• Journal of Environmental Health Sciences
• /
• v.47 no.6
• /
• pp.540-547
• /
• 2021

Background: Indoor air pollutants are caused by a number of factors, such as coming in from the outside or being generated by internal activities. Typical indoor air pollutants include nitrogen dioxide and carbon monoxide from household items such as heating appliances and volatile organic compounds from building materials. In addition there is carbon dioxide from human breathing and bacteria from speaking, coughing, and sneezing. Objectives: According to recent research results, most indoor air pollution is known to be greatly affected by internal factors such as burning (biomass for cooking) and various pollutants. These pollutants can have a fatal effect on the human body due to a lack of ventilation facilities. Methods: We fabricated a polydopamine (PDA) layer with Ti substrates as a coating on supported glass fiber fabric to enhance its photo-activity. The PDA layer with TiO₂ was covalently attached to glass fiber fabric using the drop-casting method. The roughness and functional groups of the surface of the Ti substrate/PDA coated glass fiber fabric were verified through infrared imaging microscopy and field emission scanning electron microscopy (FE-SEM). The obtained hybrid Ti substrate/PDA coated glass fiber fabric was investigated for photocatalytic activity by the removal of ammonia and an epidermal Staphylococcus aureus reduction test with lamp (250 nm, 405 nm wavelength) at 24℃. Results: Antibacterial properties were found to reduce epidermal staphylococcus aureus in the Ti substrate/PDA coated glass fiber fabric under 405 nm after three hours. In addition, the Ti substrate/PDA coated glass fiber fabric of VOC reduction rate for ammonia was 50% under 405 nm after 30 min. Conclusions: An electron-hole pair due to photoexcitation is generated in the PDA layer and transferred to the conduction band of TiO₂. This generates a superoxide radical that degrades ammonia and removes epidermal Staphylococcus aureus.

• Applied Chemistry for Engineering
• /
• v.29 no.3
• /
• pp.298-302
• /
• 2018

Photocatalytic properties of nitrogen doped titanium dioxide were investigated. Photocatalytic degradation of methylene blue under UV and visible light was carried out to characterize N-doped $TiO_2$. The result of XPS indicated that nitrogen atoms substitute for oxygen sites within the crystal structure of $TiO_2$. In the UV-Vis DRS spectra, N-doped amorphous $TiO_2$ absorbed UV light with little absorption of visible light, while the absorption of visible light of amorphous/anatase $TiO_2$ remarkably increased. Methylene blue photocatalytic degradation appeared by the irradiation of UV or visible light onto the N-doped anatase phase of $TiO_2$. However, the degradation rate of visible light was lower than that of UV light. The photocatalytic degradation rate of the amorphous/anatase $TiO_2$ sample was higher than that of the anatase $TiO_2$. These results indicate that the high surface area of amorphous/anatase $TiO_2$ sample, which was about three times larger than those of the anatase $TiO_2$ sample, may be related to small particles of N-doped anatase $TiO_2$.

• Journal of Korean Society of Environmental Engineers
• /
• v.28 no.2
• /
• pp.191-196
• /
• 2006

The injection of ozone, produced by dielectric barrier discharge, into the exhaust gas gives rise to a rapid oxidation of NO that is the main component of nitrogen oxides($NO_x$) in most practical exhaust gases. Once NO is converted into $NO_2$, it on readily be reduced to $N_2$ in the next step by a reducing agent such as sodium sulfide and sodium sulfite. The reducing agents used ca also remove $SO_2$ effectively, which makes it possible to treat $NO_x\;and\;SO_2$ simultaneously. The present two-step process made up of an ozonizing chamber and an absorber containing a reducing agent solution was able to remove about 95% of the $NO_x$ and 100% of the $SO_2$, initially contained in the simulated exhaust gas. The formation of $H_2S$ from sodium sulfide was prevented by using a strong basic reagent(NaOH) together with the reducing agent. The removal of $NO_x$\;and\;SO_2$ was more effective for $Na_2S$ than $Na_2SO_3$.

• Journal of Korean Society of Environmental Engineers
• /
• v.36 no.4
• /
• pp.277-285
• /
• 2014

The usage of efficient microorganism (EM) is increasing in concern for server purposes including odor removal during carcasses degradation. In this study, we have studied the type of soil and its effect on efficient microorganisms for the removal of odorous gases during buried carcasses degradation in lab-scale reactor. The carcasses are buried in the reactor with various soil types such as normal soil, 20% sandy and 20% clay soil with the efficient microorganism KEM. The efficient microorganisms KEM have the ability to stabilize the degradation of carcasses of the burial site. We have focused on the analysis of odorous gases such tri-methylamine (TMA), hydrogen sulfide ($H_2S$), methyl mercaptan (MM), dimethyl sulfide (DMS), dimethyl disulfide (DMDS), carbon dioxide ($CO_2$), and methane ($CH_4$) along with the changes of microbial community changed during complete degradation of buried carcasses for a year. The results suggested that the 20% sandy soil contain lesser level of $H_2S$ and MM (0.09 and 0.35 mg) but 20% clay has higher nitrogen compound removing effect and leave only less amount of ammonia and TMA (0.31 and 2.06 mg). The 20% sandy soil also has the ability to breakdown the carcasses more quality compared with other types of soil. Based on the data obtained in this study suggesting that, the use of 20% sandy soil can effectively control sulfur compounds whereas 20% clay soil controls nitrogen compounds in the buried soil. Depending on the type of the soil, the dominant of microbial communities and the distribution was change.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.25 no.6
• /
• pp.780-787
• /
• 2019

As a carbon-free, green growth alternative, internal and external interest in hydrogen energy and technology is growing. Hydrogen was added to co-axial methane, methane-propane, and methane-propane-ethane diffusion flames, which are the main ingredients of LNG, to evaluate its effect on flame formation and combustion products. The variation in combustion products produced by adding hydrogen gradually to diffusion pyrolysis at room temperature and normal pressure conditions was observed experimentally by using a gas analyzer, and the shape of diffusion pyrolysis was observed step by step using a digital camera. The experimental results showed that the production volume of nitrogen oxides tended to increase and became close to linear as hydrogen was added to the diffusion pyrotechnic. This is because the relatively high temperature of heat insulation and fast combustion speed of hydrogen facilitated the production of thermal NOx. On the other hand, CO2 production tended to decrease as hydrogen was added to reduce the overall carbon ratio contained in the mixed diffusion flame of methane, methane-propane, and methane-ethane-propane. This means that the mixed fuel use of LNG-hydrogen in ships may potentially reduce emissions of CO2, a greenhouse gas.

• Tuberculosis and Respiratory Diseases
• /
• v.59 no.6
• /
• pp.690-695
• /
• 2005

Nitric acid is an oxidizing agent used in metal refining and cleaning, electroplating, and other industrial applications. Its accidental spillage generates oxides of nitrogen, including nitric oxide (NO) and nitrogen dioxide ($NO_2$), which cause chemical pneumonitis when inhaled. The clinical presentation of a nitric acid inhalation injury depends on the duration and intensity of exposure. In mild cases, there may be no symptoms during the first few hours after exposure, or the typical symptoms of pulmonary edema can appear within 3-24 hours. However, in cases of prolonged exposure, progressive pulmonary edema develops instantaneously and patients may not survive for more than 24 hours. We report a case of a 44-year-old male who was presented with acute respiratory distress syndrome after nitric acid inhalation. He complained of cough and dyspnea of a sudden onset after inhaling nitric acid fumes at his workplace over a four-hour period. He required endotracheal intubation and mechanical ventilation due to fulminant respiratory failure. He was managed successfully with mechanical ventilation using positive end expiratory pressure and systemic corticosteroids, and recovered fully without any deterioration in his pulmonary function.

• Journal of Korean Society for Atmospheric Environment
• /
• v.33 no.2
• /
• pp.87-96
• /
• 2017

In this study, 4 gases containing typical chlorinated volatile organic compounds (VOCs) were treated by ultraviolet (UV) irradiation. The typical chlorinated VOCs are dichloromethane (DCM), trichloromethane (TCM), carbon tetrachloride (CTC) and trichloroethylene (TCE). The removal efficiency (RE) and the products of chlorinated VOCs by UV irradiation are investigated. At this time, 2 types of background gas (air and nitrogen) were used to figure out the RE by photooxidation and photolysis. The specification of UV-lamp used in this study was low-pressure mercury lamp emitting wavelength of 185~254 nm. The experimental conditions were set as initial VOC concentration of $180{\pm}10ppm$, empty bed retention time (EBRT) of 53 s, temperature of $23{\pm}2^{\circ}C$ and relative humidity of $65{\pm}5%$. In the photolysis condition with nitrogen ($N_2$) as background gas, the averaged RE of the 4 types of chlorinated VOCs was about 24% higher than that with photooxidation; and the REs of VOCs except CTC were confirmed as >99%. The composition of off-gases after UV photooxidation in air was investigated and several intermediates from DCM, TCM and TCE were detected by GC/MS. Among them, phosgene which is a toxics was detected as an intermediate of TCM. In addition, the concentration of carbon dioxide ($CO_2$) in the off-gases was measured to calculate the mineralization rate (MR). With the photooxidation, TCE showed the highest RE (>99%) while MR was the lowest (17%); and the MR of DCM was the highest (86%). In addition, particulate matters (PM) in the off-gases was also detected and high concentrated $PM_{10}$ ($21,580{\mu}g{\cdot}m^{-3}$) and $PM_{2.5}$ ($6,346{\mu}g{\cdot}m^{-3}$) were detected in TCE off-gas. More than 99% of the chlorinated VOCs could be removed using UV254-185 nm lamp, while it is necessary to conduct further studies on the production and treatment of secondary pollutants.

• Membrane Journal
• /
• v.23 no.1
• /
• pp.70-79
• /
• 2013

The $N_2$ back-flushing period (FT) and time (BT) were investigated in hybrid process of ceramic microfiltration and PES (polyethersulfone) beads loaded with titanium dioxide ($TiO_2$) photocatalyst for advanced drinking water treatment in viewpoints of membrane fouling resistance ($R_f$), permeate flux (J), and total permeate volume ($V_T$). As decreasing FT and increasing BT, $R_f$ decreased and J increased, and finally the maximum $V_T$ could be acquired at FT 10 min and BT 30 sec. In FT effect experiment, treatment efficiencies of turbidity and dissolved organic matters (DOM) were the highest at no back-flushing (NBF) because of dramatic membrane fouling. As result of BT effect, the treatment efficiencies were the maximum at BT 30 sec, which was different with the FT result. Because the photocatalyst beads could be cleaned effectively as decreasing FT and increasing BT, turbidity treatment efficiency increased a little from 95.4% to 97.5% as decreasing FT, and from 95.9% to 98.5% as increasing BT. Also DOM treatment efficiency increased from 70.8% to 80.6% as decreasing FT, and from 75.1% to 85.8% as increasing BT. The optimal condition, where the treatment efficiencies and $V_T$ were the maximum, should be FT 10 min and BT 30 sec in our experimental range.

• Korean Journal of Environmental Agriculture
• /
• v.27 no.4
• /
• pp.428-434
• /
• 2008

The objective of this study is to investigate the effect of the level of $CO_2$ (370 and $650{\mu}mol\;mol^{-1}$) and temperature (ambient and ambient+$5^{\circ}C$) on tomato growth and fruit characteristics as affected by the application rate of N-fertilizer (68 and $204\;N\;kg\;ha^{-1}$), for the purpose of evaluating the influence of elevated $CO_2$ and temperature on tomato crop. The elevated atmospheric $CO_2$ and temperature increased the plant height and stem diameter for tomato crop, while the differences among the nitrogen(N) application rates were not significantly different. Under the elevated $CO_2$, temperature, and a higher N application rate, the biomass of aerial part increased. The fruit yield showed the same result as the biomass except for the elevated temperature. The elevated temperature made the size of fruit move toward the small, but the elevated $CO_2$ and the application of N-fertilizer were vice versa. The sugar content and pH of fruit juice were affected by nitrogen application rate, but not by the elevated $CO_2$ and temperature. These results showed that both the elevated $CO_2$ and temperature stimulated the vegetative growth of aerial parts for tomato, but each effects on the yield of fruit showed an opposite result between the elevated temperature and $CO_2$. In conclusion, the elevated $CO_2$ increased tomato yield and the ratio of large size of fruit, but the elevated temperature did not. Therefore, to secure the productivity of tomato as nowadays in future environment, it will need to develop new breeder as high temperature-tolerable tomato species or new type of cropping systems.

• Applied Chemistry for Engineering
• /
• v.28 no.1
• /
• pp.112-117
• /
• 2017

This study demonstrated the emission of combustion gases of medium density fibreboard (MDF)s coated with piperazinomethyl-bis-phosphonic acid (PIPEABP), methylpiperazinomethyl-bis-phosphonic acid (MPIPEABP), N,N-dimethylethylenediaminomethyl-bis-phosphonic acid (MDEDAP), or bis-(dimethylaminomethyl) phosphinic acid (DMDAP). Each MDFs were coated in three times with a brush with 15 wt% aqueous solution of the phosphorus-nitrogen acid additives. After the specimens were dried at room temperature, the emission of combustion gases was tested using a cone calorimeter (ISO 5660-1, 2). The peak smoke production rate ($SPR_{peak}$) of the specimens coated with phosphorus-nitrogen acids was 18.5 to 41.5%, which is lower than that of using the virgin plate. However, the production of peak carbon monoxide ($CO_{peak}$) was 6.7 to 24.2% higher than that of using the virgin plate. Also, the peak carbon dioxide ($CO_{2peak}$) was 4.2 to 24.4% lower than that of using virgin plate. While the peak oxygen depletion rate was much higher than the level of 15%, which can be fatal to humans and the resulting risk could thus be eliminated. Overall, the combustibility of coated specimens was partially suppressed, but showed a negative effect on the reduction of carbon monoxide.