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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. Source

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. Source

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. Source

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. Source

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. Source

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