Applied Clay Science最新文献

Limestone calcined clay cement (LC³) is an emerging ternary binder, while typically only kaolinitic clays have been used or investigated for its production. There is a dire need to scientifically investigate the potential utilization of low-grade kaolinitic and mixed clays. In this study, nineteen different natural clays were examined from various locations in Pakistan, with a focus on clay quarries near cement plants. From the dataset, seven significant criteria were identified: mineral type, and the contents of kaolinite, SiO₂, Al₂O₃, Fe₂O₃, CaO, and the Al₂O₃/SiO₂ mass ratio. Nineteen clays were characterized using X-ray diffraction, X-ray fluorescence, and thermogravimetric analysis. These clays were then prioritized against the identified criteria using multi-criteria decision-making analysis. After characterizing them, the top ten clays were calcined to evaluate the performance of LC³. A correlation analysis was conducted between the characterization of calcined clays and the compressive strength of LC³. It was revealed that all criteria were positively correlated with compressive strength, except for Fe₂O₃ and CaO, which showed a negative correlation. The correlation coefficients for Fe₂O₃ and CaO were − 0.44 and − 0.47, respectively. According to the OPC Type I, incorporating low-grade kaolinite with a composition of 40–55% leads to greater compressive strength gain compared to the standard 42.5 MPa compressive strength of OPC Type I. Even clays with lower grades, ranging from 38 to 41 MPa, can achieve up to 96.5% of the compressive strength of OPC Type I. Therefore, low-grade clays could be incorporated into a ternary binder system to produce carbon-neutral cement.

Natural gas hydrates are predominantly buried in clay sediments in natural environments, where are some edge surfaces of clay particles directly contacting the hydrates. However, the exact nature of the interaction between these surfaces and the hydrates, as well as their influence on hydrate formation, remains elusive. Herein, microsecond molecular dynamics simulations have been performed to investigate CH₄ hydrates formation in nanopores consisting of clay edge surfaces, to reveal the effects of clay edge surfaces and layer charges. The simulation results show that the clay edge surfaces affect CH₄ hydrate formation by changing the distribution of water and CH₄ molecules via surface adsorption, mainly ascribed to the different polarities of the groups on the edge surfaces of different clays. The greater the electronegativity of the clay, the stronger the inhibition of CH₄ hydrate formation, thus, the electroneutral clays are more beneficial for CH₄ hydrate formation than the electronegative clays. Moreover, in the early stage of the simulation, compared with the electronegative clays, the electroneutral clays are more favorable for the diffusion of CH₄ molecules from the nanopores into the bulk solution and then promote CH₄ hydrate formation. On the other hand, the ions in the solution gradually aggregate together and their distribution becomes denser and more ordered. The edge surfaces of electroneutral clay are more accessible to hydrate solids than electronegative clay. These molecular insights into the formation behavior of CH₄ hydrates in clay nanopores consisting of edge surfaces help to understand the formation process of natural gas hydrates in marine sediments.

Nanofiltration is a promising technology for the treatment of industrial effluents containing organic contaminants and large divalent ions. The development of green nanomembranes is hence crucial for advancing this technology. This work aims to synthesize a novel chitosan-montmorillonite (CTS-MMT) nanomembrane concerning pH effects and to evaluate its structural stability under a wide range of operating temperatures in aqueous solution. Molecular dynamics method is conducted here and the INTERFACE-PCFF force field was employed in the biopolymer-organic system. Results show that water and counterions play a hindering role in the coating process. The higher protonation rate of chitosan can achieve higher adhesiveness and a more uniform distribution on the MMT surface after complete drying. This behaviour is due to the CTS-MMT interaction, mainly generated by -NH₃⁺ via electrostatic and hydrogen bonding interactions, while OH and NH₂ groups exhibit negligible contributions. Both water-induced peeling as well as temperature-dependent peeling were analyzed basically according to the adhesion rate of NH₃⁺ groups. Water evaporation is observed at around 550 K and no decisive desorption of chitosan from the clay substrate can be found even at extremely high temperatures up to 800 K. The high thermal stability of the CTS-modified organoclay nanomembrane in water proves that they will not generate secondary pollutants. This study can therefore provide insight into the fabrication and design of the proposed new type of membrane within clay nanocomposites.

Characterization of 10 potassium trioctahedral micas alongside pot cultivation of paddy rice was conducted here to elucidate the influence of F content on the plant availability of non-exchangeable K in the interlayers of these micas. Additionally, their effectiveness as soil amendments in reducing radiocesium uptake by paddy rice was investigated. Chemical analysis confirmed that all micas were potassium trioctahedral type, whilst F content varied between 0.09 and 1.24 per half-unit cell. The application of potassium trioctahedral micas did not increase soil exchangeable K before planting; however, exchangeable K after harvest was higher in mica-amended pots than in control pots, except for two micas. This indicated the release of non-exchangeable K during the growing season of paddy rice. Furthermore, the soil K status during the later growth stage was reflected by higher K uptake by rice shoots and lower radiocesium transfer to brown rice compared with the control, thus suggesting the effectiveness of phlogopite and biotite as soil amendments for increasing K uptake by paddy rice, whilst reducing radiocesium uptake. The strong positive correlation of tetraphenylborate-extractable K with soil K status during the late growth stage with K uptake by rice shoots suggested that the plant availability of non-exchangeable K in potassium trioctahedral mica amendments could be evaluated through tetraphenylborate extraction. An increase in the F content of Fe-poor potassium trioctahedral micas resulted in decreased soil K status during the late growing season, alongside decreased K uptake by shoots and increased radiocesium transfer to brown rice. However, the negative influence of F on the plant availability of non-exchangeable K appeared to be less significant in Fe-rich potassium trioctahedral micas than in Fe-poor ones.

In this study, chemically bound phosphate ceramics (CBPCs), a type of geopolymer, were synthesized by reacting metakaolin (MK) with acidic solutions of phosphoric acid (PA), potassium dihydrogen phosphate (KDP), calcium dihydrogen phosphate (CDP), and aluminum dihydrogen phosphate (ADP). The obtained CBPCs were characterized using thermal analysis (DTA-TG), X-ray diffraction, dilatometry, and scanning electron microscopy and by their real density, porosity, water absorption, and compressive strength. The analyses revealed that the used acid phosphate type strongly influenced the properties of the resulting CBPCs. The best compressive strength results were found in CBPCs obtained using ADP, with an average value of 34.50 MPa and average porosity of 23.21%. For CBPCs obtained from PA, CDP, and KDP, the average compressive strength values were 14.18, 8.17, and 2.84 MPa, respectively; their average porosities were 18.79%, 36.23%, and 37.90%, respectively. The results demonstrate that CBPCs produced with MK can be cured at room temperature and that CBPCs obtained with ADP have higher compressive strength values than these of the other acids.

This research examines fired clay bricks made with waste pomace from the wine industry as an additive in brick production. To this end, we analyse and discuss the chemical, mineralogical, textural and physical-mechanical behaviour of fired bricks made with three concentrations of wine pomace (2.5, 5 and 10 wt%) and at three different firing temperatures (800, 950 and 1100 °C) and evaluate their durability to salt crystallization. Variations in colour were also examined. The firing process resulted in the decomposition of phyllosilicates and carbonates, the crystallization of Fe oxides and the appearance of high-temperature Ca- (and Mg-) silicates phases such as gehlenite, wollastonite, anorthite and diopside. The bricks made with added wine pomace had very similar mineralogy to the control samples made without it. The bricks made with added wine pomace were lighter than the control samples and underwent less linear shrinkage during the drying process. Particles in the wine pomace were consumed during firing, leading to the appearance of voids. The bricks made with this additive had higher levels of water absorption and poorer mechanical strength. The greatest colour differences were detected after increasing the amount of waste, which generally resulted in yellower bricks. The increase in firing temperature resulted in an improvement in mechanical resistance regardless of the composition of the bricks. However, bricks fired at 1100 °C made without additive are more resistant to damage caused by salts than those made with wine pomace.

Layered double hydroxides (LDHs) are a class of anionic clays known for a long time and properly classified in the beginning of 20th century. They are composed of positively charged metal hydroxide-based sheets endowed with interlayer anions and solvent molecules to keep the electro-neutrality. LDHs have attracted increasing attention during the last years because of their rich chemical versatility and the fact that they can be exfoliated –or directly synthesized– into two-dimensional (2D) nanosheets, impacting a wide range of potential applications. Among others, magnetism stands out as one of the most appealing properties of LDHs, this is mainly due to the possibility of modulating their magnetic interactions by judicious tuning of their composition, morphology or interlayer spacing. The combination of their modulable physical properties with good processability positions these nanosheets as excellent candidates for the development of hybrid materials and heterostructures. This review addresses from the first reports to the most recent advances in the magnetic properties of LDHs and their hybrids, showing the great potential they hold as 2D quantum materials. In addition, it is also shown how magnetic properties can be useful in energy-related applications, either evaluating the purity of materials of utmost importance such as NiFe-LDHs, or elucidating their cationic order at the atomic scale, which influences the catalytic performance.

Illite is one of the most abundant clay minerals on earth, yet its structure remains not fully solved. In hydrothermal reservoir sandstones, illites can display a fibrous growth within the pores and pore throats. The network created by them and the particles trapped therein during fluid flow lead to a dramatic decrease in permeability, which should be prevented if the reservoirs were to be used for geothermal energy extraction. In order to determine possible changes in structure, stacking or shape of the illite fibers, the interaction of a sandstone with two different brines was compared to an unaltered sandstone via environmental scanning electron microscopy and transmission electron microscopy. Moreover, three-dimensional electron diffraction experiments were performed using automated diffraction tomography. The 1M_tv structure of illite could be solved based on a single dataset of a 50 nm illite fiber. Illites that were altered with synthetic Gerolstein brine showed one-dimensional diffuse scattering, indicating a disorder in the stacking of the illite layers. The degree of disorder is dependent on the potassium content of the fluid, since the K⁺ ions of the interlayer can be released via the (010) facet. This causes a stability reduction of the structure, resulting in a high fragmentation and detachment of individual illite layers. Fluids interacting with the sandstone can then transport such mobile layer fragments, leading to entangling and interweaving of illite fibers. These new insights into the structure of illite fibers show a significant dependence of the arrangement of the fibers in the pores on the potassium content of the fluid. The increased migration and interweaving of illite fibers associated with a low potassium content can lead to severe clogging of the pores and thus to a reduction in fluid permeability. Altered sandstones with illitic pore filling are therefore less suitable for long-term geothermal projects.

The study of ionic transport through hydrated sodium montmorillonite (Na-MMT)—the main swelling component of bentonite—is of significant interest to better understand its ability to contain contaminants. From a macroscopic viewpoint, porosity and tortuosity can be viewed as scaling factors connecting diffusion coefficients in the clay material to free diffusion coefficients of ions in water. In this work, the mechanical properties, porosity and tortuosity of Na-MMT were calculated using a bottom-up approach. First, the constructed coarse-grained mesoscopic models of Na-MMT were fitted to all-atom molecular dynamics simulations. Thirty different models—each containing one thousand 120 Å-wide hexagonal Na-MMT platelets—were generated. The dry densities considered herein range from 0.8 to 1.3 g/cm³. Second, calculated the models' elastic constants were in excellent agreement with experimental values reported in the literature. Third, each system's porosity, pore size distribution and pore network were analysed. Fourth, the pore network information was used to create a 3D image of hydrated Na-MMT, and random walk simulations were employed to evaluate its tortuosity. Finally, the porosity and tortuosity values estimated using the models were compared to macroscopic experimental values describing tritium and iodide diffusion in Na-MMT dominant bentonite. The values obtained using the models were fairly consistent with experimental values reported in the literature.

Since the outbreak of COVID-19, the extensive use of epidemic control drugs such as Arbidol (ARB) and Acyclovir (ACV) has significantly increased and the environmental pollution caused by these residues has attracted increasing attention. In this article, a novel montmorillonite graphene-like carbon hybrid Fe₃O₄ compound (Mt/GH/Fe₃O₄) as particle electrode catalyst was prepared and applied in three-dimensional-electro-Fenton (3D-EF) for the ARB and ACV degradation. The structure and composition of the compound catalyst were characterized. The degradation efficiency of targets was significantly increased in the 3D-EF degradation system and even more thorough for the degradation of targets, compared with simple 2D, 3D, and EF catalytic degradation systems. The degradation rate of antiviral drugs can reach >90% in 5 min with excellent stability. The research demonstrated that the clay mineral with a special structure loaded with graphene-like carbon and Fe₃O₄ had supplied an ideal reaction medium for the electro-Fenton reaction. Mt./GH/Fe₃O₄-based 3D-EF degradation system would have promising applications in the degradation and removal of antiviral drug residuals in the environment.