Investigating Occurrence State of Rhenium in Limestone Using In Situ Microbeam Techniques

Sub-micrometer distribution of Fe oxides and organic matter in Podzol horizons

The disposal of municipal solid waste (MSW) to thermochemical treatments promotes the formation of ashes as a by-product, which constitutes an important role in the design and operation of energy recovery plants, as the ash can cause corrosion and fouling problems. In this sense, this work analyzed samples of bottom ashes from combustible fractions (organic matter, plastics, textiles, paper/cardboard/Tetra Pak® and sanitary waste) of MSW in natura from Santo André – SP, Brazil. For this, a new methodology for sample preparation was proposed to evaluate the elemental composition of the bottom ashes, for later analysis by Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDS). The obtained data showed a standard deviation of less than 10%, guaranteeing a greater reliability of the results and corroborating with standard deviations presented in the scientific literature. In addition, the elemental composition of the bottom ash was similar between the different combustible fractions evaluated. Keywords: MSW, Combustible fractions, SEM-EDS.

This study evaluates the long-term alterations transpiring in wellbore cement on exposure to acidic environmental conditions. To achieve this, the microstructural, mechanical, and chemical processes that occur in wellbore cement subjected to CO2-saturated brine over a 30-year period are investigated, along with their impact on the cement properties. To investigate the evolution of microstructural and chemo-mechanical properties, wellbore field samples are analyzed using nanoindentation, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and micro-computed tomography (CT) imaging techniques. Nanoindentation provides spatially resolved maps of elastic modulus and hardness, indicating the sample’s stiffness and strength over the reacted zones. SEM-EDS characterizes chemical composition and mineralogical changes in cement exposed to CO2-saturated brine for 30 years. Micro-CT imaging enables non-destructive characterization of pore structure evolution and reaction-induced alterations in cement phases. The results from this study demonstrate that the major cement phases affected by carbonation are calcium-rich, aluminum-rich, and silicate-rich phases. The mechanical strength and stiffness of the calcium-rich phases are observed to have increased near the interface between wellbore cement and the shale rock, due to carbonation over time. However, following the initial increase in mechanical properties, the mechanical strength and stiffness over distance away from the interface dropped significantly, representing the deterioration in the wellbore cement. Through long-term exposure, this study provides the first detailed analysis of chemo-mechanical alterations at the microscale, highlighting how such conditions lead to phase-specific changes in stiffness and strength. Additionally, micro-CT imaging revealed the dissolution and precipitation trends of cement phases along with the micro-porosity, offering insights into the progressive deterioration of wellbore cement. These findings are crucial for understanding long-term wellbore integrity in CO2 storage and subsurface applications. Leveraging wellbore cement that was exposed to CO2-saturated brine in the field over an extended period, this study presents the first detailed examination of the chemo-mechanical and microstructural evolution of individual cement phases.

High-quality direct reduced iron (DRI) powder is essential for applications in catalysis, adsorption, and electromagnetic materials. However, its tendency to reoxidize during processing presents a significant challenge. This study investigates the oxidation behavior of DRI powder during wet ball-milling treatment. Samples were characterized using chemical phase dissolution, X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS) to assess both bulk and surface oxidation. The results reveal that significant oxidation occurs during the wet grinding and subsequent processing stages, with the relative oxidation degree (ROD) of the iron powder increasing sharply from 6.08% to 26.81% as the grinding time is extended from 20 to 40 min. SEM-EDS analysis indicates that oxidation is particularly pronounced in particles smaller than 10 μm. XRD confirms the gradual transformation of Fe0 to Fe3O4 with prolonged grinding, corroborating the chemical analysis. Furthermore, XPS analysis of the Fe 2p, Fe 3p, Fe 3s, and O 1s core levels reveals that the nanoscale surface is composed of Fe2O3, Fe3O4, Fe(OH)3, and FeOOH-a composition distinctly different from the bulk Fe/Fe3O4 phases. These findings underscore the critical roles of particle size and mechanical activation in driving DRI reoxidation during wet milling.

The removal of contaminants in slow sand filters occurs mainly in the biofilm above the filter media called schmutzdecke - a thin biological layer consisting of various microbial communities of algae, bacteria, diatoms and zooplankton. The layer formed ripens along with continuous straining and adsorption mechanism of impurities in raw water. Anadara granosa shell has been broadly used as an adsorbent to trap organic matter, turbid particles and heavy metal ion in raw wastewater. This research is aimed to visualise the microbial community grown on schmutzdecke in 2-weeks ripening period and maps the elemental characterisation of a grinded Anadara granosa shell media after the ripening period using a Scanning Electron Microscope with Energy Dispersive X-ray Spectroscopy (SEM-EDS). The result shows that mostly algae and diatoms have been recognised without species identification. Calcium (67%) and oxygen (21%) dominate the major chemical element contained in grinded Anadara granosa shell media, indicating that calcium carbonate and calcite can replace conventional sand as a more-efficient slow sand filter media, with longer maturing period. Such result can lead to further research about the increase of clamshell usage as a slow sand filter media to treat any types of wastewater, especially in rural areas in developing countries.

The present study aims to evaluate the effect of different operating conditions on fouling composition after woody biomass combustion in an experimental low-power fixed-bed boiler. The boiler was built specifically for research purposes and allows easy removal of areas susceptible to fouling and the control, modification and registry of combustion parameters. The influences of the total airflow supplied and the deposition probe temperature were studied in fouling; differentiating between the layers of fouling adhered to the tube and those deposited over the tube. Thermogravimetry and Differential Scanning Calorimetry (TG-DSC) and Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM-EDS) were performed in order to determine a relationship between the fouling composition and the combustion parameters used. Upon increasing the total airflow supplied and the deposition probe temperature, the amount of organic matter, namely unburned carbon, decreased, indicating a better combustion efficiency. Chemical analysis results of fouling deposits showed that inorganic elements presented different behaviors depending on the collection area and the combustion parameters. Non-volatile elements such as Si and Ca were mostly found in the coarse fraction of the bottom ash and minor amounts were deposited over the tube. Small amounts of Cl in biomass generated serious deposition problems, especially during combustions with low airflow rates.

The high content of organic matter in sludge is the primary reason for the poor solidifying effect and excessive dosage of the cement base. In this study, potassium ferrate and straw fiber are utilized to synergistically enhance the solidifying effect of the cement and elaborate the strength mechanisms. Among them, potassium ferrate was selected to oxidize and crack the structure of organic matter in sludge and consume part of organic matter; straw fiber was used as an adsorption material to absorb some of the organic material and reduce its interference with the cement hydration reaction; the skeleton function of straw fiber in solidified sludge was used to improve the final solidified sludge strength. It is shown that the presence of these two additives significantly improved the cement solidification strength and reduced the moisture content of the solidified body. Moreover, the moisture content and strength followed an obvious linear relationship (adjusted R2 = 0.92), with the strength increasing as the moisture content decreased. After pretreatment with potassium ferrate, the free water content in the dewatered sludge increased by 4.5%, which was conducive to the adequate hydration reaction with cement. The analysis using X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS), and mercury intrusion porosimetry (MIP) revealed potassium ferrate synergizes with straw fibers to promote the production of hemihydrate gypsum and gismondine. However, hemihydrate gypsum, calcium carbonate, and gismondine resulted in structural swelling, which was confirmed by the microscopic morphology and pore structure analysis. However, the adverse effects due to swelling were offset by the increase in strength brought by the above crystalline substances.

The Neoproterozoic carbonate rocks of the Araras Group (Amazon Craton) and the Sete‐Lagoas and Salitre Formations (São Francisco Craton) share a statistically indistinguishable single‐polarity (reversed) characteristic direction. This direction is associated with paleomagnetic poles that do not align with the expected directions for primary detrital remanence. We employ a combination of classical rock magnetic properties and micro imaging/chemical analysis (in thin sections) using synchrotron radiation to examine these remagnetized carbonate rocks. Magnetic data indicate that most samples lack the anomalous hysteresis properties typically associated with carbonate remagnetization (except for distorted loops). Through a combination of Scanning Electron Microscopy with Energy Dispersive X‐ray Spectroscopy (SEM‐EDS), X‐ray Fluorescence (XRF), and X‐ray Absorption Spectroscopy (XAS), we identified subhedral/anhedral magnetite, or spherical grains with a core‐shell structure of magnetite surrounded by maghemite. These grains are within the pseudo‐single domain size range, as do most of the iron sulfides, and are spatially associated with potassium‐bearing aluminosilicates. While fluid percolation and organic matter maturation play a role, smectite‐illitization appears to be crucial for the growth of these phases. X‐ray diffraction analysis, in addition, identifies these silicates as predominantly highly crystalline illite, suggesting exposure to epizone temperatures. These temperatures were likely reached during the final stages of the Gondwana assembly (Cambrian), but remanence was only locked in afterward, in successive cooling events during the Early Middle Ordovician. This is supported by the carbonates' paleomagnetic pole positions compared to Gondwana's apparent polar wander path, and the absence of reversals, contrasting with the high reversal frequency of the Late Ediacaran/Cambrian.

Effective removal of bisphenol A (BPA) from water using a goethite/activated carbon composite

This study focuses on microstructure, chemistry, and patina characterisation of eleven archaeological bronze artefacts from two contexts of the Middle Tiber Valley (Viterbo, Central Italy). The samples were unearthed in the cistern at Spoletino (1st -4th century AD) and in the late Roman-early Medieval necropolis of Castel Sozzio (5th-7th century AD). They were analysed using optical microscopy (OM), micro-Raman spectroscopy (µ-Raman), Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM/EDS), and electrochemical investigations. OM explored corrosion products on the surfaces, highlighting mineralogical and structural heterogeneity of the patinas. SEM-EDS analysis showed the presence of binary (Cu-Sn) and ternary (Cu-Pb-Sn) alloys with minor and trace elements. The binary alloys were used for good hardness artefacts, and the ternary ones for those that required easy metal working. Selective enrichment and depletion of the alloying metals produced broad chemical variations and structural heterogeneity in the patinas. Micro-Raman spectroscopy revealed different corrosion products such as cuprite (Cu2O), lazurite (Na7Ca(Al6Si6O24)(SO4)(S3)·H2O), malachite (CuCO3Cu(OH)2), and phosgenite (Pb2Cl2CO3). The presence of lazurite in two samples was linked to sulphur-rich burial environments, while phosgenite was linked to the interactions with Cl and a CO2-rich burial environment. Metallurgical practices, such as slow cooling rates and lead segregation during casting, promoted mineralogical and structural heterogeneity in the patinas due to interactions with the burial environment, where decomposition of organic matter occurred. Electrochemical data permitted the estimation of the corrosion rates for all artefacts at remarkably low levels (0–0.1 mm/year), reflecting stable burial conditions and the protective nature of the patinas. These results suggest that the burial environments in the Middle Tiber Valley were non-aggressive, facilitating the development of layered patinas influenced primarily by oxygen and carbon dioxide from humus-rich soils, with a lesser contribution from salts.

Accelerated artificial aging of zinc oxide (ZnO)-based acrylic artists’ paint, filled with calcium carbonate (CaCO3) as an extender, was carried out for a total of 1963 h (~8 × 107 lux·h), with assessments at specific intervals. The total color difference ΔE* was <2 (CIELab-76 system) over 1725 h of aging, while the human eye notices color change at ΔE* > 2. Oxidative degradation of organic components in the paint to form volatile products was revealed by attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy, micro-Raman spectroscopy, and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). It appears that deep oxidation of organic intermediates and volatilization of organic matter may be responsible for the relatively small value of ΔE* color difference during aging of the samples. To elucidate the degradation pathways, principal component analysis (PCA) was applied to the spectral data, revealing: (1) the catalytic role of ZnO in accelerating photodegradation, (2) the Kolbe photoreaction, (3) the decomposition of the binder to form volatile degradation products, and (4) the relative photoinactivity of CaCO3 compared with ZnO, showing slower degradation in areas with a higher CaCO3 content compared with those dominated by ZnO. These results provide fundamental insights into formulation-specific degradation processes, offering practical guidance for the development of more durable artist paints and conservation strategies for acrylic artworks.

Several concrete structures show signs of deterioration resulting from internal chemical reactions, such as the alkali-silica reaction (ASR). It is well known that these swelling reactions occur in the presence of moisture, between some silica mineral phases present in the aggregates and the alkalis of the concrete, leading to the degradation of concrete structures and consequently compromising their safety. In most of the cases, rehabilitation, demolition or even rebuilding of such structures is needed and the effective costs can be very high. Volcanic rocks are commonly used as aggregates in concrete, and they are sometimes the only option due to the unavailability of other rock types. These rocks may contain different forms of silica that are deleterious to concrete, such as opal, chalcedony, cristobalite, tridymite and micro- to cryptocrystalline quartz, as well as Si-rich volcanic glass. Volcanic rocks are typically very finegrained and their constituting minerals are usually not distinguished under optical microscopy, thus leading to using complementary methods. The objective of this research is to find the more adequate analytical methods to identify silica phases that might be present in volcanic aggregates and cause ASR. The complementary methods used include X-Ray Diffraction (XRD), mineral acid digestion and Scanning Electron Microscopy with Energy Dispersive X-Ray Spectrometry (SEM/EDS), as well as Electron Probe Micro-Analysis (EPMA).

ABSTRACTThe Barra Velha Formation and other Aptian pre‐salt deposits record the history of the proto‐Atlantic basin and the rifting of Gondwana. Studies have sought to characterize the depositional environment of the basin with a focus on carbonate fabrics and magnesium silicate clays. However, the water chemistry and fluid sources in the basin, the silica cycle, and how the basin evolved over time are not fully constrained. Additionally, current understanding of the microbiota that inhabited this basin is incomplete because microfossils have rarely been identified in pre‐salt deposits, especially on the Brazilian margin. This study describes authigenic chert in the Barra Velha Formation that preserves distinct, organic‐rich structures and textures. The petrographic relationships between the chert and carbonate suggest that both formed as authigenic phases, but their formation was temporally decoupled. These relationships and δ30Si and δ18O data suggest that chert post‐dates the formation and subsequent dissolution of the carbonates, and may have formed from a different fluid. By characterizing the chert–carbonate paragenesis and mechanism of chert formation, this study provides new insights into the fluid sources and complexity of the basin. Together, the results of this research suggest that the chert precipitated as primary, authigenic phases after karstification of the carbonate from a newly introduced, low temperature, freshwater fluid that was chemically distinct from the lake water. The chert preserves organic matter that is compositionally and texturally distinct from the void‐filling bitumen associated with the classically studied carbonate facies. Based on the composition and morphologies of organic structures, this is likely primary organic matter and a morphologically diverse microfossil assemblage preserved in place at the time of chert formation. Thus, this early chert provides new insights into the water chemistry, fluid sources and silica cycle in the basin, and represents a unique taphonomic window that helps us characterize the pre‐salt basin microbiota.

Geochemistry of muds from a shallow restricted estuary, Australia

Geochemistry of the surface sediments of the Sulu and South China Seas