Showing papers on "Ferric published in 2018"

Removal of Organoarsenic with Ferrate and Ferrate Resultant Nanoparticles: Oxidation and Adsorption.

Abstract: Many investigations focused on the capacity of ferrate for the oxidation of organic pollutant or adsorption of hazardous species, while little attention has been paid on the effect of ferrate resultant nanoparticles for the removal of organics. Removing organics could improve microbiological stability of treated water and control the formation of disinfection byproducts in following treatment procedures. Herein, we studied ferrate oxidation of p-arsanilic acid ( p-ASA), an extensively used organoarsenic feed additive. p-ASA was oxidized into As(V), p-aminophenol ( p-AP), and nitarsone in the reaction process. The released As(V) could be eliminated by in situ formed ferric (oxyhydr) oxides through surface adsorption, while p-AP can be further oxidized into 4,4'-(diazene-1,2-diyl) diphenol, p-nitrophenol, and NO3-. Nitarsone is resistant to ferrate oxidation, but mostly adsorbed (>85%) by ferrate resultant ferric (oxyhydr) oxides. Ferrate oxidation (ferrate/ p-ASA = 20:1) eliminated 18% of total organic carbon (TOC), while ferrate resultant particles removed 40% of TOC in the system. TOC removal efficiency is 1.6 to 38 times higher in ferrate treatment group than those in O3, HClO, and permanganate treatment groups. Besides ferrate oxidation, adsorption of organic pollutants with ferrate resultant nanoparticles could also be an effective method for water treatment and environmental remediation.

Hydrophilic mesoporous carbon as iron(III)/(II) electron shuttle for visible light enhanced Fenton-like degradation of organic pollutants

Abstract: A Fenton-like catalyst comprising of hydrophilic mesoporous carbon (HMC) and ferric ions was found very efficiently in degradation organic pollutants under visible light irradiation in the presence of H2O2. HMC with graphene domains and plenty of oxygen containing groups such as carboxyl groups can cooperate with ferric ions to form a visible light active Fe(III)-HMC configuration. Fe(III)-HMC showed obviously enhanced phenol degradation and mineralization efficiencies than that in dark condition. Acidic condition (pH = 3) is not only more superior in phenol degradation but also in iron leaching in comparison with the case at basic conditions (pH = 4.5–7.0) for Fe(III)-HMC. Total organic carbon (TOC) removal efficiency of five typical organic pollutants show that visible light active Fe(III)-HMC catalyst is more efficient than homogeneous Fenton reagents FeSO4/H2O2 excluding the temperature effect. Electron spin resonance (ESR) and electrochemical measurements reveal that the presence of active phenoxyl radicals and ligand to metal charge transfer (LMCT) facilitates the cycling of Fe(III)/Fe(II) and inhibit the side reaction via Haber-Weiss reaction. ·OH radicals rather than O2− and OOH were proved as the predominantly active oxidant. The proposed Fe(III)-HMC configuration activated by visible light opens up a new strategy for carbon based materials and iron species in Fenton-like chemistry.

Carbonate-sensitive phytotransferrin controls high-affinity iron uptake in diatoms

Abstract: In vast areas of the ocean, the scarcity of iron controls the growth and productivity of phytoplankton. Although most dissolved iron in the marine environment is complexed with organic molecules, picomolar amounts of labile inorganic iron species (labile iron) are maintained within the euphotic zone and serve as an important source of iron for eukaryotic phytoplankton and particularly for diatoms. Genome-enabled studies of labile iron utilization by diatoms have previously revealed novel iron-responsive transcripts, including the ferric iron-concentrating protein ISIP2A, but the mechanism behind the acquisition of picomolar labile iron remains unknown. Here we show that ISIP2A is a phytotransferrin that independently and convergently evolved carbonate ion-coordinated ferric iron binding. Deletion of ISIP2A disrupts high-affinity iron uptake in the diatom Phaeodactylum tricornutum, and uptake is restored by complementation with human transferrin. ISIP2A is internalized by endocytosis, and manipulation of the seawater carbonic acid system reveals a second-order dependence on the concentrations of labile iron and carbonate ions. In P. tricornutum, the synergistic interaction of labile iron and carbonate ions occurs at environmentally relevant concentrations, revealing that carbonate availability co-limits iron uptake. Phytotransferrin sequences have a broad taxonomic distribution and are abundant in marine environmental genomic datasets, suggesting that acidification-driven declines in the concentration of seawater carbonate ions will have a negative effect on this globally important eukaryotic iron acquisition mechanism.

The Putative Peptide Gene FEP1 Regulates Iron Deficiency Response in Arabidopsis.

Abstract: Iron is an essential element for all organisms, and plants have developed sophisticated systems to acquire iron and maintain iron homeostasis. We found that an Arabidopsis thaliana ABA-hypersensitive mutant, aba hypersensitive germination2-1 (ahg2-1), that is known to be defective in mitochondrial mRNA regulation, had increased expression of iron deficiency response genes. The ahg2-1 mutant had lower heme levels than the wild type. Transcriptome data further revealed that novel genes encoding short polypeptides were highly expressed in this mutant. The expression of one of these genes, which we named FE-UPTAKE-INDUCING PEPTIDE 1 (FEP1), was induced under iron-deficient conditions and was observed in the vascular tissues of the leaves and roots, as well as in leaf mesophyll cells. Notably, deletion or insertion mutations of FEP1 exhibited impaired iron accumulation in shoots but normal iron levels in roots. Artificially induced expression of FEP1 was sufficient to induce iron deficiency response genes, such as basic HELIX-LOOP-HELIX 38 (bHLH38), bHLH39, IRON-REGULATED TRANSPORTER1 (IRT1) and FERRIC REDUCTION OXIDASE2 (FRO2), and led to iron accumulation in planta. Further analysis confirmed that the encoded peptide, but not the FEP1 RNA, was responsible for this activity. Remarkably, the activation of bHLH39 by FEP1 was independent of FER-LIKE IRON DEFICIENCY INDUCED (FIT), a key transcription factor in the iron deficiency response. Taken together, our results indicate that FEP1 functions in iron homeostasis through a previously undescribed regulatory mechanism for iron acquisition in Arabidopsis.

Red emitting and highly stable carbon dots with dual response to pH values and ferric ions

Abstract: The authors describe strongly red-emitting carbon dots (CDs) which were obtained via microwave synthesis using phenylenediamine as the carbon source. The structural and optical properties of the resultant CDs are studied in some detail. The CDs possess (a) longwave emission (peaking at 620 nm under 470 nm excitation), (b) a quantum yield of ~15%, (c) a size of typically 3.8 nm; and (d) good photostability. The CDs have a pH-dependet response that covers the pH 5 to 10 range, and their fluorescence is quenched by ferric ions. The CDs can detect ferric ions in aqueous samples in the 0 to 30 μM concentration range with a lower detection limit of 15 nM. The CDs were also used to image pH values and ferric ions in E. coli bacteria.

Rational Design of Mononuclear Iron Porphyrins for Facile and Selective 4e–/4H+ O2 Reduction: Activation of O–O Bond by 2nd Sphere Hydrogen Bonding

Abstract: Facile and selective 4e–/4H+ electrochemical reduction of O2 to H2O in aqueous medium has been a sought-after goal for several decades Elegant but synthetically demanding cytochrome c oxidase mimics have demonstrated selective 4e–/4H+ electrochemical O2 reduction to H2O is possible with rate constants as fast as 105 M–1 s–1 under heterogeneous conditions in aqueous media Over the past few years, in situ mechanistic investigations on iron porphyrin complexes adsorbed on electrodes have revealed that the rate and selectivity of this multielectron and multiproton process is governed by the reactivity of a ferric hydroperoxide intermediate The barrier of O—O bond cleavage determines the overall rate of O2 reduction and the site of protonation determines the selectivity In this report, a series of mononuclear iron porphyrin complexes are rationally designed to achieve efficient O—O bond activation and site-selective proton transfer to effect facile and selective electrochemical reduction of O2 to water In

Iron and magnetic: new research direction of the ferroptosis-based cancer therapy.

Abstract: Ferroptosis is an iron depend cell death which caused by lipid peroxidation. Abnormal iron metabolism and high intracellular iron content are the characteristics of most cancer cells. Iron is a promoter of cell growth and proliferation. However, iron also could take part in Fenton reaction to produce reactive oxygen species (ROS). The intercellular ROS could induce lipid peroxidation, which is necessary for ferroptosis. Iron metabolism mainly includes three parts: iron uptake, storage and efflux. Therefore, iron metabolism-related genes could regulate intercellular iron content and status, which can be involved ferroptosis. In recent years, the application of nanoparticles in cancer therapy research has become more and more extensive. The iron-based nanoparticles (iron-based NPs) can release ferrous (Fe2+) or ferric (Fe3+) in acidic lysosomes and inducing ferroptosis. Magnetic field is widely used in the targeted concentration of iron-based NPs related disease therapy. Furthermore, multiple studies showed that magnetic fields can inhibit cancer cell proliferation by promoting intracellular ROS production. Herein, we focus on the relationship of between ferroptosis and iron metabolism in cancer cells, the application of nanoparticles and magnetic field in inducing ferroptosis of cancer cells, and trying to provide new ideas for cancer treatment research.

Remarkably enhanced water splitting activity of nickel foam due to simple immersion in a ferric nitrate solution

Abstract: The development of a facile method to construct a high-performance electrode is of paramount importance to the application of alkaline water electrolysis. Here, we report that the activity of nickel foam (NF) towards the oxygen evolution reaction (OER) can be enhanced remarkably through simple immersion in a ferric nitrate (Fe(NO3)3) solution at room temperature. During this immersion process, the oxidation of the NF surface by NO3− ions increases the near-surface concentrations of OH− and Ni2+, which results in the in situ deposition of a highly active amorphous Ni-Fe hydroxide (a-NiFeOxHy) layer. Specifically, the OER overpotential of the NF electrode decreases from 371 mV (bare NF) to 270 mV (@10 mA·cm−2 in 0.1 M KOH) after immersion in a 20 mM Fe(NO3)3 solution for just 1 min. A longer immersion time results in further increased OER activity (196 mV@10 mA·cm−2 in 1 M KOH). The overall water splitting properties of the a-NiFeOxHy@NF electrode were evaluated using a two-electrode configuration. It is worth noting that the current density can reach 25 mA·cm−2 in 6 M KOH at an applied voltage of 1.5 V at room temperature.

Biochar composites with nano zerovalent iron and eggshell powder for nitrate removal from aqueous solution with coexisting chloride ions

Abstract: Biochar (BC) was produced from date palm tree leaves and its composites were prepared with nano zerovalent iron (nZVI-BC) and hen eggshell powder (EP-BC). The produced BC and its composites were characterized by SEM, XRD, BET, and FTIR for surface structural, mineralogical, and chemical groups and tested for their efficiency for nitrate removal from aqueous solutions in the presence and absence of chloride ions. The incidence of graphene and nano zerovalent iron (Fe0) in the nZVI-BC composite was confirmed by XRD. The nZVI-BC composite possessed highest surface area (220.92 m2 g−1), carbon (80.55%), nitrogen (3.78%), and hydrogen (11.09%) contents compared to other materials. Nitrate sorption data was fitted well to the Langmuir (R 2 = 0.93–0.98) and Freundlich (R 2 = 0.90–0.99) isotherms. The sorption kinetics was adequately explained by the pseudo-second-order, power function, and Elovich models. The nZVI-BC composite showed highest Langmuir predicted sorption capacity (148.10 mg g−1) followed by EP-BC composite (72.77 mg g−1). In addition to the high surface area, the higher nitrate removal capacity of nZVI-BC composite could be attributed to the combination of two processes, i.e., chemisorption (outer-sphere complexation) and reduction of nitrate to ammonia or nitrogen by Fe0. The appearance of Fe-O stretching and N-H bonds in post-sorption FTIR spectra of nZVI-BC composite suggested the occurrence of redox reaction and formation of Fe compound with N, such as ferric nitrate (Fe(NO3)3·9H2O). Coexistence of chloride ions negatively influenced the nitrate sorption. The decrease in nitrate sorption with increasing chloride ion concentration was observed, which could be due to the competition of free active sites on the sorbents between nitrate and chloride ions. The nZVI-BC composite exhibited higher nitrate removal efficiency compared to other materials even in the presence of highest concentration (100 mg L−1) of coexisting chloride ion.

Modified chrome azurol S method for detection and estimation of siderophores having affinity for metal ions other than iron

Abstract: Siderophores are small molecular weight (generally 1 kDa) ferric specific ligands produced by variety of organisms to chelate iron under iron limiting conditions. Various assays have been in use to detect and estimate different phenotypes of siderophores. Though there are various methods available for detection of iron specific siderophore or modified method for Cu specific siderophore [chalkophore], reports on modified methods for detection of siderophore having affinity for various other metal ions are scarce. In present study, a modified method was designed for screening siderophores that can bind to heavy metal ions such as Cu2+, Ni2+, Mn2+, Co2+, Zn2+, Hg2+ and Ag2+. Each of the modified chrome azurol S (CAS) solution when used to screen siderophore resulted in instant colour change similar to the traditionally used CAS solution for screening Fe3+ specific siderophores. Two bacterial cultures isolated from local rhizospheric soil produced hydroxamate and catecholate siderophores that could remove Cu2+, Ni2+, Mn2+, Co2+, Zn2+, Hg2+ and Ag2+ metal ions from CAS solution resulting in instant colour change. Similar observations were recorded on CAS agar amended with modified CAS solution. The order of complexation of metals with siderophore produced by Alcaligenes sp. RZS2 in CAS assay was as follows; Cu2+ > Ni2+ > Mn2+ > Fe3+ > Co2+ > Zn2+ > Hg2+ > Ag2+. The order of complexation of metals with siderophore produced by Pseudomonas aeruginosa RZS3 in CAS assay was as follows; Ni2+ > Co2+ > Mn2+ > Zn2+ > Fe3+ > Cu2+ > Hg2+ > Ag2+.

Synthesis and application of hematite nanoparticles for acid mine drainage treatment.

Abstract: In this paper, the synthesis of pure hematite nanoparticles, magnetic properties and its removal capacity of metal cations from acid mine drainage are well described. Initially, mixtures of iron oxide nanoparticles were synthesised using hydrated ferric chloride and ferrous sulphate salt solution by co-precipitation method and converted to hematite via calcination at 500 °C. The synthesised hematite nanoparticles have shown superparamagnetic character with saturation magnetisation of 5.6 emu g−1. Treatment of partially aerated acid mine drainage in the presence of 0.85 g L−1 of synthesised hematite resulted in complete removal of Al, Mg, Mn and Fe while for Zn and Ni over 80% and Ca and Na in between 47 and 72% removals. The sludge generated from the treated acid mine drainage was also characterised by relevant analytical instruments. Overall, the non-toxicity, stability and high metal removal capacity of hematite nanoparticles is promising for the future application in large-scale acid mine drainage treatment.

The N-Methylpyrrolidone (NMP) Effect in Iron-Catalyzed Cross-Coupling with Simple Ferric Salts and MeMgBr.

Abstract: The use of N-methylpyrrolidone (NMP) as a co-solvent in ferric salt catalyzed cross-coupling reactions is crucial for achieving the highly selective, preparative scale formation of cross-coupled product in reactions utilizing alkyl Grignard reagents. Despite the critical importance of NMP, the molecular level effect of NMP on in situ formed and reactive iron species that enables effective catalysis remains undefined. Herein, we report the isolation and characterization of a novel trimethyliron(II) ferrate species, [Mg(NMP)6 ][FeMe3 ]2 (1), which forms as the major iron species in situ in reactions of Fe(acac)3 and MeMgBr under catalytically relevant conditions where NMP is employed as a co-solvent. Importantly, combined GC analysis and 57 Fe Mossbauer spectroscopic studies identified 1 as a highly reactive iron species for the selective formation generating cross-coupled product. These studies demonstrate that NMP does not directly interact with iron as a ligand in catalysis but, alternatively, interacts with the magnesium cations to preferentially stabilize the formation of 1 over [Fe8 Me12 ]- cluster generation, which occurs in the absence of NMP.

Photochemical Vapor Generation of Tellurium: Synergistic Effect from Ferric Ion and Nano-TiO2.

Abstract: Photochemical vapor generation (PVG) is emerging as a promising analytical tool for Te determination, thanks to its efficient matrix separation, and simple and green procedure. However, the low PVG generation efficiency of Te is the bottleneck for its wide application in environmental samples containing trace Te. Herein, we reported a high efficient PVG for Te determination by synergistic effect of ferric ion and nano-TiO2. The analytical sensitivity was enhanced approximately 15-fold for Te(IV) in the presence of both ferric ions and nano-TiO2, comparing to conventional PVG. Besides, the use of nano-TiO2 can provide Te(VI) and Te(IV) an equal and high PVG efficiency in the presence of ferric ions, owned to the high photocatalytic performance of TiO2 under short-wavelength UV irradiation (254 and 185 nm). Under the optimized experimental conditions, a detection limit of 1.0 ng L–1 was obtained. The precision of replicate measurements was 2.3% (RSD, n = 7) at 0.5 μg L–1 for Te(IV). The methodology was vali...

Enhanced biofilm formation by ferrous and ferric iron through oxidative stress in Campylobacter jejuni

Abstract: Campylobacter is a leading foodborne pathogen worldwide. Biofilm formation is an important survival mechanism that sustains the viability of Campylobacter under harsh stress conditions. Iron affects biofilm formation in some other bacteria; however, the effect of iron on biofilm formation has not been investigated in Campylobacter. In this study, we discovered that ferrous (Fe2+) and ferric (Fe3+) iron stimulated biofilm formation in Campylobacter jejuni. The sequestration of iron with an iron chelator prevented the iron-mediated biofilm stimulation. The level of total reactive oxygen species (ROS) in biofilms was increased by iron. However, the supplementation with an antioxidant prevented the total ROS level from being increased in biofilms by iron and also inhibited iron-mediated biofilm stimulation in C. jejuni. This suggests that iron promotes biofilm formation through oxidative stress. Based on the results of fluorescence microscopic analysis, Fe2+ and Fe3+ enhanced both microcolony formation and biofilm maturation. The levels of extracellular DNA and polysaccharides in biofilms were increased by iron supplementation. The effect of iron on biofilm formation was also investigated with 70 C. jejuni isolates from raw chicken. Regardless of the inherent levels of biofilm formation, iron stimulated biofilm formation in all tested strains; however, there were strain variations in iron concentrations affecting biofilm formation. The biofilm formation of 92.9% (65 of 70) strains was enhanced by either 40 μM Fe2+ or 20 μM Fe3+ or both (the iron concentrations that enhanced biofilm formation in C. jejuni NCTC 11168), whereas different iron concentrations were required to promote biofilms in the rest of the strains. The findings in this study showed that Fe2+ and Fe3+ contributed to the stimulation of biofilm formation in C. jejuni through oxidative stress.