• Journal of Soil and Groundwater Environment
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• v.22 no.1
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• pp.41-48
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• 2017

Persulfate (PS) activated with nanosized zero-valent iron (NZVI) was tested as a reagent to remove phenol from groundwater. Batch degradation experiments indicated that NZVI/PS molar ratios between 1 : 2 and 1 : 5 were appropriate for complete removal of phenol, and that the time required for complete removal varied with different PS and NZVI dosages. Chloride ions up to 100 mM enhanced the phenol oxidation rate, and nitrate of any concentration up to 100 mM did not significantly affect the oxidation rate. NZVI showed greater performance than ferrous iron did as an activator for PS. A by-product was formed along with phenol degradation but subsequently was completely degraded, which showed the potential to attain mineralization with the NZVI/PS system. Tests with radical quenchers indicated that sulfate radicals were a predominant radical. The results of this study suggest that NZVI is a promising activator of PS for treating contaminated groundwater.

• Advances in nano research
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• v.3 no.3
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• pp.169-176
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• 2015

Iron nanoparticles were made by using the modified coprecipitation technique. Usually the characteristics of synthesised particles depend upon the process parameters such as the ratio of the iron ions, the pH of the solution, the molar concentration of base used, type of reactants and temperature. A modified coprecipitation method was adopted in this study. A magnetic stirrer was used for mixing and the morphology and nature of particles were observed after synthesis. Nanoparticles were characterised through XRD. Obtained nanoparticles showed the formation of magnetite and maghemite under citric acid and oxalic acid as stabilisers respectively. The size of nanoparticle was greatly affected by the use of different types of stabilisers. Results show that citric acid greatly reduced the obtained particle size. Particle size as small as 13 nm was obtained in this study. The effects of different kinds of nucleating agents were also observed and two different types of nucleating agents were used i.e. potassium hydroxide (KOH) and copper chloride ($CuCl_2$). Results show that the use of nucleating agent in general pushes the growth phase of nanoparticles towards the end of coprecipitation reaction. The particles obtained after addition of nucleating agent were greater in size than particles obtained by not utilising any nucleating agent. These particles have found widespread use in medical sciences, energy conservation and electronic sensing technology.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2873-2876
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• 2010

Excess free iron generates oxidative stress that may contribute to the pathogenesis of various causes of neurodegenerative diseases. Previous studies have shown that one of the primary causes of increased brain iron may be the release of excess iron from intracellular iron storage molecules. In this study, we attempted to characterize the oxidative damage of DNA induced by the reaction of ferritin with $H_2O_2$. When DNA was incubated with ferritin and $H_2O_2$, DNA strand breakage increased in a time-dependent manner. Hydroxyl radical scavengers strongly inhibited the ferritin/$H_2O_2$ system-induced DNA cleavage. We investigated the generation of hydroxyl radical in the reaction of ferritin with $H_2O_2$ using a chromogen, 2,2'-azinobis-(2-ethylbenzthiazoline-6-sulfonate) (ABTS), which reacted with ${\cdot}OH$ to form $ABTS^{+\cdot}$. The initial rate of $ABTS^{+\cdot}$ formation increased as a function of incubation time. These results suggest that DNA strand breakage is mediated in the reaction of ferritin with $H_2O_2$ via the generation of hydroxyl radicals. The iron-specific chelator, deferoxamine, also inhibited DNA cleavage. Spectrophotometric study using a color reagent showed that the release of iron from $H_2O_2$-treated ferritin increased in a time-dependent manner. Ferritin enhanced mutation of the lacZ' gene in the presence of $H_2O_2$ when measured as a loss of $\alpha$-complementation. These results indicate that ferritin/$H_2O_2$ system-mediated DNA cleavage and mutation may be attributable to hydroxyl radical generation via a Fenton-like reaction of free iron ions released from oxidatively damaged ferritin.

• Journal of Microbiology and Biotechnology
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• v.18 no.8
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• pp.1357-1363
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• 2008

The $P_{entC}$ promoter of the entCERA operon encoding enzymes for enterobactin biosynthesis in Escherichia coli is tightly regulated by the availability of iron in the culture medium. In iron-rich conditions, the $P_{entC}$ promoter activity is strongly repressed by the global transcription regulator Fur (ferric uptake regulator), which complexes with ferrous ions and binds to the Fur box 19-bp inverted repeat. In this study, we have constructed the expression vector pOS2 containing the $P_{entC}$ promoter and characterized its repression, induction, and modulation by quantifying the expression of the lacZ reporter gene encoding $\beta$-galactosidase. $\beta$-Galactosidase activities of E. coli transformants harboring pOS2-lacZ were highly induced in the presence of divalent metal ion chelators such as 2,2'-dipyridyl and EDTA, and were strongly repressed in the presence of excess iron. It was also shown that the basal level $\beta$-galactosidase expression by the $P_{entC}$ promoter was drastically decreased by incorporating the fur gene into the expression vector. Since the newly developed iron chelator-inducible expression system is efficient and cost-effective, it has wide applications in recombinant protein production.

• The Korean Journal of Physiology and Pharmacology
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• v.18 no.2
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• pp.129-134
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• 2014

It has been suggested that transition metal ions such as iron can produce an oxidative injuries to nigrostriatal dopaminergic neurons, like Parkinson's disease (PD) and subsequent compensative increase of tetrahydrobiopterin ($BH_4$) during the disease progression induces the aggravation of dopaminergic neurodegeneration in striatum. It had been established that the direct administration of $BH_4$ into neuron would induce the neuronal toxicity in vitro. To elucidate a role of $BH_4$ in pathogenesis in the PD in vivo, we assessed the changes of dopamine (DA) and $BH_4$ at striatum in unilateral intranigral iron infused PD rat model. The ipsistriatal DA and $BH_4$ levels were significantly increased at 0.5 to 1 d and were continually depleting during 2 to 7 d after intranigral iron infusion. The turnover rate of $BH_4$ was higher than that of DA in early phase. However, the expression level of GTP-cyclohydrolase I mRNA in striatum was steadily increased after iron administration. These results suggest that the accumulation of intranigral iron leads to generation of oxidative stress which damage to dopaminergic neurons and causes increased release of $BH_4$ in the dopaminergic neuron. The degenerating dopaminergic neurons decrease the synthesis and release of both $BH_4$ and DA in vivo that are relevance to the progression of PD. Based on these data, we propose that the increase of $BH_4$ can deteriorate the disease progression in early phase of PD, and the inhibition of $BH_4$ increase could be a strategy for PD treatment.

• Applied Chemistry for Engineering
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• v.35 no.3
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• pp.255-259
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• 2024

In this study, an aqueous-based redox flow battery (RFB) was constructed using tungstosilic acid (TSA), which is a kind of polyoxometalate, as the negative electrode active material and iron chloride (FeCl3) as the positive electrode active material in a sulfuric acid (H₂SO₄) supporting electrolyte. As a result of the cell's performance, it exhibited capacity fading and low energy efficiency. To address these issues, malic acid (MA), an organic additive, was introduced to the positive electrode active material and then tested for electrochemical properties and single cell performance. The malic acid in the iron chloride aqueous solution is working as a chelate agent, and two carboxyl groups are effectively coordinated with iron ions. It was found that MA reduced the electrolyte resistance of the positive electrode active material, leading to chemical stabilization and an increase in capacity and energy efficiency.

• Journal of Conservation Science
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• v.5 no.2 s.6
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• pp.35-44
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• 1996

We propose a new method to remove salts that have permeated into excavated metal objects. This method cleans the excavated metal objects by using high temperature, high pressure deoxvgenated water containing inhibitors for corrosion of metals. The method greatly reduces the washing time compared with previous methods. Waste water from the method does not need treatment, nor do chemicals need to be removed from the metal objects. Furthermore, this method is applicable to some kind of metals(for example iron objects, bronze objects). We measured quantitatively the soluble salts dissolved from actual metal objects and found that there was a large difference between soluble chloride ions and sulfate ions.

• KSBB Journal
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• v.13 no.2
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• pp.119-124
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• 1998

Twelve bacterial strains capable of growing on phenol minimal medium were isolated from iron foundry activated sludge by enrichment culture, and amount them, one isolate which was the best in cell growth and phenol degradation was selected and identified as Acinetobacter junii POH. The optimal temperature, initial pH and phenol concentration in the above medium were 3$0^{\circ}C$, 7.5 and 1000 ppm, respectively. Cell growth of Acinetobacter junii POH dramatically increased 20 hrs cultivation-time and reached a almost stationary phsae 40 hrs cultivation-time then phenol was degraded about 98%. Cell growth was inhibited y phenol at concentrations over 1500 ppm. The isolate was resistant to several antibiotics as well as various heavy metal ions. The growth-limiting log P value of Acinetobacter junii POH on organic solvents was 2.9 in the LB medium. Therefore, it is suggested that Acinetobacter junii POH could be effectively used for the biological treatment of wastewater containing the presence of heavy metal ions and organic solvents.

• Journal of Magnetics
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• v.4 no.4
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• pp.115-118
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• 1999

$MgFe_2O_4$ has been studied with X-ray diffraction, M ssbauer spectroscopy and vibration sample magnetometer (VSM). The crystal structure of the sample is found to have a cubic spinel structure with a lattice constant of $a_0=8.390$\pm$0.005$\AA$.$ The iron ions at both A (tetrahedral) and B (octahedral)sites are found to be in ferric high-spin states. Its Neel temperature TN is found to be 710$\pm$3 K. The Debye temperature for the A and B sites found to be 417$\pm$5 K and 331$\pm$5 K., respectively. Atomic migation from the A to the B sites starts near 425 K and increases rapidly with increasing temperature to such a degree that 31% of the ferric ions at the A sites have moved over to the B sites by 600 K.

• Textile Coloration and Finishing
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• v.8 no.6
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• pp.40-46
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• 1996

In order to investigate a practical application of fibrous absorbents to transition metals such as copper, nickel, cobalt, chrome, and iron, amidoximated fiber as a particular class of solid chelate agents were prepared from acrylic fibers treatment with hydroxylamine. The adsorption mechanisms of metal ions onto amidoximated acrylic fibers and their complexes were studied. Amidoximation of acrylic fiber with hydroxylamine is found to be first-order reaction, followed by the disappearance of infrared adsorption peaks due to nitrile groups of acrylic fibers. The uptake of metal ions onto amidoximated acrylic fiber is increased with temperature raising and the adsorption is also depended on pH of the soiutions. About 70% of metal ions can be recovered from aqueous solutions of Ni(II), Co(II), Cr(III), and Fe(II) on the concentration below 5x 10$^$^{-4}$ in the range of pH 2.1~10.0. Transition metals are adsorbed to form complex with amidoxime group by the ligand sites such as C=N, NH, NO, NHOH.OH.