Abstract Clay minerals are key indicators of soil evolution and the building blocks of soil behavior. Long-term agronomic trials, in which soil samples have been collected and archived over several decades, provide a valuable opportunity to track the transformation of clay minerals over centennial timescales. To achieve this, the clay mineralogy of the archived soil samples must be characterized in great detail. In this context, the initial clay mineralogy of the <2 μm fraction of one of the world’s oldest experimental sites, the 42 plots of Versailles (France, 1929), was determined using an approach that coupled sequential fractionation with X-ray diffraction profile modeling of 00ℓ reflections. This analysis of the original clay mineralogy confirmed the great complexity of temperate soil clay mineralogy. Seven clay phases were identified, including two quasi-discrete kaolinite and illite phases, and five randomly mixed-layered minerals (MLMs), three of which had three different 2:1 layer types. Results showed that MLMs accounted for >70% of the clay phases, with their proportions increasing as particle sizes decreased. The widespread occurrence of kaolinite-illite MLMs and three 2:1 component MLMs in temperate loess soils was also assessed. Comparisons with previous descriptions of clay mineralogy in temperate soils demonstrated that despite their complex crystal structures, the three 2:1 MLMs exhibited similar relative contributions from their constituent layers, particularly the illite layers. The high proportions of such illitic clay phases quantified in the study suggested that they could serve as key markers in the study of pedogenesis in soils that have developed from sedimentary rocks or deposits under temperate climatic conditions.
Abstract Illite, a common, layered silicate mineral, widely distributed in topsoil and subsoil, is utilized extensively in textiles, medicines, construction, and agriculture due to its distinctive chemical, physical, and mechanical properties. To understand the electronic structures and mechanical properties of illite better, they were studied under pressures ranging from 0 to 20 GPa using density functional theory (DFT) calculations. At ambient pressure, the calculated lattice constants and typical bond lengths were in good agreement with the experimental data. The lattice constants and volumes decreased with increasing pressure. While most bond lengths contracted under pressure, the O–H bond lengths remained nearly constant. Furthermore, analyses of the total and partial density of states, charge density distribution, and energy band structures revealed only minor variations under high pressure, implying that pressure exerts a limited influence on the electronic structure, and that illite retains its structural stability. The elastic constant, C 33 , was less than C 11 and C 22 , whereas C 66 exceeded C 44 and C 55 in the pressure range of 0–20 GPa. These results indicated that the (001) plane exhibits weaker resistance to deformation compared with the (010) and (100) planes, while its shear deformation resistance is greater. Also, Young’s modulus, the shear modulus, and the bulk modulus of illite increased with pressure, indicating enhanced resistance to elastic deformation and shear failure. The Poisson ratio also increased with pressure, indicating increased ductility. A decrease in the ratio of shear modulus to bulk modulus ( G/B ) under higher pressures indicated improved toughness. Moreover, the anisotropy of illite diminished with increasing pressure, implying a reduction in the directional dependence of its shear modulus, Young’s modulus, and bulk modulus. These theoretical calculations provide a microscopic understanding of the behavior of natural illite under pressure and offer valuable fundamental data for practical applications of illite.
Alkali activation of Mercia mudstone offers a pathway to developing low-cement-content construction materials, but early-age reaction pathways and strength development are highly sensitive to water availability, calcium supply, and carbonation. The present study explored whether press mud, a Ca/Fe-bearing by-product of sugar refining, can be used as a co-activatable precursor to guide these processes deliberately. Clay was blended with 10-45 wt.% press mud and activated at an activator-to-press-mud (A/P) mass ratio of 0.22-0.28, then cured either sealed (non-carbonated) or under intermittent CO2 exposure (carbonated) for 3, 7, and 21 days. Time-resolved diffuse reflectance infrared Fourier transform spectroscopy, X-ray diffraction, and scanning electron microscopy were used to track phase evolution and relate it to unconfined compression behavior at elastic, peak, and post-peak strain states. Early curing was governed by surface silication and Fe(III) hydrolysis introduced by press mud; increasing A/P raised alkalinity and dissolved silicate, delayed goethite crystallization, and stabilized ferrihydrite skins, extending the alkaline window for early calcium silicate hydrate and sodium aluminosilicate hydrate formation. At intermediate press mud content (similar to 25 wt.%), Fe-oxyhydroxide pellets disrupted Si-O-Al and Si-O-Si networks, producing a transient reduction in strength. Single-point total suction values, inferred from chilled-mirror dew point psychrometry provided direct water-budget evidence. This showed a suction maximum at 25 wt.% press mud at comparable water contents. Observations were consistent with transient sequestration of pore water by hydrophilic organo-Ca(II) complexes and zeolitic phases and explained the observed strength minimum near similar to 25 wt.% press mud. Carbonation generally increased strength; however, baseline-corrected carbonate formation was consistently lower at high press mud contents, which gives direct evidence for slowed carbonation kinetics when siliceous and Fe-rich surface coatings limited CO2 access.
Cronstedtite from the Salsigne mine, France, has long been known to mineralogists and collectors but has not been characterized previously. The current study is the first thorough investigation of cronstedtite from this locality, using electron microprobe analysis, laser ablation inductively coupled plasma mass spectroscopy, M & ouml;ssbauer spectroscopy, scanning electron microscopy, and single crystal X-ray diffraction. The chemical and structural features of cronstedtite from Salsigne were compared with those of cronstedtites from other localities. The results showed that the chemical/structural signature of cronstedtite from Salsigne could help to distinguish it from cronstedtites found elsewhere. All analyzed polytypes from Salsigne belong to the subfamily A and are mostly 1M and 3T polytypes showing various degrees of disorder. The only exception is the 1T polytype (subfamily C), which was found not as an isolated crystal but allotwinned with a 3T crystal. Other allotwins were also observed in this study: 3T + 1M, 3T + 2M 1, 3T + 6T 2, and 2M 1 + 6T 2. Chemical data indicate that cronstedtite from Salsigne contains the most iron in the tetrahedral sites (x = 0.73-0.90) of any known cronstedtite, although previous studies reported that the iron in tetrahedral coordination is greater in polytypes of subfamily D. The octahedral sites are not fully occupied, and the M & ouml;ssbauer results suggest the presence of a small amount of vacancies. Although the Salsigne mine is known for the extraction of Au and other metals (Ag, Cu, As, Bi, Pb), no traces of these were detected. Traces of Cl and S are present, which seems to be a common feature for cronstedtite.
Only a few studies have been published investigating the use of carbon-doped clays as supercapacitor electrode materials, despite the many potential advantages of using clays, such as their very large specific surface area, reservoir porosity, surface conductivity, vacant crystallographic sites, layered and disrupted structure, hydrophilicity, and abundant availability worldwide. The present study is an attempt to utilize clays in supercapacitors for electrical energy storage. Furthermore, calcination and/or acid activation of kaolinitic, illitic, and smectitic clays was applied with the aim of introducing additional faradaic charge-storage mechanisms and thereby increasing the total capacitance of the clay-carbon black composite beyond the double-layer capacitance. After doping the clay with carbon black, symmetrical supercapacitors were prepared from the clay-carbon composite. Three different electrolyte solutions (H2SO4, KOH, and KCl) were used. Cyclic voltammetry measurements indicated the presence of double-layer capacitance, which may vary depending on the clay minerals, their treatment, and the electrolyte used. For smectitic clay, additional anodic currents were observed in the presence of a KCl electrolyte. Carbon-doped smectitic clay electrodes in KCl electrolyte achieved capacitance values only slightly lower than those of pure carbon black electrodes, despite containing similar to 1.9 times less carbon. The greatest capacitance of 5.11 F cm(-3) was achieved for kaolinitic clay with H2SO4 electrolyte, and an electrode thickness of 2.5 mm. This study demonstrated that supercapacitors based on clay-carbon black composites are feasible; however, additional research is required to better understand the interactions between carbon and clay particles.
Abstract A simple acid treatment was employed to modify the surface of metakaolin (MK) for enhanced visible light photocatalytic degradation of Rhodamine B (RhB). The effects of acid treatment on the photocatalytic performance of MK were investigated systematically. The systematic characterization results demonstrated that acid treatment removed oxide impurities and free metal ions on the surface of MK effectively, while increasing its specific surface area; however, it also induced partial leaching of structural Fe species. Among the three inter-related structure-function modulation effects, the removal of surface impurities (i.e. oxides and metal ions) and the concomitant increase in specific surface area were the predominant performance-enhancing mechanisms. This synergistic effect markedly enhanced the number of active sites exposed on the surface of MK, thereby facilitating the adsorption of positively charged RhB molecules and promoting the kinetics of photocatalytic degradation. Detailed analysis of the acid-treatment cost and performance gain suggested that 45 min of acid treatment would achieve optimal performance. The photocatalytic degradation rate of RhB by the MK sample treated with acid for 45 min was 53% greater than that of the original MK. This research enhanced understanding of the structural characteristics of kaolinite, particularly its photocatalytic properties.
Abstract Natural Moroccan clays such as bentonite, Ghassoul, and kaolin, are used extensively in consumer and environmental applications where their geochemical stability is critical. The potential release of potentially toxic elements (PTEs) and naturally occurring radionuclides from these raw materials remains poorly constrained, however. The present study investigated mineralogical controls on the leaching of potentially toxic elements (PTEs: Ag, As, Cd, Co, Cr, Cu, Li, Mn, Mo, Ni, Pb, Se, Sn, V, and Zn) and radionuclides (Po, U, Th, Ra) from three raw Moroccan clays: a montmorillonite-rich clay (Mnt), kaolinite-rich clay (Kln), and stevensite-rich clay (Stv). A multi-disciplinary methodology combined mineralogical (X-ray diffraction, XRD), chemical (X-ray fluorescence, XRF; inductively coupled plasma-optical emission spectroscopy, ICP-OES), and radioactivity spectrometry analyses with standardized leaching tests (EN 12457-4, 2002) to quantify elemental mobility and assess environmental risk. The results revealed distinct leaching signatures controlled by the clay mineralogy. The large cation exchange capacity of Mnt-rich clay favored cation release (e.g. Zn, exceeding inert waste limits), with moderate mobility of As (~12%) and Mo (~11%). In contrast, the Kln-rich clay exhibited low mobility of PTEs and radionuclides, consistent with its inert geochemical behavior and low specific surface area. Stevensite-rich clay exhibits significant mobility of molybdenum (~91.3%) and moderate mobility of arsenic (~22.6%) under mildly alkaline conditions. Despite the relatively high natural radioactivity of the Stv-rich clay, leachate concentrations of alpha-emitting radionuclides remained limited (<15 Bq kg –1 ), causing negligible radiological risk. These findings demonstrate that the clay mineralogy, rather than total contaminant concentration, is the primary factor dictating leaching behavior. This underscores the necessity of mineralogy-specific risk assessments for the safe management and application of industrial clays, particularly the Stv-rich Ghassoul clay, in consumer and environmental contexts.
Highly transparent thin films that exhibit circularly polarized luminescence (CPL) and which can be prepared by simple, water-based processes are important for advanced optical devices. However, most reported CPL-active thin films contain luminophores that were carefully designed to be strongly emissive and CPL-active in the solid state. Consequently, there is a need for water-based processes that can take luminophores that are essentially non-emissive as neat solids and use their CPL in the solution state to prepare transparent CPL-active films. In the present study, clay mineral-organic cation hybrids were prepared as CPL-active materials. Hybrid films of a synthetic saponite, Sumecton SA (SSA), and a chiral binaphthyl ammonium salt, (R)- or (S)-4,4-dibutyl-2,6-bis(3,4,5-trifluorophenyl)-4,5-dihydro-3H-dinaphtho[2,1-c:1 ',2 '-e]azepinium bromide (CBNC), that shows CPL in aqueous solutions, were prepared. Aqueous dispersions of SSA-CBNC hybrids were vacuum filtered to obtain optically transparent films containing CBNC molecules. Whereas CBNC was almost non-emissive as a solid powder, the hybrid films displayed fluorescence and clear CPL signals. The dissymmetry factor (|g| value), which represents the CPL efficiency of CBNC in the hybrid films was enhanced compared with that in aqueous solution. The enhancement was estimated to originate from clay-induced changes in the molecular conformation (e.g. a change in the binaphthyl dihedral angle). These results demonstrate that clay mineral-organic cation hybrids provide a simple, water-based route to transparent CPL-active thin films. Furthermore, clay interlayers may potentially be used to control the chiroptical properties of organic luminophores without covalent modification.
The interaction between iron released from corroded steel canisters and bentonite is a key process influencing the long-term performance of nuclear waste repositories. In particular, the migration of Fe & sup2;(+) into montmorillonite (Mnt) interlayers may alter its hydration, swelling, and ion-transport properties. In the present study, molecular dynamics simulations were performed to investigate the hydration behavior, structural response, and transport properties of Fe-exchanged montmorillonite (Fe-Mnt) under varying hydration states. The simulations focus on short- to intermediate-time-scale Fe2+ and Fe3+ interlayer exchange and hydration effects, and do not consider long-term structural substitution, Fe-bearing clay phase stabilization, or secondary iron mineral precipitation. Systems containing Na+-, Fe2+-, and Fe3+-Mnt were examined using both periodic and edge-exposed configurations to evaluate interlayer structure, ion exchange, and free energy of Fe intercalation. The results show that Fe ions influence the interlayer spacing primarily at low water contents (<1 bilayer), where Fe-Mnt exhibits a d-spacing 1-2 & Aring; larger than Na-Mnt due to stronger hydration. The calculated hydration energies follow the order Fe(2+)3++. Both water and ion diffusion coefficients decrease upon Fe ion intercalation, with Fe2+ ions diffusing an order of magnitude more slowly than those of Na+. Free energy profiles further confirm that Fe2+ and Fe3+ ions are thermodynamically favored in the interlayer, with Fe3+ being the most stable. These findings provide molecular-scale insights into the mechanisms of Fe-Na exchange and their implications for bentonite alteration in repository environments.
Understanding the long-term fate of radioactive cesium (137Cs) following nuclear accidents requires mechanistic knowledge of its adsorption on soil minerals. Although todorokite is a major tectomanganate, the mechanisms governing Cs+ adsorption at the trace levels typical of environmental contamination remain poorly understood. This study examined the concentration-dependent adsorption mechanisms of Cs+ on todorokite through molecular dynamics (MD) simulations. Selectivity-coefficient calculations based on potential of mean force (PMF) profiles showed that sodium ions (Na+) were energetically favored on external (100) and (010) todorokite surfaces, whereas this selectivity was reversed dramatically in favor of Cs+ within tunnel nanopores. Na+ encountered no significant kinetic barriers upon tunnel entry, but the interior was thermodynamically unfavorable; in contrast, Cs+ faced high entry barriers but gained strong interior binding, resulting in slow desorption and high retention. Thus, the exceptional Cs+ selectivity of todorokite arises from the contrasting energetic landscapes. Isotherm modeling of published experimental data, constrained by MD-derived equilibrium adsorption constants, suggested a concentration-dependent shift in dominant uptake sites, with intra-tunnel sites governing high-affinity adsorption at low Cs+ concentrations, whereas external surfaces (where both inner- and outer-sphere complexes form) become dominant at higher Cs+ concentrations.
Despite extensive research on asbestos mineralogy and health impacts, comprehensive multi-analytical characterization of naturally occurring asbestos (NOA) in ophiolitic m & eacute;langes of central T & uuml;rkiye is still lacking. The present study examines asbestos-form minerals within the ophiolitic m & eacute;lange northeast of K & imath;raman village (Karaman, T & uuml;rkiye), with a focus on chrysotile, tremolite, and talc. These minerals were formed through intensive alteration processes, including serpentinization, talc formation, listwanitization, chloritization, carbonation, and silicification. The main objective was to characterize the mineralogical, morphological, and chemical features of asbestos-form serpentine and amphibole minerals and to evaluate their potential environmental and health implications. Analytical techniques such as optical microscopy, X-ray diffraction (XRD), differential thermal analysis-thermogravimetry (DTA-TG), Fourier-transform infrared (FTIR) and Raman spectroscopy, as well as scanning and transmission electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX, TEM-EDX), were employed. The results confirmed the presence of nearly pure chrysotile, talc, and tremolite. Thermal and vibrational analyses revealed characteristic dehydroxylation reactions and diagnostic spectral bands. The SEM and TEM imaging displayed fibrous and acicular morphologies, while TEM-EDX confirmed typical chemical compositions, including minor Fe content (3-5%). Both chrysotile and tremolite fibers exhibited dimensions within the respirable range and elemental characteristics that are commonly associated with increased toxicity in asbestos minerals. The co-existence of Fe-bearing chrysotile and respirable-size tremolite fibers indicates a potential for asbestos-related health risks under conditions of environmental disturbance or exposure. These findings underscore the need for environmental monitoring and suggest the regional geological formations are a potential public health concern.
Halloysite nanotubes (HNTs), naturally abundant clay minerals with unique tubular structures and biocompatibility, offer significant potential as an enzyme immobilization matrix. Conventional functionalization methods often involve energy-intensive processes or compromise enzyme activity, however. The study offers an approach to functionalizing HNTs via alkali activation and polydopamine (PDA) coating for efficient immobilization of beta-glucosidase (BG). Alkali treatment enhanced surface hydroxyl density and defect sites, while PDA deposition through mild oxidative polymerization provided a reactive interface for covalent enzyme conjugation mediated by N-(3-dimethylaminopropyl)-N '-ethylcarbodiimide hydrochloride (EDC) crosslinking. Structural characterization (XRD, FTIR, SEM-EDS) confirmed successful PDA coating and enzyme binding while preserving the crystalline integrity of HNTs. At an optimal loading of 167 mg g-1 support, the immobilization efficiency was 83% with retained activity. The immobilized BG not only exhibited optimal catalytic performance at pH 6.0 and 60 degrees C but also enhanced stability against pH/temperature fluctuations through immobilization. Kinetic analysis revealed a 39% increase in V max (4.73 vs 3.40 mM L-1 min-1) and sustained substrate affinity (Km=10.4 mM L-1). The biocatalyst retained >= 84% activity after 30 days of storage at 4 degrees C and 53% activity over six re-use cycles, attributed to the rigid enzyme conformation stabilized by covalent PDA coupling and HNTs confinement. The research results presented are expected to broaden the application scope of halloysite in the field of enzyme catalysis and provide a feasible solution for improving the catalytic stability of beta-glucosidase.
This article studies the geological structure, mineralogical composition, genesis, and sorption properties of Khonguruu zeolite deposit (Republic of Sakha, Russia). Although it is one of the largest developed deposits in Russia, detailed studies of the mineral composition and physicochemical properties have not been conducted previously, which limits its industrial potential. Zeolites were studied with X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis (DTA), X-ray fluorescence spectrometry (XRF), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) and cation exchange capacity (CEC) analyses. Experiments on the sorption of radioactive cesium were also carried out. Zeolites formed four beds with an average content of 50-85%. The main focus of this study is on the detailed investigation of its mineral composition. These data, together with the analyses of ion-exchange complexes and color, provided an opportunity to distinguish between different types of zeolites. The zeolite minerals are represented by heulandite-1, heulandite-2 and, to a lesser extent, clinoptilolite. For the first time, a significant presence of amorphous silica was demonstrated in zeolite samples and used for correction of the crystallochemical formula of zeolites. On the basis of exchangeable cations composition, two main types of zeolites were found at the deposit: alkaline and alkaline-earth. The CEC of the zeolites ranged from 139 to 214 cmolc kg-1 and high 137Cs sorption. The zeolites have a volcanogenic-sedimentary genesis and were formed from ash material of basic and acidic composition in coastal sea waters with alternating conditions of low and high salinity. Based on the data obtained, it can be concluded that the alkaline raw material can be used as a sorbent for wastewater treatment.
Smectite- and zeolite-dominated assemblages occur at different depths within the same volcanic tuff sequence at the study site, indicating variability in post-depositional alteration conditions. The present study investigated the geological and environmental factors associated with the vertical mineralogical differences using outcrop and core samples from Pohang, South Korea. Mineralogical, geochemical, thermal, spectroscopic, and microbial analyses were conducted on representative samples. The outcrop samples contain Ca-smectite, cristobalite, and amorphous aluminosilicates, whereas the core samples contain zeolite (clinoptilolite and mordenite), quartz, and feldspar. (Na,Ca)-smectite occurs only at specific depths within the core. Major- and trace-element geochemistry indicates that the outcrop and core samples were derived from rhyolitic and andesitic precursors, respectively. Chondrite-normalized rare earth element patterns show no evidence of hydrothermal enrichment or depletion, suggesting diagenesis as the dominant alteration process. Bacterial community compositions, used as environmental indicators, indicate contrasting formation environments: the outcrop samples represent anaerobic, freshwater conditions, whereas the core samples reflect aerobic and saline conditions. M & ouml;ssbauer spectra independently support these redox differences, showing structurally bound Fe within smectite in the outcrop sample and hematite-magnetite assemblages in the core samples. These results indicate that variations in precursor composition, salinity, and redox conditions were closely associated with the development of contrasting smectite- and zeolite-bearing assemblages within the same volcanic sequence.
Organomontmorillonite-type (O-Mnt) antibacterial agents are less susceptible to development of resistance by bacteria. The aim of the present study was to test the effects of O-Mnt samples, which were reported to be effective against Staphlococcus aureus and Streptococcus mutans in previous studies and to act as a scavenger for opportunistic pathogenic microorganisms, Actinomyces viscosus and Bacteroides fragilis, which cause severe infections such as periodontal diseases, endocarditis, and lung infections. O-Mnt samples with single and mixed surfactant layers, namely benzethonium montmorillonite (Mnt-BZT) and cetylpyridinium and N-lauroyl sarcosinate montmorillonite (Mnt-CP-SR), were subjected to X-ray diffraction, thermogravimetric analysis, attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR) and zeta potential analyses to determine some key structural properties. Within the scope of the present study, detailed X-ray photoelectron spectroscopy (XPS) analyses were performed to elucidate the external surface structures, which are important in explaining their antibacterial properties. There have been few studies on XPS analysis in terms of types of surfactants used in O-Mnt preparation. These analyses made it possible to estimate the interaction between the surfactants on the external surface and the bacterial cell wall leading to lysis. A. viscosus, a facultative anaerobe, and B. fragilis, a strict anaerobe, required specific culture conditions, and their antibacterial susceptibility testing was conducted with caution due to challenges in isolation and antimicrobial resistance. Antibacterial susceptibility tests including the agar well diffusion test, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) determinations and time-kill assay showed that both OMnt samples were effective against the bacteria used. The XPS analyses of the exterior surface structure of O-Mnt revealed that contact killing was the mechanism of antibacterial effect. In vitro cytotoxicity and in vivo animal studies indicated that both O-Mnt samples can be used safely as antibacterial agents in oral and topical applications.
Aflatoxins (AFs) are contaminants of several agricultural crops, and aflatoxin B1 (AFB1) is the most toxic AF and a known carcinogen to humans and animals. A practical solution for decontamination of animal feed contaminated with AFB1 is to use bentonite, a natural raw material consisting primarily of the mineral montmorillonite (dioctahedral 2:1 layer aluminosilicate of the smectite group). The aims of this research were to compare mineralogical, structural, chemical, and physico-chemical characteristics of three bentonites from the Balkan region (Beretnica clay from Serbia (B-Clay), Yellow clay (Y-Clay) and Gray clay (G-Clay) from Bosnia) with the characteristics of a commercial pharmaceutical-grade bentonite (P-Clay), and to study the behavior of the bentonites in phosphate buffer at pH 3 and 7 with and without AFB1. AFB1 adsorption by bentonites followed non-linear isotherms with maximum amounts adsorbed from 75.43 mg g-1 at pH 3 and 62.91 mg g-1 at pH 7 for the P-Clay to 100.25 mg g-1 at pH 3 and 78.58 mg g-1 at pH 7 for the B-Clay. The Ca-bentonites (B-Clay-cis-vacant, 83% montmorillonite; Y-Clay-cis/trans-vacant, 98% montmorillonite; and G-Clay-trans-vacant, 88% montmorillonite) were efficient adsorbents of AFB1, with the greater adsorption observed at pH 3. The P-Clay (Na/Ca bentonite, cis-vacant, 63% montmorillonite), exhibited the lowest AFB1 adsorption at both pH values. The behavior of bentonites in buffers, in the presence of AFB1, indicated that ion exchange and AFB1 adsorption by montmorillonite occurred simultaneously. Cations with larger hydrated radii (Mg2+ and Ca2+) represented the primary active sites for AFB1 adsorption. The position of OH- groups in cis-montmorillonites at the same side of the octahedral site enhanced AFB1 adsorption, making them more available for protonation of edge sites and subsequent interaction with AFB1. Specific characteristics of the montmorillonite in bentonites play an important role in AFB1 adsorption, although the buffer composition also affects the adsorption process significantly.
India is rich in mica deposits, and, after extraction, similar to 75% of the mica material is discarded as waste during the cleaning and processing stages. Effective modification methods may enhance the properties of the waste mica, making it suitable for a number of environmental applications, but this has received limited attention despite its availability. The present study focused on mining-derived waste mica and was aimed specifically at assessing the effects of controlled acid modification on its structural and physico-chemical properties. To achieve this, waste mica was ground and activated using various concentrations of sulfuric acid (1 M, 2 M, and 3 M) under continuous shaking at room temperature for periods varying from 24 to 72 h. The physico-chemical characteristics of the waste mica and acid-treated waste mica were studied by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) method, scanning electron microscopy (SEM), zeta potential, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The molecular arrangement of the raw and acid-activated waste mica was elucidated using VESTA software. The waste mica was identified as biotite based on structural and compositional characteristics. The XRF and XRD studies indicated that acid activation leads to progressive expansion of the interlayer space of waste mica by way of cation leaching and the subsequent weakening of interlayer forces. After conversion to nanoform and treating the waste mica with 2 M sulfuric acid for 48 h, the characteristic mica peak shifted from 8.99 to 8.76 degrees 2 theta, indicating the enlargement of interlayer space with a concomitant increase in the specific surface area from 4.32 to 228.02 m(2) g(-1). The structural and surface modifications achieved through acid treatment enhanced the functional characteristics of the waste mica, indicating its suitability as a cost-effective and sustainable alternative to conventional adsorbents for use in environmental remediation.
