Ferrihydrite Research Articles

Antimony(V) Adsorption and Partitioning by Humic Acid-Modified Ferrihydrite: Insights into Environmental Remediation and Transformation Processes.

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

Although ligand-promoted photodissolution of ferrihydrite (FH) has long been known for low molecular weight organic acids (LMWOAs), such as oxalate (Oxa) and malonate (Mal), photochemistry of coprecipitated FH with Oxa and Mal remains unknown, despite the importance of these mineral-organic associations in carbon retention has been acknowledged recently. In this study, ferrihydrite-LMWOAs associations (FLAs) were synthesized under circumneutral conditions. Photo-dissolution kinetics of FLAs were compared with those of adsorbed LMWOAs on FH surface and dissolved Fe-LMWOAs complexes through monitoring Fe(II) formation and organic carbon decay. For aqueous Fe(III)-LMWOAs complexes, Fe(II) yield was controlled by the initial concentration of LMWOAs and nature of photochemically generated carbon-centered radicals. Inner-sphere mononuclear bidentate (MB) configuration dominated while LMWOAs were adsorbed on the FH surface. MB complex of FH-Oxa was more photoreactive, leading to the rapid depletion of Oxa. Oxa can be readsorbed but in the form of binuclear bidentate and outer-sphere complexation, with much lower photoreactivity. While LMWOAs was coprecipitated with FH, the combination mode of LMWOAs with FH includes surface adsorption with a mononuclear bidentate structure and internal physical inclusion. Higher content of LMWOAs in the FLAs promoted the photo-production of Fe(II) as compared to pure FH, while it was not the case for FLAs containing moderate amounts of LMWOAs. The distinct photochemistry of adsorbed and coprecipitated Fe-LMWOAs complexes is attributed to ligand availability and configuration patterns of LMWOAs on the surface or entrapped in the interior structure. The present findings have significant implications for understanding the photochemical redox cycling of iron across the interface of Fe-organic mineral associates.

Impact of organic phosphates on the structure and composition of short-range ordered iron nanophases.

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

In this research, we investigated the potential use of amorphous iron oxyhydroxides, ferrihydrite (FHY), for the removal of persistent pollutants from aqueous solutions. Ethylenediaminetetraacetic acid (EDTA) and ethylenediamine-N, N′-disuccinic acid (EDDS) were used as complexing agents during synthesis aiming to enhance the FHY properties. Synthesized materials were characterized by X-ray diffraction, SEM and TEM Microscopy, N2 sorption/desorption, and FT-IR Spectroscopy for their mineralogy, crystallinity, morphology and size, surface properties, and the organic content in their structure. The addition of chelating agents led to differences in nanoparticles morphology, amorphic degree, and surface properties. Reactive Yellow 84 dye was chosen as a representative refractory pollutant and laboratory-scale adsorption studies were conducted at varying dye concentrations. Ca. 100 % RY 84 dye removal efficiency was achieved within one hour at dye concentrations of 5–10 mg/L for an adsorbent dosage of 1 mg/L FHY. Adsorption kinetics and isothermal studies were considered, the uptake capacity was calculated for each nanomaterial and empiric mechanistic information was derived. The results showed that ferrihydrite exhibits the best performance, with a maximum uptake capacity of 40.73 mg Reactive Yellow 84 dye per gram adsorbent followed by FHY_EDTA and FHY_EDDS (up to 35.86 mg/g). Coupling the adsorption with photodegradation processes led to a significant increase in removal efficiencies of persistent RY 84 from polluted aqueous solution, in good timing, suggesting a feasible alternative at sites where dye concentration in effluents is elevated.

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

The increase of metal mining, processing, and smelting activities has precipitated a substantial escalation in the contamination of soil by heavy metals. Ferrihydrite (FH) has been commonly used as an amendment for the immobilization of heavy metals in contaminated soil. However, FH suffers from drawbacks such as agglomeration and nonmigratory characteristics, which limit its practical application in soil remediation. Herein, a novel spent grain-modified ferrihydrite (FH-SG) colloidal system was developed, and the FH-SG transport mechanisms in the soil medium were fully studied, focusing in particular on the simultaneous in situ stabilization of arsenic (As), lead (Pb), and cadmium (Cd) in co-contaminated soil. The results showed that the stabilization rates of the FH-SG material reached 94.66%, 96.12%, and 95.52% for water-soluble As, Pb, and Cd, respectively, and 72.22%, 49.39%, and 25.30% for bioavailable As, Pb, and Cd, respectively. The FH-SG material demonstrates notable migration properties in porous media. Theoretical calculation results of a single collector show that the migration deposition of FH-SG material in media is primarily governed by its inherent diffusion characteristics with minimal influence by gravitational forces and media interception. It is noteworthy that the maximum migration distance in quartz sand and soil media with different particle sizes can reach 2.07–2.92 m and 0.78–1.08 m, respectively. Altogether, our findings clearly demonstrate that FH-SG exhibits better stabilization and migration than those of FH alone and most proposed FH colloidal systems. The FH-SG colloidal system holds significant promise for the remediation of various kinds of complex polluted soil.

Biological Applications of Colloidal Nano Crystals Using the MOORA Method

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

It is known that the transformation of Fe and S forms in soil affects the migration and activity of Cd, but the coordinated regulation of Cd activity by Fe and S under different redox conditions is still unclear. Here, Diffusive gradients in thin films (DGT), an in-situ monitoring technique, is used to explore the difference of the regulation of Cd activity in paddy fields with ferrihydrite (FH) and ferrihydrite coprecipitated by sulfate (FH-S) under the flooding and drainage conditions. The addition of FH-S and FH significantly reduced the activity of Cd (Dissolved, Exchanged, and CDGT-Cd). Compared with pure FH, the adsorption extent of Cd in FH was enhanced by increasing concentrations of SO42− (i.e., S/Fe ratio), which is attributed to the decrease in the crystallinity of FH by sulfate. During soil flooding, the addition of FH-S promoted the production of metal sulfide (CdS and FeS/FeS2). The activity of Cd increased after drainage, while the FH-S treatment groups delayed the release of Cd. After 30 days of drainage, the concentration of Cd in FH-S treatment groups decreased by 28.9–44.1 % compared with the control group. The fresh FeS/FeS2 is not the main adsorbent for fixing Cd, and due to the existence of oxidation compensation mechanism, the preferential oxidation of FeS/FeS2 delays the release of Cd in the drainage stage. Our study shed new light on the mechanism of Fe-S synergistic regulation of Cd and remediation of Cd-contaminated soils.

Application of infrared spectroscopy and its theoretical simulation to arsenic adsorption processes.

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 combination of biochar (BC) and iron minerals improves their pollutant adsorption capacity. However, little is known about the reactivity of BC-iron mineral composites regarding their interaction and change in the pore structure. In this study, the mechanism of cadmium (Cd) adsorption by BC-iron oxide composites, such as BC combined with ferrihydrite (FH) or goethite (GT), was explored. The synergistic effect of the BC-FH composite significantly improved its Cd adsorption capacity. The adsorption efficiencies of BC-FH and BC-GT increased by 15.0% and 10.8%, respectively, compared with that of uncombined BC, FH, and GT. The strong Cd adsorption by BC-FH was attributed to stable interactions and stereoscopic pore filling between BC and FH. The scanning electron microscopy results showed that FH particles entered the BC pores, whereas GT particles were loaded onto the BC surface. FTIR spectroscopy showed that GT covered a larger area of the BC surface than FH. After loading FH and GT, BC porosities decreased by 9.3% and 4.1%, respectively. Quantum chemical calculations and independent gradient mode analysis showed that van der Waals interactions, H-bonds, and covalent-like interactions maintained stability between iron minerals and BC. Additionally, humic acid increased the agglomeration of iron oxides and formed larger particles, causing additional aggregates to load onto the BC surface instead of entering the BC pores. Our results provide theoretical support to reveal the interfacial behavior of BC-iron mineral composites in soil and provide a reference for field applications of these materials for pollution control and environmental remediation.

Enhanced Adsorption of Cd on Iron–Organic Associations Formed by Laccase-Mediated Modification: Implications for the Immobilization of Cadmium in Paddy Soil

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.

Effect of kinetics, pH, aqueous speciation and presence of ferrihydrite on vanadium (V) uptake by allophanic and smectitic clays

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 this study, a novel adsorbent of graphene oxide (GO) incorporated ferrihydrite (FH) was fabricated and integrated with ultrafiltration (UF) to remove natural organic matter (NOM), the crucial cause of membrane fouling and major precursor of disinfection by-products (DBPs). Compared with FH and powdered activated carbon (PAC), GO/FH exhibited superior removal for high molecular weight (HMW) humic- and fulvic-like substances and low molecular weight (LMW) protein. The cake layer formed by GO/FH alleviated the deposition of NOM on membrane surface or inside membrane pores. Therefore, GO/FH reduced 89% and 95% total fouling resistance and irreversible membrane resistance, respectively, together with the lowest increment of transmembrane pressure. Pearson correlation analysis indicated that DOC, rather than specific ultraviolet absorbance (SUVA) and UV254, was significantly correlated to the formation of trihalomethanes (THMs) and haloacetic acids (HAAs) when SUVA was below 4 L/mg-C.m. Whilst the HMW NOM (1–20 kDa) was highly related to dibromochloromethane (DBCM) (r = 0.98–1), the LMW fraction (< 1 kDa) was correlated with dibromochloromethane (TCAA) and dichloroacetic acid (DCAA) (r = 0.88–0.98). Inspiringly, GO/FH-UF reduced 90% of carbonaceous DBPs, the concentrations of which well met the WHO Guidelines. In summary, GO/FH-UF substantially alleviated membrane fouling and dramatically reduced DBP formation potential.

Seasonal Fluctuations in Iron Cycling in Thawing Permafrost Peatlands.

In permafrost peatlands, up to 20% of total organic carbon (OC) is bound to reactive iron (Fe) minerals in the active layer overlying intact permafrost, potentially protecting OC from microbial degradation and transformation into greenhouse gases (GHG) such as CO2 and CH4. During the summer, shifts in runoff and soil moisture influence redox conditions and therefore the balance of Fe oxidation and reduction. Whether reactive iron minerals could act as a stable sink for carbon or whether they are continuously dissolved and reprecipitated during redox shifts remains unknown. We deployed bags of synthetic ferrihydrite (FH)-coated sand in the active layer along a permafrost thaw gradient in Stordalen mire (Abisko, Sweden) over the summer (June to September) to capture changes in redox conditions and quantify the formation and dissolution of reactive Fe(III) (oxyhydr)oxides. We found that the bags accumulated Fe(III) under constant oxic conditions in 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)oxides were 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% of initial Fe(III) (oxyhydr)oxides when conditions are wetter and more reduced, and new formation of Fe(III) minerals (33.7 ± 8.6% gain in comparison to initial Fe) in the late summer under more dry and oxic conditions, which also led to the sequestration of Fe-bound organic carbon. Our data suggest that there is seasonal turnover of iron minerals in partially thawed permafrost peatlands, but that a fraction of the Fe 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

Silver nanoparticles (AgNPs) are usually capped with stabilizing agents to protect their activities and improve stability. Polyvinylpyrrolidone (PVP) is one of the most used capping agents of AgNPs, and may affect the transport of AgNPs in porous media. The transport and retention of AgNPs capped with PVPs of different molecular weights (PVP10-AgNP, PVP40-AgNP and PVP360-AgNP) in uncoated, and humic acid (HA)-, kaolinite (KL)- and ferrihydrite (FH)-coated sand porous media were investigated. Among the three AgNPs, PVP360-AgNP exhibited the highest mobility and eluted from all types of porous media. This is because PVPs of higher molecular weight provided stronger steric effect and electrostatic repulsive forces among PVP-AgNPs, inducing stronger blocking and shadow effects. The transport of the PVP-AgNPs increased in the HA-Sand columns, while decreased in the KL- and FH-Sand columns, especially for PVP10-AgNP and PVP40-AgNP. The simulation results using one-site kinetic model indicated that HA-Sand reduced the maximum retention capacity (Smax), while KL- and FH-Sand increased the Smax as well as the first-order attachment rate coefficients (katt), particularly at high ionic strength. The results shed light on the interplay of the capping agents of AgNPs and the surface heterogeneity on the transport of AgNPs in porous media.

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

Hydroxyapatite (HAP) can effectively decrease bioavailability of trace metals in soils, but the phosphorus (P) release risk was not fully known. In this study, the impacts of ferrihydrite (FH) on passivation of copper (Cu) and cadmium (Cd) and P release risk in soil amended by HAP were investigated under flooding conditions. Results showed that the combinations of HAP and FH increased soil pore water pH by 0.74–2.24 units and reduced phosphate by 71.1–99.5% than single HAP. Soil pore water Cu2+ and Cd2+ in HAP plus 5% FH treated soils were decreased by 96.8–98.6% and 86.6–98.6% than those of single HAP. The combinations of HAP and FH significantly decreased CaCl2 extractable Cu and Cd by 55.9–99% and 13–72.2%, respectively. Moreover, the combinations of HAP and FH significantly decreased exchangeable Cu 47.1–91.5%, but only FH5 decreased exchangeable Cd by 69.4% than the single HAP. Amorphous iron oxide in FH treated soils was 4.06–20 times higher than control, but some of them were transformed into crystalline iron oxide after 42-d flooding incubation. The FH significantly decreased soil labile P by 42.8–78.8% in the presence of HAP and increased stable P by 23.1–33.5% than the single HAP. This study suggested that the addition of FH can not only promote the passivation of HAP on Cu and Cd in the soil, but also reduce the P release risk. Overall, this study highlighted the potential value of the combination of HAP and FH in the passivation of Cu and Cd contaminated soils.

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

Hydroxyapatite (HAP) can effectively immobilize soil heavy metals, but excess phosphate would be released to aquatic ecosystem, resulting in eutrophication. This study investigated the effects of ferrihydrite (FH) on the HAP immobilization of copper (Cu) and cadmium (Cd) and their reduction of phosphorus release under flooding-drainage alternation conditions. Results showed that the incorporation of HAP and FH significantly increased soil solution pH and decreased Cu2+ and Cd2+ concentrations. Applications of FH, HAP, and FH-HAP (FH and HAP combination) can all enhance soil pH and reduce CaCl2-extractable and exchangeable Cu and Cd, but HAP addition increased soluble phosphate by 6.60–7.77 times compared to control. However, FH-HAP application can significantly reduce phosphate release by 92.7–99.7% compared to HAP application. FH-HAP was the most effective to reduce exchangeable Cu and Cd by 49.8–93.4% and 50.9–88.8% and decreased labile and moderately labile phosphorus by 34.0–74.4% and 13.5–18.6%, respectively, while increased stable phosphorus by 22–45.1% than single HAP. All FH treatments significantly increased amorphous iron oxides by the factors of 4.66–20.8, but only 3% and 5% of FH applications slightly enhanced crystal iron oxides by the factors of 0.81–1.27. The major implication is that the combination of FH and HAP can not only immobilize of Cu and Cd, but also reduce the risk of phosphate release by HAP addition.

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

Cd and As are difficult to co-remediate in co-contaminated soils. In this study, remediation materials comprising large-grained and nano-sized biochar (BC), ferrihydrite (FH), and complexes thereof were added to Cd- and As-contaminated soil. The uptake of Cd and As by pak choi (Brassica chinensis L.) was then evaluated using a pot experiment and the Cd and As concentrations of the soil pore water and leaching water were measured. The Cd and As concentrations of the pore and leaching water were slightly increased with the addition of BC, and decreased with addition of FH and the biochar–ferrihydrite complex (BC-FH). However, nano-sized BC (BCN), FH (FHN), and BC-FH (BC–FHN) had little influence on the decreases in Cd and As of the two monitored water types. Large-grained remediation materials, rather than nanomaterials, decreased the Cd and As concentrations of the two monitored water types. Nonetheless, nanomaterial treatments more effectively decreased the Cd and As concentrations in plants by an average of >10% relative to the large-grained treatments. The DLVO theory analysis suggested that BCN, FHN, and BC-FHN, immobilized in the topsoil, adsorbed heavy metals in the rhizosphere soil. The remainder of the nano-sized materials was dispersed in the rhizosphere soil pores, shielding the uptake of Cd and As by the roots. Although the doses of nanomaterials used in this study were less than one-fortieth of those of the large-grained materials, changes in the plant rhizosphere microenvironment caused by the nanomaterials decreased the risk of toxicity transfer from the soil to the plants.

Morphological and compositional modification of β-Ni(OH)2 nanoplates by ferrihydrite for enhanced oxygen evolution reaction

Ni(OH)2 has been long studied as an effective oxygen evolution electrocatalyst. Nevertheless, its catalytic activity can still be further enhanced by microstructural modification and Fe-doping. In this study, with the assistance of adsorbent ferrihydrite (FH), we obtain Fe-doped β-Ni(OH)2 nanoplates with Fe2O3 nanoparticles decorated on the surface via a facile hydrothermal process. The Fe-doping, decorated Fe2O3 nanoparticles, and special microstructure endow β-Ni(OH)2 nanoplates with an improved oxygen evolution activity in alkaline solutions. For the sample with optimal FH amount, the overpotential to motivate a current density of 10 mA cm−2 is 280 mV, with a low Tafel slope of ~64.17 mV dec−1. During the 10 h i-t test at 1.50 V vs. RHE, the current density has an attenuation of only 23.7%. The study opens a facile avenue to modify Ni(OH)2-based OER catalyst from perspectives of both microstructures and compositions.

Synthesis and Optimization of Multiwalled Carbon Nanotubes–Ferrihydrite Hybrid Composite

Carbon nanotubes (CNT) are a family of carbon nanomaterials that have uses in many technological and medical applications due to their unique properties. However, compared to other nanomaterials, CNT have a significantly lower specific surface areas (SSA), which is a critical limitation for applications. To overcome this limitation, here, we report a new protocol to synthesize a hybrid material composed of varying ratios of multiwalled carbon nanotubes (MWCNT) and ferrihydrite (FHY). Furthermore, through a series of physical and electrochemical characterization tests, we determined that 36% FHY and 64% MWCNT is the optimum ratio for a composite that maximizes both SSA and specific capacitance. The calculated SSA of the composite was 190 m2·g−1, 2.9 times higher than that of MWCNT alone. Moreover, the composite retained valuable electrochemical properties of CNT with an estimated specific capacitance of 100 F·g−1. This composite is a promising multifunctional nanomaterial for environmental and technological applications requiring electrochemical reactivity and high specific areas such as environmental biosensors, and capacitive deionization for wastewater remediation, and water softening.

Response of wheat cells to ferrihydrite nanoparticles under model system in vitro

High biological activity of nanoparticles (NPs) makes them promising for using in fertilizers composition. Design of such products is impossible without detection of active substance influence mechanisms on growth and development of plant as well as without detection of critical points, when influence of the investigated agent is at its maximum. Biogenic ferrihydrites (FH) are promising regulators of plant cell antioxidant system activity, also under edaphic stresses. Callus cultures are well known as convenient model system for screening of tissue and cell response to different environmental exposure. Investigation results of FH NP`s, which were produced by authors, influence on growth and development of callus culture of soft spring wheat mature wheat embryos of are presented in present article. The absence of competitive in relation to 2,4-D influence of involved levels of FH NPs (1 and 10 mg/l) on dedifferentiation process of embryo tissues was indicated. The presence of investigated agent induced the decrease of culture growth rate. However, postponed positive effect manifested in reduction of ageing rate after passing to fresh medium, the bigger, the higher had been FH NP`s level at the previous cultivation stage. The present effect may be of critical importance under field conditions under the influence of unfavorable edaphic and climatic factors, which adds further credence the potential of presented NPs applicability in agriculture.