• Bulletin of the Korean Chemical Society
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• v.30 no.6
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• pp.1394-1396
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• 2009

• Environmental Engineering Research
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• v.15 no.3
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• pp.149-156
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• 2010

The objective of this study was to investigate microbial removal using layered double hydroxides (LDHs) and iron (hydr)oxides (IHs) immobilized onto granular media. Column experiments were performed using calcium alginate beads (CA beads), LDHs entrapped in CA beads (LDH beads), quartz sand (QS), iron hydroxide-coated sand (IHCS) and hematite-coated sand (HCS). Microbial breakthrough curves were obtained by monitoring the effluent, with the percentage of microbial removal and collector efficiency then quantified from these curves. The results showed that the LDH beads were ineffective for the removal of the negatively-charged microbes (27.7% at 1 mM solution), even though the positively-charged LDHs were contained on the beads. The above could be related to the immobilization method, where LDH powders were immobilized inside CA beads with nano-sized pores (about 10 nm); therefore, micro-sized microbes (E. coli = 1.21 ${\mu}m$) could not diffuse through the pores to come into contact with the LDHs in the beads, but adhere only to the exterior surface of the beads via polymeric interaction. IHCS was the most effective in the microbial removal (86.0% at 1 mM solution), which could be attributed to the iron hydroxide coated onto the exterior surface of QS had a positive surface charge and, therefore, effectively attracted the negatively-charged microbes via electrostatic interactions. Meanwhile, HCS was far less effective (35.6% at 1 mM solution) than IHCS because the hematite coated onto the external surface of QS is a crystallized iron oxide with a negative surface charge. This study has helped to improve our knowledge on the potential application of functional granular media for microbial removal.

• Journal of Soil and Groundwater Environment
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• v.19 no.1
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• pp.63-69
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• 2014

This paper presents the feasibility of using different iron oxides (microscale hematite (HT), microscale magnetite (MT), and nanoscale maghemite (NMH)) in enhancing nitrate reduction by zero-valent iron (Fe(0)) under two solution conditions (artificial acidic water and real groundwater). Addition of MT and NMH into Fe(0) system resulted in enhancement of nitrate reduction compared to Fe(0) along reaction, especially in groundwater condition, while HT had little effect on nitrate reduction in both solutions. Field emission scanning electron microscopy (FESEM) analysis showed association of MT and NMH with Fe(0) surface, presumably due to magnetic attraction. The rate enhancement effect of the minerals is presumed to arise from its role as an electron mediator that facilitated electron transport from Fe(0) to nitrate. The greater enhancement of MT and NMH in groundwater was attributed to surface charge neutralization by calcium and magnesium ions in groundwater, which in turn facilitated adsorption of nitrate on Fe(0) surface.

• Clean Technology
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• v.16 no.3
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• pp.162-171
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• 2010

The objective of this study is to develop cleaning agents for the indoor water supply pipe which is environmentally friendly and suitable for removing scale by using various organic acids, inorganic acids, and some additives. Among various organic acids, oxalic acid, citric acid, and malic acid showed good cleaning efficiency of iron oxides which were main components of the indoor water supply pipe scale. Several cleaning agents were formulated by adding chemical additives into these organic acids and evaluated for removal of iron oxides. In this study, it was found that nonionic surfactants were excellent for the removal of iron oxide scale among various additives. Two types of cleaning agents($F_1$, $F_2$) with comparatively high solvent power for iron oxides were formulated in this study. The cleaning agents $F_1$ made by organic acids and some additives were formulated to be safe and environmentally friendly, but seemed to have disadvantage due to their comparatively low cleaning efficiency of iron oxide than $F_2$. But, the cleaning agents $F_2$ prepared by adding inorganic acid a little to $F_1$ showed comparatively good cleaning efficiency of iron oxide and could be recommended for removing hard scale of iron oxides in the indoor water supply pipe. Thus, it is considered that the formulated cleaning agents should be selected based on the extent of scale in the indoor water supply pipe.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.2
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• pp.66-69
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• 2009

The compositional dependence of bismuth iron oxides and effect of La-substitutions in the structure of $BiFeO_3$ compounds were investigated, which compounds were synthesized by conventional ceramic processing. It is shown that some of bismuth iron oxides including $BiFeO_3$ show the narrow single phase region. The effect of La-doping in $BiFeO_3$ was presented as disappearance of many impurity phases of Bi-Fe-O compounds. The lower electrical resistivity was obtained as those compositions of Fe deficient region and La-doped $BiFeO_3$. The saturation magnetization of La-doped $BiFeO_3$ was increased with La content. The dielectric dispersion was also observed for those Bi-Fe-O compounds with Fe deficient and La-doped $BiFeO_3$ at low frequencies under 1 kHz.

• Journal of Soil and Groundwater Environment
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• v.21 no.1
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• pp.40-48
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• 2016

A siderophore-producing bacterium (i.e., Pseudomonas aeruginosa) capable of chelating Fe³⁺ from its mineral form (i.e., iron oxides) was used to enhance As uptake by plants. Since As in soil is mainly associated with iron oxides, siderophore can play an important role in As mobilization through the dissolution of As-bearing iron oxides. A series of pot experiment using Pteris cretica showed that As removal by P. cretica with siderophore-producing bacteria addition increased more than three times compared to that without bacteria addition. Competition between indigenous bacteria and introduced bacteria (i.e., P. aeruginosa) was also observed, but such competition seemed not to be significant. This study suggests that enhanced-phytoremediation by siderophore-producing bacteria addition could be a visible option for longterm As removal in the forest area at the former Janghang smelter site.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.4
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• pp.571-578
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• 2004

The purpose of this study is to estimate of emission factors of the air pollutants for the melting furnaces for the iron and steel industry. The result of this study is able to obtaine the emission factor of particulate matters (PM), sulfur dioxide. nitrogen oxides for melting furnace. The emission factors of each pollutants were as follows : - the emission factor varied between 6.13E-03~6.12E-01 kg/ton for PM -1.59E-01~2.45E+00kg/ton for $SO_2$ - 6.82E-02~6.88E-01 kg/ton for NOx, respectively. Analysis of the differences in the emission factors of ours and U.S. EPA's yielded the following results for the Wilcoxon method : p>0.05. The statistical analysis showed no differences in the our emission factors and U.S. EPA's

• Journal of Soil and Groundwater Environment
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• v.19 no.2
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• pp.16-24
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• 2014

To test the potential effects of extracellular electron shuttles (EES) on the rate and extent of heavy metal release from contaminated soils during microbial iron reduction, we created anaerobic batch systems with anthraquinone-2,6-disulfonate (AQDS) as a surrogate of EES, and with contaminated soils as mixed iron (hydr)oxides and microbial sources. Two types of soils were tested: Zn-contaminated soil A and As/Pb-contaminated soil B. In soil A, the rate of iron reduction was fastest in the presence of AQDS and > 3500 mg/L of total Fe(II) was produced within 2 d. This suggests that indigenous microorganisms can utilize AQDS as EES to stimulate iron reduction. In the incubations with soil B, the rate and extent of iron reduction did not increase in the presence of AQDS likely because of the low pH (< 5.5). In addition, less than 2000 mg/L of total Fe(II) was produced in soil B within 52 d suggesting that iron reduction by subsurface microorganisms in soil B was not as effective as that in soil A. Relatively high amount of As (~500 mg/L) was released to the aqueous phase during microbial iron reduction in soil B. The release of As might be due to the reduction of As-associated iron (hydr)oxides and/or direct enzymatic reduction of As(V) to As(III) by As-reducing microorganisms. However, given that Pb in liquid phase was < 0.3 mg/L for the entire experiment, the microbial reduction As(V) to As(III) by As-reducing microorganisms has most likely occurred in this system. This study suggests that heavy metal release from contaminated soils can be strongly controlled by subsurface microorganisms, soil pH, presence of EES, and/or nature of heavy metals.

• Advances in materials Research
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• v.13 no.3
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• pp.161-171
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• 2024

This study aimed to investigate the effect of physicochemical properties and mix ratios of iron ore (oxide feed): coke (reductant) on the carbothermic reductions of iron ore. Coke size was fixed at ≤63 ㎛ while iron ore size varied between 150-63 ㎛ and ≤63 ㎛ respectively. Mix ratios were changed from 100:0 (reference) to 80:20 and 60:40 while the temperature, heating rate and soaking duration in muffle furnace were fixed at 1100 ℃, 10 ℃/min and 1 hour. Particle size analyzer, XRF, CHNS and XRD analyses were used for determination of raw feed characteristics. The occurrence of phase transformations from various forms of iron oxides to iron during the carbothermal reductions were identified through XRD profiles and supported with weight loss (%). XRF analysis proved that iron ore is of high grade with 93.4% of Fe₂O₃ content. Other oxides present in minor amounts are 2% Al₂O₃ and 1.8% SiO₂ with negligible amounts of other compounds such as MnO, K₂O and CuO. Composite pellet with finer size iron particles (≤63 ㎛) and higher carbon content of 60:40 exhibited 45.13% weight lost compared to 32.30% and 3.88% respectively for 80:20 and 100:0 ratios. It is evident that reduction reactions can only occur with the presence of coke, the carbon supply. The small weight loss of 3.88% at 100:0 ratio occurs due to the removal of moisture and volatiles and oxidations of iron ore. Higher carbon supply at 60:40 leads into better heat and mass transfer and diffusivity during carbothermic reductions. Overall, finer particle size and higher carbon supply improves reactivity and gas-solid interactions resulting in increased reductions and phase transformations.

• Bulletin of the Korean Chemical Society
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• v.15 no.11
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• pp.1023-1024
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• 1994