Formation Of Hematite Research Articles

Bio-Preparation of Iron Nano Fertilizers from Lemon Fruit Affected some of the Characters of Carrot plants (Daucus carota L.)

To study the biological preparation of iron nano fertilizers from lemon fruit extract and their effect on some quantitative traits of carrot (Daucus carota L.) plant. Experiments were conducted, a laboratory part and a field part, with two addition factors, foliar fertilization and soil fertilization, using two sources of iron. The first source was nano-iron at a concentration of 0.5, 1, 1.5, and 2 mg L-1, and the second source was chelated iron at a concentration of 1.5 g L-1 and control treatment. The results showed the superiority of foliar fertilization in most of the studied traits such as iron concentration, root length, root diameter, fresh weight, dry weight, carotene and total dissolved solids (144.30 ppm, 17.10 cm, 2.1 cm, 137.98 g, 16.03 g, 1.62 mg g fresh weight-1 and 8.79 %, respectively). Nano-iron spraying was superior than to chelated iron in the concentration of iron (Fe), root length, root diameter, fresh weight, dry weight, and total dissolved solids (1059.22 ppm, 20.82 cm, 2.29 cm, 168.97 g, 18.37 g, and 9.91 %, respectively). X-ray diffraction (XRD) was used to determine the size and purity of the nanoparticles, and scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to verify the composition. Iron oxide (Fe2O3) was in the form of α-Fe2O3 hematite with a size of 32.8 nm and Ỵ-Fe2O3 maghematite with a size of 44.6 nm. We conclude that the use of green synthesis method for nano-fertilizers has proven effective and efficient from an economic and environmental point of view.

Exploring Microwave Roasting Characteristics of Magnetite Pellets: A Focus on Hematite Formation and Elemental Migration

Exploring Microwave Roasting Characteristics of Magnetite Pellets: A Focus on Hematite Formation and Elemental Migration

Atmospheric corrosion of carbon and galvanized steel under high rainfall conditions.

The corrosion rates of carbon steel and galvanized steel according to the ISO 9223 standard, the effect of pollutant contamination and atmospheric aggressiveness under high rainfall conditions in the Chocó department were studied. Carbon and galvanized steel samples, chloride, and sulfur collectors were exposed in three atmospheric stations in three strategic positions covering the Colombian Pacific: Quibdó, Andagoya and Bahía Solano, for different exposure periods (up to 18 months). The structural-micro characterization of corrosion products was evaluated via X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy SEM-EDS. The results indicate that all study regions obtained the highest time of wetness category (τ 5). The sulfur-containing pollution (SO2) was categorized as P 0 (rural atmosphere) with average values of P d≤4mg/m2 - day. Bahia Solano station showed the highest chloride deposition rate, reporting an average of 8.3mg/m2-day (categorized as δ1), according to ISO 9223. Due to the extremely high rainfall in the department of Chocó, the results initially suggested hematite formation on carbon steel. After several months, there was a phase transition to lepidocrocite (γ-FeOOH). The formation of γ-FeOOH induces active corrosion on the iron substrate. The zincite phase (ZnO) was observed in the galvanized steel corrosion products. The corrosion rates of carbon and galvanized steel in the location of Quibdó-Colombia were higher than in previous reports. Data analysis reveals that the precipitation variable, which governs the TOW and pollution contaminants, significantly influences the corrosion of these exposed metals.

Green Synthesis of Iron Oxide from Lathe Waste Using Green Tea Leaves (<i>C</i><i>amellia</i><i> s</i><i>inensis</i>) Extract by Temperature Variations of Synthesis

Iron oxide was produced from lathe waste using green tea leaf extracts. Green tea leaves contain catechins, has been produced as a possible reducing, precipitating, stabilizing, and capping agent. Another advantage of applying green tea leaves to synthesize iron oxide is reducing toxicity. Various temperatures of synthesis utilizing the precipitation method proved successful in the formation of hematite. X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscope (SEM) were used to characterize the synthesis product. According to the XRD results, the magnetite transition phase was obtained after precipitation, while hematite formed after calcination. The crystallite sizes were 50.5 nm, 45.4 nm, and 39 nm, respectively. According to FTIR identification, the iron oxide was generated before and after calcination in the presence of a specific Fe-O group at the wavenumbers 553 cm-1 and 451 cm-1. The SEM results revealed that the particle size ranges from 4.61 nm – 20.74 nm, and the shape was not uniform, and aggregation.

Crystallization Pathways of Iron Formations: Insights From Magnetic Properties and High-Resolution Imaging of the 2.7 Ga Carajás Formation, Brazil.

Banded iron formations (BIFs) are chemical sedimentary rocks commonly utilized for exploring the chemistry and redox state of the Precambrian ocean. Despite their significance, many aspects regarding the crystallization pathways of iron oxides in BIFs remain loosely constrained. In this study, we combine magnetic properties characterization with high-resolution optical and electron imaging of finely laminated BIFs from the 2.7 Ga Carajás Formation, Brazil, to investigate their nature and potential for preserving ancient environmental conditions. Our findings reveal that magnetite, in the form of large 0.1-0.5 mm crystals, is the main iron oxide, with an overall averaged saturation magnetization (Ms) of 25 Am2/kg (corresponding to ~27 wt% of magnetite) over the studied 230 m of the sequence. Nevertheless, the non-negligible contribution of minerals with higher coercivity suggests variable proportions of hematite along the core. Additionally, we observe non-uniform behavior in magnetite grains, with distinct populations identified through low-temperature measurements of the Verwey transition. Petrographic observations indicate that the original sediment was an Fe-Si mud consisting of a ferrihydrite-silica mixture formed in the water column. This assemblage was rapidly transformed into nano-scale hematite embedded in silica as indicated by a honeycomb structure composed of Si-spherules distributed in a microscale hematite matrix. Textural relationships show that the nucleation of magnetite started during or soon after the formation of hematite, as indicated by the preservation of the Si-spherules within magnetite cores. Further magnetite overgrowth stages are characterized by inclusion-free rims, associated with continuous Si supply during the evolving diagenetic or early metamorphic stages. These findings, combined with existing literature, suggest that ferrihydrite precipitated alongside Si and organic material, later crystallizing as hematite on the seafloor. Anaerobic respiration by Fe(III)-reducing microorganisms likely contributed to early magnetite formation in a fluid-saturated, unconsolidated sediment. Subsequent low-grade metamorphism and Si mobilization led to palisade quartz precipitation and a second stage of magnetite growth likely formed at the expense of matrix hematite through thermochemical Fe(III) reduction. Low-temperature magnetic analyses revealed that the two generations of magnetite core and rim are associated with specific stoichiometry.

Characteristics of corrosion products in low-pressure and high-pressure feedwater heaters in an operating pressurized water reactor

In this study, the characterization and comparison of corrosion products collected from the low-pressure and high-pressure heaters of an operating pressurized water reactor during the dry lay-up period indicated distinct differences in their composition and structure. Low-pressure and high-pressure feedwater heaters favored the formation of hematite and magnetite, respectively. Notably, Fe oxyhydroxides, such as goethite and lepidocrocite, were observed exclusively on the surface of the corrosion products formed in the high-pressure feedwater heater. Thermodynamic calculations confirmed the formation of Fe oxyhydroxides from Fe ions, indicating that Fe oxides such as magnetite can transform into Fe oxyhydroxides during the dry lay-up period under high humidity and oxygen-rich conditions. The results of this study could guide future research on mitigating corrosion in nuclear power plants, significantly improving their safety and efficiency.

Synthesis and evaluation of iron oxide nanoparticles from banana peel (Musa spp.) extract for the delivery of ciprofloxacin against resistant Escherichia coli

Background and objectiveResistance to antimicrobials is one of our most significant worldwide challenges. In Africa, around 31 % of the infections of urinary tract (UTIs) initiated by Escherichia coli (E. coli) have been observed to develop ciprofloxacin (CIP) resistance. As a result, significant efforts have been made to investigate novel and improved antibiotics. This study aimed at synthesizing iron oxide nanoparticles (IONPs) using banana peels (Musa Spp.) extract for delivery of CIP against resistant E. coli. MethodsA green synthesis method was used for the synthesis of IONPs using FeCl3.6H2O as a precursor and banana peel extract as a reducing and stabilizing agent. The physicochemical characteristics of the formed nanoparticles (NPs) were characterized using different methods. ResultsThe formation of hematite (α-Fe2O3) was confirmed with its FTIR characteristic peak at 461 cm−1, 542 cm−1, and 1131 cm−1. The size of synthesized IONPs was found to be 10.4 nm ± 1.98, 48 nm ± 0.9, and 67.3 nm ± 0.9 under XRD, SEM, and DLS measurements respectively. CIP-IONPs had almost the maximum drug loading capacity (33.3 % ± 0.67) with fast and slow drug release patterns at gastric and intestinal or blood pH respectively, and it had a promising resistant reversal with a zone of inhibition (ZOI) 22 mm ± 0.15 against resistance E. coli. ConclusionThe green synthesis of IONP using banana peel extract represents a novel and eco-friendly approach for the delivery of ciprofloxacin, with potential applications in addressing antimicrobial resistance.

Formation conditions and geochemistry of the Tütün Tepeleri (Baskil-Elazig/Türkiye) Fe-oxide-Cu-Au (IOCG) mineralization

The Tütün Tepeleri Fe-Oxide-Cu-Au (IOCG) mineralization is located in the Eastern Taurus Mountains (Baskil-Elazığ/Turkey) and it is associated with Baskil magmatites (diorite, gabbro and tonalite) cut by Late Cretaceous Bilaser Tepe magmatites (quartized diorite, granite, granodiorite, tonalite porphyry, monzosyenite, monzonite, aplite and diorite porphyry). Baskil Magmatites are Coniacian-Santonian (82–86 Ma), calc-alkaline in character and I-type. Bilaser Tepe Magmatics are Campanian (73–74 Ma) and represent an extensional environment after the collision of oceanic arc and the Taurus platform. In this study, the Sodic-calcic alteration zone in the Tütün Tepeleri region, which was determined as Porphyry type mineralization by different researchers, was determined for the first time and the mineralizations were evaluated in terms of Fe-Oxide-Cu-Au (IOCG) deposits. Three types of alteration zones have been identified in the region, including the sodic-calcic alteration zone. These are sodic-calcic (tremolite-actinolite, albite, epidote, chlorite, magnetite), potassic (biotite, quartz, chlorite, K-feldspar, anhydrite) and sericitic (sericite, carbonate, quartz, chlorite, illite) alterations. Sodic-calcic alteration is more widespread in the region than >1 km2, reaches thicknesses of 500 m, and is occasionally overlain by potassic alterations, just like similar Fe-Oxide-Cu-Au (IOCG) deposits in the world. Tütün Tepeleri mineralizations are in the form of rare magnetite veins with intense magnetite dispersion within the sodic-calcic alteration developed in diorites. Mineral paragenesis is in the form of magnetite, molybdenite, pyrite, arsenopyrite, chalcopyrite, sphalerite, galena, hematite, malachite and azurite, and Ti content in magnetites is determined as 0.13–0.64%. Fe content is 20.13% on average. Formation temperatures in fluid inclusions measured in ore-bearing quartz veins are 320.3 °C on average and salinity is 11.32% NaCl equivalent on average. Isotope analysis results of these mineralizations show δ34Spyrite = 6–8.9; δ34Sc.pyrite = 3.8–5.5; δ18Oquartz was determined in the range of 10.8–13.2 and δD = (−37) – (−53). When the alteration types determined with isotope analysis results showing that the mineralization occurred in a magmatic-hydrothermal system, the low Ti content in the magnetites, the formation temperature and salinity values are evaluated together, it was anticipated that Tütün Tepeleri mineralization is an example of Fe-Oxide-Cu-Au (IOCG) deposits formed in a hydrothermal-magmatic system.

Application of (U-Th)/He hematite geochronology to the Çaldağ lateritic Ni-Co deposit, Western Anatolia: Implications for multi-stage weathering events during interglacial periods/segments

Lateritic Ni-Co deposits are supergene deposits that develop due to intense weathering of the underlying ultramafic parent rocks and/or their serpentinized equivalents under tropical to sub-tropical climatic conditions. These deposits provide not only important sources of valuable metals such as iron, aluminium, nickel, and cobalt, but they also provide a proxy for paleoclimatic conditions. In this regard, geochronological studies on these deposits are critical to determine the timing of the paleoclimatic conditions, which is important for a better understanding of the paleoclimate at regional scale and for identification of favourable weathering periods that can be targeted in the exploration of undiscovered lateritic deposits in a region. In this contribution, we report hematite (U-Th)/He geochronology results from a well-preserved Çaldağ lateritic Ni-Co deposit in Western Türkiye. We sampled the different parts of the lateritic profile from the different laterite zones at the Çaldağ deposit and carried out analyses of polished thin section to determine and identify the phases of hematite formation and primary hematite formed during primary lateritization. Then, we applied scanning electron microscopy (SEM) analysis and TESCAN Integrated Mineral Analyser (TIMA) mineral mapping to identify the suitable areas on primary hematites for subsequent (U-Th)/He dating.Primary hematites are detected at the base of the lateritic profiles (transition between the limonite zone and altered serpentinite) that are only in-situ parts of the laterites exposed in two different pits in the deposit. The obtained (U-Th)/He dates of ca. 502, 206, 178, and 63 ka correspond to the interglacial periods. The three youngest (U-Th)/He dates (206, 178, and 63 ka) from the weathering front of the hematite pit become younger towards the deeper parts of the profile in the direction of weathering. The ages indicate the weathering processes should have lasted until the Quaternary with some interruptions during interglacial periods/segments, despite the fact that the main intensive lateralization period is thought to be during the Middle Eocene.This study presents the first hematite (U-Th)/He dating of lateritic Ni-Co deposits and demonstrates the reliable use of this method after a careful selection of hematite samples. Our results suggest that, in contrast to the short-living lateritization model for lateritic Ni-Co deposits, they may have a multi-stage weathering history throughout their long-lasting development. In addition, the study showed that it has huge potential for the dating of lateritization and weathering processes that are related to paleoclimatic events. Finally, knowledge of the favourable paleoclimatic periods of chemical weathering in a region may help in determining the potential areas for ultramafic exposures for discovering new lateritic deposits.

Variations in aridity across the Asia–Australia region during the Neogene and their impact on vegetation

Scientific drilling provides extended records of continental environmental conditions during the Neogene in Asia and northern Australia. Spectral data allow reconstruction of the environment using abundances of hematite and goethite. Hematite formation is favoured by dry or seasonal conditions. Hemipelagic sites show the most regular records. Monsoon strengthening started in the Early Miocene and peaked at 17–20 Ma in the Bay of Bengal and at 10–15 Ma in southern China before weakening after c. 12 Ma and c. 10 Ma, respectively. The Indus Basin dried after c. 8 Ma and again after 3 Ma, while aeolian sediment sources to the Sea of Japan show increased aridity after 5 and 3 Ma. The Mekong Fan indicates increasing aridity after 6 Ma, similar to Eastern Australia. In contrast, NW Australia shows a trend towards wetter conditions after 8 Ma, with a humid period at 4–6 Ma followed by drying. There is a link between drying and vegetation in the Mekong and Pearl River basins, as well as Eastern Australia. Monsoon strengthening is linked to topographic uplift in the Himalaya, together with Tethyan gateway closure. Long-term drying is likely driven by global cooling since the Middle Miocene.

Experimental conditions for room temperature ferromagnetism in Fe-doped SnO2 via mechanochemical milling and thermal treatment

Identifying optimal experimental conditions, preferably through a simple and cost-effective method, for the fabrication of oxide-diluted magnetic semiconductors, such as Fe-doped SnO2, holds great significance in the quest for spintronic materials operating at room temperature (RT). While mechanochemical milling is a well-established technique meeting these requirements, its numerous milling variables necessitate careful consideration of restricted experimental conditions. In this study, we present some experimental mechanochemical milling conditions to prepare impurity-free iron-doped tin dioxide nanoparticles exhibiting RT ferromagnetic signal. To achieve this, we investigated the effects of milling time, the choice of the starting Sn reactant, and iron concentration on the purity of Sn1−xFexO2 (x = 0, 0.03, and 0.05) nanopowders obtained through mechanochemical milling followed by thermal treatment. Characterization through XRD, XANES, and EXAFS at the Fe K-edge, RT Raman spectroscopy, 119Sn and 57Fe Mössbauer spectroscopies, and magnetic measurements was conducted. Among the experimental techniques, micro-Raman spectroscopy proved the most effective in detecting the formation of hematite as an impurity phase. Our results indicate that extending the milling time to 12 h, as opposed to 3 h, employing anhydrous SnCl2, instead of SnCl2·2H2O and using the low iron concentration of x = 0.03, results in proper conditions for producing impurity-free samples with a robust RT ferromagnetic signal. The oxidation states for iron and tin ions were determined to be 3+ and 4+, respectively, with both occupying octahedral sites, suggesting iron’s replacement of tin. Our findings propose that both the bound magnetic polaron and RKKY models offer potential explanations for the origin of the ferromagnetic signal observed at room temperature in Sn0.97Fe0.03O2 sample milled for 12 h.

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 > 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 <Fe2+–O>6.

In-situ and ex-situ experimental investigation on the chalcopyrite replacement in saline solution at 310-365°C and 15-25 MPa

Abstract The replacement of chalcopyrite in NaCl solutions was investigated from 310 to 365° and 15 to 25 MPa with ex-situ surface characterization techniques and in-situ electrochemical methods. The replacement products and reactions were analyzed ex-situ using Raman spectroscopy, scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDS). Chalcopyrite dissolution was monitored by open circuit potential (OCP), polarization curves and electrochemical impedance spectroscopy (EIS). The ex-situ and in-situ measurements show that: (i) elevated temperature and pressure promote the oxidative dissolution of chalcopyrite by different pathways; (ii) the altered chalcopyrite surface consists of an outer layer of hematite and an inner layer of covellite; (iii) at elevated temperature, removal of more copper from chalcopyrite surface enhances chalcopyrite dissolution, and favors hematite formation over covellite in the alteration rind; and (iv) at elevated pressure, more iron ions diffuse through the passive covellite layer by point defects, promoting chalcopyrite replacement by covellite over hematite. This study provides experimental evidence on the replacement of chalcopyrite by covellite, the precipitation of hematite and the exchange of Fe/Cu ions between chalcopyrite and hydrothermal brine.

Laboratory VIS–NIR reflectance measurements of heated Vesta regolith analogs: Unraveling the spectral properties of the pitted impact deposits on Vesta

AbstractPitted impact deposits on Vesta show higher reflectance and pyroxene absorption band strengths compared to their immediate surroundings and other typical Vestan materials. We investigated whether heating to different temperatures for different durations of Vestan regolith analog materials can reproduce these spectral characteristics using mixtures of HEDs, the carbonaceous chondrite Murchison, and terrestrial analogs. We find no consistent spectral trend due merely to temperature increases, but observed that the interiors of many heated samples show both higher reflectance and pyroxene band I strength than their heated surfaces. With electron probe microanalysis, we additionally observe the formation of hematite, which could account for the higher reflectance. The presence of hematite indicates oxidation occurring in the sample interiors. In combination with heat, this might cause the increase of pyroxene band strengths through migration of iron cations. The effect grows larger with increasing temperature and duration, although temperature appears to play the more dominant role. A higher proportion of Murchison or the terrestrial carbonaceous chondrite analog within our mixtures also appears to facilitate the onset of oxidation. Our observations suggest that both the introduction of exogenic material on Vesta as well as the heating from impacts were necessary to enable the process (possibly oxidation) causing the observed spectral changes.

Transformation of Precursor Iron(III) Minerals in Diagenetic Fluids: Potential Origin of Gray Hematite at Vera Rubin Ridge

AbstractCoarse‐grained (>3–5 μm) gray hematite particles occur at Vera Rubin ridge (VRR) within Gale crater, Mars. VRR has likely undergone multiple episodes of diagenesis, at least one of which resulted in the formation of gray hematite. The precursor mineralogy and nature of the diagenetic fluids that produced coarse‐grained hematite remain unknown. Analog laboratory experiments were performed on a variety of iron(III) minerals to assess the potential fluid conditions and precursor mineralogy that form coarse‐grained hematite. Gray hematite formed from the transformation of jarosite after 20 days at 200°C. Conversion was complete in chloride‐rich fluids; however, modeling indicates that at lower jarosite‐to‐water ratios, conversion is complete even in chloride‐free, sulfate‐rich conditions. No transformations of jarosite occurred when aged at 98°C. All other precursor minerals (akaganeite, ferrihydrite, goethite, and schwertmannite) did not transform or produced red, fine‐grained hematite under all conditions assessed. Additionally, seeding precursor iron(III) phases with red hematite and coarsening pre‐existing red hematite failed to produce gray hematite. These results suggest that jarosite could have been the precursor of gray hematite at VRR and that transformation is possible in both sulfate‐bearing and chloride‐bearing fluids. Jarosite produces gray hematite because the acidic conditions it generates yield both a low degree of hematite supersaturation, producing few nuclei, and high dissolved iron concentrations, enabling rapid hematite growth. Gray hematite readily forms under oxic conditions and its occurrence at VRR is not a marker for a redox interface. The associated diagenetic event was thus unlikely to have generated substantial new chemical energy for life.

Research on Hydrothermal Iron Removal From Wet Zinc Refining Solutions and Iron Residue Reduces Emissions

For the conventional wet zinc refining processes of the jarosite method and goethite method of iron removal, the process that existed was iron residue low iron, high zinc, large amount of residue, and high cost of harmless treatment, this paper carried out a study on hydrothermal iron removal from wet zinc refining solutions and an iron residue that reduces emissions. The results show that the reaction temperature is a prerequisite for the precipitation of Fe3+ to precipitate hematite (Fe2O3). Prolonging the reaction time can induce the conversion of jarosite (KFe3(SO4)2(OH)6) to hematite. Increasing the partial pressure of oxygen will accelerate the oxidation of Fe2+ to Fe3+ and promote the formation of the hematite phase. Under the optimized technical parameters of reaction temperature 180 °C, oxygen partial pressure 0.6 MPa, reaction time 3 h, and controlled alkali metal ion concentration, 92.49% of the iron in the solution was precipitated into the residue in the form of hematite(Fe2O3), and the precipitated iron residue contained 57.75% iron and 0.82% zinc; compared with the jarosite process, the amount of iron residue was reduced by about 65%, and the zinc content of iron residue was reduced by 5.86%. The use of hydrothermal mineralization iron precipitation processes can realize the mineralization precipitation of iron in solution under low-acid conditions and obtain hematite iron precipitation residue with iron content up to the industry standard of iron oxide. And can be realized for resource utilization, helping the wet process zinc industry to develop in a green and low-carbon direction.

Influence and Mechanism Study of Soil Moisture on the Stability of Arsenic-Bearing Ferrihydrite in Surface Soil Vertical Profiles

Ferrihydrite is usually used as a remedy for arsenic (As)-contaminated soil due to its strong affinity and large specific surface area. However, its noncrystalline phase makes it unstable in long-term applications in the soil. In this study, a soil incubation experiment was designed using the diffusive gradient in thin film (DGT) technique and spectral techniques to investigate the fate of As-bearing ferrihydrite [As(V)-Fh] after long-term incubation at different soil water holding capacities (SWHCs). After As(V)-Fh (0.05 and 0.005 As/Fe molar ratio) was incubated in soil for 360 days, both DGT-derived labile As and Fe were released at 70% SWHC and 120% SWHC into the soil (at a vertical depth of 12 cm). The concentrations of DGT-As and DGT-Fe increased with incubation time and were greater at 120% SWHC. The results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that As(V)-Fh gradually transformed into hematite and goethite after 360 days of incubation. Goethite was mainly found in the 120% SWHC treatment after 180 days. Hematite and goethite formation rates were greater in the 120% SWHC treatment and in the bottom soil layer. Mechanistic analysis based on X-ray photoelectron spectroscopy (XPS) revealed that the variation in soil pH and the formation of Fe(II) (under flooded water conditions) are the two key factors promoting the formation of hematite (dehydrogenation and dehydration) and goethite (As(V)-Fh dissociation and reorganization). The As release mainly occurred due to the loss of adsorption sites. Thus, it is recommended that ferrihydrite be applied in paddy–dry rotations or dry-field patterns to effectively avoid the loss of As(V)-Fh in long-term-saturated soil.

A New Perspective on the Applicability of Diffuse Reflectance Spectroscopy for Determining the Hematite Content of Fe-Rich Soils in the Tropical Margins of China

Hematite and goethite are widely occurring chromogenic iron oxides in soils and sediments that are sensitive to climatic dry/wet shifts. However, only by accurately quantifying the content or ratio of hematite and goethite can they be applied reliably to palaeoclimate reconstruction. Compared to the Loess Plateau of China, hematite in the soils of southern China has not been sufficiently studied. We used diffuse reflectance spectroscopy (abbreviation DRS, including the first-derivative curves and the second-derivative curves of the Kubelka–Munk remission functions), combined with ignition at 950 °C, and X-ray fluorescence (XRF) to quantify the hematite content of four tropical-margin iron-rich soil profiles with different matrix compositions in the Leizhou Peninsula, China. We also examined the application of hematite quantification parameters in soils with different matrix compositions under the same climatic conditions. Our main findings are as follows: (i) DRS first-derivative curves can reflect the presence of goethite and hematite in soils, and their relative contents can be compared within the same profile. (ii) The second-derivative curve of the Kubelka–Munk remission functions can reflect the relative proportions of goethite and hematite and provide information about the degree of Al substitution. (iii) Combined with calibration equations, soil redness can reliably quantify the hematite content, but it is necessary to consider the effect of mucilage envelopes in the process of hematite formation. Additionally, we summarize various methods used for quantifying hematite, and the influence of soil matrix compositions, with the aim of providing a reference for hematite quantification elsewhere. We also propose a new indicator (ΔHmRed/HmRed) to help detect iron hydroxide/iron oxide changes in soils.

Degradation of enoxacin with different dissociated species during the transformation of ferrihydrite-antibiotic coprecipitates

Ferrihydrite acts as a natural reservoir for nutrient elements, organic matter, and coexisting pollutants through adsorption and coprecipitation. However, the degradation of emerging fluoroquinolone antibiotics during the transformation of ferrihydrite coprecipitates, especially those with various dissociated species, remains insufficiently explored. In this study, Enoxacin (ENO), employed as a model antibiotic, was introduced to prepare ferrihydrite-ENO coprecipitates. The influence of coprecipitated ENO on the transformation of the ferrihydrite-ENO coprecipitate was investigated across different pH conditions. The results revealed that ferrihydrite-ENO coprecipitates thermodynamically transformed into more stable goethite and/or hematite under all pH conditions. In neutral and alkaline conditions, ENO promoted the transformation of coprecipitates into goethite while hindering hematite formation. Conversely, under acidic conditions, ENO directly obstructed the transformation of coprecipitates into hematite. Different dissociated species of ENO displayed distinct degradation pathways. The cationic form of ENO exhibited a greater tendency for hydroxylation and defluorination, while the zwitterion form leaned toward piperazine ring oxidation, with limited preference for quinolone ring oxidation. The anionic form of ENO exhibited the fastest degradation rate. It is essential to emphasize that the toxicity of the degradation products was intricately connected to the specific reaction sites and the functional groups they acquired post-oxidation. These findings offer fresh insights into the role of antibiotics in coprecipitation, the transformation of ferrihydrite coprecipitates, and the fate of coexisting antibiotics.

Enhanced removal of iron from iron-rich manganese ore leaching solution: A promising strategy by seed-induced

Enhanced removal of iron from iron-rich manganese ore leaching solution has become a bottleneck limiting the development of the electrolytic manganese industry. Herein, iron-rich electrolytic manganese residue (IREMR) as a seeding to enhance iron removal. The results showed that the iron removal efficiency was 99.97 % with only manganese loss of 1.5 % whenadding 1 g/L IREMR. Compared with the traditional conditions of electrolytic metal manganese enterprise, it demonstrated several environmental advantages: lower manganese loss (from 16 % to 1.5 %), less IREMR produced (64.45 %), faster filtration speed (from 0.0013 to 0.1966 mL/s.cm2). Based on multiphase equilibria modelling and strengthening mechanism analysis, enhanced iron removal by seed-induced can reduce the formation of ammonium-alum complex salts and prevent the formation of Fe(OH)3 colloid. In addition, IREMR as seeding applied in the iron removal process can accelerate the formation of goethite and hematite to shorten the nucleation cycle. This strategy is important for source reduction and resource utilization of electrolytic manganese residue.