• Bulletin of the Korean Chemical Society
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• v.4 no.3
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• pp.120-123
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• 1983

The reaction of hexacyanoferrate (Ⅲ) with nitrotoluenes in aqueous acetic acid containing perchloric acid(1.0 M) at $50^{\circ}C$ gave the corresponding aldehyde as the major product. The order with respect to each of the reactants ― substrate, oxidant and acid ― was found to be unity. The Hammett plot yielded a ${\sigma}^+$ value of -1.30, and the kinetic isotope effect gave a $k_H/k_D$ value of 6.2. The pathway for the conversion of the nitrotoluenes to the products has been mechanistically visualized as proceeding through the benzylic radical intermediate, formed in the rate determining step of the reaction.

• Bulletin of the Korean Chemical Society
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• v.22 no.8
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• pp.850-856
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• 2001

This study investigates the ozonation kinetics of 2-chlorophenol in wastewater under acidic condition. Intermediates and by-products generated during the process were rigorously identified and quantified. The major by-products are four carboxylic acids: tartaric acid, oxalic acid, maleic acid, and hydroxymalonic acid. The generation of these organic acids is in agreement with theoretical predictions. But hydroxylated compounds are more favorable to produce than their corresponding non-hydroxylated ones. Based on the information concerning the generation of organic acids and other aromatic intermediates, the complete reaction pathways toward mineralization can be proposed and mathematically modeled. The fitted second-order rate constants are in the same order of magnitude with the results from other studies. Using these oxidation pathways and the corresponding kinetic model, by-products generated in ozonation process can be predicted. This can help in optimizing the design and operation of any subsequent treatment processes.

• Bulletin of the Korean Chemical Society
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• v.14 no.6
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• pp.666-668
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• 1993

A microbial BOD sensor using immobilized Hansenula anomala was prepared for the estimation of BOD. The sensor voltage was increased with time and increasing concentration of GGA when it was inserted in a sample solution. A linear relationship was obtained with a correlation coefficient, 0.998 between the concentration of standard GGA solutions and dV/dt by using the initial change of voltage, in which the response time was 20 min. It could be concluded that the oxidation of GGA conformed to a first-order kinetics. Therefore, the good linearities were also observed at various times. This sensor showed the best linearity at 30 min.

• Analytical Science and Technology
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• v.18 no.2
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• pp.120-129
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• 2005

Volatile organic compounds (VOCs) have been recognized as major contributor to air pollution. The catalytic oxidationis is one of the most important processes for VOCs destruction due to the possibility getting high efficiency at low temperature. In this study, monometallic Pt, Ir and bimetallic Pt-Ir were supported to $TiO_2$. In order to distribute metals uniformly, $H_2O-H_2$ treatment method was used. Xylene, toluene and MEK were used as reactants. The monometallic or bimetallic catalysts were prepared by the excess wetness impregnation method and characterized by XRD, XPS, and TEM analysis. Pt catalyst showed higher conversion than Ir catalyst and Pt-Ir bimetallic catalyst showed the highest conversion. The catalysts prepared by $H_2O-H_2$ treatment had better VOC's conversion than that of nothing treatment. In the VOCs oxidation, Pt-Ir bimetallic catalysts had multipoint active sites, so it improved the range of Pt metal state. Therefore, bimetallic catalysts showed higher conversion of VOCs than monometallic ones. $H_2O-H_2$ treatment effected an uniform distribution of Pt particles. In VOCs oxidation was found to follow first order reaetion kinetics. The activation energy of $H_2O-H_2$ treatment catalysts was lower than that of untreated ones. In this study, the a small amount of Ir was used with Pt to promote the oxidation conversion of VOCs.

• Korean Chemical Engineering Research
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• v.47 no.3
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• pp.292-302
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• 2009

The wet oxidation of phenol has been investigated at temperatures from 150 to $250^{\circ}C$ and oxygen partial pressures from 25.8 to 75.0 bar with initial pH of 1.0 to 12.0 and initial phenol concentration of 10 g/l. Chemical Oxygen Demand COD has bee measured to estimate the oxidation rate. Reaction intermediates have been identified and their concentration profiles have been determined using liquid chromatography. The destruction rate of phenol have shown the first-order kinetics with respect to phenol and the changes in COD during wet oxidation have been described well with the lumped model. The impact of various homogeneous catalysts, such as $Cu^{2+}$, $Fe^{2+}$, $Zn^{2+}$, $Co^{2+}$ and $Ce^{3+}$ ions, on the destruction rate of phenol and COD has also been studied. The homogeneous catalyst of $CuSO_4$ has been found to be the most effective for the destruction of phenol and COD during wet oxidations. The destruction rate of formic acid formed during wet oxidations of phenol have increased as increasing temperature and $CuSO_4$ concentration. The final concentrations of acetic acid which has been formed during wet oxidations and difficult to oxidize have increased with reaction temperature and with decrease in the catalyst load.

• Environmental Engineering Research
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• v.13 no.3
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• pp.131-135
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• 2008

In this study, Fe(VI) was employed as a multi-functional agent to treat the simulated industrial wastewater contaminated with Cu(II)-EDTA through oxidation of EDTA, decomplexation of Cu(II)-EDTA and subsequent removal of free copper through precipitation. The decomplexation of $10^{-4}\;M$ Cu(II)-EDTA species was performed as a function of pH at excess concentration of Fe(VI). It was noted that the acidic conditions favor the decomplexation of Cu(II)-EDTA as the decomplxation was almost 100% up to pH 6.5, while it was only 35% at pH 9.9. The enhanced degradation of Cu(II)-EDTA with decreasing the pH could be explained by the different speciation of Fe(VI). $HFeO_4^-$ and $H_2FeO_4$, which are relatively more reactive than the unprotonated species $FeO_4^{2-}$, are predominant species below neutral pH. It was noted that the decomplexation reaction is extremely fast and within 5 to10 min of contact, 100% of Cu(II)-EDTA was decomplexed at pH 4.0. However, at higher pH (i.e., pH 10.0) the decomplexation process was relatively slow and it was observed that even after 180 min of contact, maximum ca 37% of Cu(II)-EDTA was decomplexed. In order to discuss the kinetics of the decomplexation of Cu(II)-EDTA, the data was slightly fitted better for the second order rate reaction than the first order rate reaction in the excess of Fe(VI) concentration. On the other hand, the removal efficiency of free Cu(II) ions was also obtained at pH 4.0 and 10.0. It was probably removed through adsorption/coagulation with the reduced iron i.e., Fe(III). The removal of total Cu(II) was rapid at pH 4.0 whereas, it was slow at pH 10.0. Although the decomplexation was 100% at lower pH, the removal of free Cu(II) was relatively slow. This result may be explicable due to the reason that at lower pH values the adsorption/coagulation capacity of Fe(III) is greatly retarded. On the other hand, at higher pH values the decomplexation of Cu(II)-EDTA was partial, hence, slower Cu(II) removal was occurred.

• Journal of the Korean Magnetics Society
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• v.22 no.3
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• pp.85-90
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• 2012

Oxidation of the $Nd_2Fe_{14}B$ compound crystal and its effect on the coercivity of the fine $Nd_2Fe_{14}B$ crystal particles were investigated. Oxidation kinetics of the $Nd_2Fe_{14}B$ compound crystal was investigated using an excessively grown $Nd_2Fe_{14}B$ grains in the $Nd_{15}Fe_{77}B_8$ alloy ingot. Oxidation of the $Nd_2Fe_{14}B$ compound crystal occurred by dissociation of the phase into multi-phase mixture of ${\alpha}$-Fe, $Fe_3B$, and Nd oxides. Oxidation rate of the $Nd_2Fe_{14}B$ compound crystal showed no dependence on the crystallographic direction. The oxidation reaction was modeled according to simple linear relationship. Activation energy for the oxidation of $Nd_2Fe_{14}B$ compound crystal was calculated to be approximately 26.8 kJ/mol. Fine $Nd_2Fe_{14}B$ crystal particles in near single domain size was prepared by ball milling of the HDDR-treated $Nd_{15}Fe_{77}B_8$ alloy, and these particles were used for investigating the effect of oxidation on the coercvity. The near single domain size $Nd_2Fe_{14}B$ crystal particles (${\fallingdotseq}0.3\;{\mu}m$) had high coercivity over 9 kOe. However, the coercivity was radically reduced as the temperature increased in air (<2 kOe at $200^{\circ}C$). This radical coercivity reduction was attributed to the soft magnetic phases, ${\alpha}$-Fe and $Fe_3B$, which were formed on the surface of the fine particles due to the oxidation.

• Journal of Soil and Groundwater Environment
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• v.20 no.6
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• pp.117-126
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• 2015

Reductive degradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by nanoscale zero-valent iron (nZVI) was investigated to evaluate the feasibility of using it for in-situ groundwater remediation. Batch experiments were conducted to quantify the kinetics and efficiency of RDX removal by nZVI, and to determine the effects of pH, dissolved oxygen (DO), and ionic strength on this process. Experimental results showed that the reduction of RDX by nZVI followed pseudo-first order kinetics with the observed rate constant (k_obs) in the range of 0.0056-0.0192 min⁻¹. Column tests were conducted to quantify the removal of RDX by nZVI under real groundwater conditions and evaluate the potential efficacy of nZVI for this purpose in real conditions. In column experiment, RDX removal capacity of nZVI was determined to be 82,500 mg/kg nZVI. pH, oxidation-reduction potential (ORP), and DO concentration varied significantly during the column experiments; the occurrence of these changes suggests that monitoring these quantities may be useful in evaluation of the reactivity of nZVI, because the most critical mechanisms for RDX removal are based on the chemical reduction reactions. These results revealed that nZVI can significantly degrade RDX and that use of nZVI could be an effective method for in-situ remediation of RDX-contaminated groundwater.

• Environmental Engineering Research
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• v.20 no.1
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• pp.89-97
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• 2015

Remediation of wastewater contaminated with metal(II)-complexed species (Cu(II)-NTA (NTA: nitrilotriacetic acid), Cu(II)-EDTA (EDTA: ethylenediamine tetraacetic acid) and Cd(II)-EDTA is attempted using the potential applicability of ferrate(VI). Kinetics of pollutant degradation is obtained with the removal of ferrate(VI) studied at wide range of pH (8.0-10.0) and the concentration of metal(II)-complexed species (0.3 to 15.0 mmol/L) employing a constant dose of ferrate(VI) i.e., 1.0 mmol/L. Pseudo-first-order and pseudo-second-order rate constants were obtained in the reduction of ferrate(VI) which was then employed to obtain the overall rate constants of the pollutant degradation. The mineralization of NTA and EDTA was obtained with the change in TOC (total organic carbon) values collected by the ferrate(VI) treated pollutant samples. Decrease in pH and molar pollutant concentrations was greatly favored the percent mineralization of NTA or EDTA by the ferrate(VI) treatment. The treated pollutant samples were filtered and subjected for AAS (atomic absorption spectrophotometric) analysis to assess the simultaneous removal of copper and cadmium from aqueous solutions at the studied pH as well at the elevated pH 12.0. Results show that an enhanced removal of cadmium or copper was achieved at pH 12.0. Overall, ferrate(VI) possesses multifunctional application in wastewater treatment as it oxidizes the degradable impurities and removes metallic impurities by coagulation process.

• Toxicological Research
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• v.15 no.1
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• pp.95-101
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• 1999

Cytochrome P450 (CYP) 3A4 metabolizes aflatoxin B1 (AFB1) to AFB1-exo-8,9-epoxide (8,9-epoxidation) and aflatoxin Q1 (AFQ1; 3$\alpha$-hydroxylation) simultaneously. We investigated whether each metabolite was formed via its own binding site of CAP3A4 active site. Kinetics of the formation of the two metabolites were sigmoidal and consistent with the kinetics of substrate activation. The HIll model predicted that two substrate binding wites are involved in the oxidationof AFB1 by CYP3A4. Dehydronifedipine, a metabolite of nifedipine generated by CYP3A4, inhibited the formation of AFQ1 without any inhibition in the formation of AFB1-exo-8,9-epoxidation. Dehydronifedipine was found to act as a reversible competitive inhibitor against 3$\alpha$-hydroxylation of AFB1. Vmax and S0.5 of the 8,9-epoxidation were not changed in the presence of 0, 50, or 100 $\mu\textrm{M}$ dehydronifedipine. S0.5 of 3$\alpha$-hydroxylation was increased from 58$\pm$4 $\mu\textrm{M}$ to 111$\pm$8 $\mu\textrm{M}$ in the presence of 100 $\mu\textrm{M}$ nifedipine whereas Vmax was not changed. These results suggest that there exist two independent binding sites in the active site of CAP3A4 . One binding site is responsible for AFB1-exo-8,9-epoxidation and the other is involved in 3$\alpha$-hydroxylation of AFB1. Dehydronifedipine might selectively bind to the site which is responsible for the formation of AFQ1 in the active site of CYP3A4.