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Her N.,Korea Army Academy at Young Cheon | Kim J.,Beautiful Environment Construction Co. | Yoon Y.,University of South Carolina
Chemosphere | Year: 2010

Perchlorate has been detected in dairy milk and milk-based powdered infant formula samples from many different provinces of South Korea. A total of 37 dairy milk samples from 12 different brands and 26 milk-based powdered infant formula samples from four different brands were tested for the presence of perchlorate. These brands and their products, which are analyzed in this study, cover over 95% of the dairy milk and milk-based powdered infant formula market share in South Korea, which has a population of approximately 50 million inhabitants. Perchlorate was explicitly detected by ion chromatography tandem mass spectrometry; the limit of quantification (LOQ) for dairy milk and milk-based powdered infant formula was 0.12μgL-1 and 1.0μgkg-1, respectively. The perchlorate concentration in all the samples was above the LOQ. The perchlorate detection data is given as follows: 1.99-6.41μgL-1 (n=37, mean concentration=4.59±0.17μgL-1) for dairy milk and 1.49-33.3μgkg-1 (n=26, mean concentration=7.83±0.22μgkg-1) for milk-based infant formula. This study provides increasing evidence that perchlorate commonly occurs in dairy products, presumably as the result of perchlorate intake by dairy cattle from water and feed. © 2010 Elsevier Ltd.

Jung C.,University of South Carolina | Park J.,North Carolina State University | Lim K.H.,East Carolina University | Park S.,North Carolina State University | And 5 more authors.
Journal of Hazardous Materials | Year: 2013

Chemically activated biochar produced under oxygenated (O-biochar) and oxygen-free (N-biochar) conditions were characterized and the adsorption of endocrine disrupting compounds (EDCs): bisphenol A (BPA), atrazine (ATR), 17 α-ethinylestradiol (EE2), and pharmaceutical active compounds (PhACs); sulfamethoxazole (SMX), carbamazepine (CBM), diclofenac (DCF), ibuprofen (IBP) on both biochars and commercialized powdered activated carbon (PAC) were investigated. Characteristic analysis of adsorbents by solid-state nuclear magnetic resonance (NMR) was conducted to determine better understanding about the EDCs/PhACs adsorption. N-biochar consisted of higher polarity moieties with more alkyl (0-45ppm), methoxyl (45-63ppm), O-alkyl (63-108ppm), and carboxyl carbon (165-187ppm) content than other adsorbents, while aromaticity of O-biochar was higher than that of N-biochar. O-biochar was composed mostly of aromatic moieties, with low H/C and O/C ratios compared to the highly polarized N-biochar that contained diverse polar functional groups. The higher surface area and pore volume of N-biochar resulted in higher adsorption capacity toward EDCs/PhACs along with atomic-level molecular structural property than O-biochar and PAC. N-biochar had a highest adsorption capacity of all chemicals, suggesting that N-biochar derived from loblolly pine chip is a promising sorbent for agricultural and environmental applications. The adsorption of pH-sensitive dissociable SMX, DCF, IBP, and BPA varied and the order of adsorption capacity was correlated with the hydrophobicity (Kow) of adsorbates throughout the all adsorbents, whereas adsorption of non-ionizable CBM, ATR, and EE2 in varied pH allowed adsorbents to interact with hydrophobic property of adsorbates steadily throughout the study. © 2013 Elsevier B.V.

Nam S.-W.,Seoul National University | Choi D.-J.,Seoul National University | Kim S.-K.,Incheon National University | Her N.,Korea Army Academy at Young Cheon | Zoh K.-D.,Seoul National University
Journal of Hazardous Materials | Year: 2014

In this study, we investigated adsorption characteristics of nine selected micropollutants (six pharmaceuticals, two pesticides, and one endocrine disruptor) in water using an activated carbon. The effects of carbon dosage, contact time, pH, DOM (dissolved organic matter), and temperature on the adsorption removal of micropollutants were examined. Increasing carbon dosage and contact time enhanced the removal of micropollutants. Sorption coefficients of hydrophilic compounds (caffeine, acetaminophen, sulfamethoxazole, and sulfamethazine) fit a linear isotherm and hydrophobic compounds (naproxen, diclofenac, 2, 4-D, triclocarban, and atrazine) fit a Freundlich isotherm. The removal of hydrophobic pollutants and caffeine were independent of pH changes, but acetaminophen, sulfamethazine, and sulfamethoxazole were adsorbed by mainly electrostatic interaction with activated carbon and so were affected by pH. The decrease in adsorption removal in surface water samples was observed and this decrease was more significant for hydrophobic than hydrophilic compounds. The decline in the adsorption capacity in surface water samples is caused by the competitive inhibition of DOM with micropollutants onto activated carbon. Low temperature (5. °C) also decreased the adsorption removal of micropollutants, and affected hydrophobic compounds more than hydrophilic compounds. The results obtained in this study can be applied to optimize the adsorption capacities of micropollutants using activated carbon in water treatment process. © 2014 Elsevier B.V.

Im J.-K.,University of South Carolina | Im J.-K.,National Water Research Institute | Yoon J.,Korea Institute of Energy Research | Her N.,Korea Army Academy at Young Cheon | And 3 more authors.
Separation and Purification Technology | Year: 2015

Immobilized TiO2 nanotube (NT) arrays containing anatase phases were synthesized through electrochemical oxidation of TiO2 foil. At ultrasonic (US) frequencies of 28 and 1000 kHz, the feasibility of the use of TiO2 NTs was investigated in terms of the production of H2O2 and the degradation of acetaminophen (AAP) and naproxen (NPX), which are pharmaceuticals (PhACs) used for pain relief and which persist despite wastewater treatment. The degradation efficiencies of the PhACs, as well as the production of H2O2, were enhanced in the presence of TiO2 NTs. Furthermore, the reduction of TiO2 slurries after the reaction was achieved at 1000 kHz. The feasibility of the TiO2 NTs was clearly shown in US/Fenton/TiO2 NT process, exhibiting the highest degradation (85.3% for AAP and 96.0% for NPX) at low Fe2+:H2O2 ratio of 20:4 ratio at 1000 kHz. These results could be attributed to the accelerated cycling of Fe2+-Fe3+, assisted by electrons in the presence of TiO2 NTs under US irradiation. In the US/CCl4 process, the degradation rates of both PhACs were improved with an increased concentration of CCl4, implying that the scavenging H leads to high concentrations of OH and the accumulation of reactive chlorine species, while t-BuOH notably inhibited the degradation of the PhACs. In acidic conditions, high degradation efficiencies were observed because of the hydrophobicity of the PhACs, high OH activity, and high HOCl/OCl- ratio. Finally, we suggest possible process mechanisms of the US/Fenton/TiO2 NT and US/CCl4 processes. © 2014 Elsevier B.V. All rights reserved.

Son C.,Korea Army Academy at Young Cheon | Geum Y.,Seoul National University | Park Y.,Seoul National University
Expert Systems with Applications | Year: 2013

Recently, due to the explosive increase of services, firms have faced with challenges to analyze patterns and trends in services in an intuitive but objective ways. The notion of service map can be adapted to this end. Maps, in general, have been receiving a great deal of attention because of their potential as visualization tools that can allow people to visualize massive amounts of information. Specifically, the generative topographic mapping through time (GTM-TT) algorithm is suitable for dynamic analysis since GTM-TT provides a time-based clustering and change path. In response, this study proposes an approach for developing and using GTM-TT service maps consisting of a service clustering map and a service sequence map for analyzing service trends. The proposed approach, broadly, is comprised of four steps: (1) the construction of a database, (2) data preprocessing, (3) development of a GTM-TT service map, and (4) interpretation. The proposed approach is expected to aid in the identification of dynamic service trends. © 2013 Elsevier B.V. All rights reserved.

Her N.,Korea Army Academy at Young Cheon | Jeong H.,Korea Army Academy at Young Cheon | Kim J.,Beautiful Environment Construction Co. | Yoon Y.,University of South Carolina
Archives of Environmental Contamination and Toxicology | Year: 2011

Concentrations of perchlorate were determined by both liquid- chromatography-mass spectrometry (LC-MS) and ion chromatography tandem mass spectrometry (IC-MS/MS) in 520 tap-water, 48 bottled-water, and 9 seawater samples obtained or purchased from >100 different locations in South Korea. The method detection limits were 0.013 μg/L for LC-MS and 0.005 μg/L for IC-MS/MS, and the limits of quantification (LOQs) were 0.10 μg/L for LC-MS and 0.032 μg/L for IC-MS/MS. Perchlorate was detected in most (80%) of the tap-water samples, with concentrations higher than the LOQ; the concentrations ranged from <1.0 to 6.1 μg/L (mean 0.56). Perchlorate was detected by IC-MS/MS in many (n = 23) of the bottled-water samples, with concentrations higher then the LOQ, ranging from 0.04 to 0.29 μg/L (mean 0.07 ± 0.01). The concentrations of perchlorate in all seawater samples collected from the various locations were higher than the LOQ, with a mean concentration of 1.15 ± 0.01 μg/L (maximum 6.11 and minimum 0.11). This study provides further evidence that drinking-water sources have been contaminated by perchlorate. To the best of our knowledge, this is the first comprehensive study on perchlorate assessment in drinking water and seawater in South Korea. © 2010 Springer Science+Business Media, LLC.

Park J.-S.,Korea Army Academy at Young Cheon | Her N.,Korea Army Academy at Young Cheon | Yoon Y.,University of South Carolina
Desalination and Water Treatment | Year: 2011

This study examined the relative degradation of commonly known endocrine-disrupting compounds (EDCs) such as bisphenol A (BPA), 17β-estradiol (E2), and 17α-ethinyl estradiol (EE2) in single-component aqueous solution using 28, 580, and 1,000 kHz ultrasonic reactors. The degradation of EDCs follows a pseudo-first order rate kinetics; the order of degradation is EE2 ≥ BPA > E2. At different frequencies, the degradation of these compounds follows the order 580 kHz (92-97%) > 1,000 kHz (90-94%) > 28 kHz (62-67%) at an initial concentration of 1 mM of each compound with a contact time of 30 min. Additional experiments were performed to determine the effects of carbon tetrachloride (CCl4, H• scavenger) and tert-butyl alcohol (t-BuOH, HO• scavenger) on BPA, E2, and EE2 degradation at 580 kHz with a reaction time of 30min. The addition of t-BuOH slightly decreased the rate of BPA degradation as follows: no addition (97%), 0.01 mM (96%), and 0.1 mM (95%). At high t-BuOH concentrations of 1, 10, and 100 mM, the degree of degradation was significantly decreased; that is, the degradation decreased to 90%, 33%, and 20%, respectively. However, in the presence of CCl4, the BPA degradation increased as follows: no addition (97%), 0.01/0.1 mM (98%), 1 mM (99.7%), and 10 mM (99.8%). © 2011 Desalination Publications. All rights reserved.

Heo J.,University of South Carolina | Flora J.R.V.,University of South Carolina | Her N.,Korea Army Academy at Young Cheon | Park Y.-G.,Korea Institute of Energy Research | And 3 more authors.
Separation and Purification Technology | Year: 2012

The retention and adsorption of bisphenol A (BPA) and 17β-estradiol (E2) were examined using three commercially available ultrafiltration (UF) membranes. A stirred cell operated within a batch dead-end stirred cell was employed to study the solute retention and the membrane flux of solutions both in the absence and presence of natural organic matter (NOM) and single-walled carbon nanotubes (SWNTs). The batch adsorption and stirred-cell filtration experiments indicated that adsorption was an important mechanism for the retention of hydrophobic compounds and was dependent on the octanol-water partition coefficient. The results also suggested that BPA and E2 transport was influenced by NOM, which fouls the membrane through pore blockage and cake/gel formation. The NOM fouling was presumably attributed to the adsorptive hydrophobic interactions, which decreased the membrane pore size and caused the flux decline. A strong linear correlation between the retention and adsorption of BPA and E2 was observed, indicating that retention by the UF membranes was mainly due to the adsorption of BPA and E2 onto the membrane, the SWNTs, and/or the NOM. Size-exclusion is unlikely to be a key factor in the retention of E2, however, BPA retention showed a slight dependence on the membrane pore size. © 2012 Elsevier B.V. All rights reserved.

Park J.-S.,Korea Army Academy at Young Cheon | Her N.,Korea Army Academy at Young Cheon | Oh J.,Chung - Ang University | Yoon Y.,University of South Carolina
Separation and Purification Technology | Year: 2011

This study explores the sonochemical reactivity and the degradation of bisphenol A (BPA) and 17α-ethinyl estradiol (EE2) in a newly designed sonochemical reactor in the presence of a stainless steel wire mesh (SSWM), which acted as a catalyst, at a low frequency of 28 kHz with a contact time of 60 min. The sonochemical efficiency based on H2O2 production and the degradation of BPA and EE2 were determined as a function of the SSWM position, area, pore size, setting height, liquid height, and power. The degradation of BPA and EE2 due to H2O2 production was significantly higher when the SSWM was placed in a horizontal position than in a vertical position. The formation of H2O2 was found to be dependent on the SSWM setting height; the highest zero-order rate constant was obtained at a height of 3.6 cm from the bottom of the reactor. The sonochemical reactivity increases significantly in the presence of the SSWM, ranging from 18.5 μM when there is no addition of SSWM to 61.3 μM for a pore size of 1.0 mm. For a given SSWM pore size of 1.0 mm, the sonochemical reactivity and the degradation of BPA and EE2, as a function of the SSWM area, followed the order: 128 cm2 > 192 cm2 > 384 cm2 > no addition. © 2011 Elsevier B.V. All rights reserved.

Yang M.,Korea Army Academy at Young Cheon | Her N.,Korea Army Academy at Young Cheon
Journal of Agricultural and Food Chemistry | Year: 2011

The occurrence of perchlorate in soybean sprouts (Glycine max L. Merr), water dropwort (Oenanthe stolonifera DC.), and lotus (Nelumbo nucifera Gaertn.) root, which are commonly consumed by people in South Korea, was determined by using an ion chromatograph coupled with a tandem mass spectrometer. For soybean sprouts (11 samples), perchlorate was detected in most (91%) of the samples at various concentrations of up to 78.4 μg/kg dry weight (DW); the mean concentration was 35.2 μg/kg DW. For water dropwort, of the 13 samples examined, four showed concentrations that were above the limit of quantification (LOQ). The mean perchlorate concentration was 20.7 μg/kg DW, and the highest perchlorate value was 39.9 μg/kg DW. Of the six lotus root samples examined, only one exhibited a detectable perchlorate concentration (17.3 μg/kg DW). For the accumulation experiments with artificially contaminated solutions, the concentrations of perchlorate in soybean sprouts gradually increased with the increase of perchlorate concentration in the solution. However, there was a decrease in the bioconcentration factor as the perchlorate concentration in the solution increased. © 2011 American Chemical Society.

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