Search Results (162)

Mortars taken from the 16th century Venetian Fortress of Bergamo (Italy) were characterized (binder-concentrated fractions and aggregate fractions as well as bulk samples) with a multi-analytical approach using X-ray diffraction (XRD), inductively coupled plasma optical emission spectrophotometry (ICP-OES), optical microscopy (OM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). The results showed the presence of calcite, hydrocalumite and hydrotalcite-type compounds, brucite, aragonite, plombierite and a large fraction of amorphous phases (ranging between 14 and 27 wt%) in the binder. Quartz and carbonate-rich sands were used as aggregates. The mortar is a Mg-rich material containing 4–5 wt% brucite. No evidence of magnesite or hydromagnesite was found in any sample, although these phases are frequently detected in the binder of buildings from the Renaissance period that are located in Northern Italy. The large average amount (12–13 wt%) of reactive silicate, such as Mg-containing phyllosilicates that can react with lime, and the presence of carbonate-containing hydrocalumite and hydrotalcite indicate hydraulic interactions between lime and reactive silicate aggregates. The CO₂/H₂O_bound ratio, evaluated from the weight loss referred to the finer fraction (<63 μm), ranges from 1.99 to 2.55, which suggests that the walls of Bergamo were constructed using lime-based mortar with hydraulic properties. Full article

This study investigates the feasibility of using a triboelectrostatic belt separator (TBS) as a dry alternative to conventional magnetic separation for concentrating apatite from a phyllosilicate-rich phosphate ore from the Unidade de Mineração de Angico, Brazil. The testing material contained 22.9% P₂O₅ and exhibited over 90% mineral liberation even at coarse fractions (+0.6 mm), being mainly composed of apatite and Mg/Al-bearing phyllosilicates. Pilot-scale experiments were carried out in an M6c TBS, evaluating operational parameters such as electrode polarity, belt speed, feed rate, and electrode gap. In the rougher stage, apatite’s positive charging behavior enabled separation from negatively charged gangue, with optimal conditions (run 4) producing a concentrate of 25.3% P₂O₅ at 85.1% recovery. Cleaner experiments further upgraded product quality, with runs 15 and 18 yielding concentrates of 29.0% and 28.9% P₂O₅ and overall P₂O₅ recoveries of 69.3% and 74.5%, respectively. Compared to high-intensity magnetic separation currently applied at the industrial plant, the TBS achieved superior mass and P₂O₅ recoveries and more effective MgO removal, although Fe₂O₃ and Al₂O₃ contents remained slightly above market thresholds. These results confirm the technical feasibility of triboelectrostatic separation for phosphate beneficiation, offering environmental benefits through reduced water consumption and tailings generation. Further research should focus on finer particle sizes (−0.3 mm), electrode design, and surface charge modifiers to enhance industrial performance. Full article

Polypropylene (PP) dielectric capacitors are crucial for electronics and electric power systems due to their high power density. However, their relatively low energy density limits their practical application in energy storage devices, presenting a long-standing challenge. Montmorillonite (MMT), a natural phyllosilicate mineral abundantly found on earth, features a two-dimensional nanosheet structure and excellent insulating properties. MMT nanosheets have shown promise in enhancing the breakdown strength and energy storage capability of PP dielectric, but compatibility issues with the PP matrix remain a challenge. In this study, we propose a novel surface modification strategy in which polystyrene (PS)-capped MMT (PCM) nanosheets are synthesized through a polymerization–dissolution process. The modified PCM nanosheets demonstrate improved compatibility and are well dispersed within the PP matrix. Optimal loading of the PCM nanosheets effectively dissipate charge energy and hinder the growth of electric trees in the PP matrix. As a result, the PP nanocomposite with 0.2 wt% PCM nanosheets exhibits an enhanced breakdown strength of 619 MV m⁻¹ and a discharged energy density of 4.23 J cm⁻³, with an energy storage efficiency exceeding 90%. These findings provide a promising strategy for the development of high-energy-density dielectric capacitors in an economical manner. Full article

The technological potential and sustainability of red clays from the Taveiro region (Coimbra, Portugal) for structural ceramic applications have been investigated. Thirteen representative samples granulometric, mineralogical, chemical analysis, and technological characterization were conducted to determine the suitability for extrusion-based ceramics, aligned with circular economy and climate goals (e.g., PNEC2030, RNC2050). The samples exhibited a high fine fraction content (<0.002 mm up to 76%) and plasticity index (PI; up to 41%), associated with significant smectite, illite, and kaolinite content. Bulk mineralogy was dominated by Σ phyllosilicates (up to 77%) and quartz (12%–29%), while chemical analyses showed high SiO₂ and Al₂O₃ content, moderate Fe₂O₃, and low CaO/MgO, typical of aluminosilicate clays for red ceramics. High cation exchange capacity (CEC; up to 49 meq/100 g) and specific surface area (SSA; up to 83 m²/g) reflected smectite-rich samples. Firing tests at 900 and 1000 °C demonstrated decreasing water absorption and shrinkage with increased temperature, with some samples yielding lower porosity and higher strength (~12 MPa), confirming suitability for bricks and tiles. Two samples showed higher plasticity but greater shrinkage and porosity, suggesting applicability in porous ceramics or blends. This work highlights the role of mineralogical and technological indicators in guiding the eco-efficient use of georesources for ceramic manufacturing. Full article

A small, strongly schistose Ni-laterite occurrence at the Vermion ophiolite (40°26′ Ν, 22°10′ Ε), Northen Greece, along a strong shear zone, is characterized by relatively high Ni, Co and Mn contents, magnetite as the dominant mineral, garnet (grossularite), theophrastite [β-Ni(OH)₂], otwayite-like phase (ideally Ni₂CO₃(OH)₂.H₂O), (Ni, Co, Mn)-hydroxides, and Ni-phyllosilicates. New analytical data, including black-white and color back-scattered electron images (BSEIs), elemental mapping and scanning, and Raman Spectroscopy, alongside silicates and hydroxides revealed the presence of varying silica content (less than 1 to 29 wt.%) in theophrastite and in (Ni, Co, Mn ± Fe)-hydroxides, although the X-ray powder diffraction data correspond to those of pure hydroxides. The gradual stacking of fine fibrous otwayite-like crystals to the boundaries of successive thin layers and within layers themselves, results in porous mineral phases of varying density shifting towards more compact mineral with increasing residence time. The presented data suggest that a potential explanation of the presence of Si in theophrastite may be the precipitation of Si after initial Ni-hydroxyl-carbonate fine crystals deposition. A potential sequence of the stability of Ni-minerals at Vermion may be as follows: Hydroxyl-carbonates < [β-Ni(OH)₂] (theophrastite) < (Ni, Co, Mn)(OH)₂ < Ni-phyllosilicates; this may be a significant factor for Ni-exploration in Ni-larerite deposits. Full article

Numerical simulations enable us to couple multiphase flow and geochemical processes to evaluate how sequestration impacts brine chemistry and reservoir properties. This study investigates these impacts during CO₂ storage at the San Juan Basin CarbonSAFE (SJB) site. The hydrodynamic model was calibrated through history-matching, utilizing data from saltwater disposal wells to improve predictive accuracy. Core-scale simulations incorporating mineral interactions and equilibrium reactions validated the model against laboratory flow-through experiments. The calibrated geochemical model was subsequently upscaled into a field-scale 3D model of the SJB site to predict how mineral precipitation and dissolution affect reservoir properties. The results indicate that the majority of the injected CO₂ is trapped structurally, followed by residual trapping and dissolution trapping; mineral trapping was found to be negligible in this study. Although quartz and calcite precipitation occurred, the dissolution of feldspars, phyllosilicates, and clay minerals counteracted these effects, resulting in a minimal reduction in porosity—less than 0.1%. The concentration of the various ions in the brine is directly influenced by dissolution/precipitation trends. This study provides valuable insights into CO₂ sequestration’s effects on reservoir fluid dynamics, mineralogy, and rock properties in the San Juan Basin. It highlights the importance of reservoir simulation in assessing long-term CO₂ storage effectiveness, particularly focusing on geochemical interactions. Full article

To address lithium extraction from clay-type lithium ore from the Qaidam Basin, this study identified key controlling factors through particle fractionation, acid-leaching–roasting experiments, and mineral characterization. The results demonstrate that particle size optimization enriched the lithium to 87.65 ppm, where a 74% leaching rate was achieved with 65 ppm extraction, which established intermediate-sized samples as optimal. During acid leaching, adsorbed lithium ions with a phyllosilicate interlayer were released via the ion exchange process instead of mineral dissolution, as verified by the Li-O/S-O peak shifts in the FTIR spectra. The roasting induced hydroxyl elimination, carbonate decomposition, and silicate restructuring but triggered lithium encapsulation via mineral phase reorganization, which caused a sharp leaching rate decline. Effective lithium extraction requires integrated particle size screening, acid-leaching optimization, and roasting-induced phase encapsulation disruption. This study established theoretical foundations for clay-type lithium ore exploitation. Full article

In the field of green chemistry, the development of more sustainable and cost-efficient methods for synthesizing primary amines is of paramount importance, with catalyst research being central to this effort. This work presents a facile, aqueous-phase synthesis of highly active cobalt catalysts (Co-Ph@SiO₂(x)) via pyrolysis of silica-supported cobalt–phenanthroline complexes. The optimized Co-Ph@SiO₂(900) catalyst achieved exceptional performance (>99% conversion, >98% selectivity) in the reductive amination of acetophenone to 1-phenylethanamine using NH₃/H₂. Systematic studies revealed that its exceptional performance originates from the in situ pyrolysis of the cobalt–phyllosilicate complex. This process promotes the uniform distribution of metal cobalt nanoparticles, simultaneously enhancing porosity and imparting bifunctional (acidic and basic) properties to the catalyst, resulting in outstanding catalytic activity and selectivity. The catalyst demonstrated broad applicability, efficiently converting diverse ketones (aryl-alkyl, dialkyl, bioactive) and aldehydes (halogenated, heterocyclic, biomass-derived) into primary amines with high yields (up to 99%) and chemoselectivity (>40 examples). This sustainable, non-noble metal-based catalyst system offers significant potential for industrial primary amine synthesis and provides a versatile tool for developing highly selective and active heterogeneous catalysts. Full article

Mining waste presents significant environmental and public health risks due to the potential release of toxic substances when improperly managed. In this study, four tailings samples were taken to evaluate the environmental risks in the Ponce Enríquez mining area in Ecuador. Chemical characterization and X-ray Fluorescence Spectrometry (XRF) were used to analyze the content of potentially toxic elements (PTEs) of interest (As, Cd, Cr, Cu, Ni, Pb, and Zn), and X-ray Diffraction (XRD) for mineralogical characterization. The contamination index (IC) was calculated to assess the potential hazard associated with the content of PTEs in the mining wastes. To assess environmental risks, leaching tests were carried out to evaluate the potential release of PTEs, and Acid-Base Accounting (ABA) tests were conducted to determine the likelihood of acid mine drainage formation. The results revealed that the PETs concentration exceeded the maximum permissible limits in all samples, according to Ecuadorian regulations: As, Pb, and Cd were identified as critical contaminants. Mineralogically, quartz was the dominant phase, followed by carbonates (calcite, dolomite and magnesite), phyllosilicates (chlorite and illite), and minor amounts of pyrite and talc. The IC indicated high to very high contamination risk levels, with As being the predominant contributor. Although leaching tests met the established limits for non-hazardous mining waste, the ABA test showed that all samples had a high potential for long-term acid generation. These results underscore the need for implementing management strategies to mitigate the environmental impacts and the development of plans to protect local ecosystems and communities from the adverse effects of mining activities. Full article

Glauconite, a diagenetic sedimentary phyllosilicate mineral, holds significant importance in soil science, as it is commonly used in soil characterization (as in greensands) and can be identified in the field by its color and morphology. It is a potential fertilizer, rich in essential macronutrients like potassium, phosphorus, calcium, and numerous micronutrients such as manganese, zinc, copper, cobalt, and nickel. In this meticulously conducted study, we extracted five individual elements (potassium, calcium, magnesium, sodium, and zinc) from washed glauconite samples separated into five different size fractions using a suite of acids. The acids employed were nitric acid, hydrochloric acid, acetic acid, and phosphoric acid, each prepared at the same molarity of 0.1 M. Water was used as the control solubilizing medium. The extractant behavior of the acids was assessed by measuring concentrations of each element by the ICP-OES device. The results demonstrate that nitric acid consistently exhibits the highest efficacy in releasing elements, followed by hydrochloric acid and phosphoric acid, while acetic acid results in the lowest release of these nutrients. These findings support the use of acidification treatment of glauconite, enhancing elemental release and potentially reducing the amount of glauconite needed as an alternative fertilizer, thus adding economic value. Full article

Clays are fundamental raw materials in the ceramics industry due to their plasticity, mineralogical composition, and thermal behavior. This study characterizes four clay samples from Bustos (Portugal), aiming to assess their suitability for ceramic applications through granulometric, geochemical, mineralogical, and technological assays, looking at aspects such as their plasticity and sintering behavior. A textural analysis of the samples revealed distinct granulometric profiles, being dominated by silty–clayey fractions and low amounts of coarse particles, indicating high plasticity potential. Three samples showed an alkaline pH (8.17–8.63), and one an acidic pH (5.11), which can significantly influence the rheology and firing behavior of the ceramic body. Samples had a predominance of phyllosilicate minerals, followed by quartz and magnetite–maghemite, and trace amounts of feldspars, anatase, bassanite, and siderite. In the clay fraction, smectite, illite, and kaolinite were identified. By combining classical analysis techniques with ceramic technology principles, this study contributes to the sustainable development of local ceramic industries, emphasizing the importance of characterizing natural raw materials for industrial applications. The plasticity tests showed strong workability in two samples, which exhibited high values of plasticity and moldability, making them suitable for shaping processes in ceramic production. Also, sintering behavior tests revealed that the same clays exhibited good densification during firing, with relatively low shrinkage. Full article

Talc, as a phyllosilicate mineral, is often associated with sulfides such as copper, molybdenum, and nickel, which severely impact the flotation of target minerals. Micro-flotation experiments combined with SEM, contact angle, FTIR, TOC, and AFM analyses were performed to explore the influence and mechanism of sodium carboxymethyl starch (CMS-Na) on the flotation behavior of talc with varying particle sizes in a butyl xanthate system. The flotation results indicate that when CMS-Na is used as a depressant, the recovery of coarse talc particles (−74 + 45 μm) is only about 1%, while fine talc particles (−23 μm) maintain a recovery rate of over 70%. FTIR analysis revealed that the interaction between CMS-Na and talc involves both chemical and physical adsorption mechanisms, with the most pronounced effect observed on fine-grained talc surfaces. TOC, AFM, and contact angle measurements further revealed that the proportion of exposed edge surfaces increases as the talc particle size decreases. These edge surfaces exhibited a higher affinity for CMS-Na, resulting in significant reagent adsorption. Consequently, at an equivalent reagent dosage, the adsorption of CMS-Na on the basal planes was reduced, leading to the retention of high surface hydrophobicity. This phenomenon is considered an important factor contributing to the poor depressive effect on fine-grained talc. Full article

Projections for the Brazilian semi-arid (BSA) region estimate a reduction in water bodies and an increase in degraded areas. Recovering degraded soils using treated wastewater (TWW) is a strategy to increase the resilience of the local population to these climatic adversities. This study aimed to evaluate the impact of deficit irrigation with treated effluent on the (geo)chemistry of degraded soil in the BSA. An experiment with the application of TWW was conducted on soil degraded within an agroforestry system. The treatments arranged in randomized block design were WS_0.5 (water supply at 0.5 L/plant/week), TE_0.5 (treated effluent at 0.5 L/plant/week), and TE₁ (treated effluent at 1 L/plant/week). Soil samples were collected (0–15 and 15–30 cm) at the initial condition, after two years of irrigation, and two years after the end of irrigation. Analyses of chemicals and geochemicals were carried out. All treatments increased soil fertility after two years in both layers, with TE₁ resulting in higher Ca²⁺ (0–15 cm: 2.88; 15–30; 3.14; cmolc kg⁻¹), Mg²⁺ (0–15 cm: 2.13; 15–30; 2.00; cmolc kg⁻¹), and K⁺ (0–15 cm: 0.11; 15–30; 0.12; cmolc kg⁻¹), generating a residual effect two years post-irrigation suspension and no risk of salinization. However, TE₁ and mainly TE_0.5 showed an increase in sodium content, making the soil solodic (6–11%). The application of TWW changed the CaO, MgO, and K₂O contents of silt fraction, contributing to the availability of Ca, Mg, and K in soils. Future studies should monitor sodium levels and confirm K-bearing phyllosilicate (illitization) after irrigation with TWW. The application of TWW for a short period (two years) and in small volumes (0.5 L/plant/week) affects (geo)chemistry of degraded soil from the BSA. Full article

In the early Cambrian period, a severe greenhouse effect subjected the Gondwanan continents to accelerated erosion, enriching oceanic waters with essential nutrients, including phosphate, silicon, calcium, magnesium, iron, and trace elements. The nutrient flux, sourced from the volcanic composition of west Gondwana, was recorded as sequences of nodular phosphoritic limestones intercalated with chlorite-rich silts, containing ferrous phyllosilicates such as chamosite and chlorite. The abundant and diverse fossil record within these deposits corroborates that the ion supply facilitated robust biogeochemical and nutrient cycling, promoting elevated biological productivity and biodiversity. This paper investigates the early Cambrian nutrient fluxes from the Gondwanan continental region, focusing on the formation of phosphoritic and ferrous facies and the diversity of the fossil record. We estimate and model the biogeochemical cycling within a unique early Cambrian ecosystem located in South Spain, characterized by calcimicrobial reefs interspersed with archaeocyathids that settled atop a tectonically elevated volcano-sedimentary platform. The configuration enclosed a shallow marine lagoon nourished by riverine contributions including ferric and phosphatic complexes. Geochemical analyses revealed varying concentrations of iron (0.14–3.23 wt%), phosphate (0.1–20.0 wt%), and silica (0.27–69.0 wt%) across different facies, with distinct patterns between reef core and lagoonal deposits. Using the Geochemist’s Workbench software and field observations, we estimated that continental andesite weathering rates were approximately 23 times higher than the rates predicted through modeling, delivering, at least, annual fluxes of 0.286 g·cm⁻²·yr⁻¹ for Fe and 0.0146 g·cm⁻²·yr⁻¹ for PO₄³⁻ into the lagoon. The abundant and diverse fossil assemblage, comprising over 20 distinct taxonomic groups dominated by mollusks and small shelly fossils, indicates that this nutrient influx facilitated robust biogeochemical cycling and elevated biological productivity. A carbon budget analysis revealed that while the system produced an estimated 1.49·10¹⁵ g of C over its million-year existence, only about 0.01% was preserved in the rock record. Sulfate-reducing and iron-reducing chemoheterotrophic bacteria played essential roles in organic carbon recycling, with sulfate reduction serving as the dominant degradation pathway, processing approximately 1.55·10¹¹ g of C compared to the 5.94·10⁸ g of C through iron reduction. A stoichiometric analysis based on Redfield ratios suggested significant deviations in the C:P ratios between the different facies and metabolic pathways, ranging from 0.12 to 161.83, reflecting the complex patterns of organic matter preservation and degradation. The formation of phosphorites and ferrous phyllosilicates was primarily controlled by suboxic conditions in the lagoon, where microbial iron reduction destabilized Fe(III)-bearing oxyhydroxide complexes, releasing scavenged phosphate. This analysis of nutrient cycling in the Las Ermitas reef–lagoon system demonstrates how intensified continental weathering and enhanced nutrient fluxes during the early Cambrian created favorable conditions for the development of complex marine ecosystems. The quantified nutrient concentrations, weathering rates, and metabolic patterns established here provide a baseline data for future research addressing the biogeochemical conditions that facilitated the Cambrian explosion and offering new insights into the co-evolution of Earth’s geochemical cycles and early animal communities. Full article

The effectiveness of copper-based composites, specifically cupric ion (Cu²⁺)-modified phyllosilicate minerals, was evaluated in reducing the concentration of infectious agents in the environment while minimizing metal ion release. The phyllosilicate minerals, vermiculite, exfoliated and unexfoliated, and sepiolite, all modified with Cu²⁺, were compared with copper oxide for their antiviral activity against non-enveloped porcine parvovirus (PPV) and enveloped human coronavirus 229E (HCoV). Sepiolite effectively removed PPV and HCoV from the solution, regardless of Cu²⁺ presence, while vermiculite showed substantial viral clearance only when Cu²⁺ was present. The kinetics of viral clearance was fast, with complete clearance within one hour in many cases. To better understand the mechanism of virus clearance, EDTA was added at different times during the clearance study for PPV. EDTA prevented virus clearance in all vermiculite samples, whereas sepiolite containing copper still demonstrated substantial virus clearance. The addition of BSA before the virus binding was able to block binding in all cases. It was determined that binding is the key mechanism, and PPV can be eluted from the minerals with EDTA and still be infectious. This study provides the potent antiviral mechanisms of Cu²⁺-modified phyllosilicate minerals, offering insights for designing paints and plastics for high-touch surfaces to reduce viral transmission and enhance public health significantly. Full article