Iron Carbon Research Articles

Carbon Fate, Iron Dissolution, and Molecular Characterization of Dissolved Organic Matter in Thawed Yedoma Permafrost under Varying Redox Conditions.

Permafrost soils store ∼50% of terrestrial C, with Yedoma permafrost containing ∼25% of the total C. Permafrost is undergoing degradation due to thawing, with potentially hazardous effects on landscape stability and water resources. Complicating ongoing efforts to project the ultimate fate of deep permafrost C is the poorly constrained role of the redox environment, Fe-minerals, and its redox-active phases, which may modulate organic C-abundance, composition, and reactivity through complexation and catalytic processes. We characterized C fate, Fe fractions, and dissolved organic matter (DOM) isolates from permafrost-thaw under varying redox conditions. Under anoxic incubation conditions, 33% of the initial C was lost as gaseous species within 21 days, while under oxic conditions, 58% of C was lost. Under anoxic incubation, 42% of the total initial C was preserved in a dissolved fraction. Lignin-like compounds dominated permafrost-thaw, followed by lipid- and protein-like compounds. However, under anoxic incubation conditions, there was accumulation of lipid-like compounds and reduction in the nominal oxidation state of C over time, regardless of the compound classes. DOM dynamics may be affected by microbial activity and abiotic processes mediated by Fe-minerals related to selective DOM fractionation and/or its oxidation. Chemodiversity DOM signatures could serve as valuable proxies to track redox conditions with permafrost-thaw.

Evaluation of industrial byproduct iron ore tailings and carbon fiber cement-based materials under sulfate freeze-thaw cycles: Durability, piezoresistivity, and microscopic mechanism

This study investigated the feasibility of utilizing industrial byproduct iron ore tailings and carbon fiber cement-based materials (ICCM) in sulfate freeze-thaw (F-T) environments. The effects of carbon fiber (CF) and iron ore tailing (IOT) on the sulfate F-T resistance, piezoresistivity, and pore distribution were tested. The results revealed that CF (0.6 vol%) and IOT (30%) significantly improved the compressive strength (51.6 MPa) and resistance to sulfate F-T of ICCM. The stress sensitivity was obviously enhanced to 1.389 %·MPa−1. Furthermore, the stress sensitivity is closely related to the sulfate F-T environment. After the sulfate F-T cycles, the fractional change in resistivity (FCR) and compressive stress agreed with a first-order exponential decay relationship. Replacement with IOT compensated for the degradation in piezoresistivity by formation of balanced pore distribution over 200 F-T cycles. The combination of IOT and CF in cement material yields excellent performance in terms of stress sensing, cost, and environmental impact (EI). This approach is expected to be developed for self-sensing in extreme environments with a recycled conductive filler.

Constraining reducing conditions in the Prague Basin during the late Silurian Lau/Kozlowskii extinction event

The Silurian was marked by repeated extinctions, carbon cycle volatility and significant intervals of climatic change. The most notable of these events were the Ludfordian Lau/Kozlowskii extinction and the associated Mid-Ludfordian Lau C isotope excursion, both of which have been linked to a period of global cooling and expanded reducing conditions in the global ocean. We present new data that characterize the marine palaeoredox conditions of the Prague Basin, a peri-Gondwanan terrane. We use I/Ca ratios to assess the local redox conditions in a shallow water carbonate succession and Fe speciation and redox-sensitive trace element concentrations to assess the local redox conditions of a deeper water sequence. Consistently low I/Ca values in the shallow water section suggest either persistent local low-oxygen conditions or possibly diagenetic overprinting. Fe speciation data suggest that the bottom water redox conditions in the deeper shelf setting were consistently anoxic with possible intermittent euxinia. Concentrations of redox-sensitive trace elements consistently higher than upper continental crust values also indicate persistent reducing conditions in the deeper part of the basin. These local redox proxy data from the Prague Basin, including trends in new pyrite S isotope ( δ 34 S pyr ) data, are consistent with previous findings of the expansion of anoxic and/or euxinic oceanic conditions. These data, derived from a mid-palaeolatitude marine setting, fill an important gap in our current global dataset for this interval of the late Silurian. Supplementary material: All the geochemical data reported and discussed herein are available in the Supplemental Data Tables at https://doi.org/10.6084/m9.figshare.c.7008107 Thematic collection: This article is part of the Chemical Evolution of the Mid-Paleozoic Earth System and Biotic Response collection available at: https://www.lyellcollection.org/topic/collections/chemical-evolution-of-the-mid-paleozoic-earth-system

Copper–Iron Selenides Nanoflakes and Carbon Nanotubes Composites as an Advanced Anode Material for High‐Performance Lithium‐Ion Batteries

Metal selenides are widely considered as an emerging anode electrode material for lithium‐ion batteries (LIBs). Hence, the present study uses a conductive carbon materials matrix such as carbon nanotubes (CNTs) with copper–iron selenide (CuFeSe2). The composites (CuFeSe2@CNTs) are synthesized by a hydrothermal method and examined for electrochemical performance as anode applications in LIBs. Herein, the CuFeSe2@CNTs show excellent specific capacity of 783.7 and 720.6 mA h g−1 at 0.1 and 1 A g−1, respectively. This composite further exhibits a high‐capacity value compared to only FeSe2 and CuFeSe2 and a reversible capacity of 691 mA h g−1 after 200 cycles at 1 A g−1 current density. Moreover, the homogeneous combination of CuFeSe2 nanoflakes and CNTs provides structural stability that reduces the volume change during lithium‐ion interactions and successively improves the conductivity of the complex, which is advantageous for better ion and electron kinetics during the reaction.

Analysis of Early Iron Sulfide, Carbonate, and Phosphate Mineral Analogues Produced by Flow-Driven Precipitation in a Microchannel.

Most of the chemical and physical interactions of interest to the astrobiology community are influenced by the mineralogy of the systems under consideration. Often, this mineralogy occurs in sediment or sediment-like aqueous microenvironments in which the early minerals differ dramatically from the mature version that results from a long diagenesis, which are tied to complex interactions of pH, redox state, concentration, and temperature. This interconnectedness is difficult to reproduce in a laboratory setting yet is essential to understanding how the physical and chemical demands of living systems alter and are altered by their geological context. We present a facile means for producing precipitated mineral analogues within a microchannel and demonstrate its analytical efficacy through instrumental and modeling techniques. We show that amorphous, early-stage analogues of iron sulfide, iron carbonate, and iron phosphate can be formed at the boundary between flowing solutions, modeled on the microscale, and analyzed by standard instrumental techniques such as scanning electron microscopy/energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy.

Geochemistry of iron and trace metals in seep carbonates of the middle Okinawa Trough impacted by hydrothermal plumes

Geochemistry of iron and trace metals in seep carbonates and its dependence on anaerobic oxidation of methane (AOM)-driven diagenesis in cold seeps are not well documented. Here we characterize geochemistry of Fe and trace metals in carbonate nodules collected at an active cold seep in the middle Okinawa Trough (OT) impacted by hydrothermal plumes. The carbonate nodules in the studied core are dominated by aragonite even at sulfate-low core bottom. Most aragonite at the core bottom may have formed much earlier close to the seafloor under high sulfate concentration. Additionally, porewater at the depth may not be developed to a condition for the formation of calcite dominating over aragonite due to constant downward replenishment of sulfate across through shallow SMTZ (40 cm below sediment surface). As indicated by δ13C and δ18O of the carbonates, anaerobic oxidation of thermogenic methane from gas hydrate dissociation is the dominant fluid source for carbonate precipitation. It can be inferred from the existence of vivianite that Fe reduction coupled to AOM (Fe-AOM) may have ever been prevalent at the hydrothermal Fe-impacted seep site. Enhanced inputs of Mo, Co, Cu, Ni, and Zn associated with hydrothermal Fe-oxyhydroxides-organic colloids is the main source for their high enrichment in the carbonate nodules, and clay minerals and AOM-related microbial organics may have played an important role in their partitioning in the nodules. Uranium enrichment in the carbonate nodules is mainly through enhanced U delivery associated with Fe-oxyhydroxides-scavenged organic colloids and additional U enrichment induced by U(VI) reduction. U(IV) incorporation into carbonate lattices dominates U partitioning in the carbonate nodules over the upper 60 cm of the seep sediments, but the incorporation is substantially dampened at depth due to an increase in concentration of dissolved inorganic carbon, which consequently may have rendered U(IV) adsorption on clay minerals as the important U sink in the nodules. Our results suggest that the exceptional enrichments of Co, Cu, Ni, Zn, Mo, and U in seep carbonates may be used as a paleo-proxy to differentiate cold-seep carbonates whose formation has been co-impacted by hydrothermal plumes.

Research on the Influencing Factors of Iron and Steel Carbon Emission Right Trading Price and Trading Mechanisms

Research on the Influencing Factors of Iron and Steel Carbon Emission Right Trading Price and Trading Mechanisms

Adding Granular Activated Carbon and Zerovalent Iron to the High-Solid Anaerobic Digestion System of the Organic Fraction of Municipal Solid Waste: Anaerobic Digestion Performance and Microbial Community Analysis.

Anaerobic digestion (AD) performance and microbial dynamics were investigated in a high-solid anaerobic digestion (HSAD) system of the organic fraction of municipal solid waste (OFMSW). 1, 5, 10, and 15% (w/w, dry weight of the OFMSW) of granular activated carbon (GAC) and zerovalent iron (ZVI) were added to the HSAD system. The results showed that adding ZVI and GAC can improve the methane yield of the OFMSW. Notably, R-(GAC + ZVI) exhibited the highest cumulative methane yield of 343.0 mL/gVS, which was 57.1% higher than that of the R-control. At the genus level, the dominant bacteria included norank_f__norank_o__MBA03, norank_f__norank_o__norank_c__norank_p__Firmicutes, Fastidiosipila, norank_f__Rikenellaceae, and Sphaerochaeta, while Methanoculleus, Methanobacterium, and Methanosarcina were the dominant archaea. The highest relative abundance of norank_f__norank_o__norank_c__norank_p__Firmicutes was 30.8% for the R-(GAC + ZVI), which was 71.4% higher than that of the R-control. The relative abundance of Methanoculleus and Methanobacterium for the R-(GAC + ZVI) and the R-control group accounted for 79.0 and 90.8% of the total archaeal abundance, respectively. Additionally, the relative abundance of Methanosarcina was 10.6% for R-(GAC + ZVI), which was higher than that of the R-control (1.1%). After the addition of GAC and ZVI, the electron transfer capacity of the HSAD system was enhanced, resulting in promoted methane production. Thus, the simultaneous addition of GAC and ZVI to the HSAD system can be an effective strategy to promote the cumulative methane yield of the OFMSW.

Genome-wide screen reveals cellular functions that counteract rifampicin lethality in Escherichia coli.

Rifamycins are a group of antibiotics with a wide antibacterial spectrum. Although the binding target of rifamycin has been well characterized, the mechanisms underlying the discrepant killing efficacy between gram-negative and gram-positive bacteria remain poorly understood. Using a high-throughput screen combined with targeted gene knockouts in the gram-negative model organism Escherichia coli, we established that rifampicin efficacy is strongly dependent on several cellular pathways, including iron acquisition, DNA repair, aerobic respiration, and carbon metabolism. In addition, we provide evidence that these pathways modulate rifampicin efficacy in a manner distinct from redox-related killing. Our findings provide insights into the mechanism of rifamycin efficacy and may aid in the development of new antimicrobial adjuvants.

Improving wear performance, physical, and mechanical properties of iron sand/epoxy composite modified with carbon powder

This study was conducted to investigate the usage of iron sand as composite reinforcement. The addition of carbon powder with variations of 15 wt%, 20 wt%, and 30 wt% is expected to enhance the interfacial bond between iron sand and epoxy matrix to be better. Physical and mechanical properties of the composite were investigated using a wear resistance test Pin on Disc method, shore-D hardness, bending test, X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) and Scanning Electron Microscope (SEM). The results showed an increase in wear resistance and mechanical properties of composite due to the addition of carbon powder. This was confirmed by the fact that the HCP composite with 30 wt% carbon powder showed a good increase in wear resistance but a reduction in flexural properties and hardness values. Meanwhile, the LCP composite with 20 wt% carbon powder was recommended in terms of good flexural properties. The increased mechanical properties of composite were supported by composite crystallinity index value recorded to be 59.45 % from the XRD test. SEM analysis showed better dispersion and interfacial bonding for carbon powder and iron sand in the composite matrix. These results are expected to contribute to the new development of composite brake pad.

Controls on mechanical properties of a carbonate mudstone: Insights from non-destructive techniques and geochemical data

This study quantifies geomechanical properties of carbonate mudrocks in the Arabian intra-shelf basin, focusing on different sedimentologic zones (proximal to distal). Core-based mechanical properties were obtained through unconfined conditions. Micro Rebound Testing (MRT) was conducted on 700′ ft of core at 0.5 ft intervals to capture high-resolution rock hardness (HLD), unconfined compressive strength (UCS), and static Young's Modulus (E). Additional tests validated log-based parameters, including impulse hammer, acoustic velocity testing for (E), P-wave and S-wave velocities (Vp and Vs), scratch testing, and XRF/XRD analyses for mineralogical and elemental variability impact on mechanical properties.Multivariate statistical analysis correlates mechanical properties with elemental data, showing direct proportionality to calcium percentage, (E), Vp, and Vs, while inversely correlated to aluminum, iron, sulfur, and total organic carbon (TOC), especially in distal zones. Porosity, as measured by neutron porosity log, is a significant control on mechanical properties, with higher porosity resulting in lower mechanical properties at any given calcium percentage. Variations in geomechanical properties within each zone are principally controlled by depositional environments, sediment supply, diagenesis, and a pycnocline dividing the water column into anoxic, dysoxic (or suboxic), and oxic conditions.Zone 1A and 4 exhibit high brittleness characterized by high Ca-calcite, HLD, (E), Vp, Vs., low terrigenous elements/minerals, and porosity. Zone 1B and 2A are moderately brittle, showing a slight decrease in brittleness and a slight increase in terrigenous elements/minerals, porosity, and organic matter, particularly in the distal zone (Zone 1B). Zone 2B, 3A, and 3B represent moderate to highly ductile zones with low levels of Ca-calcite, HLD, (E), Vp, Vs, and an increase in terrigenous elements/minerals, porosity, and TOC, especially in the distal zone (Zone 2B and 3B). This study highlights the value of high-resolution mechanical data from cores with applications for improved stress estimation and hydraulic fracture stimulation in unconventional reservoirs.

Mazon Creek fossils brought to you by coal, concretions and collectors

Abstract The late Carboniferous (Middle Pennsylvanian, ∼307 Ma ago) Mazon Creek Lagerstätte found in northern Illinois, USA, is unique for its exceptional biotic diversity as well as the human endeavours, both professional and avocational, that brought vast numbers of fossils and new species to science. In 1997, the Mazon Creek Fossil Beds, exposed along the Mazon River near Benson Road, Morris, IL, became a National Historic Landmark. The fossils are preserved in siderite (iron carbonate, FeCO 3 ) concretions within the lower 3–8 m of the Francis Creek Shale Member of the Carbondale Formation, and often retain outlines of original soft tissues. The Mazon Creek biota includes over 465 animal and 350 plant species representing more than 100 orders, which is attributed to the preservation of organisms from multiple habitats and the large number of specimens collected. That phenomenon was made possible by coal extraction bringing concretions to the surface and highly motivated amateur collectors pursuing them. Some of the formerly mined areas continue to draw collectors and are preserved as part of the Mazonia-Braidwood State Fish and Wildlife Area. The fossils, fossil collectors and collection sites are a significant part of the cultural and scientific geoheritage.

Hydrogen-driven routes to steel from siderite with low CO2 emissions: A modeling study

Efficient use of low-grade siderite minerals can not only potentially mitigate the shortage of iron ores but also enable drastic reduction in CO2 emissions from steel industry in China. In this study, we conducted a systematic thermodynamics analysis toward ferrous carbonate hydrogenation to CH4, which was verified by experimental study over the 5 wt.% Ni/siderite. CO2 hydrogenation reduction was introduced in steelmaking from siderite minerals to further reduce the CO2 emissions. Based on thermodynamic analysis results, we provided four options of hydrogen-driven route to steel from siderite named FTI-CO2HR, FTM-MTI-CO2HR, FTH-HTI-CO2HR and FTW-WTI-CO2HR, respectively. The FTM-MTI-CO2HR process route achieved minimized CO2 emissions (0.56 metric ton CO2/metric ton iron) and was competitive to the steel scrap-EAF route (0.54–0.60 metric CO2/metric ton iron). The proposed process route would be cleaner, more environment friendly assuming successful technology and process development and favorable market conditions in terms of acceptable level of hydrogen production cost.

Dual therapy for the eradication of bacterial biofilms: Iron oxide nanoparticles and carbon dots as magnetic actuator and photothermal agents

Nanohybrids based on maghemite iron oxide nanoparticles (IONPs) and carbon dots (CDs), with different linkers between the two components, are synthesized, with the idea of combining several properties (magnetic and optical) in one nanomaterial in order to eradicate bacterial biofilm. The photothermal capacities of these materials are expressed by two parameters: the specific absorption rate (SAR) and the photothermal light-to-heat conversion constant (η). They show that the IONP/CD combination is more effective in photothermia (PT) than either of the components, but depends on the linkage (amide > ester > electrostatic). The antibacterial properties of the nanohybrids are first determined for the exponential and stationary growth phases of planktonic S. aureus and B. subtilis with and without PT. In the absence of PT, no nanohybrid has any significant bactericidal effect, but with PT the nanohybrids have different activities, with the IONP-amide-CD pattern the most effective. Combining magnetic actuation and PT on B. subtilis biofilms shows a synergistic effect and reveals the advantages of using such nanohybrid materials for killing bacteria and eradicating biofilm.

Effects of iron oxide and carbon nanotube contents on mechanical properties and shape memory behavior of biocompatible and biodegradable shape memory polymers

AbstractThe shape memory polymers (SMPs) is a potential alternative material for conventional shape memory alloys (SMAs) in various fields. Previous studies have focused on the application of SMPs materials as an alternative to SMAs. However, considering problems such as the poor mechanical properties, its application has been limited. This study developed a biodegradable, magnetically responsive SMPs material that can be used for medical implants with shape memory behavior under magnetic force and improved mechanical properties by adding nanoparticles. Moreover, effect of the added nanoparticle was investigated due to contents ratio. Nanocomposite was synthesized with polycaprolactone which has shape memory properties, Fe3O4 that generates heat under magnetic field, and carbon nanotubes with reinforcing effect. The morphology analysis confirmed the homogeneous dispersion of the Fe3O4/Carbon‐nanotubes (CNTs) in polymer matrix. The tensile test shows that tensile strength (14.9–17.6 MPa) increased when Fe3O4 (0–20 wt%) was included and that it did not increase significantly when CNTs (0–0.8 wt%) were included. The shape memory test result confirmed that developed composite had a shape memory under a magnetic field. It was confirmed that even if Fe3O4 was incorporated into polycaprolactone, did not lose its exothermic properties under magnetic field. The developed polymer showed high shape memory ratio (91%–98%) in all the nanoparticle content rates. With regard to biodegradability, weight loss occurred over time in the phosphate‐buffered saline solution. Therefore, the biocompatible, biodegradable, magnetic response shape memory polymer developed in this study might applied to various medical implant as advanced shape memory materials.

Dual-modality probe nanodrug delivery systems with ROS-sensitivity for atherosclerosis diagnosis and therapy.

Most acute cardiovascular and cerebrovascular diseases are caused by atherosclerotic plaque rupture leading to blocked arteries. Targeted nanodelivery systems deliver imaging agents or drugs to target sites for diagnostic imaging or the treatment of various diseases, providing new insights for the detection and treatment of atherosclerosis. Based on the pathological characteristics of atherosclerosis, a hydrogen peroxide-sensitive bimodal probe PPIS@FC with integrated diagnosis and treatment function was designed. Bimodal probes Fe3O4@SiO2-CDs (FC) were prepared by coupling superparamagnetic iron oxide and carbon quantum dots synthesized with citric acid, and self-assembled with hydrogen peroxide stimulus-responsive amphiphilic block polymer PGMA-PEG modified with simvastatin (Sim) and target molecule ISO-1 to obtain drug-loaded micelles PGMA-PEG-ISO-1-Sim@FC (PPIS@FC). PPIS@FC could release Sim and FC in an H2O2-triggered manner, achieving the goal of releasing drugs using the special microenvironment at the plaque. At the same time, in vivo magnetic resonance and fluorescence imaging results proved that PPIS@FC possessed targeting ability, magnetic resonance imaging and fluorescence imaging effects. The results of the FeCl3 and ApoE-/- model showed that PPIS@FC had an excellent therapeutic effect and in vivo safety. Therefore, dual-modality imaging drug delivery systems with ROS response will become a promising strategy for the diagnosis and treatment of atherosclerosis.

Optimal composition of paste composite electrodes based on glassy carbon matrix and iron oxides.

Optimal composition of paste composite electrodes based on glassy carbon matrix and iron oxides.

Remoção de H2S de biogas por adsorção em carvão ativado comercial e oxido de ferro granular

ABSTRACT Among the impurities that are harmful to the energy conversion of biogas generated in landfills is hydrogen sulfide (H2S). The present study compared the efficiency of H2S removal with the use of granular activated carbon (GAC) of two commercial brands, Norit GAC and Pelegrini GAC, and with the use of granular iron oxide from mineral residues. The tests were conducted on a laboratory scale, in a glass column, filled with filtering material, applying an inlet flow of gas and monitoring the outlet concentration. The best removal efficiencies occurred with the use of Norit GAC, which presented longer rupture times. Wet gas tests were also carried out, in which rupture and equilibrium times increased with the use of Norit GAC, while with the use of Pelegrini GAC the same adsorptive behavior was not observed. Tests with iron oxide showed low potential for H2S removal due to reduced specific surface values, although it provided removal of the contaminant. Knowledge of the saturation time and adsorption equilibrium data is essential for a better understanding and planning of adsorption systems, in addition to the conduction of studies on the influence of external factors and variations in initial concentration.

Research Investigates and Simulation Behavior of the Failure Characteristics of Red Mud–Loess Type Permeable Reactive Barriers PRB in Fixed‐Bed Column Experiments

Controlling and remediating water and soil pollution while efficiently utilizing solid waste is essential for comprehensive environmental protection and sustainable development, particularly in establishing green, low‐carbon economic systems in China. We evaluate the impact of initial concentration, flow rate, and bed height on breakthrough performance and adsorption capacity using the Tessier method under dynamic water flow conditions. Additionally, we analyze micromorphological changes in the red mud–loess mixture before and after breakthrough by acid mine drainage containing Pb and Cd in mining areas, employing soil column experiments and numerical simulations with COMSOL Multiphysics. Our findings suggest that reducing initial concentration and flow rate while increasing bed height leads to higher breakthrough time, saturation time, and adsorption capacity for Pb and Cd in the red mud–loess mixture (7 : 3). Furthermore, the red mud–loess blend (7 : 3) demonstrates sustained and efficient acid‐buffering capability in the presence of acid mine drainage containing Pb and Cd. Notably, under specific conditions (initial Pb content at 100 mg/L, a height of 7 cm, and flow rate set at 1 mL/min), the adsorption capacity of red mud–loess (7 : 3) reaches 17.30 mg/g. The prescribed minimum length for PRBs is 11.40 cm. Under specified conditions (Cd concentrations at 100 mg/L, a height of 5 cm, and a flow rate of 1 mL/min), the material exhibits a notable adsorption capacity of 29.91 mg/g, with a theoretical minimum length for PRBs at 8.95 cm. Increasing bed heights successfully remove Pb and Cd ions through chemical precipitation. The BDST model accurately describes the breakthrough curves of Pb and Cd and develops a correlation formula for the breakthrough time of red mud–loess PRB medium. As the saturation of Pb increases from 0.05 to 0.85, the maximum volume adsorption capacity of Pb increases from 1.78 to 2.98 mg/L, while for Cd, it increases from 4.15 to 7.87 mg/L. Elevating the bed height first triggers chemical precipitation, hence improving Pb and Cd removal. Consequently, the longevity of red mud–loess PRB in acidic mine effluent containing Pb and Cd surpasses predicted theoretical outcomes. These observations reveal correlations between the breakthrough length for red mud–loess permeable reactive barriers and the bed height. Furthermore, the distribution of Pb speciation within the red mud–loess mixture (7 : 3) is primarily governed by the presence of iron–manganese oxide, while the composition of Cd speciation is chiefly influenced by the carbonate form and iron–manganese oxide. After treating acidic mine wastewater with Pb and Cd, the red mud–loess mixed material (7 : 3) undergoes surface changes, shifting from smooth to rough due to H+ corrosion. Pores between particles enlarge, yet heavy metal ions, adsorbates, and precipitates reoccupy and cover the surface, transforming the particle morphology from dense lamellar to clustered spherical. Our innovative approach to combining waste materials for environmental remediation presents a cost‐effective and impactful solution for heavy metal pollution.

Transient crystallisation of rare earth carbonates during the hydrothermal oxidation of siderite.

The researchers investigated the interaction between multi-component rare earth element-bearing aqueous solutions and siderite grains under hydrothermal conditions. Our study investigates the interaction between multi-component rare earth element (REE; La, Ce, Pr, Nd, Dy)-bearing aqueous solutions and siderite (FeCO3) grains under hydrothermal conditions (50-205 °C). The results revealed a solution-mediated mineral replacement reaction that occurs via a multi-step crystallisation pathway involving the formation of iron oxides (goethite, α-FeO(OH), and hematite, Fe2O3), metastable REE-bearing minerals (kozoite, REE(CO3)(OH), and bastnasite, REE(CO3)(OH,F)), and cerianite (CeO2). Siderite stability, dissolution, and subsequent mineral formation are temperature and pH-dependent. At low temperatures, REE carbonate formation is inhibited by a goethite coating, creating a partial equilibrium situation. Higher temperatures increase dissolution rates and enable kozoite and bastnasite formation. The redox behaviour of Fe and Ce combined with the temperature, and the availability of CO3 2- govern this crystallisation sequence. Continued oxidation promotes decarbonation processes by acidifying the aqueous solution, dissolving all carbonates, and resulting in hematite and cerianite crystallisation as thermodynamically stable phases. Understanding iron carbonate, oxide and REE interactions can inform new resource targets and improve recovery and separation techniques.