Changes In Fe2 Research Articles

Mechanism of arsenic release process from arsenopyrite chemical oxidation

Oxidation of arsenopyrite is one of the main causes of arsenic pollution in the environment. This study, examind changes in the surface properties of arsenopyrite in the presence of oxygen. Furthermore, X-ray photoelectron spectroscopy, in situ Raman analysis, high-resolution transmission electron microscopy, and ab initio molecular dynamics were carried out on arsenopyrite, and the oxidation properties and processes of the arsenopyrite surface, along with the Fe/As/S oxidation processes, were analysed In situ-Raman spectroscopy data clearly showed that in the presence of oxygen, Fe2+ ions were transformed into Fe3+ ions on the surface of arsenopyrite at 207 cm−1, and the content of iron oxides on the surface of arsenopyrite increased significantly over time. The presence of iron promoted the oxidation of As(III), and the oxidation process was found to affect the oxidation of As atoms on the surface of arsenopyrite due to the presence of FeS bonds. The presence of As3+ intensified the oxidation of arsenopyrite surface (139 cm−1).The main reason was the presence of O2·-/HO2· on the surface of arsenopyrite, the change of Fe2+ → FeOH2+ → Fe3+ on the surface of arsenopyrite, and the change of As3+ → As4+ → As5+, which strengthened the overflow of As, leading to reconstruction and changes on the surface of arsenopyrite.

Unraveling synergistic mechanisms of polyacrylamide coagulation and Fe2+/CaO2 Fenton-like oxidation to enhance sludge dewatering

Enhancing sludge dewatering can effectively reduce the operational costs of wastewater treatment plants. In the present study, a synergistic process combining polyacrylamide (PAM) coagulation with Fe2+/CaO2 Fenton-like oxidation was proposed to improve the performance of sludge dewatering. The findings indicate that pre-addition of PAM before Fe2+/CaO2 treatment yielded superior dewatering performance, reducing the water content from 78.6% to 73.1% and the capillary suction time (CST) from 32.9 s to 19.5 s, respectively. Even with a CaO2 dosage of 62.5 mg/g DS, the ultimate pH of the filtrate remained near neutral, and effective dewatering performance was consistently attained. Results of particle size and zeta potential revealed that the addition of PAM enhanced the particle size by electric neutralization and bridging, thus accelerating sludge filtration. Furthermore, Fe2+/CaO2 facilitated the conversion of hydrophilic organic matter in tightly bound EPS (TB-EPS) to soluble EPS (SB-EPS) and loosely bound EPS (LB-EPS), and lysis of the sludge cells, contributing to a decrease in water content. Molecular analysis of EPS through Fourier-transform infrared spectroscopy (FT-IR) further elucidated the breakdown of hydrophilic functional groups by this combined method. Additionally, the changes of Fe2+, Fe3+, and H2O2 concentrations were investigated to explore the mechanism of enhanced sludge dewatering from a kinetic perspective. Ultimately, the concentration of typical heavy metals in the treated sludge sample significantly decreased, leading to a reduction in environmental risks. Overall, this study employed the safe and stable CaO2 as the source of H2O2, combined with Fe2+ to form a Fenton-like system. Meanwhile, PAM was utilized to flocculate the sludge firstly, and then Fe2+/CaO2 oxidation system was carried out to enhance sludge dewatering, which provided a promising sludge dewatering approach with potential applications.

A colorimetric and fluorometric dual-mode carbon dots probe derived from phenanthroline precursor for the selective detection of Fe2+ and Fe3.

Iron's metabolism is heavily involved in the regulation of redox balance for cell functions, however, the simultaneous monitoring of Fe2+/3+ concentration is still a great challenge due to their transitional nature in biological systems. A novel type of carbon dots (CDs) was synthesized by solvothermal treatment with 5-amino-1,10-phenanthroline (Aphen) and salicylic acid as precursors, and the resulting targeted CDs (T-CDs) were used to simultaneously detect Fe2+ and Fe3+. Comprehensive experimental characterizations revealed that the strong binding affinity of Aphen moiety to Fe2+ leads to the formation of rigid T-CDs aggregates, which causes a substantial enhancement of fluorescence intensity, whereas Fe3+ could cause the fluorescence quenching of T-CDs due to the oxidation-reduction induced electron transfer. These different fluorescence responses allow T-CDs to sensitively differentiate Fe2+ from Fe3+, and give the limit of detection (LOD) of 1.78 and 2.78μM for Fe2+ and Fe3+, respectively. Furthermore, the Aphen dominated structure endows the T-CDs with a colorimetric response to Fe2+ with a LOD of 0.13μM, which is very different from Fe3+. Thus, the dynamic changes of Fe2+ and Fe3+ in solution can be accurately monitored by T-CDs within the total iron concentration of 50μM, which is probably the most sensitive dual-mode probe reported so far. In addition, this probe is successfully applied to detect the Fe2+/3+ concentration in cells, demonstrating a huge application potential in the sensing of the dynamic equilibrium of these important transition metals during the cell metabolism or stimulated process. The dynamic changes of Fe2+ and Fe3+ in solution can be accurately monitored by carbon dots based on the colorimetric and fluorometric dual-mode.

Fe2+ imaging in ferroptosis and drug-induced liver injury with a ratiometric near-infrared fluorescent probe

Recently, great attention has been given to the detection of ferrous ion (Fe2+) in live organisms because it plays a vital role in life and is associated with ferroptosis and many diseases. Near-infrared (NIR) ratiometric fluorescence probes are essential tools, however, such probes for tracking Fe2+ in iron-associated diseases in vivo are rarely reported. Herein, we report a novel NIR ratiometric fluorescent probe NRF-Fe2+ for Fe2+ based on a fluorescence resonance energy transfer (FRET) system using the N-oxide chemistry. This probe shows significant ratiometric fluorescence changes (λem shifts from 460 nm to 675 nm) for Fe2+ with high selectivity and sensitivity, and can image both exogenous and endogenous Fe2+ in cells with low cytotoxicity and ratiometric fluorescence signals. The imaging of Fe2+ in mice with NRF-Fe2+ is also successfully applied. Finally, we demonstrate that the probe can be applied for monitoring the level changes of Fe2+ in ferroptosis and drug-induced liver injury. All the results show that NRF-Fe2+ is a useful tool for the detection of biological Fe2+ and the study of iron-related diseases.

Effects of pH and Cl− Content on Degradation Process of Pre-Passivated Stainless Steels in an Alkaline Solution

The degradation behavior of four prepassivated stainless steels (SSs) in the alkaline solutions with different Cl− concentrations and pH values were investigated by cyclic potentiodynamic polarization (CPP), electrochemical impedance spectroscopy (EIS) and Mott-Schottky analysis and the X-ray photoelectron spectroscopy (XPS). The results indicated that the pH value and Cl− concentration, together with the phase ratio difference in the microstructure of SS, played a critical role in the degradation process of passive film. At low pH and high Cl− concentration, the passive film gradually enriched in Fe3+ and Cr3+ species and depleted in Fe2+ oxides and its self-regeneration process became more difficult. As the pH decreased, the passive film exhibited clear n-type and p-type semiconductor characteristics more clearly, and the decrease in dopant density well reflected the changes in Fe2+/Fe3+ ratio and electrochemical behavior. Based on the viewpoint of adsorption balance between OH− with inhibitory effect and Cl− with promotion effect on the degradation process, a mechanism for the degradation process of prepassivation film was proposed.

Seal meat enzymatic hydrolysates and its digests: A comparison on protein and minerals profiles

Seal meat is of high nutritive value but currently a by-product and waste from seal oil processing. Seal meat hydrolysates were generated from alcalase catalysis and were subjected to a soft dynamic digestion system to study their nutritional value and the health benefits. The total amino acid content was determined as 568.54 and 384.65 mg/g for seal meat hydrolysates and its intestinal digests, respectively, using UPLC, and both of the samples were rich in essential amino acids such as Leu and Lys. There were no harmful minerals observed by ICP-MS analyses. Both the gastric and intestinal digests revealed nutritive minerals, i.e., Ca, Fe, Mg, Zn, among which the contents of Fe were 548 and 602 mg/kg, respectively, higher than common meat products. The absorbable Fe2+ ions content remained almost the same during the gastric and intestinal digestion, while the content of undesirable Fe3+ ions declined drastically in intestinal digests. The change of Fe2+ and Fe3+ ions was probably due to the antioxidant activities of seal meat hydrolysates observed via scavenging of DPPH and hydroxyl radicals. This study provides knowledge on seal meat hydrolysates as healthy food supplement.

Degradation of the mixed organic solvents of tributyl phosphate and n-dodecane by heterogeneous Fenton-like oxidation using nanoscale zero-valent iron as the catalyst

The treatment and disposal of spent radioactive organic solvents, i.e., tributyl phosphate (TBP) and diluent (such as kerosene, n-dodecane, etc.), produced in the reprocessing of spent fuel in the closed cycle are crucial for the sustainable development of the nuclear industry. In this study, the synthesized nanoscale zero-valent iron (nZVI) was used as the heterogeneous Fenton-like catalyst to promote the generation of hydroxyl radicals (•OH) by reacting with H2O2 to degrade the mixed organic solvents of TBP and n-dodecane. nZVI was characterized by scanning electron microscopy (SEM), nitrogen adsorption/desorption isotherms, and X-ray photoelectron spectroscopy (XPS) to investigate the micro-morphology, nano-particle size, and surface valence state. The change of Fe2+/Fe3+ concentration ratio during the reaction was measured to clarify the performance of nZVI. The effects of temperature, catalyst dosage, H2O2 dosage, and acidifier concentration on the degradation of TBP and n-dodecane were studied, and the results were complemented by the COD of the aqueous solution and the volume reduction rate of the organic phase. The mixed organic solvents of TBP and n-dodecane containing Co2+ were used to simulate the spent radioactive organic solvents and to study the distribution of nuclides after the reaction. The results showed that most of the radioactivity was in the residual solution, and the condensate contained almost no radioactivity. The degradation of TBP and n-dodecane was carried out separately, which showed that n-dodecane was more difficult to degrade. Density functional theory (DFT) calculations were applied to determine the adsorption energy of organic solvents and nZVI. According to the Fourier transform infrared spectra (FTIR) and their corresponding DFT calculations, liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) of the sample after the reaction, the possible intermediates were analyzed, and the degradation mechanism was speculated.

3D two-photon brain imaging reveals dihydroartemisinin exerts antiepileptic effects by modulating iron homeostasis

Imbalanced iron homeostasis plays a crucial role in neurological diseases, yet direct imaging evidence revealing the distribution of active ferrous iron (Fe2+) in the living brain remains scarce. Here, we present a near-infrared excited two-photon fluorescent probe (FeP) for imaging changes of Fe2+ flux in the living epileptic mouse brain. Invivo 3D two-photon brain imaging with FeP directly revealed abnormal elevation of Fe2+ in the epileptic mouse brain. Moreover, we found that dihydroartemisinin (DHA), a lead compound discovered through probe-based high-throughput screening, plays a critical role in modulating iron homeostasis. In addition, we revealed that DHA might exert its antiepileptic effects by modulating iron homeostasis in the brain and finally inhibiting ferroptosis. This work provides a reliable chemical tool for assessing the status of ferrous iron in the living epileptic mouse brain and may aid the rapid discovery of antiepileptic drug candidates.

First-principle study on the magnetic and optical properties of SnO2 doped with Fe2+/3+ and oxygen vacancies at different ratios

The effects of different ratios of Fe2+/3+ and oxygen vacancy doping on the magneto-optical properties and mechanism of SnO2 have not been fully investigated. Therefore, the electronic structure and magneto-optical properties of SnO2 doped with different concentrations of Fe and oxygen vacancies were studied through geometry optimization and energy calculation in accordance with the first-principle generalized gradient approximation + U(GGA + U) method of density functional theory. The effects of changes in Fe2+/3+ and oxygen vacancy concentration on the electronic structure, energy, magnetic exchange mode, and optical absorption properties of SnO2 materials were explored. Calculation results showed that doping with different concentrations of Fe2+/3+ and oxygen vacancies made the stability and magnetic moment of the doping system vary. The comparison of several doping systems with the same high magnetic moment showed that the Sn22[Fe3+]2O46 system demonstrates the best stability and magnetic value. Doping with different concentrations of Fe2+/3+ and oxygen vacancies exerted varying effects on the energy band structure and optical properties of the doped system. The static dielectric constant of all doping systems increased, and the absorption band edge was red-shifted, which helped improve the photocatalytic activity of SnO2.

Deciphering the biodegradation of petroleum hydrocarbons using FTIR spectroscopy: application to a contaminated site.

The chemical composition of groundwater in a petroleum-contaminated site is determined by the present functional groups and these play a vital role in a feasibility remediation technique. Based on the in situ investigation of a contaminated shallow groundwater in an oilfield, Fourier transform infrared (FTIR) spectroscopy associated with chemometric treatments, principal component analysis (PCA), and simple-to-use interactive self-modeling mixture analysis (SIMPLISMA), were used to decipher the biodegradation process by analyzing the conversion of functional groups. Environmental factors that can influence microbial metabolism were also evaluated for a comprehensive explanation. FTIR spectroscopy and PCA results showed that the contamination in the study area can be divided into three parts based on FTIR spectra: (1) regular contamination plume distribution and biodegradation level to fresh oil, (2) moderate biodegradation area, and (3) intensive biodegradation area. FTIR spectra further revealed the present functional groups as aliphatic, aromatic, and polar family compounds. SIMPLISMA was used to discuss the degree of biodegradation along the flow path quantitatively and qualitatively and elucidated that the aliphatic and aromatic compounds were mainly metabolized into polar compounds with nitrogen, sulfur, and oxygen via microbes. During metabolism, microbial indices, such as the Shannon-Weaver, Simpson, and Pielou indices, indicated that microbial diversity did not greatly change; hence, hydrocarbons were constantly consumed to feed dominant microbes. Dissolved oxygen concentrations decreased from 4.58 ± 0.31 mg/L (in monitoring well Z1) to 3.21 ± 0.26 mg/L (in monitoring well Z16) and then became constant in the down-gradient area, demonstrating that aerobic biodegradation was the dominant process at the up-gradient plume. Results were in accordance with the oxidation index, which continuously increased from 0.028 ± 0.013 (in monitoring well Z1) to 0.669 ± 0.047 (in monitoring well Z10), showing that oxygen was consumed along the flow path. Similarly, concentration changes in Fe2+, Mn2+, and SO4 2- proved that the down-gradient area was in reduction condition.

Effect of controlled crystallization on polaronic transport in phosphate‐based glass‐ceramics

AbstractThe effect of induced crystallization on changes in electrical transport of two types of glass‐ceramics, pure polaron conductive 40Fe2O3‐60P2O5 (F40) (mol%) and predominantly polaronic 5Li2O‐5ZnO‐40P2O5‐50WO3 (Li‐50W) (mol%) was investigated. F40 glass‐ceramics produced at low heat‐treatment temperatures contain single‐phase Fe3(P2O7)2 whereas at higher temperatures two more phases Fe4(P2O7)3 and Fe(PO3)3 are formed. Structural modifications strongly depend on the crystallization temperature and time. The appearance of crystalline phases studied by Mössbauer spectroscopy exhibits changes in Fe2+/Fetot ratio in crystalline/glassy phases. The detailed analysis of different iron sites allows their correlation with changes in electrical conductivity as crystallization progresses. Depending on the course of crystallization, the contribution of each phase to the overall conductivity is determined by the frequency dependence of Zʺ(ω) and Mʺ(ω). DC conductivity shows a sharp decrease as Fe3(P2O7)2 phase appears and consequently glass matrix remains impoverished in Fe2+‐Fe3+ pairs. In the multiphase systems prepared at higher crystallization temperatures, the overall electrical conductivity increases although the continuous grain boundaries along different crystalline grains play a limiting factor. In contrast, the slight conductivity change in Li‐50W glass‐ceramics upon crystallization is a result of remaining W5+‐W6+ pairs in the residual glassy phase. Independence of electrical transport on Li+ ions confirms predominantly polaronic transport in Li‐50W glass‐ceramics.

How Does Fault-Related Alteration of Basalt Affect the Potential for Geological Carbon Sequestration in Basalt Formations?

Basalt is an increasingly attractive target for CO2 storage via mineral trapping, due to its abundance of reactive divalent cations such as Ca2+, Mg2+ and Fe2+. The majority of previous studies into the potential for CO2 storage in basalts have used fresh basalt samples. However, it has generally been beyond of the scope of existing studies to look at the effects of faulted and altered basalt at depth, which might have an effect on CO2 storage estimates, especially in geologically older basalt volumes. In this study, two mugearite basalt samples were collected to assess potential for CO2 reactions: a fresh basalt, and its faulted equivalent (altered by fault-related fluids). The faulted equivalent contains less olivine and clinopyroxene compared with its fresh counterpart, due to fluids altering them to clay minerals during and after faulting. Two batch experiments were conducted in synthetic aquifer water (brine) at 50C and PCO2= 130 bar with the aim of investigating potential change in basalt composition and/or concentration of the brine caused by chemical reactions between the basalt rocks and CO2-saturated brine. After 30 days of reaction, Fe2+, Ca2+, Si4- , Al3+ and Mg2+ were leached from the fresh basalt sample showing a potential dissolution of reactive minerals such as olivine and clinopyroxene minerals from the original sample. In contrast, no changes of Fe2+ concentration were observed in experiments performed for faulted basalt. The increase of Fe2+, Ca2+, Si4- , Al3+ and Mg2+ concentration was higher in the fresh basalt experiment compared with the faulted basalt sample. This is most likely due to less reactive minerals available within the faulted sample, such as olivine and pyroxene, having been partially or completely replaced by clay minerals following faulting. Our study therefore finds that faulted and altered basalt is in general less reactive to CO2 than fresh basalt, and this may have implications for the storage of CO2 via mineral trapping in basalts in geologically old and faulted basalt volumes. If basalt volumes targeted for CO2 storage in the future contain geological faults, bulk estimates for mineral trapping of CO2 should take into account the possibility of a difference in reaction rates across the rock volume, and complete additional lab studies to quantify any difference.

The roles of two O-donor ligands in the Fe2+-binding and H2O2-sensing by the Fe2+-dependent H2O2 sensor PerR

PerR is a metal-dependent peroxide sensing transcription factor which controls the expression of genes involved in peroxide resistance. The function of Bacillus subtilis PerR is mainly dictated by the regulatory metal ion (Fe2+ or Mn2+) coordinated by three N-donor ligands (His37, His91, and His93) and two O-donor ligands (Asp85 and Asp104). While H2O2 sensing by PerR is mediated by Fe2+-dependent oxidation of N-donor ligand (either His37 or His91), one of the O-donor ligands (Asp104), but not Asp85, has been proposed as the key residue that regulates the sensitivity of PerR to H2O2. Here we systematically investigated the relative roles of two O-donor ligands of PerR in metal-binding affinity and H2O2 sensitivity in vivo and in vitro. Consistent with the previous report, in vitro the D104E-PerR could not sense low levels of H2O2 in the presence of excess Fe2+ sufficient for the formation of the Fe2+-bound D104E-PerR. However, the expression of PerR-regulated reporter fusion was not repressed by D104E-PerR in the presence of Fe2+, suggesting that Fe2+ is not an effective corepressor for this mutant protein in vivo. Furthermore, in vitro metal titration assays indicate that D104E-PerR has a significantly reduced affinity for Fe2+, but not for Mn2+, when compared to wild type PerR. These data indicate that the type of O-donor ligand (Asp vs. Glu) at position 104 is an important determinant in providing high Fe2+-binding affinity required for the sensing of the physiologically relevant Fe2+-levels, in addition to its role in rendering PerR highly sensitive to physiological levels of H2O2. In comparison, the D85E-PerR did not show a perturbed change in Fe2+-binding affinity, however, it displayed a slightly decreased sensitivity to H2O2 both in vivo and in vitro, suggesting that the type of O-donor ligand (Asp vs. Glu) at position 85 may be important for the fine-tuning of H2O2 sensitivity.

Spin crossovers in iron-bearing MgSiO3 and MgGeO3: Their influence on the post-perovskite transition

MgGeO3-perovskite is known to be a low-pressure analog of MgSiO3-perovskite in many respects, but especially in regard to the post-perovskite transition. As such, investigation of spin state changes in Fe-bearing MgGeO3 might help to clarify some aspects of this type of state change in Fe-bearing MgSiO3. Using DFT+U calculations, we have investigated pressure induced spin state changes in Fe2+ and Fe3+ in MgGeO3 perovskite and post-perovskite. Owing to the larger ionic radius of germanium compared to silicon, germanate phases have larger unit cell volume and inter-atomic distances than equivalent silicate phases at same pressures. As a result, all pressure induced state changes in iron occur at higher pressures in germanate phases than in the silicate ones, be it a spin state change or position change of (ferrous) iron in the perovskite A site. We showed that iron state transitions occur at particular average Fe–O bond-length (i.e., ∼2.22(1)Å and ∼1.86(1)Å for Fe2+ and Fe3+ substitutions, respectively) irrespective of mineral composition (silicate or germanate) or exchange–correlation functionals used in the calculation (LDA+Usc or GGA+Usc). Ferrous iron substitution decreases the perovskite to post-perovskite (PPv) transition pressure while coupled ferric iron substitution increases it noticeably.

XANES Investigation of Dynamic Phase Transition in Olivine Cathode for Li‐Ion Batteries

Dynamic phase transformation in olivine LiFePO4 involving formation of one or more intermediate or metastable phases is revealed by an in situ time‐resolved X‐ray absorption near edge structure (XANES) technique. The XANES spectra measured during relaxation immediately after the application of relatively high overpotentials, where metastable phases are expected, show a continuous shift of the Fe K‐edge toward higher energy. Surprisingly, the Fe K‐edge relaxes to higher energies after current interrupt regardless of whether the cell is being charged or discharged. This relaxation phenomenon is superimposed upon larger shifts in K‐edge due to changes in Fe2+/Fe3+ ratio due to charging and discharging, and implies an intermediate phase of larger FeO bond length than any of the known crystalline phases. No intermediate crystalline phases are observed by X‐ray diffraction (XRD). A metastable amorphous phase formed during dynamic cycling and which structurally relaxes to the equilibrium crystalline phases over a time scale of about 10 min after cessation of charging/discharging current is consistent with the experimental observations.

Time-dependent changes in cerebrospinal fluid metal ions following aneurysm subarachnoid hemorrhage and their association with cerebral vasospasm.

Aneurysm subarachnoid hemorrhage affects 10 in 100,000 people annually, 40 % of whom will develop neurological deficits from ischemic stroke caused by cerebral vasospasm. Currently, the underlying mechanisms are uncertain. Metal ions are important modulators of neuronal electrophysiological conduction and smooth muscle cell activity, thereby potentially contributing to vasospasm. We hypothesized that metal ion concentrations in the cerebrospinal fluid (CSF) after aneurysm rupture would change over time and be associated with vasospasm. To test this hypothesis, for 21 days, we collected CSF from patients with aneurysmal rupture and subjected it to spectrometry to detect metals. A repeated measures analysis was performed to analyze concentration changes over time. Six of the seven patients with aneurysmal rupture experienced vasospasm, all resolving by day 14. Changes in Fe²⁺ and Zn²⁺ concentrations in the CSF paralleled the incidence of vasospasm in this study population. Na²⁺, Ca²⁺, Mg²⁺, and Cu²⁺ concentrations exhibited no statistically significant changes over time. In conclusion, Fe²⁺ concentration in the CSF was significantly elevated during days 7-10, whereas Zn²⁺ concentrations spiked shortly thereafter, during days 11-14. This suggests that Fe²⁺ may be related to the induction of vasospasm and Zn²⁺ may be a marker of early brain injury secondary to ischemic injury and inflammation.

Design, synthesis and cellular dynamics studies in membranes of a new coumarin-based “turn-off” fluorescent probe selective for Fe2+

A new coumarin-based ‘turn-off’ fluorescent probe, 7-(diethylamino)-N-(1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl)-2-oxo-2H-chromene-3-carboxamide (AGD) was synthesized. This compound is highly selective for ferrous ions (Fe2+) and can reversibly detect them in aqueous medium. The probe localizes to the cell membrane in living cells, where it can detect changes in Fe2+ concentration. Molecular dynamics (MD) simulations indicate that AGD interacts with the lipid bilayer at the level of the glycerol moieties.

Mössbauer Spectroscopic and Chromaticity Analysis on the Colourative Mechanism of Ancient Goryeo Celadon from GangJin and Buan

In ancient Goryeo celadon excavated from the kiln sites in the GangJin and Buan areas, the effect of the chemical composition and ionic state of Fe on the colour was evaluated by Mössbauer spectroscopy and chromaticity analysis. According to chromaticity analysis, the L* value (brightness) of the glaze was shown to be affected more by TiO2 and MnO than by Fe2O3, and the body was affected more by Fe2O3 than by TiO2. The a* value was found to be affected by Fe2O3 and TiO2 in the glaze, whereas there was hardly any change in the body according to the composition. As for the b* value, changes due to the composition were shown to be smaller than those for the L* and a* values. According to the Mössbauer spectroscopy results, as the quantities of TiO2 and Fe2O3 are increased, Fe2+/Fe3+ decreases; while the changes in Fe2+/Fe3+ with MnO and P2O5 are negligible. As the quantity of Fe2+/Fe3+ increases, the a* and b* values decrease, which results in the change of colour from red–yellow to blue–green. The characteristic green colour can be attributed to increased L* (brightness) and decreased a* and b* values (blue–green shift) due to the reduced Fe ion, which is mainly determined by the TiO2 and Fe2O3 contents.

Distribution of Fe(II) Concentration during Degradation of Rhodamine B by Fenton Reagent

The effects of reaction conditions including Fe2+, H2O2, oxalic acid, and humic acid dosages were discussed on the Fenton degradation of rhodamine B (RB). The optimal reaction conditions of Fenton reaction were 0.15 mM Fe2+, 5 mM H2O2, and pH 3.0, and the decolorization rate RB (10 mg/L) reached 97.8% after 30min catalytic degradation. The changes of Fe2+concentrations in Fenton system has been focused on in this work. A relatively low concentration of Fe2+was maintained during reaction process when Fe2+and H2O2were added with high concentration, and thus RB was degraded quickly. The results implicated that Fe2+dosage played a very important role in the degradation of RB, and H2O2dosage didn’t have an apparent influence on the degradation of RB in general. The Fenton degradation of RB could be inhibited in the presence of oxalic acid and humic acid, especially at a high concentration of oxalic acid and humic acid.

Electronic structure and properties of (Fe 1− xNi x) 4N (0≤ x≤1.0)

The electronic structure, magnetic moment, elastic and ductile properties of the nitride (Fe 1− x Ni x ) 4N with x from 0.00 to 1.00 were investigated by first-principles calculations within generalized gradient approximation (GGA). The calculated results indicate that the substitution of Ni for Fe in the (Fe 1− x Ni x ) 4N nitride leads to the shrinkage of the lattice parameters and the decrease of the stability of this nitride with increasing x value from 0.00 to 1.00. The alloying ability of Ni to the nitride decreases with Ni content. In comparison with N–Fe covalent bond, the N–Ni covalent bond is weaker and can be also strengthened with Ni content in the nitride. The interactions between Fe2 (at face-centered site) and Ni1 (at corner site) atoms, between Ni1 and Ni2 (at face-centered site) atoms are bonding effect. However, the interactions between Fe2 and Fe2 atoms, between Fe2 and Ni2 atoms, between Ni2 and Ni2 atoms are anti-bonding effect and their bonding strengths depend on the Ni content in the nitride. The magnetic moments (MM) of (Fe 1− x Ni x ) 4N and Ni2 atom decrease with the increase of Ni content, and the MM change of Fe2 and Ni1 atoms is opposite to that of Ni2 atom. Generally, the substitution of Ni for Fe improves the elastic properties and reduces the ductility for the (Fe 1− x Ni x ) 4N nitride.