• Journal of Korean Society of Water and Wastewater
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• v.33 no.6
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• pp.469-480
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• 2019

This study was conducted to evaluate the degradation and mineralization of PPCPs (Pharmaceuticals and Personal Care Products) using a CBD(Collimated Beam Device) of UV/H₂O₂ advanced oxidation process. The decomposition rate of each substance was regarded as the first reaction rate to the ultraviolet irradiation dose. The decomposition rate constants for PPCPs were determined by the concentration of hydrogen peroxide and ultraviolet irradiation intensity. If the decomposition rate constant is large, the PPCPs concentration decreases rapidly. According to the decomposition rate constant, chlortetracycline and sulfamethoxazole are expected to be sufficiently removed by UV irradiation only without the addition of hydrogen peroxide. In the case of carbamazepine, however, very high UV dose was required in the absence of hydrogen peroxide. Other PPCPs required an appropriate concentration of hydrogen peroxide and ultraviolet irradiation intensity. The UV dose required to remove 90% of each PPCPs using the degradation rate constant can be calculated according to the concentration of hydrogen peroxide in each sample. Using this reaction rate, the optimum UV dose and hydrogen peroxide concentration for achieving the target removal rate can be obtained by the target PPCPs and water properties. It can be a necessary data to establish design and operating conditions such as UV lamp type, quantity and hydrogen peroxide concentration depending on the residence time for the most economical operation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.10
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• pp.855-859
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• 2007

Hydrogen as an energy carrier in fuel cell offers perhaps the largest potential benefits of reduced emissions of pollutants and greenhouse gases. The generation of high-purity hydrogen from hydrocarbon fuels is essential for efficient operation of fuel cell. Reduction of carbon monoxide to an acceptable level of 10ppm involves high temperature and low temperature water gas shift (WGS), followed by selective oxidation of residual carbon monoxide. The WGS reactor was designed and tested in this study to produce hydrogen-rich gas with CO to less than 5000 ppm. In the water gas shift operation, gas emerges from the reformer is taken through a high temperature shift (HTS) catalyst to reduce the CO concentration to about $2{\sim}4%$ followed to about 5000 ppm via a low temperature shift (LTS) catalyst.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.4
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• pp.481-491
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• 2015

The aim of this study was to evaluate the chemical quenching system for residual ozone and to determine the operating condition for the quenching system. Hydrogen peroxide ($H_2O_2$) and sodium thiosulfate ($Na_2S_2O_3$) were investigated as quenching reagents for ozone removal, and the tendency of each chemical was notably different. In the case of $H_2O_2$, the degradation rate of ozone was increased as the concentration of $H_2O_2$ increase, and temperature and pH value have a significant effect on the degradation rate of ozone. On the other hand, the degradation rate of ozone was not affected by the concentration of $Na_2S_2O_3$, temperature and pH value, due to the high reactivity between the ${S_2O_3}^{2-}$ and ozone. This study evaluates the decomposition mechanism of ozone by $H_2O_2$ and $Na_2S_2O_3$ with consideration for the water quality and reaction time. Furthermore, the removal test for the quenching reagents, which can be remained after reaction with ozone, was conducted by GAC process.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.3
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• pp.377-384
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• 2004

In the present study, a feasibility of an advanced oxidation process using UV/Hydrogen peroxide($H_2O_2$) system equipped with a medium pressure lamp for secondary effluent reclamation was investigated. Initial concentration of $H_2O_2$ and pH were changed to determine the optimum operation condition for the system. The removal efficiency of color was than 80% with 14.3mg/L of initial $H_2O_2$ and 5 minute of contact time in the UV/$H_2O_2$ system. The color removal was analyzed using first-order reaction equation. The dependence of rate constant (k) on initial $H_2O_2$ represented the rational relationship with maximum value. Residual $H_2O_2$ caused increase of effluent COD, since analyzing agent, dichromate, reacted with $H_2O_2$ in the sample. Therefore, excess initial concentration of $H_2O_2$ would significantly affect effluent COD measurement. At pH variation experiment, both residual $H_2O_2$ and color showed peak in the neutral pH range with the same pattern. Effect of $H_2O_2$ dose also enhanced color removal but raised residual $H_2O_2$ problem in the continuous operation UV system. In conclusion, these results indicated that medium pressure UV/$H_2O_2$ system could be used to control color in the secondary effluent for reclamation and reuse.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.20-25
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• 2008

Sulfide stress corrosion cracking (SSCC) of materials exposed to oilfield environment containing hydrogen sulfide ($H_2S$) has been recognized as a materials failure problem. Laboratory data and field experience have demonstrated that extremely low concentration of $H_2S$ may be sufficient to lead to SSC failure of susceptible materials. In some cases, $H_2S$ can act synergistically with chlorides to produce corrosion and cracking failures. SSC is a form of hydrogen embrittlement that occurs in high strength steels and in localized hard zones in weldment of susceptible materials. In the heat-affected zones adjacent to welds, there are often very narrow hard zones combined with regions of high residual stress that may become embrittled to such an extent by dissolved atomic hydrogen. On the base of understanding on sulfide stress cracking and its mechanism, SSC resistance for the several materials, those are ASTM A106 Gr B using in the oil industries, are evaluated.

• Corrosion Science and Technology
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• v.18 no.6
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• pp.267-276
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• 2019

The purpose of this study was to examine the influence of conditions for quenching and/or tempering on the corrosion and hydrogen diffusion behavior of ultra-strong automotive steel in terms of the localized plastic strain related to the dislocation density, and the precipitation of iron carbide. In this study, a range of analytical and experimental methods were deployed, such as field emission-scanning electron microscopy, electron back scatter diffraction, electrochemical permeation technique, slow-strain rate test (SSRT), and electrochemical polarization test. The results showed that the hydrogen diffusion parameters involving the diffusion kinetics and hydrogen solubility, obtained from the permeation experiment, could not be directly indicative of the resistance to hydrogen embrittlement (HE) occurring under the condition with low hydrogen concentration. The SSRT results showed that the partitioning process, leading to decrease in localized plastic strain and dislocation density in the sample, results in a high resistance to HE-induced by aqueous corrosion. Conversely, coarse iron carbide, precipitated during heat treatment, weakened the long-term corrosion resistance. This can also be a controlling factor for the development of ultra-strong steel with superior corrosion and HE resistance.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.6
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• pp.434-441
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• 2009

The effect of varying sulfate concentration on continuous fermentative hydrogen production was studied using enriched mixed microflora in continuously fed reactor. Glucose was used as a model substrate for carbohydrates, and hydraulic retention time (HRT) was maintained at 1, 0.5, 0.25 day, respectively. Sulfate concentration was 0${\sim}$20,000 mg/L and the operating pH was maintained at 5.5. The experimental results indicate that hydrogen production is not affected by high sulfate concentration and shorter HRT of 0.25 day enhance hydrogen production. At HRT 1, 0.5, 0.25 day, the hydrogen production rate and hydrogen yield were 2.6, 4.6, 9.4 L/day, and 2.0, 1.8, 1.6 mol $H_2$/mol glucose, respectively. Residual sulfate content was 96${\sim}$98, 95${\sim}$97, and 94${\sim}$97% at HRT 1, 0.5, 0.25 day which show that no sulfate reduction occurred in the reactor during the experiments. Results of Fluorescence In Situ Hybridization (FISH) may indicate the presence of HPB (hydrogen producing bacteria) under all experimental conditions. However, SRB (sulfate reducing bacteria) were not found.

• Korean Journal of Environmental Agriculture
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• v.38 no.1
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• pp.54-60
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• 2019

BACKGROUND: Hydrogen fluoride is one of the 97 accident preparedness substances regulated by the Ministry of Environment (Republic of Korea) and chemical accidents should be managed centrally due to continual occurrence. Especially, hydrogen fluoride has a characteristic of rapid diffusion and very toxic when leaking into the environment. Therefore, it is important to predict the impact range quickly and to evaluate the residual contamination immediately to minimize the human and environmental damages. METHODS AND RESULTS: In order to estimate the accident impact range, the off-site consequence analysis (OCA) was performed to the worst and alternative scenarios. Also, in order to evaluate the residual contamination of hydrogen fluoride in crop, the samples in accident site were collected from 15-divided regions (East direction from accident sites based on the main wind direction), and the concentration was measured by fluoride ($F^-$) ion-selective electrode potentiometer (ISE). As a result of the OCA, the affected distance by the worst scenario was estimated to be >10 km from the accident site and the range by the alternative scenario was estimated to be about 1.9 km. The residual contamination of hydrogen fluoride was highest in the samples near the site of the accident (E-1, 276.82 mg/kg) and tended to decrease as it moved eastward. Meanwhile, the concentrations from SE and NE (4.96~28.98 mg/kg) tended to be lower than the samples near the accident site. As a result, the concentration of hydrogen fluoride was reduced to a low concentration within 2 km from the accident site (<5 mg/kg), and the actual damage range was estimated to be around 2.2 km. Therefore, it is suggested that the results are similar to those of alternative accident scenarios calculated by OCA (about 1.9 km). CONCLUSION: It is difficult to estimate the chemical accident-affecting range/region by the OCA evaluation, because it is not possible to input all physicochemical parameters. However simultaneous measurement of the residual contamination in the environment will be very helpful in determining the diffusion range of actual chemical accident.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.506-510
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• 2009

The effects of various organic wastes on anaerobic fermentative hydrogen production were studied using enriched mixed microflora in batch tests. Rotten fruit, corn powder and organic wastewater enriched with sulfate (up to 1,000 mg/L) were used for experiments. Maximum hydrogen production (547.1 mL) was observed from rotten apple with initial substrate concentration of 132.2 g COD/L. The experimental result on sulfate enriched organic wastewater indicated that hydrogen production is not adversely influenced by relatively high sulfate concentration. Residual sulfate content remained at 96-98 % after 75 hours of reaction, which showed that no major sulfate reduction was occurred at pH 5.3-5.5 in the reactor. The volatile fatty acid (VFA) fractions produced during the reaction was in the order of butyrate > acetate > propionate in all experiments. The results of this study would be useful for controlling the conditions on fermentative hydrogen production using different feedstocks.

• Journal of the Korean Electrochemical Society
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• v.13 no.4
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• pp.277-282
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• 2010

Durability of automotive polymer electrolyte membrane fuel cell (PEMFC) strongly depends the startup/shutdown procedure. Formation of hydrogen/air boundary in the anode gas channel, so-called reverse current condition, particularly induces fast degradation of the cathode. Under the reverse current condition, high voltage is present at the cathode facing air in the anode gas channel and is a function of residual oxygen concentration in the gas channels, that increases with storage time and reaches 21% (air) eventually. In this study, effects of residual oxygen concentration in a PEMFC on degradation of the PEMFC.