• Journal of Korean Society of Environmental Engineers
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• v.29 no.5
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• pp.564-570
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• 2007

This study investigated the treatment of liquid waste containing highly concentrated iron(III)-ethylenediaminetetraaceticacid (Fe(III)-EDTA) of 70,000 mg/L by an underwater electrical discharge process using low voltage and high current. When AC voltage is applied to the discharging electrode with the other electrode grounded, the temperature of the liquid waste around the discharging electrode rapidly increases, and at the same time, hydrogen and oxygen gases are formed at the electrode as a result of electrochemical reactions. Ultimately, gases formed by vaporization of water and electrochemical reactions cover the electrode. Since the liquid waste is electrically conductive, it elongates the ground electrode up to the border of the gas layer, where electrical discharge occurs. Without hydrogen peroxide, electrical discharge was able to remove about 50% of Fe(III)-EDTA. As the concentration of hydrogen peroxide added increased, the removal efficiency of Fe(III)-EDTA increased. When the molar ratio of hydrogen peroxide to the initial Fe(III)-EDTA was higher than 24.7, more than 80 g of Fe(III)-EDTA was removed with an energy of 1 kWh. A comparison between tungsten and steel electrodes showed that electrode material did not affect the Fe(III)-EDTA removal. In the present underwater electrical discharge process, the removal of Fe(III)-EDTA was completed within 30 min at molar ratios of hydrogen peroxide to the initial Fe(III)-EDTA higher than 24.7.

• Applied Chemistry for Engineering
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• v.17 no.5
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• pp.552-556
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• 2006

An advanced oxidation process catalyzed by iron ions in the presence of hydrogen peroxide, the so-called Fenton's reaction, has been applied to the treatment of steam generator chemical cleaning waste containing highly concentrated iron(III)- ethyl-enediaminetetraaceticacid (Fe(III)-EDTA) of 70000 mg/L. The experiments for the degradation of Fe(III)-EDTA were carried out not only with a simulated waste, but also with the real one. The effect of pH and the amount of hydrogen peroxide added to the waste on the degradation was examined, and the results were discussed in several aspects. The optimal pH to maximize the degradation efficiency was dependent on the amount of hydrogen peroxide added to the waste. i.e., when the amount of hydrogen peroxide was different, maximum degradation efficiency was obtained at different pH's. The optimal amount of hydrogen peroxide relative to that of Fe(III)-EDTA was found to be 24.7 mol ($H_{2}O_{2}$)/mol (Fe(III)-EDTA) at pH around 9.

• Analytical Science and Technology
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• v.24 no.3
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• pp.231-235
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• 2011

A spectrofluorimetric method for the determination of EDTA in real samples such as mayonnaise, powder detergent and cleansing cream with tiron (4,5-dihydroxy-1,3-benzenedisulfonic acid) as a fluorimetric reporter was developed. When tiron is chelated with Cu(II), the fluorescent intensity is decreased by a quenching effect. However, when Cu(II)-tiron chelate reacts with EDTA, fluorescent intensity is increased as tiron is released. Several experimental conditions such as pH of the sample solution, the amount of Cu(II), the amount of tiron, heating temperature and heating time were optimized. Fe(III) interfered more seriously than any other ions, interference of Fe(III) could be disregarded, because Fe(III) was scarcely contained in selected real samples. The linear range of EDTA was from $8.0{\times}106{-8}\;M$ to $2.0{\times}10^{-6}\;M$. With this proposed method, the detection limit of Fe(III) was $5.2{\times}10^{-8}\;M$. Recovery yields of 92.7~99.3% were obtained. Based on experimental results, it is proposed that this technique can be applied to the practical determination of EDTA.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.7
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• pp.729-734
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• 2008

The higher valence state of iron i.e., Fe(VI) was employed for the treatment of Cu(II)-EDTA in the aqueous/waste waters. The ferrate(VI) was prepared through wet oxidation of Fe(III) by sodium hypochlorite. The purity of prepared Fe(VI) was above 93%. The stability of Fe(VI) solution decreased as solution pH decreased through self decomposition. The reduction of Fe(VI) was obtained by using the UV-Visible measurements. The dissociation of Cu(II)-EDTA complex through oxidation of EDTA using Fe(VI) and subsequent treatment of organic matter and metal ions by Fe(III) reduced from Fe(VI) in bench-scale of continuous flow reactor were studied. The removal efficiencies of copper were 69% and 79% in pH control basin and reactor, respectively, at 120 minutes as retention time. In addition, Cu(II)-EDTA in the reactor was decomplexated more than 80% after 120 minutes as retention time. From this work, a continuous treatment process for the wastewater containing metal and EDTA by employing Fe(VI) as muluti-functional agent was developed.

• 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 Chemical Society
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• v.43 no.4
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• pp.423-429
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• 1999

A spectrofluorimetric method for the determination of Fe(III) in aqueous solution with 4,5-dihydroxy-1,3-benzenedisulfonic acid(Tiron) as a fluorimetric reporter was developed. Tiron, which is very soluble in water,is a good fluorimetric reagent. However, when Tiron was complexed with Fe(III), the fluorescent intensity was decreased proportionally with the concentration of Fe(III) by a quenching effect. The excitation and fluorescene wavelength of Tiron showing the quenching effect by Fe(III) at pH 4.5 were 312 nm and 341 nm, respectively. The highest sensitivities were shown at Tiron concentration of $1.0{\times}10^{-2}M$. To enhance the quenching effect, the Fe(III)-Tiron complex solution was heated to 80$^{\circ}C$ for 90 minutes. As for Fe(III), the most interfering ion was Cu(II). The interference effects could be mostly eliminated by pH adjustment or by adding EDTA. The concentration ranges showing the linear response to Fe(III) was from $5.0{\times}10^{-7}M\;to\;6.0{\times}10^{-5}M$ With this proposed method, the detection limits of Fe(III) was $2.8{\times}10^{-6}M$. Recovery of Fe(lII) in a synthetic sample was almost quantitative. Based on experimental results, it is proposed that the above technique can be applied to the practical determination of Fe(III).

• Journal of Electrochemical Science and Technology
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• v.10 no.3
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• pp.321-328
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• 2019

A new miniaturized all solid-state contact Fe (III)-selective PVC membrane electrode based on Fe (II) phthalocyanine as a neutral carrier was described. The effects of the membrane composition and foreign ions on the electrode performance was investigated. The best performance was obtained with a membrane containing 32% poly (vinyl chloride), 64% dioctylsebacate, 3% Fe (II) phthalocyanine, and 1% potassium tetrakis (p-chlorophenyl) borate. The electrode showed near Nernstian response of $26.04{\pm}0.95mV/decade$ over the wide linear concentration range $1.0{\times}10^{-6}$ to $1.0{\times}10^{-1}M$, and a very low limit of detection $1.8{\pm}0.5{\times}10^{-7}M$. The potentiometric response of the developed electrode was independent at pH 3.5-5.7. The lifetime of the electrode was approximately 3 months and the response time was very short (< 7 s). It exhibited excellent selectivity towards Fe (III) over various cations. The miniaturized all solid-state contact Fe (III)-selective membrane electrode was successfully applied as an indicator electrode for the potentiometric titration of $1.0{\times}10^{-3}M$ Fe (III) ions with a $1.0{\times}10^{-2}M$ EDTA and the direct determination of Fe (III) ions in real water samples.

• Korean Journal of Microbiology
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• v.29 no.5
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• pp.307-313
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• 1991

A yellow-green, fluorescent siderophore A3 was extracellularly produced under iron-limited growth conditions from Pseudomonas synxantha A3. The physicochemical and biological properties of siderophore A3 were examined. The approxiamte molecular weights of the Fe(III)-siderophore A3-1 complex and Fe(III)-siderophore A3-2 complex were estimated to be about 1,300 and 1,100, respectively, by Bio-gel P2 gel exclusion chromatography. The molar ratio between the siderophore and the Fe(III)was 1.08 mole. The molecular weight of the complex could be calculated with this ratio and the new values were 1,150 and 960, respectively. The binding constant(K) between thesiderophore A3 and Fe(III) that determined by displacing the iron from the Fe(III)-siderophore complex with EDTA was 4.12*10$^{18}$ at pH 5.0. Siderophore A3 appeared to have antibacterial activity on several bacterial strains, however, ferric siderophore Ae complex did not show that activity. The cytotoxicity of siderophore A3 was obtained from Human Chronic Myelogenous Leudemia K562 cells. Inhibition concentration (50%)($IC_{50}$ ) was $0.17\mu$\{g/ml}.

• Journal of Soil and Groundwater Environment
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• v.14 no.2
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• pp.26-32
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• 2009

In this study, the degradation of BTEX (benzene, toluene, ethylbenzene, xylene) was tested in both (Fe$^{3+}$+chelating agent)/H$_2$O$_2$system [Fe(III) 1 mM, oxalate 6 mM, H$_2$O$_2$ 3%, and pH 6] and UV/(Fe3++ chelating agent)lHzOz system [UV dose 17.4 kWhlL, Fe(III) 1mM, oxalate 6 mM,H$_2$O$_2$ 1%, and pH 6]. The types of chelating agents used in experiments were catechol, NTA, gallic, acetyl acetone, succinic, acetate, EDTA, citrate, malonate, and oxalate and the optimum chelating agent for BTEX degradation was determined. The results showed that acetate was the optimum chelating agent for BTEX degradation in both (Fe$^{3+}$+chelating agent)/H$_2$O$_2$ and UV/(Fe$^{3+}$+chelating agent)/H$_2$O$_2$ system, and UV radiation enhanced the degradation of BTEX with any types of chelating agents. Moreover, UV/(Fe$^{3+}$+chelating agent)/H$_2$O$_2$ system, which chelating agent was acetate, removed effectively mixtures of BTEX and MTBE (methyl tert-butyl ether) when the concentration of both BTEX and MTBE was 200 mg/L, respectively. In this system, BTEX was degraded completely and 85% of MTBE was degraded at the reaction time of 180 min. Therefore, UV/((Fe$^{3+}$+chelating agent)/H$_2$O$_2$ system with acetate as a chelating agent removed not only BTEX but also BTEX and MTBE, effectively.

• Journal of the Korean Chemical Society
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• v.15 no.2
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• pp.49-54
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• 1971

It is shown that the impurities of Cu(II), Pb(II), Zn(II) and Ag(I) in Bismuth metal and the components of Pb(II), Zn(II) and Sn(IV) in Bismuth alloy are separated into their components from each other by elutions through $3.14cm^2{\times}10cm$ cation exchange resin, $Dowex\;50w\;{\times}\;8$ (100~200 mesh), column with the mixed solutions of HAc and NaAc as the eluents. The elution curve of Fe(III) has a long tailing and is not separated quantitatively from Bi(III). The eluents used for this separation are as follows; 1M HAc + 0.1M NaAc (pH 3.36) for Fe(III) and Bi (III). 0.3M HAc + 0.3M NaAc (pH 4.70) for Cu(II), Pb(II) and Zn(II). 0.5M HAc + 0.5M NaAc (pH4.70) for Ag(I) and Sn(IV). The analysis of cations eluted are carried out by spectrophotometry and EDTA titrimetry. Their recoveries are more than 99%.