Addition Of Iron Ions Research Articles

Dual-mode strategy for glyphosate detection: Leveraging competitive interaction with iron and zinc-organic frameworks

The extensive use of glyphosate poses a potential threat to food safety, human health, and the ecological environment. Hence, detecting glyphosate residues in food is of great significance for food safety. In this work, the synthesis of zinc-organic frameworks (Zn-MOFs) was achieved through the coordination of Zn2+ with the 2,5-dihydroxyterephthalic acid (DOBDC) ligand. Upon excitation at 350 nm, these Zn-MOFs exhibited robust fluorescence emission at 533 nm. However, upon the addition of iron ions, the Zn-MOFs structure disintegrated, forming a blue Fe-DOBDC complex, resulting in fluorescence quenching. In the presence of glyphosate, the iron ions were chelated by glyphosate, causing the system to lighten in color and restore fluorescence. Further, the mechanism of this strategy was investigated, which was achieved by utilizing the competitive interaction of glyphosate and Zn-MOFs for iron ions. The binding stoichiometry and binding constant of glyphosate:Fe3+ are 1:1 and 7.59 × 103 M−1 using the Job's plot and Benesi-Hildebrand equation, respectively. To enhance glyphosate detection, this study introduced an ingenious dual-mode strategy. By analyzing the colorimetric and fluorescence changes before and after glyphosate addition, we can accurately determine its concentration in the system. The combined colorimetric and fluorescent modalities offer improved reliability and applicability, boasting simplicity, rapidity, and cost-effectiveness. This innovative method is anticipated to find widespread applications and offers novel perspectives on pesticide detection platforms based on ligand competition effects.

Design and Optimization of Iron-Based Superionic-Like Conductor Anode for High-Performance Lithium/Sodium-Ion Batteries.

Metal selenides have received extensive research attention as anode materials for batteries due to their high theoretical capacity. However, their significant volume expansion and slow ion migration rate result in poor cycling stability and suboptimal rate performance. To address these issues, the present work utilized multivalent iron ions to construct fast pathways similar to superionic conductors (Fe-SSC) and introduced corresponding selenium vacancies to enhance its performance. Based on first-principles calculations and molecular dynamics simulations, it is demonstrated that the addition of iron ions and the presence of selenium vacancies reduced the material's work function and adsorption energy, lowered migration barriers, and enhances the migration rate of Li+ and Na+. In Li-ion half batteries, this composite material exhibites reversible capacity of 1048.3 mAh g-1 at 0.1 A g-1 after 100 cycles and 483.6 mAh g-1 at 5.0 A g-1 after 1000 cycles. In Na-ion half batteries, it is 687.7 mAh g-1 at 0.1 A g-1 after 200 cycles and 325.9 mAh g-1 at 5.0 A g-1 after 1000 cycles. It is proven that materials based on Fe-SSC and selenium vacancies have great applications in both Li-ion batteries and Na-ion batteries.

Boosted photo-self-Fenton degradation activity by Fe-doped carbon dots as dual-function active sites for in-situ H2O2 generation and activation

Photo-Fenton process is acknowledged for its high efficiency and technical feasibility in water treatment; however, its application is constrained by the addition of iron ions and hydrogen peroxide (H2O2). Herein, an efficient photo-self-Fenton system with coating Fe-doped carbon dots (Fe-CDs) on the surface of highly crystalline C3N5 (HC-C3N5) nanosheets was developed for degradation of tetracycline (TC) under visible light irradiation. Experimental results reveal that Fe-CDs not only serve as active sites for facilitating superior light-induced charge separation and transfer towards the in-situ generation of H2O2 over HC-C3N5, but also provide the solid-phase Fe species for maximizing the activation of in-situ generated H2O2 to produce highly oxidative OH and O2– species towards the photo-self-Fenton reaction. This research presents a novel design approach of utilizing a Fe-CDs-based photo-self-Fenton system for efficient wastewater treatment.

Iron ions regulate antifungal HSAF biosynthesis in Lysobacter enzymogenes by manipulating the DNA-binding affinity of the ferric uptake regulator (Fur).

Heat-stable antifungal factor (HSAF), produced by Lysobacter enzymogenes OH11, is regarded as a potential biological pesticide due to its broad-spectrum antifungal activity and novel mode of action. However, the current production of HSAF is low and cannot meet the requirements for large-scale production. Herein, we discovered that iron ions greatly promoted HSAF production, and the ferric uptake regulator (Fur) was involved in this regulatory process. Fur was also found to participate in the regulation of iron homeostasis in OH11 via the classic inhibition mechanism of Holo-Fur. Furthermore, Fur was collectively observed to directly bind to the promoter of the HSAF biosynthesis gene, and its DNA-binding affinity was attenuated by the addition of iron ions in vitro and in vivo. Its regulatory mechanism followed the uncommon inhibition mechanism of Apo-Fur. In summary, Fur exhibited a bidirectional regulatory mechanism in OH11. This study reveals a novel regulatory mechanism whereby Fur upregulates the biosynthesis of secondary metabolites. These findings contribute to the improvement of HSAF production and may guide its development into biological pesticides. IMPORTANCE HSAF possesses potent and broad antifungal activity with a novel mode of action. The HSAF yield is critical for fermentation production. In this study, iron ions were found to increase HSAF production, and the specific mechanism was elaborated. These results provide theoretical support for genetic transformation to improve HSAF yield, supporting its development into biological pesticides.

Ultra-Low Loading of Iron Oxide and Platinum on CVD-Graphene Composites as Effective Electrode Catalysts for Solid Acid Fuel Cells

We propose a new design for electrocatalysts consisting of two electrocatalysts (platinum and iron oxide) that are deposited on the surfaces of an oxidized graphene substrate. This design is based on a simple structure where the catalysts were deposited separately on both sides of oxidized graphene substrate; while the iron oxide precipitated out of the etching solution on the bottom-side, the surface of the oxidized graphene substrate was decorated with platinum using the atomic layer deposition technique. The Fe2O3-decorated CVD-graphene composite exhibited better hydrogen electrooxidation performance (area-normalized electrode resistance (ANR) of ~600 Ω·cm−2) and superior stability in comparison with bare-graphene samples (ANR of ~5800 Ω·cm−2). Electrochemical impedance measurements in humidified hydrogen at 240 °C for (Fe2O3|Graphene|Platinum) electrodes show ANR of ~0.06 Ω·cm−2 for a platinum loading of ~60 µgPt·cm−2 and Fe2O3 loading of ~2.4 µgFe·cm−2, resulting in an outstanding mass normalized activity of almost 280 S·mgPt−1, exceeding even state-of-the-art electrodes. This ANR value is ~30% lower than the charge transfer resistance of the same electrode composition in the absence of Fe2O3 nanoparticles. Detailed study of the Fe2O3 electrocatalytic properties reveals a significant improvement in the electrode’s activity and performance stability with the addition of iron ions to the platinum-decorated oxidized graphene cathodes, indicating that these hybrid (Fe2O3|Graphene|Platinum) materials may serve as highly efficient catalysts for solid acid fuel cells and beyond.

Efficient degradation of chromium picolinate with simultaneous chromium removal from aqueous solutions using the Fenton process

Chromium picolinate (Cr(pic)3) is widely used for feeding animals. Most Cr(pic)3 administered to animals is excreted without change. The land use of animal waste introduces Cr(pic)3 to the environment. Transformation of Cr(pic)3 in the environment releases hexavalent chromium (Cr(VI)), posing a chromium contamination risk. Because chromium (in trivalent valent) is complexed by picolinic acid (pic), removal of chromium in Cr(pic)3 form via direct adsorption and precipitation methods is rather difficult. Release of chromium from Cr(pic)3 first and then removal of it through the combination of adsorption and precipitation is advisable. To this end, the treatment of Cr(pic)3 using the Fenton process was first investigated in this work. Treatment parameters were optimized for Cr(pic)3 degradation and chromium removal (i.e., initial and final pH of 3.0 and 7.0, and the molar ratio of Fe(II) and H2O2 was 1:2). Adverse effects of the water constituents could be mitigated by flexible adjustment of the Fenton reagent dosages and the external addition of iron ions. The residual chromium in the aqueous phase was simultaneously lowered to the required standard, and Cr(VI) was barely detected in the aqueous phase. Mechanisms of Cr(pic)3 degradation and chromium removal were proposed by the intermediates determined. The results obtained indicate that the Fenton process is robust for degrading Cr(pic)3 and removing chromium simultaneously and is promising for treating Cr(pic)3-containing wastewater.

Comparative characteristics of oxidative modification intensity of proteins in infant milk formulas

Cow's milk is mainly used in the production of infant milk formulas. However, the protein composition of cow's milk differs significantly from the proteome of breast milk. In addition, various technological factors significantly affect the properties and structure of proteins, susceptibility to oxidative processes. This article uses a method of complex evaluation of the products of oxidative modification of proteins to characterize the total level of carbonyl compounds with the analysis of the ratio of aldehyde-dinitrophenylhydrazones (ADNPH) and ketone-dinitrophenylhydrazones (CDNPH), which increases the possibility of determining the severity of protein damage. The purpose of the study was to compare the level of indicators of oxidative modification of proteins in adapted milk infant formulas. Material and methods. The research objects were 4 dry adapted milk infant formulas, as well as ultra-pasteurized cow's milk. The intensity of oxidative modification of milk proteins was determined spectrophotometrically by the reaction of carbonyl compounds with dinitrophenylhydrazine (DNFG). Results. With spontaneous oxidation in infant formula, the total area of carbonyl derivatives of proteins (Sомб) was increased compared to the indicators of ultra-pasteurized cow's milk. The greatest change occurred in relation to ADNFG indicators (SАДНФГ), the level of which increased in 3 formulas by 48.6-59.4%. The content of ketone derivatives (SКДНФГ) did not differ significantly in the studied mixtures from milk indicators. The level of carbonyl derivatives of proteins in milk infant formulas was even more elevated during the induction of oxidation by the addition of iron ions and hydrogen peroxide to the incubation medium. The content of both total and various fractions of carbonyl compounds exceeded the corresponding indicators of cow's milk by 2.0-2.6 times. Conclusion. The results of the study indicate a greater susceptibility to oxidative damage of proteins in milk infant formulas, compared with cow's milk.

(Digital Presentation) Effect of Iron Doping on Oxygen Reduction Activity of Zirconium Oxides Containing Carbon and Nitrogen Using Pyrazine Carboxylic Acid As Platinum Alternative Cathodes for PEFC

The use of carbon-supported platinum catalysts as cathode of present polymer electrolyte fuel cells (PEFCs) have some problems such as high cost and low amount of resources of platinum. Therefore, we have attempted to develop substitute of platinum based on group 4 transition metal oxides. We found that stable oxygen vacancies on the surface and lattice distortion by doping foreign elements of these metal oxides could act as active sites of oxygen reduction reaction (ORR) [1]. However, although zirconium oxides show some ORR activity, the onset potential of the ORR still remains low. Then, we focused on the improvement of the ORR activity by an addition of iron ions to zirconium oxides according to the research of P. Madkikar et. al. [2]. In this study, we used pyrazine carboxylic acid as ligand of metal ions to prepare zirconium-iron complexes including carbon and nitrogen as precursors. The precursors were heat-treated under low oxygen pressure to obtain the iron-added zirconium oxide-based catalysts, which are designated as ZrOx-Fe. We investigated the correlation between the ORR activity and physical characteristics such as crystalline phase.ZrOx-Fe catalysts were synthesized according to the previous patent [3]. We prepared zirconium complexes solutions by mixing zirconium butoxide and acetic acid in acetylacetone as a solvent. On the other hand, we also prepared iron complexes solutions by mixing iron acetic acid and pyrazine carboxylic acid in mixed solvents of water, ethanol and acetic acid. The amount of the iron addition was changed in atomic ratios of 0, 0.004, 0.01, 0.1, and 0.2 against Zr atoms. The iron atomic ratio of 0.004 was selected according to P. Madkikar’s results, because Fe atomic ratio of 0.0036 caused the highest ORR activity in the report [2]. After mixing of two solutions, the solutions were stirring several days, and the precursors were obtained by evaporation and vacuum drying. These precursors were heat-treated under argon including 2 % hydrogen and 0.05 % oxygen for low oxygen pressure oxidation, and finally ZrOx-Fe catalysts were obtained. To investigate the effect of Fe addition to zirconium oxides, we also synthesized iron-based catalyst without Zr in the same way. Electrochemical measurements were conducted in the solution of 0.5 M H2SO4 at 30 oC. In this study, we used the ORR onset potential as the parameter of the ORR activity, which was defined as the potential when the ORR current (i ORR) was 0.01 ampere per a mass of the whole catalysts.Among the ZrOx-Fe catalysts prepared in this study, ZrOx-Fe with the Fe atomic ratio of 0.1 showed the highest E ORR, which was designated as ZrOx-Fe(0.1). Therefore, we compared with ZrOx and FeOx prepared by the same way as well as conventional catalysts. Fig. 1 shows the ORR polarization curves of the ZrOx, ZrOx / CNT [1], ZrOx-Fe / KB [2], FeOx and ZrOx-Fe(0.1) catalysts. As shown in Fig.1, the ZrOx-Fe(0.1) catalyst had highest ORR onset potential among these catalysts. Comparing with ZrOx, FeOx and ZrOx-Fe(0.1), the Fe addition into zirconium oxide was essential to increase the ORR onset potential. In addition, the onset potential of the ZrOx-Fe(0.1) was higher than that of the ZrOx-Fe / KB [2] and our previous ZrOx / CNT [1]. The onset potential of the ZrOx-Fe(0.1) was exceeded 0.9 V that we have never been able to reach with zirconium oxides. Therefore, the addition of iron to zirconium oxides improved drastically the quality of the active sites of the ORR.Next, we examined crystalline phase of all ZrOx-Fe catalysts with XRD. All ZrOx-Fe catalysts were consisted of ZrO2 monoclinic or tetragonal phase. We calculated monoclinic rate in each catalyst using the equation in the literature [4]. The change of atomic ratio of Fe caused the different monoclinic rate. A positive correlation between the ORR onset potentials and the monoclinic rates of the ZrOx-Fe was obtained. Thus, the ORR onset potential increased with increasing the monoclinic rate in the catalysts, suggesting that the monoclinic phase formed the active sites of the ORR.AcknowledgementThe authors thank the financial support of the New Energy and Industrial Technology Development Organization (NEDO), JSPS grants-in-aid for scientific research, and ENEOS Tonen General Sekiyu Research / Development Encouragement & Scholarship Foundation.References(1) A. Ishihara et. al., Int. J. Hydro. Energy, 45, 5438 (2019).(2) P. Madkikar et. al., J. Electrochem. Soc., 166, F3032 (2019).(3) Showa Denko Corp., R. Monden et. al., Oxygen reduction catalysts, the methods of these, and polymer electrolyte fuel cells, JP 2013-240785, 2013-12-05.(4) H. Toraya et. al., J. Am. Ceram. Soc., 67, C119 (1984). Figure 1

A Novel Fluorescent Probe Based on Pyrazole-Pyrazoline for Fe (III) Ions Recognition.

Firstly, a novel pyrazole-pyrazoline fluorescent probe was developed and synthesized. The probe can be used to determine Fe3+ ions in a series of cations in tetrahydrofuran aqueous solution with high selectivity and high sensitivity. After the addition of iron ions, the fluorescence intensity is significantly reduced, Its structure was characterized by 1H NMR, 13C NMR and HR-ESI-MS. UV absorption spectra and Fluorescence spectroscopy were used to study the selective recognition of probe M on metal ions. The probe M can selectivity and sensitivity to distinguish the target ion from other ions through different fluorescence phenomena. In addition, the binding modes of M with Fe3+ were proved to be 1:1 stoichiometry in the complexes by Job's plot, IR results. The combination of probe M and iron ions is 1:1, and the detection limit is 3.9 × 10-10 M. The binding mode and sensing mechanism of M with Fe3+ was verified by theoretical calculations using Gaussian 09 based on B3LYP/6-31G(d) basis.

Novel multi-functional Pr3+:Bi12SiO20 luminescent nano-sensor for latent human prints, iron ions in drinking water and anti-counterfeiting application

Pure and metal-doped bismuth silicate matrix (Bi12SiO20) were prepared in bulk scale and studied from the electrical, crystal and optical properties point of view. Production of Nano-praseodymium doped bismuth silicate and its potential applications as a photoluminescent sensor in forensic science, heavy metal detection as well as in anti-counterfeiting ink applications have not been reported in the literature to now. Herein, a novel, simple, sensitive and multi-functional photoluminescent Nano-sensor based on x mol Pr3+:Bi12SiO20 (Pr:BS) (x = 0.015, 0.030 and 0.100 mol) was prepared and characterized for latent prints and iron ion detection and anti-counterfeiting ink applications. High crystallinity and Nano-domain of partly connected spherical particles for Pr:BS have been confirmed from XRD and TEM analysis, respectively. Pr:BS Nano-sensor emits a strong and pure pinkish red color which appears to the human eye upon un-harmful UVA excitation resource. Lifetime values; either in solid state or aqueous solutions were measured. Pr:BS Nano-sensor has successfully visualized latent print from various forensic non-porous and porous surfaces. Pr:BS Nano-sensor was used to develop luminescent ink for anti-counterfeiting application. The sensing results revealed that Pr:BS Nano-sensor detects the iron ion from aqueous solution with fast response time and high selectivity if compared to other metal ions. The assessment of iron ion depends on PBS photoluminescence quenching upon the addition of iron ion. Stern-Volmer plot was achieved over the concentration 0.00–17 × 10−5 mol L−1 with a correlation coefficient of 0.996 and a detection limit of 1.56 × 10−5 mol L−1. The sensing mechanism was discussed in detail. Optimized 0.015 mol Pr:BS Nano-sensor was applied for iron detection in real drinking water samples with high recovery value.

Activated Carbon as a Cathode for Water Disinfection through the Electro-Fenton Process.

Unlike many other water disinfection methods, hydroxyl radicals (HO•) produced by the Fenton reaction (Fe2+/H2O2) can inactivate pathogens regardless of taxonomic identity of genetic potential and do not generate halogenated disinfection by-products. Hydrogen peroxide (H2O2) required for the process is typically electrogenerated using various carbonaceous materials as cathodes. However, high costs and necessary modifications to the cathodes still present a challenge to large-scale implementation. In this work, we use granular activated carbon (GAC) as a cathode to generate H2O2 for water disinfection through the electro-Fenton process. GAC is a low-cost amorphous carbon with abundant oxygen- and carbon-containing groups that are favored for oxygen reduction into H2O2. Results indicate that H2O2 production at the GAC cathode is higher with more GAC, lower pH, and smaller reactor volume. Through the addition of iron ions, the electrogenerated H2O2 is transformed into HO• that efficiently inactivated model pathogen (Escherichia coli) under various water chemistry conditions. Chick–Watson modeling results further showed the strong lethality of produced HO• from the electro-Fenton process. This inactivation coupled with high H2O2 yield, excellent reusability, and relatively low cost of GAC proves that GAC is a promising cathodic material for large-scale water disinfection.

Combining stiffness and stretchiness

Materials Science There is usually a trade-off between making a material stretchy, so that it can absorb energy on deformation, and making a material stiff, so that it does not extend very much when stretched. Mussels have long been an inspiration for developing adhesives that work when wet. Filippidi et al. produced an extensible polymeric material containing catechol groups whose mechanical properties were augmented when dry through the addition of iron ions (see the Perspective by Winey). The iron ions lead to sacrificial metal coordination bonds, creating a reversible load-bearing network that does not trade extensibility for stiffness. Science , this issue p. [502][1]; see also p. [449][2] [1]: /lookup/doi/10.1126/science.aao0350 [2]: /lookup/doi/10.1126/science.aap8114

Unraveling the genetic basis of xylose consumption in engineered Saccharomyces cerevisiae strains.

The development of biocatalysts capable of fermenting xylose, a five-carbon sugar abundant in lignocellulosic biomass, is a key step to achieve a viable production of second-generation ethanol. In this work, a robust industrial strain of Saccharomyces cerevisiae was modified by the addition of essential genes for pentose metabolism. Subsequently, taken through cycles of adaptive evolution with selection for optimal xylose utilization, strains could efficiently convert xylose to ethanol with a yield of about 0.46 g ethanol/g xylose. Though evolved independently, two strains carried shared mutations: amplification of the xylose isomerase gene and inactivation of ISU1, a gene encoding a scaffold protein involved in the assembly of iron-sulfur clusters. In addition, one of evolved strains carried a mutation in SSK2, a member of MAPKKK signaling pathway. In validation experiments, mutating ISU1 or SSK2 improved the ability to metabolize xylose of yeast cells without adaptive evolution, suggesting that these genes are key players in a regulatory network for xylose fermentation. Furthermore, addition of iron ion to the growth media improved xylose fermentation even by non-evolved cells. Our results provide promising new targets for metabolic engineering of C5-yeasts and point to iron as a potential new additive for improvement of second-generation ethanol production.

Enhancement of embryo yield from isolated microspores of Brassica napus by early iron starvation

Induction of embryogenesis in isolated microspores of Brassica napus requires stress conditions to trigger the developmental instead of the gametophytic pathway. To obtain further insight into the involvement of different ions in this process, a comparison has been made between embryo yields obtained with standard NLN-13 medium and the same medium without cobalt, copper or iron. It was confirmed that iron was essential to control embryo development, but not cobalt and copper. For the latter two ions, the concentration is probably too low to play a significant role in microspore embryogenesis. With the timing of iron application, as well as its chemical form, embryo yield could be improved or reduced. In media that exhibited iron deficiency, microspores initiated embryogenesis and the number of observed divided microspores increased 6 days after isolation. However, embryo development was not achieved. Addition of iron ions chelated with EDTA at day 3, leading to the doubling of embryo yield. Some of the putative role(s) of Fe-EDTA in the early events of embryogenesis is discussed.

Effect of iron ions (Fe2+, Fe3+) on the formation and structure of aerobic granular sludge.

Aerobic granulation is a promising technology for wastewater treatment, but problems regarding its formation and stability need to be solved. Divalent metal ions, especially Ca2+, Mg2+ and Mn2+, have been demonstrated to play an important role in the process of aerobic granulation. Here, we studied whether iron ions can affect aerobic granulation. Granular sludge formed without iron ion addition (<0.02mg Fe2+ L-1) was fluffy and had a finger-type structure and filamentous out-growth. The addition of iron ions to concentrations of 1 and 10mg Fe2+ L-1 repressed the finger-type structure and filamentous out-growth. The results show that chemical precipitation in the granules with iron ion addition was higher than that in the granules without ferrous addition. The amount of precipitates was higher inside the granules than outside. This study demonstrates that iron ions (Fe2+/Fe3+) increase the size and stability of aerobic granular sludge but do not affect the granulation time, which is the time that the first granular sludge is observed. The study shows that aerobic granular sludge technology can be confidently applied to actual wastewater containing a high concentration of iron compounds.

Formation initiation and structural changes of phosphate conversion coating on titanium induced by galvanic coupling and Fe2+ ions

A scholzite coating was precipitated on Ti by a galvanically coupled approach and addition of iron ions in the bath.

Stability of hydroxycinnamic acids and caffeine from green coffee extracts after heating in food model systems

This study was designed to characterize the stability of hydroxycinnamic acids and caffeine obtained from green coffee beans in the form of lyophilized extract (GCE) during heating after supplementation to model systems with saccharose, potato starch, egg white protein, and sunflower oil. Also the addition of iron ions was used. Systems were prepared as a mixture of GCE with a single substance or in a more complex matrix. Heating was carried out at 180 °C for 0.5 and 1 h. Because of the saccharose content, some systems were heated only at 110 °C. The losses of hydroxycinnamic acids in heated systems ranged from 18 to 84 %, and the caffeine from 1.5 to 10 %. The presence of sunflower oil in the systems had the greatest influence on hydroxycinnamic acids degradation. However, in case of the system of each of the examined substances with the coffee preparation, an increased degradation of hydroxycinnamic acids resulting from the introduction of ferrous ions into the systems was observed. Earlier results concerning antioxidant activity of systems containing GCE allow to conclude that the degradation of hydroxycinnamic acids was weakly related to the decrease in antioxidant activity.

Influences of sludge retention time on the performance of submerged membrane bioreactors with the addition of iron ion

A bench-scale submerged membrane bioreactor (MBR) treating synthetic wastewater with FeCl3 dose of 15mg/L was operated under different sludge retention times (SRTs), i.e. 10, 20 and 30d, in order to evaluate the impacts of SRT on the performance of MBRs with the addition of FeCl3. The results showed that the effluent quality was slightly influenced by SRT, while membrane fouling was effectively mitigated by lengthening SRT under the condition of FeCl3 adding. The concentration of soluble microbial products (SMP) significantly decreased as SRT extended from 10 to 30d, which correlated well with the variation of membrane fouling. SMP played a more important role in membrane fouling in this study compared to other sludge properties. Fe accumulated in the MBR as SRT prolonged, and the accumulation of Fe enhanced flocculation and resulted in the decrease of MLVSS/MLSS ratio and the increase of particle size. The accumulated Fe in mixed liquor was mainly located in bound extracellular polymeric substances (BEPS). It is suggested that the negatively functional groups such as polysaccharide in SMP were adsorbed by the bridging effects of iron ion, thus leading to the reduction of SMP and increase of BEPS at longer SRT.

Iron chelation with salicylaldehyde isonicotinoyl hydrazone protects against catecholamine autoxidation and cardiotoxicity

Elevated catecholamine levels are known to induce damage of the cardiac tissue. This catecholamine cardiotoxicity may stem from their ability to undergo oxidative conversion to aminochromes and concomitant production of reactive oxygen species (ROS), which damage cardiomyocytes via the iron-catalyzed Fenton-type reaction. This suggests the possibility of cardioprotection by iron chelation. Our in vitro experiments have demonstrated a spontaneous decrease in the concentration of the catecholamines epinephrine and isoprenaline during their 24-h preincubation in buffered solution as well as their gradual conversion to oxidation products. These changes were significantly augmented by addition of iron ions and reduced by the iron-chelating agent salicylaldehyde isonicotinoyl hydrazone (SIH). Oxidized catecholamines were shown to form complexes with iron that had significant redox activity, which could be suppressed by SIH. Experiments using the H9c2 cardiomyoblast cell line revealed higher cytotoxicity of oxidized catecholamines than of the parent compounds, apparently through the induction of caspase-independent cell death, whereas co-incubation of cells with SIH was able to significantly preserve cell viability. A significant increase in intracellular ROS formation was observed after the incubation of cells with catecholamine oxidation products; this could be significantly reduced by SIH. In contrast, parent catecholamines did not increase, but rather decreased, cellular ROS production. Hence, our results demonstrate an important role for redox-active iron in catecholamine autoxidation and subsequent toxicity. The iron chelator SIH has shown considerable potential to protect cardiac cells by both inhibition of deleterious catecholamine oxidation to reactive intermediates and prevention of ROS-mediated cardiotoxicity.

Aqueous 4-nitrophenol decomposition and hydrogen peroxide formation induced by contact glow discharge electrolysis

Liquid-phase decomposition of 4-nitrophenol (4-NP) and formation of hydrogen peroxide (H 2O 2) induced by contact glow discharge electrolysis (CGDE) were investigated. Experimental results showed that the decays of 4-NP and total organic carbon (TOC) obeyed the first-order and pseudo-first-order reaction kinetics, respectively. The major intermediate products were 4-nitrocatechol, hydroquinone, benzoquinone, hydroxyhydroquinone, organic acids and nitrite ion. The final products were carbon dioxide and nitrate ion. The initial formation rate of H 2O 2 decreased linearly with increasing initial concentration of 4-NP. Addition of iron ions, especially ferric ion, to the solution significantly enhanced the 4-NP removal due to the additional hydroxyl radical formation through Fenton's reaction. A reaction pathway is proposed based on the degradation kinetics and the distribution of intermediate products.