The discovery of the feasibility of using activated clays to produce reactive aluminosilicates has significantly expanded the raw material base for supplementary cementitious materials, opening up new prospects and options for low-carbon cements. Furthermore, the potential of kaolin clays for producing pozzolans has been thoroughly studied and practically realized. However, the more widely available and accessible non-kaolin clays of the 2:1 structural type require further comprehensive studies of their suitability in relation to the variety of influencing factors. In this study, the reactivity of five montmorillonite clays calcined at 830 °C and milled to Dv,50 of 11.5–13.8 µm was explored through chemical, mechanical, and thermal methods. Based on the consistency of results obtained through these techniques insights into the relationship between the reactivity of low-, medium, and high-grade montmorillonite clays and their chemical/mineralogical composition are presented. These findings advance the understanding of the categorization of montmorillonite clays as supplementary cementitious materials.

In the original publication [...]

ABSTRACT Electrokinetic remediation (EKR) and biochar are both effective and widely used techniques for treating chromium-contaminated soil. However, when treating soils that are previously treated with biochar, the efficiency of EKR becomes highly variable. The main reason is that biochar could act as both a promoter and an inhibitor of the EKR process. Unfortunately, this dual-mechanism of how biochar influences the efficiency of EKR has not yet been explored. This study systematically investigates the role of biochar in EKR across four representative soil components: quartz sand (QS), kaolinite (KL), organic matter (OM), and metal oxides (MO). Results demonstrated that in high-activity matrices (OM and MO), biochar served as an electron shuttle and a chelating agent, enhancing soil conductivity, promoting the reduction of Cr(VI) to Cr(III), and maintaining Cr(III) solubility by lowering pH and reducing competitive precipitation. Consequently, the total Cr removal rate in MO significantly increased from 0.4% to 15.7% compared to biochar free samples. Conversely, in low-activity substrates (QS and KL), the negative effects of biochar mostly come from pore clogging, increased mass transfer resistance, and electrostatic repulsion of Cr(VI) anions, which severely hindered chromium migration and reduced removal efficiency. This work elucidates the dual mechanisms of biochar in EKR and provides critical insights for optimizing its application in precise and sustainable soil remediation strategies.

Extracellular polymers produced by microorganisms are utilized as bioflocculants. In this study, bioflocculant-producing lactic acid bacteria were screened from seven strains based on the flocculation activity of their cultures. The Leuconostoc mesenteroides NBRC 100496 culture exhibited strong flocculation activity, with a 79.5% flocculation rate against kaolin clay. The optimal concentration of sucrose as a carbon source for the cultivation was investigated by measuring the flocculation activity of the L. mesenteroides culture. The addition of 30% sucrose was appropriate for kaolin flocculation. Kaolin exhibited a negative zeta potential, and the excessive presence of trivalent cations (Al3+ and Fe3+) caused charge inversion on the kaolin surface. The L. mesenteroides culture flocculated kaolin even under conditions where Al3+ and Fe3+ were present in excess. The glucan involved in flocculation was purified by isopropanol precipitation and alkaline treatment. The purified glucan lost its flocculation activity after dextranase treatment. Dynamic light scattering analysis revealed that the average particle size of the purified glucan was 361 nm, which was larger than that of commercially available dextrans (average molecular weight, 400,000-500,000). These results suggest that the glucan involved in flocculation exhibits α-1,6-glycosidic linkages, the particle size of the glucan is extremely large, and flocculation is caused by physical adsorption.

IO-based epoxy composites from epoxidized soybean oil, tannic acid and 2D-layered nanoclays

Sustainable stabilization of kaolin clay by waste eggshell powder & hemp fibre: Mechanical & microstructural study

Comparing the physico-chemical characteristics of calcite rich kaolinitic clays using soak and flash calcination methods

This study investigates the mechanical behavior and durability performance of kaolin clay stabilized using a hybrid system composed of Xanthan Gum biopolymer, polypropylene fibers, and Trivoltherm waste fibers. Experimental studies were designed according to the Taguchi L16 orthogonal array to evaluate the effects of different additive combinations. Unconfined compressive strength tests were performed after curing periods of 7, 28, and 90 days, while durability behavior was assessed through 5 and 10 freeze–thaw cycles. In addition, scanning electron microscopy analyses were conducted to investigate the microstructural characteristics of the stabilized soils. The results indicated that strength increased significantly with curing time, reaching a maximum value of 1186 kPa after 90 days. Statistical analyses showed that Xanthan Gum was the dominant parameter affecting strength development, contributing approximately 57–63% to the unconfined compressive strength behavior. Fiber additives also improved ductility, crack resistance, and freeze–thaw durability through reinforcement and crack-bridging mechanisms. The best-performing mixtures exhibited markedly lower strength losses under freeze–thaw conditions compared with untreated soil specimens. Analysis of variance results confirmed that the investigated parameters were statistically significant (p < 0.05), and the developed models showed high prediction accuracy (R2 > 85%). Overall, the findings demonstrate that the synergistic interaction between the biopolymer matrix and fiber reinforcement system provides an effective and sustainable hybrid stabilization approach for improving the engineering performance of clay soils.

ABSTRACT Desiccation cracks in expansive clayey soils reduce shear strength and increase permeability, posing significant challenges in geotechnical and geoenvironmental engineering. Accurate crack segmentation is essential for evaluating soil stability and mitigating infrastructure risks. This study proposes a deep learning-based semantic segmentation approach using DeepLabv3+, for automated detection of soil desiccation cracks. A dataset of 820 manually annotated, laboratory-acquired images of Kaolinite clay was used for training, validation, and testing with four backbone architectures i.e. MobileNetV2, ResNet-18, ResNet-50, and Xception. Model performance was assessed using precision, recall, F1 score, and Intersection over Union (IoU). Results show that DeepLabv3+ effectively segments cracks across all backbones. Xception achieved the highest accuracy, with precision of 89.39%, recall of 91.64%, F1 score of 90.50%, and IoU of 82.65%, while ResNet-18 demonstrated superior computational efficiency for real-time applications. These findings support accurate and efficient soil crack detection, advancing automated geotechnical analysis and monitoring.

Population growth and climate change demand technologies for the efficient use of water in agriculture. This study aimed to synthesize and characterize hybrid hydrogels of polyacrylamide and white angico gum (Anadenanthera colubrina), reinforced with kaolinitic clay and soapstone, for potential application as soil conditioners and nutrient carriers. The hydrogels were obtained via radical polymerization, followed by alkaline hydrolysis (0.1 mol L−1 NaOH) to convert amide groups into carboxylates. The results indicated that the HPAD formulation [constituted by white angico gum (1:1); 5% (w/w) kaolin and 5% (w/w) steatite (soapstone)] presented the best balance, with a maximum compressive force greater than 200 N, thermal stability up to 310 °C, and a swelling capacity of 60 g/g in saline medium, surpassing the limits of viability for use in soil. The kinetics followed the pseudo-second-order model, and the point of zero charge (pH 9.0–11.7) favored phosphate retention. It is concluded that the HPAD hydrogel, one of several hydrogel formulations developed in this study, is a viable and safe technical alternative, with non-toxicity exceeding 80% in Artemia salina assays and capable of optimizing water and nutrient efficiency in agricultural systems.

his study presents a cost-effective and efficient method for removing the synthetic dye Allura Red (E129) from aqueous solutions using kaolin clay as an adsorbent. The structural and surface properties of the kaolin clay (KC) composite were characterized through Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray (EDX) analysis. Experimental results showed that the optimal adsorption conditions were achieved at pH 3.0 using 150 mg of kaolin clay (KC). The adsorption of Allura Red (E129) followed the Freundlich isotherm model, suggesting a heterogeneous adsorption process on the kaolin surface. Thermodynamic studies confirmed that the adsorption was both spontaneous and exothermic, with a maximum adsorption capacity (qmax) of 80.25 mg/g. Additionally, kinetic model analysis revealed that the process fit the pseudo-second-order (PSO) model, indicating strong dye-adsorbent interactions and efficient removal performance. Kaolin clay (KC) proves to be a promising low-cost material for wastewater treatment applications.

Modeling the alkaline dissolution of metakaolinite

Closure to “Cyclic Behavior of Kaolin Clay under Undrained Conditions: Role of Microfabric”

Discussion of “Cyclic Behavior of Kaolin Clay under Undrained Conditions: Role of Microfabric”

Reviving indigenous electrical insulator manufacturing in sub-saharan Africa: A narrative critical review of barriers and opportunities

Comparative study on the effect of kaolin clay calcination temperature on the fabrication and properties of ceramic membranes

Abstract Gigaton-scale carbon dioxide (CO2) capture is an indispensable part of the way towards global carbon neutrality, but has lagged in developing an adsorbent that simultaneously has high performance, low cost, and scalability from earth-abundant raw materials coupled with industrially compatible synthesis processes. Here we discover that high performing CO2 adsorbent of Linda Type A (LTA) zeolite can be converted from ubiquitous kaolin clay (reserves &amp;gt; 30 gigatons) via scalable processes and exhibits record high CO2 uptake with good cycling stability. The synthesis route, comprising mainly calcination and a hyperthermal reaction, is readily compatible with existing industrial infrastructure and avoids the use of complex or toxic chemicals. Benefiting from an optimized crystal structure for CO₂ trapping, the material achieves CO₂ adsorption capacities that surpass all previously reported clay-derived zeolites across a wide concentration range, from ambient air (∼400 ppm) to flue gas conditions (&amp;lt;20%). It also maintains stable performance over 50 adsorption–desorption cycles. Beyond material and method development, we provide a proof-of-concept showing that integrating radiative cooling for CO₂ adsorption and solar heating for sorbent regeneration could enable a low-carbon pathway for passive sorbent operation. This study offers a feasible route to explore scalable carbon capture using widely available materials and passive energy strategies.

Bell pepper production is significantly constrained by insect pests, particularly the European corn borer (ECB), which causes severe yield loss. Effective control of ECB is challenging because larvae rapidly bore into plant tissues after hatching, limiting the efficacy of conventional insecticides. To address this issue, we conducted a field study to determine the effectiveness of kaolin clay as an eco-friendly alternative to insecticides to minimize ECB infestation and improve bell pepper yield. The treatments included kaolin application duration (6, 9, 12, and 15 weeks) and bell pepper cultivars (‘Captain’, ‘Alliance’, and ‘Orange Blaze’) randomized in a complete block design. The maximum efficacy in insect management was observed with the 15-week kaolin application, resulting in a 35% reduction in ECB incidence in the cultivar ‘Captain’. Kaolin application over 15 weeks significantly reduced ECB infestation while increasing fruit yield. Kaolin application reduced the ECB egg, larval, and adult populations by 69%, 56%, and 58%, respectively, relative to untreated controls. Weekly kaolin applications maintained for 12 weeks reduced flower drop by 20% and increased fruit set by 17%, resulting in a 20% increase in marketable fruit yield of ‘Captain’. The increased yield in “Captain” at 12 and 15 weeks was a result of both the combined effect of reducing insect infestation and exhibiting enhanced photosynthetic performance and other physiological responses. Overall, these results suggest that kaolin clay applied for 12 weeks is a promising and sustainable alternative to chemical pesticides to reduce ECB infestation and improve bell pepper productivity, with ‘Captain’ appearing as the best-performing cultivar among those tested.

Due to the negative carbon footprint of cement production and the decreasing availability of commonly used supplementary cementitious materials (SCM), the thermal activation of non-kaolinite clays for use as pozzolanas was investigated. The calcination potential of two bentonites was studied and compared with the performance of kaolin clay in terms of density, specific surface area, granulometry, thermal analysis, and chemical and phase compositions. Based on thermal analysis, the clays were calcined at 500°C, 550°C, 600°C and 650°C (for three hours) with a heating rate of 10°C min −1 . Then, blended pastes were prepared with the studied clays with a substitution rate of 10% of Portland cement. The pozzolanic activity of prepared pastes was investigated by isothermal calorimetry, lime saturation test (LST), changes in mechanical properties and pH activity test. Tests performed on raw clays revealed the following findings: i) temperatures needed for activation were above 550°C; ii) during firing, the bentonitic clays tend to agglomerate, which, however, can be fixed by additional milling. Results of testing on blended cements can be summarised as follows: iii) all activation temperatures show good potential for thermal activation of bentonites in terms of isothermal calorimetry; iv) lime saturation test showed a slower onset of pozzolanic reaction for bentonites compared to kaolin; v) best mechanical properties were achieved for clays heated to 600°C. • The activation of bentonites was successful for temperatures above 550°C. • Bentonitic clays tend to agglomerate during thermal activation. • Hydration heat curves of bentonitic clays overlapped for all studied temperatures. • Ca(OH) 2 consumption by bentonite clays was initially slower but later accelerated. • Best values of mechanical properties of bentonitic clay pastes were found for 600°C.

Facile Synthesis of Amine-Functionalized Activated Alumina from Kaolinite Clay for Enhanced CO₂ Capture: Structure–Property–Adsorption Relationship