and size distribution (median diameter MD) in the polymer matrix, were directly related to the mechanical properties. The experimental results demonstrate the sensitivity of strength, resilience and flammability to particle dispersion and distribution. The yield stress decreases with the increase of MD, the resilience decreases with the increase of ID with a critical ID value from which the composite became brittle, and the pHRR increases with the increase of ID. [ABSTRACT FROM AUTHOR]

To understand the morphological changes of three commercial kaolins during flash calcination and to compare them with those obtained during traditional heat treatments in the laboratory (an electric furnace at 700 °C for 5 h), this paper presents the physical and chemical characteristics of metakaolins obtained from an industrial flash calciner. In the metakaolin products, kaolinite was not completed dehydroxylated during calcination, and the proportion of untransformed kaolinite was greater in flashed metakaolins than in traditional rotary-calcined metakaolins. Several particle morphologies were discernible in the metakaolins, including spherical particles that were formed in flash calcinations. These spherical particles were cut with a focused ion beam (FIB) and were revealed to contain a vitrified aluminum silicate phase with traces of mullite and various gases. These spherical particles were produced from the direct calcination of several submicron kaolinites near the flame of the calciner. [ABSTRACT FROM AUTHOR]

This paper discusses the formation of cetylpyridinium bromide (CPB), a cationic surfactant quaternary ammonium compound (QAC), immobilized on kaolinite with different initial CPB concentrations ([CPB] i ) and their effect on the antibacterial activity against Escherichia coli . The CPB-immobilized kaolinites were characterized by a CHNS analyzer, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), zeta potential (ZP) analysis and the amount of CPB adsorbed on kaolinite. The antibacterial assay of the samples was studied through the disk diffusion technique (DDT) against E. coli as a model bacterium. The amount of CPB adsorbed on kaolinite did not affect the structure of the parent kaolinite but affected the overall charge of the kaolinite and eventually affected their antibacterial activity. CPB-immobilized kaolinite with [CPB] i above the critical micelle concentration (CMC) possessed antibacterial activity because of reversal of the charge from negative to positive on the kaolinite surfaces, as proven by ZP analysis, which could allow the action of CPB molecules against bacteria cells. This was due to the bilayer formation of surfactant molecules via hydrophobic bonding of their long hydrocarbon chains on the kaolinite surfaces at surfactant concentrations above the CMC value. Therefore, one of the important factors in producing antibacterial agents from surfactant immobilized kaolinite (organo-clay) is by loading excess surfactant on the clay above its CMC level to ensure bilayer formation of surfactant molecules on clay surfaces. [ABSTRACT FROM AUTHOR]

The influence of thermal activation temperature in the pozzolanic reactivity of low grade kaolinitic clay and the impact of calcination products in OPC hydration are assessed in this paper. The raw material, with approximately 40% kaolinite and 40% of 2:1 clay minerals, was calcined to temperatures ranging between 500 and 1000 °C. The clay and its calcined products were characterized by XRD, XRF, FTIR, TGA–DTA, 27 Al NMR, PSD and BET. The pozzolanic reactivity of the calcined products and its impact on hydration of blended systems was assessed by compressive strength in mortars with 30% substitution of OPC and heat output from lime–pozzolan pastes. The influence of calcined clays on OPC hydration was characterized by XRD, 27 Al NMR and 29 Si NMR, and Isothermal Calorimetry. The increase of pozzolanic reactivity with the increase of activation temperature is limited not only by recrystallization above 900 °C, but also by the decrease of the specific surface that occurs between 800 and 900 °C. Highest pozzolanic reactivity is reached when calcined at 800 °C, a temperature representing the best compromise between structural disorder of the clay fraction and its specific surface. The impact of calcined clays on the hydration of blended systems is a combination of a filler effect at early ages and the pozzolanic reaction. Calcined clays favor the formation of AFm-type phases and C–A–S–H with longer chains, in which Al is substituting for Si. The experimental results indicate that clays with moderate contents of kaolinite constitute a potential source of high reactivity pozzolanic materials. [ABSTRACT FROM AUTHOR]

This paper reported a new method to enhance adsorption performance of La(III) and Y(III) on kaolinite by enlarging the interlayer space of kaolinite. The intercalation method could enlarge the interlayer space of kaolinite effectively in previous research literatures, whereas there were few studies on utilizing further reaction of intercalators to expand and exfoliate kaolinite by generating gas. The expanded kaolinite (EKH) involved in this study could enhance adsorption performance of La(III) and Y(III) significantly. The EKH in a state between extended and exfoliated was obtained undergoing two steps. Firstly, H 2 C 2 O 4 was inserted into the kaolinite layers through the secondary substitution liquid phase intercalation method. Secondly, the Kaol-H 2 C 2 O 4 (KH) intercalation complex was rapidly calcined with H 2 C 2 O 4 and Na 2 CO 3 , the power provided by the neutralization reaction promoted the thermal decomposition of H 2 C 2 O 4 between the kaolinite layers to produce a large amount of gas. XRD showed that the interlayer space of the KH intercalation complex expanded from 0.717 nm to 1.112 nm. The specific surface area and total pore volume of the EKH were 1.5 and 2.2 times higher than unmodified kaolinite respectively. The surface of EKH possessed higher zeta potential with more negative charges. The results of batch adsorption experiments showed that the adsorption capacity (101.5 mg/g and 78.9 mg/g) of EKH to La(III) and Y(III) was much higher than that of kaolinite (17.1 mg/g and 9.8 mg/g). Pseudo-second-order model and Langmuir model manifest the adsorption kinetics and isotherm. Therefore, the EKH prepared by the intercalation expansion method could be prospectively applied to the treatment of La(III) and Y(III) in industrial wastewater. [Display omitted] • Expanded kaolinite is obtained by intercalation-expansion method. • H 2 C 2 O 4 was inserted into the kaolinite layers and generated gas to expand kaolinite. • The adsorption performance of La(III) and Y(III) on EKH were up to 101.5 mg/g and 78.9 mg/g. • Pseudo-second-order kinetics and Langmuir model could manifest the adsorption kinetics and isotherm. [ABSTRACT FROM AUTHOR]

Granite residual soil (GRS) contains a large amount of kaolinite, which is highly hydrophilic and thus easily disintegrated by water. These characteristics may cause severe landslides and debris flows in some hillslopes composed of GRS. This paper describes an investigation of possible solutions to this problem: the addition of fiber and/or alkaline solutions to GRS to reinforce GRS. The effects of the silica-to‑sodium oxide (SiO 2 -to-Na 2 O) molar ratios of alkaline solutions on the static mechanical properties of reinforced GRS and the effects of fiber type on the impact resistance of reinforced GRS are discussed. The reinforcement mechanism, characterized by a combination of techniques, namely X-ray powder diffraction, Fourier-transform infrared spectroscopy, microcomputed tomography, and scanning electron microscopy, is also discussed. Static load test results indicated that the alkaline solution–reinforced GRS with a SiO 2 -to-Na 2 O molar ratio of 0.5 exhibited the highest compressive strength (4550 kPa), which is attributable to this reinforced GRS having the lowest porosity (2.3%). The alkaline solution reacted with GRS to form cementitious materials, thereby improving the compressive strength of GRS. Drop weight impact testing showed that fiber-reinforced GRS had dynamic mechanical properties superior to those of pristine GRS, and that in combination with a given alkaline solution, glass fibers reinforced GRS more effectively than basalt fibers. This is because the silicon atoms on the surface of glass fibers participated in the reaction with the alkaline solution, thus forming more cementitious materials. These materials were evenly distributed on the surface of the glass fibers, and thus particles of glass fiber–reinforced GRS were more closely bound to each other than particles of basalt fiber–reinforced GRS particles. These findings suggest that waste GRS, once appropriately reinforced, could be used for the construction of high-strength foundations and embankments. • Alkaline solution and fiber are used to reinforce granite residue soil (GRS). • Solution with a SiO 2 /Na 2 O ratio of 0.5 shows best effect on static mechanical property. • Glass fiber shows better effect on dynamic mechanical property than basalt fiber. • The consumption of kaolinite and formation of gels favor the improved properties. [ABSTRACT FROM AUTHOR]

Calcination of kaolinite particles under appropriate conditions to produce materials that can replace part of the CO 2 intensive clinker is gaining an increasing interest in cement industry worldwide. This paper presents a study of flash calcination of kaolinite rich clay particles in a pilot scale gas suspension calciner, with the aim to derive useful guidelines on smart calcination for obtaining products of the best pozzolanic properties. Calcination tests are performed in the calciner under six different operation conditions. The raw feed and the calcined clay samples are all characterized experimentally and a mathematical model is also developed to predict the conversion of the clay particles. The model properly accounts for the particle–ambient flow interaction and numerically solves all the processes occurring within the clay particles. The model predictions are compared against the experimental results. A good agreement is achieved. Finally, a model-based sensitivity analysis is conducted. [ABSTRACT FROM AUTHOR]

A preparation strategy for constructing Pd-deposited ZnO/kaolinite was described in detail in this paper. Natural rod-like kaolinite served as a support to disperse ZnO nanoparticles through a thermal treatment. The ZnO nanoparticles were assembled on the surface of kaolinite rods to produce ZnO/kaolinite nanocomposites, which were then employed as a supporting material for the dispersion of Pd nanoparticles. The samples were characterized by XRD, FTIR, TEM, XPS, UV–vis spectroscopy, and photocatalytic property measurements. The results indicated that an obvious chemical binding existed between ZnO nanoparticles and the kaolinite surface. The shift of the binding energy of metallic Pd demonstrated a strong interaction between the metallic Pd and ZnO nanocrystals. The as-synthesized Pd–ZnO/kaolinite exhibited superior photocatalytic activity for the photodegradation of methylene blue compared with Pd/ZnO, ZnO/kaolinite, and pure ZnO, which indicated that the hybridization of the metal, kaolinite rods, and semiconductor could provide enhanced photocatalytic activity through a synergistic effect. [ABSTRACT FROM AUTHOR]

Many types of zeolites have been developed based on kaolinite in previous years. This review focuses on the current reports of kaolinite-based zeolites and the important factors in their synthesis. Among the factors discussed in this review are the effect of SiO2/Al2O3 (Si/Al) molar ratio of the gel mixture, metakaolinization time and temperature, aging condition, alkalinity, and crystallization time and temperature. This review only covers the most recent kaolinite-based zeolite papers published from 2005 to present. A brief discussion on the evolution of zeolites is also included. [ABSTRACT FROM AUTHOR]

The shuttling effect of polysulfide ions is an important reason that hinders the commercial application of lithium‑sulfur batteries. The natural clay mineral halloysite has good adsorption performance and hollow tubular structure, which can absorb and accommodate enough sulfur, while the flake kaolinite can roll to form a halloysite-like structure. The effect of acid-modified halloysite and kaolinite nanoscrolls as sulfur carriers on the performance of lithium‑sulfur batteries was studied in this paper. As a result, both acid-modified halloysite and kaolinite nanoscrolls could effectively adsorb polysulfide ions, while kaolinite nanoscrolls were more conducive to the migration and diffusion of Li+ due to its thinner wall (about 5 nm), thus exhibiting faster reaction kinetics and higher sulfur utilization, and had better rate performance and cycle stability. The application of clay minerals in the field of energy has always been unpromising. This research work makes full use of the characteristics of clay minerals and broadens its application, providing a basis for the design of clay minerals and a possible modification direction for their application in lithium‑sulfur batteries. Compared with the thin-walled halloysite nanotubes by acid treatment, the kaolinite nanoscrolls present high capacity and cycle stability, which is attributed to the thinner tubewall accelerating the migration of lithium ions. [Display omitted] • Kaolinite nanoscroll with larger inner lumen is suitable for loading sulfur. • Kaolinite nanoscroll sulfur cathode has good rate performance and cycling stability. • Thinner tube walls effectively enhance the Li+ diffusion coefficient in battery. • Hollow tubular structure and silicate component synergistically inhibit shuttle effect. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the present paper is to investigate the adsorption of uranyl species (UO2)2+(H2O)5 onto kaolinite (001) surfaces. To this end we have employed molecular dynamic simulations based on CLAYFF force field potential. Various types of surface model for inner-sphere adsorption complexes and one model for outer-sphere adsorption complexes were optimized. In order to have a neutral structure, the uranyl (UO2)2+(H2O)5 or the kaolinite was deprotonated to form the outer-sphere or inner-sphere adsorption complexes. Both singly protonated and partially deprotonated states of the Al(0) kaolinite surface were considered for adsorption in the model of inner-sphere complexes. The first uranyl coordination shell exhibits pentagonal bi-pyramidal symmetry with the pentagonal formed by 5 water molecules. We show that the average U–OW distances are between 2.49 and 2.57Å for water molecules. The bond of uranyl with deprotonated O− center is always short because of the charge attraction. The obtained results agree well with density functional calculations and EXAFS measurements, and show how and why the adsorption of uranyl appears on the surface of kaolinite. [Copyright &y& Elsevier]

Abstract: This paper reports on designed non-fired clay mixes for sustainability and low carbon use. Ground Granulated Blastfurnace Slag (GGBS), an industrial by-product, was used as a partial substitute for conventional stabiliser (Lime or Portland cement) to stabilise Kaolinite Clay (KC) and Lower Oxford Clay (LOC), for sustainable and low carbon non-fired clay building material production. Although GGBS has been used extensively in concretes to reduce the carbon footprint, there is an unexplored potential for its use as a cement replacement for stabilised soil production. The benefits of using GGBS in non-fired clay building material development include lower emissions of greenhouse gases and improved durability. The parameters considered under this study are: (1) material characterisation, (2) unconfined compressive and (3) durability. For the assessment of durability, a MX 2000VJ Tech multi-channel data logger equipped with a digital displacement transducer and computer device was employed to monitor the linear expansion behaviour of the stabilised test specimens. The 90-day unconfined compressive results for the test specimens showed that there is significant strength gain (up to 5N/mm2) for all the stabilised mixtures. The lime-activated GGBS stabiliser has significantly higher influence in the strength gain compared to the equivalent PC-based system. These results suggest that there is potential in using Lime or Portland cement activated GGBS blend for the stabilisation of natural clay soil for sustainable and low carbon building materials production. [Copyright &y& Elsevier]

Abstract: In this paper, we reported the synthesis of composite conductive powders of antimony-doped tin oxide (Sb–SnO2) coated onto kaolinite. Structure and morphology of the samples were systematically characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transform infrared (FTIR) and X-ray photoelectron spectrum (XPS). The results showed that Sb–SnO2 nanoparticles (<10nm) were successfully coated as thin layers on the surface of kaolinite. The antimony-doped tin oxide/kaolinite (ATK) composites retained the flake morphology like the original kaolinite and had a resistivity of 273.2Ω·cm. Sb–SnO2 layers were proved to attach to the kaolinite surface via the Sn–O–Si or Sn–O–Al bonds. The growth mode of Sb–SnO2 layers onto the kaolinite was investigated. [Copyright &y& Elsevier]

Abstract: This paper presents an immersion method for preparing the kaolinite–potassium acetate intercalation complexes. The effectiveness of intercalation and influencing factors were analysed and evaluated. The results show that the intercalation of kaolinite by potassium acetate is strongly related to crystallinity of kaolinite, concentration of intercalating agent solution, aging time and pH. The well-crystallized kaolinite is conducive to intercalation by potassium acetate. A higher concentration of intercalating agent (≥30%) can complete the intercalation in a short time (<12h), but at lower concentrations intercalation took significantly longer (≥144h). The weak alkaline condition of pH=10 proved to be the most suitable environment for the formation of intercalation complex. A good intercalated complex can be obtained at room temperature. [ABSTRACT FROM AUTHOR]

Abstract: Addition of pozzolans to blended cements is well known to have a positive effect due to the pozzolanic reaction. For some pozzolanic materials such as clays, the activation temperature plays an important role in the mineralogy and in the pozzolanic reaction. This paper reports the influence of the activation conditions (700 to 800°C for 2 or 5h in a furnace) of a clay waste on the mineralogy of a 20% blended cement matrix at 28days of normalised curing. The mineralogical composition changes were analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) — energy dispersive X-ray spectroscopy (EDX). The presence of an unstable LDH-like compounds (without magnesium) and the presence of tetracalcium aluminate hydrate (C4AH13) and calcium hydroxide, and the persistence of alite (Portland cement compound), was identified. [ABSTRACT FROM AUTHOR]