• Corrosion Science and Technology
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• v.18 no.6
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• pp.285-291
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• 2019

In this study, the corrosion characteristics of T22 and T92 steel were investigated in 6O₂ + 16CO₂ + 2SO₂ gas environment at 650 ℃. Corrosion characteristics were characterized by weight gain, oxide layer thickness, scanning electron microscope, optical microscope, energy dispersive X-ray spectroscopy, and X-ray diffraction. T22 and T92 steel tended to stagnate oxide layer growth over time. Oxidation kinetics were analyzed using the data of oxide layer thickness, and a regression model was presented. The regression model was significantly acceptable. The corrosion rate between the two steels through the regression model showed significant difference. The T92 steel was approximately twice as large as the time exponent and showed very good corrosion resistance compared to the T22 steel. In both steels, the oxide layer mainly formed a Fe-rich oxide layer composed of hematite (Fe₂O₃), magnetite (Fe₃O₄), and spinel (FeCr₂O₄). Sulfide segregation occurred in the oxide layer due to SO₂ gas. However, the locations of segregation for the T22 and T92 steel were different.

• Nuclear Engineering and Technology
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• v.33 no.5
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• pp.526-538
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• 2001

Fatigue tests in air and in room temperature water were performed to obtain comparable data and stable crack measuring conditions. In air environment, fatigue crack growth rate was increased with increasing temperature due to an increase in crack tip oxidation rate. In room temperature water, the fatigue crack growth rate was faster than in air and crack path varied on loading conditions. In simulated light water reactor (LWR) conditions, there was little environmental effect on the fatigue crack growth rate (FCGR) at low dissolved oxygen or at high loading frequency conditions. While the FCGR was enhanced at high oxygen condition, and the enhancement of crack growth rate increased as loading frequency decreased to a critical value. In fractography, environmentally assisted cracks, such as semi-cleavage and secondary intergranular crack, were found near sulfide inclusions only at high dissolved oxygen and low loading frequency condition. The high crack growth rate was related to environmentally assisted crack. These results indicated that environmentally assisted crack could be formed by the Electrochemical effect in specific loading condition.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.435-437
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• 2003

In order to investigate processes and factors controlling the chemical and isotopic compositions of the Han River, seasonal studies were carried out. The North Han River was much lower in the concentrations of total dissolved solids (TDS), dissolved inorganic carbon (DIC) and major ions than the South Han River, but higher in $SiO_2$ concentration, $\delta$$^{34}$ $S_{so4}$ value and $^{87}$ Sr/$^{86}$ Sr ratio. This indicates that the chemical and isotopic compositions of the Han River were strongly controlled by the geology of their drainage basins: silicate rocks in the North Han River and carbonate rocks in the South Han River. The $\delta$$^{34}$ $S_{so4}$ values were relatively higher in the North Han River (5.90$\pm$1.46$\textperthousand$)) than in the South Han River (3.48$\pm$0.73$\textperthousand$). This implies that dissolved S $O_{4}$$^{2-}$ in the North Han River might be mostly derived from deposition of atmospheric sulfates, whereas in the South Han River from oxidation of sulfide minerals in the abandoned poly-metallic deposits and the coal-bearing sedimentary rocks distributed over the upstream as well as deposition of atmospheric sulfates. The $^{87}$ S $r^{86}$ Sr ratios in the North Han River were distinctly higher than those in the South Han River, reflecting water-rock interaction with different rock types.pes.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.409-412
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• 2003

Total extraction of stream sediments in the Kwangyang mine area shows their significant pollution with most trace metals such as Cr, Co, Fe, Pb, Cu, Ni, Zn and Cd, due to sulfide oxidation in waste dumps. Calculations of enrichment factor shows that Chonam-ri creek sediments are more severely contaminated than Sagok-ri sediments. Using the weak acid (0.1N HCl) extraction and sequential extraction techniques, the transport and sediment-water partitioning of heavy metals in mine drainage were examined for contaminated sediments in the Chonam-ri and Sagok-ri creeks of the Kwangyang Au-Ag mine area. Calculated distribution coefficient (Kd) generally decreases in the order of Pb $\geq$Al > Cu > Mn > Zn > Co > Ni $\geq$ Cd. Sequential extraction of Chonam-ri creek sediments shows that among non-residual fractions the Fe-Mn oxide fraction is most abundant for most of the metals. This indicates that precipitation of Fe hydroxides plays an important role in regulating heavy metal concentrations in water, as shown by field observations.

• Resources Recycling
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• v.27 no.3
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• pp.3-7
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• 2018

Development of extractive metallurgical processes for metal sulfides has become of importance owing to the depletion of oxide ores with rich metal contents. Most of the leaching reactions of metal sulfides is electrochemical reaction and can be classified as $H_2S$, S, and ${SO_4}^{2-}$ evolution type. The acidity of leaching solution and the presence and concentration of an oxidizing agent affect the formation of reaction intermediates containing sulfur. Frost diagram of sulfuroxoanion indicates that the oxoanions with higher oxidation number are more thermodynamically stable in the presence of oxidizing agents.

• Journal of the Korean Home Economics Association
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• v.4 no.1
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• pp.589-594
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• 1963

Ascorbic acid has a strong power to reduce other materials, so by using this reducing power we can analise many materials quantitatively. Dihydro-ascorbic acid is quantitatively changed into ascorbic acid under a certain condition, if reduced by hydrogen-sulfide. Dihydro-ascorbic acid also has physiolosical effect, but less effect than ascorbic acid. The effect of dihydro-ascorbic acid is regarded as a half of that of ascorbic acid. Among the analytical methods applying this theory the method using 2.6 dichlorophenol indophenol what called the method of Indophenol is used most widely; so does Hydrazine-method. But comparing these two methods the former shows a little higher rate in analytical value. Vegetable are vital sources for vitamin C. According to the report of the commitee of FAO Korean branch the amount of daily per head average intake of vitamin C is about 70mg in raw materials. Since vitamin C is easily affected by heating or oxidation in Cooking the loss is not a little. Consequntly it is regarded that the actual amount of intake will be much less than basic amount. It is therefore very important to find out that how much percent of the loss there will be in case of cooking, in order to dicide the actual amount of in take as proper nutrition for a person. Therefore this paper intended to give some help in setting a standard amount of V.C intake, by measuring the change of the V.C amount using the general cooking method and by measuring amount of V.C contained in the part of vegetable, used in Korea abundantly.

• Journal of the korean society of oceanography
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• v.39 no.4
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• pp.243-250
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• 2004

Sediment microcosm experiments were conducted for 14 and 28 days using Zn spiked sediment to examine the changing distribution of bioavailab1e sediment-bound Zn at different SEM (simultaneously extracted metal)-Zn/ AVS (acid volatile sulfide) mole ratios as a function of time and amphipod density. In surficial sediments (0-1cm), AVS concentrations significantly decreased due to bioturbation and oxidation, while SEM-Zn concentrations remained unchanged. As a result, SEM-Zn/AVS ratios in the surface sediment were greater one although the ratios were designed as less than one initially. With increasing SEM-Zn/AVS ratios in surficial sediments, concentrations of potentially bioavailable $MgCl_2$extractable-Zn, NaOAc extractable-Zn and pore water-Zn significantly increased, while concentrations of SEM-Zn were not significantly varied. Results suggested that as AVS concentrations decreased, AVS bound Zn was partitioned to other sediment fractions (i.e. $MgCl_2$ and NaOAc extractable) and the pore water, resulting in changes in Zn bioavailability in surficial sediments. Concentrations of AVS, SEM-Zn and pore water-Zn remained unchanged in the deeper layers (>1 cm) of the sediment.

• Korean Journal of Metals and Materials
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• v.47 no.2
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• pp.99-106
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• 2009

The high temperature corrosion properties of heat resistant steels were investigated in oxidation atmosphere including sulfur dioxide. The heat resistant steels of T22, T92, T122, T347HFG and T304H were evaluated at 620, $670^{\circ}C$ for 400 hours. The corrosion rates showed a decreasing tendency while chrome contents of those steels increased from 2 mass.% to 19 mass.%. The in crease in temperature increasement has an more effect on the corrosion rates of low chrome steels than high chrome steels. The weight gains of T22, T92, T304H at $670^{\circ}C$ were 3.7, 1.65, 1.23 times compared with those at $620^{\circ}C$. The external scale formed on T22 was composed of hematite, magnetite and Fe-Cr spinel and internal layer including iron oxide mixed with sulfide. The scales formed on T92, T122, T304H consisted of an outer layer of hematite and inner layer of chrome oxide and hematite. The proportion of chrome oxide at inner layer was increased when the chrome contents in heat resistant steels were increased.

• Resources Recycling
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• v.30 no.4
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• pp.11-19
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• 2021

Arsenic (As) oxidation followed by precipitation from a high-As(III)-containing leaching solution derived from a sulfidic ore was investigated in this study to remove aqueous As from the solution using activated carbon (AC) with air injection as an oxidant. To obtain the initial leaching solution, a domestic sulfidic ore was leached in a sulfuric acid solution at pH 1 and 50℃ for 95 h, and approximately 7 g/L of Fe and 3 g/L of As were leached out. To determine the effect of the oxidative reaction utilizing AC with air injection, the leaching solution was tested under the following five oxidative conditions at an initial pH of 1 and 90℃ for 72 h: air-only injection; air injection with 1, 5, and 10 w/v% of AC addition; and H₂O₂ addition. The tests in the presence of both air and AC revealed that the oxidation kinetics and As removal were improved by the reaction between the metallic species and the surface group formed on the AC surface. In addition, the greater the amount of AC added, the better was the reaction efficiency, removing 93-94% of As with more than 5 w/v% of AC addition. Finally, X-ray diffraction analysis confirmed that the precipitate formed from the oxidative reaction was scorodite (FeAsO₄·2H₂O).

• The Journal of Engineering Geology
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• v.28 no.3
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• pp.501-512
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• 2018

The acid leachate derived from the sulfide mineral such as pyrite can cause problems such as aging of infrastructure and environment contamination around the civil construction site. The purpose of this study is to assess the environmental effect of an acid leachate derived from pyrite in the Miryang area under road construction. In this study, 13 samples of situ core were used for the net acid generation (NAG) experiment. The chemical composition including pH, oxidation and reduction potential (ORP) and electrical conductance of water samples produced from the NAG test was analyzed. In additional, five polished thin sections of rock cores were made for electro microprobe analyses. In the results of the NAG tests, 7 samples showed lower values than pH 3.5. It strongly indicated that these areas are under the environmental and infrastructure damage by the acid leachate. The chemical type of the 7 samples was classified as the $Fe(Ca)-SO_4$ type, which is totally a different type compared to general groundwater. The concentration of total sulfur ranges from 0.004% to 12.5%. 6 rock samples are plotted on a potentially acid forming zone in the relation diagram between the total sulfide and NAG-pH. In conclusion, it is suggested that a protection method against an environmental demage and an infrastructure corrosions by the acid leachate should be prepared in all of areas under a road construction.