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Application and Modification of Clay Minerals
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Application and Modification of Clay Minerals

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: 20 June 2025 | Viewed by 8643

Special Issue Editor

Dr. Gang Yang

E-Mail Website
Guest Editor
College of Resources and Environment & Chongqing Key Laboratory of Soil Multi-scale Interfacial Process, Southwest University, Chongqing 400715, China
Interests: interfacial adsorption and reaction; catalysis; clay minerals

Special Issue Information

Dear Colleagues,

Clay minerals are a group of minerals that are ubiquitously found in soils, sediments, and rocks. Natural clay minerals are scavengers for heavy metals and organic contaminants, and catalysts for reactions such as the degradation of organic contaminants, oil and gas formation, and the condensation of amino acids. Modification and oriented synthesis broaden the applications of clay minerals and also enhance their adsorption and catalytic performances. Overall, clay minerals have a wide range of applications and can be modified to suit specific needs in various engineering and industrial processes. Their unique properties make them valuable materials for a variety of purposes.

This Special Issue of the journal Materials, entitled “Application and Modification of Clay Minerals”, focuses on recent advances in the application of modified and synthesized clay minerals in environmental, catalytic, engineering, pharmaceutical and other fields. As the Guest Editor of this Special Issue, I am inviting you to contribute your work on clay mineral materials to this Special Issue, whose scope includes, but is not limited to, the following topics: the modification/synthesis of clay mineral materials, and the adsorption/catalysis/characterization of clay mineral materials.

Your contributions are highly appreciated.

Dr. Gang Yang
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • adsorption
  • catalysis
  • characterization
  • modeling
  • modification
  • synthesis

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Published Papers (10 papers)

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Research

15 pages, 6603 KiB  
Article
Contribution of Active Surface of NiFe-Layered Double Hydroxide on the Removal of Methyl Orange
by Yanping Zhao, Fengzhu Lv, Yanwen Ou, Guocheng Lv and Shifeng Zhao
Materials 2025, 18(4), 911; https://doi.org/10.3390/ma18040911 - 19 Feb 2025
Abstract
Layered double hydroxides (LDHs) have potential applications for pollutant removal. Enhancing their pollutant removal ability by fully utilizing the synergistic effects of physical adsorption and chemical catalysis has received widespread attention. In this study, a high methyl orange (MO) removal capacity was achieved [...] Read more.
Layered double hydroxides (LDHs) have potential applications for pollutant removal. Enhancing their pollutant removal ability by fully utilizing the synergistic effects of physical adsorption and chemical catalysis has received widespread attention. In this study, a high methyl orange (MO) removal capacity was achieved by utilizing the synergistic effects of physical adsorption and chemical catalysis of NiFe-LDH. wNiFe-LDH showed a significant removal amount of MO, up to 506.30 mg/g due to its reserving of the active surface to the largest extent. Experiment and molecular simulation clarified the high removal capacity derived from surface adsorption and the degradation ability of the active surface. The presence of more -OH groups on the surface enhanced the removal of MO, and the vacancies in the surface were beneficial for the formation of •O2− and contributed to the degradation of MO. As K2S2O8 was introduced, the removal rate of MO improved to 100% from 60.67%. However, a deeper study showed that the degradation was incomplete, as K2S2O8 inhibited the formation of •O2−, and the active species in the system changed to holes. The degradation path of MO was also altered. Thus, this study gives new insight into the reactivity of the active surface of NiFe-LDH and affords a new path to preserve the active surface. Full article
(This article belongs to the Special Issue Application and Modification of Clay Minerals)
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Figure 1

Figure 1
<p>(<b>a</b>) Preparation of four types of NiFe-LDH; (<b>b</b>) SEM image of wNiFe-LDH; (<b>c</b>) XRD patterns of wNiFe-LDH.</p> Full article ">Figure 2
<p>(<b>a</b>) Removal rate of MO (50 mg/L) by NiFe-LDH with different active surface areas; (<b>b</b>) removal rate of MO (50 mg/L) by wNiFe-LDH with differentNi/Fe molar ratios; and (<b>c</b>) removal rate under different pH conditions and initial MO concentrations.</p> Full article ">Figure 3
<p>(<b>a</b>) TGA curves of wNiFe-LDH and wNiFe-MO-50; (<b>b</b>) XRD patterns of wNiFe-LDH, wNiFe-MO-50, and w NiFe-MO-250; (<b>c</b>) in situ FTIR spectra of the MO solution; and (<b>d</b>) removal rate of MO under different quenching conditions.</p> Full article ">Figure 4
<p>Removal rate of MO at different pH for (<b>a</b>) wNiFe-LDH suspension and (<b>b</b>) wNiFe-LDH/MO mixture. Diagrams of wNiFe-LDH-MO with (<b>c</b>) Ni vacancy, (<b>d</b>) Fe vacancy, and (<b>e</b>) O vacancy (as shown in the position of the red circle) on the surface of wNiFe-LDH. Charge density of (<b>f</b>) NiFe-LDH with Vo, (<b>g</b>) Ni-Fe slice, and (<b>h</b>) Vo slice.</p> Full article ">Figure 5
<p>Illustration of the removal mechanism of MO (<b>a</b>) with wNiFe-LDH and (<b>b</b>) in the S-wNiFe-MO system.</p> Full article ">Figure 6
<p>(<b>a</b>) Removal rate of MO under different supplementary assistants; (<b>b</b>) influence of ingredient addition order on removal rate; (<b>c</b>) XRD pattern of wNiFe-LDH, S-MO-wNiFe, S-wNiFe-MO, and wNiFe-MO-S; and (<b>d</b>) free radical trapping results of S-wNiFe-MO.</p> Full article ">
24 pages, 9996 KiB  
Article
Relationships Between Physicochemical and Structural Properties of Commercial Vermiculites
by Ayoub Lahchich, Pedro Álvarez-Lloret, Javier F. Reynes and Celia Marcos
Materials 2025, 18(4), 831; https://doi.org/10.3390/ma18040831 - 14 Feb 2025
Abstract
This study examines the effects of thermal (1000 °C), hydrothermal (100 °C), mechanochemical (ambient T), and microwave (~100 °C) treatments on three types of Chinese vermiculites, one with lower potassium content than the others. The goal was to obtain materials with enhanced properties [...] Read more.
This study examines the effects of thermal (1000 °C), hydrothermal (100 °C), mechanochemical (ambient T), and microwave (~100 °C) treatments on three types of Chinese vermiculites, one with lower potassium content than the others. The goal was to obtain materials with enhanced properties related to specific surface areas. The response of the vermiculites to treatments and their physicochemical properties were analyzed using X-ray diffraction (XRD), thermal analysis (TG and DTG), and textural characterization via the BET method. XRD analyses showed similar mineral composition in treated and untreated samples, but the treatments affected the intensity and width of phase reflections, altering crystallinity and structural order, as well as the proportions of vermiculite, hydrobiotite, and phlogopite. Thermogravimetric analysis revealed two mass loss stages: water desorption (from 25 °C to about 250 °C) and recrystallization or dehydroxylation (above 800 °C). The isotherms indicated mesoporous characteristics, with hydrothermally CO2-treated samples having the highest specific surface area and adsorption capacity. The samples with vermiculite, hydrobiotite, and phlogopite generally showed moderate to high specific surface area (SBET) values, and mechanochemical treatments significantly increase SBET and pore volume (Vp) in the vermiculite and hydrobiotite samples. Crystallinity affects SBET, average Vp, and average pore size, and its monitoring is crucial to achieve the desired material characteristics, as higher crystallinity can reduce SBET but improve mechanical strength and thermal stability. This study highlights the influence of different treatments on vermiculite properties, providing valuable insights into their potential applications in various fields (such as thermal insulation in vehicles and aircraft, and the selective adsorption of gases and liquids in industrial processes, improving the strength and durability of building materials like cement and bricks). Full article
(This article belongs to the Special Issue Application and Modification of Clay Minerals)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Appearance of the investigated vermiculites in hand samples: (<b>a</b>) CHG, (<b>b</b>) CHS, and (<b>c</b>) CHGO.</p> Full article ">Figure 2
<p>Syrupy appearance of the CHG sample after hydrothermal treatment.</p> Full article ">Figure 3
<p>SEM image of the delaminated appearance of the CHGO sample after mechanochemical treatment.</p> Full article ">Figure 4
<p>XRD of the untreated and treated samples of CHG (<b>a</b>), CHS (<b>b</b>), and CHGO (<b>c</b>). Note: Vrm = vermiculite, PHl = phlogopite, Bt = biotite, and Hbt = hydrobiotite.</p> Full article ">Figure 4 Cont.
<p>XRD of the untreated and treated samples of CHG (<b>a</b>), CHS (<b>b</b>), and CHGO (<b>c</b>). Note: Vrm = vermiculite, PHl = phlogopite, Bt = biotite, and Hbt = hydrobiotite.</p> Full article ">Figure 5
<p>Curves of TG (<b>a</b>) and DTG (<b>b</b>) and SDTA (<b>c</b>) for the untreated and treated samples of CHG (heating rate of 10 °C/min and flowing oxygen at 50 mL/min). Note: 1—adsorbed surface water loss; 2—interlayer water loss and interlayer cation-bound water; 3–4—loss of hydroxyls; 5—decomposition of CO<sub>2</sub>; 6—recrystallization.</p> Full article ">Figure 5 Cont.
<p>Curves of TG (<b>a</b>) and DTG (<b>b</b>) and SDTA (<b>c</b>) for the untreated and treated samples of CHG (heating rate of 10 °C/min and flowing oxygen at 50 mL/min). Note: 1—adsorbed surface water loss; 2—interlayer water loss and interlayer cation-bound water; 3–4—loss of hydroxyls; 5—decomposition of CO<sub>2</sub>; 6—recrystallization.</p> Full article ">Figure 6
<p>Curves of TG (<b>a</b>) and DTG (<b>b</b>) and SDTA (<b>c</b>) for the untreated and treated samples of CHS (heating rate of 10 °C/min and flowing oxygen at 50 mL/min). Note: 1—adsorbed surface water loss; 2—interlayer water loss and interlayer cation-bound water; 3–4—loss of hydroxyls; 5—decomposition of CO<sub>2</sub>; 6—recrystallization.</p> Full article ">Figure 6 Cont.
<p>Curves of TG (<b>a</b>) and DTG (<b>b</b>) and SDTA (<b>c</b>) for the untreated and treated samples of CHS (heating rate of 10 °C/min and flowing oxygen at 50 mL/min). Note: 1—adsorbed surface water loss; 2—interlayer water loss and interlayer cation-bound water; 3–4—loss of hydroxyls; 5—decomposition of CO<sub>2</sub>; 6—recrystallization.</p> Full article ">Figure 7
<p>Curves of TG (<b>a</b>) and DTG (<b>b</b>) and SDTA (<b>c</b>) for the untreated and treated samples of CHGO (heating rate of 10 °C/min and flowing oxygen at 50 mL/min). Note: 1—adsorbed surface water loss; 2—interlayer water loss and interlayer cation-bound water; 3—loss of hydroxyls; 4—decomposition of CO<sub>2</sub>; 5—recrystallization.</p> Full article ">Figure 7 Cont.
<p>Curves of TG (<b>a</b>) and DTG (<b>b</b>) and SDTA (<b>c</b>) for the untreated and treated samples of CHGO (heating rate of 10 °C/min and flowing oxygen at 50 mL/min). Note: 1—adsorbed surface water loss; 2—interlayer water loss and interlayer cation-bound water; 3—loss of hydroxyls; 4—decomposition of CO<sub>2</sub>; 5—recrystallization.</p> Full article ">Figure 8
<p>Pore size vs. dV/dlog(w) graph: (<b>a</b>) CHG samples (* for CHG-AH, CHG-AH-CO<sub>2</sub>, and CHG-mq30), (<b>b</b>) CHS samples, (<b>c</b>) CHGO samples.</p> Full article ">Figure 8 Cont.
<p>Pore size vs. dV/dlog(w) graph: (<b>a</b>) CHG samples (* for CHG-AH, CHG-AH-CO<sub>2</sub>, and CHG-mq30), (<b>b</b>) CHS samples, (<b>c</b>) CHGO samples.</p> Full article ">Figure 9
<p>Relationships between mineral composition and S<sub>BET</sub> (<b>a</b>), mineral composition and average V<sub>p</sub> (<b>b</b>), and mineral composition and crystallinity (<b>c</b>); and the relationship between crystallinity and average pore size (<b>d</b>).</p> Full article ">Figure 9 Cont.
<p>Relationships between mineral composition and S<sub>BET</sub> (<b>a</b>), mineral composition and average V<sub>p</sub> (<b>b</b>), and mineral composition and crystallinity (<b>c</b>); and the relationship between crystallinity and average pore size (<b>d</b>).</p> Full article ">
17 pages, 6546 KiB  
Article
Catalytic Combustion of Biodiesel Wastewater on Red Mud Catalyst
by Shangzhi Yu, Wenyu Yuan, Qinglong Xie, Xiaojiang Liang and Yong Nie
Materials 2025, 18(3), 652; https://doi.org/10.3390/ma18030652 - 1 Feb 2025
Abstract
The resource utilization of red mud (RM) has attracted widespread attention for achieving the waste-to-waste treatment goal. In this work, the RM catalysts were synthesized at different calcination temperatures by a simple method. The calcination temperature had a great effect on catalyst activity [...] Read more.
The resource utilization of red mud (RM) has attracted widespread attention for achieving the waste-to-waste treatment goal. In this work, the RM catalysts were synthesized at different calcination temperatures by a simple method. The calcination temperature had a great effect on catalyst activity in the catalytic combustion of biodiesel wastewater. The RM catalyst calcined at 350 °C (RM350) exhibited the best catalytic activity. The chemical oxygen demand (COD) and COD removal rate of the treated wastewater reached almost 0 mg/L and 100%, respectively. The COD removal rate was significantly higher than 90.703% of the catalyst prepared by α-Fe2O3 at the same calcination temperature. Characterization results showed that the RM catalyst exhibited a high specific surface area of 60.03–64.15 m2/g and a well-developed mesoporous structure, as the calcination temperature did not exceed 400 °C, which was beneficial for adsorption and diffusion. Meanwhile, most of the Fe2O3 in the catalyst existed in an amorphous form and was abundantly presented on the catalyst surface, significantly lowering the reduction temperature of the catalyst and enhancing its reducibility. Furthermore, the α-Fe2O3 in the catalyst had higher dispersion, leading to an increase in utilization efficiency. Full article
(This article belongs to the Special Issue Application and Modification of Clay Minerals)
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Figure 1

Figure 1
<p>TG, DTG, and DSC curves of RM120.</p> Full article ">Figure 2
<p>XRD pattern of the as-prepared RM catalysts.</p> Full article ">Figure 3
<p>FTIR spectra of the as-prepared catalysts.</p> Full article ">Figure 4
<p>SEM images of fresh (<b>a</b>) RM120, (<b>b</b>) RM300, (<b>c</b>) RM350, (<b>d</b>) RM400, (<b>e</b>) RM500, (<b>f</b>) RM600, (<b>g</b>) RM700, (<b>h</b>) RM800, (<b>i</b>) RM900, (<b>j</b>) RM1000, (<b>k</b>) RM1100, and (<b>l</b>) Fe<sub>2</sub>O<sub>3</sub>-350.</p> Full article ">Figure 5
<p>(<b>a</b>) N<sub>2</sub> adsorption–desorption isotherms and (<b>b</b>) pore-size distribution curves of the as-prepared catalysts.</p> Full article ">Figure 6
<p>(<b>a</b>) Fe 2p and (<b>b</b>) O 1s XPS spectra of the as-prepared catalysts.</p> Full article ">Figure 7
<p>H<sub>2</sub>-TPR profiles of RM350 and Fe<sub>2</sub>O<sub>3</sub>-350.</p> Full article ">Figure 8
<p>The mechanical strength of (<b>a</b>) the catalyst at different calcination temperatures and (<b>b</b>) RM120, RM350, and Fe<sub>2</sub>O<sub>3</sub>-350 and the COD and COD removal rate of biodiesel wastewater after catalytic combustion.</p> Full article ">
12 pages, 7594 KiB  
Article
Hydrothermal Synthesis of Kaolinite Group Minerals
by Tatiana Koroleva, Boris Pokidko, Ivan Morozov, Anastasia Nesterenko, Sofya Kortunkova, Mikhail Chernov, Dmitry Ksenofontov and Victoria Krupskaya
Materials 2025, 18(3), 472; https://doi.org/10.3390/ma18030472 - 21 Jan 2025
Viewed by 306
Abstract
Synthetic alumosilicates are used in many industrial applications, and the synthesis of clay minerals under different conditions allows us to understand the conditions of their formation. This study examined the impact of varying silica precursors, pH conditions and synthesis durations. Synthetic kaolinite group [...] Read more.
Synthetic alumosilicates are used in many industrial applications, and the synthesis of clay minerals under different conditions allows us to understand the conditions of their formation. This study examined the impact of varying silica precursors, pH conditions and synthesis durations. Synthetic kaolinite group mineral analogues were investigated by X-ray diffraction, scanning electron microscopy and infrared spectroscopy. Additionally, the crystallinity index was calculated. The impact of using different silica sources on the structural features of synthetic kaolinite group analogues was revealed. The use of a Nanosil precursor resulted in the formation of highly crystalline kaolinite. The most significant alterations in the course of synthesis were observed at different pH values. The formation of various synthetic analogues of minerals from the kaolinite group was observed: at a high pH, the formation of halloysite with a small admixture of kaolinite was observed. Conversely, the synthesis resulted in the formation of ordered kaolinite at a low pH. The crystallinity index of the resulting synthesized kaolinite analogues rises as the synthesis duration increases, while the quantity of non-crystallized material decreases. The changes in the crystallinity of kaolinite when using different silica precursors are related to the different homogenization of the material that occurs at the stage of alumosilica gel formation. Full article
(This article belongs to the Special Issue Application and Modification of Clay Minerals)
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Figure 1

Figure 1
<p>Basic reactions leading to formation of aluminosilica gel using TEOS and aluminum nitrate [<a href="#B17-materials-18-00472" class="html-bibr">17</a>].</p> Full article ">Figure 2
<p>Scheme for aluminosilicate particle formation upon addition of aminosilane solution to acidic aluminum nitrate solution.</p> Full article ">Figure 3
<p>Scheme of first stage of kaolinite synthesis using different Si precursors.</p> Full article ">Figure 4
<p>XRD (<b>I</b>) and IR spectra (<b>II</b>) for synthesized analogues of kaolinite using different precursors —TEOS, Nanosil and aminosilicate (synthesis time of 5 days and temperature of 240 °C).</p> Full article ">Figure 5
<p>SEM micrographs for synthesized analogues of kaolinite group minerals using (<b>a</b>) TEOS, (<b>b</b>) Nanosil and (<b>c</b>) aminosilicate. (<b>d</b>) SEM and TEM micrographs of kaolinite-like spherical particles in aminosilicate are indicated by green arrows. The white arrow indicates from which particles the TEM was made.</p> Full article ">Figure 6
<p>XRD (<b>I</b>) and IR spectra (<b>II</b>) for synthesized analogues of kaolinite using Nanosil with different synthesis times—3, 5 and 7 days, and temperature of 240 °C.</p> Full article ">Figure 7
<p>XRD patterns (<b>I</b>) and IR spectra (<b>II</b>) for synthesized analogues of kaolinite using aminosilicate with different synthesis times—3, 5, 7 and 10 days, and temperature of 240 °C.</p> Full article ">Figure 8
<p>XRD patterns (<b>I</b>) and IR spectra (<b>II</b>) for synthesized analogues of kaolinite with different pH conditions—3.4, 6.6 and 10.8 (precursor—Nanosil, temperature—240 °C).</p> Full article ">Figure 9
<p>SEM micrographs for synthesized analogues of kaolinite group minerals using Nanosil precursor at different pHs: (<b>a</b>,<b>b</b>) 3.4, (<b>c</b>) 6.6 and (<b>d</b>) 10.8. Green lines indicate some of the intermicroaggregate pores.</p> Full article ">
13 pages, 5281 KiB  
Article
Preparation of Mesoporous Analcime/Sodalite Composite from Natural Jordanian Kaolin
by Muayad Esaifan, Fayiz Al Daboubi and Mohammed Khair Hourani
Materials 2024, 17(19), 4698; https://doi.org/10.3390/ma17194698 - 25 Sep 2024
Viewed by 753
Abstract
In this work, a meso-macroporous analcime/sodalite zeolite composite was produced by a hybrid synthesis process between a complex template method and hydrothermal treatment at 220 °C of naturally abundant kaolinitic-rich clay, using dodecyltrimethylammonium bromide as an organic soft template to enhance the mesoporous [...] Read more.
In this work, a meso-macroporous analcime/sodalite zeolite composite was produced by a hybrid synthesis process between a complex template method and hydrothermal treatment at 220 °C of naturally abundant kaolinitic-rich clay, using dodecyltrimethylammonium bromide as an organic soft template to enhance the mesoporous structure. The chemical and morphological properties of the developed zeolites composite were characterized using powder X-ray diffraction (PXRD), attenuated total Reflectance–Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA), N2 adsorption/desorption; and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) methods were used to study the morphology, chemical composition and structure of the product. Two types of zeolite particles were obtained:(1) hollow microsphere with an attached analcime icositetrahedron of 30–40 µm in size and (2) sodalite microsphere with a ball-like morphology of 3–4 µm in size. Both N2 adsorption/desorption and surface area data confirmed the high potentiality of the produced zeolite composite to act as an excellent adsorbent to remove inorganic pollutants such as Cu, Cd, Cr, Ni, Zn, and Pb ions, organic pollutants such as dyes, phenolic compounds, and surfactants from water; and their high catalytic activity, especially in the oxidation reaction of volatile organic compounds. The catalytic activity and adsorption ability of the produced analcime/sodalite composite will be tested experimentally in future work. Full article
(This article belongs to the Special Issue Application and Modification of Clay Minerals)
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Figure 1

Figure 1
<p>Geological map of the Baten El-Ghoul kaolinite deposit and sampling points.</p> Full article ">Figure 2
<p>Infrared spectra of the (<b>a</b>) kaolin starting material and (<b>b</b>) synthesized zeolites composite.</p> Full article ">Figure 3
<p>XRD diffractogram of thekaolinitic-rich clay (K: kaolinite, Q: quartz).</p> Full article ">Figure 4
<p>XRD diffractogram of the synthesized zeolites composite (S: sodalite, An: analcime, Q: quartz).</p> Full article ">Figure 5
<p>TGA and DTG curves of the (<b>a</b>) kaolinitic-rich clay and (<b>b</b>) synthesized zeolites composite.</p> Full article ">Figure 6
<p>SEM micrographs of (<b>a</b>) kaolinitic-rich clay, (<b>b</b>) synthesized zeolites composite with 1000× magnification, and (<b>c</b>) synthesized zeolites composite with 12,500× magnification.</p> Full article ">Figure 6 Cont.
<p>SEM micrographs of (<b>a</b>) kaolinitic-rich clay, (<b>b</b>) synthesized zeolites composite with 1000× magnification, and (<b>c</b>) synthesized zeolites composite with 12,500× magnification.</p> Full article ">Figure 7
<p>N<sub>2</sub> adsorption-desorption isotherms for the (<b>a</b>) kaolinitic-rich clayand (<b>b</b>) synthesized zeolites composite.</p> Full article ">Figure 8
<p>Pore size distribution curves, calculated using thedensity functional theory at STP for the (<b>a</b>) kaolinitic-rich clayand (<b>b</b>) synthesized zeolites composite.</p> Full article ">Figure 8 Cont.
<p>Pore size distribution curves, calculated using thedensity functional theory at STP for the (<b>a</b>) kaolinitic-rich clayand (<b>b</b>) synthesized zeolites composite.</p> Full article ">
19 pages, 8814 KiB  
Article
A Lab-Scale Evaluation of Parameters Influencing the Mechanical Activation of Kaolin Using the Design of Experiments
by Jofre Mañosa, Adrian Alvarez-Coscojuela, Alex Maldonado-Alameda and Josep Maria Chimenos
Materials 2024, 17(18), 4651; https://doi.org/10.3390/ma17184651 - 23 Sep 2024
Cited by 1 | Viewed by 1072
Abstract
This research investigates the mechanical activation of kaolin as a supplementary cementitious material at the laboratory scale, aiming to optimize milling parameters using the response surface methodology. The study evaluated the effects of rotation speed and milling time on the amorphous phase content, [...] Read more.
This research investigates the mechanical activation of kaolin as a supplementary cementitious material at the laboratory scale, aiming to optimize milling parameters using the response surface methodology. The study evaluated the effects of rotation speed and milling time on the amorphous phase content, the reduction in crystalline kaolinite, and impurity incorporation into the activated clay through the Rietveld method. The results demonstrated that adjusting milling parameters effectively enhanced clay activation, which is crucial for its use in low-carbon cements. High rotation speeds (300/350 rpm) and prolonged grinding times (90/120 min) in a planetary ball mill increased the pozzolanic activity by boosting the formation of amorphous phases from kaolinite and illite and reducing the particle size. However, the results evidenced that intermediate milling parameters are sufficient for reaching substantial degrees of amorphization and pozzolanic activity, avoiding the need for intensive grinding. Exceedingly aggressive milling introduced impurities like ZrO2 from the milling equipment wear, underscoring the need for a balanced approach to optimizing reactivity while minimizing impurities, energy consumption, and equipment wear. Achieving this balance is essential for efficient mechanical activation, ensuring the prepared clay’s suitability as supplementary cementitious materials without excessive costs or compromised equipment integrity. Full article
(This article belongs to the Special Issue Application and Modification of Clay Minerals)
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Figure 1

Figure 1
<p>Kaolinite layered structure.</p> Full article ">Figure 2
<p>X-ray powder diffractogram of K.</p> Full article ">Figure 3
<p>Face-centered central composite design with two variables.</p> Full article ">Figure 4
<p>Amorphous content (Y<sub>1</sub>) response: (<b>a</b>) contour plot and (<b>b</b>) 3D surface.</p> Full article ">Figure 5
<p>ZrO<sub>2</sub> impurity content (Y<sub>2</sub>) response: (<b>a</b>) contour plot and (<b>b</b>) 3D surface.</p> Full article ">Figure 6
<p>Kaolinite content (Y<sub>3</sub>) response: (<b>a</b>) contour plot and (<b>b</b>) 3D surface.</p> Full article ">Figure 7
<p>Secondary electron micrographs obtained via SEM of (<b>a</b>) K, (<b>b</b>) K250-60, and (<b>c</b>) K350-120.</p> Full article ">Figure 8
<p>(<b>a</b>) Particle size distribution and (<b>b</b>) specific surface area of K and representative DoE samples.</p> Full article ">Figure 9
<p>X-ray diffractograms of representative DoE samples: kaolinite (Kaol), illite (I), K-feldspar (K-F), quartz (Q), cubic zirconia (Zc), and monoclinic zirconia (Zm). *: zoomed region 27.5–35.0 2θ°.</p> Full article ">Figure 10
<p>Backscattered electron (BSE) micrographs obtained via SEM: (<b>a</b>) K, (<b>b</b>) 250-60, and (<b>c</b>) 350-120.</p> Full article ">Figure 11
<p>Energy-dispersive X-ray spectroscopy (EDS) analysis of K350-120 sample.</p> Full article ">Figure 12
<p>TGA (solid line) and DTG (dashed line) of representative DoE samples.</p> Full article ">Figure 13
<p>Modified Chapelle test for representative DoE samples and raw material.</p> Full article ">Figure 14
<p>R<sup>3</sup> test heat release for representative DoE samples.</p> Full article ">
22 pages, 14976 KiB  
Article
Effect of Chlorine Salt Content on the Microstructural Development of C-S-H Gels and Ca(OH)2 at Different Curing Temperatures
by Wenjie Qi, Zhisheng Fang, Shiyi Zhang, Yingfang Fan, Surendra P. Shah and Junjie Zheng
Materials 2024, 17(18), 4460; https://doi.org/10.3390/ma17184460 - 11 Sep 2024
Viewed by 715
Abstract
Freshwater resources are scarce in coastal areas, and using seawater as mixing water can alleviate the scarcity of freshwater resources. However, the presence of chloride ions in seawater affects the generation of hydration products and the durability of concrete structures. In order to [...] Read more.
Freshwater resources are scarce in coastal areas, and using seawater as mixing water can alleviate the scarcity of freshwater resources. However, the presence of chloride ions in seawater affects the generation of hydration products and the durability of concrete structures. In order to investigate the effect of hydrated calcium silicate (C-S-H) gel and calcium hydroxide (CH) generation in seawater-mixed cement pastes under 50 °C curing, their microscopic morphology was investigated using differential scanning calorimetry analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The relationship between the amount of C-S-H gel and CH production and the amount of chloride ion dosing, fly ash dosing, and the age of curing were investigated. The degree of influence between hydration products and influencing factors was analyzed using the grey correlation analysis. It was shown that 50 °C curing promoted the hydration reaction and generated more hydration products compared with ASTM standard. The content of C-S-H gel and CH increased with chloride dosage. The content of C-S-H gel increased by 13.5% under 50 °C curing compared with the control group at a chloride dosage of 1.3%. Fly ash is rich in active SiO2 and AI2O3, and other components, which can react with Ca(OH)2 generated by cement hydration and then generate C-S-H gel. With the increase of fly ash, the content of C-S-H gel also increases, but the CH content decreases. When 25% of fly ash was doped under 50 °C curing, the C-S-H gel content increased by 5.02% compared to the control group. The CH content decreased by 31.8% compared to the control group. With the growth of the maintenance age, the hydration reaction continues, the generation of C-S-H gel and CH will continue to increase, and their microstructures will become denser. C-S-H gel and CH content increased the most by raising the curing temperature at 7 days of curing, increasing by 10.11% and 22.62%, respectively. C-S-H gel and CH content had the highest gray relation with fly ash dosing. Chloride dosage and age of maintenance had the highest correlation with CH content at room temperature maintenance of 0.788 and 0.753, respectively. Full article
(This article belongs to the Special Issue Application and Modification of Clay Minerals)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Microscopic properties of experimental materials. (<b>a</b>) Cement (<b>b</b>) Fly ash.</p> Full article ">Figure 2
<p>Fabrication flow chart.</p> Full article ">Figure 3
<p>Effect of chloride ion concentration on the relative content of C-S-H gel.</p> Full article ">Figure 4
<p>Effect of chloride ion concentration on the heat-absorption decomposition peak of C-S-H gels.</p> Full article ">Figure 5
<p>SEM images of a hardened slurry of cementitious materials with different chloride dosages for 50 °C curing. (<b>a</b>) 0% (<b>b</b>) 0.5% (<b>c</b>) 1.3%.</p> Full article ">Figure 6
<p>SEM images of a hardened slurry of cementitious materials with different chloride dosages in standard curing. (<b>a</b>) 0% (<b>b</b>) 0.5% (<b>c</b>) 1.3%.</p> Full article ">Figure 7
<p>Effect of fly ash on the relative content of C-S-H gel.</p> Full article ">Figure 8
<p>Effect of fly ash dosage on the heat-absorption decomposition peak of C-S-H gels.</p> Full article ">Figure 9
<p>SEM images of a hardened slurry of cementitious materials with different fly ash dosages in 50 °C curing. (<b>a</b>) 0% (<b>b</b>) 15% (<b>c</b>) 25%.</p> Full article ">Figure 10
<p>SEM images of a hardened slurry of cementitious materials with different fly ash dosages in standard curing. (<b>a</b>) 0% (<b>b</b>) 15% (<b>c</b>) 25%.</p> Full article ">Figure 11
<p>Effect of age of maintenance on the relative content of C-S-H gels.</p> Full article ">Figure 12
<p>Effect of curing age on endothermic decomposition peak of C-S-H gel.</p> Full article ">Figure 13
<p>SEM images of C-S-H gels at different curing ages at 50 °C curing. (<b>a</b>) 3 days (<b>b</b>) 7 days (<b>c</b>) 28 days.</p> Full article ">Figure 14
<p>SEM images of C-S-H gels at different curing ages in standard curing. (<b>a</b>) 3 days (<b>b</b>) 7 days (<b>c</b>) 28 days.</p> Full article ">Figure 15
<p>XRD analysis of the effect of chloride doping on CH generation: (<b>a</b>) 50 °C curing (<b>b</b>) Standard curing.</p> Full article ">Figure 16
<p>Effect of chloride ions on CH content.</p> Full article ">Figure 17
<p>Effect of chloride ion concentration on the heat-absorption decomposition peak of CH.</p> Full article ">Figure 18
<p>SEM images of a hardened slurry of cementitious materials with different chloride dosages in 50 °C curing. (<b>a</b>) 0% (<b>b</b>) 0.5% (<b>c</b>) 1.3%.</p> Full article ">Figure 19
<p>SEM images of hardened slurry of cementitious materials with different chloride dosages in standard curing. (<b>a</b>) 0% (<b>b</b>) 0.5% (<b>c</b>) 1.3%.</p> Full article ">Figure 20
<p>XRD plot of the effect of fly ash dosage on CH content. (<b>a</b>) 50 °C curing (<b>b</b>) Standard curing.</p> Full article ">Figure 21
<p>Effect of fly ash admixture on CH content.</p> Full article ">Figure 22
<p>Effect of fly ash content on endothermic decomposition peak of CH.</p> Full article ">Figure 23
<p>SEM images of a hardened slurry of cementitious materials with different fly ash dosages at 50 °C curing. (<b>a</b>) 0% (<b>b</b>) 15% (<b>c</b>) 25%.</p> Full article ">Figure 24
<p>SEM images of CH with different fly ash admixtures in standard curing. (<b>a</b>) 0% (<b>b</b>) 15% (<b>c</b>) 25%.</p> Full article ">Figure 25
<p>XRD plots of the effect of different age of curing on CH content. (<b>a</b>) 50 °C curing (<b>b</b>) Standard curing.</p> Full article ">Figure 26
<p>Effect of age of maintenance on CH content.</p> Full article ">Figure 27
<p>Effect of curing age on endothermic decomposition peak of CH.</p> Full article ">Figure 28
<p>SEM images of cementitious materials hardened slurry at different curing ages in 50 °C curing. (<b>a</b>) 3 days (<b>b</b>) 7 days (<b>c</b>) 28 days.</p> Full article ">Figure 29
<p>SEM images of cementitious materials hardened slurry at different curing ages in standard curing. (<b>a</b>) 3 days (<b>b</b>) 7 days (<b>c</b>) 28 days.</p> Full article ">Figure 30
<p>Gray correlation values of hydration products and influencing factors.</p> Full article ">
16 pages, 43800 KiB  
Article
Study on the Binding Behavior of Chloride Ion and Ettringite in Nano-Metakaolin Cement by Seawater Mixing and Curing Temperatures
by Zhisheng Fang, Shiyi Zhang, Wenjie Qi, Yingfang Fan, Surendra P. Shah and Junjie Zheng
Materials 2024, 17(16), 3943; https://doi.org/10.3390/ma17163943 - 8 Aug 2024
Cited by 1 | Viewed by 1337
Abstract
Mixing cement with seawater will cause the hydration process of cement to be different from that of ordinary cement, which will significantly affect cement’s mechanical properties and durability. This article investigates the effects of chloride ion concentration, curing temperature, and nano-metakaolin content on [...] Read more.
Mixing cement with seawater will cause the hydration process of cement to be different from that of ordinary cement, which will significantly affect cement’s mechanical properties and durability. This article investigates the effects of chloride ion concentration, curing temperature, and nano-metakaolin content on the evolution process of Friedel’s salts and ettringite (AFt) crystals in cement pastes. The study was conducted using X-ray diffraction (XRD), thermal analysis (TG), scanning electron microscopy (SEM), and mercury-intrusion porosimetry (MIP). The results show that chlorine salt can increase the production of Friedel’s salt and ettringite, and the delayed AFt production increases by up to 27.95% after the addition of chlorine salt, which has an adverse effect on cement-based materials. Increasing the curing temperature and increasing the nano-metakaolin dosage increased the generation of Friedel’s salt and decreased the delayed AFt generation, which resulted in a decrease in the length and diameter of the AFt crystals. After 28 days of high-temperature curing and the addition of nano-metakaolin, Friedel’s salt production increased by 13.40% and 14.34%, respectively, and ettringite production decreased by 9.68% and 7.93%, respectively. Increasing the curing temperature and adding nano-metakaolin can reduce the adverse effect of delayed ettringite increases due to chloride ion binding. Full article
(This article belongs to the Special Issue Application and Modification of Clay Minerals)
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Figure 1

Figure 1
<p>Microstructure of cement and NMK. (<b>a</b>) Cement, (<b>b</b>) NMK.</p> Full article ">Figure 2
<p>Schematic diagram of specimen production and experimental procedures.</p> Full article ">Figure 3
<p>XRD patterns of samples with different chloride content for standard curing.</p> Full article ">Figure 4
<p>TG curves of specimens with different chloride content for standard curing. (<b>a</b>) 3 days, (<b>b</b>) 28 days.</p> Full article ">Figure 5
<p>Friedel’s salt production with different chlorine content for standard curing.</p> Full article ">Figure 6
<p>Micromorphologies of Friedel’s salt and AFt with different chlorine content at 28 days. (<b>a</b>) NC3C0, (<b>b</b>) NC3C1, (<b>c</b>) NC3C2.</p> Full article ">Figure 7
<p>XRD patterns of samples (NC3C1) with different curing temperatures.</p> Full article ">Figure 8
<p>TG curves of specimen (NC3C1) with different curing temperatures. (<b>a</b>) 3 days, (<b>b</b>) 28 days.</p> Full article ">Figure 9
<p>Friedel’s salt production of specimen (NC3C1) with different curing temperatures.</p> Full article ">Figure 10
<p>Micromorphologies of Friedel’s salt and AFt with different curing temperature of specimen (NC3C1) at 28 days. (<b>a</b>) 5 °C, (<b>b</b>) 20 °C, (<b>c</b>) 50 °C.</p> Full article ">Figure 11
<p>XRD patterns of samples with different nano-metakaolin content for standard curing.</p> Full article ">Figure 12
<p>TG curves of specimens with different nano-metakaolin content for standard curing. (<b>a</b>) 3 days, (<b>b</b>) 28 days.</p> Full article ">Figure 13
<p>Friedel’s salt production with different nano-metakaolin content for standard curing.</p> Full article ">Figure 14
<p>Micromorphologies of Friedel’s salt and AFt with different nano-metakaolin content at 28 days. (<b>a</b>) NC0C1, (<b>b</b>) NC3C1, (<b>c</b>) NC5C1.</p> Full article ">
12 pages, 24112 KiB  
Article
A Novel Approach for Preparing Sepiolite Micron Powder Based on Steam Pressure Changes
by Wenjia Yang, Youhang Zhou, Jialin Song, Yuze Li and Tianyu Gong
Materials 2024, 17(14), 3574; https://doi.org/10.3390/ma17143574 - 19 Jul 2024
Viewed by 770
Abstract
As a common method for preparing micron powder in industrial operations, the mechanical extrusion method simply pursues the particle size without considering the microstructure characteristics of sepiolite, which leads to problems such as bundles of sepiolite not being effectively dispersed, and thus the [...] Read more.
As a common method for preparing micron powder in industrial operations, the mechanical extrusion method simply pursues the particle size without considering the microstructure characteristics of sepiolite, which leads to problems such as bundles of sepiolite not being effectively dispersed, and thus the disruption of fibers is inevitably caused. In this work, a new micronization method for disaggregating these bundles while preserving the original structural integrity of the fibers is proposed based on steam pressure changes. The effects of steam pressure changes on the particle size distribution, microstructure, and properties of treated sepiolite are studied using X-ray fluorescence spectrometer (XRF), X-ray diffractometer (XRD), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM), and a specific surface area and aperture analyzer (BET). The experimental results show that the particle size of sepiolite powder depends greatly on steam pressure, and sepiolite powder with mass ratio of 91.6% and a particle size D97 of 21.27 μm is obtained at a steam pressure of 0.6 MPa. Compared to the sepiolite after mechanical extrusion, the sepiolite treated with steam pressure changes can maintain the integrity of its crystalline structure. The specific surface area of sepiolite enhanced from 80.15 m2 g−1 to 141.63 m2 g−1 as the steam pressure increased from 0.1 to 0.6 MPa, which is about 1.6 times that of the sample treated with mechanical extrusion. Full article
(This article belongs to the Special Issue Application and Modification of Clay Minerals)
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Figure 1
<p>Sepiolite sample.</p> Full article ">Figure 2
<p>Experimental platform.</p> Full article ">Figure 3
<p>The principle of preparing sepiolite powder using this method: (<b>a</b>) Steam injection. (<b>b</b>) Steam release.</p> Full article ">Figure 4
<p>Distribution of the proportions of mass among the samples.</p> Full article ">Figure 5
<p>Particle size distribution results: (<b>a</b>) Particle size distribution of samples treated with steam (≤210 μm). (<b>b</b>) Cumulative particle size distribution of all samples.</p> Full article ">Figure 6
<p>SEM images of samples: (<b>a</b>) SEP-0.1, (<b>b</b>) SEP-0.2, (<b>c</b>) SEP-0.3, (<b>d</b>) SEP-0.4, (<b>e</b>) SEP-0.5, (<b>f</b>) SEP-0.6, (<b>g</b>) SEP-ext.</p> Full article ">Figure 7
<p>TEM images of samples: (<b>a</b>) SEP-0.4, (<b>b</b>) SEP-0.5, (<b>c</b>) SEP-0.6, (<b>d</b>) SEP-ext.</p> Full article ">Figure 8
<p>XRD patterns of the samples.</p> Full article ">Figure 9
<p>N<sub>2</sub> adsorption–desorption isotherms of the samples.</p> Full article ">
16 pages, 5682 KiB  
Article
Synthesis of Low-Silicon X-Type Zeolite from Lithium Slag and Its Fast Exchange Performance of Calcium and Magnesium Ions
by Yu Wang, Longbin Deng, Lin Zhang, Qun Cui and Haiyan Wang
Materials 2024, 17(13), 3181; https://doi.org/10.3390/ma17133181 - 28 Jun 2024
Cited by 2 | Viewed by 1235
Abstract
Without the addition of silicon and aluminum sources, a pure-phase KNaLSX zeolite was successfully synthesized from the residue (lithium slag), which was produced from spodumene in the production process of lithium carbonate. The KNaLSX samples were characterized by an X-ray Diffractometer (XRD), Scanning [...] Read more.
Without the addition of silicon and aluminum sources, a pure-phase KNaLSX zeolite was successfully synthesized from the residue (lithium slag), which was produced from spodumene in the production process of lithium carbonate. The KNaLSX samples were characterized by an X-ray Diffractometer (XRD), Scanning Electron Microscope (SEM), X-ray Fluorescence Spectrometer (XRF), Thermogravimetric Differential Thermal Analysis (TG-DTA), Fourier Transform Infrared Spectrometer (FT-IR), and N2 adsorption measurement. The ion exchange capacity and the ion exchange rate of calcium and magnesium ions were measured as used for a detergent builder, and the results were compared with the standard zeolites (KNaLSX and 4A). The experimental results show that the pure-phase KNaLSX synthSynthesis and characterization of co-crystalline zeolite composite of LSX/esized from lithium slag has a SiO2/Al2O3 ratio of 2.01 with a grain size of 3~4 μm, which is close to the commercial KNaLSX sample of a SiO2/Al2O3 ratio of 2.0. The BET-specific surface area of KNaLSX is 715 m2/g, which is larger than the low-silicon X-type zeolite (LSX) synthesized from waste residue reported in the literature. The ion exchange rate constant of calcium and magnesium ions in KNaLSX is 5 times and 3 times that of 4A zeolite, respectively. KNaLSX also has a high ion exchange capacity for magnesium ion of 191 mgMgCO3/g, which is 2 times than that of 4A zeolite, and a high ion exchange capacity for calcium ion of 302 mgCaCO3/g, which meets the first-grade standard of zeolite for detergent builders in China. The work provides the basis for high-value resource utilization of lithium slag and the development of a detergent builder for rapid washing. Full article
(This article belongs to the Special Issue Application and Modification of Clay Minerals)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>The diagram of the hydrothermal synthesis process of KNaLSX zeolite from lithium slag.</p> Full article ">Figure 2
<p>Synthetic samples at different potassium/alkali ratios: (<b>a</b>) XRD patterns and (<b>b</b>) relative crystallinity.</p> Full article ">Figure 3
<p>Synthetic samples at different crystallization temperatures: (<b>a</b>) XRD patterns and (<b>b</b>) relative crystallinity.</p> Full article ">Figure 4
<p>Synthetic samples at different crystallization times: (<b>a</b>) XRD patterns and (<b>b</b>) relative crystallinity.</p> Full article ">Figure 5
<p>SEM images of (<b>a</b>) KNaLSX and (<b>b</b>) KNaLSX-C.</p> Full article ">Figure 6
<p>TG-DTA curves of (<b>a</b>) KNaLSX and (<b>b</b>) KNaLSX-C.</p> Full article ">Figure 7
<p>N<sub>2</sub> adsorption/desorption isotherms of KNaLSX and KNaLSX-C.</p> Full article ">Figure 8
<p>Pore size distribution of KNaLSX and KNaLSX-C calculated by the NLDFT method.</p> Full article ">Figure 9
<p>(<b>a</b>) Calcium ion and (<b>b</b>) magnesium ion exchange rate curves of the zeolites and their kinetic model fitting.</p> Full article ">Figure 10
<p>The ion exchange rate curves and kinetic model fitting of the mixed solution of calcium and magnesium ions by (<b>a</b>) KNaLSX, (<b>b</b>) KNaLSX-C, and (<b>c</b>) 4A zeolites.</p> Full article ">
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: evolution of nontronite toward serpentines: possible implications for terrestrial and extraterrestrial samples
Authors: Isabella Pignatelli, Enrico Mugnaioli, Mustapha Abdelmoula
Affiliation: Université de Lorraine, Nancy, France

Title: Relationship between physico-chemical and structural properties of commercial vermiculites
Authors: Ayoub Lahchich; Pedro Álvarez-Lloret; Javier F. Reynes; Celia Marcos
Affiliation: Dpto. Geología, Facultad de Geología, Universidad de Oviedo
Abstract: This study examines the effects of thermal, hydrothermal, mechanochemical, and micro-wave treatments on three types of Chinese vermiculites, one with lower potassium content than the others. The goal was to obtain materials with enhanced properties related to spe-cific surface areas. The response of the vermiculites to treatments and their physicochem-ical properties were analyzed using X-ray diffraction (XRD), thermal analysis (TG and DTG), and textural characterization via the BET method. XRD analyses showed similar mineral composition in treated and untreated samples, but treatments affected the inten-sity and width of phase reflections, altering crystallinity and structural order, and the proportions of vermiculite, hydrobiotite, and phlogopite. Thermogravimetric analysis re-vealed two mass loss stages: water desorption and recrystallization or dehydroxylation. The isotherms indicated mesoporous characteristics, with hydrothermally CO2-treated samples having the highest specific surface area and adsorption capacity. Samples with vermiculite, hydrobiotite, and phlogopite generally show moderate to high specific surface area (SBET) values, and mechanochemical treatments significantly increase SBET and pore volume (Vp) in vermiculite and hydrobiotite samples. Crystallinity affects SBET, average Vp, and average pore size, and its monitoring is crucial to achieve desired material character-istics, as higher crystallinity can reduce SBET but improve mechanical strength and ther-mal stability. This study highlights the influence of different treatments on vermiculite properties, providing valuable insights into their potential applications in various fields.

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