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Organo-Clays: Preparation, Characterization and Applications

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A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Clays and Engineered Mineral Materials".

Deadline for manuscript submissions: closed (30 September 2025) | Viewed by 9758

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Prof. Dr. Francisco Rolando Valenzuela-Díaz

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Departamento de Engenharia Metalúrgica e de Materiais da Escola Politécnica, Universidade de São Paulo, Sao Paulo 05508-030, Brazil
Interests: clay science and technology
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Dr. Antonio Kieling

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Department of Mechanical Engineering, State University of Amazonas, Manaus 69850-020, Brazil
Interests: clay science and technology; composite materials

Dr. Jose Costa de Macedo Neto

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Departamento de Engenharia de Materiais, Universidade do Estado do Amazonas (UEA), Manaus 69850-020, Brazil
Interests: polymer nanocomposites and metals

Special Issue Information

Dear Colleagues,

An enormous number of organo-clay complexes have been and are being studied. This is because clays are made up of very small elementary particles which have an anisometric morphology, chemically interesting surfaces and generally have the ability to exchange cations or anions, allowing for the intercalation or incorporation of organic substances. The most studied types of clays have been kaolin, halloysite, other tubular clays, bentonite and anionic clays like lamellar double hydroxides. This Special Issue will focus on the preparation, characterization and application of organo-clays that include both the consolidated applications of organo-clays, such as organophilic clays in the drilling of oil wells, in the paint industry and in cosmetics and toiletries, as well as in more modern applications such as the incorporation of organic substances in water treatment, controlled drug release, fertilizers, herbicides, etc., nanofillers in polymers’ nanocomposites, and also the emerging study of organo-synthetic clays.

Prof. Dr. Francisco Rolando Valenzuela-Díaz
Dr. Antonio Kieling
Dr. Jose Costa de Macedo Neto
Guest Editors

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Keywords

organo-clays
the preparation of organo-clays
the characterization of organo-clays
the uses of organo-clays
organo-bentonite
organo-kaolin

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Published Papers (8 papers)

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Research

27 pages, 7466 KB

Open AccessArticle

Purification Capacity of a Modified Montmorillonite on the Post-Consumption Vegetable Oil Recycling Process

by Christiano Gianesi Bastos Andrade, Caroline Tiemi Toda dos Santos, Victor Akira Murata Kussaba, Francisco Rolando Valenzuela Diaz and Samuel Marcio Toffoli

Minerals 2026, 16(4), 369; https://doi.org/10.3390/min16040369 - 31 Mar 2026

Viewed by 540

Abstract

Among the naturally abundant clays in the Earth’s crust, montmorillonite (MMT), a member of the smectite group, stands out for its versatility. Its interesting properties can be further improved by chemical processing with inorganic acids and reaction temperatures close to boiling. In this study, a Brazilian polycationic MMT was treated with a low-concentration (2M) aqueous solution of hydrochloric acid at 60 and 70 °C for 5 h. The resulting modified clay was then employed in the purification of post-consumption oil (PCO), specifically soybean oil. The effect of the modification variables of the clay and also the purification parameters (time and temperature) were investigated, comparing the adsorptive and purification capacities of the modified MMT with those of the natural and a commercial clay sample. The characterization of the MMT (raw and modified) was carried out by bulk density, moisture content, plasticity limit, BET, SEM/EDS, XRD, and FTIR, whereas the characterization of the PCO, as-received and after purification, involved the analyses of apparent density, relative flow time, UV-Vis spectrophotometry, and acid value. The results show that light acid activation, especially at 70 °C, promoted a significant increase in the surface area up to 96% and the adsorption capacity of the clay. The oil purification showed good results in all tests, with the best condition being 70 °C for 24 h with the C70 clay. Thus, the satisfactory results represent an economy of time and energy. Full article

(This article belongs to the Special Issue Organo-Clays: Preparation, Characterization and Applications)

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26 pages, 6076 KB

Open AccessArticle

Using TESPT to Improve the Performance of Kaolin in NR Compounds

by Michael Cezar Camargo, Abel Cardoso Gonzaga Neto, Samuel Marcio Toffoli and Ticiane Sanches Valera

Minerals 2026, 16(2), 149; https://doi.org/10.3390/min16020149 - 29 Jan 2026

Viewed by 661

Abstract

Kaolin is an abundant, low-cost filler for elastomeric compounds. The kaolin used here is primarily kaolinite, chemically clean, and contains a fine particle population. Although agglomeration is evident, it can be mitigated by appropriate physical processing and, when desired, by chemical coupling. This study evaluates kaolin in natural rubber (NR) and examines how adding bis(triethoxysilylpropyl) tetrasulfide (TESPT) during mixing affects filler–matrix compatibility, viscoelastic response, cure stability, and mechanical performance. Kaolin was structurally and morphologically characterized, and the compounds were prepared in a closed mixer coupled to a torque rheometer under controlled dispersion conditions. Part 1 assessed NR with kaolin without a coupling agent, and Part 2 assessed the NR–kaolin with TESPT added during mixing (0.5 and 5 phr). Small-amplitude oscillatory shear (SAOS) was used to probe viscoelastic behavior, while oscillating disk rheometry (ODR) and tensile tests quantified cure and mechanical properties. In Part 1, kaolin increased NR stiffness in SAOS and raised the 100% and 300% moduli by about 40% and 50%, respectively, relative to the unfilled NR compound, while reducing cure reversion from 30% to 10% at 150 °C. In Part 2, TESPT produced a threshold-like response: 0.5 phr caused only minor changes, whereas 5 phr led to pronounced stiffening and cure stabilization. At 5 phr, a low-frequency plateau in G′ below 0.1 Hz with no G′–G″ crossover was observed, accompanied by higher M_H and ΔM in ODR and reversion suppressed to 1% after 30 min. These trends indicate the formation of a more connected filler-rubber network, promoted by TESPT-assisted interfacial coupling/adhesion, while also reflecting the ability of TESPT (tetrasulfide) to contribute sulfur and modify the curing chemistry. Mechanically, kaolin produced marked stiffness increases, with the 100% and 300% moduli increasing by an additional 9% and 36%, respectively, at 5 phr TESPT. At the same time, ultimate tensile strength remained lower than that of neat NR, and elongation at break decreased slightly. Overall, adding TESPT during mixing enhances interfacial coupling and network connectivity and, at higher loading, also influences cure chemistry, yielding higher modulus and strongly improved reversion resistance without increasing ultimate tensile strength relative to neat NR. Full article

(This article belongs to the Special Issue Organo-Clays: Preparation, Characterization and Applications)

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20 pages, 4878 KB

Open AccessArticle

Transforming Bentonite into High Sorption Capacity Organoclays for Gasoline, Diesel, and Kerosene

by Jessica de Carvalho Arjona, Paulo Henrique Sousa, Nicole Raymonde Demarquette and Francisco Rolando Valenzuela-Diaz

Minerals 2026, 16(1), 14; https://doi.org/10.3390/min16010014 - 23 Dec 2025

Cited by 1 | Viewed by 1006

Abstract

Bentonite is the most widely used raw material for producing organoclays, which have numerous industrial and environmental applications. Due to their hydrophobicity, high swelling, and strong affinity for organic compounds, organoclays are effective in removing organic solvents from contaminated water originating from pipeline leaks, oil spills, traffic accidents, and industrial discharges. Such contamination not only degrades water quality but also forms surface films that hinder oxygen transfer, threatening aquatic ecosystems. In this study, two sodium bentonites with different specific surface areas (30 and 50 m²/g) were modified with three quaternary ammonium salts of varying molar masses and alkyl chain lengths (Sun, Arq, and Arm) to evaluate their performance in organic solvent sorption (gasoline, diesel, and kerosene). The materials were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron microscopy (SEM), and swelling capacity and sorption efficiency. The swelling capacity was determined according to ASTM D5890-19 (Foster method) using gasoline, diesel, kerosene, toluene, and xylene, while the sorption efficiency was assessed following ASTM F726-17 in gasoline, diesel, and kerosene, chosen due to their high potential for water contamination and frequent occurrence in oil spill and leakage scenarios. These solvents also differ in polarity and aromatic content, providing a relevant model for hydrocarbon mixtures commonly found in the environment. Results showed that the interaction between the clay and the surfactant depended strongly on the modifier’s chemical structure. The sorption capacity increased with greater interlayer expansion, surfactant molar mass, and specific surface area of the clay. Among all samples, the Arm-modified natural bentonite (VLArm) exhibited the best performance, with adsorption capacities of up to 6 g/g for diesel, 5 g/g for gasoline, and 5 g/g for kerosene. These values exceeded most previously reported organoclays. These findings demonstrate that optimizing the combination of clay properties and surfactant chemistry can yield highly efficient, low-cost organoclays for environmental remediation of organic contaminants. Full article

(This article belongs to the Special Issue Organo-Clays: Preparation, Characterization and Applications)

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19 pages, 14036 KB

Open AccessArticle

Enhanced Antibiotic Removal via Adsorption–Photocatalysis Using a ZnO–TiO₂–Halloysite Nanocomposite

by Jairo R. Marques, Rodrigo P. Feitosa, Idglan S. de Lima, Luis H. Oliveira, Edson C. Silva-Filho, Francisco Franco, Juan A. Cecilia and Josy A. Osajima

Minerals 2025, 15(12), 1253; https://doi.org/10.3390/min15121253 - 26 Nov 2025

Cited by 2 | Viewed by 734

Abstract

A nanocomposite combining the photocatalytic activity of ZnO and TiO₂ with the adsorption capacity of halloysite was developed for the degradation of ciprofloxacin hydrochloride (CIP). Characterization was performed by UV-Vis diffuse reflectance spectrophotometry, X-ray fluorescence, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy. The results revealed uniform dispersion of ZnO and TiO₂ particles on the halloysite surface and the formation of heterojunctions, contributing to efficient adsorption and photocatalytic degradation. XRD and XPS analyses confirmed the presence of Ti⁴⁺ in the anatase phase, supporting the high photocatalytic potential of the synthesized samples. Photodegradation tests of CIP (30 mg L⁻¹) showed that the 5Zn-Ti-Hal sample achieved the highest removal efficiency (71.45%), with a predominance of photocatalysis (42.57%) over adsorption (28.58%). Bioassays demonstrated a significant antibacterial effect against Staphylococcus aureus (50.35% inhibitory effect) and no toxicity to Artemia salina (100% survival). These results indicate that ZnO–TiO₂–halloysite nanocomposites are a promising green technology for aquatic remediation, offering efficient CIP degradation, antibiotic inactivation, and environmental safety. Full article

(This article belongs to the Special Issue Organo-Clays: Preparation, Characterization and Applications)

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25 pages, 20193 KB

Open AccessArticle

Effect of a Montmorillonite Modification on the Rheology and Mechanical Properties of a Clay/Natural Rubber Nanocomposite

by Christiano Gianesi Bastos Andrade, Gabriel Akio Mori dos Santos, Michael Cezar Camargo, Abel Cardoso Gonzaga Neto, Ticiane Sanches Valera and Samuel Marcio Toffoli

Minerals 2025, 15(11), 1151; https://doi.org/10.3390/min15111151 - 31 Oct 2025

Cited by 2 | Viewed by 1480

Abstract

Clay/natural rubber (Clay–NR) nanocomposites are a sustainable material class with a wide range of applications. The type and amount of the filler added to the rubber matrix promote significant changes in the matrix properties. Montmorillonitic clays (MMT) are mineral, natural fillers. This study investigates the effect of a modified Brazilian polycationic MMT on the nanocomposite rheology and mechanical properties. The MMT was incorporated into a NR matrix in its natural state, and after modification by cation exchange (MMT^Na) and organophilization (MMT^ORG), at concentrations of 2.5 and 5 phr (parts per hundred parts of rubber). The natural and modified clays were characterized by XRD, FTIR, BET, and SEM/EDS. Mechanical tests (tensile strength, elongation at break, and modulus at 100%) indicated that the use of MMT^Na led to increased strength and modulus, whereas a minor decrease in the elongation was observed. However, the use of MMT^ORG yielded the most significant improvements in the mechanical properties. The rheology tests indicated that the Payne effect was not observed, and the strain-dependent behavior arises from matrix-dominated mechanisms, rather than disruption of a filler network. Vulcanization curves showed that the NR-MMT^ORG composites exhibited higher torque values, corroborated by higher crosslink densities. These findings highlight the critical role of cation exchange modification in optimizing MMT dispersion and interfacial interactions within NR matrices, providing design principles for high-performance sustainable nanocomposites. Full article

(This article belongs to the Special Issue Organo-Clays: Preparation, Characterization and Applications)

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24 pages, 2096 KB

Open AccessArticle

Engineered Organo-Clay Nanocomposites for Dual Cationic/Anionic Dye Removal: Role of Polyethylene Glycol Chain Length

by Amina Sardi, Soumia Abdelkrim, Adel Mokhtar, Khaled Zaiter, Mohammed Hachemaoui, Bouhadjar Boukoussa, Gianluca Viscusi, Zouhaier Aloui and Mohamed Abboud

Minerals 2025, 15(9), 935; https://doi.org/10.3390/min15090935 - 2 Sep 2025

Cited by 2 | Viewed by 1290

Abstract

Water pollution by organic dyes poses serious environmental and health challenges, demanding efficient and selective remediation methods. In this study, we engineered tailored organo-clay nanocomposites by modifying montmorillonite with hexadecyltrimethylammonium bromide (HTAB) and intercalating polyethylene glycol (PEG) chains of two distinct molecular weights (PEG200 and PEG4000). Comprehensive characterization techniques (XRD, FTIR, SEM, zeta potential, and TGA) confirmed the successful modification of the composites. Notably, PEG4000 promoted significant interlayer expansion, as evidenced by the shift of the (00l) reflection corresponding to the basal spacing d, indicating an increase in basal spacing. This expansion contributed to the formation of a well-ordered porous framework with uniformly distributed pores. In contrast, PEG200 produced smaller pores with a more uniform distribution but induced less pronounced interlayer expansion. Adsorption tests demonstrated rapid kinetics, achieving equilibrium in under 15 min, and impressive capacities: 420 mg/g of methylene blue (MB) adsorbed on PEG200/MMT@HTAB, and 385 mg/g of Congo red (CR) on PEG4000/MMT@HTAB. The crucial role of PEG chain length in adsorption selectivity was assessed, showing that shorter PEG chains favored methylene blue adsorption by producing narrower pores and faster kinetics, while longer PEG chains enhanced CR uptake via a stable, interconnected pore network that facilitates diffusion of larger dye molecules. Thermodynamic and Dubinin–Radushkevich analyses confirmed that the adsorption was spontaneous, exothermic, and predominantly driven by physical adsorption mechanisms involving weak van der Waals and dipole interactions. These findings highlight the potential of PEG-modified montmorillonite nanocomposites as cost-effective, efficient, and tunable adsorbents for rapid and selective removal of organic dyes in wastewater treatment. Full article

(This article belongs to the Special Issue Organo-Clays: Preparation, Characterization and Applications)

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23 pages, 2930 KB

Open AccessArticle

Assessment of Nontoxic Surfactant-Modified Kaolinite for Potential Application as an Adsorbent for Mycotoxins

by Milica Ožegović, Marija Marković, Aleksandra Daković, Milena Obradović, Danijela Smiljanić, George E. Rottinghaus, Vesna Jaćević, Ljubiša Ignjatović and Ivana Sredović Ignjatović

Minerals 2025, 15(7), 731; https://doi.org/10.3390/min15070731 - 12 Jul 2025

Cited by 1 | Viewed by 1461

Abstract

In this study, natural kaolin was modified with hexadecyltrimethylammonium bromide (HDTMA-Br) at two levels corresponding to 50% and 90% of its cation exchange capacity. The resulting materials, designated as HKR-50 and HKR-90, were used as adsorbents for the mycotoxins ochratoxin A (OCHRA) and zearalenone (ZEN). The characterization of the HKRs with several methods (X-ray diffraction, DRIFT spectroscopy, thermal analysis (DTA/TG), SEM, zeta potential measurements, and the determination of the point of zero charge and textural properties) confirmed the presence of surfactant ions on the organokaolinites’ surfaces. The adsorption of ZEN and OCHRA by HKRs followed nonlinear adsorption isotherms, suggesting a complex adsorption mechanism. The adsorption capacities of ZEN and OCHRA were similar for HKR-50 and HKR-90 at pH 3, with higher adsorption observed for ZEN (~13.0 mg/g for HKR-50 and HKR-90 for ZEN and ~8.0 mg/g for HKR-50 and HKR-90 for OCHRA). At pH 7, the adsorption of ZEN and OCHRA was lower than at pH 3, especially for OCHRA, but slightly increased with increased amounts of surfactant on the kaolinite surface (8.5 mg/g for HKR-50 and 10.8 mg/g for HKR-90 for ZEN and 2.6 mg/g for HKR-50 and 4.1 mg/g for HKR-90 for OCHRA). Special attention was paid to the safety assessment of the natural kaolin and HKR-90, and toxicological tests confirmed the safety of both materials, as no adverse effects were observed in rats. Full article

(This article belongs to the Special Issue Organo-Clays: Preparation, Characterization and Applications)

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16 pages, 4165 KB

Open AccessArticle

Sorption Properties of Bentonite-Based Organoclays with Amphoteric and Nonionic Surfactants in Relation to Polycyclic Aromatic Hydrocarbons

by Tamara Dudnikova, Marina Burachevskaya, Tatyana Minkina, Saglara Mandzhieva, Inna Zamulina, Leonid Perelomov and Maria Gertsen

Minerals 2024, 14(11), 1132; https://doi.org/10.3390/min14111132 - 8 Nov 2024

Cited by 3 | Viewed by 1690

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are a major scientific challenge due to their profound impact on public and environmental health. Therefore, studying ways to detoxify PAHs is important. In this research, the adsorption ability of bentonite modified with five surfactants, including amphoteric (cocoamphodiacetate disodium and sodium cocoiminodipropionate) and nonionic (lauramine oxide, cocamide diethanolamine, and alkylpolyglucoside) substances for the adsorption of high-molecular benzo(a)pyrene and low-molecular naphthalene from the PAH group was studied. The bentonite and bentonite-based organoclays were characterized using X-ray diffraction and Fourier transform infrared spectroscopy. The results showed that the maximum adsorption of benzo(a)pyrene by organoclays increased compared with the initial mineral. The adsorption of benzo(a)pyrene is higher than that of naphthalene. The adsorption process of benzo(a)pyrene by bentonite and organoclays is predominantly monolayer, as it is better described by the Langmuir model (R² 0.77–0.98), while naphthalene is predominantly multilayer, described by the Freundlich model (R² 0.86–0.96). According to the effectiveness of sorption capacities of organoclays—including the degree of sorption, Langmuir and Freundlich constants, the value of maximum adsorption, Gibbs free energy, and the index of favorability of the adsorption process—the most effective modification was found. For the adsorption of benzo(a)pyrene the best was cocoamphodiacetate disodium, and for naphthalene it was sodium cocoiminodipropionate. Full article

(This article belongs to the Special Issue Organo-Clays: Preparation, Characterization and Applications)

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