• Transactions of the Korean hydrogen and new energy society
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• v.22 no.4
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• pp.443-450
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• 2011

The three-reactor chemical-looping process (TRCL) for the production of hydrogen from natural gas is attractive for both $CO_2$ capture and hydrogen production. In this study, redox property of $Fe_2O_3$ and $WO_3$ supported with $ZrO_2$ and $MgAl_2O_4$ were studied with temperature programmed oxidation/reduction (TPO/R) experiment. All metal oxides were prepared by ball mill method. Metal oxides supported with $ZrO_2$ showed the good redox property in TPO and TPR tests. Reduction behavior was matched well the theoretical reduction mechanism. Metal oxides supported with $MgAl_2O_4$ formed a solid solution ($MgFe_{0.6}Al_{1.4}O_4$, $MgWO_4$). $Fe_2O_3$ showed more narrow reaction range and lower reaction temperature than $WO_3$.

• Journal of Korean Society on Water Environment
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• v.38 no.6
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• pp.316-326
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• 2022

This study aimed to investigate the causes of the increasing Total Phosphate(TP) in the mainstream of Mangyeong river over the past 10 years, and suggested a reduction plan of about 3 points. First, the high TP concentration was continuously released in the discharge outlet of the Haepo bridge stormwater pipeline. The average TP concentration was 5.066 mg/L and values as high as 29.470 mg/L were measured. The highest pollution contribution rate to the Mangyeong river was more than 70 %. The cause of the pollution was expected to take place somewhere in Wanju Industrial Complex. Second, the average TP concentration of wastewater-treated effluent in the H factory was 0.405 mg/L. If a TP reduction facility is additionally installed in the H factory, it will help reduce TP uptake by Lake Saemangeum. Third, the TP concentration of untreated non-point source point flowing into the Samrae stream was very high with an average of 2.828 mg/L. Also, the pollution contribution rate of Samraecheon 2 to Mangyeong river was 21.8 % on average and up to 58 %. The pollution contribution rate was also high during the agricultural season and the winter, during which the flow rate is decreased. Investigation of these three points may be continuously needed, and analysis results and policy proposals presented to Jeollabukdo and Wanjugun to manage pollution sources.

• The Korean Journal of Pesticide Science
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• v.14 no.3
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• pp.235-240
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• 2010

In order to elucidate residual characteristics of pesticides in garlic by drying, azoxystrobin and flutolanil used for garlic were treated to the garlic by dipping for 1 and 5 min into their standard diluents and then the garlic was dried with a freeze-drier. The test pesticides were analyzed with a GLC-ECD/NPD. Recoveries of the pesticides ranged from 81.96 to 98.18%. Amount of azoxystrobin and flutolanil in fresh garlic were 0.34 and 1.18 mg/kg in case of dipping for 1 min. and 0.44 and 2.15 mg/kg in case of dipping for 5 min., respectively. Also, amount of azoxystrobin and flutolanil in dried garlic were 0.80 and 4.51 mg/kg in case of dipping for 1 min. and 1.03, 5.28 mg/kg in case of dipping for 5 minute, respectively, representing that concentration of the test pesticides in garlic were increased by drying. In case of dipping for 1 and 5 min., processing factors of azoxystrobin were 2.35 and 3.34 and those of flutolanil were 1.19 and 1.17, respectively. Reduction factors of the pesticides in garlic were range from 0.94 to 0.97, indicating that few amounts of the test pesticides in garlic were dissipated by freeze-drying.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2003.04a
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• pp.28-28
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• 2003

• The Korean Journal of Pesticide Science
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• v.18 no.4
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• pp.330-335
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• 2014

This study was conducted to investigate residue levels of chlorantraniliprole and ethaboxam in inner part and outer leaves of a head-type Korean cabbage. Further, reduction of residues was measured after water washing, blanching and heat-cooking of the outer leaves. For chlorantraniliprole, residues in inner part and outer leaves were <0.01 mg/kg and 0.0757 mg/kg, respectively, in case of three-time spraying 30 days before harvest and <0.01 mg/kg and 1.19 mg/kg, respectively, in case of four-time spraying 10 days before harvest; for ethaboxam, <0.05 mg/kg and 0.216 mg/kg, respectively and <0.05 mg/kg and 1.18 mg/kg, respectively. Chlorantraniliprole and ethaboxam were not detected in inner part of the head-type Korean cabbage. Residue levels in outer leaves were very high as 10-100 fold as those in inner part of the cabbage. Therefore, there is no concern for safety of pesticide residues on kimchi prepared with the inner part of a head-type Korean cabbage. In addition, it needs to be noted that outer leaves should be carefully removed at harvest of the cabbage. Outer leaves water washed and blanched are called as Woogeogi, which is consumed after heat-cooking. In Woogeogi, residue concentrations of two compounds reduced to less than 10%, and further less than 5% by heat-cooking. This indicates that considerable amount of the test pesticide residues in outer leaves of a head-type Korean cabbage removed through water washing, blanching and heat-cooking.

• Korean Journal of Environmental Agriculture
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• v.20 no.3
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• pp.175-179
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• 2001

To find out the effect of cadmium(Cd) on growth of major vegetables in Korea, phytotoxicity and absorption of Cd were investigated with chinese cabbage, radish, and lettuce grown in upland soils of different Cd concentrations. Cadmium phytotoxicity was shown by growth retardation and leaf chlorosis in chinese cabbage and lettuce at the early growing stage. The threshold concentrations of growth damage resulting from the significant reduction (5%) of growth and yield of chinese cabbage and lettuce were $50{\sim}100$ and $10{\sim}25$ mg/kg soil, respectively. However, there was no significant reduction of radish yield under Cd treatment of 100 mg/kg soil. As Cd concentrations in soils increased, the contents of Cd in products were significantly increased, basically. The contents of Cd in edible part of chinese cabbage, radish, and lettuce grown at the 5 mg/kg Cd treated soils were 0.13, 0.18, and 3.37 mg/kg FW, respectively. Total absorbed Cd in the vegetables tended to occur in the following order, chinese cabbage > radish > lettuce above 25 mg/kg Cd treated soils whereas lettuce absorbed more Cd than chinese cabbage and radish below 10 mg/kg Cd concentration.

• Journal of the Mineralogical Society of Korea
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• v.21 no.2
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• pp.161-175
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• 2008

The soil developed from volcanic ash in Jeju Island, Korea, were classified as typical Andisols. The soils had acidic pH, high water contents, high organic matters and clay-silty textures. The crystalline minerals of the samples were mainly composed of ferromagnesian minerals such as olivine and pyroxene, and iron oxides such as magnetite and hematite derived from basaltic materials. A large amount of gibbsite was found at the subsurface horizon as a secondary product from the migration of excessive aluminum. In addition, our study has shown that considerable amounts of poorly ordered minerals like allophane and ferrihydrite were present in Jeju soils. The contents of $SiO_2$ were lower than those of other soil orders, but $A1_2O_3$ and $Fe_2O_3$ contents were higher. These results are some of the important chemical properties of Andisols. The contents of heavy metals were in the range of $84{\sim}198$ for Zn, $56{\sim}414$ for Ni, $38{\sim}150$ for Co, $132{\sim}1164\;mg\;kg^{-1}$ for Cr, which are higher than the worldwide values in most of the soils. Some soil samples contained relatively high levels of Cr exceeding 1000 mg/kg. Mean reduction capacity of the Jeju soils was $6.53\;mg\;L^{-1}$ reduced Cr(VI), 5.1 times higher than that of the non-volcanic ash soils from inland of Korea. The soil reduction capacity of the inland soils had a good correlation with total carbon content (R = 0.90). However, in spite of 20 times higher total carbon contents in the Jeju soils, there was a week negative correlation between the reduction capacity and the carbon content (R = -0.469), suggesting that the reduction capacity of Jeju soils is not mainly controlled by the carbon content and affected by other soil properties. Correlations of the reduction capacity with major elements showed that Al and Fe were closely connected with the reduction capacity in Jeju soil (R = 0.793; R = 0.626 respectively). Moreover, the amounts of Ni, Co and Cr had considerable correlations with the reduction capacity (R = 0.538; R = 0.647; R = 0.468 respectively). In particular, in relation to the behavior of redox-sensitive Cr, the oxidation of the trivalent chromium to mobile and toxic hexavalent chromium can be restricted by the high reduction capacity in Jeju soil. The factors controlling the reduction capacity in Jeju soils may have a close relation with the andic soil properties explained by the presence of considerable allophane and ferrihydrite in the soils.

• The Korean Journal of Ecology
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• v.19 no.3
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• pp.193-199
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• 1996

Alleviation of Al toxicity by Ca and Mg was studied with seedings of Pinus densiflora, P. rigida and P. thunbergii under the solution culture. The seedlings were cultivated in the enriched Can and Mg nutrient solution with 2, 000 ${\mu}M$ Al for three weeks. The hightest total root lengths of P. densiflora, P. rigida and P. thunbergii increased by 21, 33 and 133% in Ca enriched solution, and 23, 44 and 107% in Mg enriched solution, respectively. Ratios of lateral root to main root length increased significantly in Mg enriched solution, and redution of Al toxicity was more affected by enriched Mg than by enriched Ca. Al content in tissue was reduced by enriched Ca and Mg.

• Bulletin of the Korean Chemical Society
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• v.26 no.2
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• pp.281-284
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• 2005

The Fe/MgO catalysts with different Fe loadings (1, 4, 6, 15 and 30 wt% Fe) were prepared by a wet impregnation with iron nitrate as precursor. All of the catalysts were characterized by BET surface analyzer, X-ray diffraction (XRD), temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). The maximum removal capacity of $H_2S$ was obtained with 15 wt% Fe/MgO catalyst which had the highest BET surface area among the measured catalysts. XRD of Fe/MgO catalysts showed that well dispersed Fe particles could be present on Fe/MgO with Fe loadings below 15 wt%. The crystallites of bulk $\alpha$-$Fe_2O_3$ became evident on 30 wt% Fe/MgO, which were confirmed by XRD. TPR profiles showed that the reducibility of Fe/MgO was strongly related to the loaded amounts of Fe on MgO support. Therefore, the highest removal efficiency of $H_2S$ in wet oxidation could be ascribed to a good dispersion and high reducibility of Fe/MgO catalyst. XPS studies indicated that the $H_2S$ oxidation with Fe/MgO could proceed via the redox mechanism ($Fe^{3+}\;{\leftrightarrow}\;Fe^{2+}$).

• Journal of Korea Foundry Society
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• v.36 no.6
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• pp.195-201
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• 2016

The effects of Mg addition on heat treatment and mechanical properties of A356 alloy were investigated. With increased amounts of Mg addition to A356 alloy, the grain size decreased and eutectic Si was refined. And, this process can improve the mechanical properties. Solid solution heat treatment causes the spheroidizing of eutectic Si. In this study, although eutectic Si was refined with Mg addition, solid solution time increased from 2 hours to 6 hours with Mg addition, and aging time also increased, from 4 hours to 8 hours. After heat treatment, Mg2Si remained in a formation of Chinese script. And, Chinese script Mg2Si formed with Mg addition caused a reduction of the elongation of the alloys according to the stress concentration.