Up to 20% of rare earth elements (REEs) in ion adsorption deposits (IADs) are associated with iron oxide minerals, primarily goethite. Often termed “non-extractable”, goethite-hosted REEs are thought to be structurally incorporated into the mineral lattice. The large mismatch in size and charge density between REEs (ionic radius, r = 0.86–1.03 Å) and Fe3+ (r = 0.65 Å), however, makes direct substitution energetically unfavorable. To determine REE compatibility with and incorporation into goethite on the atomic level, we used X-ray pair distribution function analysis (PDF) and LIII-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. The compatibility of REEs with goethite and the precursor ferrihydrite (FH) is Lu ≥ Yb ≫ Dy > Nd for both phases. Nd and Dy primarily form secondary amorphous phases, with <30% Nd and Dy incorporated into goethite. In the FH precursor at pH 6.8, Yb and Lu assumed a local REE-OOH like structure with next nearest neighbor Fe. The Yb, Lu, and Nd-FH samples were also matured at ambient conditions for 100 days; despite the presence of only ∼5% goethite, Lu and Yb were 42% and 100% in goethite-like structural environments, respectively, whereas the PDF and EXAFS of Nd showed little evidence of any incorporation. Using ab initio molecular dynamics (AIMD) to model the EXAFS, we determined the presence of protonated Fe vacancies, edge-sharing with structural Lu and Yb, likely helped accommodate these REEs in the goethite structure. Incorporation into Fe oxyhydroxides thus potentially fractionates the REEs during weathering associated with formation of lateritic and ion adsorption deposits.

Chromium removal via coprecipitation with carbonates and iron oxyhydroxides minerals: The effect of organic complexing agents.

Glyphosate (PMG) is a globally used broad-spectrum herbicide and receives environmental concerns because of its moderate persistence and potential carcinogenicity. Traditional PMG treatment methods often suffer from the generation of a more toxic and persistent aminomethylphosphonic acid (AMPA) intermediate. Herein, we develop a green method with ferrihydrite (FH) and CaO2 (FH/CaO2) via regulating the coordination of PMG with FH and Ca2+, where the phosphonate group of PMG preferentially binds to FH and its carboxylate side complexes with Ca2+ released by CaO2, forming a FH-PMG-Ca ternary surface complex. This unique ternary complex can redistribute electrons within the PMG molecule for its C-P activation and C-N bond stabilization, favoring the selective C-P bond attack of superoxide radical produced by the Fenton reaction between CaO2-derived H2O2 and FH, thus generating environment-friendly glycine instead of AMPA. The FH/CaO2 process realizes over 99% PMG degradation in industrial wastewater within 1 h, with residual PMG < 0.1 ppm and AMPA < 40 ppb. More importantly, the CaO2 consumption was as low as 3.1 mg of CaO2/mg of PMG, one-fifth those of previously reported CaO2-based counterparts. This study provides an effective and environment-friendly PMG treatment strategy and highlights the importance of surface coordination modes on the degradation pathway of PMG.

Antimony (Sb) migration in soil and water systems is predominantly governed by its adsorption onto ferrihydrite (FH), a process strongly influenced by natural organic matter. This study investigates the adsorption behavior, stability, and mechanism of FH and FH-humic acid (FH-HA) complexes on Sb(V), along with the fate of adsorbed Sb(V) during FH aging. Batch adsorption experiments reveal that initial pH and concentration significantly influence Sb(V) sorption. Lower pH levels decrease adsorption, while higher concentrations enhance it. Sb(V) adsorption increases with prolonged contact time, with FH exhibiting a higher adsorption capacity than FH-HA complexes. Incorporating HA onto FH surfaces reduces reactive adsorption sites, decreasing Sb(V) adsorption. Adsorbed FH-HA complexes exhibit a higher specific surface area than co-precipitated FH-HA, demonstrating stronger Sb(V) adsorption capacity under various conditions. X-ray photoelectron spectroscopy (XPS) confirms that Sb(V) adsorption primarily occurs through ligand exchange, forming Fe-O-Sb complexes. HA inhibits the migration of Sb(V), thereby enhancing its retention within the FH and FH-HA complexes. During FH transformation, a portion of Sb(V) may replace Fe(III) within converted iron minerals. However, the combination of relatively high adsorption capacity and significantly lower desorption rates makes adsorbed FH-HA complexes promising candidates for sustained Sb adsorption over extended periods. These findings enhance our understanding of Sb(V) behavior and offer insights for effective remediation strategies in complex environmental systems.

Distinct photochemistry of adsorbed and coprecipitated dicarboxylates with ferrihydrite: Implications for iron reductive dissolution and carbon stabilization

Organic phosphates (OP) are important nutrient components for living cells in natural environments, where they readily interact with ubiquitous iron phases such as hydrous ferric oxide, ferrihydrite (FHY). FHY partakes in many key bio(geo)chemical reactions including iron-mediated carbon storage in soils, or iron-storage in living organisms. However, it is still unknown how OP affects the formation, structure and properties of FHY. Here, we document how β-glycerophosphate (GP), a model OP ligand, affects the structure and properties of GP-FHY nanoparticles synthesized by coprecipitation at variable nominal molar P/Fe ratios (0.01 to 0.5). All GP-FHY precipitates were characterized by a maximum solid P/Fe ratio of 0.22, irrespective of the nominal P/Fe ratio. With increasing nominal P/Fe ratio, the specific surface area of the GP-FHY precipitates decreased sharply from 290 to 3 m2 g-1, accompanied by the collapse of their pore structure. The Fe-P local bonding environment gradually transitioned from a bidentate binuclear geometry at low P/Fe ratios to monodentate mononuclear geometry at high P/Fe ratios. This transition was accompanied by a decrease in coordination number of edge-sharing Fe polyhedra, and the loss of the corner-sharing Fe polyhedra. We show that Fe(iii) polymerization is impeded by GP, and that the GP-FHY structure is highly dependent on the P/Fe ratio. We discuss the role that natural OP-bearing Fe(iii) nanophases have in biogeochemical reactions between Fe-P and C species in aquatic systems.

Amorphous iron oxyhydroxides nano precursors used for Reactive Yellow 84 removal from aqueous solutions

Migration of spent grain-modified colloidal ferrihydrite: Implications for the in situ stabilization of arsenic, lead, and cadmium in co-contaminated soil

Introduction: Nano crystals are collections of molecule that may be put together to generate crystalline forms of drugs that are covered in a thin layer of surfactant. Quantum dots offer a wide range of uses in biology imaging, bioengineering, and environmental research, but less so in biomedicine for drug delivery. Nano crystals are created as nano absences, which are tiny medication particles. For medications that are weakly soluble, nano crystal is a commercially feasible formulation. A flexible and all-purpose manufacturing technique for nano crystalline is wet milling. Several delivery methods have been devised using nano crystalline structures. The crystals hair remover uses micro innovation to cause hairs to gather and separate from the flesh when it is gently massaged into the skin. Refillable and rechargeable-free for years of use. Skin, arms, limbs, chest, head back are all safe places to apply Crystal Hair Extractor. Research significance: A nonmaterial is a chemical particle made up of atoms in a mono or poly-crystalline form and having at least one length more than 100 micrometers. It is based on classical dots, which are nano particles. Organic nano crystal ferri hydrites have been identified as the basic core of ferritin in biology and are significant elements of many ecosystems. They are produced on CWP substrates by detonation. Methodology: Alternative: Conduction band offset, capacitive density, band gap, and dynamic constant. Evaluation Preference: Si3N4, Al2O3, ZrO, HfO2, Ta2O5. Result: “from the result it is seen that ZrO and is got the first rank whereas is the Si3N4 got is having the lowest rank”. Conclusion: “The value of the dataset for nano crystals in MOORA shows that it results in ZrO and top ranking”.

Oxidative compensation mechanism of Fe-S synergetic inhibition of Cd activity in paddy field during flooding and drainage

Accurate detection and analysis of arsenic pollutants are an important means to enhance the ability to manage arsenic pollution. Infrared (IR) spectroscopy technology has the advantages of fast analysis speed, high resolution, and high sensitivity and can be monitored by real-time in situ analysis. This paper reviews the application of IR spectroscopy in the qualitative and quantitative analysis of inorganic and organic arsenic acid adsorbed by major minerals such as ferrihydrite (FH), hematite, goethite, and titanium dioxide. The IR spectroscopy technique cannot only identify different arsenic contaminants but also obtain the content and adsorption rate of arsenic contaminants in the solid phase. The reaction equilibrium constants and the degree of reaction conversion can be determined by constructing adsorption isotherms or combining them with modeling techniques. Theoretical calculations of IR spectra of mineral adsorbed arsenic pollutant systems based on density functional theory (DFT) and analysis and comparison of the measured and theoretically calculated characteristic peaks of IR spectra can reveal the microscopic mechanism and surface chemical morphology of the arsenic adsorption process. This paper systematically summarizes the qualitative and quantitative studies and theoretical calculations of IR spectroscopy in inorganic and organic arsenic pollutant adsorption systems, which provides new insights for accurate detection and analysis of arsenic pollutants and arsenic pollution control. PRACTITIONER POINTS: This paper reviews the application of infrared spectroscopy in the qualitative and quantitative analyses of inorganic and organic arsenic acid adsorbed by major minerals such as ferrihydrite, hematite, goethite, and titanium dioxide, which can help identify and evaluate the type and concentration of arsenic pollutants in water bodies. In this paper, theoretical calculations of infrared spectra of mineral adsorbed arsenic pollutant systems based on density functional theory reveal the adsorption mechanism of arsenic pollutants in water at the solid-liquid interface and help to develop targeted arsenic pollution control technologies. This paper provides a new and reliable analytical detection technique for the study of arsenic contaminants in water bodies.

Enhanced cadmium removal by biochar and iron oxides composite: Material interactions and pore structure

The objectives of this study were to evaluate the cadmium adsorption capacity of iron-organic associations (Fe-OM) formed by laccase-mediated modification and assess the effect of Fe-OM on the immobilization of cadmium in paddy soil. Leaf organic matter (OM) was extracted from Changshan grapefruit leaves, and then dissolved organic matter (Lac-OM) and precipitated organic matter (Lac-P) were obtained by laccase catalytic modification. Different Fe-OM associations were obtained by co-precipitation of Fe with OM, Lac-OM, and Lac-P, respectively, and the adsorption kinetics, adsorption edge, and isothermal adsorption experiments of Cd on Fe-OM were carried out. Based on the in situ generation of Fe-OM, passivation experiments on Cd-contaminated soils with a high geological background were carried out. All types of Fe-OM have a better Cd adsorption capacity than ferrihydrite (FH). The theoretical maximum adsorption capacity of the OM-FH, Lac-OM-FH, and Lac-P-FH were 2.2, 2.53, and 2.98 times higher than that of FH, respectively. The adsorption of Cd on Fe-OM is mainly chemisorption, and the -OH moieties on the Fe-OM surface form an inner-sphere complex with the Cd ions. Lac-OM-FH showed a higher Cd adsorption capacity than OM-FH, which is related to the formation of more oxygen-containing groups in the organic matter modified by laccase. The immobilization effect of Lac-OM-FH on active Cd in soil was also higher than that of OM-FH. The Lac-OM-FH formed by laccase-mediated modification has better Cd adsorption performance, which can effectively inactivate the activity of Cd in paddy soil.

Sorption of oxyanions, such as pentavalent vanadium (V(V)), by reactive, poorly crystallized clay minerals and Fe-(hydr)oxides surfaces significantly contributes to the nutrient and pollutant transport in soils. However, only a few studies yet exist, which evaluate and quantify the role of such common soil substituents on V sorption. In this contribution, the uptake of V(V) by allophane with molar Al/Si ratios of 1.5 (ALO-1) and 1.8 (ALO-2) and by montmorillonite-beidellite (MNT-BEI) clays was investigated using kinetic and equilibrium experiments. The effects of pH, V speciation, contact time and presence of 6-line ferrihydrite (FHY) were evaluated at 25 °C. The clayey substrates with(out) FHY were characterized using X-ray diffraction, X-ray fluorescence, high-resolution transmission electron microscopy with energy-dispersive X-ray spectroscopy and selected area electron diffraction and N2-Brunauer-Emmett-Teller physisorption methods. Fast (≥ 15 min) adsorption of V(V) was followed by pseudo-first-order reaction kinetics and progressed through instantaneous diffusion processes at the exterior surface. Subsequently, V(V) transportation and adsorption within the interior substrate, as inferred from Weber-Morris intra-particle diffusion model plots, was observed. The presence of FHY had a positive effect on V(V) adsorption ([V]T = 0.02 mmol/L), which followed in the order MNT-BEI-FHY and MNT-BEI (≥ 95% removal), ALO-1-FHY and ALO-2-FHY (≥ 90% removal), ALO-1 (≥ 70% removal) and ALO-2 (≥ 40% removal) in the pH range from ~6 to ~8. The results of this study demonstrate the high affinity of ferrihydrite as well as allophanic and smectitic clays for V(V) adsorption, suggesting that these components can limit the V mobility in soils over a wide pH range.

Insights into graphene oxide/ferrihydrite adsorption as pretreatment during ultrafiltration: Membrane fouling mitigation and disinfection by-product control

In permafrost peatlands, up to 20%of total organic carbon (OC)is bound to reactive iron (Fe) minerals in the active layer overlyingintact permafrost, potentially protecting OC from microbial degradationand transformation into greenhouse gases (GHG) such as CO2 and CH4. During the summer, shifts in runoff and soilmoisture influence redox conditions and therefore the balance of Feoxidation and reduction. Whether reactive iron minerals could actas a stable sink for carbon or whether they are continuously dissolvedand reprecipitated during redox shifts remains unknown. We deployedbags of synthetic ferrihydrite (FH)-coated sand in the active layeralong a permafrost thaw gradient in Stordalen mire (Abisko, Sweden)over the summer (June to September) to capture changes in redox conditionsand quantify the formation and dissolution of reactive Fe(III) (oxyhydr)oxides.We found that the bags accumulated Fe(III) under constant oxic conditionsin areas overlying intact permafrost over the full summer season.In contrast, in fully thawed areas, conditions were continuously anoxic,and by late summer, 50.4 ± 12.8% of the original Fe(III) (oxyhydr)oxideswere lost via dissolution. Periodic redox shifts (from 0 to +300 mV)were observed over the summer season in the partially thawed areas.This resulted in the dissolution and loss of 47.2 ± 20.3% ofinitial Fe(III) (oxyhydr)oxides when conditions are wetter and morereduced, and new formation of Fe(III) minerals (33.7 ± 8.6% gainin comparison to initial Fe) in the late summer under more dry andoxic conditions, which also led to the sequestration of Fe-bound organiccarbon. Our data suggest that there is seasonal turnover of iron mineralsin partially thawed permafrost peatlands, but that a fraction of theFe pool remains stable even under continuously anoxic conditions.

Transport of silver nanoparticles coated with polyvinylpyrrolidone of various molecular sizes in porous media: Interplay of polymeric coatings and chemically heterogeneous surfaces

Ferrihydrite reduces the bioavailability of copper and cadmium and phosphorus release risk in hydroxyapatite amended soil

Combined application of ferrihydrite and hydroxyapatite to immobilize soil copper, cadmium, and phosphate under flooding-drainage alternations

Comparison of the effects of large-grained and nano-sized biochar, ferrihydrite, and complexes thereof on Cd and As in a contaminated soil–plant system