Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 97.480
Filtrar
1.
Sci Total Environ ; 857(Pt 2): 159364, 2023 Jan 20.
Artículo en Inglés | MEDLINE | ID: mdl-36228794

RESUMEN

The coupling of microscale zero-valent iron with autotrophic hydrogen bacteria (mZVI-AHB) are often believed to show greater potential than the single abiotic or biotic systems in remediating chlorinated aliphatic hydrocarbon-contaminated groundwater. However, our understanding of the remediation performance of this system under real field conditions, especially by incorporating the concept of sustainable remediation, remains limited. In this study, the performances of the mZVI, H2-AHB, and mZVI-AHB systems in dechlorinating groundwater containing complex electron acceptors were compared by evaluating their removal efficiency (RE), reaction products, and electron efficiency (EE), using trichloroethylene (TCE) as the target contaminant and NO3- and SO42- as the coexisting natural electron acceptors. Ultimately, which of these systems had TCE removal superiority was dependent on the coexisting electron acceptor. mZVI-AHB and mZVI resulted in more complete dechlorination, whereas H2-AHB exhibited higher N2 selectivity in reducing NO3-. Regardless of the coexisting electron acceptor, the mZVI-alone system showed the highest EE. Finally, the sustainability concerns and applicability of the three systems were evaluated on the basis of their TCE RE, complete dechlorination ratio, N2 selectivity, EE, and cost, which were integrated into a comparison of overall benefits. Our findings provide comprehensive and insightful information on the factors that determine remediation scheme selection in real practice.


Asunto(s)
Agua Subterránea , Tricloroetileno , Contaminantes Químicos del Agua , Hidrógeno , Hierro , Tricloroetileno/análisis , Bacterias , Contaminantes Químicos del Agua/análisis
2.
J Environ Manage ; 325(Pt B): 116550, 2023 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-36347188

RESUMEN

Owing to the tremendous increase of chemicals for agricultural practices, the quality of water has degraded significantly and requires inevitable attention. With this in mind, present work aims at treating Paraquat (PQ) contaminated water using Fe containing industrial waste as a catalyst via photo-Fenton treatment. Utilizing the industrially generated Fe rich waste by-products i.e., Fly ash (FA), Foundry sand (FS), Red mud (RM), and Blast sand (BS) as catalysts marks the novelty of the work since this idea of using waste for treating waste serves the dual purpose of environment remediation:first by treating wastewater and second by resolving the issue of solid waste disposal. In the present study, 25 mg/L PQ was subjected to both UV and solar radiations in the presence of FeSO4, FA, FS, RM, and BS as catalysts. The presence of Fe in the catalysts was verified using analytical techniques namely FTIR, FESEM-EDX, and their XRD was also analyzed. The system was further optimized for various parameters and results indicated maximum PQ degradation under UV radiations was attained in the order FeSO4 (73%) > BS (65%) > FS (46%) > RM (37%) > FA (14%) within 60 min which significantly increased with introduction of solar radiations to 83% for Fe salt and 76% for BS justifying the potential of using waste for treating waste. Further, to enhance the real-life utilization of industrial waste, Fe2O3/BS heterojunction (Fe-BS) was synthesized which along with leading to 88% degradation of PQ, also showed 82% COD removal indicating that the catalyst not only degrades the pollutant but also converts it into a lower toxic form. Further, the intermediates formed during the process were analyzed using LCMS.


Asunto(s)
Residuos Industriales , Contaminantes Químicos del Agua , Hierro , Eliminación de Residuos Líquidos/métodos , Paraquat , Arena , Peróxido de Hidrógeno , Aguas Residuales , Agua , Oxidación-Reducción
3.
J Colloid Interface Sci ; 630(Pt B): 866-877, 2023 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-36356452

RESUMEN

The photo-Fenton performance of Fe-based metal organic frameworks (Fe-MOFs) largely depends on the amount and the local electron density of metal coordinately unsaturated sites (M CUSs). However, a majority of Fe active sites are fully bound by organic ligands leading to decreased Fe CUSs. Additionally, the symmetrical electronic distribution of iron-oxo (Fe-O) clusters and the fast electron-hole recombination are unbeneficial for the directional electron transfer and the following electron accumulation on Fe CUSs. Herein, the structure of Fe-O clusters onto the framework of MIL-88B was controllably regulated via change of Ce doping amount, among which Fe0.8Ce0.2-MIL-88B exhibited highest removal efficiency of tetracycline (TC). That was mainly ascribed to the following two points: for one, the induced ligand missing defects ameliorated the pore structures and generated more M CUSs; for another, the lower electronegativity of Ce than Fe and the role of ligand missing defects as electron trap state collectively increased the local electron density at Fe CUSs. As a result, the increased M CUSs provided more active sites for H2O2 coordination and the highly concentrated electrons density at Fe CUSs afforded the substantial electron donation towards robust H2O2 dissociation into ∙OH. Furthermore, the increased mesoporous size favored highly-efficient utilization of ∙OH. This work provides a facile strategy to improve photo-Fenton performance of Fe-MOFs.


Asunto(s)
Cerio , Estructuras Metalorgánicas , Estructuras Metalorgánicas/química , Hierro/química , Electrones , Peróxido de Hidrógeno/química , Ácidos de Lewis , Ligandos
4.
Biochim Biophys Acta Proteins Proteom ; 1871(1): 140856, 2023 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-36252939

RESUMEN

Serum transferrin (sTf) is a bi-lobal protein. Each lobe of sTf binds one Fe3+ ion in the presence of a synergistic anion. Physiologically, carbonate is the main synergistic anion but other anions such as oxalate, malonate, glycolate, maleate, glycine, etc. can substitute for carbonate in vitro. The present work provides the possible pathways by which the substitution of carbonate with oxalate affects the structural, kinetic, thermodynamic, and functional properties of blood plasma sTf. Analysis of equilibrium experiments measuring iron release and structural unfolding of carbonate and oxalate bound diferric-sTf (Fe2sTf) as a function of pH, urea concentration, and temperature reveal that the structural and iron-centers stability of Fe2sTf increase by substitution of carbonate with oxalate. Analysis of isothermal titration calorimetry (ITC) scans showed that the affinity of Fe3+ with apo-sTf is enhanced by substituting carbonate with oxalate. Analysis of kinetic and thermodynamic parameters measured for the iron release from the carbonate and oxalate bound monoferric-N-lobe of sTf (FeNsTf) and Fe2sTf at pH 7.4 and pH 5.6 reveals that the substitution of carbonate with oxalate inhibits/retards the iron release via increasing the enthalpic barriers.


Asunto(s)
Carbonatos , Hierro , Aniones/química , Carbonatos/metabolismo , Hierro/química , Cinética , Oxalatos
5.
Biochim Biophys Acta Proteins Proteom ; 1871(1): 140855, 2023 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-36182071

RESUMEN

Bacteria depend on the ferrous iron transport (Feo) system for the uptake of ferrous iron (Fe2+). The Feo system is crucial for colonization and virulence of pathogens. In γ-proteobacteria, the system consists of FeoA, FeoB, and FeoC. The function of FeoA remains unknown. FeoB likely forms the channel, whose regulation has been suggested to involve its GTPase domain (part of its NFeoB domain). FeoC from Klebsiella pneumonia was found to contain a [4Fe4S] cofactor, whose presence was speculated to enhance the GTPase activity of FeoB (Hsueh, K.-L., et al., J. Bacteriol. 2013 195(20): 4726-34). We present results here that support and extend that hypothesis. We monitored the GTPase activity of FeoB by NMR spectroscopy and found that the presence of 7% FeoC-[4Fe-4S]3+ (the highest level of cofactor achieved in vitro) increased the GTPase rate of NFeoB by 3.6-fold over NFeoB. The effect depends on the oxidation state of the cluster; with reduction of the cluster to [4Fe-4S]2+ the GTPase greatly decreased the GTPase rate. From the effects of point mutations in FeoC on GTPase rates, we conclude that Lys62 and Lys68 on FeoC each contribute to increased GTPase activity on NFeoB. Mutation of Thr37 of NFeoB to Ser nearly abolished the GTPase activity. The GTPase activity of the isolated K. pneumoniae NFeoB-FeoC complex (NFeoBC) was found to be higher in KCl than in NaCl solution. We solved the X-ray structure of the NFeoBC crystallized from KCl and compared it with a prior X-ray structure crystalized from NaCl. We propose a hypothesis, consistent with these results, to explain the factors that influence the GTPase activity. Bacteria may use the oxygen-sensitive cluster as a sensor to up-regulate the gate closing speed.


Asunto(s)
Hierro , Klebsiella pneumoniae , Klebsiella pneumoniae/genética , Cloruro de Sodio , Azufre , GTP Fosfohidrolasas/genética
6.
Sci Total Environ ; 855: 158710, 2023 Jan 10.
Artículo en Inglés | MEDLINE | ID: mdl-36099954

RESUMEN

Iron (Fe) oxides are widely recognized to prevent the degradation of organic matter (OM) in environments, thereby promoting the persistence of organic carbon (OC) in soils. Thus, discerning the association mechanisms of Fe oxides and OC interactions is key to effectively influencing the dynamics and extent of organic C cycling in soils. Previous studies have focused on i) quantifying Fe oxide-bound organic carbon (Fe-OC) in individual environments, ii) investigating the distribution and adsorption capacity of Fe-OC, and iii) assessing the redox cycling and transformation of Fe-OC. Furthermore, the widespread application of high-tech instrumentation and methods has greatly contributed to a better understanding of the mechanism of organic mineral assemblages in the past few decades. However, few literature reviews have comprehensively summarized Fe-OC distributions, associations, and characteristics in soil-plant systems. Here, studies investigating the Fe-OC contents among different environments are reviewed. In addition, the mechanisms and processes related to OM transformation dynamics occurring at mineral-organic interfaces are also described. Recent studies have highlighted that diverse interactions occur between Fe oxides and OC, with organic compounds adhering to Fe oxides due to their huge specific surfaces area and active reaction sites. Moreover, we also review methods for understanding Fe-OC interactions at micro-interfaces. Lastly, developmental prospects for understanding coupled Fe-OC geochemical processes in soil environments at molecular- and nano-scales are outlined. The summary suggests that combined advanced techniques and methods should be used in future research to explore micro-interfaces and in situ descriptions of organic mineral assemblages. This review also suggests that future studies need to consider the functional and spatial complexity that is typical of soil/sediment environments where Fe-OC interactions occur.


Asunto(s)
Óxidos , Suelo , Suelo/química , Carbono , Minerales/química , Hierro , Compuestos Orgánicos/química
7.
Sci Total Environ ; 855: 158752, 2023 Jan 10.
Artículo en Inglés | MEDLINE | ID: mdl-36108861

RESUMEN

Highly dispersed iron nanoclusters on carbon (FeNC@C) hold great promise for wastewater purification in Fenton-like reactions. The microenvironment engineering of central Fe atom is promising to boost the activation capacity of FeNC@C, which is however remains a challenge. This study developed a self-sacrificed templating strategy to S, N-codoped carbon supported Fe nanoclusters (FeNC@SNC) activator and find the key role of sulfur heteroatoms in regulating the electron structure of Fe sites and final activation property. Investigations revealed that the FeNC@SNC composite exhibited unusual bifunctional activity in both peroxymonosulfate (PMS)- and periodate (PI)-based Fenton-like reactions. We also offered insights into the differences between the degradation of organics by the FeNC@SNC/PMS and FeNC@SNC/PI systems. Specifically, under identical conditions, the FeNC@SNC/PMS system delivered a higher oxidation capability and stronger resistance to nontarget matrix constituents, but showed more severe Fe leaching than the FeNC@SNC/PI system. Furthermore, while mediated electron-transfer process was identified as the major route for pollutant decomposition in both systems, the high-valent Fe-oxo species [Fe (IV)] was the auxiliary reactive species found only in the FeNC@SNC/PMS system. Based on these findings, our results provide profound insights into the design of active and durable Fe-based activators toward highly efficient Fenton-like reactions.


Asunto(s)
Carbono , Hierro , Hierro/química , Carbono/química , Nitrógeno , Azufre
8.
Sci Total Environ ; 855: 158715, 2023 Jan 10.
Artículo en Inglés | MEDLINE | ID: mdl-36113792

RESUMEN

Many nanomaterials containing different valences of iron have been designed for applications in biomedicine, energy, catalyzers, nanoenzymes, and so on. However, the toxic effects of the valence state of iron in iron-based nanomaterials are still unclear. Here, three different-valence iron-based nanomaterials (nFe@Fe3O4, nFe3O4 and nFe2O3) were synthesized and exposed to zebrafish embryos and mammalian cardiomyocytes. All of them induced ferroptosis along with an increase in valence through iron overload and the Fenton reaction. Specifically, we exposed Tg (cmlc2:EGFP) zebrafish to the three iron-based nanomaterials and found that nFe@Fe3O4 treatments led to enlarged ventricles, while nFe3O4 and nFe2O3 increased atrial size, which was consistent with the results from hematoxylin-eosin staining and in situ hybridization. Moreover, we used ferroptosis inhibitors (ferrostatin-1 or deferoxamine) to treat zebrafish along with nanoparticles exposure and found that the cardiac developmental defects caused by nFe3O4 and nFe2O3, but not nFe@Fe3O4, could be completely rescued by ferroptosis inhibitors. We further found that nFe@Fe3O4, rather than nFe3O4 and nFe2O3, reduced the dissolved oxygen in the medium, which resulted in hypoxia and acceleration of heart tube formation and ventricular enlargement, and both were fully rescued by oxygen donors combined with ferroptosis inhibitors. Consistently, these findings were also observed in mammalian cardiomyocytes. In summary, our study demonstrates that the valence state of iron-based nanomaterials determines the ferroptosis potential. Our study also clarifies that high-valence iron-based nanomaterials induce an enlarged atrium via ferroptosis, while low-valence ones increase the ventricular size through both hypoxia and ferroptosis, which is helpful to understand the potential adverse effects of different valences of iron-based nanomaterials on environmental health and assure the responsible and sustainable development of nanotechnology.


Asunto(s)
Ferroptosis , Nanoestructuras , Animales , Hierro/toxicidad , Pez Cebra , Nanoestructuras/toxicidad , Hipoxia , Oxígeno , Mamíferos
9.
Sci Total Environ ; 855: 159003, 2023 Jan 10.
Artículo en Inglés | MEDLINE | ID: mdl-36155041

RESUMEN

A majority of clay minerals contain Fe, and the redox cycling of Fe(III)/Fe(II) in clay minerals has been extensively studied as it may fuel the biogeochemical cycles of nutrients and govern the mobility, toxicity and bioavailability of a number of environmental contaminants. There are three types of Fe in clay minerals, including structural Fe sandwiched in the lattice of clays, Fe species in interlayer space and adsorbed on the external surface of clays. They exhibit distinct reactivity towards contaminants due to their differences in redox properties and accessibility to contaminant species. In natural environments, microbially driven Fe(III)/Fe(II) redox cycling in clay minerals is thought to be important, whereas reductants (e.g., dithionite and Fe(II)) or oxidants (e.g., peroxygens) are capable of enhancing the rates and extents of redox dynamics in engineered systems. Fe(III)-containing clay minerals can directly react with oxidizable pollutants (e.g., phenols and polycyclic aromatic hydrocarbons (PAHs)), whereas structural Fe(II) is able to react with reducible pollutants, such as nitrate, nitroaromatic compounds, chlorinated aliphatic compounds. Also structural Fe(II) can transfer electrons to oxygen (O2), peroxymonosulfate (PMS), or hydrogen peroxide (H2O2), yielding reactive radicals that can promote the oxidative transformation of contaminants. This review summarizes the recent discoveries on redox reactivity of Fe in clay minerals and its links to fates of environmental contaminants. The biological and chemical reduction mechanisms of Fe(III)-clay minerals, as well as the interaction mechanism between Fe(III) or Fe(II)-containing clay minerals and contaminants are elaborated. Some knowledge gaps are identified for better understanding and modelling of clay-associated contaminant behavior and effective design of remediation solutions.


Asunto(s)
Contaminantes Ambientales , Hierro , Arcilla , Hierro/química , Peróxido de Hidrógeno , Minerales/química , Oxidación-Reducción , Compuestos Ferrosos/química , Compuestos Férricos/química
10.
J Inorg Biochem ; 238: 112023, 2023 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-36270041

RESUMEN

Lactobacillaceae are a diverse family of lactic acid bacteria found in the gut microbiota of humans and many animals. These bacteria exhibit beneficial effects on intestinal health, including modulating the immune system and providing protection against pathogens, and many species are frequently used as probiotics. Gut bacteria acquire essential metal ions, like iron, zinc, and manganese, through the host diet and changes to the levels of these metals are often linked to alterations in microbial community composition, susceptibility to infection, and gastrointestinal diseases. Lactobacillaceae are frequently among the organisms increased or decreased in abundance due to changes in metal availability, yet many of the molecular mechanisms underlying these changes have yet to be defined. Metal requirements and metallotransporters have been studied in some species of Lactobacillaceae, but few of the mechanisms used by these bacteria to respond to metal limitation or excess have been investigated. This review provides a current overview of these mechanisms and covers how iron, zinc, and manganese impact Lactobacillaceae in the gut microbiota with an emphasis on their biochemical roles, requirements, and homeostatic mechanisms in several species.


Asunto(s)
Microbioma Gastrointestinal , Humanos , Animales , Lactobacillaceae , Manganeso/farmacología , Bacterias , Zinc/farmacología , Hierro/farmacología
11.
J Inorg Biochem ; 238: 112024, 2023 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-36272187

RESUMEN

Although cobalt is a required nutrient, it is toxic due to its ability to generate reactive oxygen species (ROS) and damage DNA. ROS generation by Co2+ often has been compared to that of Fe2+ or Cu+, disregarding the reduction potential differences among these metal ions. In plasmid DNA damage studies, a maximum of 15% DNA damage is observed with Co2+/H2O2 treatment (up to 50 µM and 400 µM, respectively) significantly lower than the 90% damage observed for Fe2+/H2O2 or Cu+/H2O2 treatment. However, when ascorbate is added to the Co2+/H2O2 system, a synergistic effect results in 90% DNA damage. DNA damage by Fe2+/H2O2 can be prevented by polyphenol antioxidants, but polyphenols both prevent and promote DNA damage by Cu+/H2O2. When tested for cobalt-mediated DNA damage affects, eight of ten polyphenols (epicatechin gallate, epigallocatechin gallate, propyl gallate, gallic acid, methyl-3,4,5-trihydroxybenzoate, methyl-4,5-dihydroxybenzoate, protocatechuic acid, and epicatechin) prevent cobalt-mediated DNA damage with IC50 values of 1.3 to 27 µM and two (epigallocatechin and vanillic acid) prevent little to no DNA damage. EPR studies demonstrate cobalt-mediated formation of •OH, O2•-, and •OOH, but not 1O2 in the presence of H2O2 and ascorbate. Epigallocatechin gallate and methyl-4,5-dihydroxybenzoate significantly reduce ROS generated by Co2+/H2O2/ascorbate, consistent with their prevention of cobalt-mediated DNA damage. Thus, while cobalt, iron, and copper are all d-block metal ions, cobalt ROS generation and its prevention is significantly different from that of iron and copper.


Asunto(s)
Antioxidantes , Polifenoles , Antioxidantes/farmacología , Polifenoles/farmacología , Especies Reactivas de Oxígeno , Cobalto , Peróxido de Hidrógeno , Cobre , Oxidación-Reducción , Estrés Oxidativo , Hierro
12.
J Inorg Biochem ; 238: 112035, 2023 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-36327499

RESUMEN

Nitric oxide synthase (NOS) is a cytochrome P450-type mono­oxygenase that catalyzes the oxidation of L-arginine to nitric oxide. We previously observed that intramolecular electron transfer from biopterin to Fe2+-O2 in Deinococcus radiodurans NOS (DrNOS) using pulse radiolysis. However, the rate of electron transfer in DrNOS (2.2 × 103 s-1) contrasts with a reported corresponding rate (11 s-1) in a mammalian NOS determined using rapid freeze-quench (RFQ) EPR. We applied pulse radiolysis to Bacillus subtilis NOS (bsNOS) and to rat neural NOS oxygenase domain NOS (mNOS). Concurrently, RFQ EPR was used to trap a pterin radical during single-turnover enzyme reactions of the enzymes. By using the pulse radiolysis method, hydrated electrons (eaq-) reduced the heme iron of NOS enzymes. Subsequently, ferrous heme reacted with O2 to form a Fe2+-O2 intermediate. In the presence of pterin, the intermediate of bsNOS was found to convert to other intermediate in the time range of milliseconds. A similar process was determined to have occurred after pulse radiolysis of the pterin-bound mNOS, though the rate was much slower. The intermediates of all of the NOS enzymes further converted to the original ferric form in the time range of seconds. When using the RFQ method, pterin radicals were formed very rapidly in both DrNOS and bsNOS in the time range of milliseconds. In contrast, the pterin radical in mNOS was observed to form slowly, at a rate of ∼20 s-1.


Asunto(s)
Biopterina , Óxido Nítrico , Ratas , Animales , Biopterina/metabolismo , Óxido Nítrico/metabolismo , Electrones , Óxido Nítrico Sintasa/metabolismo , Hemo/metabolismo , Oxidación-Reducción , Arginina/metabolismo , Pterinas , Hierro , Compuestos Ferrosos , Óxido Nítrico Sintasa de Tipo II , Mamíferos/metabolismo
13.
J Inorg Biochem ; 238: 112055, 2023 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-36335746

RESUMEN

Iron is the trace element of natural selection by the biological systems due to its versatile coordination chemistry, and is recently explored for medicinal and diagnostic applications. Photo-activated states of iron complexes exhibiting substitution, dissociation, isomerization reactions, intramolecular redox reactions or energy transfer to other molecules have attracted the attention across the globe for the potent applications in photo-chemotherapy. There is a significant advancement on the development of iron-based complexes for photochemotherapeutic applications. Here in we reviewed the photo-activated states and photochemistry of iron complexes, and recent advances made in the area of photochemotherapy of iron complexes relevant to the photochemistry of iron complexes.


Asunto(s)
Complejos de Coordinación , Fotoquimioterapia , Hierro/química , Fotoquímica , Oxidación-Reducción , Complejos de Coordinación/química
14.
Sci Total Environ ; 856(Pt 1): 159037, 2023 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-36179839

RESUMEN

The problem of nitrate contamination in water has attracted widespread attention. Original biochar has a poor adsorption capacity for nitrate adsorption. Iron impregnation and acid protonation (base deprotonation) are common modification methods for biochar. In order to develop iron-mediated biochar containing multi-functional groups for enhancing nitrate adsorption, Fe-BC@H and Fe-BC@OH were prepared using a two-stage development process, including an iron-based carbon pyrolysis followed by acid protonation (or base deprotonation). The pseudo-second-order kinetic and Langmuir models can well describe the adsorption process which is a physicochemical complex monolayer adsorption. The data proved that Fe-BC@H (9.35 mg/g NO3--N) had a stronger adsorption capacity than Fe-BC@OH (2.95 mg/g NO3--N). Surface morphologies, functional groups, and mineral compositions of Fe-BC@H and Fe-BC@OH were analyzed through Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Characterization results showed that acid protonation can further improve the specific surface area (SSA), pore volume, and Zeta potential of Fe-based biochar, providing more adsorption sites for nitrate and enhancing the electrostatic force between nitrate and biochar. However, these effects were suppressed through base deprotonation. In addition, acid protonation can significantly increase the type and number of functional groups of biochar to enhance the chemisorption of nitrate. Such results suggested that the acid protonation can further improve the adsorption capacity of Fe-based biochar for nitrate, while base deprotonation had an inhibitory effect on that of Fe-based biochar. Overall, this study reveals that specific surface area, electrostatic force, and functional groups are crucial effects of the nitrate adsorption on acid/base modified biochar.


Asunto(s)
Nitratos , Contaminantes Químicos del Agua , Adsorción , Nitratos/química , Hierro/química , Electricidad Estática , Contaminantes Químicos del Agua/química , Carbón Orgánico/química , Óxidos de Nitrógeno , Cinética , Espectroscopía Infrarroja por Transformada de Fourier
15.
Sci Total Environ ; 856(Pt 1): 159078, 2023 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-36179848

RESUMEN

The acidophilic sulfur oxidizing bacterium (SOB), Acidithiobacillus ferrooxidans, has been found to stimulate elemental sulfur (S0) oxidation and mineral weathering in alkaline Fe ore tailings. However, A. ferrooxidans growth and activities depend on the pH conditions surrounding their interfaces with minerals. The present study aimed to investigate how pH influences bacterial growth and functions in Fe ore tailings. A simulated aquatic 'homogeneous' incubation system was initially adjusted into acidic (pH 4), neutral (pH 7) and alkaline (pH 9) conditions, which mimicked the microenvironmental conditions of the water-cell-mineral interfaces in the tailings. It was found that A. ferrooxidans grew well and oxidised S0 under the prevailing and initially acidic conditions (pH < 6). These stimulated the weathering of biotite and amphibole-like minerals and the formation of nanosized jarosite and ferrihydrite-like minerals mediated by extracellular polymer substrate (EPS). In contrast, the initially neutral/alkaline pH conditions (i.e., pH > 7) with the presence of the alkaline tailings restricted SOB growth and functions in S0-oxidation and mineral weathering. These findings suggest that it is essential to prime acidic conditions in microenvironments to support SOB growth, activities, and functions toward mineral weathering in tailings, providing critical basis for involving SOB in eco-engineered pedogenesis in tailings.


Asunto(s)
Minerales , Azufre , Bacterias , Oxidación-Reducción , Hierro , Concentración de Iones de Hidrógeno
16.
Sci Total Environ ; 856(Pt 1): 159081, 2023 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-36179843

RESUMEN

Simultaneous nitrification and denitrification (SND) has the advantage of energy saving and carbon demand reduction. Here, readily available low-cost iron scraps packing was added to an aerobic sludge system. This successfully enhanced the efficiency of total nitrogen removal from 37.7 ± 13.2 % to 62.7 ± 7.9 % over 2 days. While electrons from iron biocorrosion did not contribute to nitrate reduction, iron promoted heterotrophic denitrification. The iron scraps changed the spatial distribution of the microbial community, where more denitrification bacteria accumulated around the packing and higher denitrification capacity was noted. Metagenomic analysis of the sludge cultured in the presence of iron scraps for 2 days revealed that, with the exception of the enriched amoA/B/C gene expression, the abundance of other key nitrogen removal genes showed little variation. Furthermore, the structure of the microbial community was unchanged probably due to the relatively short culturing period. However, metatranscriptomic analysis indicated that iron increased the abundance of nitrifying bacteria (i.e. unclassified Nitrosomonas, Nitrosomonas sp. Is79A3 and Nitrospira defluvii) and promoted higher expression of nitrification genes. Notably, iron scraps packing decreased the abundance of the key denitrification bacteria Thauera sp. MZ1T from 52.92 to 7.58 %. The expression of napA/B also decreased, while expression of narG/H/I increased by 9 to 23 fold and a 2 to 3 fold over expression was noted for nirS, norB/C and nosZ in the presence of iron scraps. This suggested that aerobic denitrification was inhibited and anaerobic denitrification was promoted. This study has provided in-depth understanding of the influence of iron on SND to improve the application of iron-supported biological processes.


Asunto(s)
Nitrógeno , Aguas del Alcantarillado , Desnitrificación , Hierro , Reactores Biológicos , Nitrificación , Aguas Residuales
17.
Sci Total Environ ; 856(Pt 2): 159142, 2023 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-36183767

RESUMEN

Acid sulfate soils discharge large amounts of sulfuric acid along with toxic metals, deteriorating water quality and ecosystem health of recipient waterbodies. There is thus an urgent need to develop cost-effective and sustainable measures to mitigate the negative effects of these soils. In this study, we flushed aseptically-prepared MQ water (reference) or mitigation suspensions containing calcite, peat or a combination of both through 15-cm-thick soil cores from an acid sulfate soil field in western Finland, and investigated the geochemistry of Fe and S on the surfaces of macropores and in the solid columnar blocks (interiors) of the soil columns. The macropore surfaces of all soil columns were strongly enriched in total and HCl-extractable Fe and S relative to the interiors, owing to the existence of abundant Fe oxyhydroxysulfates (schwertmannite and partly jarosite) as yellow-to-brownish surface-coatings. The dissolution/hydrolysis of Fe oxyhydroxysulfates (predominantly jarosite) on the macropore surfaces of the reference columns, although being constantly flushed, effectively buffered the permeates at pH close to 4. These results suggest that Fe oxyhydroxysulfates accumulated on the macropore surfaces of boreal acid sulfate soils can act as long-lasting acidification sources. The treatments with mitigation suspensions led to a (near-)complete conversion of jarosite to Fe hydroxides, causing a substantial loss of S. In contrast, we did not observe any recognizable evidence indicating transformation of schwertmannite. However, sulfate sorbed by this mineral might be partially lost through anion-exchange processes during the treatments with calcite. No Fe sulfides were found in the peat-treated columns. Since Fe sulfides can support renewed acidification events, the moderate mineralogical changes induced by peat are desirable. In addition, peat materials can act as toxic-metal scavengers. Thus, the peat materials used here, which is relatively cheap in the boreal zone, is ideal for remediating boreal acid sulfate soils and other similar jarosite-bearing soils.


Asunto(s)
Hierro , Suelo , Hierro/análisis , Carbonato de Calcio , Ecosistema , Sulfatos , Azufre , Ácidos , Sulfuros
18.
Sci Total Environ ; 856(Pt 2): 159186, 2023 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-36202351

RESUMEN

The reduction process of pollutants by nano zero-valent iron (nZVI) is limited by mass transfer and its effective utilization, and previous studies have ignored the electron loss caused by its oxidative passivation. The carbon-coated structure can effectively inhibit the oxidation of nZVI, but the effectiveness of carbon-coated nZVI (Fe0@C) as a reducing agent in soil remediation is unclear. Therefore, in this study, the Fe0@C/surfactant system was used to remove soil-adsorbed nitrobenzene (NB) to simultaneously enhance the mass transfer process and effective utilization of nZVI. The results showed that the use of surfactants effectively promoted the desorption of NB adsorbed by the soil, and the desorption process was affected by factors such as the type and concentration of surfactants, water-soil ratio, and soil organic matter (SOM) content. The enhanced desorption of NB by the surfactant in the soil system promoted the effective contact between the composite and NB, thereby enhancing the reduction of NB by the composite. In addition, Fe0@C exhibited excellent performance for the reduction of soil-adsorbed NB compared with the conventional nZVI, and this advantage was more obvious in the potting soil system. However, the composite will be gradually passivated due to the alkaline environment during the reduction process, and this phenomenon was especially obvious in the campus soil system. When the pH value decreased from 9 to 3, the proportion of aniline (AN) generated in the campus soil system increased from 19.37 % to 69.29 %. In addition, in potting soil systems with high SOM content, the adsorption of soil particles to the composite and the high dissolved organic matter (DOM) content resulting from the high SOM content also negatively affected the reduction process. The conclusions of this study demonstrate the great potential of the Fe0@C/surfactant system for in-situ contaminated site remediation applications.


Asunto(s)
Restauración y Remediación Ambiental , Contaminantes del Suelo , Contaminantes Químicos del Agua , Hierro/química , Suelo/química , Tensoactivos/química , Carbono , Contaminantes Químicos del Agua/análisis , Nitrobencenos/química , Contaminantes del Suelo/química
19.
Sci Total Environ ; 856(Pt 2): 159226, 2023 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-36202358

RESUMEN

Both earthworms and nano zero-valent iron (nZVI) have been recently regarded as important approaches for in-situ remediation of polychlorinated biphenyls (PCBs) in soil. However, the combined action of earthworms and nZVI toward PCBs, and the biological responses of earthworm-microbiota symbionts to nZVI-PCBs co-exposure in soil remediation systems remain unclear. In this study, a 28-d exposure with different levels of polychlorinated biphenyls (PCBs) and nZVI was applied to earthworm Eisenia fetida in an agricultural soil. Both physiological responses of earthworms and their surrounding microbiota in gut and soil were examined. Kinetic modelling parameters showed a doubled PCB accumulation in earthworms with the presence of nZVI. Meanwhile, nZVI-PCBs coexposure synergistically stimulated the activities of superoxide dismutase (SOD) and catalase (CAT), along with the elevated levels of reactive oxygen species (ROS), malondialdehyde (MDA) and glutathione (GSH) in earthworms. Based on integrated metabolomic and 16S rRNA analysis, it was found that earthworms provided certain metabolites, e.g., S-(2-hydroxyethyl)glutathione, 16-hydroxypalmitic acid, and formamide, beneficial to PCB-degrading microbiota (Novosphingobium and Achromobacter) in the intestine. Our findings of nZVI-enhanced PCB bioaccumulation and the defense mechanism afforded by the earthworm-microbiota symbionts toward PCB-nZVI exposure show the promise of combining earthworms with nZVI for the remediation of PCBs-contaminated soil.


Asunto(s)
Microbiota , Oligoquetos , Bifenilos Policlorados , Contaminantes del Suelo , Animales , Oligoquetos/fisiología , Suelo , Bifenilos Policlorados/análisis , Hierro/análisis , Contaminantes del Suelo/análisis , ARN Ribosómico 16S
20.
Chemosphere ; 311(Pt 1): 136898, 2023 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-36257394

RESUMEN

To prevent the scale formation in the equipments and pipelines after pre-treated coal gasification gray water (CGGW) entering the reuse system and reduce the influence of various pollutants in the effluent on subsequent biochemical treatment, this study presented a coupled use of pulse electrocoagulation (PEC) and chemical precipitation (CP) coupling method for the pretreatment of coal gasification gray water (CGGW). In addition, the operation parameters of PEC and the reaction conditions of PEC-CP were optimized based on iron plate as electrode and total hardness, turbidity and sludge yield as assessment indicators. Due to the formation of multi-hydroxyl iron by several minutes of pulse current, and the addition of pH regulator and coagulant aid, the efficient removal of various ions, hardness and turbidity was significantly reduced via various mechanism such as redox, precipitation, adsorption and coagulation reaction. The result indicated that under the optimal operation conditions, the total hardness, turbidity, and Fen+ of PEC-CP effluents were 275.0 mg/L, 3.0 NTU and 5.6 mg/L, respectively and sludge amount was 0.88 kg/m3. The removal rates of Si, B, Mn, Ba, COD, NPOC and NH4+-N by PEC-CP reached 80.0%, 75.4%, 97.0%, 99.8%, 35.0%, 33.6% and 23.8%, respectively. The present results suggested that the CGGW pretreatment effluents could be not only reused directly, but also greatly alleviate the scaling problem of water pipeline and coal gasification production facilities.


Asunto(s)
Contaminantes Ambientales , Contaminantes Químicos del Agua , Carbón Mineral , Aguas Residuales , Aguas del Alcantarillado , Agua , Precipitación Química , Electrocoagulación , Hierro , Contaminantes Químicos del Agua/análisis , Eliminación de Residuos Líquidos/métodos
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA
...