• Journal of Korean Society of Water and Wastewater
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• v.25 no.6
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• pp.815-824
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• 2011

In this study, a non-thermal plasma system was employed to simultaneously remove odorous compounds and organic sludge. The system consisted of two reactors; the first one was the non-thermal plasma reactor where ozone was produced by the plasma reaction and the ozone oxidized hydrogen sulfide, the model odorous compound, and then the ozone-laden gas stream was introduced to the second reactor where wasted sludge was disintegrated and solubilized by ozone oxidation. In this study, the gas retention time (GRT) and the hydraulic retention time (HRT) were changed in the two-reactor system, and the effects of GRT and HRT on reduction efficiencies of odor and sludge were determined. As the GRT increased, the ozone concentration increased resulting in an increasing efficiency of hydrogen sulfide removal. However, the overall ozone loading rate to the second sludge reactor was the same at any GRT, which resulted in an insignificant change in sludge reduction rate. When HRTs in the sludge reactor were 1, 2, 4 hours, the sludge reduction rates were approximately 30% during the four-hour operation, while the rate increased to 70% at the HRT of 6 hours. Nevertheless, at HRTs greater than 4 hours, the solubilization efficiency was not proportionally increased with increasing specific input energy, indicating that an appropriate sludge retention time needs to be applied to achieve effective solubilization efficiencies at a minimal power consumption for the non-thermal plasma reaction.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.10
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• pp.702-708
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• 2012

Tetrafluoromethane ($CF_4$) has been used as etching and Chemical Vapor Deposition (CVD) gases for semiconductor manufacturing processes. These gases need to be removed efficiently because of their strong absorption of infrared radiation and long atmospheric lifetimes which cause the global warming effect. Also, the wastewater including the fluorine is caused by of the ground water pollution. Long-term consumption of water containing excessive fluoride can lead to fluorosis of the teeth and bones. The wastewater including the fluorine among the by-product which is generated by using the waterjet plasma after destroying $CF_4$ by HF is generated. The system which can remove the hydrogen fluoride among the wastewater by using the electrocoagulation using this wastewater the aluminum electrode was developed. The operating condition such as initial pH, electrocoagulation time, wastewater flow rate, current density were investigated experimentally using a electrocoagulation. Through the parametric studies, the highest hydrogen fluoride destruction of 85% was achieved at 3.5 initial pH, 10 min electrocoagulation time, 10 mL/min wastewater flow rate and $159A/m^2$ current density.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.7
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• pp.4675-4681
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• 2014

This study examined the $H_2S$ removal characteristics, such as breakthrough time, adsorption capacity, and adsorption rate of adsorbents between Zeolite 3A and DETOX in terms of the $H_2S$ inflow concentration and adsorption temperature. The adsorption capacity of Zeolite 3A increased with increasing mass flow rate of hydrogen sulfide($H_2S$) inflow, but the breakthrough time decreased. On the other hand, both the adsorption capacity and breakthrough time of DETOX decreased with increasing mass flow rate of $H_2S$ inflow. The adsorption capacity and breakthrough time of Zeolite 3A decreased with increasing adsorption temperature but those of DETOX increased. The adsorption capacity of DETOX was higher than that of Zeolite 3A by a factor of 2.5 - 16.4 because the collision frequency that overcomes the activation energy barrier increased with increasing adsorption temperature. For Zeolite 3A and DETOX, the adsorption rate of $H_2S$ increased with increasing mass flow rate of $H_2S$ inflow and adsorption temperature. The adsorption rate of $H_2S$ for Zeolite 3A was 4 times as much as that for DETOX. For the removal of $H_2S$ in biogas, DETOX had an advantage over Zeolite 3A because DETOX had a much longer breakthrough time and greater adsorption capacity in the temperature range of 308~318K than Zeolite 3A.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 1998.10a
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• pp.1-1
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• 1998

Advanced (Chemical) oxidation processes (AOP) differ from most conventional ones in that hydroxyl radical(OH.) is considered to be the primary oxidant. Hydroxyl radicalcan react non-selectively with a great number of organic and inorganic chemicals. The typical rate constants of true hydroxyl radical reactions are in the range of between 109 to 1012 sec-1. Many processes are possible to generate hydroxyl radical. These include physical and chemical methods and their combinations. Physical means involves the use of high energy radiation such as gamma ray, electron beam, and acoustic wave. Under an applied high energy radiation, water molecules can be decomposed to yield hydroxyl radicals or aqueous electrons. Chemical means include the use of conventional oxidants such as hydrogen peroxide and ozone, two of the most efficient oxidants in the presence of promoter or catalyst. Hydrogen peroxide in the presence of a catalyst such as divalent iron ions can readily produce hydroxyl radicals. Ozone in the presence of specific chemical species such as OH- or hydrogen peroxide, can also generate hydroxyl radicals. Finally the combination of chemical and physical means can also yield hydroxyl radicals. Hydrogen peroxide in the presence of acoustic wave or ultra violet beam can generate hydroxyl radicals. The principles for hydroxyl radical generation will be discussed. Recent case studied of AOP for water treatment and other environmental of applications will be presented. These include the treatment of contaminated soils using electro-Fenton, lechate treatment with conventional Ponton, treatment of coal for sulfur removal using sonochemical and the treatment of groundwater with enhanced sonochemical processes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.46-49
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• 2003

Chemical mechanical polishing (CMP) is an essential dielectric planarization in multilayer microelectronic device fabrication. In the CMP process it is necessary to minimize the extent of surface defect formation while maintaining good planarity and optimal material removal rates. The polishing mechanism of W-CMP process has been reported as the repeated process of passive layer formation by oxidizer and abrasion action by slurry abrasives. Thus, it is important to understand the effect of oxidizer on W passivation layer, in order to obtain higher removal rate (RR) and very low non-uniformity (NU%) during W-CMP process. In this paper, we compared the effects of oxidizer or W-CMP process with three different kind of oxidizers with 5% hydrogen peroxide such as $Fe(NO_3)_3$, $H_2O_2$, and $KIO_3$. The difference in removal rate and roughness of W in stable and unstable slurries are believed to caused by modification in the mechanical behavior of $Al_3O_3$ particles in presence of surfactant stabilizing the slurry.

• Journal of Korean Society on Water Environment
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• v.30 no.6
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• pp.653-657
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• 2014

Effects of $H_2O_2$ addition for fenton oxidation on iron coagulation for treatment of phosphorus species, such as orthophosphate, metaphosphate, pyrophosphate, organic phosphate, were investigated. The effects of coagulant dosage, hydrogen peroxide dosage and the combined sequence ferric coagulation and $H_2O_2$ addition for fenton oxidation and coagulation were studied. The characteristics of floc growth rate were monitored using the PDA. The removal efficiencies of phosphorus species by iron coagulation were increased as Fe/P molar ratio increased. However, the removal efficiencies of metaphosphate, pyrophosphate, organic phosphate by a ferric coagulation were not increased as Fe/P molar ratio increased. The removal efficiency of metaphosphate, pyrophosphate, organic phosphate was increased by using iron coagulation and $H_2O_2$ addition for fenton oxidation. The result indicated that non-reactive phosphorus after iron coagulation was changed to reactive phosphorus by $H_2O_2$ addition for fenton oxidation and the oxidized iron enhanced the coagulation efficiencies.

• Journal of Environmental Science International
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• v.1 no.2
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• pp.105.1-113
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• 1992

The present study was performed to develop the removal system of the offensive gases, including hydrogen sulfide of acid gas, ammonia or amice of base gas, from the nightsoil treatment plant. In order to remove the offensive gases, the Fe-EDTA system liquid phase catalytic oxidation method with the bubble lift column reactor was employed. From the results obtained, it was confirmed that the offensive gases can be deodorized simultaneously and also hydrogen sulfide of acid gas, ammonia of base gas completely removed at pH 6.45. In addition, as input gases feed rate the efficiency of acid gas did not change but the efficiency of base gases decreased to approximately 90 % at pH 6, 0. From the result of particle size analyzer, it was found that the particle sizes including sulfur and other impurites grew up to $21{\mu}m$ over 72hour reaction time.

• Analytical Science and Technology
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• v.28 no.5
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• pp.353-360
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• 2015

Boiling is an efficient removal method to reduce radon in groundwater when ventilating indoor air. 13 groundwater samples with various radon concentrations were used to evaluate the reduction rate of radon with heating temperature and time. The groundwater samples were obtained by Bladder pump and on-situ measurements such as dissolved oxygen (DO) and hydrogen concentration (pH) and so on were carried out by a flow cell system isolated from the ambient atmosphere environment. All samples for measuring radon in groundwater were analyzed by liquid scintillation counter (LSC). The experiment result showed that increasing groundwater temperature enhanced radon removal rate but the initial radon concentration with high level lowered the removal rate. This means that radon reduction in groundwater by heating needs more heating energy and longer heating time with radon concentrations. Radon removal rate in groundwater, therefore, mainly depends on the initial radon concentration, heating temperature, and heating time.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.1
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• pp.45-53
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• 2015

The objective of this study is to develop a gas pro-treatment system for DME synthesis, wherein this system separates $CO_2$ from Flaring gas as Membrane, in order to save raw material ($CH_4$) cost of DME. In this study, hollow fiber membrane is developed, which is able to separate high-pressure gas, supported by polysulfone and coated with amorphous fluorinated polymer. Throughout the evaluation of the membrane's separation characteristics, the membrane is applied to this system. The membrane is designed by 2 stages for over 90% removal rate of $CO_2$ and over 90% recovery rate of $CH_4$. The bench scale of pro-treatment system is developed as $25Nm^3/hr$.

• Environmental Engineering Research
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• v.23 no.2
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• pp.129-135
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• 2018

The aim of this study is to assess the applicability of ferrate(VI) in the efficient treatment of aqueous waste contaminated with potassium hydrogen phthalate (KHP) which is known to be a potent endocrine disrupting chemicals. Simulated batch reactor operations were conducted at a wide range of pH (7.0 to 12.0) and molar ratios of KHP to ferrate(VI). Kinetic studies were performed in the degradation process and overall rate constant was found to be 83.40 L/mol/min at pH 8.0. The stoichiometry of ferrate(VI) and KHP was found to be 1:1. Further, lower pH values and higher KHP concentrations were favoured greatly the degradation of KHP by ferrate(VI). Total organic carbon analysis showed that partial mineralization of KHP was achieved. The presence of several background electrolytes were studied in the degradation of KHP by ferrate(VI).