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Yoon I.-H.,Korea Atomic Energy Research Institute | Bang S.,Korea Mine Reclamation Corporation MIRECO | Kim K.-W.,Gwangju Institute of Science and Technology | Kim M.G.,Pohang Accelerator Laboratory | And 2 more authors.
Environmental Science and Pollution Research | Year: 2015

In this study, batch experiments were conducted to investigate the effect of the concentration of ferrous [Fe(II)] ions on selenate [Se(VI)] removal using zero-valent iron (ZVI). The mechanism of removal was investigated using spectroscopic and image analyses of the ZVI-Fe(II)-Se(VI) system. The test to remove 50 mg/L of Se(VI) by 1 g/L of ZVI resulted in about 60 % removal of Se(VI) in the case with absence of Fe(II), but other tests with the addition of 50 and 100 mg/L of the Fe(II) had increased the removal efficiencies about 93 and 100 % of the Se(VI), respectively. In other batch tests with the absence of ZVI, there were little changes on the Se(VI) removal by the varied concentration of the Fe(II). From these results, we found that Fe(II) ion plays an accelerator for the reduction of Se(VI) by ZVI with the stoichiometric balance of 1.4 (=nFe2+/nSe6+). Under anoxic conditions, the batch test revealed about 10 % removal of the Se(VI), indicating that the presence of dissolved oxygen increased the kinetics of Se(VI) removal due to the Fe(II)-containing oxides on the ZVI, as analyzed by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS). The X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) spectra also showed that the reductive process of Se(VI) to Se(0)/Se(−II) occurred in the presence of the both ZVI and Fe(II). The final product of iron corrosion was lepidocrocite (γ-FeOOH), which acts as an electron transfer barrier from Fe(0) core to Se(VI). Therefore, the addition of Fe(II) enhanced the reactivity of ZVI through the formation of iron oxides (magnetite) favoring electron transfer during the removal of Se(VI), which was through the exhaustion of the Fe(0) core reacted with Se(VI). © 2015 Springer-Verlag Berlin Heidelberg

Hanh H.T.,Gwangju Institute of Science and Technology | Kim K.-W.,Gwangju Institute of Science and Technology | Bang S.,Korea Mine Reclamation Corporation MIRECO | Hoa N.M.,Can Tho University
Journal of Environmental Monitoring | Year: 2011

We examined the daily inorganic arsenic (i-As) intake from drinking water and rice in 45 households (75 individuals) in the An Giang province, Southern Vietnam. The daily i-As intake ranged from 28-102 μg d -1, equivalent to the daily dose of 0.6-1.9 μg d -1 kg (body wt) -1. Increased As concentrations were observed in human hair in the study location. Approximately 67% (n = 44), 42% (n = 28), and 15% (n = 10) of the hair samples had As levels exceeding 1, 3, and 10 μg g -1, respectively. The total As concentrations in female and male hair correlated well with the total daily i-As intake. Measurement of As concentrations in the hair of people who were consuming or had previously consumed As from contaminated sources may help predict the onset of negative health effects. We suggested an application of the Bayes's theorem to calculate the probability that an individual in a population will acquire a negative health effect, given that the concentration of arsenic in the subject's hair has been determined. © 2011 The Royal Society of Chemistry.

Ko M.-S.,Gwangju Institute of Science and Technology | Kim J.-Y.,Gwangju Institute of Science and Technology | Kim K.-W.,Gwangju Institute of Science and Technology | Lee J.-S.,Korea Mine Reclamation Corporation MIRECO
Understanding the Geological and Medical Interface of Arsenic, As 2012 - 4th International Congress: Arsenic in the Environment | Year: 2012

In this study we find the sulfate reducing bacteria from arsenic contaminated soil and apply arsenic sequestration. The isolated bacteria can be reduced sulfate in the solution and produced black precipitate. In addition, the bacteria metabolize arsenic contaminated condition that is from 1 to 500 μg/L. The black precipitate removed the arsenic in solution and showed 50% of removal efficiency. The pilot scale experiment shows the similar removal efficiency. It suggested that the bacterial reaction controlled to arsenic immobilization and sequestration. © 2012 Taylor & Francis Group.

An J.,Gwangju Institute of Science and Technology | Kim J.-Y.,Gwangju Institute of Science and Technology | Kim K.-W.,Gwangju Institute of Science and Technology | Park J.-Y.,Gwangju Institute of Science and Technology | And 2 more authors.
Environmental Geochemistry and Health | Year: 2011

Mechanisms of natural attenuation of arsenic (As) by wetland plants may be classified by plant uptake and adsorption and/or co-precipitation by iron (oxy)hydroxide formed on the root surface of plants or in rhizosediment. A natural Cattail (Typha spp.) wetland impacted by tailings containing high levels of As from the Myungbong abandoned Au Mine, South Korea was selected, and the practical capability of this wetland to attenuate As was evaluated. The As concentrations in the plant tissues from the study wetland were several-fold higher than those from control wetland. SEM-EDX analyses demonstrated that iron plaques exist on the rhizome surface. Moreover, relatively high As contents bonded with hydrous iron oxides were found in the rhizosediments rather than in the bulk sediments. It was revealed through the leaching and sequential extraction analyses that As existed as more stable forms in the wetland sediment compared with adjacent paddy soil, which is also contaminated with As due to input of mine tailings. The As concentration ratios of extracted solution to sediment/soil represented that the wetland sediment showed significant lower values (10-fold) rather than the paddy soil with indicating high As stability. Also, As in the wetland sediment was predominantly bonded with residual phases on the basis of results from sequential extraction analysis. From these results, it is concluded that transformation of As contaminated agricultural field to wetland environment may be helpful for natural attenuation until active remediation action. © 2010 Springer Science+Business Media B.V.

Jang M.,Korea Mine Reclamation Corporation MIRECO | Lee H.-J.,Korea Mine Reclamation Corporation MIRECO | Shim Y.,Korea Mine Reclamation Corporation MIRECO
Environmental Technology | Year: 2010

The processes of coagulation and flocculation using high molecular weight long-chain polymers were applied to treat mine water having fine flocs of which about 93% of the total mass was less than 3.02 m, representing the size distribution of fine particles. Six different combinations of acryl-type anionic flocculants and polyamine-type cationic coagulants were selected to conduct kinetic tests on turbidity removal in mine water. Optimization studies on the types and concentrations of the coagulant and flocculant showed that the highest rate of turbidity removal was obtained with 10 mg L-1 FL-2949 (coagulant) and 12 mg L-1 A333E (flocculant), which was about 14.4 and 866.7 times higher than that obtained with A333E alone and that obtained through natural precipitation by gravity, respectively. With this optimized condition, the turbidity of mine water was reduced to 0 NTU within 20 min. Zeta potential measurements were conducted to elucidate the removal mechanism of the fine particles, and they revealed that there was a strong linear relationship between the removal rate of each pair of coagulant and flocculant application and the zeta potential differences that were obtained by subtracting the zeta potential of flocculant-treated mine water from the zeta potential of coagulant-treated mine water. Accordingly, through an optimization process, coagulation-flocculation by use of polymers could be advantageous to mine water treatment, because the process rapidly removes fine particles in mine water and only requires a small-scale plant for set-up purposes owing to the short retention time in the process.

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