• Environmental Engineering Research
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• v.16 no.4
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• pp.187-203
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• 2011

Chlorophenols (CPs) are widely used industrial chemicals that have been identified as being toxic to both humans and the environment. Zero valent iron (ZVI) and iron based bimetallic systems have the potential to efficiently dechlorinate CPs. This paper reviews the research conducted in this area over the past decade, with emphasis on the processes and mechanisms for the removal of CPs, as well as the characterization and role of the iron oxides formed on the ZVI surface. The removal of dissolved CPs in iron-water systems occurs via dechlorination, sorption and co-precipitation. Although ZVI has been commonly used for the dechlorination of CPs, its long term reactivity is limited due to surface passivation over time. However, iron based bimetallic systems are an effective alternative for overcoming this limitation. Bimetallic systems prepared by physically mixing ZVI and the catalyst or through reductive deposition of a catalyst onto ZVI have been shown to display superior performance over unmodified ZVI. Nonetheless, the efficiency and rate of hydrodechlorination of CPs by bimetals depend on the type of metal combinations used, properties of the metals and characteristics of the target CP. The presence and formation of various iron oxides can affect the reactivities of ZVI and bimetals. Oxides, such as green rust and magnetite, facilitate the dechlorination of CPs by ZVI and bimetals, while oxide films, such as hematite, maghemite, lepidocrocite and goethite, passivate the iron surface and hinder the dechlorination reaction. Key environmental parameters, such as solution pH, presence of dissolved oxygen and dissolved co-contaminants, exert significant impacts on the rate and extent of CP dechlorination by ZVI and bimetals.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.8
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• pp.892-899
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• 2005

Groundwater is naturally of excellent microbiological qualify and generally of adequate quality for drinking water use. However, recently, the impact of urbanization and intensification of agricultural production have led to serious deterioration in groundwater quality. The representative SOCs used in this study were trichloroethylene (TCE) and tetrachloroethylene (PCE). Powdered activated carbon (PAC) is widely used for SOCs removal. The overall goal of this study was to demonstrate the feasibility of using a hybrid use of PAC-UF and PAC-MF processes for treating groundwater contaminated with TCE and PCE. The results show that the flux decline rate was lower for the PAC-UF or PAC-MF process than for UF or MF only process. Therefore, applying PAC before UF or MF membrane filtration showed not only enhancing the removal of TCE and PCE, but also reducing membrane fouling.

• Journal of Environmental Health Sciences
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• v.26 no.2
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• pp.97-107
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• 2000

PCBs [Polychlorinated biphenyls] are halogenated aromatic compounds with the empirical formula C12H10-nCln(n=1~10), and are a mixture of possible 209 different chlorinated congeners. PCBs were widely used as dielectric fluids for capacitors, transformers, plasticizers, lubricant inks, and paint additives. once released into the environment, PCBs persist for years because they are so resistant to degradation. In addition to their high degree of lipophilicity. In 1970s, the worldwide production of PCBs seem to be still in use. The environmental load of PCBs was prohibited since 1983 in Korea. In spite of these actions, many PCBs seem to be still in use. The environmental load of PCBs will continue to be recycled through air, land, water, and the biosphere for decades to come. This study was conducted to measure the concentrations of PCBs I the serum samples of 112 women by GC/MSD(Hewlett Packard 5897 Gas Chromatography-Mass Chromatography Detector) and CG/ECD(Hewlett Packard 5890 series-II gas chromatography-Electron capture detector, U.S.A). The main results of this study were as follows; The mean and standard deviation of serum PCBs were 3.613, 0.759 ppb, respectively and median of it was 3.828 ppb. The correlation coefficients of the concentrations of 13 PCB congeners ranged from 0.7913 to 0..9985 and were significantly correlated between each items(p=0.0001). The PCB concentrations were positively associated with age(simple linear regression; R2=0.86, =0.08023, p<0.001) and with total lipids in serums(simple linear regression; R=0.7058, =0.00486, p<0.001). The age adjusted model (Y=$\beta$0+$\beta$1age+$\beta$2X) was applied for possible predictors of PCBs levels in serum. For BMI(Body Mass Index), major residential area, and fish, meat, and dairy consumption, there was no association with PCBs levels, Also there was negative association for the number of pregnancy and lactation period with PCBs levels.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.3292-3297
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• 2014

The vehicle wiper blade(W/B) to lower the friction coefficient of the rubber surface after the surface treatment with chlorine were investigated. IR spectrum from W/B was used to determine the extent of chlorination of the rubber surface. Coefficient of friction is significantly reduced by the treatment with chlorine. In particular, the more sensitive influence on the initial chlorination. Rubber surface properties with respect to the longitudinal direction of the cutting plane were obtained by EPMA line analysis results. Penetration depth by EPMA chlorine concentration($20.0{\ell}$ of water for 35.0% hydrochloric acid(HCl) $300m{\ell}$ with 5.25% sodium hypochlorite(NaOCl) $400m{\ell}$), the chlorine treatment for 5 minutes was conducted to find that after 1.2 ${\mu}m$.

• Journal of Soil and Groundwater Environment
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• v.27 no.6
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• pp.47-57
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• 2022

A number of different methods have been used for modeling the sorption of volatile organic chlorinated compounds such as tetrachloroethylene/perchloroethylene (PCE). In this study, PCE was adsorbed in several natural sorbents, i.e., Pahokee peat, vermicompost, BionSoil^®, and natural soil, in the batch experiments. Several sorption models such as linear, Freundlich, solubility-normalized Freundlich model, and Polanyi-Manes model (PMM) were used to analyze sorption isotherms. The relationship between sorption model parameters, organic carbon content (f_oc), and elemental C/N ratio was studied. The organic carbon normalized partition coefficient values (log K_oc = 1.50-3.13) in four different sorbents were less than the logarithm of the octanol-water partition coefficient (log K_ow = 3.40) of PCE due to high organic carbon contents. The log K_oc decreased linearly with log f_oc and log C/N ratio, but increased linearly with log O/C, log H/C, and log (N+O)/C ratio. Both log K_F,oc or log K_F,oc decreased linearly with log f_oc (R² = 0.88-0.92) and log C/N ratio (R² = 0.57-0.76), but increased linearly with log (N+O)/C (R² = 0.93-0.95). The log q_max,oc decreased linearly as log f_oc and log C/N increased, whereas it increased with log O/C, log H/C and log (N+O)/C ratios. The log q_max,oc increased linearly with (N+O)/C indicating a strong dependence of q_max,oc on the polarity index. The results showed that PCE sorption behaviors were strongly correlated with the physicochemical properties of soil organic matter (SOM).

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.97-108
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• 2023

Two carbonaceous adsorbents CAT and CARBOPAL were tested for reducing the concentration of the three herbicides in water: 2,4-D (2,4-dichlorophenoxyacetic acid), TCP (2,4,6-trichlorophenol) and metolachlor. Textural and chemical characterization of the adsorbents include nitrogen isotherms, FTIR, titration and thermogravimetric analyses. Adsorption was studied in discontinuous adsorption experiments at different pH values. The experimental adsorption isotherms data were fitted to four theoretical models. Adsorbent characterization reveals that CAT has higher micropore area, lower pore diameter and lower acidity than CARBOPAL. The adsorption is a second-order process and the isotherms best fitted to Sips model. The efficiency of the process depends mainly on the charge of the adsorbate for TCP and 2,4-D, but it depends on the charge of the surface for metolachlor. Adsorption capacity is higher on CAT for 2,4-D and TCP (small molecules), and it is higher on CARBOPAL for metolachlor (large molecules). Theoretical calculations clearly support this assumption.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.27 no.4
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• pp.340-360
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• 1982

Because of the continuing rapid increase in pesticide usage in Taiwan, much attention has been focus on pesticide contamination of food and effect of pesticides on human and environmental health. The Plant Protection Center (PPC) conducts safety evaluation of pesticides usee! in Taiwan. The pesticides are classified into different groups based on their acute toxicities. Pesticides which are classified into extremely toxic group are not allow to used on short term crops or the continuously harvest crops. The acute toxicity of pesticides to the beneficial insects are also studied, special attention has been paid to the two predators of rice brown planthopper. 60% of cultivated land in Taiwan are paddy field; therefore, acute fish toxicity was taken into consideration when a pesticide was applied for registration to be used in the paddy. Fish toxicities were evaluated by the dangerous rating value which is the amount of pesticide residue in the field water over the TLM value. Mutagenicity of pesticides was continuously evaluated by using Arne's microbial testing method. Island wide survey of residual levels of pesticides of known pollutants such as chlorinated hydrocarbon . insecticides, mercurial compounds in soil, water and biological samples were carried out constantly. The potential of a new1y Imported esticides to pollute the environment were studied by using model ecosystem. Ecological magnification (EM) of a chemical was calculated from model ecosystem. A chemical was considered as a pollutant when its EM value over 5000. In order to ensure the levels of pesticides residue of the crop within the safety limit. The 'tolerance' of pesticides on different crop groupings were established base on 1) acceptable daily intake value of individual pesticides, 2) average daily consumption of each crop groupings by Chinese person, 3) Actual residues of pesticides. on different crops obtained from supervised trials. Total about 79 pesticides for which the tolerances have been established on different crop groupings. Because the intensive agricultural system was adopted in Taiwan. The phytotoxicity of pesticides to the non-target crops was therefore become one of the important factor in the safety evaluation of pesticide usage. These will include 1) direct injury, 2) injury caused by pesticide polluted irrigation water, 3) injury caused by the pesticide polluted soil, 4) reduction of growth caused by the effect of pesticide on the soil microorganisms. This paper will reviewed all the aspects mentioned in the previous .paragraphs. Most the works have done in Taiwan by the PPC.y the PPC.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.10
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• pp.1031-1037
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• 2006

The main purposes of this study were to compare the characteristics of fractionated natural organic matters(NOM) from Han River water and Wangsuk(W) stream water, and to investigate the relationships between NOM and the formation of disinfection by products(DBPs). Three types of resin such as XAD-4, XAD-7HP and IRC-50 were used to isolate the water samples into three organic fractions. The DOC concentrations of raw waters were relatively low($1.5{\sim}3.3$ mg/L) at all seasons. The hydrophilic was the major constituent, contributing $44{\sim}63%$ of the total NOM and hydrophobic $21{\sim}33%$, transphilic $16{\sim}31%$, respectively. The formation of trihalomethans(THMs) was highly influenced by particulated NOM especially in the rainy season, whereas haloaceticacid forming potentials(HAAFPs) depended more on the hydrophilic fraction of dissolved NOM which is known to be difficult to be removed through conventional processes. The NOM of W stream was characterized as 15% hydrophobic, 9% transphilic, and 76% hydrophilic. In the fractionation of NOM using resins, $20{\sim}40%$ of the NOM in W tributary water could not be clearly isolated, whereas, 85% of the NOM in the raw water was recovered. Although the DOC concentration of tributary water was higher than the raw waters from the Han River, the DBPFPs was approximately 40% of the raw waters. In DBPFPs aspect, W stream has less effect than Han River water itself. Bromide in tributary waters discharged from waste water treatment plants has been found to shift the distribution of THMs and HANs to the more brominated DBPs.

• Journal of Korean Society on Water Environment
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• v.23 no.5
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• pp.712-722
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• 2007

This study screened three natural ores (iron, mangenase, and zinc), two types of slags, and two elemental metals (elemental iron and zinc) to evaluate transformation characteristics of CAH mixtures [e.g. Carbontetrachloride (CT), 1,1,1-Trichloroethane (1,1,1-TCA), and Perchloroethene (PCE)]. To select an effective metal medium to treat the CAH mixtures, we measured transformation capacities (CAH mass ultimately transformed/mass of metal added) and the degree of dechlorination. We also considered economical efficiency of the metal media by comparing the value, CAH mass ultimately transformed divided by the price of metal medium added. A simplified mathematical model adapting CAH transformation capacity, first-order transformation kinetics, and available mass of metal transforming CAH was developed and used for estimating CAH transformation rate coefficient and longevity of the metal medium. CAH transformation capacity for elemental iron and elemental zinc were 4258~7129 and $4215{\sim}6330{\mu}g\;CAH\;transformed/g$ metal added, respectively, which are a factor of 80~200 higher than slags and natural ores. They also showed a factor of 1.1 to 2.2 greater degree of dechlorination than the others. Among natural ores and slags, Zinc ore showed the highest transformation capacity, $47{\sim}53{\mu}g\;CAH\;transformed/g$ metal added. Although zinc ore have smaller transformation capacity than elemental metals, economical efficiency of zinc ore is a factor of 10~20 greater than elemental metals tested. Consequently, zinc ore would be more economical medium than the others tested in this study. We estimated the pseudo first-order transformation rate of zinc ore was in the order of CT > 1,1,1-TCA > PCE.

• Journal of Environmental Science International
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• v.14 no.2
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• pp.221-230
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• 2005

Catalytic wet oxidation of trichloroethylene (TCE) in water has been conducted using $TiO_2-supported$ cobalt oxides at $36^{\circ}C$ with a weight hourly space velocity of $7,500\;h^{-1}.\;5\%\;CoO_x/TiO_2$, prepared by using an incipient wetness technique, might be the most promising catalyst for the wet oxidation although it exhibited a transient behavior in time on-stream activity. Not only could the bare support be inactive for the wet decomposition reaction, but no TCE removal also occurred by the process of adsorption on $TiO_2$ surface. The catalytic activity was independent of all particle sizes used, thereby representing no mass transfer limitation in intraparticle diffusion. XPS spectra of both fresh and used Co surfaces gave different surface spectral features for each $CoO_x,\;Co\;2P_{3/2}$ binding energy for Co species in the fresh catalyst appeared at 781.3 eV, which is very similar to the chemical states of $CoTiO_x$ such as $CO_2TiO_4\;and\;CoTiO_3$. The used catalyst exhibited a 780.3-eV main peak with a satellite structure at 795.8 eV. Based on XPS spectra of reference Co compound, the TCE-exposed Co surfaces could be assigned to be in the form of mainly $Co_3O_4$. XRD patterns for $5\%\;CoO_x/TiO_2$ catalyst indicated that the phase structure of Co species in the catalyst even before reaction is quite comparable to the diffraction lines of external $Co_3O_4$ standard. A model structure of $CoO_x$ present predominantly on titania surfaces would be $Co_3O_4$, encapsulated in thin-film $CoTiO_x$ species consisting of $Co_2TiO_4$ and $CoTiO_3$, which may be active for the decomposition of TCE in a flow of water.