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The amount of As(III) adsorbed and the interfacial process are closely associated with the phase transformation of Schwertmannite (SCH). At present, studies on the adsorption characteristics of As(III) on SCH and the accompanying phase transformation process, especially the related mechanisms under the mediation of iron-reducing bacteria (FeRB) and sulfate-reducing bacteria (SRB), are limited in existing literature. With the help of continuous characterization, the adsorption behavior of As(III) on SCH was explored, as well as the transformation processes of SCH during these processes. The findings revealed that the SCH, synthesized by the KMnO4 oxidation and ethanol modification methods, exhibited excellent physical adsorption capacity for As(III) due to their increasing specific surface area and porosity. At room temperature (20°C), the saturation adsorption capacities of As(III) by M-SCH and Y-SCH reached 62.69 and 58.62 mg/g, respectively. Moreover, the generation and phase transformation of As(III)-bearing ferrihydrite were observed within a 60-min timeframe. It is the first time this phenomenon has been observed in such a short time, which is presumed to be an intermediate stage in the transformation of SCH into goethite. Furthermore, both FeRB and SRB could enhance the adsorption capacity of SCH for As(III). Comparatively, SRB has a more substantial impact on SCH's phase transformation. These insights are valuable for the practical application of SCH in treating As(III) pollution. [ABSTRACT FROM AUTHOR]

Mangroves provide fundamental ecosystem services; however, the growing impact of human activities has resulted in increased pollution pressure, such as chemical contaminants. The redox processes are major biogeochemical players in the fate of contaminants. We investigate the effects of the redox environment on As(V) and Cr(VI) adsorbed on goethite (i.e., Fe(III)‐oxide) over 40 days of incubation in columns containing mangrove soil subjected to seawater saturation cycles. Our spectroscopic data highlighted a less Fe(III)‐ordered arrangement on goethite over time; As(V) is strongly bound to goethite, which delayed until 20 days its remobilization and reduction to As(III). After 40 days, the goethite held ∼50% of the initial As, but it was 15% as As(III). On the other hand, Cr(VI) was desorbed almost completely in less than 10 days, and the residual Cr ions bound to goethite were almost totally converted to Cr(III). Our study stresses the importance of individual time‐dependence in evaluating chemical speciation changes among potential toxic elements in wetland systems, such as mangroves and artificial wetlands designed to water treatment or soil remediation. Core Ideas: The redox processes are major biogeochemical players in wetlands.Goethite surface changes to less‐ordered structure in mangrove soils.Fast Cr(VI) mobilization in mangrove soils, however, is reduced to Cr(III).Slow As(V) release in mangrove soils, however, is reduced to As(III). [ABSTRACT FROM AUTHOR]

The article discusses the presence of 'super-stable' interlayer organic carbon in soil clay minerals and its impact on soil carbon sequestration. Soil organic carbon plays a crucial role in the global carbon cycle, influencing climate change by regulating greenhouse gas concentrations. The study highlights the stability of mineral-associated organic carbon in soil, particularly in clay minerals like montmorillonite and vermiculite. The research suggests that interlayer organic carbon in clay minerals is universal and exhibits high stability, contributing to soil carbon sequestration. Further investigation is needed to understand the formation mechanisms and properties of interlayer organic carbon in soil clay minerals. [Extracted from the article]

Cobalt (Co) and nickel (Ni) are critical metals for modern renewable energy technologies as well as essential micronutrients for terrestrial plant health and marine primary production. Both metals are commonly surface-adsorbed onto and/or structurally-incorporated into iron (oxyhydr)oxide minerals, such as goethite (α-FeOOH), that are ubiquitously present in soils and sediments at the Earth's surface. In sub- and anoxic environments, aqueous ferrous iron (Fe(II)) generated from dissimilatory Fe(III) reduction can induce the recrystallization of goethite and subsequently influences the speciation and mobilization of associated metals, e.g., Co(III) being reduced to Co(II). While it is generally considered that divalent Co and Ni behave similarly at goethite-water interfaces, there lacks a direct comparison of their cycling through goethite in response to Fe(II)-catalyzed recrystallization. Here, under circumneutral anoxic conditions with and without addition of aqueous Fe(II), we performed batch reaction experiments on Co(II)-substituted goethite and Co(II) and Ni(II) sorption experiments on pure goethite. The redox state and coordination environment of Co associated with goethite were determined using high energy resolution fluorescence detected X-ray absorption spectroscopy at the Co K-edge, and the distribution of solid-bound Co and Ni in goethite following sorption was revealed by sequential dissolution. Our results show that substitution of Co(II) for Fe(III) in goethite has less negative feedback on Fe(II)-catalyzed recrystallization than Ni(II), which may be related to their differing structural distortions as evidenced by EXAFS. In the absence of Fe(II), aqueous Co(II) is more favourably adsorbed onto and incorporated deeper into goethite than Ni(II), suggesting that Co(II) is more structurally compatible with goethite. The presence of Fe(II) markedly enhances the structural incorporation of both Co(II) and Ni(II) as a result of goethite recrystallization, which in turn can be inhibited by the accumulation of metals at the mineral surface. Furthermore, structurally-incorporated Co(II) is more difficult to be released back into solution (i.e. sum of aqueous and extract fractions) than Ni(II) during Fe(II)-catalyzed goethite recrystallization. Overall, our work highlights the significant differences between Co(II) and Ni(II) in their cycling at goethite-water interfaces and intricate interplay with Fe(II)-catalyzed recrystallization. This improves our understanding of their mobilization and distribution in anoxic goethite-rich systems and can provide useful insights for their enrichment and extraction from natural and artificial laterites generated from the enhanced weathering of ultramafic mine tailings. [ABSTRACT FROM AUTHOR]

Samples of siliceous rocks of the Southern Kambalny Central Thermal Field (SKC) containing a unique ore mineralization were studied. Optical microscopy, scanning electron microscopy, X-ray microanalysis, X-ray diffraction, ICP-MS, and Raman spectroscopy were used in this study. High concentrations and a wide range of rare and rare-earth elements were found in siliceous rocks. Silicates (quartz, moganite, and opal-crystobalite/tridymite opal), oxides (hematite and anatase), hydroxides (goethite), carbonates (calcite with Fe and Mn impurities), sulfates (barite with Sr impurity and gypsum), sulfides (pyrite, marcasite, chalcopyrite, and chalcocite), phosphates (xenotime-Y, YPO4 with impurities of lanthanides, S, Ca, and As; berlinite, AlPO4 with the V impurity), and apatite were identified. Structures of anatase replacement by quartz often in association with pyrite were identified. The mineralization of SKC siliceous rocks reflects the physicochemical specificity of deep metal-bearing solutions. [ABSTRACT FROM AUTHOR]

Green rusts (GR) are mixed-valence iron (Fe) hydroxides which form in reducing redox environments like riparian and wetland soils and shallow groundwater. In these environments, silicon (Si) can influence Fe oxides' chemical and physical properties but its role in GR formation and subsequent oxidative transformation have not been studied starting at initial nucleation. Green rust sulfate [GR(SO4)] and green rust carbonate [GR(CO3)] were both coprecipitated from salts by base titration in increasing % mol Si (0, 1, 10, and 50). The minerals were characterized before and after rapid (24 h) aqueous air-oxidation by x-ray diffraction (XRD), scanning electron microscopy (SEM), Fe extended x-ray absorption fine structure spectroscopy (EXAFS), and N2-BET surface area. Results showed that only GR(SO4) or GR(CO3) was formed at every tested Si concentration. Increasing % mol Si caused decreased plate size and increased surface area in GR(CO3) but not GR(SO4). GR plate basal thickness was not changed at any condition indicating a lack of Si interlayering. Air oxidation of GR(SO4) at all % mol Si contents transformed by dissolution and reprecipitation into lepidocrocite and goethite, favoring ferrihydrite with higher % Si content. Air oxidation of GR(CO3) transformed into magnetite and goethite but increasing Si caused GR to oxidize while retaining its hexagonal plate structure via solid-state oxidation. Our results indicate that Si has the potential to cause GR to form in smaller particles and upon air oxidation, Si can either stabilize the plate structure or alter transformation to ferrihydrite. [ABSTRACT FROM AUTHOR]

We report the discovery of the first fossil of an Australian species of Pergidae, Baladi warru gen. et sp. n., found at McGraths Flat, a newly discovered Miocene Konservat‐Lagerstätte in central New South Wales. Using morphological data from the well‐preserved fossil, along with a previously published molecular dataset of 59 taxa and a newly generated molecular dataset for 8 taxa, we constructed a data matrix and generated the first chronogram for Pergidae that incorporates internal calibration points. Our data reveal that Baladi warru belongs to the subfamily Perginae and is closely related to the Australian genera Cerealces and Xyloperga (tribe Cerealcini). According to our analysis, the origin of Pergidae appears slightly younger than previously hypothesised; however, additional calibration points are needed for a more detailed age constraint. Furthermore, ancestral character reconstruction indicates four independent adaptations to toxic Myrtaceae as host plants, while biogeographic analyses suggest that sympatry followed by founder events were the primary processes shaping the current disjunct distribution of pergids. Two significant founder events correspond with transitions to utilising Myrtaceae as host plants. With the approval of the Mudgee Local Aboriginal Land Council, Wiradjuri words were used to name the newly described species. ‘Baladi’ means ‘saw’ and ‘warru’ means ‘wasp’. This name honours the Traditional Owners of the lands on which the fossil was collected. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of iron oxide nanostructures, specifically snowflake architecture, are investigated for their potential applications in electrochemical sensing systems. A Raman spectroscopy analysis reveals phase diversity in the synthesized powders. The pH of the synthesis affects the formation of the hematite (α-Fe2O3) and goethite (α-FeOOH). Scanning electron microscopy (SEM) images confirm the distinct morphologies of the particles, which are selectively obtained through recrystallization during the elongated reaction time. An electrochemical analysis demonstrates the differing behaviors of the particles, with synthesis pH affecting the electrochemical activity and surface area differently for each shape. Cyclic voltammetry measurements reveal reversible dopamine detection processes, with snowflake iron oxide showing lower detection limits than a mixture of snowflakes and cube-like particles. This research contributes to understanding the relationship between iron oxide nanomaterials' structural, morphological, and electrochemical properties. It offers practical insights into their potential applications in sensor technology, particularly dopamine detection, with implications for biomedical and environmental monitoring. [ABSTRACT FROM AUTHOR]

A systematic study on the dissolution in concentrated alkali of two volcanic ashes from Cameroon, denoted as DAR and VN, is presented here. One volcanic ash, DAR, was 2 wt% richer in Fe and Ca and 4 wt% lower in Si than the other, designated as VN. Such natural raw materials are complex mixtures of aluminosilicate minerals (kaersutite, plagioclase, magnetite, diopside, thenardite, forsterite, hematite, and goethite) with a good proportion of amorphous phase (52 and 74 wt% for DAR and VN, respectively), which is more reactive than the crystalline phase in alkaline environments. Dissolution in NaOH + sodium silicate solution is the first step in the geopolymerisation process, which, after hardening at room temperature, results in solid and resistant building blocks. According to XRD, the VN finer ash powders showed a higher reactivity of Al-bearing soluble amorphous phases, releasing Al cations in NaOH, as indicated by IPC-MS. In general, dissolution in a strong alkaline environment did not seem to be affected by the NaOH concentration, provided that it was kept higher than 8 M, or by the powder size, remaining below 75 µm, while it was affected by time. However, in the time range studied, 1–120 min, the maximum element release was reached at about 100 min, when an equilibrium was reached. The hardened alkali activated materials show a good reticulation, as indicated by the low weight loss in water (10 wt%) when a hardening temperature of 25 °C was assumed. The same advantage was found for of the room-temperature consolidated specimens' mechanical performance in terms of resistance to compression (4–6 MPa). The study of the alkaline dissolution of volcanic ash is, therefore, an interesting way of predicting and optimising the reactivity of the phases of which it is composed, especially the amorphous ones. [ABSTRACT FROM AUTHOR]

The aim of this study is to carry out a petrological and geotechnical study of the lateritic soils of Ngaoundal (Adamawa-Cameroon). Hence, geotechnical identification, X-ray difractometry, and chemical analysis (XRF) were used to characterize soils. Field investigations show that the average thickness of the lateritic layers is 1.3 m; the soils encountered are nodular with a silty/clay matrix. The dominant color is dark brown (7.5YR 5/6) with a lumpy structure and silty or clayey texture. Mineralogical analysis (XRD) and chemical data (XRF) show that these materials are made up of quartz (38.27%), goethite (13.98%), gibbsite (10.59%), kaolinite (8.62%), hematite (7.88%), magnetite (8.38%), anatase, and boehmite. These soils are silico-ferrugino-aluminous. Their silica/sesquioxide ratios correspond to those of true laterites. X-ray diffraction analysis of the soil samples revealed the absence of swelling clays. Geotechnical analyses indicate that these soils have specific weights between 2.580 and 2.648 g/cm3. The liquidity limits show an average of 54.5%, with an average plasticity index of 29.73%. According to the (HRB) classification, these soils belong to the class of silty/clayey gravels and sands known as A-2–7. The values for maximum dry density and optimum water content range from 2.040 to 2.188 g/cm3 and from 9.5 to 13.6% respectively. The CBR bearing capacity index shows values ranging from 78.0 to 95.1%, which proves that these materials belong to bearing capacity class S5. The geological and geotechnical data confirm that the Ngaoundal materials are suitable for road construction (sub-base and base layers). [ABSTRACT FROM AUTHOR]

The primary purpose of this study is to synthesize biochar (Fe-SB) derived from sucrose through hydrothermal carbonization coupling with goethite activation and utilize it as an adsorbent to remove methylene blue (MB). FTIR, SEM, and BET were used to analyze the biochar characterization. Factors affecting the adsorption of MB on Fe-SB, including temperature, pH, salt, and different water sources, were also meticulously investigated. SEM results indicate that the morphology of the biochar derived from sucrose has a spherical shape, and the goethite crystal has a needle-like structure that successfully deposits on the adsorbent. The specific surface area of Fe-SB is 568 m2/g and contains enormous functional groups of O–H, C = C, and C–O. In the condition of pH 8, Fe-SB had a maximum adsorption capability of 476.2 mg/g. The adsorption capacity of biochar for MB removal consists of various adsorption mechanisms. In conclusion, Fe-SB, a novel material, pinpoints a promising and environmentally friendly adsorbent for the removal of MB from aquatic environment. [ABSTRACT FROM AUTHOR]

Carbon fibers (CFs) are indispensable materials in our daily life. The excellent bearing capacity, remarkable dielectric property, ease of production, and corrosion resistance of CFRP composites distinguish them from all other options in addition to them, CFRPs may also shield from electromagnetic interference (EMI). In this study, two-layer CF reinforced epoxy composites reinforced with two different hematite (alpha- Fe2O3) and goethite (FeO(OH)) particle sizes of 50 nm and 45 μm (325 mesh) were produced using the manual lay-up method. Then, far field electromagnetic shielding effectiveness (SE) with 700 MHz - 6000 MHz range were examined. The maximum shielding effectiveness was determined to be at 5200 MHz with 39.28 dB for 5 wt.% FeO(OH), at 4700 MHz with 38.38 dB for 10 wt.% Fe2O3(325 mesh), at 3800 MHz with 37.15 dB for 15 wt.% Fe2O3(50 nm). [ABSTRACT FROM AUTHOR]

Aims: The application of cover crop residue is an important means in managing paddy soil. This study was to investigate the influences of minerals on the mineralization of organic matter and the community and necromass of microbes in paddy soils amended with cover crop residue. Methods: 13C-labelled cover crop residue (Astragalus sinicus L.) was prepared using a pulse labeling method. The mineralization of cover crop residue and native soil organic matter and the community and necromass of microbes in two flooded paddy soils amended with or without illite, goethite and ferrihydrite was investigated by incubation experiments. The released CO2/CH4 was analyzed by gas chromatography. Amino sugar was used as the biomarker of microbial residue carbon. Soil microbial communities were analyzed by high-throughput sequencing and quantitative polymerase chain reaction. Results: Illite, goethite and ferrihydrite significantly decreased the amounts of both CO2 and CH4 emissions from native soil organic carbon in both paddy soils. Moreover, the inhibition efficiency followed the same sequence of ferrihydrite > goethite > illite for both CO2 and CH4 emissions. However, ferrihydrite significantly stimulated the mineralization of cover crop residue in both paddy soils. The examined minerals, especially ferrihydrite, also tended to decrease bacterial and fungal abundance and diversity in both paddy soils. Moreover, the contents of both bacterial and fungal residue carbon were significantly decreased by the examined minerals in alkaline paddy soil. Conclusion: Examined minerals tended to decrease total mineralization of cover crop residue and native organic matter, the microbial abundance, diversity, and necromass in flooded paddy soils. [ABSTRACT FROM AUTHOR]

Fe(III) oxides were prepared as free nanoparticles and on DNA templates via the precipitation of Fe(III) salts with NaOH in the presence/absence of DNA. Through control of the pH and temperature, FeOOH and Fe2O3 were synthesised. The formation of templated materials FeOOH/DNA and Fe2O3/DNA was confirmed using UV-Vis absorption and FTIR spectra. The direct optical gap of Fe2O3/DNA was estimated as 3.2 eV; the absorption by FeOOH/DNA and Fe2O3/DNA at longer wavelengths is weaker, but consistent with indirect gaps near 2 eV. X-ray photoelectron spectra confirmed the presence of Fe(III) and DNA in the templated samples. Analysis of the X-ray diffraction patterns of both templated and non-templated FeOOH and Fe2O3 demonstrated that the materials were the α-FeOOH and α-Fe2O3 polymorphs with crystallite diameters of the DNA-templated materials estimated as 7.6 nm and 6.8 nm. Transmission electron microscopy showed needle-like crystals of both FeOOH and Fe2O3, but the Fe2O3 contains some globular structures. In contrast, the morphology of FeOOH/DNA and Fe2O3/DNA consists of needle-like crystallites of the respective oxides organised into complex dendritic structures with a length on the 10 μm scale formed by the DNA molecules. Finally, scanned conductance microscopy provided evidence for the conductivity of the FeOOH/DNA after alignment via molecular combing on an Si/SiO2 substrate. Fe2O3/DNA did not exhibit any detectable conductivity. [ABSTRACT FROM AUTHOR]

Fragment of Calama 009 L6 ordinary chondrite recovered in the Atacama Desert was chosen for a complex study of the bulk interior and the fusion crust by scanning electron microscopy (SEM) with energy‐dispersive spectroscopy (EDS), X‐ray diffraction (XRD), magnetization measurements, and Mössbauer spectroscopy. SEM demonstrated the presence of Fe‐Ni‐Co grains, troilite and chromite inclusions in both the bulk interior and the fusion crust as well as many veins with ferric compound. EDS showed variations in the Ni concentration within the metal grains and within one metal phase in the grain. XRD revealed some differences in the contents of various phases in the bulk interior and in the fusion crust. XRD indicated the presence of magnesioferrite in the fusion crust as well as the formation of goethite nanoparticles with the mean size of 9 nm in both the bulk interior and the fusion crust. Magnetization measurements demonstrated the ferrimagnetic–paramagnetic phase transition in chromite at 44 K and low values of the saturation magnetization moments (6.46 and 3.26 emu g−1 at 100 K) for the bulk interior and the fusion crust, respectively, due to the lack of Fe‐Ni‐Co alloy as a result of weathering. The Mössbauer spectra of the bulk interior and the fusion crust showed some differences in the number and relative areas of spectral components. The revealing of the Mössbauer spectral components related to 57Fe in the M1 and M2 sites in olivine and orthopyroxene as well as determining the Fe2+ occupations of these sites from XRD permitted us to estimate the temperature of equilibrium cation distribution for these silicates which are (i) 662 K (XRD) and 706 K (Mössbauer spectroscopy) for olivine and (ii) 893 K (XRD) and 910 K (Mössbauer spectroscopy) for orthopyroxene. [ABSTRACT FROM AUTHOR]

This study aims to expand on existing connections between magnetic minerals and hydrocarbons within petroleum systems. Previous studies have focussed on single-source petroleum systems whereas this study, for the first time, analyses a multi-source petroleum system to investigate potential correlations between different kerogen type source rocks and magnetic minerals. To do this, the study investigates the magnetic mineral characteristics of the Inner Moray Firth (IMF), UK North Sea, through room-, low- and high-temperature techniques, and correlates this to published basin and petroleum systems modelling results that show a three-source hydrocarbon mix. Magnetic mineral analysis identifies extensive evidence for magnetite, goethite and siderite, alongside more minor lepidocrocite and iron sulphides. Although we find that magnetite is ubiquitous within the IMF, its abundance is relatively low, and, in contrast, the relatively magnetically weak goethite is more likely the most abundant magnetic mineral throughout the IMF. In agreement with previous studies, we find magnetic enhancement at oil-water contacts (OWCs); however, here, we identify two different magnetic enhancement processes at OWCs in wells, which are dependent on the amount of sulphur available in the local environment. Wells with low levels of sulphur have increasing levels of magnetite towards the OWC, with the magnetic enhancement occurring at the top of the water-saturated section. Sulphur-rich environments display an increase in iron sulphides near the OWC at the bottom of the oil-saturated sediments. Additionally, we confirm the presence of siderite as indicator of upward vertical migration. Combining with petroleum system model predictions, we find direct links between iron hydroxide presence and Type I and II–III kerogen source rocks, and iron sulphide presence with Type II kerogen source rocks. This study shows the potential for further utilization of magnetic mineral analysis within hydrocarbon exploration and petroleum system definition. [ABSTRACT FROM AUTHOR]

Jarosite, a prominent mineral in oxidised acid sulfate soil, is known to sorb and incorporate a variety of elements, including Al. However, to understand the role that jarosite plays in regulating element cycles, it is crucial to understand the stability and transformation pathways of jarosite in an acid sulfate soil under dynamic biogeochemical conditions. In this study, we observed the transformation of unsubstituted jarosite and Al-substituted jarosite, collectively referred to as 'jarosite', in an acid-sulfate rice paddy topsoil and subsoil from Thailand. Jarosite was incubated in flooded paddy topsoils and subsoils for up to sixteen weeks, both in laboratory mesocosms and in the field, using bags made of polyethylene terephthalate mesh. One set of mesh bags contained jarosite that was not mixed with any other minerals, and referred to as 'pure mineral' incubations. Mineral transformations occurred under the influence of the soil porewater only and were primarily followed by X-ray diffraction analysis. A parallel set of mesh bags contained soil with 57Fe-labelled jarosite enrichment (Fe enriched in soil by a factor of 1.3 but 57Fe enrichment factor of 12.5–13.6), which allowed jarosite transformation to occur in close association with the soil matrix. Mineral transformations in 57Fe-jarosite-enriched soil were followed using 57Fe Mössbauer spectroscopy. In laboratory mesocosms and in the field, jarosite transformed most quickly in topsoil, whereas jarosite underwent limited transformation in subsoils, especially in laboratory mesocosms where Fe reduction was slow. The chemical environment around the jarosite affected the outcome of the transformation processes. Crystalline Fe oxyhydroxides, such as goethite, dominated the products in mesh bags where jarosite was not mixed with soil, whereas short-range-ordered or non-mineral Fe phases, such as Fe(II) sorbed to mineral surfaces or complexed with organic ligands, were dominant transformation products of jarosite when mixed in soil. Furthermore, Al substitution in jarosite caused contrasting effects in mesh bags containing pure minerals or mineral-enriched soil. Aluminium substitution slowed the transformation of jarosite in pure mineral mesh bags, but Al-substituted and unsubstituted jarosite showed similar transformation rates and pathways when incubated as a mixture with soil. The contrasting rate of transformation in topsoil and subsoil, the contrasting products of transformation in pure mineral mesh bags and 57Fe-jarosite-enriched soil, and the contrasting effect of Al substitution in pure mesh bags or jarosite-enriched soil, all demonstrate that the rate and products of jarosite transformation are defined by a balance between competitive transformation pathways that affect the transforming minerals. [ABSTRACT FROM AUTHOR]

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The scarce carbonate record on the Martian surface is one of the fundamental unsolved issues for paleoclimate and environmental evolution. Whether carbonates first formed and then dissolved due to a transition in global environments or whether Mg–Fe carbonates never extensively formed due to geochemical kinetics thresholds remains unknown. In this study, we experimentally examined the preservation potential of siderite in Mars‐relevant fluids, including ultrapure water, H2O2, NaClO4, NaClO3, NaCl, Na2SO4, NaHCO3, and Na2SiO3 solutions, at 277 K. The effects of the water/rock ratio at WR10 and WR100 on dissolution rates were also investigated. We found that siderite dissolution and subsequent oxidation and hydrolysis of leached Fe did not substantially acidify the solutions. The siderite dissolved relatively rapidly in the chloride and chlorate solutions and slowly in the silica or bicarbonate solutions. In a circum‐neutral to slightly alkaline aqueous environment with oxidative species, the mobility of leached Fe was limited, leading to the formation of goethite or lepidocrocite, which clustered on the siderite surface. The longest lifetime of 1‐mm siderite grains was found in the Na2SiO3 solution at WR100, which was estimated to range from 198 ka to 198 Ma. Water‐limited, silica‐rich, and oxidative aqueous environments benefit siderite preservation on the Martian surface. Our results support that the lack of voluminous siderite on Mars may be primarily due to the inhibition of its formation rather than alteration and dissolution after its presence, consistent with the recent detection of Mg–Fe carbonate at Gale Crater and Jezero Crater. Plain Language Summary: Despite the predominant carbon dioxide atmosphere, the distribution of carbonate outcrops on Mars detected to date is very limited. The discrepancy between the CO2‐dominant atmosphere and scarce carbonate records is one of the key issues for understanding the paleoclimate and environmental evolution of Mars. We experimentally investigated the preservation potential of siderite in eight Mars‐relevant fluids under water‐limited versus water‐abundant scenarios at 277 K. We found that water‐limited conditions, silica‐rich environments, and the presence of oxidants in aqueous environments generally benefit siderite preservation. The longest lifetime of 1‐mm siderite grains is present in silica‐rich solutions, estimated to range from 198 ka to 198 Ma. In a neutral to alkaline aqueous environment with oxidative species, the mobility of leached iron is limited, and the Fe precipitates are mainly in the form of goethite or lepidocrocite, accumulating on the siderite surface. Martian aqueous environments can efficiently preserve siderite. Therefore, the lack of voluminous siderite on Mars may be because siderite was never extensively formed rather than altered and dissolved after its presence. Key Points: Siderite dissolves relatively fast in chloride‐ and chlorate‐fluids and slowly in silica‐ and bicarbonate‐fluidsWater‐limited, silica‐rich, and oxidative aqueous environments favor siderite preservation on the Martian surfaceThe scarcity of voluminous siderite on Mars may be due to the inhibition of its formation rather than its dissolution after its presence [ABSTRACT FROM AUTHOR]

Background Aims and Methods Results Conclusions Fe and Al oxyhydroxides are well‐known phosphorus (P)‐retaining minerals in soils. Little information is available regarding the relevance of clay minerals for the sorption of P in mixed oxyhydroxide–clay mineral systems and pH effects on P sorption partitioning.We wanted to investigate pH effects on P sorption partitioning between Fe oxyhydroxides and high‐activity clay minerals in mixed‐mineral systems. We quantified the relative contribution of ferrihydrite or goethite versus Al‐saturated montmorillonite (Al‐MT) to the retention of orthophosphate (oPO4) and inositol hexakisphosphate (IHP) at different pH values (3–6). We combined the analysis of P solution concentration changes with the quantification of P bound to Fe(III) versus Al in the Fe oxyhydroxide/Al‐MT mixtures by X‐ray absorption near‐edge structure (XANES) spectroscopy.Orthophosphate was preferentially retained by ferrihydrite, compared to Al‐MT at pH 3–6. The opposite was observed for goethite at low P solution concentrations. The contribution of Al‐MT versus Fe oxyhydroxides to oPO4 retention increased with pH. This is attributed to a speciation change of clay‐adsorbed Al from monomeric Al3+ to polynuclear Al hydroxy species. IHP was predominantly retained by Al‐MT rather than ferrihydrite at pH 3–6, probably by the formation of adsorbed and surface‐precipitated Al phytate complexes.Synchrotron‐based XANES spectroscopy allows for quantifying P adsorbed to co‐existing pedogenic Fe(III) oxyhydroxides versus Al‐MT in mixed‐mineral systems. Soil P retention partitioning to these minerals depends on (1) dominating P form (oPO4, IHP), (2) relative abundance of high‐activity clay minerals, short‐range ordered and crystalline Fe oxyhydroxides, and (3) solution pH. [ABSTRACT FROM AUTHOR]

Aims Biofilms are complex microbial cell aggregates that attach to different surfaces in nature, industrial environments, or hospital settings. In photovoltaic panels (PVs), biofilms are related to significant energy conversion losses. In this study, our aim was to characterize the communities of microorganisms and the genes involved in biofilm formation. Methods and results In this study, biofilm samples collected from a PV system installed in southeastern Brazil were analyzed through shotgun metagenomics, and the microbial communities and genes involved in biofilm formation were investigated. A total of 2030 different genera were identified in the samples, many of which were classified as extremophiles or producers of exopolysaccharides. Bacteria prevailed in the samples (89%), mainly the genera Mucilaginibacter, Microbacterium, Pedobacter, Massilia , and Hymenobacter. The functional annotation revealed >12 000 genes related to biofilm formation and stress response. Genes involved in the iron transport and synthesis of c-di-GMP and c-AMP second messengers were abundant in the samples. The pathways related to these components play a crucial role in biofilm formation and could be promising targets for preventing biofilm formation in the PV. In addition, Raman spectroscopy analysis indicated the presence of hematite, goethite, and ferrite, consistent with the mineralogical composition of the regional soil and metal-resistant bacteria. Conclusions Taken together, our findings reveal that PV biofilms are a promising source of microorganisms of industrial interest and genes of central importance in regulating biofilm formation and persistence. [ABSTRACT FROM AUTHOR]

Gold, along with other highly siderophile elements, is hosted by Fe-Ni sulfide phases within peridotites and mantle melts. In this context, the lithospheric mantle emerges as a principal reservoir, providing materials crucial for the inception, augmentation, conveyance, and genesis of auriferous CO2-rich mantle fluids. EPMA and laser ablation ICP-MS data, integrated with petrographic and SEM studies, were used to assess the transfer of base and precious metals into the Earth's crust, discerning between inputs from subduction-related processes and post-formation metasomatism. The study focuses on sulfide minerals in serpentinized peridotites of the Abu Dahr ophiolite in the Eastern Desert of Egypt. Originating in a supra-subduction setting during the Neoproterozoic era, the Abu Dahr peridotites underwent serpentinization and contain discrete sulfide minerals, including pentlandite, nickeloan pyrrhotite, millerite, chalcopyrite, and violarite. The uneven distribution of calcite ± magnesite ± serpentine veins throughout the host ophiolitic rocks reflects the intricate interplay of serpentinization and carbonation, as fO2 and fCO2 conditions fluctuated. Geochemical data of the host rocks reveal a progressive geochemical evolution marked by concurrent silicification and carbonate alteration, driven by the interaction of ultramafic rocks with hydrothermal fluids, ultimately leading to the extensive silicification and formation of birbirite. The ICP-MS data show that pentlandite contains up to 6.11 ppm of Au, pyrrhotite up to 0.41 ppm, millerite 0.34 ppm, and violarite 0.12 ppm. The gold concentration in pentlandite is significantly higher than in pyrrhotite, millerite, and violarite, which exhibit lower but detectable levels of Au. Desulfurization reactions of sulfide minerals during progressive serpentinization triggered the release and redistribution of Au as well as base metals and highly siderophile elements. Published thermodynamic modeling at temperatures below 300 °C and pressures of 50 MPa closely replicates the mineral assemblage observed in the Abu Dahr ophiolites, including sulfide assemblages and variations in major elements such as Mg and Fe. This suggests that the serpentinization process, along with associated hydrothermal fluids, played a crucial role in the mobilization and redistribution of gold, particularly affecting its incorporation into secondary sulfides. The mobilization of Au and other highly siderophile elements during serpentinization occurred in an environment marked by strong oxidation, as indicated by the presence of acicular antigorite, magnetite, millerite, and goethite intergrowths. [ABSTRACT FROM AUTHOR]

Sediment microbial fuel cells (SMFC) are bioelectrochemical systems that can use different wastes for energy production. This work studied the implementation of nanoparticles (NPs) of α-FeOOH (goethite, which is well-known as a photoactive catalyst) in the electrodes of an SMFC for its potential use for dye removal. The results obtained demonstrate the feasibility of the NPs activation with the electrical potential generated in the electrodes in the SMFC instead of the activation with light. The NPs of α-FeOOH were synthesized using a hydrothermal process, and the feasibility of a conductive bio-composite (biofilm and NPs) formation was proven by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and electrochemical techniques. The improvement of the power density in the cell was more than twelve times higher with the application of the bio-composite, and it is attributed mostly to the presence of NPs. The results also demonstrate the NPs effect on the increase of the electron transfer, which resulted in 99% of the COD removal. The total electrical energy produced in 30 days in the SMFC was 1.2 kWh based on 1 m2 of the geometric area of the anode. The results confirm that NPs of α-FeOOH can be used to improve organic matter removal. Moreover, the energy produced due to its activation through the potential generated between the electrodes suggests the feasibility of its implementation for dye removal. [ABSTRACT FROM AUTHOR]

The total content, forms, and mineralogy of iron compounds in soils of forest-steppe, steppe, and semidesert zones of a large territory from the central chernozem regions to the Caspian lowland and from the Southern Urals to the Kerch Strait are studied. The study covers Chernozems (n = 40), Kastanozems (n = 15), Solonetzes (n = 7), and Calcisols (n = 7). Our results demonstrate the specific features in the distribution of total iron content, mass balance (τFe, Zr), forms of iron compounds, magnetic susceptibility (χ), and mineralogy in soil profiles. The distribution of τFe, Zr in the studied soils reflects the processes and conditions of soil formation, as well as specific lithological features. For a more comprehensive understanding of the transformation of iron compounds in steppe soils, particle-size fractions (<2, 2–5, 5–10, and 10–50 μm) have been analyzed by Mössbauer spectroscopy and magnetic susceptibility methods for Luvic Chernozem, Haplic Kastanozem, Haplic Kastanozem (Endosalic, Cambic), and Luvic Calcisol (Endosalic). In the clay fraction, a large share of Fe3+ is contained in highly dispersed oxides and hydroxides in a superparamagnetic state. In the humus-accumulative horizons of steppe soils, a decrease in the Fe2+ fraction in aluminosilicates caused by weathering is recorded. The observed correlation of the goethite/(hematite + goethite) ratio in humus-accumulative soil horizons with climatic parameters suggests the possibility to apply it for future paleoclimatic reconstructions. Mössbauer spectroscopy shows a significant increase in the content of nonsilicate iron in the humus-accumulative horizons of steppe soils as compared with the soil-forming material, which is an important confirmation for the formation of iron oxides during pedogenesis. A comparison of the methods for assaying nonsilicate iron in soils (Mössbauer spectroscopy and Mehra–Jackson extraction) demonstrates considerable differences in the results, suggesting that the chemical technique underestimates the amount of free iron forms. [ABSTRACT FROM AUTHOR]

[Display omitted] Reducing iron by hydroxylamine (HA) can promote the generation of reactive oxygen species (ROS) in the Fenton reaction and play a crucial role in the degradation of organic pollutants. However, the performance of this system at wider environmental thresholds is still not sufficiently understood, especially in the highly alkaline environments resulting from human activities. Here, we assessed the impact of solution pH on organic pollutant degradation by goethite with the addition of HA and H 2 O 2. The solid phase variation and ROS generation were analyzed using Mössbauer spectroscopy, X-ray absorption near edge structure spectroscopy, and electron paramagnetic resonance analysis. This study found that under alkaline conditions, the system can continuously scavenge organic pollutants through oxygen-mediated generation of free radicals. At lower pH levels, organic pollutant decomposition, exemplified by the breakdown of bisphenol A (BPA), is primarily driven by the Fenton reaction facilitated by iron. As pH increases, hydroxyl radical (•OH) production decreases, accompanied by decreased BPA removal efficiency. However, the removal efficiency of BPA increased significantly at pH > 9. At pH 12, the removal of BPA exceeded that of the acidic condition after one hour, which is consistent with observations in soil system studies. Unlike the Fenton reaction, which is not sensitive to oxygen content, the removal of BPA under alkaline conditions occurs only under aerobic conditions. H 2 O 2 is hardly involved in the reaction, and the depletion of HA becomes a critical factor in the decomposition of BPA. Importantly, in contrast to acidic conditions, where the dramatic decomposition of BPA occurs mainly in the first 10 min, the decomposition of BPA under alkaline conditions continued to occur over the 2 h of observation until complete removal. For natural systems, the remediation of pollutants depends more on the active time of ROS than on their reactivity. Therefore, this idea can reference pollution remediation strategies in anthropogenically disturbed environments. [ABSTRACT FROM AUTHOR]

This article demonstrates the important roles of silicon in the nonclassical crystallization of goethite by particle attachment during limpet teeth formation and their structure–mechanical property relationship. [Display omitted] The intricate organization of goethite nanorods within a silica-rich matrix makes limpet teeth the strongest known natural material. However, the mineralization pathway of goethite in organisms under ambient conditions remains elusive. Here, by investigating the multi-level structure of limpet teeth at different growth stages, it is revealed that the growth of goethite crystals proceeds by the attachment of amorphous nanoparticles, a nonclassical crystallization pathway widely observed during the formation of calcium-based biominerals. Importantly, these nanoparticles contain a high amount of silica, which is gradually expelled during the growth of goethite. Moreover, in mature teeth of limpet, the content of silica correlates with the size of goethite crystals, where smaller goethite crystals are densely packed in the leading part with higher content of silica. Correspondingly, the leading part exhibits higher hardness and elastic modulus. Thus, this study not only reveals the nonclassical crystallization pathway of goethite nanorods in limpet teeth, but also highlights the critical roles of silica in controlling the hierarchical structure and the mechanical properties of limpet teeth, thus providing inspirations for fabricating biomimetic materials with excellent properties. [ABSTRACT FROM AUTHOR]

This paper presents the results of a selective flocculation/magnetic separation study performed with a sample of iron ore slime from the desliming stage of the industrial flotation circuit of a mine in the southern region in the Quadrilátero Ferrífero-Brazil that was discarded in a tailings dam. Zeta potential measurements of pure minerals previously identified in the sample (goethite = 52.4%, hematite = 26.2%, quartz = 12.3%, kaolinite = 8.2%, and others = 0. 9%) were evaluated to assess the influence of the reagents used (sodium hexametaphosphate – SHMP (dispersant)) and flocculants (corn starch, nonionic polyacrylamide – P2500 and cationic polyacrylamide – P806)) on their surface properties and consequently on the stability of suspensions of the slime and of the pure minerals individually, aiming to establish conditions for selective separation between Fe-bearing minerals (goethite and hematite) and gangue minerals (quartz and kaolinite) in the subsequent magnetic separation step. At pH 10 and a 25 mg/L dosage of SHMP, a higher Fe recovery was verified with starch (2000 g/t) in relation to nonionic and cationic polyacrylamides, and similar Fe contents in all dosages tested of the flocculants. [ABSTRACT FROM AUTHOR]

The synthesis of a strontium hexaferrite magnet is studied using in situ synchrotron powder X‐ray diffraction (PXRD) with a 16‐ms time resolution. The precursor material is cold compacted shape‐controlled goethite and strontium carbonate. The time evolution of the phases is modeled with sequential Rietveld refinements revealing that strontium hexaferrite forms within seconds at ≈1173 K. Texture analysis is performed on selected PXRD frames throughout the experiment, and the preferred orientation introduced by cold‐pressing goethite prevails through the iron oxide phase transitions (goethite → hematite → strontium hexaferrite). Electron backscatter diffraction (EBSD) data on the final pellet confirms the preferred orientation observed with PXRD. The resulting magnet has respectable magnetic properties, considering the simplicity of the preparation method, with an energy product (BHmax) of 18.6(8) kJ m−3. [ABSTRACT FROM AUTHOR]

• Rice straw-derived dissolved organic matter (DOM) included four main components. • The presence of goethite significantly promotes the straw decomposition process. • OM's adsorption capacity for Cd increased with the straw decomposition time. • The presence of minerals promoted the OM's adsorption capacity and affinity of Cd. • Surface precipitation and complexation dominant Cd adsorption by OM. Organic matter (OM) derived from the decomposition of crop residues plays a key role as a sorbent for cadmium (Cd) immobilization. Few studies have explored the straw decomposition processes with the presence of minerals, and the effect of newly generated organo-mineral complexes on heavy metal adsorption. In this study, we investigated the variations in structure and composition during the rice straw decomposition with or without minerals (goethite and kaolinite), as well as the adsorption behavior and mechanisms by which straw decomposition affects Cd immobilization. The degree of humification of extracted straw organic matter was assessed using excitation-emission matrix (EEM) fluorescence and Ultraviolet-visible spectroscopy (UV-vis), while employing FTIR spectroscopy and XPS to characterize the adsorption mechanisms. The spectra analysis revealed the enrichment of highly aromatic and hydrophobic components, indicating that the degree of straw decomposition and humification were further intensified during incubation. Additionally, the existence of goethite (SG) accelerated the humification of OM. Sorption experiments revealed that the straw humification increased Cd adsorption capacity. Notably, SG exhibited significantly higher adsorption performance compared to the organic matter without minerals (RS) and the existence of kaolinite (SK). Further analysis using FT-IR spectroscopy and XPS verified that the primary mechanisms involved in Cd immobilization were complexion with —OH and —COOH, as well as the formation of Cd-π binds with aromatic C=C on the surface of solid OMs. These findings will facilitate understanding the interactions of the rice straw decomposing with soil minerals and its remediation effect on Cd-contaminated farmland. [Display omitted] [ABSTRACT FROM AUTHOR]

Deep-sea mud shows tremendous resource potential for rare earth elements (REEs) and its formation is closely associated with sea-floor hydrothermal activities. Iron (oxyhydr)oxides link the sources and sinks of REEs in sea-floor hydrothermal systems. However, the complexation mechanisms of REEs on iron (oxyhydr)oxides have not been well understood yet. In this study, by using the first principles molecular dynamics technique, we first calculated the pK a 's of surface groups on goethite (1 1 0) surface at elevated temperatures relevant to sea-floor hydrothermal systems and then evaluated the complexation structures and free energies of REEs on goethite (1 1 0) and (0 1 0) surfaces using the method of constraint by taking Sc3+, Y3+, and La3+ as model REE cations. The results show that REE complexation occurs in mildly acidic to neutral conditions. The most thermodynamically stable complexes of REEs are bidentate complexes on two neighboring FeOH sites on goethite (1 1 0) surface and tridentate complexes on two neighboring FeOH sites plus one Fe 2 OH site on goethite (0 1 0) surface. Sc3+ complexes match the goethite lattice and can be incorporated into the lattice. The stabilities of REE complexes increase with the distance from hydrothermal vents. Complexation of Y3+ is less favored on goethite compared to other REEs whereas Sc3+ prefers complexation on goethite (0 1 0) surface and La3+ exhibits similar stabilities on both (0 1 0) and (1 1 0) surfaces. The derived atomic level complexation mechanisms would be helpful for the interpretation of experimental data and the prediction of REEs' behavior in the sea-floor. The findings presented here provide valuable insights into REEs fractionation and enrichment in deep-sea muds. [ABSTRACT FROM AUTHOR]

Scandium (Sc) is a rare element that finds uses in modern technologies. Thermodynamic properties of Sc phases could help in the development of innovative technologies to extract Sc from mining waste. In this work, we investigated the FeOOH–ScOOH solid solution with the goethite structure. The end members and five intermediate compositions were synthesized and characterized. The lattice parameters show that the solid solution is non-ideal, with complex behavior induced by the Fe–Sc substitution. The excess unit-cell volume deviates negatively for the Sc-rich region, and positively for the Fe-rich region from the ideal behavior (Vegard's law). Enthalpies of dissolution were determined by acid-solution calorimetry in 5 mol · dm - 3 HCl at T = 343.15 K. Enthalpies of mixing ( Δ mix H ), calculated from the experimental data, are small and positive. The available data allow for fitting the data as Δ mix H = W x (1 - x) , with the mixing parameter W = 15.2 ± 1.0 kJ · mol - 1 . Using Δ f G o of ScOOH from earlier literature, we calculated a Lippmann diagram that shows that Sc should strongly partition into the aqueous phase upon goethite precipitation. The field observations from lateritic profiles show that Sc is primarily harbored by goethite via adsorption. It seems that under weathering conditions, thermodynamically driven partitioning of Sc 3 + into the aqueous phases and its subsequent adsorption onto goethite surfaces controls the mobility of Sc in the weathering profiles. [ABSTRACT FROM AUTHOR]

• Activated persulfate systems with Fe-based catalysts in laboratory are reviewed. • The persulfate system activated by iron ore catalysts was introduced. • The advantages and disadvantages of two types of catalysts were discussed. • The mechanism of removing organic pollutants was evaluated. • The research direction of Fe-based catalyst/PS/ pollutant system was proposed. Heterogeneous iron-based catalysts have drawn increasing attention in the advanced oxidation of persulfates due to their abundance in nature, the lack of secondary pollution to the environment, and their low cost over the last a few years. In this paper, the latest progress in the research on the activation of persulfate by heterogeneous iron-based catalysts is reviewed from two aspects, in terms of synthesized catalysts (Fe0, Fe 2 O 3 , Fe 3 O 4 , FeOOH) and natural iron ore catalysts (pyrite, magnetite, hematite, siderite, goethite, ferrohydrite, ilmenite and lepidocrocite) focusing on efforts made to improve the performance of catalysts. The advantages and disadvantages of the synthesized catalysts and natural iron ore were summarized. Particular interests were paid to the activation mechanisms in the catalyst/PS/pollutant system for removal of organic pollutants. Future research challenges in the context of field application were also discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

Goethite (α-FeOOH), a vital water- and hydrogen-bearing natural mineral, is extensively distributed on the Earth's surface and probably in the lower mantle. Laboratory measurements of its phase transition and sound velocities provide crucial data for a more rational understanding of the deep-water transportation and physical properties of the Earth's interior. Herein, the Hugoniot equation of state and sound velocities of natural goethite up to around 15 GPa are measured by dynamic compression. The discontinuities pertinent to the density and sound velocities of goethite are observed at 7.1 (2) GPa, in which a solid–solid phase transition occurs from α- (Pbnm) to ɛ-FeOOH (P21nm). Through this structural phase transition, the longitudinal and shear wave velocities in order, enhance by about 5% and 12%. We suggest that changes in the sound velocity due to the FeOOH phase transition may contribute to the discontinuity in the subduction zones. [ABSTRACT FROM AUTHOR]

Technogenic soils result from the oxidation and hydrolysis of minerals in rocks extracted from mining areas and brought to the surface. Diagnostics of such soils involve a set of detailed tests, which can be both time-consuming and costly. In this study, the pH of sulfate soils in the Kizel Coal Basin (Perm krai, Russia) was determined using hydrogen peroxide. Particularly, the soils affected by runoff from rock dumps, outflow, and mine water discharge were examined. The findings showed pH-H2O2 below 2.5 in certain horizons, indicating the presence of sulfides. Additionally, the soils exhibited significantly higher levels of mobile sulfur and iron, total sulfur, and sulfates, ranging from tens to hundreds of times above the background content. XRD analysis revealed that the soils contained goethite and jarosite, thereby confirming the efficacy of pH determination with hydrogen peroxide for the prompt diagnostics of acid sulfate soils.

The residue generated during the production process of alumina, known as red mud, is a type of solid waste. The engineering properties of red mud can be significantly enhanced through the modification and solidification using inorganic materials. This study primarily utilized red mud as the raw material, supplemented with fly ash, lime, and clay, to conduct a solidification experiment of red mud. Orthogonal tests with three factors of two ash ratio (ratio of lime to fly ash), two ash content (total lime and fly ash), and red mud types were designed to study the changes of different ratios and maintenance conditions, etc., on the engineering properties of red mud. In addition, the micro-mechanisms of modified red mud were investigated by means of XRF, XRD, SEM and EDX. The results show that for optimum moisture content, red mud types are the most important influencing factor and for maximum dry density, two ash content is the most important influencing factor. For strength characteristics, the optimum two ash ratio was 1.5:1, the optimum two ash content was 50%, and the optimum red mud types were 70% CRM (red mud made of Chalco Shandong Co., Ltd) mixed with 30% clay. The addition of lime, fly ash, and clay improves the temperature shrinkage coefficient of the red mud. Through the analysis of microscopic composition and structure, it can be seen that goethite (α-FeO(OH)) and magnetite (γ-Fe2O3) in the red mud reacted with the modified materials to generate crystalline aluminosilicate and amorphous hydrated silicate gel, and these products together with the original calcium carbonate (CaCO3), tricalcium aluminate (Ca3Al2O6) and garnet (Ca3TiFeSi3O12) in the red mud which have certain strengths enhance the structural strength of the modified red mud. The optimum ratio obtained from the combined test results was lime: fly ash: CRM = 30:20:50. Therefore, using lime, fly ash and clay as modified materials can greatly enhance the engineering properties of red mud and realise the resourceful use of red mud. [ABSTRACT FROM AUTHOR]

Chiton articulatus is a species of mollusk living in the tropical Pacific intertidal rocky shores of Mexico. This species feeds on solid waste organic sources, including hard crustose algae that grow on rocky substrates, by grazing on them with its radula, a flexible chitinous membrane lined with mineralized major lateral teeth. In this study, the composition, morphology, and resulting mechanics of the mature teeth of this species, which have yet to be examined, are revealed. The results show the presence of multiphasic mature teeth, each consisting of aligned hard magnetite nanoparticles on the leading edge of the tooth underneath which are magnetite lamellae, followed by goethite, lepidocrocite, and eventually hydroxyapatite near the trailing edge. This multiregional structure demonstrates a gradation in hardness as well as different microstructural features integrated with tough interfaces. The combination of these microstructural and phase arrangements results in an abrasion‐resistant tough structure with a self‐sharpening ability. The results of this work will help contribute to developing new bioinspired designs while also helping to understand the evolution and feeding habits of these intriguing invertebrates. [ABSTRACT FROM AUTHOR]

Manganese co-precipitated with goethite (Mn-FeOOH) is ubiquitous within (sub-)surface environments, which are considered one of the most important sinks for phosphorus pollution management. Accordingly, various mole ratios of Mn-FeOOHs are synthesized and characterized by XRD, FE-SEM, FTIR, BET, XPS, hysteresis loop, acid–base titration and zero potential. According to XRD and FESEM images, the substitution of Mn causes subtle alterations in the microstructure and crystal structure of goethite, and the morphology of Mn-FeOOHs is transformed from needle-shaped goethite to a short-rod-shaped rough surface with increasing Mn substitution. Based on the analysis of BET and acid–base titration, the substitution of Mn into goethite significantly improved the surface area, pore volume, surface properties and active sites of goethite, thereby establishing a theoretical basis for effective subsequent adsorption. Batch experiment results show that the removal rate of phosphate decreases with the increasing solution pH, indicating that acidic groundwater conditions are more conducive to the removal of phosphate. In addition, the adsorption of phosphate on Mn-FeOOHs is independent of ionic strength, indicating that the inner-sphere surface complexation predominated their adsorption behaviors. The isotherm experiment results showed that Mn-G15 exhibits the strongest adsorption capacity for phosphate at pH 5.5 and T = 318 K, with a maximum adsorption capacity of 87.18 mg/g. These findings highlighted the effect of Mn content on the fixation of phosphate onto Mn-FeOOHs from (sub-)surface environments in pollution management. [ABSTRACT FROM AUTHOR]

Constraining dust models to understand and quantify the effect of dust upon climate and ecosystems requires comprehensive analyses of the physiochemical properties of dust-emitting sediments in arid regions. Building upon previous studies in the Moroccan Sahara and Iceland, we analyse a diverse set of crusts and aeolian ripples (n=55) from various potential dust-emitting basins within the Mojave Desert, California, USA. Our focus is on characterizing the particle size distribution (PSD), mineralogy, aggregation/cohesion state, and Fe mode of occurrence. Our results show differences in fully and minimally dispersed PSDs, with crusts exhibiting average median diameters of 92 and 37 µm , respectively, compared to aeolian ripples with 226 and 213 µm , respectively. Mineralogical analyses unveiled strong variations between crusts and ripples, with crusts being enriched in phyllosilicates (24 % vs. 7.8 %), carbonates (6.6 % vs. 1.1 %), Na salts (7.3 % vs. 1.1 %), and zeolites (1.2 % and 0.12 %) and ripples being enriched in feldspars (48 % vs. 37 %), quartz (32 % vs. 16 %), and gypsum (4.7 % vs. 3.1 %). The size fractions from crust sediments display a homogeneous mineralogy, whereas those of aeolian ripples display more heterogeneity, mostly due to different particle aggregation. Bulk Fe content analyses indicate higher concentrations in crusts (3.0 ± 1.3 wt %) compared to ripples (1.9 ± 1.1 wt %), with similar proportions in their Fe mode of occurrence: nano-sized Fe oxides and readily exchangeable Fe represent ∼1.6 %, hematite and goethite ∼15 %, magnetite/maghemite ∼2.0 %, and structural Fe in silicates ∼80 % of the total Fe. We identified segregation patterns in the PSD and mineralogy differences in Na salt content within the Mojave basins, which can be explained by sediment transportation dynamics and precipitates due to groundwater table fluctuations described in previous studies in the region. Mojave Desert crusts show similarities with previously sampled crusts in the Moroccan Sahara in terms of the PSD and readily exchangeable Fe yet exhibit substantial differences in mineralogical composition, which should significantly influence the characteristic of the emitted dust particles. [ABSTRACT FROM AUTHOR]

Terrestrial supergene goethites of known ages record information on changes in weathering conditions through time. Here we present a database of (U-Th)/He ages and U and Th contents of goethites from different weathering environments around the globe. By consolidating published data collected at four different laboratories and unpublished data collected at the Noble Gas Laboratory at Caltech, we aim to give an overview of the work carried out by geochronologists and geochemists in the last 20 years. The database contains 2597 (U-Th)/He ages of goethites from 10 countries; most of the ages come from Brazil and Australia. [ABSTRACT FROM AUTHOR]

Goethite is one of the most common minerals in iron ore, and is the main source of internal crystal water generated during the heating process of lump ore. To address this challenge, three measures are proposed: first, minimizing the decomposition of crystalline water upon the introduction of lump ores into the furnace; second, reducing the heat absorption of water vapor within the furnace; and third, increasing the proportion of lump ores being introduced into the furnace. With this in mind, the lump ore preheating treatment technology is introduced. By preheating the lumps at different temperatures, the influence of pretreatment on the reduction and soft melting of the lumps is studied. The results show that at different preheating temperatures, due to the transformation of FeOOH to Fe2O3, the natural goethite gradually changes from natural granular to spherical at higher preheating temperatures. When the preheating temperature is 400–700 °C, the coexisting phase of goethite and hematite in the pores changes obviously. The metallurgical properties of lump ore change dramatically. When the temperature is lower than 400 °C or higher than 700 °C, almost all goethite in lump ore is transformed into hematite, and the morphology does not change. [ABSTRACT FROM AUTHOR]

The corrosion behavior of Q345qNH steel and Q420qNH steel in simulated industrial atmospheric environment medium was studied by periodic immersion+infrared aging corrosion experiment. The results show that the corrosion type of both samples is uneven comprehensive corrosion, and the rust layer formed in the later stage of corrosion is relatively dense. But average corrosion rate of Q345qNH steel is always lower than that of Q420qNH steel, and the ratio of Iα‐FeOOH/Iγ‐FeOOH in rust layer is always higher. Compared with Q420qNH steel, Q345qNH steel has fewer surface pits but deeper local pits. The self‐corrosion potential of Q345qNH steel increases obviously, the resistance of the rust layer is larger, and protection to the matrix is stronger. This is because the formation of a large number of corrosion microcells induced by fine lamellar sorbite tissue that uneven distributed in Q420qNH steel, which increases the corrosion rate and makes corrosion uneven, while the larger pearlitic group in Q345qNH steel increases the local corrosion rate. However, the higher chromium/carbon ratio in Q345qNH steel promotes the conversion of lepidocrocite to goethite and inhibits the cathode reaction in the infrared drying stage, improving the density and stability of the rust layer. [ABSTRACT FROM AUTHOR]

The rise in demand for iron- and steel-based products globally has resulted in the depletion of high-grade iron ores, high energy consumption, and CO2 emissions. The world is rich in low-grade ores that have not been exploited, and this study aims to develop a feed for cast iron production, goethite ore–carbon composite pellets. A pelletizing disc was used to make the pellets followed by induration in a muffle furnace at 1373 K for 25 min, and the results showed that goethite–carbon composite pellets with the desired physical properties of a drop index greater than 4, dry compression strength greater than 2.2 kg/pellet, and an indurated compression strength above 250 kg/pellet could be produced by controlling the coal, limestone, and ethyl hydroxyethyl cellulose, avoiding the addition of impurities from bentonite. About 0.4 wt.% ethyl hydroxyethyl cellulose could be added to achieve the optimum strength in the composite pellets with a binary basicity of 0.27 and coal addition of 2.5 wt.%. A total metal recovery of 48.46% was achieved from the preliminary smelting experiments on the furnace burden, with a binary basicity of 1.3 at 1673 K with 25 min holding time and a carbon-to-oxygen ratio (wt.%) of 1.4 using an induction furnace. These composite pellets can potentially be used as a raw material for cast iron production towards the decarbonization of the steel industry. [ABSTRACT FROM AUTHOR]

In the present study, based on continuous acid–base potentiometric titration experiments of argillaceous limestone-derived yellow soil obtained at different depths in Pingba, Guizhou, a 1-site/2-pKa generalized composite surface complexation model (SCM) was established to obtain relevant parameters and explore soil surface acid–base properties. The model was employed to simulate cadmium (Cd) adsorption behavior. Combining the physicochemical properties of yellow soil and acid–base titration curves, the SCM-derived concentrations (Hs) and densities (Ds) of the surface-active sites for three soil layers showed decreasing trends with an increase in depth, whereas the calculated soil charge zero point (pHpzc) values matched the experimental values, indicating the applicability of SCM in studying the surface acid–base properties of yellow soil. Furthermore, as the pH increased, Cd shifted gradually from the dissolved to the adsorbed state, achieving complete adsorption at a pH of ~ 7. The model-simulated Cd adsorption curve matched well with the experimental curve; the Cd adsorption behavior corresponded with the simulated distribution of surface sites at different pH levels, with ≡SOH2+ and ≡SO− being the main forms at pH < pHpzc and pH > pHpzc, respectively. Correlation analysis indicated that organic matter and goethite played a major role in Hs, whereas the charge zero points of soils at different depths were determined mainly by clay minerals, such as illite and iron-aluminum oxides. Our study established a scientific and reasonable relationship between the soil physicochemical properties and model parameters, providing a basis for preventing heavy metal pollution behavior via the effective application of model predictions. [ABSTRACT FROM AUTHOR]

Soil mineralogy and texture are directly related to soil carbon due to the physical properties of the clay surface. Traditional techniques for quantifying carbon in soil are time-consuming and expensive, making large-scale quantification for mapping unfeasible. The alternative is the use of soil sensors, such as diffuse reflectance spectroscopy (DRS), an economical, fast, and accurate technique for predicting carbon stocks. In this sense, this study aimed to (a) investigate the relationship of C with different soil mineralogical, chemical, and physical attributes for different geological and geomorphological compartments; (b) understand which spectral bands are most important for estimating C content; (c) estimate C content from diffuse reflectance spectroscopy using different mathematical techniques and indicate which one is the best for tropical soil conditions; and (d) map C contents in detail. The study area was the Western Plateau of São Paulo (WPSP), which covers approximately 13 million hectares (~ 48% of the State of São Paulo, Brazil). A total of 265 samples were collected in this area. The attributes clay, silt, sand, crystalline and non-crystalline iron, base saturation, soil density, total pore volume, total C, C stock, kaolinite/(kaolinite + gibbsite) and hematite/(hematite + goethite), hematite and goethite contents, and spectral curves were evaluated. The spectra were recorded at 0.5-nm intervals, with an integration time of 2.43 nm s−1 over the 350 to 2500-nm range (350–800 nm—visible—VIS and 801–2500 nm—near-infrared—NIR). The data were subjected to descriptive statistics, Spearman correlation, stepwise analysis, and cluster grouping for characterization purposes; partial least squares regression (PLSR) and random forest (RF) for estimation purposes; and geostatistics analysis for creation of spatial maps. Our results indicate that the highest C contents are associated with more clayey soils, oxidic mineralogy, higher total pore volume, and lower soil density in highly dissected basalt compartments. The random forest algorithm associated with the Vis–NIR spectral range is more efficient for estimating and mapping C contents. This suggests that integrating diffuse reflectance spectroscopy with machine learning techniques holds promise for shaping public policies related to land use, mitigating CO2 emissions, and facilitating the implementation of carbon credit policies in a rapid and economically efficient manner. [ABSTRACT FROM AUTHOR]

Iron is commonly present as an impurity or by-product in various smelting processes. In this study, the separation and purification of iron from a zinc wet smelting leaching solution were achieved using the goethite method, which involved controlling pH and adding crystal seeds. The separated iron was then utilized as the iron source for the preparation of LiFePO4/C (lithium iron phosphate) in the form of α-FeOOH. Subsequently, LiFePO4/C was synthesized through wet ball milling and carbon thermal reduction. The physicochemical and electrochemical properties of the material were characterized using several techniques, including inductively coupled plasma-optical emission spectrometry (ICP-AES), X-ray diffractometer (XRD), field emission scanning electron microscopy (SEM), transmission electron microscope (TEM), thermogravimetric differential thermal analyzer (TG/DTA), Fourier exchange infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and electrochemical techniques. The results indicate that the LiFePO4/C prepared using the goethite method exhibits excellent cycling properties and stability. The initial discharge capacities at various rates (0.1 C, 0.2 C, 0.5 C, 1 C, 2 C, and 5 C) were measured as 149.5, 142.6, 135.6, 131.7, 116.5, and 102.5 mAh g−1, respectively. Impressively, after 200 cycles at 1 C, the material retained 99.5% of its initial capacity. Furthermore, even after 1000 cycles at a current rate of 1 C, it still maintained 95.4% of its capacity. Therefore, this study presents a novel technical route for the recovery and recycling of iron ions, while also demonstrating the promising performance of LiFePO4/C. [ABSTRACT FROM AUTHOR]

Carbonate rocks, widely used for quantifying paleolatitude of the Gondwana‐derived terranes on the Tibetan Plateau and the geodynamic evolution of the Tethyan Oceans, are prone to remagnetization. However, diagnosing such secondary remanent magnetization is difficult and the mistakes have induced confusion in paleogeographic reconstructions. To evaluate if the Upper Triassic limestones of the Duoburi Formation from the Lhasa terrane carry a primary remanence, we report comprehensive rock magnetic, diffuse reflectance spectroscopic, and petrographic results of these rocks. We discover that magnetic carriers vary systematically from magnetite to magnetite plus minor hematite/goethite to hematite/goethite plus minor magnetite with change of rock color and demagnetization behavior of the specimens. Most magnetite and all hematite/goethite grains have clear authigenic origin and were possibly formed during oxidation of early diagenetic pyrite. Such a process was likely assisted by oxic fluid circulation as shown by omnipresent calcite veins within the rocks. These authigenic iron oxides have widely distributed grain sizes with most of them being superparamagnetic at room temperature. Detrital (titano)magnetite is also recognized in some specimens, but its concentration is much lower than that of the authigenic magnetic grains. Based on these results, we conclude that limestone from the Duoburi Formation was remagnetized due to fluid circulation during late diagenesis. We discuss criteria used for diagnosing remagnetization in carbonate rocks, and suggest that a robust evaluation of the remanence origin should integrate field tests, statistics of the remanence direction, rock magnetic properties, and petrographic observations with the limits of each criterion being carefully considered. Plain Language Summary: The Lhasa terrane from the central Tibetan Plateau was one of the continental blocks that rifted from the Gondwana supercontinent, drifted northward, and accreted to Eurasia in the Mesozoic. Paleolatitude determined by paleomagnetism can provide quantitative information which is critical to restore these geodynamic processes. However, paleomagnetic investigations on the ancient carbonate rocks on the Tibetan Plateau are often troubled by remagnetization, a process during which the primary remanent magnetization acquired during or soon after formation of the rocks was replaced by secondary remanent magnetization with an unknown younger age. In this study, we provide an example of Upper Triassic limestones from the Lhasa terrane. Within these rocks, detrital (titano)magnetite, which can carry a primary magnetic signal, was mostly altered, and nonmagnetic pyrite largely transformed to authigenic magnetite/hematite/goethite, which acquired remanent magnetization at an unknown later time. The magnetic record from these rocks thus cannot be used to determine the Late Triassic paleolatitude of the Lhasa terrane. Our analysis reveals the most common mechanisms of remagnetization in carbonate rocks. More importantly, we provide universal tools and criteria that can be used in future paleomagnetic studies of carbonate rocks to evaluate their remanence origin. Key Points: Magnetic carriers of the Duoburi Formation limestone are authigenic magnetite, hematite and goethite and little detrital titanomagnetiteLimestones of the Duoburi Formation were remagnetized due to circulation of oxic fluid through the rock at a late stageDiagnosis of remagnetization in carbonate rocks should integrate different criteria but consider the limits of each criterion carefully [ABSTRACT FROM AUTHOR]

The Wadi Ranga sulfidic jasperoids in the Southern Eastern Desert (SED) of Egypt are hosted within the Neoproterozoic Shadli metavolcanics as an important juvenile crustal section of the Arabian Nubian Shield (ANS). This study deals with remote sensing and geochemical data to understand the mechanism and source of pyritization, silicification, and hematization in the host metavolcanics and to shed light on the genesis of their jasperoids. The host rocks are mainly dacitic to rhyolitic metatuffs, which are proximal to volcanic vents. They show peraluminous calc-alkaline affinity. These felsic metatuffs also exhibit a nearly flat REE pattern with slight LREE enrichment (La/Yb = 1.19–1.25) that has a nearly negative Eu anomaly (Eu/Eu* = 0.708–0.776), while their spider patterns display enrichment in Ba, K, and Pb and depletion in Nb, Ta, P, and Ti, reflecting the role of slab-derived fluid metasomatism during their formation in the island arc setting. The ratios of La/Yb (1.19–1.25) and La/Gd (1.0–1.17) of the studied felsic metatuffs are similar to those of the primitive mantle, suggesting their generation from fractionated melts that were derived from a depleted mantle source. Their Nb and Ti negative anomalies, along with the positive anomalies at Pb, K, Rb, and Ba, are attributed to the influence of fluids/melt derived from the subducted slab. The Wadi Ranga jasperoids are mainly composed of SiO2 (89.73–90.35 wt.%) and show wide ranges of Fe2O3t (2.73–6.63 wt.%) attributed to the significant amount of pyrite (up to 10 vol.%), hematite, goethite, and magnetite. They are also rich in some base metals (Cu + Pb + Zn = 58.32–240.68 ppm), leading to sulfidic jasperoids. Pyrite crystals with a minor concentration of Ag (up to 0.32 wt.%) are partially to completely converted to secondary hematite and goethite, giving the red ochre and forming hematization. Euhedral cubic pyrite is of magmatic origin and was formed in the early stages and accumulated in jasperoid by epigenetic Si-rich magmatic-derived hydrothermal fluids; pyritization is considered a magmatic–hydrothermal stage, followed by silicification and then hematization as post-magmatic stages. The euhedral apatite crystals in jasperoid are used to estimate the saturation temperature of their crystallization from the melt at about 850 °C. The chondrite (C1)-normalized REE pattern of the jasperoids shows slightly U–shaped patterns with a slightly negative Eu anomaly (Eu/Eu* = 0.43–0.98) due to slab-derived fluid metasomatism during their origin; these jasperoids are also rich in LILEs (e.g., K, Pb, and Sr) and depleted in HFSEs (e.g., Nb and Ta), reflecting their hydrothermal origin in the island arc tectonic setting. The source of silica in the studied jasperoids is likely derived from the felsic dyke and a nearby volcanic vent, where the resultant Si-rich fluids may circulate along the NW–SE, NE–SW, and E–W major faults and shear zones in the surrounding metavolcanics to leach Fe, S, and Si to form hydrothermal jasperoid lenses and veins. [ABSTRACT FROM AUTHOR]

This study investigates the uncommon formation of laterite from garnet–sillimanite–gneiss (grt-sil-gn) in the Matale area, a hilly region of Sri Lanka. Geographically, laterites typically form in lowland wet zone of the country, but this research explores their genesis in a unique, less-studied hilly environment. Employing a comprehensive approach combining field observations, petrographic studies, and chemical mapping, we elucidate the contrasting mechanisms of lateritization on the dip slope and scarp slope of a cuesta landform. Our findings reveal a significant influence of weathering conditions and supergene processes on laterite formation. Dip slopes experience intense supergene activity due to deeper groundwater, promoting downward fluid flow and mineral dissolution. Conversely, scarp slopes exhibit isovolumetric leaching with reduced infiltration and enhanced fluid interaction, leading to lateritization along fractures in partially weathered grt-sil-gn. Intense supergene processes on the dip slopes involve downward fluid migration and mineral dissolution, aided by a deep groundwater table. In contrast, scarp slopes exhibit laterite formation through isovolumetric leaching in areas with reduced water infiltration and heightened fluid interaction. Evidence of lateritization includes the formation of gibbsite, hematite, or goethite, attributed to fluctuating oxic and anoxic conditions caused by fluid variations. Additionally, kaolinite patches emerged on the exterior of fully altered garnet, resulting from the weathering products and leachates of quartz, sillimanite, and feldspar. This research emphasizes the critical role of external factors, such as weathering and supergene processes, alongside parent rock composition, in influencing laterite formation. It significantly advances our understanding of lateritization in grt-sil-gn, particularly in hilly areas with lower rainfall compared to usual laterite formation zones. [ABSTRACT FROM AUTHOR]

Bioremediation has drawn widespread concern in passivating heavy metals, but the intense toxicity of heavy metals to biological cells limits the application of functional strains. Herein, goethite-modified biochar (GMB) was chosen as the carrier to immobilize phosphate-solubilizing bacteria (PSB) of strain L1 for lead and cadmium remediation. Batch experiments showed that the GMB-L1 possessed excellent adsorption performance with a maximum adsorption of 496.54 and 178.18 mg/g for Pb and Cd, respectively. Moreover, adding GMB-L1 in contaminated soil converted heavy metals (Pb and Cd) into more stable fractions and reduced TCLP-extracted heavy metal concentrations (73.24% of Pb and 57.25% of Cd). The GMB-L1 was proved to accomplish Pb and Cd remediation via the process of chemical precipitation, surface complexation, electrostatic attraction, and biomineralization, which was accompanied by the transformation of heavy metals into a more stable crystal structure, such as Pb5(PO4)3OH and Cd5(PO4)3OH. Therefore, the co-system of GMB and strain L1 could be regarded as a prospective option for efficiently remedying environmental heavy metal pollution. [ABSTRACT FROM AUTHOR]

In this paper, based on our previous expertise on ceramic artifacts, several archaeometric methods applied to some samples collected from the Dudești archaeological site (Oltenia region, Romania) are reported for the first time in the literature. The chemical composition, and microstructural and morphological characterization of these samples offer important conclusions about the processing conditions. Some specific techniques such as X-ray diffraction (XRD), wavelength-dispersive X-ray fluorescence (WDXRF), optical microscopy (OM), stereomicroscopy, environmental scanning electron microscopy (ESEM), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy provide compositional information about composition and the decay processes. Additionally, the Brunauer–Emmett–Teller (BET) method helps to estimate pore sizes and specific surface areas. A thermogravimetric analysis (TGA/TDG) was used to establish details regarding the production technology and also the raw materials source used to make the ceramics. The obtained results indicated that the ceramics are based on a paste of muscovite and feldspar, with high plasticity, together with quartz and hematite/goethite and calcite, the latter in very low concentrations. According to the obtained results, we could assume that clays from the investigated samples had a low concentration of calcium. Gypsum is present as paste in a very low concentration, identified by the presence of a sulphate group in WDXRF. In the same context, iron oxides have a significant impact on the firing atmosphere of iron-rich clay, resulting in blackening under reducing conditions and a reddish coloration under oxidative conditions. The use of hematite and gypsum as pigments further contributes to the color variations in the pottery. The consistent firing temperature range of 200–600 °C in Dudești pottery implies a standardized production process, the variation in color being dependent on the specific reducing/oxidative regime conditions (reducing atmosphere followed by rapid oxidation). This relationship between clay composition and local sources suggests a connection to Neolithic pottery production in the region and their color depending on the reducing/oxidative regime conditions. [ABSTRACT FROM AUTHOR]