Low Fe3 Research Articles

Phosphorus removal from steelmaking slag by selective leaching in the steel pickling waste liquor

Steelmaking slag and steel pickling waste liquor (SPWL) are two kinds of by-products in steel plants. The existence of phosphorus (P) in steelmaking slag is the main factor affecting its reuse within the steelmaking process. To remove P from steelmaking slag with a low-cost method, selective leaching was proposed by using SPWL as a leaching agent. SPWL generally contains a small amount of Fe3+ ions, and thus the effect of Fe3+ content in SPWL on the dissolution behavior (especially P element) of steelmaking slag was investigated, as well as the pH value and steelmaking slag type. The dissolution ratios of P from various slags in the SPWL containing 500 ppm Fe3+ exceeded 95 % at pH 1.5 while those of Fe, Mn, and Al were very low, exhibiting satisfied selective leaching of P. Increasing pH value and Fe3+ content (in SPWL) resulted in a decreasing P dissolution ratio while exerting an insignificant effect on the dissolution of other elements. The FeHPO4+ was predicted as the predominant species during leaching and the transformation of FeHPO4+ to FePO4 could be present. When the SPWL containing 800 ppm Fe3+ was used, FePO4 was observed in the residues after leaching at pH 2.0, resulting in a worse removal of P from slag. However, the residues including massive valuable components had an extremely low P content after leaching in the SPWL containing 500 ppm Fe3+ at pH 1.5, which can be used as a flux in the metallurgical process. To ensure a high P removal rate from steelmaking slag and to prevent FePO4 precipitation during leaching, a relatively low pH and Fe3+ content in the SPWL are necessary.

Origin and metamorphism of ophiolitic serpentinites from the Yuli belt, eastern Taiwan: new findings and tectonic implications

ABSTRACT Serpentinites associated with metamafic and metaplagiogranitic rocks occur sporadically within metasedimentary schists in the Yuli belt. Such metaigneous rocks are considered to represent ophiolitic protoliths and some contain high-pressure (HP) metamorphic minerals or assemblages. However, the origin and metamorphism of these serpentinites have long been a mystery. This study systematically investigates the four major serpentinite-bearing exposures at the Fengtien, Wanjung, Tsunkuanshan, and Chinshuichi. The results reveal that the serpentinites are of two different protoliths on the basis of relict chromian spinel composition. Cr-spinel compositions of the Fengtien and Tsunkuanshan samples are characterised by moderate Cr# [Cr/(Cr + Al)] (0.45–0.57), relatively high Mg# [Mg/(Mg+Fe2+)] (0.59–0.79), but low Fe3+# [Fe3+/(Fe3++Cr+Al)] (0.02–0.06), reflecting an abyssal peridotite type protolith. By contrast, Cr-spinel compositions of the Wanjung and Chinshuichi samples show high Cr# (up to 0.74) and Fe3+# (0.03–0.08), but low Mg# (<0.6), indicating a forearc mantle peridotite origin. Peak metamorphic conditions of the serpentinites are represented by the assemblage of antigorite + magnetite + chlorite + olivine + diopside, which is estimated as up to 550°C but the pressure cannot be constrained quantitatively. Based on field relations, it is inferred that the serpentinites, associated HP metaigneous rocks, and garnet-bearing metasedimentary schists were metamorphosed isofacially. Despite two origins, the peridotitic protoliths were all subjected to hydration and subduction processes. We suggest that precursors of the serpentinites, metaigneous rocks, and metasedimentary schists were juxtaposed and metamorphosed at intermediate to great depths (~35–55 km) of a subduction zone. Therefore, the Yuli belt serpentinites and associated rocks likely represent exhumed materials from a palaeo-subduction interface.

Enhanced removal of nanoplastics from freshwater using in-situ synthesized and anchored nano-Fe3O4 via two-step ferrous oxidation

Magnetic separation is a promising strategy for removing nanoplastics (NPs) from water; however, it often requires complex processeses, such as synthesizing nano-Fe3O4 magnets and attaching them to specific carriers. This study presents an innovative and efficient strategy to in-situ synthesize and anchor nano-Fe3O4 onto polystyrene (PS) NPs through a two-step oxidation of ferrous ions, which significantly enhances NPs removal via magnetic separation. The two-step process involves initial alkalization of a ferrous aqueous solution under anoxic conditions, followed by oxidation in air. In the presence of PS spheres, nano-Fe3O4 forms in-situ on the PS surfaces, promoting sedimentation under a magnetic field. Results demonstrate that two-step ferrous oxidation achieves superior removal rates, with 99.32 % for 500 nm PS spheres (PS-500) and 93.16 % for 100 nm PS spheres (PS-100) using a low Fe2+ dosage of 0.1 mM. In contrast, the conventional one-step method, which simultaneously alkalizes and oxidizes ferrous sulfate in aerobic conditions, fails to form nano-Fe3O4 and results in low removal rates of only 56.49 % for PS-500 and 8.89 % for PS-100, respectively. Furthermore, the turbidity and residual Fe can be reduced to below 1 NTU and 0.1 mg/L by using two-step process, respectively, meeting drinking water safety and hygiene standards. This approach not only simplifies the magnetic nanomaterial preparation process but also substantially improves the NP removal efficiency, offering a promising solution for enhanced water treatment technologies and safer drinking water.

Resistance of four mutant rice (Oryza sativa L.) Varieties to iron toxicity at Njala inland valley swamp ecology in southern Sierra Leone

Four lowland rice varieties were examined for tolerance to Fe toxicity using morphological traits. In 2021, at the Njala Agricultural Research Centre (NARC), we conducted a field trial at the Inland Valley Swamp (IVS) in Sierra Leone. The four rice varieties, Bina 8, 10, 17, and Early Mutant, were planted in a randomized complete block design with three replications. The variance analysis revealed significant differences in all four rice varieties' traits. Elemental analysis of plant stalk revealed that Early Mutants and Bina 17 had the lowest Fe2+ concentrations (0.4 mg/kg soil and 0.8 mg/kg soil, respectively). On the other hand, Bina 10 and Bina 8 had higher Fe2+ concentrations (3.5 mg/kg soil and 1.5 mg/kg soil, respectively). In contrast, Bina 8 and Bina 10 had higher Fe2+ concentration values in their roots and stalks, indicating a higher accumulation of Fe2+. Thus, these two varieties also had the highest yield, indicating they tolerate Fe toxicity. This finding implies that rice varieties' capacity to withstand Fe toxicity plays a crucial role in sustaining growth and yield in Fe-toxic environments. The study concludes that screening rice varieties for Fe toxicity tolerance is important, but further research is needed to understand the mechanisms underlying Fe toxicity tolerance in rice.

Reactions between ferric oxyhydroxide mineral coatings and a dimethoxyhydroquinone: A source of hydroxyl radicals

Quinones are organic molecules that facilitate electron-transfer reactions in terrestrial environments. The reduced forms, hydroquinones, are powerful reductants that can trigger non-enzymatic radical-based decomposition of organic matter and contaminants by simultaneous reduction of iron and oxygen. Iron oxides often occur as coatings on other minerals, thus our study investigated the reactions between the ferric oxyhydroxide (FeO(OH)) surface coatings on gibbsite (Al(OH)3) and 2,6-dimethoxy-1,4-hydroquinone (2,6-DMHQ). The main aim was to investigate the oxidation of 2,6-DMHQ and the generation ∙OH in the presence of O2 at low Fe concentrations in a novel setup that allows local structural characterization. The heterogeneous redox reactions between 2,6-DMHQ and the FeO(OH) coatings were studied at pH 5.0 as a function of the amount of Fe present on the gibbsite surfaces, including the effect of aging of the FeO(OH) coatings. The results showed that reactions between 2,6-DMHQ and FeO(OH) coated gibbsite under ambient conditions can generate substantial amounts of ·OH, comparable with amounts generated on pure ferrihydrite surfaces. The ·OH is the product of two sequential reactions: hydroquinone oxidation by O2 and degradation of the formed H2O2. The calculated rate constant of the former reaction is the same regardless of amount of FeO(OH) coating suggesting a surface catalytic process where 2,6-DMHQ is oxidized by O2 resulting in formation of H2O2. Subsequently, the observed induction period, the low Fe2+ (aq) concentrations in solution and the dependency of FeO(OH) coating amount influencing ·OH formation suggest that the pathway for ∙OH is through H2O2 decomposition by the surface sites on the FeO(OH) coating. Overall, this study shows that co-existence of oxygen, FeO(OH) and organic reductants, possibly secreted by soil microorganisms, creates favorable conditions for generation of ·OH contributing to decomposition of organic matter and organic pollutants in soil environments.

Electrical and structural properties of BiFeO3 thin films with four distinct buffer layers: La2O3, Pr2O3, Sm2O3, and Tm2O3

In this study, BiFeO3 thin films were fabricated using a spin-coating technique on SrRuO3/n+-Si substrates, employing four different RE2O3 (La2O3, Pr2O3, Sm2O3, and Tm2O3) buffer layers. The investigation focused on assessing the structural and ferroelectric characteristics of these films. X-ray diffraction analysis revealed a (110) preferred orientation with a perovskite-rhombohedral structure in films with RE2O3 buffer layers. Atomic force microscopy analysis indicated smooth surfaces for these layers. Secondary ion mass spectrometry demonstrated high levels of Bi ions in films with RE2O3 buffer layers, while X-ray photoelectron spectroscopy revealed a low Fe2+/Fe3+ ratio in these layers. Notably, the film with a Sm2O3 buffer layer showed a lower leakage current (2.05 × 10−6 A/cm2) and a higher remnant polarization (43.65 μC/cm2). This improvement is attributed to Sm3+ ions fostering (110) orientation, reducing surface roughness, increasing Fe3+ content, thereby minimizing oxygen vacancies, and suppressing Fe3+ to Fe2+ valence fluctuation.

Optimizing bimetallic-insect exuviate melanin composite cathodes using response surface methodology to enhance the H2O2 yield and selectivity of the electro-Fenton process

Electro-Fenton is a fast and efficient oxidative degradation technology for treating many refractory organic substances. However, the poor electrochemical performance and power generation capacity of the cathode during electro-Fenton treatment limit H2O2 generation and pollutant removal. A FeCu bimetal–melanin cathode catalyst with high H2O2 production, low Fe3+ formation, and low resistance was optimized using response surface methodology. The composite desirability coefficient was as high as 0.9281, indicating that the two-factor setting conditions yielded the optimal response results. The synergistic effect between Fe and Cu and the ionic conductivity of melanin promote the conversion between Fe2+ and Fe3+ and improve the charge transfer ability of the cathode. The optimized Fe–Cu–Me cathodic catalyst had the highest H2O2 generation (217.91 ± 4.65 mg/L) and the lowest resistance value (190.33 Ω), 4.88 times and 5.05 % that of the unmodified cathode, respectively; also the lowest Fe3+ generation was 32 % and 73 % that of the Fe and FeCu cathodic catalysts, respectively. Moreover, the optimized Fe–Cu–Me cathode catalyst exhibited up to 80 % selectivity for 2-electron oxygen reduction reaction-catalyzed H2O2 generation based and excellent O2 and H2O2 adsorption performance on ring disk electrode analysis and density function theory calculation. This study is the first to use FeCu bimetals combined with insect exuviate melanin as a cathode catalyst for the in situ generation of cathodic H2O2. The high performance and stability of the fabricated electrocatalyst can be used in the subsequent treatment of wastewater through the electro-Fenton process, providing an innovative approach to improve the performance of the cathode.

Green degradation of ofloxacin in electric Fenton based on Fe3+/Fe2+ internal cycling within Fe3O4 under neutral condition

To break the drawbacks of the traditional electro-Fenton (EF) such as narrow pH, low utilization of ·OH, Fe2+ loss, and low Fe3+ reduction rate, a new strategy that the ·OH generation in EF is based on the internal cycling of Fe2+/Fe3+ within Fe3O4 is proposed. A new-type homogeneous EF system (EF-Fe3O4@CF) where the Fe3O4-modified carbon felt box with clinoptilolite addition was used as the cathode, was established. The experimental results indicate that the system has 100 % removal efficiency for ofloxacin (OFL) and 86.4 ± 2.4 % removal efficiency for TOC at 120 min at pH = 7, and in multi-cycle operation the efficiency of OFL and TOC degradation did not decrease. Fe2+ (within Fe3O4) can activate H2O2 to generate ·OH and Fe3+ (within Fe3O4) is simultaneously reduced to Fe2+ on the cathode, so the internal cycling of Fe3+/Fe2+ within Fe3O4 achieve the green regeneration of ·OH. The conversion range of Fe3+/Fe2+ within Fe3O4 crystal is 4.43:1–1.46:1. The EF-Fe3O4@CF with multi-functions of adsorption, catalysis, and green degradation showed good stability and reusability. Our work provides fundamental research for Fe3O4 as a promising heterogeneous EF catalyst in advanced wastewater treatment.

Ferric Iron in Eclogitic Garnet and Clinopyroxene from the V. Grib Kimberlite Pipe (NW Russia): Evidence of a Highly Oxidized Subducted Slab

Abstract Estimates of oxygen fugacity of eclogitic rocks are linked to the redox evolution of the oceanic protolith during subduction and its residence in the lithospheric mantle, and, based on knowledge of pressures and temperatures, allow modelling of the speciation of volatile elements and diamond (or graphite) versus carbonate stability. To date, the oxygen fugacity of mantle eclogites has been shown to vary between −6 (Kasai, Congo and Udachnaya, Siberia) and −0.1 (Udachnaya, Siberia) log units (relative to the fayalite–magnetite–quartz buffer, FMQ), linked to the low Fe3+ contents of garnets. In this study, we investigated the Fe oxidation state of coexisting garnet and clinopyroxene hand-picked out of 17 diamond-free high-MgO and low-MgO mantle eclogites (dated at 2.84 Ga) from the Grib kimberlite pipe (East-European platform). Measured Fe3+/∑Fe values range between 0.03 and 0.19 for garnet and 0.18–0.38 for clinopyroxene, the former being higher than what was measured previously in garnets equilibrated at mantle conditions. The Fe3+/∑Fe of the reconstructed bulk rock ranges between 0.10 and 0.15 for high-MgO eclogites and 0.10 and 0.24 for low-MgO eclogites (with uncertainties of ± 0.02 and ± 0.03 in both cases). Thermobarometric calculations result in equilibration pressures and temperatures of 3.0–5.2 (± 0.4) GPa and 720–1050 (± 60) °C for both high-MgO and low-MgO eclogites, slightly lower than previous P–T estimates of mantle eclogites from the Udachnaya kimberlite pipe (Siberian craton). At these conditions, ∆logfo2 (FMQ) calculated using the available oxythermobarometric model varies from −1.7 to −0.6 log units for high-MgO eclogites and from −2.9 to 0.9 log units for low-MgO eclogites. Samples recording ∆logfo2 (FMQ) ≤ −1 log units overlap with North Slave, West Africa and Udachnaya eclogites, with no difference among eclogite types. The average values of −1.2 (± 0.4) log units for high-MgO and −0.6 (± 1.1) log units for low-MgO eclogites suggest different redox conditions of basaltic protoliths during subduction worldwide. Previous geochemical studies on the same rock samples reported evidence of cryptic metasomatism in both garnet and clinopyroxene that we demonstrate being not recorded by their major elements, while modal metasomatism evidenced by the presence of phlogopite as a product of interaction with a kimberlitic melt only affects the MgO of the bulk rock. Therefore, we suggest that high Fe3+/∑Fe ratios for garnet (&amp;gt; 0.10) and for reconstructed bulk rocks in the case of both low-MgO and high-MgO samples cannot be due to metasomatic interaction with an oxidized fluid, but rather are the consequence of Fe3+ redistribution in an unusually oxidized mafic protolith upon metamorphism. Our results highlight the redox variability of eclogites of Archaean age at conditions more oxidized than present-day mid-ocean ridge basalts (MORBs) and imply an oxidizing nature of the convective mantle source where magma was formed with consequent speciation of C in the form of carbonate fluid explaining, therefore, the lack of eclogitic diamonds in V. Grib kimberlite pipe.

Oxoborates of the ludwigite group: Natural and mineral-like compounds as prospective materials

Research subject. Natural oxoborates of the ludwigite group, including azoproite, ludwigite, and vonsenite. Their empirical formulas based on five oxygen atoms have the following form: azoproite (Mg1.81Fe2+0.19)∑2.00(Fe3+0.36Ti0.26Mg0.26Al0.12)∑1.00 O2(BO3), ludwigite (Mg1.69Fe2+0.30Mn2+0.01)Σ2.00(Fe3+0.90Al0.07Mg0.02Sn0.01)Σ1.00O2(BO3) and vonsenite (Fe2+1.86Mg0.13)∑1.99 (Fe3+0.92Mn2+0.05Sn4+0.02Al0.02)∑1.01O2(BO3). Aim. To establish the relationship between the composition, crystal structure, and thermal behavior (293–1373 K) of the minerals. Materials and methods. Ludwigite was collected at the Iten’yurginskoe tin skarn deposit; vonsenite was collected at the Titovskoe magnesium-skarn boron deposit; azoproite was collected at magnesian skarns of the Tazheran alkaline massif. The methods of single crystal X-ray diffraction, energy dispersive X-ray spectroscopy, high-temperature X-ray diffraction, Mössbauer spectroscopy, and thermal analysis were used. Results. Low-charge cations (Fe2+, Fe2.5+, Mg2+) tend to occupy the M(1)–M(3) sites, and high-charge cations (Fe3+, Al3+, Ti4+, Sn4+) generally occupy the M(4) site. Azoproite is characterized by the highest melting temperature Tm &gt; 1650 K. Due to the low Fe2+ content, azoproite does not undergo solid-phase decomposition across the investigated temperature range. The melting point of ludwigite exceeds 1582 K, which is due to the high Mg content; as a result of the Fe2+ → Fe3+ oxidation, it gradually decomposes with the formation of hematite, warwickite, and magnetite. The temperatures of oxidation and solid-phase decomposition in the Fe2+-rich vonsenite are approximately 100 K lower than those in ludwigite. The melting point of vonsenite is 1571 K. All the minerals are characterized by a weak degree of thermal expansion anisotropy. The main contribution to the thermal expansion anisotropy is due to the preferred orientation of the [BO3]3– triangles. Conclusions. The thermal properties of the oxoborates depend on their chemical composition. It was established that Tm increases with an increase in the Mg and Ti4+ content, and decreases with an increase in the Fe2+ content. The Fe2+ → Fe3+ oxidation is observed when the FeO component in the minerals exceeds 10 wt %, which leads to the solid-phase decomposition starting at temperatures of about 500–600 K. The values of the 293KαV volume thermal expansion of ludwigite and azoproite are comparable, while the largest values were observed for vonsenite. This is associated with the largest average bond lengths, primarily those of &lt;Fe2+–O&gt;6.

Genesis of gray sandstone within the red beds in HLJ-DL uranium deposit, southwest Songliao Basin and its relationship with uranium mineralization

The search for uranium deposits in the red beds is currently a hotspot in China's sandstone-type uranium exploration efforts. The typical occurrence of uranium deposits is within gray sandstone layers amidst the red beds, where the distribution of these gray sand bodies dictates the presence of uranium deposits. Hence, delving into the genesis of gray sandstone within the red beds proves beneficial for both uranium exploration and unraveling the ore-forming mechanisms. However, there is currently significant controversy surrounding the genesis of gray sandstone in the red beds. This paper focuses on the typical uranium deposit in the red beds—the HLJ-DL uranium deposit in the southwestern part of the Songliao Basin. It investigates the genesis of gray sandstone within uranium-bearing rock series and its relationship with uranium mineralization. The lithology of representative drill cores, including the red sandstone for comparative study, is methodically examined, along with their elemental geochemistry as well as carbon and oxygen isotope characteristics. The petrological characteristics suggest that both the gray and red sandstone share similar compositions of clastic particles, indicating minimal influence of the source rock on the sandstone color. The gray sandstone displays comparable TOC content (averaging around 0.05 %) and δ18OPDB values (averaging around −16 ‰) to the red sandstone. However, it exhibits relatively higher δ13CPDB values (averaging −0.26 ‰), whereas the average δ13CPDB value for the red beds is −1.61 ‰. The data indicate that the gray sandstone is less affected by hydrothermal or hydrocarbon fluids. Compared to the red sandstone, which has relatively higher Cu/Al values (averaging 1.09) and Fe3+/Fe2+ ratios (averaging 3.37), the gray sandstone exhibits low Cu/Al values (averaging 0.44) and a low Fe3+/Fe2+ ratio (averaging 0.36), suggesting its formation in a relatively reducing environment. The reducing conditions necessary for the formation of gray sandstone may stem from the climate becoming relatively warm and humid, irrespective of whether it originates from the original sedimentary environment or is induced by the reducing pore water discharged from dark mudstones. The chemical weathering index of fine-grained sediments indicates that, the gray sandstones were commonly configured in relatively humid-warm climate with fairly low dissolved oxygen content in the bottom water. Additionally, the deposition of the uranium-bearing rock series experienced alternating climatic changes, rather than consistently being in a humid-warm climate. This resulted in the sand bodies with low TOC content, insufficient reducing potential, and uranium mineralization primarily occurring in the interior of the basin. Organic matter has a relatively weak control over uranium mineralization, whereas uranium mineralization shows a certain correlation with iron reduction. The ore-forming fluid was uranium-rich oxygenated atmospheric water. Dark-colored mudstones, formed under humid-warm climatic condition, contain relatively high TOC contents (avg. 0.43 %) and exhibit a strong reducing capacity. The reducing pore water in dark-colored mudstones excreted into the adjacent sandstones under compaction during the early diagenesis, is able to serve as a vital reducing agent in later-stage uranium mineralization. Additionally, certain dark-colored mudstones with high uranium content (up to 944 ppm) undergo significant uranium pre-enrichment, providing a partial uranium source for uranium mineralization.

The relationship between iron redox states and H2O contents in back-arc basin basaltic glasses from the North Fiji Basin

Island-arc basalts (IAB) from convergent plate margins tend to have both higher iron oxidation states (higher Fe3+/Fe2+) and higher H2O contents than the mid-ocean ridge basalts (MORB) produced by seafloor spreading, which raises the question of whether these two characteristics are causally related. Back-arc basin basalts (BABB) may help with this question, in that they are products of seafloor spreading, like MORB, but sourced from supra-subduction mantle, like IAB. Here we examine the relationship between Fe3+/Fe2+ (determined by XANES spectroscopy) and H2O contents in BABB glasses from the North Fiji Basin (NFB). The glasses cover a range of compositions from 6.1 to 8.5 wt% MgO, and from 0.16 to 1.6 wt% H2O, and have also been analysed for trace elements and Sr-Nd-Pb-isotopes. Measured Fe3+/Fe2+ range from MORB-like to slightly higher values and are positively correlated with H2O and heavy-halogen contents (Cl, Br and I). The correlation is due to lower Fe2+ rather than higher Fe3+ compared to the MORB array. This suite of BABBs is not significantly enriched in trace elements other than H2O and the heavy halogens, with MORB-like Ba/Th and other incompatible-element ratios, suggesting that the H2O and halogens may have come from dehydration of subducted lithospheric serpentinites under subsolidus conditions. Na2O is unusually variable for a suite of samples from such a limited area, and is not correlated with H2O, precluding a relationship between H2O and degree of melting. The link between H2O and low Fe2+ may be explained by H2O-rich fluids entering the transcrustal magma plumbing system, where they increase the proportion of olivine and augite to plagioclase crystallizing during the crustal evolution of the magmas. In this situation, relatively small additions of H2O can have an enhanced effect on major-element chemistry if the crustal evolution proceeds by cycles of replenish-mix-tap-crystallize (RMTX) rather than by simple fractional crystallization without repeated replenishment and tapping. The absence of any increase in Fe3+ with H2O, together with the lack of any correlation between H2O and Fe3+/Fe2+ in MORB glasses generally, suggest that various mechanisms, including more extensive olivine fractionation, were responsible for elevating Fe3+/Fe2+ in H2O-rich basalts from convergent margin settings. Proxy methods based on concentrations of elements with redox-variable partition coefficients (V, Eu) are not sensitive enough to record the subtle variations in Fe3+/Fe2+ observable by XANES spectroscopy.

Ferroptosis as a Potential Therapeutic Target for Reducing Inflammation and Corneal Scarring in Bacterial Keratitis.

Bacterial keratitis (BK) is a serious ocular infection that can cause severe inflammation and corneal scarring, leading to vision loss. In this study, we aimed to investigate the involvement of ferroptosis in the pathogenesis of BK. Transcriptome analysis was performed to evaluate ferroptosis-related gene expression in human BK corneas. Subsequently, the ferroptosis in mouse models of Pseudomonas aeruginosa keratitis and corneal stromal stem cells (CSSCs) were validated. The mice were treated with levofloxacin (LEV) or levofloxacin combined with ferrostatin-1 (LEV+Fer-1). CSSCs were treated with lipopolysaccharide (LPS) or LPS combined Fer-1. Inflammatory cytokines, α-SMA, and ferroptosis-related regulators were evaluated by RT-qPCR, immunostaining, and Western blot. Iron and reactive oxygen species (ROS) were measured. Transcriptome analysis revealed significant alterations in ferroptosis-related genes in human BK corneas. In the BK mouse models, the group treated with LEV+Fer-1 exhibited reduced inflammatory cytokines (MPO, TNF-α, and IFN-γ), decreased corneal scarring and α-SMA expression, and lower Fe3+ compared to the BK and LEV groups. Notably, the LEV+Fer-1 group showed elevated GPX4 and SLC7A11 in contrast to the BK and LEV group. In vitro, Fer-1 treatment effectively restored the alterations of ROS, Fe2+, GPX4, and SLC7A11 induced by LPS in CSSCs. Ferroptosis plays a crucial role in the pathogenesis of BK. The inhibition of ferroptosis holds promise for mitigating inflammation, reducing corneal scarring, and ultimately enhancing the prognosis of BK. Consequently, this study provides a potential target for innovative therapeutic strategies for BK, which holds immense potential to transform the treatment of BK.

Advanced oxidation treatment of aqueous atrazine by fixed-bed reactor packed with carbon-supported molybdenum disulfide

MoS2/carbon composites were prepared by affixing MoS2 onto carbon particulates and used as packing materials to establish persulfate advanced oxidation fixed-bed reactors (PS-FBR) for effective continuous-flow degradation of organic pollutants. Since MoS2 was a co-catalyst in accelerating the conversion of Fe3+ to Fe2+, an improved degradation performance against organic pollutants such as atrazine (ATZ) was achieved in this PS/Fe2+/MoS2-FBR. Cost-effective materials of granular carbon, needle carbon, quartz particles, and MoS2 with different morphologies were compared during the preparation of MoS2/carrier composites. The results indicated that a higher adsorption capacity of both carriers and MoS2 was more plausible for ATZ degradation in FBR. After the systematic investigation of reaction conditions, a removal efficiency of 99 % for ATZ was achieved at pH 3–7, 2 mg/L Fe2, 2 mM PS, flow rate of 2 mL/min (cross-sectional area of 1.33 cm2). Meanwhile, this PS/Fe2+/MoS2-FBR could be continuously operated for over 5 days with removal efficiency above 90 %. Importantly, a low Fe2+ concentration of 2 mg/L was sufficient in this system, which could limit the formation of iron sludge and ensure long-term operation.

Fe Kα XANES, Fe Kβ HERFD XANES and EPMA flank method determinations of the oxidation state of Fe in garnet

The ferric to total iron ratios (Fe3+/∑Fe) of garnets can be paired with thermodynamic mineral activity models to quantify the oxygen fugacity of garnet-bearing rocks. However, techniques with a high analytical and spatial resolution are necessary to distinguish differences in garnet Fe3+/∑Fe ratios at the percent level and to accurately measure garnets that are zoned or contain inclusions. We acquired conventional Fe Kα and high-resolution energy fluorescence detection (HERFD) Fe Kβ X-ray absorption near edge structure (XANES) spectra and electron microprobe flank method analyses on a suite of 27 peridotitic and eclogitic garnets with Fe3+/∑Fe ratios previously determined by Mössbauer spectroscopy to evaluate the precision of each technique. We examined variations in the energy and intensity of three XANES spectral features as a function of Fe3+/∑Fe ratios: 1) the intensity ratio of two-post edge features (I-ratio; Fe Kα only); 2) the energy of the Fe edge at 90% normalized intensity (E0.9; Fe Kα only) and 3) the pre-edge centroid energy (Fe Kα and HERFD Fe Kβ). In accordance with previous work, we find the energies of garnet pre-edge centroids are relatively insensitive to Fe3+/∑Fe ratios. The I-ratios of peridotitic and eclogitic garnets are offset from each other at low Fe3+/∑Fe ratios (≤0.13); I-ratio garnet XANES calibrations are composition-specific. The E0.9 feature is independent of garnet major element composition in spectra that have been corrected for the effects of self-absorption. We produce two Fe Kα garnet XANES calibrations based on variations in the E0.9 feature; one calibration with all garnet reference materials included (Fe3+/∑Fe up to 1.0; “all garnet calibration”) and another calibration specific to garnets with low Fe3+/∑Fe ratios (“low ferric calibration”). Fe3+/∑Fe ratios calculated from the mean of up to 25 flank method measurements on eight garnet reference materials fall within 4% absolute of a one-to-one correlation with Fe3+/∑Fe ratios measured by Mössbauer. The standard error of the mean Fe3+/∑Fe ratio calculated from flank method approaches the Mössbauer-determined Fe3+/∑Fe ratio within estimated error (3%) after three analyses. Flank method precision is enhanced at higher beam current; however, the precision of the flank method does not approach the precision of XANES under any microprobe analytical condition tested here. Garnet reference materials detailed here are available by request to the Smithsonian Institution.

Coupling homogeneous and heterogeneous catalysis for the efficient and selective activation of H2O2

This work reveals the synergy between homogeneous and heterogeneous catalysis for the efficient and selective H2O2 activation, realizing excellent AOPs with very low Fe2+ input, enhanced selectivity, and potential large-scale applications.

Agri-waste derived electroactive carbon-iron oxide nanocomposite for oxygen reduction reaction: an experimental and theoretical study.

Herein, we have utilized agri-waste and amalgamating low Fe3+, to develop an economic iron oxide-carbon hybrid-based electrocatalyst for oxygen reduction reaction (ORR) with water as a main product following close to 4e- transfer process. The electrocatalytic activity is justified by electrochemical active surface area, synergetic effect, and density functional theory calculations.

Main minerals of the Araxá alkali-carbonatite complex, Minas Gerais State, Brazil

The Araxá alkali-carbonatitic complex is a significant source of niobium and phosphate and accounts for approximately 75% of global niobium production. The complex contains magmatic niobium ore minerals, such as natrium-pyrochlore and calcium-pyrochlore, and hydrothermal niobium ore minerals in the form of kenopyrochlore and natrium-pyrochlore. The magmatic micas in the complex are tetraferriphlogopites that exhibit Mg-rich cores surrounded by one or two rims of tetraferriphlogopites formed by hydrothermal alteration. These rims have lower IVAl and Mg apfu (atom per formula unit) values but higher IVFe3+ and Fe2+ contents than the original phlogopite. Microphlogopitite dikes that formed during several episodes of magmatism between 83.48 and 77.4 Ma contain tetraferriphlogopites, phlogopite, eastonite, biotite, and annite-siderophyllite. These micas exhibit variations in Mg2+ and Fe2+ concentrations owing to the magmatic differentiation and subsequent hydrothermal alteration, resulting in rims with higher Mg and lower Fe2+ concentrations than the mica core. The Araxá complex also contains magmatic magnetite that has been further altered by hydrothermal processes, resulting in the formation of ilmenite and the oxidation and crystallization of titaniferous hematite. Magnetite within the microphlogopitites displays variations in the concentrations of Fe3+ and Ti, likely owing to the timing of the intrusion of the microphlogopitites into the Araxá complex. The degree of oxidation of the oxidized ilmenite of the Araxá complex varies based on the intrusions, which occurred before or during hydrothermal activity. Apatite is concentrated in carbonatites, which form a ring around the core of the complex, and disseminated in phlogopite-rich rocks hosting norsethite carbonatite veins in the center of the complex. The apatite in the core rocks exhibits complex zonation with unexpected changes in Ca, P, and Sr concentrations. Apatite in the carbonatite ring was generated during the differentiation of the carbonatite magma, whereas that in the core rocks exsolved from the phosphorus-saturated carbonatite magma (in press). The carbonate minerals dolomite, norsethite, and calcite exhibit compositions grouped around their end-members, suggesting that they formed during different stages of magmatic source differentiation. Strontium differentiation occurs in the magmas corresponding to each endmember, and carbocernaite is exsolved from the Sr-saturated crystals, thus forming micro-inclusions in some carbonate crystals that have been displaced by late-magmatic hydrothermal fluids.

Tracing tungsten-tin mineralization processes with tourmaline geochemistry in the Wangxianling-Hehuaping district, Nanling Range (South China)

The mechanisms controlling the enrichment and separate precipitation of tungsten and tin ores are obscure. To unravel the physicochemical changes in the mineralization system during the magmatic-hydrothermal transition, we investigate the petrography, geochemistry, and boron isotopes of tourmaline in the Wangxianling-Hehuaping district (Nanling Range, South China). Four types of tourmalines were identified: Magmatic (Tur-WG) and hydrothermal (Tur-WV) tourmaline in the Triassic W-mineralized tourmaline-two-mica granite (ca. 220 Ma); Magmatic (Tur-SnG) and hydrothermal (Tur-SnV) tourmaline in the Jurassic Sn-mineralized biotite granite (ca. 155 Ma). Tur-WV and Tur-SnV have lower Fe3+/(Fe2+ + Fe3+) ratios than those of Tur-WG and Tur-SnG, suggesting that W-Sn mineralization occurred in a relatively reducing environment. In addition, the δ11B values of all four types of tourmalines are similar, suggesting that the ore-forming fluids were primarily exsolved from the granitic magma. Significant chemical variations (e.g., Mg, Fe, Sc, V, Ni, and REEs) between Tur-SnG and Tur-SnV may have been resulted from fractionation and intense ore fluid-wall rock reactions. In contrast, Tur-WG has similar chemical compositions to Tur-WV, suggesting that the Triassic W mineralization may have undergone a magmatic-hydrothermal process with little ore fluid-wall reaction. Tur-SnV has exceptionally high F content, which could enhance the Sn solubility and enrichment. This explains the low Sn content of granitic magmas with large-scale Jurassic tin mineralization. Considering that W has a large melt-fluid partition coefficient, we conclude that in the Triassic, W is enriched in the exsolved fluid from the granitic magma and precipitated with temperature drop. This may have caused the decrease in W content in the protolith and limited the Jurassic W mineralization. Subsequently, the mantle-derived F addition along the Chenzhou-Linwu fault in the Jurassic had led to Sn enrichment in the fluids, and mineralization is triggered by temperature drop and fluid-rock reactions. Eventually, the extensive Triassic W mineralization and Jurassic Sn mineralization exhibit the separation of tungsten-tin mineralization. The separated tungsten-tin mineralization model based on different volatile components could also be applicable to other tungsten-tin metallogenic belts.

Copper recovery from low-grade copper sulfides using bioleaching and its community structure succession in the presence of Sargassum

Bioleaching characteristics and bacterial community structure were studied during low-grade copper sulfide ores bioleaching in the presence of pretreated Sargassum (PSM). Results indicated that proportion of attached bacteria and copper recovery were improved by using appropriate-dosage PSM. High copper recovery (82.99%) and low Fe3+ concentration were obtained when 150 mg L−1 PSM was used. Precipitation, such as KFe3(SO4)2(OH)6 and (H3O)Fe3(SO4)2(OH)6, was not found in samples used PSM according to XRD, FTIR and TG analyses, which may result from less passivation layer formed by Fe3+ hydrolysis. I− contained in PSM can act as the reductant to convert Fe3+ into Fe2+, which can reduce Fe3+ hydrolysis and adjust Eh value. Bacterial community structure was influenced significantly by PSM according to the 16 S rDNA analysis. Acidithiobacillus ferrooxidans dominated proportion of bacterial community throughout bioleaching process, whose proportion reached 89.1091% after 14 days in sample added 150 mg L−1 PSM.