As(iii) removal through catalytic oxidation and Fe(iii) precipitation.
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ABSTRACT:
SUBMITTER: Oshima K
PROVIDER: S-EPMC9171746 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Mobilization of Arsenic in groundwater is primarily induced by reductive dissolution of As-rich Fe(III) oxyhydroxides under anoxic conditions. Creating a well-controlled artificial environment that favors oxidative precipitation of Fe(II) and subsequent oxidation and uptake of aqueous As can serve as a remediation strategy. We reported a proof of concept study of a novel iron-based dual anode system for As(III) oxidation and removal in synthetic groundwater. An iron anode was used to produce Fe(II) under iron-deficient conditions, and another inert anode was used to generate O2 for oxidative precipitation of Fe(II). For 30 min's treatment, 6.67 ?M (500 ?g/L) of As(III) was completely oxidized and removed from the solution during the oxidative precipitation process when a total current of 60 mA was equally partitioned between the two anodes. The current on the inert anode determined the rate of O2 generation and was linearly related to the rates of Fe(II) oxidation and of As oxidation and removal, suggesting that the process could be manipulated electrochemically. The composition of Fe precipitates transformed from carbonate green rust to amorphous iron oxyhydroxide as the inert anode current increased. A conceptual model was proposed for the in situ application of the electrochemically induced oxidative precipitation process for As(III) remediation.
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Project description:Antimony (Sb) pollution is a worldwide problem. In some anoxic sites, such as Sb mine drainage and groundwater sediment, the Sb concentration is extremely elevated. Therefore, effective Sb remediation strategies are urgently needed. In contrast to microbial aerobic antimonite [Sb(III)] oxidation, the mechanism of microbial anaerobic Sb(III) oxidation and the effects of nitrate and Fe(II) on the fate of Sb remain unknown. In this study, we discovered the mechanism of anaerobic Sb(III) oxidation coupled with Fe(II) oxidation and denitrification in the facultative anaerobic Sb(III) oxidizer Sinorhizobium sp. GW3. We observed the following: (1) under anoxic conditions with nitrate as the electron acceptor, strain GW3 was able to oxidize both Fe(II) and Sb(III) during cultivation; (2) in the presence of Fe(II), nitrate and Sb(III), the anaerobic Sb(III) oxidation rate was remarkably enhanced, and Fe(III)-containing minerals were produced during Fe(II) and Sb(III) oxidation; (3) qRT-PCR, gene knock-out and complementation analyses indicated that the arsenite oxidase gene product AioA plays an important role in anaerobic Sb(III) oxidation, in contrast to aerobic Sb(III) oxidation; and (4) energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and powder X-ray diffraction (XRD) analyses revealed that the microbially produced Fe(III) minerals were an effective chemical oxidant responsible for abiotic anaerobic Sb(III) oxidation, and the generated Sb(V) was adsorbed or coprecipitated on the Fe(III) minerals. This process included biotic and abiotic factors, which efficiently immobilize and remove soluble Sb(III) under anoxic conditions. The findings revealed a significantly novel development for understanding the biogeochemical Sb cycle. Microbial Sb(III) and Fe(II) oxidation coupled with denitrification has great potential for bioremediation in anoxic Sb-contaminated environments.
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Project description:Feammox-based nitrogen removal technology can reduce energy consumption by aeration and emission of carbon dioxide. However, the huge theoretical demand for Fe(III) becomes a challenge for the further development of Feammox. This study investigated an anammox-derived Feammox process with an intermittent dosage of Fe2O3 and proposed a novel approach to reduce the Fe(III) consumption. The results showed that anammox genera Candidatus Brocadia and Candidatus Kuenenia in the seed anammox sludge significantly decreased after cultivation. The formation of N2 was the dominating pathway in Feammox while that of nitrite and nitrate could be neglected. Batch tests showed that specific Feammox activity of ammonium oxidation was 1.14-9.98 mg N/(g VSS·d). The maximum removal efficiency of ammonium reached 52.3% in the bioreactor with a low dosage of Fe(III) which was only 5.8% of the theoretical demand in Feammox. The removal of ammonium was mainly achieved through Feammox, while partial nitrification/anammox also played a role due to the non-power and unintentional oxygen leakage. The super-low oxygen also responded to the low demand of Fe(III) in the bioreactor because it could trigger the cycle of Fe(III)/Fe(II) by coupling Feammox and chemical oxidation of Fe(II) to Fe(III). Therefore, anammox-derived Feammox can achieve the removal of ammonium with low Fe(III) demand at super-low oxygen.
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Project description:Phosphorus (P) removal is a significant issue in wastewater treatment. This study applies Fe-Al composite coagulant to the advanced treatment of different P forms in biological effluent. For 90% total P removal, the dosage of FeCl3-AlCl3 composite coagulant reduces by 27.19% and 43.28% than FeCl3 and AlCl3 only, respectively. Changes in effluent P forms could explain the phenomenon of composite coagulant dosage reduction. The suspended P in the effluent of composite coagulant is easier removed by precipitation than single coagulant. In this study, the hydrolysis speciations of Fe3+, Fe2+, and Al3+ at a pH range are calculated by Visual MINTEQ. Changes in the morphology of metal hydroxides correlate with P removal at pH 4-9. Besides, analyses of scanning electron microscope (SEM), Fourier transformed infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) are performed on the coagulation precipitations. Fe2+ reacts directly with P to form flocs of Fe3(PO4)2, and Al2(SO4)3 assists in the sedimentation of the small-volume flocs. Al13 is a significant hydrolysis product of Al3+, and Fe and P would substitute for the peripheral AlVI of the Al13 structure to form stable Fe-O-Al covalent bonds.
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Project description:This SuperSeries is composed of the SubSeries listed below.
2024-02-01 | GSE242760 | GEO
Project description:Excessive phosphorus (P) in water is the main reason
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Project description:The oxidation of the C-H and C=C bonds of hydrocarbons with H2O2 catalyzed by non-heme iron complexes with pentadentate ligands is widely accepted as involving a reactive FeIV=O species such as [(N4Py)FeIV=O]2+ formed by homolytic cleavage of the O-O bond of an FeIII-OOH intermediate (where N4Py is 1,1-bis(pyridin-2-yl)-N,N-bis(pyridin-2-ylmethyl)methanamine). We show here that at low H2O2 concentrations the FeIV=O species formed is detectable in methanol. Furthermore, we show that the decomposition of H2O2 to water and O2 is an important competing pathway that limits efficiency in the terminal oxidant and indeed dominates reactivity except where only sub-/near-stoichiometric amounts of H2O2 are present. Although independently prepared [(N4Py)FeIV=O]2+ oxidizes stoichiometric H2O2 rapidly, the rate of formation of FeIV=O from the FeIII-OOH intermediate is too low to account for the rate of H2O2 decomposition observed under catalytic conditions. Indeed, with excess H2O2, disproportionation to O2 and H2O is due to reaction with the FeIII-OOH intermediate and thereby prevents formation of the FeIV=O species. These data rationalize that the activity of these catalysts with respect to hydrocarbon/alkene oxidation is maximized by maintaining sub-/near-stoichiometric steady-state concentrations of H2O2, which ensure that the rate of the H2O2 oxidation by the FeIII-OOH intermediate is less than the rate of the O-O bond homolysis and the subsequent reaction of the FeIV=O species with a substrate.
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Project description:Ascorbic acid has been reported to stimulate DNA iterative oxidase TET enzymes, Jumonji C-domain-containinghistone demethylase and potentially RNA m6A demethylase FTO and ALKBH5 as a cofactor. Although ascorbic acid has been widely investigated in reprogramming DNA and histone methylation status in vitro, in cell lines and mouse models, its specific role in the catalytic cycle of dioxygenases remains enigmatic. Here we systematically investigated the stimulation of ascorbic towards TET2, ALKBH3, histone demethylases and FTO. We find that ascorbic acid reprograms epitranscrip-tome by erasing the hypermethylated m6A sites. Biochemistry and Electron spin resonance (ESR) assays demonstrate that ascorbic acid enters the active pocket of dioxygenases, reduces Fe (III), either incorporated upon protein synthesis or generated upon rebounding the hydroxyl radical during oxidation, into Fe (II). Finally, we propose a new model for the catalytic cycle of dioxygenases by adding in the essential dynamic cofactor, ascorbic acid. Ascorbic acid refreshes and regenerates inactive dioxygenase through recycling Fe (III) into Fe (II) in a dynamic “hit-and-run” manner.
2024-02-01 | GSE242758 | GEO
Project description:Microbially mediated anaerobic oxidation of methane (AOM) is a key process in the regulation of methane emissions to the atmosphere. Iron can serve as an electron acceptor for AOM, and it has been suggested that Fe(III)-dependent AOM potentially comprises a major global methane sink. Although it has been proposed that anaerobic methanotrophic (ANME) archaea can facilitate this process, their active metabolic pathways have not been confirmed. Here we report the enrichment and characterisation of a novel archaeon in a laboratory-scale bioreactor fed with Fe(III) oxide (ferrihydrite) and methane. Long-term performance data, in conjunction with the 13C- and 57Fe-labelling batch experiments, demonstrated that AOM was coupled to Fe(III) reduction to Fe(II) in this bioreactor. Metagenomic analysis showed that this archaeon belongs to a novel genus within family Candidatus Methanoperedenaceae, and possesses genes encoding the "reverse methanogenesis" pathway, as well as multi-heme c-type cytochromes which are hypothesised to facilitate dissimilatory Fe(III) reduction. Metatranscriptomic analysis revealed upregulation of these genes, supporting that this archaeon can independently mediate AOM using Fe(III) as the terminal electron acceptor. We propose the name Candidatus "Methanoperedens ferrireducens" for this microorganism. The potential role of "M. ferrireducens" in linking the carbon and iron cycles in environments rich in methane and iron should be investigated in future research.
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