• Title, Summary, Keyword: 영가철

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Research on Remediation of Trichloroethylene using Zero Valent Iron Bipolar Packed Bed Electrodes (영가철 충진 복극전해조를 이용한 TCE 정화기법에 관한 연구)

  • Park, Yu-Ri;Shin, Ja-Won;Park, Joo-Yang
    • Journal of The Korean Society of Civil Engineers
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    • v.32 no.1B
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    • pp.85-91
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    • 2012
  • Permeable Reactive Barriers (PRBs) using zero valent iron (ZVI, $Fe^0$) is a promising technology for in-situ remediation of trichloroethylene (TCE) forming dense non aqueous phase liquid (DNAPL). The objective of this study is to develop an enhanced treatment method of trichloroethylene-contaminated groundwater using ZVI packed bed with direct current (D.C.). A column experiment was performed to investigate degradation efficiency of TCE that was performed in three different combination of control (only sand), ZVI column (ZVI:sand, packing ratio 1:2(v/v)) and bipolar column (ZVI:sand=1:2(v/v) with electric current) in the test columns. As the results of this study, the degradation efficiency of TCE was improved with simultaneous application of both bipolar column compared to that used ZVI column. Because ZVI particles are isolated and individual particles act like small electrodes. In this experiment, it was indicated a basic material for application of bipolar packed bed as electro-PRBs that was effective degradation of TCE.

A Study on Transport Characteristics of CMC-modified Zero Valent Iron (ZVI) Nanoparticles in Porous Media (다공성 매질내에서 CMC로 표면개질된 영가철 나노입자의 이동 특성에 관한 연구)

  • Cho, Yun-Chul;Choi, Sang-Il
    • Journal of Soil and Groundwater Environment
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    • v.14 no.6
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    • pp.101-107
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    • 2009
  • Carboxymethyl cellulose (CMC) as stabilizer is expected to facilitate in-situ delivery of zero-valent iron (ZVI) nanoparticles in a contaminated aquifer because it increases dispersity of ZVI nanoparticles. This work investigated the transport of CMC-stabilized ZVI nanoparticles (CMC-Fe) using column breakthrough experiments. The ZVI nanoparticles (100 mg/L Fe) were transportable through sand porous media. In contrast, non-stabilized ZVI nanoparticles rapidly agglomerate in solution and are stopped in sand porous media. At pH 7 of solution approximately 80% CMC-Fe were eluted. When the pH of solution is below 5, 100% CMC-Fe were eluted. These results suggest that the mobility of CMCFe was increased as pH decreases. In the mobility test under different ionic strengths using $Na^+$ and $Ca^{2+}$ ions, there was no signigficant difference in the mobility of CMC-Fe. Also, in the experiments of effect of clay and natural organic mater (NOM) on the mobility of ZVI, there was no significant difference in the mobility of CMC-Fe not only between 1 and 5% clay, but 100 and 1000 mg/L NOM. The results from this work suggests that the CMC-Fe nanoparticles could be easily delivered into the subsurface over a broad range of ionic strength, clay and NOM.

Assessment of Sludge Solubilization by Aeration and Zero-valent Iron As a Pre-treatment for Anaerobic Digestion (공기주입과 영가철을 이용한 하수슬러지 가용화 연구)

  • Kim, Yong-Jun;Park, Jin-Kyu;Tameda, Kazuo;Lee, Nam-Hoon
    • Journal of the Korea Organic Resources Recycling Association
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    • v.24 no.3
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    • pp.53-61
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    • 2016
  • The reaction of zero-valent iron (ZVI) with oxygen can produce reactive oxidants capable of oxidizing organic compounds. Thus, the aim of this study was to investigate the effect of pre-treatment on sludge solubilization by ZVI and aeration. The results demonstrated that the aeration pre-treatment with ZVI method was more effective than the only aeration for improving sludge solubilization, indicating that ZVI increased the extent of sludge solubilization. In addition, removal rate of $NH_3-N$ by ZVI and aeration was found to be 34%, while only aeration was 24%. Thus, ZVI and aeration can be employed as an efficient pre-treatment option to achieve higher sludge solubilization and decrease the toxic effect of $NH_3-N$ for sludge digestion.

The Effect of Fumed Silica on Nitrate Reduction by Zero-valent Iron (흄드 실리카가 영가철에 의한 질산성질소 환원에 미치는 영향)

  • Cho, Dong-Wan;Jeon, Byong-Hun;Kim, Yong-Je;Song, Ho-Cheol
    • Journal of Korean Society of Environmental Engineers
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    • v.32 no.6
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    • pp.599-608
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    • 2010
  • The effect of silica(fumed) on nitrate reduction by zero-valent iron(ZVI) was studied using batch experiment. The reduction of nitrate was tested in three different aqueous media including de-ionized water, artificial groundwater and real groundwater contaminated by nitrate. Kinetics of nitrate reduction in groundwater were faster than those in de-ionized water, and first-order rate constant($k_{obs}$) of ZVI/silica(fumed) process was about 2.5 time greater than that of ZVI process in groundwater. Amendment of Silica(fumed) also decreased ammonium presumably through adsorption on silica surface. The pHs in all processes increased due to oxidation of ZVI, but the increase was lower in groundwater due to buffering capacity of groundwater. The result also showed amount of reduced nitrate increased as initial nitrate concentration increased in groundwater. Separate adsorption isotherm experiments indicated that fumed silica itself had some degree of adsorption capacity for ammonium. The overall results indicated that silica(fumed) might be a promising material for enhancing nitrate reduction by ZVI.

Durability Extension of Fe(0) Column with Shewanella Algae BrY on TCE Treatment (Shewanella algae BrY를 이용한 영가철 칼럼의 TCE 처리 수명연장)

  • Chae, Heehun;Bae, Yeunook;Park, Jae-Woo
    • Journal of the Korean Geoenvironmental Society
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    • v.8 no.2
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    • pp.41-48
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    • 2007
  • Zevo-valent iron (ZVI) has been widely used in permeable reactive barriers for reducing organic contaminants, such as trichloroethylene (TCE). The rapid reaction time, however, leads to decrease in reactivity and availability of ZVI. Shewanella algae BrY, a strain of dissimilatory iron reducing bacteria, can reduce the oxidized Fe (III) to Fe (II) and reduced Fe (II) can be reused to reduce the contaminant. The effect of Shewanella algae BrY on the reduction of the oxidized ZVI column and further TCE removal in the contaminated groundwater were studied at different flow rates and TCE input concentrations in this study. High input concentration of TCE and flow rate increase the amount of input contaminant and make to lower the effect of reduction by Shewanella algae BrY. Specially, the fast flow rate inhibits the direct contact and implantation on the surface of iron. The reduction of oxidized iron reactive barrier by Shewanella algae BrY can decrease the decreation of duration of PRBs by the precipitation of oxidized iron produced by dechlorination of TCE.

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Trichloroethylene Treatment by Zero-Valent Iron and Ferrous Iron with Iron-Reducing Bacteria - Model Development (영가철 및 철환원균을 이용한 2가 산화철 매질에 의한 TCE 제거 연구 - 모델수립)

  • Bae, Yeun-Ook;Kim, Doo-Il;Park, Jae-Woo
    • Journal of Korean Society of Environmental Engineers
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    • v.30 no.11
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    • pp.1146-1153
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    • 2008
  • Numerical simulation was carried out to study the trichloroethylene (TCE) degradation by permeable reactive barrier (PRB), and revealed the effect of concentration of TCE, iron medium mass, and concentration of iron-reducing bacteria (IRB). Newly developed model was based on axial dispersion reactor model with chemical and biological reaction terms and was implemented using MATLAB ver R2006A for the numerical solutions of dispersion, convection, and reactions over column length and elapsed time. The reaction terms include reactions of TCE degradation by zero-valent iron (ZVI, Fe$^0$) and ferrous iron (Fe$^{2+}$). TCE concentration in the column inlet was maintained as 10 mg/L. Equation for Fe$^0$ degradation includes only TCE reaction term, while one for Fe$^{2+}$ has chemical and biological reaction terms with TCE and IRB, respectively. Two coupled equations eventually modeled the change of TCE concentration in a column. At Fe$^0$ column, TCE degradation rate was found to be more than 99% from 60 hours to 235 hours, and declined to less than 1% in 1,365 hours. At the Fe$^{2+}$ and IRB mixed column, TCE degradation rate was equilibrated at 85.3% after 210 hours and kept it constant. These results imply that the ferrous iron produced by IRB has lowered the TCE degradation efficiency than ZVI but it can have higher longevity.http://kci.go.kr/kciportal/ci/contents/ciConnReprerSearchPopup.kci#

Continuous Nitrate Removal using Bipolar ZVI Packed Bed Electrolytic Cell (영가철(Fe0) 충진 복극전해조를 이용한 질산성질소의 연속식 제거 연구)

  • Jeong, Joo-Young;Kim, Han-Ki;Shin, Ja-Won;Park, Joo-Yang
    • Journal of The Korean Society of Civil Engineers
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    • v.32 no.1B
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    • pp.79-84
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    • 2012
  • Nitrate is a common contaminant in groundwater aquifer. The present study investigates the performance of the bipolar zero valent iron (ZVI, $Fe^0$) packed bed electrolytic cell in removing nitrate in different operating conditions. The packing mixture consists of ZVI as electronically conducting material and silica sand as non-conducting material between main cathode and anode electrodes. In the continuous experiments for the simulated wastewater (contaminated groundwater, initial nitrate about 30 mg/L as N and electrical conductivity about 300 ${\mu}S/cm$), over 99% removal of nitrate was achieved in the applied voltage 600 V and at the flow rate of 20 mL/min. The optimum packing ratio (v/v) and flow rate were determined to be 1:1~2:1 (silica sand to ZVI), 30 mL/ min respectively. Effluent pH was proportional to nitrate influx concentration, and ammonia which is the final product of nitrate reduction was about 60% of nitrate influx. Magnetite was observed on the surface of the used ZVI as major oxidation product.

Reductive Degradation of 4-Chlorophenol Compound by Nickel-Coated Zero Valent Iron (니켈로 코팅된 염가금속을 이용한 4-염화페놀의 환원제거율 평가)

  • Shin Seung-Chul;Kim Young-Hun;Ko Seok-Oh
    • Journal of Soil and Groundwater Environment
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    • v.11 no.3
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    • pp.59-65
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    • 2006
  • Reductive dechlorination of chlorophenols by nickel coated iron was investigated to understand the feasibility of using Ni/Fe for the in situ remediation of contaminated groundwater. Zero valent iron (ZVI) was amended with Ni(II) ions to form bimetal (Ni/Fe). Dechlorination of 4-chlorophenol and formation of intermediates was studied using Ni/Fe. Effects of initial contaminant concentration, bimetal loading, presence of humic acid, and solution chemistry were also evaluated. Experimental results showed that Ni/Fe bimetal was so effective that more than 95% of 4-CP degradation was achieved within 240 minutes. Pseudo first-order rate constant for the dechlorination reaction was well correlated with bimetal loading. Humic acid competed for the reactive sites on the nickel coated iron with chlorophenols, lowering the dechlorination efficiency. No significant changes in solution pH were observed in the dechlorination of chlorophenols with Ni/Fe in the absence of buffer, indicating that reactivity of bimetal (Ni/Fe) could be prolonged. Phenol was found as a dechlorination intermediate of the conversion of 4-chlorophenol compound by Ni/Fe.

Stabilization of As (arsenic(V) or roxarsone) Contaminated Soils using Zerovalent Iron and Basic Oxygen Furnace Slag (영가철(Zerovalent Iron)과 제강슬래그를 이용한 비소(V) 및 록살슨(Roxarsone) 오염토양의 비소 안정화 효율 평가)

  • Lim, Jung-Eun;Kim, Kwon-Rae;Lee, Sang-Soo;Kwon, Oh-Kyung;Yang, Jae-E;Ok, Yong-Sik
    • Journal of Korean Society of Environmental Engineers
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    • v.32 no.6
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    • pp.631-638
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    • 2010
  • The objective of this study was to evaluate the efficiency of zerovalent iron and basic oxygen furnace slag on arsenic stabilization in soils. For this, arsenic (V) contaminated soil and roxarsone contaminated soil were incubated after incorporation with zerovalent iron (ZVI) or basic oxygen furnace slage (BOFS) at four different levels (0%, 1%, 3%, and 5%) for 30 days and then the residual concentrations of arsenic were analysed following extraction with aqua reqia, 1N HCl and 0.01 M $CaCl_2$. The total concentration of arsenic was 2,285 mg/kg in the As(V) contaminated soil and 6.5 mg/kg in the roxarsone contaminated soil. 1 N HCl extractable arsenic concentration in the As(V) contaminated soil was initially 1,351 mg/kg and this was significantly declined by 713~1,034 mg/kg following incubation with ZVI while BOFS treatment showed no effect on the stabilization of inorganic arsenate except 5% treatment which showed around 100 mg/kg reduction in 1N HCl extractable arsenic. Similarly, in the roxarsone contaminated soil 1N HCl extractable concentration of arsenic was reduced from 3.13 mg/kg to 0.69 mg/kg with ZVI treatment increased from 1% to 5% while BOFS treatment did not lead to any statistically significant reduction. Available (0.01M $CaCl_2$ extractable) arsenic was initially 0.85 mg/kg in the As(V) contaminated soil and this declined by 0.79 mg/kg following incorporation with 5% ZVI, which accounted for more than 90% of the available As in the control. When As(V)-contaminated soil was treated with BOFS, the available arsenic was increased due to competing effect of the phosphate originated from BOFS with arsenate for the adsorption sites. For the roxarsone contaminated soil, the greater the treatment of ZVI or BOFS, the lower the available arsenic concentration although it was still higher than that of the control.

Synthesis of Oxidation Resistant Core-shell Nanoscale Zero-valent Iron by Controlled Air Contact (공기접촉 제어를 통한 산화방지 Core-Shell 나노영가철의 제조)

  • Ahn, Jun-Young;Kim, Hong-Seok;Hwang, In-Seong
    • Journal of Soil and Groundwater Environment
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    • v.13 no.6
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    • pp.93-102
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    • 2008
  • Experimental studies were conducted to characterize the synthesized nanoscale zero-valent iron (NZVI) which is resistant to oxidation in the atmospheric environment. XRD, XPS, and TEM analyses revealed that the oxidation-resistant NZVI particles formed under various controlled air contact conditions (4, 8 and 12 mL/min) have shells with ${\sim}$5 nm thickness. The shells consist of magnetite (${Fe_3}{O_4}$) and maghemite (${\gamma}-{Fe_2}{O_3}$), predominantly. No substantial differences were found in the shell components and thickness among NZVI particles formed under the various air flow rates. On the other hand, shell was not detected in the TEM image of rapidly oxidized NZVI particles. NZVI particles synthesized under the various air flow rates showed similar TCE degradation performances ($k_{obs}$= 0.111, 0.102, and 0.086 $hr^{-1}$), which are equivalent to approximately 80% of those obtained by the fresh NZVI particles. TCE degradation efficiencies of the NZVI particles(fresh, controlled air contact and rapidly oxidized) were improved after equilibrating with water for one day, indicating that depassivation of the shells occurred. The performances of NZVI particles decreased to 90% and 50% of those of the fresh NZVI particles, when they were equilibrated with the atmosphere for a week and two months, respectively. The NZVI particles synthesized under the controlled air contact would have advantages over traditional NZVI particles in terms of practical application into the site, because of their inertness toward atmospheric oxygen.