• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.4
• /
• pp.402-408
• /
• 2005

This investigation aimed at selecting the optimum catalyst and reaction conditions used in Fenton oxidation for landfill leachate treatment and was carried out at ambient temperature using a lab-scale experiment. The investigation led to the following results: 1) The optimum pH and dose for each iron catalyst were as follows: $Fe^{2+}\;=\;1,200\;mg/L$, $H_2O_2\;=\;1,200\;mg/L$, initial pH=3.0; $Fe^{3+}\;=\;1,200\;mg/L$, $H_2O_2\;=\;1,500\;mg/L$, initial pH=4.5; $Fe^0\;=\;1,200\;mg/L$, $H_2O_2\;=\;900\;mg/L$, initial pH=4.0, respectively. 2) The progress of Fenton oxidation could be instrumentally monitored by measuring redox potential evolution during leachate oxidation, thus, indicating the possibility of an on-line process monitoring. 3) A simple acid-base titration of Fenton-treated leachate proved that a relevant fraction of by- products formed during the treatment was made of acidic compounds in the optimum reaction condition for each catalyst used, thus demonstrating that the higher the extent of Fenton oxidation the greater was the amount of acids formed. 4) With the aim of selecting the optimum catalyst among $Fe^0$, $Fe^{2+}$ and $Fe^{3+}$, removal efficiency of each parameter in the optimum reaction conditions was considered. Although $Fe^{3+}$ was higher than other catalysts($Fe^0$, $Fe^{2+}$) in removal efficiency, $Fe^0$ was a optimum catalyst with a view of cost effectiveness.

• The Korean Journal of Pesticide Science
• /
• v.21 no.1
• /
• pp.68-74
• /
• 2017

An analytical method for detecting metamifop residue in paddy water, soil, and rice with high performance liquid chromatography (HPLC) was developed. Water was extracted with ethyl acetate before analyzing by HPLC. Soil residues were extracted with acetone under acidic condition and after purifying with $Extrelut^{(R)}$ NT, and silica SPE, the residue was analyzed by HPLC. For residue analysis in rice, the procedure involved extraction with acetone, purification with $Extrelut^{(R)}$ NT, partitioning between acetonitrile/hexane, purification with silica SPE cartridge, and analysis by HPLC. The limit of detection (LOD) was 1.0 ng, limit of quantitation (LOQ) was 3.0 ng, and method limit of quantitation (MLOQ) were 0.001 mg/L for paddy water, 0.01 mg/kg for rice and soil, respectively. Standard calibration curve shows linearity from 0.05 mg/kg to 5.0 mg/kg ($R^2=0.9999$). The recoveries in fortified paddy water were $91.3{\pm}3.5%$ (0.01 mg/L level) and $93.2{\pm}6.3%$ (0.05 mg/L level). The recoveries in fortified paddy soils were $92.5{\pm}4.0%$ (0.1 mg/kg level) and $92.7{\pm}4.0%$ (0.5 mg/kg level) in soil A, while, $102.3{\pm}4.4%$ (0.1 mg/kg level) and $98.9{\pm}7.9%$ (0.5 mg/kg level) in soil B, respectively. The recoveries in fortified rice were $93.0{\pm}6.9%$ (0.1 mg/kg level) and $85.0{\pm}3.5%$ (0.5 mg/kg level). This method was proved to be effective and can be used to determine the metamifop residue in paddy water, paddy soil, and rice.

• The Journal of the Petrological Society of Korea
• /
• v.28 no.4
• /
• pp.251-277
• /
• 2019

The Gogunsan Archipelago is composed of two island groups; the first group includes Mal-do, Myeong-do, Gwangdae-do, and Bangchuk-do islands consisting of Neoproterozoic rocks, and the second group includes Yami-do, Sinsi-do, Muneo-do, Jangja-do, and Seonyu-do islands consisting of Cretaceous rocks. The first group mainly consists of the Bangchuk formation which can be divided into two layers; the lower layer was more deformed than the upper layer. The former was intruded by mafic and felsic volcanic rocks formed in the volcanic arc tectonic setting 930-890 Ma and the latter was deposited ca. 825-800 Ma. In these islands, large scale folds with east-west fold axes were beautifully formed; the Maldo island fold was designated as natural monument and large scale beautiful chevron fold was developed on the Gwangdae-do island. In addition, there are unique zebra-shaped outcrop formed by a mixing of basic and acidic magma and Independent Gate shaped outcrop formed by coastal erosion. On the other hand, the Yami-do, Sinsi-do, Muneo-do, Jangja-do and Seonyu-do islands consist of 92-91Ma Cretaceous volcanic rocks and, in Sinsi-do island, the Nanshan formation deposited ca. 92 Ma. These Cretaceous volcanic rocks formed by melting of the continental crust by the heat supplied from the uplifting mantle due to the extension caused by a retreat of subducting ocean slab. Yami-do and Sinsi-do islands are composed of rhyolite. In Yami-do island, bands with vertical joint formed by cooling of the bottom part of the lava, are shown. In Sinsi-do island, large-scale vertical joints formed by cooling of lava flow, were developed. The Jangja-bong of Jangja-do island and Mangju-bong of Seonyu-do island are composed of brecciated rhyolite and formed a ring shaped archipelago contributing to the development of marine culture by providing natural harbor condition. They also provide beautiful views including 'Seonyu 8 views' along with other islands. As mentioned above, the Gogunsan archipelago is rich in geoheritages and associated cultural and historical resources, making it worth as a National Geopark.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.37 no.5
• /
• pp.612-617
• /
• 2008

Tetrodotoxin (TTX) analogues were first determined from the liver extracts of puffer fish, Takifugu niphobles, by LC/MS with Hydrophilic Interaction Liquid Chromatography (HILIC). In total, 7 TTX analogues were detected within 20 minutes as follows; 5,6,11-trideoxyTTX (34.0%, 1,029.6 nmol/g), 6,11-dideoxyTTX (29.3%, 887.6 nmol/g), TTX (22.1%, 667.8 nmol/g), 4,9-anhydro-TTX (11.2%, 339.3 nmol/g), 11-deoxyTTX＋5-deoxyTTX (2.6%, 78.6 nmol/g), and 4-epiTTX (0.8%, 23.6 nmol/g). Mouse toxicity of diluted liver extracts showed the highest toxicity at pH 3 (8.7 MU/mL) and decreased, as increasing pH, to 1.4 MU/mL at pH 10. At acidic (pH 5) and neutral conditions (pH 7), mouse toxicity of liver extracts (79 MU/mL) decreased slowly, as increasing temperature from $80^{\circ}C$ to $115^{\circ}C$, and time until 1 hour; in contrast, at the akaline condition (pH 9), the toxicity decreased rapidly to the more than half within 10 minutes. Individual toxicity of the fillet of T. niphobles were between $43.2{\sim}106.7$ MU, and $64{\sim}78%$ of its toxicity was eluted to soup when boiled with 3 volumes of water during 10 minutes.

• Economic and Environmental Geology
• /
• v.41 no.1
• /
• pp.15-32
• /
• 2008

The hydrochemical and isotopic (stable isotopes and noble gas isotopes) analyses for hot spring waters, cold groundwaters and surface water samples from the Seokmodo hot spring area of the Ganghwa province were carried out to characterize the hydrogeochemical characteristics of thermal waters and to interpret the source of thermal water and noble gases and the geochemical evolution of hot spring waters in the Seokmodo geothermal system. The hot spring waters and groundwaters show a weakly acidic condition with the pH values ranging from 6.42 to 6.77 and 6.01 to 7.71 respectively. The outflow temperature of the Seokmodo hot spring waters ranges from $43.3^{\circ}C\;to\;68.6^{\circ}C$. Relatively high values of the electrical conductivities which fall between 60,200 and $84,300{\mu}S/cm$ indicate that the hot spring waters were mixed with seawater in the subsurface geothermal system. The chemical compositions of the Seokmodo hot spring waters are characterized by Na-Ca-Cl water type. On the other hand, cold groundwaters and surface waters can be grouped into three types such as the Na(Ca)-$HCO_3$, Na(Ca)-$SO_4$ and Ca-$HCO_3$ types. The ${\delta}^{18}O\;and\;{\delta}D$ values of hot spring waters vary from -4.41 to -4.47%o and -32.0 to -33.5%o, respectively. Cold groundwaters range from -7.07 to -8.55%o in ${\delta}^{18}O$ and from -50.24 to -59.6%o in ${\delta}D$. The oxygen and hydrogen isotopic data indicate that the hot spring waters were originated from the local meteoric water source. The enrichments of heavy isotopes ($^{18}O\;and\;^2H$) in the Seokmodo hot spring waters imply that the thermal water was derived from the diffusion Bone between fresh and salt waters. The ${\delta}^{34}S$ values ranging from 23.1 to 23.5%o of dissolved sulfate are very close to the value of sea water sulfate of ${\delta}^{34}$S=20.2%o in this area, indicating the origin of sulfate in hot springs from sea water. The $^3H/^4He$ ratio of hot spring waters varies from $1.243{\times}10^{-6}\;to\;1.299{\times}10^{-6}cm^3STP/g$, which suggests that He gas in hot spring waters was partly originated from a mantle source. Argon isotopic ratio $(^{40}Ar/^{36}Ar=298{\times}10^{-6}cm^3STP/g)$ in hot spring waters corresponds to the atmospheric value.

• Journal of Soil and Groundwater Environment
• /
• v.8 no.2
• /
• pp.62-69
• /
• 2003

The aim of research is the evaluation of the $Cr^{6+}$ emission features of the liquid injection through emission experiments in varying conditions, based on a field-mixing ratio. The results showed that the content of $Cr^{6+}$ content in cement measured had an Ordinary Potland Cement (OPC) of 25.3 mg/kg, which constitute the largest portion among the other materials. Likewise, the emission experiment of homo-gel and sand-gel generally satisfied the standard of KSLT (Korea Standard Leaching Test) in waste of 1.5 mg/L, but in case of the standard of KSLT in soil the emission of OPC $Cr^{6+}$ of 4.85 mg/kg. These conditions is a little exceeded the criteria in the ‘Ga’ area in terms of Korea Soil Environmental Preservation Law. In addition, results generated by the mock-up injection facilities revealed that $Cr^{6+}$ emission increased as Water/Cement and injection pressure increased. At injection pressure higher than 4 kg/㎤, $Cr^{6+}$ emission exceeded the water preservation standard of 0.5 mg/L. Similarly, a pattern experiment of C $r^{6+}$ emission according to pH was conducted, in order to evaluate the $Cr^{6+}$ emission features of grout materials in leachate below pH 5 such as pH 4 acid rain or landfill. Results show that $Cr^{6+}$ emission dramatically increased in high acidic or basic state. It indicates that $Cr^{6+}$ emission will probably increase in an environment where grout materials are injected. On the other hand, concentration of leachate was determined in areas where grout materials are used. The results show that the concentration of emission in an ultra purity condition does not manifest intensity, and is affected in the OPC>MC>SC order. It means that the pollutants or $Cr^{6+}$ emission increases with decreasing concentration. As such, $Cr^{6+}$ emission will probably exceed the countermeasure criteria according to the types of gout materials. Similarly, high pressure or injection will cause increased $Cr^{6+}$ emission. Therefore, the selection of materials or mixing ratio should be considered in general as well as according to specific industries, based on the strength and pH of $Cr^{6+}$ emission.

• Journal of the Mineralogical Society of Korea
• /
• v.24 no.2
• /
• pp.73-82
• /
• 2011

X-ray absorption spectroscopy (XAS) study was conducted using arsenite-sorbed two-line ferrihydrite to investigate the mechanism of surface interactions between two-line ferrihydrite and As(III) (arsenite) which are ubiquitous in nature. The two-line ferrihydrite used was synthesized in the laboratory and the study was undertaken at pHs 4 and 10 to compare the difference in mechanisms of surface interaction between acidic and alkaline environments. The effect of arsenite-adsorbed concentrations on surface complexation was investigated at each pH condition as well. From the results of XAS analyses, the structural parameters of arsenite in the EXAFS revealed that the coordination number and distanceof As-O were 3.1~3.3 and 1.74~1.79 ${\AA}$, respectively, which indicate that the unit structure of arsenite complex formed on the surface of two-line ferrihydrite is $AsO_3$. The dominant structures of As(III)-Fe complex were examined to be bidentate binuclear comer-sharing ($^2C$) and the mixture of bidentate mononuclear edge sharing ($^2E$) and $^2C$ appeared as well. At pH 4, arsenite complex showed different structures on the surface of two-line ferrihydrite, depending on the adsorbed concentrations. At pH 10, on the contrary, the surface structures of arsenite complexes were interpreted to be almost identical, irrespective of the adsorbed concentrations of arsenite. Consequently, this microscopic XAS results support the results of macroscopic adsorption experiments in which the surface interaction between arsenite and two-line ferrihydrite is significantly influenced by pH conditions as well as arsenite concentrations.

• Journal of the Mineralogical Society of Korea
• /
• v.22 no.3
• /
• pp.177-189
• /
• 2009

Iron (oxyhydr)oxides commonly form as secondary minerals of high reactivity and large surface area resulting from alteration and weathering of primary minerals, and they are efficient sorbents for inorganic and organic contaminants. Accordingly, they have a great potential in industrial applications and are also of substantial interest in environmental sciences. Goethite (${\alpha}$-FeOOH) is one of the most ubiquitous and stable forms of iron (oxyhydr)oxides in terrestrial soils, sediments, and ore deposits, as well as a common weathering product in rocks of all types. This study focused on adsorption reaction as a main mechanism in scavenging arsenic using goethite. Goethite was synthesized in the laboratory to get high purity, and a variety of mineralogical and physicochemical features of goethite were measured and related to adsorption characteristics of arsenic. To compare differences in adsorption reactions between arsenic species, in addition, a variety of experiments to acquire adsorption isotherm, adsorption edges, and adsorption kinetics were accomplished. The point of zero charge (PZC) of the laboratory-synthesized goethite was measured to be 7.6, which value seems to be relatively higher, compared to those of other iron (oxyhydr)oxides. Its specific surface area appeared to be $29.2\;m^2/g$ and it is relatively smaller than those of other (oxyhydr)oxides. As a result, it was speculated that goethite shows a smaller adsorption capacity. It is likely that the affinity of goethite is much more larger for As(III) (arsenite) than for As(V) (arsenate), because As(III) was observed to be much more adsorbed on goethite than As(V) in equivalent pH conditions. When the adsorption of each arsenic species onto goethite was characterized in various of pH, the adsorption of As(III) was largest in neutral pH range (7.0~9.0) and decreased in both acidic and alkaline pH conditions. In the case of As(V), the adsorption appeared to be highest in the lowest pH condition, and then decreased with an increase of pH. This peculiarity of arsenic adsorption onto goethite might be caused by macroscopic electrostatic interactions due to variation in chemical speciation of arsenic and surface charge of goethite, and also it is significantly affected by change in pH. Parabolic diffusion model was adequate to effectively evaluate arsenic adsorption on goethite, and the regression results show that the kinetic constant of As(V) is larger than that of As(III).

• Economic and Environmental Geology
• /
• v.36 no.6
• /
• pp.469-480
• /
• 2003

Laboratory leaching experiment study carried out to estimate a extent of heavy metals that could be leached out when acid rain(pH 5.0-3.0) and strong acidic solution(pH 2.5-1.0) reacted with tailings and contaminated soils from abandoned metal mines. In slightly to moderately acid conditions(pH 5.0-3.0), As, Pb and Zn dissolutions became significantly increased with decreased pH in tailing, while dissolution of these elements was very limited in contaminated soil. These results suggested that moderately acid rainwater leaches Pb, As and Zn from the tailings, while these elements would remain fixed in contaminated soil. In the pH range of 2.5-1.0(strongly acid condition), Zn, Cd and Cu concentrations of leachate rapidly increased with decreased pH in contaminated soil, while Pb, As and Co dissolutions became importantly increased in tailings. The experimental solubility of Zn. Cd and Cu was very low even at very low pH values(up to pH 1), except for CY4(Cheongyang mine). These can result from an incomplete dissolution or the presence of less soluble mineral phases. So, the solubility of heavy metals depends not only on the pH values of leachate but also on the speciation of metals associated with contaminated soils and tailings. The relative mobility of each element within failings at the pH 5.0-3.0 of the reaction solution was in the order of Pb>Zn>Cd>Co=Cu>As. In case of pH 2.5-1.0 of the reaction solution, the relative mobility of each element within contaminated soils and tailings were in the order of Zn＞Cd>Cu>Co>Pb=As for contaminated soils, and Pb>Zn>Cd>hs>Co>Cu for tailings. The obtained results could be useful for assessing the environmental effects and setting up the restoration plan in the areas.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.4
• /
• pp.609-617
• /
• 2000

This study is aimed at investigating an effect of HCl gas on selective reduction of NOx over a CuHM and $V_2O_5-WO_3/TiO_2$ catalyst. SCR process is the most effective method to remove NOx, but catalyst can be deactivated by the acidic gas such as HCl gas which is also included in flue gas from the incinerator. In dry condition of flue gas, the CuHM catalyst treated by HCl gas has shown higher NO removal activity than the fresh catalyst. The activity of the catalyst can be restored by treating at $500^{\circ}C$. On the contrary. $V_2O_5-WO_3/TiO_2$ catalyst is obviously deactivated by HCl and the deactivation increases in proportion to the concentration of HCl gas. The deactivated catalyst is not restored to it's original activity by heat treatment for regeneration. In wet flue gas stream, the CuHM catalyst has shown lower activity than fresh catalyst and $V_2O_5-WO_3/TiO_2$ catalyst was severely deactivated by HCl treatment. The activity loss of catalysts are mainly due to the decrease of Br$\ddot{o}$nsted acid site on the catalyst surface by $NH_3$ TPD. The change of BET surface area of CuHM catalyst after the reaction isn't observed but $V_2O_5-WO_3/TiO_2$ catalyst is observed. The amount of $Cu^{{+}{+}}$ and $V_2O_5$ is decreased after the reaction. From these results, it is expected that CuHM catalyst should be better than $V_2O_5-WO_3/TiO_2$ catalyst for its application to the incineration of flue gas.