• Korean Chemical Engineering Research
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• v.52 no.5
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• pp.638-646
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• 2014

The effect of in-organic chelating agents with Fe(II) and Fe(III) in modified Fenton was evaluated to degradation BTEX (benzene, toluene, ethylbenzene, xylene). Citric acid and pyrophosphate were used in experimentals and an optimum chelating agent for BTEX degradation was determined. In $H_2O_2$/Fe(III)/citric acid, degradation of BTEX was decreased when concentration of citric acid was increased. In $H_2O_2$/Fe(III)/pyrophosphate, degradation of BTEX was increased when concentration of pyrophosphate was increased and degradation for BTEX was relatively high compared with $H_2O_2$/Fe(III)/citric acid. In $H_2O_2$/Fe(II)/chelating agents, degradation for BTEX was high and pH variation was minimized when molar ratio of Fe(II) and citric acid was 1:1. Optimum molar concentration of Fe(II), citric acid and $H_2O_2$ were 7 mM, 7mM and 500 mM for degradation of 100 mg/L of benzene to obtain best efficiency of $H_2O_2$, least precipitation of iron and best degradation.

• Journal of the Korean Chemical Society
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• v.46 no.6
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• pp.509-514
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• 2002

A method to determin Fe(II) and Fe(III) ion in aqueous solution by chemiluminescence method using a stopped flow system has been studied. The method is based on the increased chemiluminescence intensity with the addition of Fe(III) ion to a solution of lucigenin and hydrogen peroxide. The effects of KOH concentration, flow rate of reagents, $H_2O_2$ concentration and citric acid concentration used for the masking of Fe(II) ion on the chemilu-minescence intensity have been investigated. The calibration curve for total Fe was linear over the range from 1.0${\times}$$10^{-6}$ M to 1.0${\times}$$10^{-4}$M, coefficient of correlation was 0.996 and the detection limit was 1.0${\times}$$10^{-7}$M under the optimal exper-imental conditions of 4.0 M, 2.0 M, 3.5 mL/min for the concentration of $H_2O_2,$ KOH and flow rate of reagents, respec-tively. The calibration curve for Fe(Ⅲ) was linear over the range from 1.0${\times}$$10^{-6}$M to 1.0${\times}10^{-4}$ M, the coefficient of correlation was 0.997 and the detection limit was 5.0${\times}$$10^{-7}$M under the optimal experimental conditions.

• Bulletin of the Korean Chemical Society
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• v.25 no.1
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• pp.97-100
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• 2004

Tetragonal $K_2NiF_4$-type $La_{2-2x}Sr_{2x}Cu_{1-x}Fe_xO_{4-y}$ solid-solution have been synthesized by citrate based sol-gel method. The valence state of iron was determined by Mossbauer spectroscopy and subsequent iodometric titration clearly showed that the copper ions in this solid-solution are in the mixed valence state Cu(II/III). When x ${\geq}$ 0.3, Fe(III) is competing with the mixture of Cu(II) and Cu(III) and $La_{2-2x}Sr_{2x}Cu_{1-x}Fe_xO_{4-y}$ exhibits a metallic character. No evidence for Cu(II)-O-Fe(IV) ${\leftrightarrow}$ Cu(III)-O-Fe(III) valence degeneracy was observed. In contrast, a small amount of Fe(IV) is observed with increasing x (x = 0.4 and 0.5), revealing a semiconducting behavior. These results suggest that the electronic interaction of Cu(III)-O-Fe(III) contributes greatly to the metallic character, while the electronic interaction of Cu(II)-O-Fe(IV) deteriorates the metallic character of $La_{2-2x}Sr_{2x}Cu_{1-x}Fe_xO_{4-y}$.

• Journal of Korean Society on Water Environment
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• v.22 no.2
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• pp.328-332
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• 2006

Fe(III)-impregnated activated carbon (Fe-AC) was applied in the treatment of synthetic wastewater containing Cu(II). To investigate the stability of Fe-AC at acidic condition, dissolution of Fe was studied with a variation of solution pH ranging from 2 to 4. Fe-AC was unstable at pH 2, showing a gradual increase of the dissoluted Fe as reaction time increased, while negligible amount of Fe was dissoluted above pH 3. This stability test suggests the applicability of Fe-AC in the treatment of wastewater above pH 3. Adsorption capacity of Cu(II) onto activated carbon (AC) and Fe-AC was investigated in a batch and a column test. In the adsorption kinetics, rapid adsorption of Cu(II) onto AC and Fe-AC was noted at initial reaction time and then reached a near complete equilibrium after 6 hrs. Adsorption trends of Cu(II) onto AC and Fe-AC were similar, showing an increased Cu(II) adsorption at higher pH. Compared with AC, Fe-AC showed a greater Cu(II) adsorption over the entire pH range studied in this research. From the adsorption isotherm obtained with variation of the concentration of Cu(II), the maximum adsorption capacity was identified as 61,700 mg/kg.

• Economic and Environmental Geology
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• v.36 no.1
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• pp.39-48
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• 2003

The removal of chromate from aqueous solution using finely ground pyrite and biotite was investigated by batch experiments and the kinetics and the mechanism of chromate reduction were discussed. The chromate reduction by pyrite was about hundred times faster than that by biotite and was also faster at pH 3 than at pH 4. When pyrite was used, more than 90% of initial chromate was reduced within four hours at pH 4 and within 40 min. at pH 3. However, more than 400 hours was taken for the reduction of 90% of initial chromate by biotite. The results indicate that the rate of chromate reduction was strongly depending on the amount of Fe(II) in the minerals and on the dissolution rate of Fe(II) from the minerals. The reduction of chromate at pH 4 resulted in the precipitation of (Cr, Fe)(OH))$_3$$_{ (s)}$, which is believed to have limited the concentrations of dissolved Cr(III) and Fe(III) to less than expected values. When biotite was used, amounts of decreased Fe(II) and reduced Cr(Ⅵ) did not show stoichiometric relationship, which implying there was not only chromate reduction by ferrous ions in the acidic solution but also heterogeneous reduction of ferric ions by the structural ferrous iron in biotite. However, the results from a series of the experiments using Pyrite showed that concentrations of the decreased Fe(II) and the reduced Cr(Ⅵ) were close to the stoichiometric ratio of 3:1. It was because the oxidation of pyrite rapidly created ferrous ions even in oxygenated solutions and the chromate reduction by the ferrous ions was significantly faster than ferrous ion oxygenation.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.2
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• pp.123-129
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• 2005

In situ permeable reactive barrier (PRB) technologies have been proposed to reductively remove organic contaminants from the subsurface environment. The major reactive material, zero valent iron ($Fe^0$), is oxidized to ferrous iron or ferric iron in the barriers, resulting in the decreased reactivity. Iron-reducing bacteria can reduce ferric iron to ferrous iron and iron reduced by these bacteria can be applied to dechlorinate chlorinated organic contaminants. Iron reduction by iron reducing bacteria, Shewanella algae BrY, was observed both in aqueous and solid phase and the enhancement of TCE removal by reduced iron was examined in this study. S. algae BrY preferentially reduced Fe(III) in ferric citrate medium and secondly used Fe(III) on the surface of iron oxides as an electron acceptor. Reduced iron formed reactive materials such as green rust ferrihydrite, and biochemical precipitation. These reactive materials formed by the bacteria can enhance TCE removal rate and removal capacity of the reactive barrier in the field.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.4
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• pp.421-429
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• 2018

Hydrazine based reductive dissolution applied on magnetite oxide was investigated. Dissolution of Fe(II) and Fe(III) from magnetite takes place either by protonation, surface complexation, or reduction. Solution containing hydrazine and sulfuric acid provides hydrogen to break bonds between Fe and oxygen by protonation and electrons for the reduction of insoluble Fe(III) to soluble Fe(II) in acidic solution of pH 3. In terms of dissolution rate, numerous transition metal ions were examined and Cu(II) ion was found to be the most effective to speed up the dissolution. During the cycle of Cu(I) ions to Cu(II) ions, the released electron promoted the reduction of Fe(III) and Cu(II) ions returned to Cu(I) ion due to the oxidation of hydrazine. In the experimental results, the addition of a very low amount of cupric ion (about 0.5 mM) to the solution increased the dissolution rate about 40% on average and up to 70% for certain specific conditions. It is confirmed that even though the coordination structure of copper ions with hydrazine is not clear, the $Cu(II)/H^+/N_2H_4$ system is acceptable regarding the dissolution performance as a decontamination reagent.

• Preventive Nutrition and Food Science
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• v.6 no.2
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• pp.83-86
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• 2001

The autoxidation reaction of L-ascorbic acid(AsA), and, particularly, the oxidation rates of AsA in the presence of Fe(III) or Cu(II) ions were determined in water and methanol. UV spectral measurement (at 265 nm) and HPLC were used to determine the remaining amounts of AsA in water and methanol, respectively. It was found that, in the presence of metal ions, the autoxidation rate of AsA was significantly affected by the kinds of solvents used, and also by the kinds of metal ions present. Moreover, the first-order rate constants for the oxidation of non-dissociated AsA compared with dissociated-AsA were investigated. It was confirmed that the oxidation of AsA was more accelerated in the dissociated form of AsA than in the non-dissociated form of AsA in either with Fe(III) or Cu(II). It was also found that the Cu(II) at a concentration of 0.1 $\mu$M had a more significant effect on the first-order rate constants for the autoxidation of AsA than Fe(III) at 5 $\mu$M.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.1
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• pp.87-97
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• 2016

First of all, Fe or/and Mn immobilized granular activated carbons (Fe-GAC, Mn-GAC, (Fe, Mn)-GAC) were synthesized and tested to remove arsenate (As(V)). The results in batch test indicated that Fe-GAC removed As(V) effectively, even though the surface area of Fe-GAC was reduced largely. Moreover, adsorption isotherm test indicated that the experimental data fit well with Langmuir model and the maximum adsorption capacity ($q_{max}$) of Fe-GAC for As(V) was $3.49mg\;g^{-1}$, which was higher than GAC ($2.24mg\;g^{-1}$). In column test, the simulated water, which consisted of As(V), Fe(III), Mn(II) and Ca(II) in tap water, was used. Fe-GAC column with 1 hr of pre-washing time treated As(V) effectively while GAC column removed Fe(III) better than Fe-GAC column. Moreover, the increasing pre-washing time from 1 to 9 hour in Fe-GAC column enhanced Fe(III) removal with little negative impact of As(V) removal. Mostly, the column filled with Fe-GAC and GAC (i.e. the mass ratio of Fe-GAC:GAC = 2:8) showed the higher treatability of both As(V) and Fe(III), even it operated with 1 hr pre-washing time.

• Journal of Microbiology
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• v.39 no.4
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• pp.273-278
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• 2001

Shewanela, putrefaciene IR-1 and MR-1 were cultivated by using various combinations electron donor-acceptor, lactate-Fe(III) lactate-nitrate, pyruvate-FE(III), pyruvate-nitrate H$_2$ acetate-Fe(III) and H$_2$-acetate-nitrate. Both strains grew fermentatively on pyruvate and lactate but not on without and electron acceptor. In culture with Fe(III), both astrains grew on pyruvate and lactate but on H$_2$-acetate- CO$_2$. In cultivation with nitrate, both stains grew on pyruvate lactage and on H$_2$-acetate-CO$_2$ The growth yields of IR-1 pyruvate, pyruvate-Fe(III) and lactate-Fe(III) were about 3.4, 3.5, and 3.6(g cell/M substrate), respectively. From the growth properties of both strains on media with Fe(III) as an electron acceptor, the bacterial growth was confirmed not to be increased by addition of Fee(III) as an electron acceptor to the growth medium, which indicates a possibility that the dissimilatory reduction of Fe(III) to Fe(III) may not be coupled to free energy production.