Applied Clay Science最新文献

In aqueous zinc-ion batteries (AZIBs), Zn anode faces issues such as uncontrolled dendrite growth, electrode corrosion, and by-product formation. This study successfully exfoliated a 1:1 type layered clay mineral, dickite, into ultrathin dickite nanolayers (DE) with a layer thickness of less than 5 nm and a yield of over 40 % using an ultrasonic-assisted solvothermal method. These ultrathin dickite nanolayers were mixed with sodium alginate (SA) and coated onto a zinc matrix to obtain a coated Zn electrode (DE-Zn). Due to the abundant hydrophilic groups on the surface of the ultrathin dickite nanolayers, the DE-SA coating exhibited excellent electrolyte affinity. The uniform dispersion of ultrathin dickite nanolayers in the SA matrix constructed a polygonal network structure, providing rapid ion transport channels. The unique surface negative charge characteristics of the ultrathin dickite nanolayers allowed for significant ion selectivity, enhancing Zn²⁺ migration efficiency by adsorbing Zn²⁺ and repelling SO₄²⁻ in the electrolyte. The symmetric cell assembled with DE-Zn electrodes demonstrated stable operation for up to 5500 h at 0.5 mA cm⁻², with a polarization voltage of 40 mV, and remained stable even at 10 mA cm⁻². The addition of ultrathin dickite nanolayers to the coating inhibited dendrite growth, HER, and by-product formation, maintaining a stable zinc electrode interface. The DE-Zn//MnO₂ full cell assembled with DE-Zn electrodes maintained a high discharge specific capacity (144 mAh g⁻¹) after 750 cycles at 0.15 mA g⁻¹, exhibiting excellent electrochemical performance. This work provides new scientific insights for the low-cost, efficient exfoliation of clay minerals and the preparation of high-performance AZIBs.

Bentonite clay is commonly accepted as an appropriate material for backfilling the space between the radioactive canisters and the host rock of planned underground repository sites for waste disposal. Despite its favourable properties as a hydrodynamic seal, its long-term stability remains a concern. This experimental study of a Bavarian bentonite investigated advanced montmorillonite (smectite) illitisation at 180 °C in the presence of K-oxalate and/or the accessory minerals of pyrite and calcite. The formation of mixed-layered illite-smectite was quantified by X-ray diffraction Rietveld refinement and the crystal chemistry was determined by transmission electron microscopy. The results showed neocrystallisation of a celadonitic illite-smectite (up to 63% illite-layers) after treatment with KCl or K-oxalate with increased Al³⁺ in the tetrahedral sheets, reduced amounts in the octahedral locations and increased fixation of non-exchangeable K⁺ ions in response to the increased layer charges. K-oxalate complexation of Al³⁺ and enhanced dissolution of the smectite resulted in the formation of a possible intermediate amorphous phase and illite-smectite crystallites with additional vacant sites explaining the lower number of octahedral ions (<2 per formula unit). Adding 10% pyrite, 10% calcite, or 5% of each, did influence the degree of alteration to a recognisable degree in the presence of KCl, but the effects on the rate of illitisation were minimal when reacted with K-oxalate, which further increased illitisation by up to 6.4 times. Although batch reactor experiments do have limitations compared to complex repository conditions, our results do indicate that claystone host rocks low in organic matter should be favoured over organic-rich lithologies that are likely to contain oxalate ligands or similar catalysing compounds.

Tiebas Castle was built between 1254 and 1264 as a royal residence of the kings of Navarre. The Castle was decorated with architectural luxuries imported from the French court. Some decorative elements of this French style are the polychrome roof tiles, called tuiles vernissées; and the glazed floor tiles, called carreaux de pavement. Both are the unique that have been found in the Iberian Peninsula. Elemental and mineralogical analysis allowed us to distinguish two different types of pastes that were used for both tuiles vernissées and carreaux de pavement: yellowish and reddish. The reddish paste was composed mainly of quartz, and to a lesser extent of haematite and illite. The yellow pastes were very rich in calcite and other calcium-bearing minerals (gehlenite, anorthite, diopside or wollastonite) and poorer in quartz and haematite. The different colour tones of the yellow paste samples allowed them to be classified into five subgroups (YP-1, YP-2, YP-3, YP-4, and YP-5). This classification turned out to coincide with a somewhat different mineral composition. The study of the mineral phases newly formed (gehlenite, anorthite, diopside and wollastonite) or destroyed (illite) during firing allowed us to estimate the maximum firing temperature of each of the subgroups. The temperature ranges for each subgroup were as follows: 750–800 °C (YP-5), 850–900 °C (YP-4), 900–925 °C (YP-3), 925–950 °C (YP-2), and 950–1000 °C (YP-1). The study of its possible raw materials allowed us to identify that the yellow pastes from tuiles vernissées and carreaux de pavement were prepared from a mixture of two clays. One of them was the decalcification clay (A15 clay) with which they also made the reddish pastes. The other component of the mixture was the marl from Castle hill. The proportion that the artisans used of both raw materials was 1:2 (twice as much marl as decalcification clay).

As a byproduct of sand-washing process, sand-washing slurry (SWS) showed a potential geopolymer precursor due to the abundant clay minerals. This study investigated the impact of calcination temperature of SWS and SiO₂/Na₂O ratio of alkaline solution on the microstructure and mechanical properties of SWS-based geopolymers. The analysis results indicated that at a calcination temperature of 550 °C, some clay minerals in SWS underwent a transition from crystalline to amorphous phases, resulting in increased amounts of amorphous Si and Al, thereby enhancing their alkaline reactivity. However, due to the low content of amorphous phases, the formed geopolymer structure was loose, leading to lower compressive strength. Compared to geopolymer treated at 550 °C, the geopolymer produced under temperatures ranging from 650 °C to 750 °C exhibited denser microstructures and higher compressive strength. The improvement in performance was attributed to more clay minerals undergoing dehydroxylation reactions, resulting in more amorphous Si and Al participating in the polymerization reaction. Nevertheless, upon reaching a calcination temperature of 850 °C, the microstructure of the formed geopolymers became loose with diminished compressive strength due to reduced activity of Si and Al in the amorphous phase.

Furthermore, under a calcination temperature of 750 °C, the amorphous content in geopolymers with SiO₂/Na₂O ratios in the alkaline solution of 0.8 and 1.4 was 62.4 % and 64.5 %, respectively, while decreasing to 54.5 % in geopolymers with a ratio of 2. Geopolymers with a SiO₂/Na₂O ratio of 1.4 exhibited denser microstructures and higher compressive strength, indicating that alkaline solutions with this ratio promoted the formation of more amorphous materials and enhanced geopolymer strength. These findings suggested that calcination around 750 °C improved the microstructure and mechanical properties of SWS-based geopolymers, with the appropriate SiO₂/Na₂O ratio in alkaline solutions facilitating geopolymerization.

The processing of clay minerals consists, among other steps, in the removal of isolated mineral impurities, that is, not associated to crystalline structure of clay minerals, such as fractions of quartz and feldspars, originating from the process of soil formation. Thus, this work evaluated a sustainable method to reduction of isolated mineral impurities, in 4 in natura soil samples from Maranhão/Brazil, containing clay minerals. The method consisted of dispersing the samples only in water under high rotation and separating the impurities by sieving and decanting. The water and clay fraction were recovered from a manufactured solar evaporator and the clay fraction analyzed: X-ray diffraction (XRD) revealed a reduction in the intensities of mineral impurities, largely quartz, and a significant increase in the intensity corresponding to clay minerals; X-ray fluorescence (XRF) demonstrated a decrease in the SiO₂/Al₂O₃ ratio, indicating quartz removal; Fourier transform infrared analysis (FTIR) indicated removal of organic material; thermal analysis (TG/DTG) revealed an increase in the percentage of structural water loss, suggesting an increase in clay mineral content, and adsorption/desorption isotherms of N₂ demonstrated an increase in the surface areas and adsorption capacity of the benefited samples. The process yields obtained demonstrated compatibility with the particle size of the samples, with more expressive results for the more clayey ones. Thus, the investigated method, low cost and sustainable, proved to be viable and effective in obtaining clay minerals with reduced presence of isolated impurities, promoting considerable improvements in their properties, and favoring various technological applications, such as adsorption, heterogeneous catalysis, synthesis of mesoporous materials, among others.

Understanding the adsorption of organic corrosion inhibitors with different functional groups on layered double hydroxide (LDH) nanosheet is crucial for the synthesis of these protective materials. In this study, the adsorption process of five deprotonated organic corrosion inhibitors—lactate (Lc), 2-hydroxybenzothiazole (2-OH-BTH), 2-mercaptoethanesulfonic acid (MS), N,N-dimethylethanolamine (DMEA), and eugenol (EG)—on LDH nanosheets was simulated. The adsorption rate, adsorption configuration, and adsorption stability between LDH nanosheet and organic corrosion inhibitors were investigated throughout the entire adsorption process. The study observed consistency in the adsorption rate and stability of these organic corrosion inhibitors in the following order: Lc > 2-OH-BTH > MS > DMEA > EG. Additionally, hydrogen bonds between the organic corrosion inhibitors and the LDH nanosheet is the primary mechanism driving adsorption. The number and stability of hydrogen bonds influenced both the adsorption rate and stability. It is noteworthy that 2-OH-BTH and DMEA have not previously been incorporated into LDH. There is potential for these two organic corrosion inhibitors to be modified for LDH, suggesting significant prospects for future research.

The present study aimed to produce specimens made from steel fibers/metakaolin (SFs/MK) composite concrete that would achieve superior strength characteristics and controlled cracking behavior under aggressive media (i.e. sodium sulfate and sodium chloride). The composite of SF and concrete is full of porosity, creating weak zone in the specimens. Therefore, the use of clay materials is required to reduce the porosity. In this context, the general physical and chemical properties of clay, including structure and the percentage of alumina and quartz, play a significant role in forming composites with suitable mechanical properties. The changes in weight of SFs, effects of the aging period in terms of strength, and effect of aggressive solution are investigated and compared with SF reinforced concrete. The findings from N₂ adsorption-desorption, field emission scanning electron microscopy (FE-SEM), X-ray powder diffraction (XRD), X-ray fluorescence (XRF) and compressive strength tests indicate that MK with disordered stacking and higher percentage of alumina, and lower quartz content provides better bonding in the concrete composite. According to the experiments conducted in this study, a 15.0 % MK and 2.0 % SF replacement of cement increased the sulfate and chloride resistance due to porosity, and water absorption values, respectively.

Kojic acid (KA) is widely utilized in cosmetic formulations for skin brightening and as a food preservative to prevent oxidative browning in fruits and vegetables. However, its effectiveness is compromised by susceptibility to pH and temperature fluctuations, as well as oxidation after exposure to UV light. These limitations highlight the need for improvements to facilitate sustainable applications. In this study, KA was encapsulated within the interlayer space of layered yttrium hydroxide (LYH) through a two-step host-guest reaction involving dodecylsulfate and basic ethoxide anions. Examination of the X-ray diffraction (XRD) pattern of the resulting product (KA-LYH) revealed an expanded interlayer space from approximately 8.4 to 16.7 Å, conducive to a partially interdigitated bilayer arrangement of KA anions within the LYH interlayer. KA-LYH demonstrated significantly improved stability against light, heat, and oxygen compared to free KA, indicating effective confinement and protection of KA from photoreaction and oxidation in the interlayer space of LYH host. Minimal release of KA was observed in saline solution and simulated seawater, while sustained release occurred in a phosphate buffer solution even after 24 h. Notably, the KA released from the LYH interlayer space retained potent tyrosinase inhibition activity, showcasing the sustainable efficacy of KA-LYH under physiological conditions.

Carbon dioxide (CO₂) storage through aqueous mineral carbonation is recognized as a promising technology for geochemical carbon removal. Previous studies predominantly focused on individual alkaline earth silicates, such as wollastonite or serpentine, overlooking their interactive effects on carbonation processes. To address this knowledge gap, we conducted aqueous carbonation tests using individually ball-milled serpentine (m-serpentine), wollastonite (m-wollastonite), mixtures of ball-milled serpentine and wollastonite (m-serpentine + m-wollastonite), and the co-milled serpentine and wollastonite (m-(serpentine + wollastonite)). The carbonation of (m-serpentine + m-wollastonite) involved the formation of a combination of calcite (CaCO₃) and magnesite (MgCO₃), suggesting that no significantly interactive effect between the serpentine and wollastonite. In contrast, carbonating m-(serpentine + wollastonite) results in the precipitation of Mg-bearing calcite ((Mg, Ca)CO₃). Upon quantification, the carbonation degrees of m-(serpentine + wollastonite) is relatively higher than that of (m-serpentine + m-wollastonite). During the carbonation of m-(serpentine + wollastonite), the combination of serpentine and wollastonite facilitates mutual dissolution, leading to the release of more cations. However, these released ions do not diffuse into the bulk carbonating solution; instead, carbonation occurs exclusively at the mineral-water interface. Consequently, the co-milling process, merging Ca-rich wollastonite into Mg-rich serpentine, induces the formation of (Mg, Ca)SiO₃. These novel insights into aqueous carbonation using a combination of Mg-containing and Ca-containing minerals underscore the significant role of mineral-mineral reactions in CO₂ mineralization.