Abstract Multifunctional coatings represent the most widely used strategy for extending the service life of metallic materials in harsh environments. However, coating performance is determined by the designed functional fillers, or the micro/nano-containers. Attapulgite (ATP) has attracted increasing attention in multifunctional coating systems because it can simultaneously improve barrier performance, act as a micro/nano-container for active agents, form surface micro- and nanostructures and regulate interfacial properties. These features enable its broad use in superhydrophobic, anti-corrosion, anti-bacterial/anti-fouling, self-cleaning/anti-smudge and anti-icing coatings. This review provides a comprehensive overview of recent progress in ATP-based multifunctional protective coatings. It examines the main pretreatment strategies for ATP, including thermal treatment, acid/alkali activation, hydrothermal treatment and solvothermal treatment, together with their influence on channel characteristics, surface activity, dispersibility and matrix compatibility. The diverse roles of ATP in coating systems are further discussed, ranging from barrier-phase reinforcement and micro/nano-container construction to roughness generation and interfacial functional regulation, as well as the corresponding protective mechanisms. By integrating the discussion of passive barrier enhancement and active functional protection, this review offers a unified perspective on the design of ATP-based multifunctional coatings. In addition, current challenges and future research directions are briefly outlined to promote the practical development of high-performance ATP-enabled protective coatings.
Abstract The significant threat posed by harmful microorganisms to human health and environmental sanitation has garnered considerable attention. Sepiolite, with its natural nanofibre structure, excellent physicochemical properties and good biocompatibility, shows great potential for antimicrobial applications in healthy living environments. In this study, magnesium oxide nanocrystal/sepiolite composites (MgO/sepiolite) were synthesized via an acid leaching–hydrothermal combined method using sepiolite without the addition of external magnesium salts, and their antimicrobial performance for bacteria and fungi was investigated. As both a magnesium source and carrier material, sepiolite effectively improved the dispersion of MgO nanoparticles by utilizing its large specific surface area, facilitating the formation of a greater quantity of smaller-sized MgO nanoparticles and abundant oxygen vacancies. The resulting MgO/sepiolite composites retained the fibre morphology of sepiolite, with the MgO nanoparticles uniformly dispersed on the fibre surface and with particle sizes in the range of 1.0–2.5 nm. The synergistic effects of these advantages of the MgO/sepiolite composite contributed to improved antimicrobial performance, leading to 99.99% antibacterial rates against Escherichia coli and Staphylococcus aureus , and a fungal growth grade of 0 against mixed fungi. Analyses of the pH value changes in the bacterial solution, Mg 2+ release, free radical concertation and Fourier-transform infrared spectra data revealed that the excellent antimicrobial performance is primarily attributable to oxygen vacancy-mediated reactive oxygen species damage. Additionally, the release of Mg 2+ , pH adjustment and contact killing synergistically improved the oxygen vacancy-mediated damage, thus contributing to the antibacterial performance. This study is expected to provide valuable insights into the design and development of novel clay-based antimicrobial function materials, particularly with respect to synthesis methodology and the elucidation of antimicrobial mechanisms.
Abstract The reduction of volatile organic compounds (VOCs), especially the oxidation of highly toxic and chemically resistant toluene, remains a challenge in environmental catalysis. In this research, a porous TiO 2 /SiO 2 support was initially fabricated through titanium pillaring of montmorillonite and then calcined and acid-leached as an efficient platform for Pt nanoparticle immobilization to yield Pt–TiO 2 /SiO 2 . The experimental data showed that the catalyst loaded with 0.37 wt.% Pt (0.37Pt–TiO 2 /SiO 2 ) exhibits superior toluene oxidation performance, reaching a T 90 of 190°C. Moreover, the catalyst exhibited remarkable water resistance, maintaining high efficiency even in the presence of 10% water vapour and outstanding long-term stability, with no substantial deactivation after 48 h of continuous operation. The performance improvement is explained by the high dispersion of Pt nanoparticles on the support and the metal–support interaction between Pt and TiO 2 , characterized by electron transfer from TiO 2 to Pt. This interaction facilitates the adsorption and activation of reactant molecules. In situ diffuse reflectance Fourier-transform infrared spectroscopy explained the catalytic mechanism: toluene is sequentially transformed into benzyl alcohol, benzaldehyde and benzoate intermediates, which are subsequently converted to maleic anhydride by opening the ring and eventually mineralized into CO 2 and H 2 O. This work developed a high-performance, durable catalyst using cost-effective and abundant natural minerals, offering promising prospects for practical abatement of industrial VOCs.
Rapid and efficient haemostasis is key to controlling bleeding and reducing mortality, and so it is necessary to design high-performance haemostatic materials. Here, haemostatic gauze composites were facilely prepared based on dopamine polymerization modification of gauze and simultaneous impregnation loading of mixed-dimensional palygorskite clay (MDPal). The haemostatic performance of gauze composites was systematically evaluated in comparison with a commercially available gauze impregnated with kaolin. The results confirmed that no obvious changes were observed regarding the water vapour transmittance and water absorption of the gauze after coating with polydopamine and MDPal. Blood coagulation studies indicated that the optimal gauze composites prepared with 200 mg of dopamine after reaction for 6.5 h presented superior haemostatic properties according to the in vitro blood-clotting index, the coagulation kinetics of platelet-poor plasma coagulation, erythrocyte adhesion behaviour and thrombus formation. The haemorrhage effects on rat liver bleeding suggested that the blood losses with the gauze composites were 8.52% and 29.45% less than that of the blank group. In addition, the coagulation time decreased by 38.12% compared with the blank group. Furthermore, the gauze composites exhibited good biocompatibility as evaluated by haemolysis rate and cytotoxicity assays. Thus, the obtained gauze composites can serve as promising candidates for rapid wound haemostasis.
Abstract Palygorskite (Pal) is a layered-chain clay mineral characterized by unique one-dimensional nanorod crystals, regular nanochannels and abundant surface active groups. Since the discovery of Pal’s presence in China in 1976, Chinese scientists have resolved the key bottleneck of efficient the disaggregation of the rod crystal bundles restricting its high-value utilization and achieved a fundamental transformation of Pal from a traditional raw mineral material to an advanced functional nanomaterial. The applications of Pal in China have expanded into diverse fields, including energy materials, antibacterial agents, catalysts, tissue engineering scaffolds, hydrogen storage materials, membrane separation materials, functional coatings and pigments, among others. In the case of naturally abundant mixed-dimensional Pal clays with complex mineral compositions, full-mineral synchronous utilization technology has been developed for the fabrication of functional materials based on the differences and complementarities in the structures and properties of the coexisting minerals. This article reviews the significant progress made by Chinese researchers in transforming nanostructured Pal into advanced functional materials, highlighting representative cases in green preparation and sustainable applications. Finally, future key research directions are proposed to promote the efficient and sustainable utilization of Pal resources, aligning with the disciplinary frontier of mineral materialization.
Converting CO2 into value-added fuels via photocatalysis represents a promising strategy to address the energy crisis and global climate challenges. The core of the matter lies in constructing an optimal photocatalytic system featuring broadband light utilization, high charge separation efficiency and abundant surface-active centres. To overcome obstacles including high cost, complex processes and poor environmental compatibility of synthetic photocatalysts, this study constructs kaolinite/pyrite (KL/Py) composite photocatalysts via a green mechanical ball milling method based on natural mineral symbiosis characteristics, using the abundant 1:1 layered clay mineral KL and the narrow-bandgap mineral Py as raw materials. Although the KL and Py used in this work are obtained from different commercial sources, their typical coexistence in sedimentary deposits inspires the design of this composite. By adjusting the composite mass ratio, the obtained composite exhibits the best photocatalytic activity, and its CO yield can reach up to 89.5 mu mol g(-1) h(-1), which is 2.3 times higher than that of Py alone. The synergistic interaction between KL and Py markedly improves the efficiency of charge transfer at the interface and inhibits the recombination of photogenerated carriers. In addition, the hydroxyl-enriched surface of KL serves as an active centre for CO2 uptake and hole capture. This composite photocatalyst demonstrates outstanding and durable performance in photocatalytic CO2 conversion and offers a novel theoretical foundation and an eco-friendly synthesis route for the value-added application of clay minerals and the development of natural mineral-based photocatalysts.
Abstract The 14 elements from La to Lu (except the unstable Pm) form a group with similar chemical characteristics provided by their electronic configurations. Widespread, albeit in low abundance (hence their original description as ‘rare’), they were soon viewed as an opportunity to trace rock origins and geological processes. In addition to this scientific use, their technological applications have increased over the decades, which have multiplied in the present electronic age. Their exponential growth in demand and limited abundance have transformed them into strategic resources. Characteristic of clay minerals, which take centre stage in so many industrial applications and scientific issues, they have been discovered to be involved in this story as important commercial rare earth element ( REE ) deposits. This review describes how phyllosilicates bind REE , how environmental conditions modify REE contents in phyllosilicates and how such interactions can be used to trace both original rocks and the nature of modifying geological processes. Phyllosilicates bind REE strongly and concentrate them as adsorbed species in inner and outer poly-coordination complexes. This mode of binding controls the capacity for REE retention by phyllosilicates in conjunction with the physicochemical conditions of environmental fluids (salinity, pH, temperature, ligands, Eh) and fluid:rock ratios to determine the contribution of clay minerals to bulk REE signatures and their modifications in geological processes (soil formation, clay mineral precipitation from fluids, alteration, diagenesis, ore formation, transport).
Abstract The influence of exchangeable alkali cations on glucose uptake, interlayer reorganization and ionic transport was investigated in homoionic Wyoming montmorillonite exchanged with the complete alkali series (Li + , Na + , K + , Rb + and Cs + ). Glucose adsorption was rapid during the initial stage and reached equilibrium after ∼6 h. Under the investigated conditions, the equilibrium uptake was highest for the Li- and Cs-exchanged forms, whereas the Na-exchanged form showed the lowest adsorption amount. X-ray diffraction, differential thermal analysis and Fourier-transform infrared spectroscopy collectively support partial accommodation of glucose within the interlayer region without major disruption of the aluminosilicate framework, although the magnitude of the structural response depended strongly on the exchangeable cation. The largest basal expansion was observed for the Li- and Na-exchanged forms, showing that interlayer opening does not directly parallel adsorption capacity across the alkali series. Broadband impedance spectroscopy further indicates thermally activated ionic transport and a marked cation dependence of both direct current (DC) conductivity and activation energy after glucose loading. In particular, glucose adsorption altered the conduction environment more strongly in the Li- and Na-exchanged systems than in the K-, Rb- and Cs-exchanged forms under the same thermal conditioning. Taken together, the results suggest that glucose uptake, interlayer expansion and ionic transport are governed by coupled effects involving cation hydration, interlayer accessibility and local structural organization rather than by a single cation property alone. This comparative dataset provides a basis for understanding how exchangeable cations regulate saccharide–clay interactions in montmorillonite.
Oil-based drilling fluids (OBDFs) are widely used in high-temperature ultra-deep wells, high-inclination wells, horizontal wells and various complex wellbores due to their excellent lubricity, high temperature stability, salt tolerance and contamination resistance. However, the intrusion of drill cuttings during drilling destabilizes water-in-oil (W/O) emulsion drilling fluids. Therefore, bentonite - a common component of drill cuttings - was selected to study the factors influencing its dispersion stability in W/O emulsions. The macroscopic stability of the system was evaluated via static observation, and the dispersion state was characterized using optical microscopy. Additionally, the viscosity, the contact angle of bentonite after adsorption of various surfactants, the interfacial tension and the charge of the bentonite particles were measured. The results indicate that various surfactants affect dispersion stability through distinct mechanisms. The system stabilized by a non-ionic surfactant exhibited low interfacial tension and the greatest stability. Furthermore, dispersion stability increased with surfactant concentration. Finally, binary surfactant systems were formulated with Span80. Calcium stearate demonstrated a significant synergistic effect with Span80, improving the stability of the bentonite dispersed in the emulsion, with an optimal ratio of 1:1. The mechanism of the stable dispersion of bentonite in oil was analysed, providing theoretical guidance for improving the stability of W/O emulsion drilling fluids during drilling operations.
This study investigates the potential of six illite-rich clay samples from the Lower Cretaceous outcrops of Zemlet El Beidha (southern Tunisia) as precursors for geopolymer synthesis. Tau he raw materials are predominantly illitic, although kaolinite remains a main reactive phase. Samples BHG2 and BHG5 were specifically selected for further investigation due to their relatively high kaolinite content compared to the remaining samples and due to their distinct secondary mineralogy, with BHG2 being rich in hematite and BHG5 being rich in calcite. This selection allowed for a comparative analysis of how different impurities affect geopolymerization. The samples were calcined at 550 degrees C, 750 degrees C and 950 degrees C to determine the optimal dehydroxylation temperature. Alkali activation was systematically performed using 10, 12 and 14 M NaOH solutions to assess the influence of alkalinity on the polycondensation process. The 12 M NaOH was most effective for the dissolution of aluminosilicate phases without the detrimental effects of excess sodium. Structural characterization (X-ray diffraction, Fourier-transform infrared spectroscopy and scanning electron microscopy) confirmed that the greatest compressive strength (similar to 8 MPa) was achieved with BHG5 calcined at 750 degrees C. Although this strength is lower than that of kaolinite-based geopolymers, it meets the requirements for non-structural applications, such as thermal insulation or lightweight masonry units. This research demonstrates a viable pathway for valorizing abundant illitic-kaolinitic Tunisian clays into sustainable construction materials.
Compared with superhydrophobic coatings, superamphiphobic coatings offer broader application potential in various fields. However, their practical applications are often hindered by insufficient repellency towards low-surface-tension, high-viscosity and complex multicomponent liquids, as well as by their stability. Herein, a palygorskite-based stable superamphiphobic coating with a simple fabrication process and low cost is reported. The coating was fabricated through sequential spray deposition of a fluorosilicone resin (FSR) bonding layer and a superamphiphobic functional layer composed of fluorinated palygorskite (F-PAL), fluorinated carbon black (F-CB) and FSR. In this coating, F-PAL nanorods serve as the building blocks for constructing the primary nanostructure, while F-CB nanoparticles occupy the interstitial spaces between the PAL nanorods, forming the secondary nanostructure. Together, these components generate a multiscale hierarchical micro-/nanostructure that is critical for achieving superamphiphobicity. By systematically optimizing the mass ratio of F-CB to F-PAL and the FSR content, a low-surface-energy multiscale hierarchical micro-/nanostructure was successfully established, imparting the coating with excellent superamphiphobicity towards water, hydroxyl-terminated polybutadiene/dioctyl sebacate mixtures (HTPB-H) and their aluminium powder-containing suspensions (HTPB-H/Al). The coating exhibits outstanding mechanical, chemical and thermal stability. Furthermore, the coating demonstrates remarkable anti-adhesion performance against both HTPB-H and HTPB-H/Al, together with superior passive anti-icing performance, as evidenced by a significantly prolonged freezing delay time (1291 s, similar to 30-fold increase) and a substantially reduced ice adhesion strength (from 224.3 to 65.8 kPa). Moreover, efficient photothermal de-icing performance was achieved under low-temperature, high-humidity and weak-light conditions. These results demonstrate that the proposed superamphiphobic coating holds significant promise for practical applications in anti-adhesion and anti-icing under harsh conditions.
Santa Maria Island (Azores, Portugal) hosts diverse clayey materials derived from the intense weathering of basaltic-andesitic volcanic units, volcaniclastic deposits and localized Miocene marine sediments. This study provides a preliminary characterization of 20 clay samples to assess their suitability for ceramics. Textural analyses revealed a clay fraction often of >70%, indicating advanced alteration, and a particle-size distribution favourable for ceramic processing. The clayey materials are dominated by total phyllosilicates, with kaolinite prevailing, along with minor quartz, Fe- and Ti-oxides and scarce feldspars as accessory phases. The materials are characterized by high Al2O3 and Fe2O3 contents and low CaO-Na2O contents, with Chemical Index of Alteration values of 88-98%, consistent with intense leaching under humid weathering conditions. Technological tests revealed low to moderate cation-exchange capacities in kaolinite-rich samples and greater values in smectitic and palygorskitic clays. Abrasivity is variable, controlled by the quartz content, microstructure and grain angularity, while density remained within expected ranges. According to their consistency, most samples are projected within the medium- to high-plasticity field, compatible with requirements for structural ceramics, with plastic index/liquid limit ratios comparable to successful red ceramic formulations. Rheological measurements showed predominantly shear-thinning behaviour, ranging from nearly Newtonian kaolinitic suspensions to highly pseudoplastic smectitic gels, suggesting that blending strategies may be necessary. The SiO2-Al2O3-total flux ternary diagram indicated that most samples fall within compositional domains comparable to those of widely used ceramic clay bodies, with a subset shifted towards greater total flux contents. The Santa Maria Island clays constitute a robust and versatile clay resource base suitable for red structural ceramics and, in specific cases, showing technological compatibility with healing clay/peloid-type applications.
