Pub Date : 2026-01-01Epub Date: 2025-11-15DOI: 10.1016/j.clay.2025.108044
M. Farjad Iqbal, Nishant Garg
Calcined clays (CCs) are promising supplementary cementitious materials given their potential for improving concrete durability and sustainability. However, they often cause high water demand and associated workability challenges. In this study, the rotational rheology of 16 cement and largely kaolinitic-CC blends was analyzed, revealing a wide range of dynamic yield stress (DYS) values (25–300 Pa). These DYS values strongly correlate with the ASTM C1437 paste flow, ranging from ∼30 % to 140 % (R2 > 0.9). Interestingly, calorimetry results indicated that the rheological properties are linked to the onset heat (OH). By combining 3 unique parameters: OH, and particle size distribution (PSD) outputs (D10 and D50) a new parameter has been introduced, the onset heat size index (OHSI = OH/D10·D50). This OHSI can reliably predict the DYS (R2 = 0.90, RMSE = 26 Pa), opening a pathway for employing widely adopted calorimetry and PSD measurements to simultaneously predict reactivity and rheology of cement-CC blended systems.
{"title":"OHSI – Onset Heat Size Index: A new parameter to predict rheology of cement-calcined clay blends","authors":"M. Farjad Iqbal, Nishant Garg","doi":"10.1016/j.clay.2025.108044","DOIUrl":"10.1016/j.clay.2025.108044","url":null,"abstract":"<div><div>Calcined clays (CCs) are promising supplementary cementitious materials given their potential for improving concrete durability and sustainability. However, they often cause high water demand and associated workability challenges. In this study, the rotational rheology of 16 cement and largely kaolinitic-CC blends was analyzed, revealing a wide range of dynamic yield stress (DYS) values (25–300 Pa). These DYS values strongly correlate with the ASTM C1437 paste flow, ranging from ∼30 % to 140 % (R<sup>2</sup> > 0.9). Interestingly, calorimetry results indicated that the rheological properties are linked to the onset heat (OH). By combining 3 unique parameters: OH, and particle size distribution (PSD) outputs (<em>D</em><sub>10</sub> and <em>D</em><sub>50</sub>) a new parameter has been introduced, the onset heat size index (OHSI = OH/<em>D</em><sub>10</sub><em>·D</em><sub>50</sub>). This OHSI can reliably predict the DYS (R<sup>2</sup> = 0.90, RMSE = 26 Pa), opening a pathway for employing widely adopted calorimetry and PSD measurements to simultaneously predict reactivity and rheology of cement-CC blended systems.</div></div>","PeriodicalId":245,"journal":{"name":"Applied Clay Science","volume":"279 ","pages":"Article 108044"},"PeriodicalIF":5.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145526237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lightweight aggregates (LWAs) are granular materials with a highly porous interior and an external sintered layer formed during high-temperature processing. The potential of LWAs is significant in construction, as they improve energy efficiency, lightness, and enhance fire resistance. The applications of LWAs have also extended to various fields, including water treatment, adsorption processes, hydroponics, horticulture, green roofs, and other agronomic applications. The aim of this study is to evaluate the suitability of the Argentinian waste shales as a raw material to manufacture LWAs, as a potential solution for its disposal and to add value to this waste. At the same time, it can contribute to expanding the use of waste clays and shales from quarries with illite and chlorite clay minerals. This work includes the thermal transformations of shales using thermogravimetric analysis and hot-stage microscopy. The shales are used as raw material to produce sintered LWAs under two thermal treatment conditions, conventional and rapid heating, and two maximum temperatures, 1150 and 1200 °C. Finally, the mineralogical composition, microstructure, and technological properties of the LWAs are analyzed. The results show that Argentinian waste shales containing illite and chlorite clay minerals can be successfully used for manufacturing LWAs with sintering treatment at 1200 °C. Conventional sintering favours the formation of larger diameter pores, while rapid sintering produces a higher number of smaller pores and improves compressive strength. The selection will depend on the desired technological properties. This study provides a foundation for future research and promotes the industrial production of LWAs in developing countries.
{"title":"Thermal assessment of Argentinian waste shales for manufacturing lightweight aggregates","authors":"Cecilia Lucía Martinefsky , Anabella Mocciaro , Edgardo Fabián Irassar , Alejandra Tironi","doi":"10.1016/j.clay.2025.108054","DOIUrl":"10.1016/j.clay.2025.108054","url":null,"abstract":"<div><div>Lightweight aggregates (LWAs) are granular materials with a highly porous interior and an external sintered layer formed during high-temperature processing. The potential of LWAs is significant in construction, as they improve energy efficiency, lightness, and enhance fire resistance. The applications of LWAs have also extended to various fields, including water treatment, adsorption processes, hydroponics, horticulture, green roofs, and other agronomic applications. The aim of this study is to evaluate the suitability of the Argentinian waste shales as a raw material to manufacture LWAs, as a potential solution for its disposal and to add value to this waste. At the same time, it can contribute to expanding the use of waste clays and shales from quarries with illite and chlorite clay minerals. This work includes the thermal transformations of shales using thermogravimetric analysis and hot-stage microscopy. The shales are used as raw material to produce sintered LWAs under two thermal treatment conditions, conventional and rapid heating, and two maximum temperatures, 1150 and 1200 °C. Finally, the mineralogical composition, microstructure, and technological properties of the LWAs are analyzed. The results show that Argentinian waste shales containing illite and chlorite clay minerals can be successfully used for manufacturing LWAs with sintering treatment at 1200 °C. Conventional sintering favours the formation of larger diameter pores, while rapid sintering produces a higher number of smaller pores and improves compressive strength. The selection will depend on the desired technological properties. This study provides a foundation for future research and promotes the industrial production of LWAs in developing countries.</div></div>","PeriodicalId":245,"journal":{"name":"Applied Clay Science","volume":"279 ","pages":"Article 108054"},"PeriodicalIF":5.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145576431","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The growing global energy demand and environmental concerns necessitate innovative thermal energy storage solutions. Phase change materials (PCMs), particularly organic PCMs like stearic acid (SA), offer high latent heat storage capacity but face challenges such as leakage and low thermal conductivity. This study presents a novel strategy to synthesize hierarchical porous honeycomb kaolinite (HPCK) microspheres via spray drying, calcination, and hydrothermal reconstruction for encapsulating SA. The HPCK/SA composite form-stable PCM (CFSPCM) demonstrates superior thermal performance, with a melting enthalpy of 104.6 J/g and crystallization enthalpy of 105.4 J/g, alongside enhanced shape stability and thermal conductivity (0.51 W/m·K). Structural characterization reveals that HPCK's hierarchical porosity (BET surface area of 220.1 m2/g, 0.76 cm3/g pore volume) effectively immobilizes SA through physical interactions, preventing leakage even at 90 °C. Cyclic stability tests confirm retention of 90 % latent heat after 200 thermal cycles. This work advances the design of clay-based CFSPCMs for scalable applications in building thermal management, solar energy storage, and industrial waste heat recovery.
{"title":"Hierarchical porous kaolinite microspheres for leakage-resistant and high-conductivity phase change composites in advanced thermal energy storage","authors":"Qian Zhang , Xiaoguang Zhao , Xiaochao Zuo , Huaming Yang","doi":"10.1016/j.clay.2025.108029","DOIUrl":"10.1016/j.clay.2025.108029","url":null,"abstract":"<div><div>The growing global energy demand and environmental concerns necessitate innovative thermal energy storage solutions. Phase change materials (PCMs), particularly organic PCMs like stearic acid (SA), offer high latent heat storage capacity but face challenges such as leakage and low thermal conductivity. This study presents a novel strategy to synthesize hierarchical porous honeycomb kaolinite (HPCK) microspheres via spray drying, calcination, and hydrothermal reconstruction for encapsulating SA. The HPCK/SA composite form-stable PCM (CFSPCM) demonstrates superior thermal performance, with a melting enthalpy of 104.6 J/g and crystallization enthalpy of 105.4 J/g, alongside enhanced shape stability and thermal conductivity (0.51 W/m·K). Structural characterization reveals that HPCK's hierarchical porosity (BET surface area of 220.1 m<sup>2</sup>/g, 0.76 cm<sup>3</sup>/g pore volume) effectively immobilizes SA through physical interactions, preventing leakage even at 90 °C. Cyclic stability tests confirm retention of 90 % latent heat after 200 thermal cycles. This work advances the design of clay-based CFSPCMs for scalable applications in building thermal management, solar energy storage, and industrial waste heat recovery.</div></div>","PeriodicalId":245,"journal":{"name":"Applied Clay Science","volume":"279 ","pages":"Article 108029"},"PeriodicalIF":5.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145414423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-11-14DOI: 10.1016/j.clay.2025.108047
Marco Brysch , Ben Laurich , Monika Sester
In this study, an automatic method for segmenting pores in scanning electron microscopy images was developed. An ensemble of machine learning classifiers was combined with a fully connected conditional random field to obtain a spatial pore probability field. This field was then thresholded to produce coherent binary pore masks, and a confidence per pore was defined to quantify the reliability of the segmentation. The approach was demonstrated on a broad-ion-beam polished sample of the shaley facies of the Opalinus Clay. Accurate segmentation enabled the derivation of pore size distributions (PSD), pore morphologies, orientations, and spatial statistics. By using the median of per size range, a data-driven lower truncation limit for PSD fitting was established. The resulting microstructural metrics supported the interpretation of rock properties such as permeability. These results highlighted the method’s relevance for materials such as Opalinus Clay, which is investigated as a potential candidate for a host rock for nuclear waste storage.
{"title":"Pore segmentation in electron micrographs: A probabilistic approach by ensemble machine learning","authors":"Marco Brysch , Ben Laurich , Monika Sester","doi":"10.1016/j.clay.2025.108047","DOIUrl":"10.1016/j.clay.2025.108047","url":null,"abstract":"<div><div>In this study, an automatic method for segmenting pores in scanning electron microscopy images was developed. An ensemble of machine learning classifiers was combined with a fully connected conditional random field to obtain a spatial pore probability field. This field was then thresholded to produce coherent binary pore masks, and a confidence per pore <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>l</mi></mrow></msub></math></span> was defined to quantify the reliability of the segmentation. The approach was demonstrated on a broad-ion-beam polished sample of the shaley facies of the Opalinus Clay. Accurate segmentation enabled the derivation of pore size distributions (PSD), pore morphologies, orientations, and spatial statistics. By using the median of <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>l</mi></mrow></msub></math></span> per size range, a data-driven lower truncation limit for PSD fitting was established. The resulting microstructural metrics supported the interpretation of rock properties such as permeability. These results highlighted the method’s relevance for materials such as Opalinus Clay, which is investigated as a potential candidate for a host rock for nuclear waste storage.</div></div>","PeriodicalId":245,"journal":{"name":"Applied Clay Science","volume":"279 ","pages":"Article 108047"},"PeriodicalIF":5.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145526236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-11-12DOI: 10.1016/j.clay.2025.108032
Tilo Kneuker , Thomas Mann , Reiner Dohrmann , Kristian Ufer , Martin Blumenberg , Jochen Erbacher , André Bornemann , Bernhard Schuck , Géraldine Nicole Zimmerli , Lukas Pollok
The Middle Jurassic Opalinus Clay (OPA) in Switzerland and southern Germany is regarded as a potential host rock for the disposal of high-level radioactive waste. This study investigates sediment samples from drill cores taken from the Swabian Alb region (southern Germany), and employs a facies-based approach combined with mineralogical analyses, measurements of cation exchange capacity (CEC), and Rock-Eval pyrolysis. Special focus was given to the analysis of the degree of ordering of irregular illite-smectite interstratified clay minerals (I-S) that are responsible for the sorption of radionuclides and the swelling properties of the rocks.
The observations support the classification of OPA at the study site into three facies associations (FA-1: clay-rich lower part, FA-2: silty middle part, FA-3: silty upper part with interbedded calcareous-sandy beds), and further into subfacies (SF), in addition to the established twofold lithostratigraphic division into the Zillhausen and Teufelsloch Member. The percentages of clay fraction (<2 μm) varies across different lithofacies, correlating with variations in CEC.
Crystal structure-based Rietveld refinement indicates that the proportion of illitic layers in the I-S phase averages between 77 % and 83 % across all refinements and ordering types. No significant differences in the illite:smectite ratio of the I-S phases were observed between the two studied sites, however, a difference in the degree of ordering was identified. This variation may be attributed to differences in the burial history of the two localities and/or a mixture of different domains. A preliminary comparison with results from the OPA in Switzerland reveals that the average proportion of illite layers in the I-S (approximately 77 % for Mont Terri) closely aligns with the results observed in southern Germany.
The findings of this study underscore the importance of integrating lithofacies studies with mineralogical investigations to effectively assess the variability and comparability of clay-rich host rocks suitable for radioactive waste disposal.
{"title":"Compositional-structural properties of the Opalinus Clay in southern Germany: Combining facies-based studies and mineralogical analyses","authors":"Tilo Kneuker , Thomas Mann , Reiner Dohrmann , Kristian Ufer , Martin Blumenberg , Jochen Erbacher , André Bornemann , Bernhard Schuck , Géraldine Nicole Zimmerli , Lukas Pollok","doi":"10.1016/j.clay.2025.108032","DOIUrl":"10.1016/j.clay.2025.108032","url":null,"abstract":"<div><div>The Middle Jurassic Opalinus Clay (OPA) in Switzerland and southern Germany is regarded as a potential host rock for the disposal of high-level radioactive waste. This study investigates sediment samples from drill cores taken from the Swabian Alb region (southern Germany), and employs a facies-based approach combined with mineralogical analyses, measurements of cation exchange capacity (CEC), and Rock-Eval pyrolysis. Special focus was given to the analysis of the degree of ordering of irregular illite-smectite interstratified clay minerals (I-S) that are responsible for the sorption of radionuclides and the swelling properties of the rocks.</div><div>The observations support the classification of OPA at the study site into three facies associations (FA-1: clay-rich lower part, FA-2: silty middle part, FA-3: silty upper part with interbedded calcareous-sandy beds), and further into subfacies (SF), in addition to the established twofold lithostratigraphic division into the Zillhausen and Teufelsloch Member. The percentages of clay fraction (<2 μm) varies across different lithofacies, correlating with variations in CEC.</div><div>Crystal structure-based Rietveld refinement indicates that the proportion of illitic layers in the I-S phase averages between 77 % and 83 % across all refinements and ordering types. No significant differences in the illite:smectite ratio of the I-S phases were observed between the two studied sites, however, a difference in the degree of ordering was identified. This variation may be attributed to differences in the burial history of the two localities and/or a mixture of different domains. A preliminary comparison with results from the OPA in Switzerland reveals that the average proportion of illite layers in the I-S (approximately 77 % for Mont Terri) closely aligns with the results observed in southern Germany.</div><div>The findings of this study underscore the importance of integrating lithofacies studies with mineralogical investigations to effectively assess the variability and comparability of clay-rich host rocks suitable for radioactive waste disposal.</div></div>","PeriodicalId":245,"journal":{"name":"Applied Clay Science","volume":"279 ","pages":"Article 108032"},"PeriodicalIF":5.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145526235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-10-22DOI: 10.1016/j.clay.2025.108008
Ritwick Sudheer Kumar, Laurence N. Warr, Balu R. Thombare, Tobias Manzel, Georg H. Grathoff
Smectite-rich bentonites are widely used as engineered barriers, and consequently, their stability and alteration behaviour have been extensively studied. Small hematite crystals frequently form during the alteration of bentonite under oxidising conditions; however, the mechanism of Fe2O3 formation remains poorly understood, especially its relationship to smectite alteration. This study presents mineralogical and geochemical analyses of hematite neocrystallisation from the experimental alteration of a purified montmorillonite fraction isolated from a Bavarian bentonite. Experiments were conducted in eight batch reactors containing monomineralic Na-saturated montmorillonite and a 0.1 M NaCl solution, at temperatures ranging from 160 to 220 °C and durations of 1–5 months, while other parameters were kept constant. Hematite crystallisation and smectite alteration mechanisms were investigated using transmission electron microscopy, X-ray diffraction and solution chemistry analyses. Results indicate that Fe ions released from partial dissolution (up to 7 wt%) of montmorillonite were mobilised and incorporated into neocrystallised hematite, producing log-normal crystal size distributions consistent with supply-controlled ripening mechanisms of crystal growth in a closed system. Time-dependent data indicate hematite growth is kinetically supply-controlled and self-limiting in low-Fe smectites, suggesting minimal long-term impact on engineered barrier performance. As iron oxides on clay minerals can mediate electron transfer in fluctuating redox environments, hematite formation may influence subsequent alteration processes, including microbial activity. Mass balance calculations suggest the formation of up to 6 % amorphous SiO2, potentially limiting further reaction progress under these conditions.
富蒙脱石膨润土被广泛用作工程屏障，因此对其稳定性和蚀变行为进行了广泛的研究。膨润土在氧化条件下的蚀变过程中经常形成小赤铁矿晶体；然而，对于Fe2O3的形成机制，特别是其与蒙脱石蚀变的关系，人们仍然知之甚少。本研究介绍了从巴伐利亚膨润土中分离的纯蒙脱土部分的实验蚀变中赤铁矿新结晶的矿物学和地球化学分析。实验在8个间歇反应器中进行，反应器中含有单矿物钠饱和蒙脱土和0.1 M NaCl溶液，温度范围为160 ~ 220℃，持续时间为1 ~ 5个月，其他参数保持不变。利用透射电镜、x射线衍射和溶液化学分析研究了赤铁矿结晶和蒙脱石蚀变机理。结果表明，蒙脱土部分溶解释放的铁离子（高达7 wt%）被动员并结合到新结晶的赤铁矿中，产生对数正态的晶体尺寸分布，符合封闭系统中晶体生长的供应控制成熟机制。随时间变化的数据表明，在低铁蒙脱石中，赤铁矿的生长是动态供应控制和自我限制的，这表明对工程屏障性能的长期影响最小。由于粘土矿物上的氧化铁可以在波动的氧化还原环境中介导电子转移，赤铁矿的形成可能会影响随后的蚀变过程，包括微生物活动。质量平衡计算表明，在这些条件下，形成高达6%的无定形SiO2，可能会限制进一步的反应进展。
{"title":"Hematite neocrystallisation derived from the experimental alteration of montmorillonite in NaCl solution","authors":"Ritwick Sudheer Kumar, Laurence N. Warr, Balu R. Thombare, Tobias Manzel, Georg H. Grathoff","doi":"10.1016/j.clay.2025.108008","DOIUrl":"10.1016/j.clay.2025.108008","url":null,"abstract":"<div><div>Smectite-rich bentonites are widely used as engineered barriers, and consequently, their stability and alteration behaviour have been extensively studied. Small hematite crystals frequently form during the alteration of bentonite under oxidising conditions; however, the mechanism of Fe<sub>2</sub>O<sub>3</sub> formation remains poorly understood, especially its relationship to smectite alteration. This study presents mineralogical and geochemical analyses of hematite neocrystallisation from the experimental alteration of a purified montmorillonite fraction isolated from a Bavarian bentonite. Experiments were conducted in eight batch reactors containing monomineralic Na-saturated montmorillonite and a 0.1 M NaCl solution, at temperatures ranging from 160 to 220 °C and durations of 1–5 months, while other parameters were kept constant. Hematite crystallisation and smectite alteration mechanisms were investigated using transmission electron microscopy, X-ray diffraction and solution chemistry analyses. Results indicate that Fe ions released from partial dissolution (up to 7 wt%) of montmorillonite were mobilised and incorporated into neocrystallised hematite, producing log-normal crystal size distributions consistent with supply-controlled ripening mechanisms of crystal growth in a closed system. Time-dependent data indicate hematite growth is kinetically supply-controlled and self-limiting in low-Fe smectites, suggesting minimal long-term impact on engineered barrier performance. As iron oxides on clay minerals can mediate electron transfer in fluctuating redox environments, hematite formation may influence subsequent alteration processes, including microbial activity. Mass balance calculations suggest the formation of up to 6 % amorphous SiO<sub>2</sub>, potentially limiting further reaction progress under these conditions.</div></div>","PeriodicalId":245,"journal":{"name":"Applied Clay Science","volume":"279 ","pages":"Article 108008"},"PeriodicalIF":5.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145360839","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-11-20DOI: 10.1016/j.clay.2025.108033
Ernesto Adler Licursi , Luiz Carlos Bertolino , Francisco José da Silva
With the continued advancement of nanotechnology and emergence of new applications, the number of publications directly related to technological uses involving halloysite has shown an exponential growth over the years. However, despite the overall increase, the number of publications dedicated to the geological/mineralogical characterization of halloysite has not expanded proportionally. In this context, new researches focusing on mineral exploration, ore processing, identification of occurrences, and mineralogical/technological characterization should be developed to meet the growing demand of material suitable for novel applications. This study aims to characterize the mineralogy associated with new halloysitic kaolin occurrences in the region of Barra do Piraí and surroundings, state of Rio de Janeiro. X-ray diffraction (XRD) patterns of the raw and < 20 μm fractions were used to identify and quantify the major mineral phases, while the diffraction patterns of the clay fractions enabled the differentiation between kaolinite and halloysite. X-ray fluorescence (XRF) was used not only to quantify the major oxides, but also to validate the quantification by the Rietveld method. Scanning electron microscopy (SEM) was performed to enhance the accuracy of the clay minerals identification. Six out of seven samples contain significant quantities of halloysite, while only one is composed essentially by kaolinite. The results suggest that there is a strong potential for halloysite mineral exploration in this specific region of southeastern Brazil, opening up the possibility of delimiting sufficient volumes compatible with the new demands of emerging applications.
{"title":"Unravelling and characterizing new halloysitic kaolin occurrences from the Barra do Piraí, Rio de Janeiro, southeastern Brazil.","authors":"Ernesto Adler Licursi , Luiz Carlos Bertolino , Francisco José da Silva","doi":"10.1016/j.clay.2025.108033","DOIUrl":"10.1016/j.clay.2025.108033","url":null,"abstract":"<div><div>With the continued advancement of nanotechnology and emergence of new applications, the number of publications directly related to technological uses involving halloysite has shown an exponential growth over the years. However, despite the overall increase, the number of publications dedicated to the geological/mineralogical characterization of halloysite has not expanded proportionally. In this context, new researches focusing on mineral exploration, ore processing, identification of occurrences, and mineralogical/technological characterization should be developed to meet the growing demand of material suitable for novel applications. This study aims to characterize the mineralogy associated with new halloysitic kaolin occurrences in the region of Barra do Piraí and surroundings, state of Rio de Janeiro. X-ray diffraction (XRD) patterns of the raw and < 20 μm fractions were used to identify and quantify the major mineral phases, while the diffraction patterns of the clay fractions enabled the differentiation between kaolinite and halloysite. X-ray fluorescence (XRF) was used not only to quantify the major oxides, but also to validate the quantification by the Rietveld method. Scanning electron microscopy (SEM) was performed to enhance the accuracy of the clay minerals identification. Six out of seven samples contain significant quantities of halloysite, while only one is composed essentially by kaolinite. The results suggest that there is a strong potential for halloysite mineral exploration in this specific region of southeastern Brazil, opening up the possibility of delimiting sufficient volumes compatible with the new demands of emerging applications.</div></div>","PeriodicalId":245,"journal":{"name":"Applied Clay Science","volume":"279 ","pages":"Article 108033"},"PeriodicalIF":5.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145576432","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-10-21DOI: 10.1016/j.clay.2025.108016
Beril Tanc Kaya , Rabia Bozbay , Nermin Orakdogen
A series of clay-based cationic hybrids from N,N-dimethylaminoethyl methacrylate and 2-acrylamido-2-methyl-1-propanesulfonic acid in the presence of various clays; montmorillonite (Mt), bentonite (Bnt), sepiolite (Sep), kaolin and mica was prepared by in-situ free-radical polymerization. The primary objective was to understand the macroscale properties of ionically modified (alkyl)methacrylate-based polymers reinforced with nanometer-sized clays. Water absorption, repeated on-off switching in salt solutions, elasticity and efficiency in removal of anionic indigo carmine (IC) dye, widely used in textile industry for denim production, were comparatively analyzed depending on the clay type. Compared to Sep and Mt-integrated hybrids, the mechanical property was weaker due to the inhomogeneous distribution in the structure, while the mica and kaolin-integrated gels were resistant to high compression. Mt- and Sep-addition increased the swelling by four-fold, while the swelling in the presence of mica was limited. Hybrids exhibited good salt resistance and pH-sensitive swelling, with largest change in the volume being observed in Mt-doped gels, while least change was in Kaolin-doped ones. Based on the effect of salinity, the swelling of hybrids in aqueous solutions of monovalent and divalent metal nitrates followed the decreasing order as KNO3 > NaNO3 > Ba(NO3)2. Regardless of clay type, hybrid cryogels prepared at low polymerization temperature followed Fickian diffusion, while at higher temperatures, the clay type altered the mechanism and non-Fickian diffusion was observed in hybrid hydrogels doped with Mt, kaolin and mica. Anionic IC adsorption, which reached equilibrium in 30 min, varied between 93.4 % and 97.6 %. The presence of Kaolin and Bnt caused a significant increase in adsorption, while a decrease was observed in presence of Sep. Adsorption isotherms determined by three parameter models were compared with two-parameter models in linear and non-linear fitting of equilibrium data; Freundlich isotherm model and pseudo-first order kinetic model had the best fitness. Comparative results demonstrated that clay-integrated (alkyl)methacrylate-based cationic hybrids can be employed as effective and economical adsorbents for removal of anionic dyes from aqueous environments.
{"title":"Mechanistic insights for (alkyl)methacrylate-based cationic hybrid gels reinforced with sepiolite, montmorillonite, mica, bentonite and kaolin: A comparative thermodynamic study with all-in-one formulations","authors":"Beril Tanc Kaya , Rabia Bozbay , Nermin Orakdogen","doi":"10.1016/j.clay.2025.108016","DOIUrl":"10.1016/j.clay.2025.108016","url":null,"abstract":"<div><div>A series of clay-based cationic hybrids from <em>N</em>,<em>N</em>-dimethylaminoethyl methacrylate and 2-acrylamido-2-methyl-1-propanesulfonic acid in the presence of various clays; montmorillonite (Mt), bentonite (Bnt), sepiolite (Sep), kaolin and mica was prepared by in-situ free-radical polymerization. The primary objective was to understand the macroscale properties of ionically modified (alkyl)methacrylate-based polymers reinforced with nanometer-sized clays. Water absorption, repeated on-off switching in salt solutions, elasticity and efficiency in removal of anionic indigo carmine (IC) dye, widely used in textile industry for denim production, were comparatively analyzed depending on the clay type. Compared to Sep and Mt-integrated hybrids, the mechanical property was weaker due to the inhomogeneous distribution in the structure, while the mica and kaolin-integrated gels were resistant to high compression. Mt- and Sep-addition increased the swelling by four-fold, while the swelling in the presence of mica was limited. Hybrids exhibited good salt resistance and pH-sensitive swelling, with largest change in the volume being observed in Mt-doped gels, while least change was in Kaolin-doped ones. Based on the effect of salinity, the swelling of hybrids in aqueous solutions of monovalent and divalent metal nitrates followed the decreasing order as KNO<sub>3</sub> > NaNO<sub>3</sub> > Ba(NO<sub>3</sub>)<sub>2</sub>. Regardless of clay type, hybrid cryogels prepared at low polymerization temperature followed Fickian diffusion, while at higher temperatures, the clay type altered the mechanism and non-Fickian diffusion was observed in hybrid hydrogels doped with Mt, kaolin and mica. Anionic IC adsorption, which reached equilibrium in 30 min, varied between 93.4 % and 97.6 %. The presence of Kaolin and Bnt caused a significant increase in adsorption, while a decrease was observed in presence of Sep. Adsorption isotherms determined by three parameter models were compared with two-parameter models in linear and non-linear fitting of equilibrium data; Freundlich isotherm model and pseudo-first order kinetic model had the best fitness. Comparative results demonstrated that clay-integrated (alkyl)methacrylate-based cationic hybrids can be employed as effective and economical adsorbents for removal of anionic dyes from aqueous environments.</div></div>","PeriodicalId":245,"journal":{"name":"Applied Clay Science","volume":"279 ","pages":"Article 108016"},"PeriodicalIF":5.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145327140","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-11-15DOI: 10.1016/j.clay.2025.108048
Mayen J. Geu, Yan Zhuge, Xing Ma, Thong M. Pham
The growing emphasis on environmental sustainability has significantly boosted research into metakaolin (MK)-based concrete as a viable alternative to traditional cement. The incorporation of MK enhances the mechanical and microstructural properties of concrete. Furthermore, it improves specific durability aspects, including chloride resistance, reduced permeability, and increased resistance to acid and alkali attacks. The overall enhancements arise from the small particle size's fill effect, improving packing density, and the pozzolanic reaction that produces additional gels, resulting in stronger and more durable concrete. However, the literature reveals mixed results concerning other durability factors, particularly carbonation resistance, water absorption, and shrinkage behaviour. Previous studies have indicated that a 10 % replacement reduced carbonation depth, and a 15 % MK dosage decreased capillary water absorption. In contrast, other investigations have highlighted potential drawbacks, including an increase in carbonation depth at 10–15 % MK replacement, a substantial dry shrinkage beyond 15 %, and greater water absorption at higher replacement levels. This review paper identifies and outlines research gaps in understanding how the structure of raw kaolinite influences its pozzolanic reactivity, mechanical performance, and durability properties in green concrete. The review paper consolidates key research findings on metakaolin, highlighting its durability properties as a partial replacement for cement, with an optimal level of 10–15 % MK in concrete.
{"title":"Systematic review of physical, mechanical and durability performances of metakaolin concrete","authors":"Mayen J. Geu, Yan Zhuge, Xing Ma, Thong M. Pham","doi":"10.1016/j.clay.2025.108048","DOIUrl":"10.1016/j.clay.2025.108048","url":null,"abstract":"<div><div>The growing emphasis on environmental sustainability has significantly boosted research into metakaolin (MK)-based concrete as a viable alternative to traditional cement. The incorporation of MK enhances the mechanical and microstructural properties of concrete. Furthermore, it improves specific durability aspects, including chloride resistance, reduced permeability, and increased resistance to acid and alkali attacks. The overall enhancements arise from the small particle size's fill effect, improving packing density, and the pozzolanic reaction that produces additional gels, resulting in stronger and more durable concrete. However, the literature reveals mixed results concerning other durability factors, particularly carbonation resistance, water absorption, and shrinkage behaviour. Previous studies have indicated that a 10 % replacement reduced carbonation depth, and a 15 % MK dosage decreased capillary water absorption. In contrast, other investigations have highlighted potential drawbacks, including an increase in carbonation depth at 10–15 % MK replacement, a substantial dry shrinkage beyond 15 %, and greater water absorption at higher replacement levels. This review paper identifies and outlines research gaps in understanding how the structure of raw kaolinite influences its pozzolanic reactivity, mechanical performance, and durability properties in green concrete. The review paper consolidates key research findings on metakaolin, highlighting its durability properties as a partial replacement for cement, with an optimal level of 10–15 % MK in concrete.</div></div>","PeriodicalId":245,"journal":{"name":"Applied Clay Science","volume":"279 ","pages":"Article 108048"},"PeriodicalIF":5.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145526145","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-10-23DOI: 10.1016/j.clay.2025.108023
Jakub Matusik , Klaudia Dziewiątka , Youjun Deng
This study investigated the efficiency of modified smectites for zearalenone (ZEN) removal, with a focus on the role of structural characteristics and surface chemistry. Cation exchange and/or calcination yielded poor performance (<10% removal). In contrast, organic functionalization with amphiphilic molecules, significantly enhanced ZEN adsorption by interlayer expansion and increased hydrophobicity. Among the tested modifiers, hexadecyltrimethylammonium bromide (C16) exhibited the highest removal efficiency (∼85%; 0.1 ppm ZEN, 200 mg/L dosage), driven by high organic loading correlated with smectites' cation exchange capacity. The C16-modified smectites had hydrophobic domains containing neutral C16 molecules, which resulted in optimal structural conditions for ZEN uptake. The smectites modified with ethyl lauroyl arginate (LAE®) and cocamidopropyl betaine (CAPB) demonstrated lower ZEN removal (∼70% and ∼60%, respectively), limited by lower organic loading caused by functional groups of modifiers. Vitamin B1-functionalization showed high efficiency for Na-rich smectite (47.6±0.6%) due to efficient Na+ to B1 exchange and thus enhanced surface hydrophobization. All modified materials retained high performance under acidic conditions, while alkaline pH reduced efficiency, except for the C16-modified materials. Adsorption kinetics were rapid and independent of the temperature (18°C and 37°C), though the C16 materials showed slower uptake due to colloidal stability issues. Linear adsorption isotherms followed the Freundlich model, supporting a partitioning mechanism. The C16- and B1-modified smectites were resistant to competitive pepsin interactions in simulated gastric fluid, unlike the LAE® and CAPB. These findings emphasize the importance of appropriate functionalization of smectites for ZEN adsorption and support the development of adsorbents for mycotoxin mitigation in animal feed.
{"title":"Smectite functionalization for targeted zearalenone immobilization: Investigating the key role of surface chemistry and adsorption mechanisms","authors":"Jakub Matusik , Klaudia Dziewiątka , Youjun Deng","doi":"10.1016/j.clay.2025.108023","DOIUrl":"10.1016/j.clay.2025.108023","url":null,"abstract":"<div><div>This study investigated the efficiency of modified smectites for zearalenone (ZEN) removal, with a focus on the role of structural characteristics and surface chemistry. Cation exchange and/or calcination yielded poor performance (<10% removal). In contrast, organic functionalization with amphiphilic molecules, significantly enhanced ZEN adsorption by interlayer expansion and increased hydrophobicity. Among the tested modifiers, hexadecyltrimethylammonium bromide (C16) exhibited the highest removal efficiency (∼85%; 0.1 ppm ZEN, 200 mg/L dosage), driven by high organic loading correlated with smectites' cation exchange capacity. The C16-modified smectites had hydrophobic domains containing neutral C16 molecules, which resulted in optimal structural conditions for ZEN uptake. The smectites modified with ethyl lauroyl arginate (LAE®) and cocamidopropyl betaine (CAPB) demonstrated lower ZEN removal (∼70% and ∼60%, respectively), limited by lower organic loading caused by functional groups of modifiers. Vitamin B1-functionalization showed high efficiency for Na-rich smectite (47.6±0.6%) due to efficient Na<sup>+</sup> to B1 exchange and thus enhanced surface hydrophobization. All modified materials retained high performance under acidic conditions, while alkaline pH reduced efficiency, except for the C16-modified materials. Adsorption kinetics were rapid and independent of the temperature (18°C and 37°C), though the C16 materials showed slower uptake due to colloidal stability issues. Linear adsorption isotherms followed the Freundlich model, supporting a partitioning mechanism. The C16- and B1-modified smectites were resistant to competitive pepsin interactions in simulated gastric fluid, unlike the LAE® and CAPB. These findings emphasize the importance of appropriate functionalization of smectites for ZEN adsorption and support the development of adsorbents for mycotoxin mitigation in animal feed.</div></div>","PeriodicalId":245,"journal":{"name":"Applied Clay Science","volume":"279 ","pages":"Article 108023"},"PeriodicalIF":5.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145360840","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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