Mechanism Of Fe2 Research Articles

Removal of Fe2+ in coastal aquaculture source water by manganese ores: Batch experiments and breakthrough curve modeling.

Excessive Fe2+ in coastal aquaculture source water will seriously affect the aquaculture development. This study used manganese sand to investigate the removal potential and mechanism of Fe2+ in coastal aquaculture source water by column experiments. The pseudo-first-order kinetic model could better describe Fe2+ removal process with R2 in the range of 0.9451-0.9911. More than 99.7% of Fe2+ could be removed within 120 min while the removal rate (k) was positively affected by low initial concentration of Fe2+, high temperature, and low pH. Logistic growth (S-shaped growth) model could better fit the concentration variation of Fe2+ in the effluent of the column (R2>0.99). The Fe2 breakthrough curve could be fitted by Bohart-Adams, Yoon-Nelson, and Thomas models (R2>0.95). Smooth slices with irregular shapes existed on the surface of manganese sand after the reaction while Fe content increased significantly on the surface of manganese sand after the column experiment. Moreover, FeO (OH) was mainly formed on the surface of manganese sand after the reaction. PRACTITIONER POINTS: Fe2+ in coastal aquaculture source water could be removed by manganese ores. The pseudo-first-order kinetic model better described the Fe2+ removal process. FeO (OH) was mainly formed on the surface of manganese sand after the reaction.

Piezoelectric charges promote FeS2 regeneration for efficient catalytical seawater splitting H2 evolution

Piezoelectric catalytic seawater hydrogen production is one of the most crucial and potential hydrogen production strategies. However, the low surface activity and the high carrier recombination rate limit the further improvement of catalytic efficiency. To solve this problem, we prepared SrBi4Ti4O15 (SBTO) and FeS2 (FS) heterojunctions, which can effectively utilize the valence state transformation cycle between Fe2+ and Fe3+ to improve the surface activity and maintain carrier separation. This mechanism of Fe2+ and Fe3+ conversion is similar to the well-known Fenton reaction. It was confirmed by electrochemical measurements that with the help of FeS2, SBTO possessed a stronger piezoelectric current response and faster carrier transfer rate. Piezoelectric catalytic seawater splitting H2 evolution rate of SBTO-25 %FeS2 could reach 31 mmol g-1h−1, which is higher than that of other piezoelectric materials in similar conditions. Our findings provide valuable insights for further improving the efficiency of seawater hydrogen production efficiency.

Model simulation and mechanism of Fe(0/II/III) cycle activated persulfate degradation of methylparaben based on hydroxylamine enhanced nano-zero-valent iron

The mechanism of Fe2+-activated peroxodisulfate (PDS) by hydroxylamine (HA) has been investigated, however, nano zero-valent iron-activated persulfate (nZVI/PDS) has a more optimal effect and needs further investigation. This study investigated the addition of HA to nZVI/PDS to improve Fe2+ regeneration and accelerate methylparaben (MP) degradation by Fe (0/II/III) cycle. After 60 min of reaction, the HA-enhanced nZVI/PDS (HA/nZVI/PDS) system afforded a 21% increase in MP degradation, reaching 93.26% (1 mM HA, 1 mM nZVI, and 2 mM PDS). nZVI/PDS system was a second-order reaction, but after adding HA, the reaction was more suitable for the first-order reaction. The addition of HA effectively promoted the reduction of Fe3+ to Fe2+ to improve the effect and reaction rate of PDS degradation of MP (k increased from 0.0127 min−1 to 0.0198 min−1) and broadened the reaction pH range. The results of various characterizations of nZVI before and after the reaction revealed that nZVI changed from a spherical structure to a bundle structure and was slightly oxidized. Changes in the Fe2+ and Fe3+ concentrations as well as in the pH of the reaction systems were monitored and the possible reactions of the HA/nZVI/PDS system were derived for the first time (knZVI/PDS<3.7 × 106 M−1 s−1, kFe3+/NH2O· >4.2 min−1). 12 potential compounds were investigated and MP breakdown pathways were speculated; hydroxylation was determined to be the most important pathway of degradation. And the HA/nZVI/PDS system had universal applicability.

Promoted diffusion mechanism of Fe2.7wt.%Si-Fe10wt.%Si couples under magnetic field by atomic-scale observations

Diffusion behavior of newly designed Fe2.7wt.%Si-Fe10wt.%Si couples at 1100 °C for up to 12 h has been investigated under the 0, 0.8 and 3 T magnetic fields. Diffusion thickness of solid solution layer and weight percent of Si on Fe2.7wt.%Si side increase significantly under a magnetic field. Application of a magnetic field promotes the diffusion of solid solution layer through the possible diffusion of vacancies mainly due to the appearance of defects, which has been demonstrated by the increased dislocation density and broadening of the typical XRD peaks. Replacement of Si sits by Fe atoms in the crystal structure leads to the appearance of Fe diffraction peaks, which has been confirmed by the increased interplanar spacings under a magnetic field. The magnetic field benefits the depinning of dislocations and leads to higher dislocation density because of the magnetoplastic effect which has been confirmed by the significantly reduced thickness of Fe2.7wt.%Si. Nano-sized Fe3Si particles precipitate in the matrix with an orientation relationship on Fe10wt.%Si side as {220}Fe3Si || {220}matrix & < 1–10 >Fe3Si || < 1–10 >matrix. Fe3Si particles pin dislocation moving and lead to higher dislocation density.

Removal of Fe(Ⅱ), Mn(Ⅱ), and NH4+-N by Using δ-MnO2 Coated Zeolite

δ-MnO2/zeolite nanocomposites were prepared with natural zeolite, potassium permanganate, and manganese sulfate by oxidation-reduction precipitation, which were used to simultaneously remove Fe2+, Mn2+, and NH4+-N from groundwater. To investigate the performance and mechanism of Fe2+, Mn2+, and NH4+-N removal from groundwater by δ-MnO2/zeolite nanocomposites, static batch experiments were conducted under different environmental conditions in a zero-oxygen atmosphere using SEM, TEM, Zeta potential, FTIR, and XPS techniques. The experimental results showed that the manganese-oxide-coated natural zeolite was δ-MnO2, and Fe2+, Mn2+, and NH4+-N adsorption on the δ-MnO2/zeolite nanocomposites could be best described with the pseudo-second-order kinetic model and the Langmuir model. In addition, the maximum adsorption capacities of Fe2+, Mn2+, and NH4+-N were calculated to be 215.1, 23.6, and 7.64 mg·g-1, respectively. The removal mechanism of NH4+-N from the solutions by zeolite was via the action of ion exchange, and the adsorption and oxidation catalysis of δ-MnO2-coated zeolite were responsible for the removal of Fe2+ and Mn2+. This research indicates that δ-MnO2/zeolite nanocomposites could be used as highly efficient adsorbents to simultaneously remove Fe2+, Mn2+, and NH4+-N from water.

Toward a mechanistic understanding of Feo-mediated ferrous iron uptake.

Virtually all organisms require iron and have evolved to obtain this element in free or chelated forms. Under anaerobic or low pH conditions commonly encountered by numerous pathogens, iron predominantly exists in the ferrous (Fe2+) form. The ferrous iron transport (Feo) system is the only widespread mechanism dedicated solely to bacterial ferrous iron import, and this system has been linked to pathogenic virulence, bacterial colonization, and microbial survival. The canonical feo operon encodes for three proteins that comprise the Feo system: FeoA, a small cytoplasmic β-barrel protein; FeoB, a large, polytopic membrane protein with a soluble G-protein domain capable of hydrolyzing GTP; and FeoC, a small, cytoplasmic protein containing a winged-helix motif. While previous studies have revealed insight into soluble and fragmentary domains of the Feo system, the chief membrane-bound component FeoB remains poorly studied. However, recent advances have demonstrated that large quantities of intact FeoB can be overexpressed, purified, and biophysically characterized, revealing glimpses into FeoB function. Two models of full-length FeoB have been published, providing starting points for hypothesis-driven investigations into the mechanism of FeoB-mediated ferrous iron transport. Finally, in vivo studies have begun to shed light on how this system functions as a unique multicomponent complex. In light of these new data, this review will summarize what is known about the Feo system, including recent advancements in FeoB structure and function.

Determinants of Fe2+ over M2+ (M = Mg, Mn, Zn) Selectivity in Non-Heme Iron Proteins.

Iron cations are indispensable players in a number of vital biological processes such as respiration, cell division, nitrogen fixation, oxygen transport, nucleotide synthesis, oxidant protection, O2 activation in the metabolism of various organic substrates, gene regulation, and protein structure stabilization. The basic mechanisms and factors governing the competition between Fe2+ and other metal species from the cellular fluids such as Mg2+, Mn2+, and Zn2+ are, however, not well understood, and several outstanding questions remain. (i) How does the Fe2+ binding site select the "right" cation and protect itself from attacks by other biogenic cations present in the surrounding milieu? (ii) Do the iron binding sites employ different selectivity strategies toward metal cations possessing different ligand affinities and cytosolic concentrations? (iii) What are the key determinants of metal selectivity in Fe2+ proteins? In this study, by employing density functional theory calculations combined with polarizable continuum model computations, we endeavor to address these questions by evaluating the thermodynamic outcome of the competition between Fe2+ and Mg2+/Mn2+/Zn2+ in model non-heme mononuclear metal binding sites of various compositions and charge states. The present calculations, which are in line with available experimental data, shed light on the mechanism of Fe2+-Mg2+/Mn2+/Zn2+ competition in non-heme iron proteins and disclose the key factors governing the process.

Thermal behaviour of pyrope at 1000 and 1100 �C: mechanism of Fe2+ oxidation and decomposition model

The mechanism of thermally induced oxidation of Fe2+ from natural pyrope has been studied at 1000 and 1100 degreesC using Fe-57 Mossbauer spectroscopy in conjunction with XRD, XRF, AFM, QELS, TG, DTA and electron microprobe analyses. At 1000 degreesC, the non-destructive oxidation of Fe2+ in air includes the partial stabilization of Fe3+ in the dodecahedral 24c position of the garnet structure and the simultaneous formation of hematite particles (15-20 nm). The incorporation of the magnesium ions to the hematite structure results in the suppression of the Morin transition temperature to below 20 K. The general garnet structure is preserved during the redox process at 1000 degreesC, in accordance with XRD and DTA data. At 1100 degreesC, however, oxidative conversion of pyrope to the mixed magnesium aluminium iron oxide, Fe-orthoenstatite and cristoballite was observed. During this destructive decomposition, Fe2+ is predominantly oxidized and incorporated into the spinel structure of Mg(Al,Fe)(2)O-4 and partially stabilized in the structure of orthoenstatite, (Mg,Fe)SiO3. The combination of XRD and Mossbauer data suggest the definite reaction mechanism prevailing, including the refinement of the chemical composition and quantification of the reaction products. The reaction mechanism indicates that the respective distribution of Fe(2+)and Fe3+ to the enstatite and spinel structures is determined by the total content of Fe2+ in pyrope. (Less)

The mechanism of Fe2+-initiated lipid peroxidation in liposomes: the dual function of ferrous ions, the roles of the pre-existing lipid peroxides and the lipid peroxyl radical

The mechanism of Fe2+-initiated lipid peroxidation in liposomes: the dual function of ferrous ions, the roles of the pre-existing lipid peroxides and the lipid peroxyl radical

The mechanism of Fe2+-initiated lipid peroxidation in liposomes: the dual function of ferrous ions, the roles of the pre-existing lipid peroxides and the lipid peroxyl radical

The mechanism of Fe(2+)-initiated lipid peroxidation in a liposomal system was studied. It was found that a second addition of ferrous ions within the latent period lengthened the time lag before lipid peroxidation started. The apparent time lag depended on the total dose of Fe(2+) whenever the second dose of Fe(2+) was added, which indicates that Fe(2+) has a dual function: to initiate lipid peroxidation on one hand and suppress the species responsible for the initiation of the peroxidation on the other. When the pre-existing lipid peroxides (LOOH) were removed by incorporating triphenylphosphine into liposomes, Fe(2+) could no longer initiate lipid peroxidation and the acceleration of Fe(2+) oxidation by the liposomes disappeared. However, when extra LOOH were introduced into liposomes, both enhancement of the lipid peroxidation and shortening of the latent period were observed. When the scavenger of lipid peroxyl radicals (LOO(.)), N,N'-diphenyl-p-phenylene-diamine, was incorporated into liposomes, neither initiation of the lipid peroxidation nor acceleration of the Fe(2+) oxidation could be detected. The results may suggest that both the pre-existing LOOH and LOO(.) are necessary for the initiation of lipid peroxidation. The latter comes initially from the decomposition of the pre-existing LOOH by Fe(2+) and can be scavenged by its reaction with Fe(2+). Only when Fe(2+) is oxidized to such a degree that LOO(.) is no longer effectively suppressed does lipid peroxidation start. It seems that by taking the reactions of Fe(2+) with LOOH and LOO(.) into account, the basic chemistry in lipid peroxidation can explain fairly well the controversial phenomena observed in Fe(2+)-initiated lipid peroxidation, such as the existence of a latent period, the critical ratio of Fe(2+) to lipid and the required oxidation of Fe(2+).

Metal ion transporters and homeostasis.

Transition metals are essential for many metabolic processes and their homeostasis is crucial for life. Aberrations in the cellular metal ion concentrations may lead to cell death and severe diseases. Metal ion transporters play a major role in maintaining the correct concentrations of the various metal ions in the different cellular compartments. Recent studies of yeast mutants revealed key elements in metal ion homeostasis, including novel transport systems. Several of the proteins discovered in yeast are highly conserved, and defects in some of the yeast mutants could be complemented by their human homologs. The studies of yeast metal ion transporters helped to unravel the molecular mechanism of macrophage defense against bacterial infection and hereditary diseases.

The Mechanism of Fe2+Production by a Moderately Thermophilic Iron-oxidizing Bacterium Strain TI-1

The mechanism of Fe2+ production by a moderately thermophilic iron-oxidizing bacterium, strain TI-1, was studied. Strain TI-1 produced H2S outside of the cells when the following five l-amino acids, aspartic acid, glutamic acid, serine, arginine, and histidine, were added to the medium. The activity of H2S production was completely inhibited by uncouplers and inhibitors of cytochrome c oxidase or sulfite reductase. When Fe3 + was added to the H2S production medium, it was chemically reduced by the H2S produced by the strain to give Fe2+, the sole energy source of this bacterium.