• Korean Chemical Engineering Research
• /
• v.43 no.3
• /
• pp.352-359
• /
• 2005

This work has studied the changes of pH in both of anodic and cathodic chambers of a divided cell due to the electrolytic split of water during the ammonia decomposition to nitrogen, and has studied the continuous decomposition characteristics of ammonia in a multi-cell stacked electrolyzer. The electrolytic decomposition of ammonia was much affected by the change of pH of ammonia solution which was caused by the water split reactions. The water split reaction occurred at pH of less than 8 in the anodic chamber with producing proton ions, and occurred at pH of more than 11 in the cathodic chamber with producing hydroxyl ions. The pH of the anodic chamber using an anion exchange membrane was sustained to be higher than that using a cation exchange membrane, which resulted in the higher decomposition of ammonia in the anodic chamber. By using the electrolytic characteristics of the divided cell, a continuous electrolyzer with a self-pH adjustment function was newly devised, where a portion of the ammonia solution from a pHadjustment tank was circulated through the cathodic chambers of the electrolyzer. It enhanced the pH of the ammonia solution fed from the pH-adjustment tank into the anodic chambers of the electrolyzer, which caused a higher decomposition yield of ammonia. And then, based on the electrolyzer, a salt-free ammonia decomposition process was suggested. In that process, ammonia solution could be continuously decomposed into the environmentally-harmless nitrogen gas up to 83％, when chloride ion was added into the ammonia solution.

• Journal of dental hygiene science
• /
• v.10 no.2
• /
• pp.101-107
• /
• 2010

The purpose of this study was to analysis know the important oral environmental factors which affect halitosis components of the adult in order to provide basic data for halitosis prevention and establish a device to eliminate halitosis efficiently. The 97 adults who visited at the Dental Clinic in Metropolis (M=68, F=30) participated in this study that performed from March in 2009 to in 2010. The obtained results through items as caries status, periodontal status, salivary flow, the viscosity, pH, Snyder test, plaque deposit, tongue plaque and halitosis check were as followings. The average shame of halitosis components appeared at hydrogen sulfide 36.71 ppb methyl mercaptan 31.46ppb dimethyl sulfide 54.33 ppb and Ammonia 22.60 ppm. The normality and the detection comparative result dimethyl sulfide above reverse appeared highly at 46.9%, ammonia appeared highly at 52%. According to the Hydrogen sulfide level was a high relationship among age, CPI, tongue coat status, DMFT index which were statistically significant (p<0.05). According to the quantity of hydrogen sulfide level there was relationship where tongue coat status Saliva flow rate considers statistically(p<0.05). The quantity of methyl mercaptan level there was relationship where Dimethyl sulfide level, tongue coat status, Saliva flow rate considers statistically(p<0.05). The quantity of Dimethyl sulfide level there was relationship where Hydrogen sulfide level, ammonia level, tongue coat status, Saliva pH and Saliva flow rate considers statistically(p<0.05). Ammonia level there was relationship where Methyl mercaptan level, CPI, and Saliva flow rate considers statistically(p<0.05).

• Applied Chemistry for Engineering
• /
• v.18 no.2
• /
• pp.116-120
• /
• 2007

The synthesis of 1-[2-(3-{7-oxabicyclo[4.1.0]heptyl} 1,1,3,3-tetramethyl-disiloxane (Mono), which is a key intermediate for the synthesis of monomers applied for photopolymer systems based on the cationic ring opening polymerization, was studied. Mono was successfully synthesized by the hydrosilylation reaction of 4-vinyl-1-cyclohexene 1,2-epoxide (VCHO) with an excess amount of 1,1,3,3-tetramethyldisiloxane (TMDS) in the presence of a Speier catalyst. The structure and the purity of Mono were characterized by FT-IR, $^1H-NMR$, and $^{29}Si-NMR$. The optimum conditions for the hydrosilyation reaction were found to be 1:4 molar ratio of VCHO to TMDS and 5 ppm of the catalyst at the temperature of $55^{\circ}C$.

• Journal of Adhesion and Interface
• /
• v.5 no.1
• /
• pp.3-11
• /
• 2004

In this work, the cure behaviors of the DGEBA/PMR-15 blends initiated by N-benzylpyrazinium hexafluoroantimonate (BPH) as a cationic latent catalyst were performed in DSC and DMA analyses. And, the thermal stabilities were carried out by TGA analysis and their mechanical interfacial properties of blends were measured in the context of critical stress intensity factor ($K_{IC}$). As a result, the curing activation energy ($E_a$) determined from Ozawa's equation in DSC and the relaxation activation energy ($E_r$) from DMA were increased with increasing PMA-15 content. Also, the thermal stabilities obtained from the integral procedural decomposition temperature (IPDT) and the glass transition temperature ($T_g$) were highly improved with increasing the PMR-15 content, which were probably due to the high heat resistance. And, the $K_{IC}$ showed a similar behavior with $E_a$, which was attributed to the improving of the interfacial adhesion or hydrogen bondings between intermolecular chains.

• Membrane Journal
• /
• v.15 no.3
• /
• pp.247-254
• /
• 2005

Chitosan film has potential applications in agriculture, food, and pharmacy. However, films made only from chitosan lack gas barrier and have poor mechanical properties. For enhanced gas barrier and mechanical properties, chitosan/clay nanocomposites have been prepared with montmorillonite (MMT) which is a layered structure of clays and chitosan. The cationic biopolymer, chitosan is intercalated into $Na^+-montmorillonite$ through cationic exchange and hydrogen bonding process. Diluted acetic acid is used as solvent f3r dissolving and dispersing chitosan. Chitosan was intercalated or exfoliated in MMT and it was confirmed by X-ray diffraction method. D-spacing of the characteristic peak from MMT plate in chitosan/clay nanocomposites was moved and diminished. The thermal stability and the mechanical properties of the nanocomposites are measured by TGA and Universal Testing Machine. Gas permeability through the chitosan/clay nanocomposites films decreased due to increased tortuosity made by intercalation of clay in chitosan.

• Journal of Korean Society of Environmental Engineers
• /
• v.29 no.7
• /
• pp.820-825
• /
• 2007

Earthworm casting was the natural fertilizer that contained high concentrations of nutrients such as nitrogen, phosphate and potassium and of over $10^8$ CFU/ml of microorganisms. Greater than 80% of feed was excreted through the fermentation by the intestinal enzyme, after worm had eaten feeds such as fallen leaves and rotten roots under the ground. Also, the soil structure of casting was known to be very efficient in the aspects of the porosity, the water permeability, and deodorizing activities. In this research, the biofilter packed with a biomedia made of casting and waste polyurethane foam, a binder, which helped to improve the durability and perpetuity of casting, was investigated to degrade malodorous hydrogen sulfide gas. The biomedia had no need of extra supply of nutrients and of microbial inoculations. On the beginning of the operations, it showed 100% removal of hydrogen sulfide gas without lag phase. At SV of 50 $h^{-1}$, hydrogen sulfide gas from the outlet of the biofilter was not detected, when inlet concentration increased to 450 ppmv. After that, removal efficiency decreased as increasing inlet hydrogen sulfide concentration. Hydrogen sulfide removal was maintained at almost 93% until inlet concentration was increased up to 950 ppmv, at which the elimination capacity of $H_2S$ was 61.2 g $S{\cdot}m^{-3}{\cdot}h^{-1}$. Maximum elimination capacity guaranteing 90% removal was 61.2, 65.9, 84.7, 89.4 g $S{\cdot}m^{-3}{\cdot}h^{-1}$ at SV ranging from 50 $h^{-1}$ to 300 $h^{-1}$, but was 59.3 g $S{\cdot}m^{-3}{\cdot}h^{-1}$ at SV of 400 $h^{-1}$. The results calculated from Michaelis-Menten equation revealed that $V_m$ increased from 66.04, 88.96, 117.35, 224.15, to 227.54 g $S{\cdot}m^{-3}{\cdot}h^{-1}$ with increasing space velocity in the range of 50 $h^{-1}$ to 400 $h^{-1}$. However, saturation constant$(K_s)$ decreased from 79.97 ppmv to 64.95 and 65.37 ppmv, and then increased to 127.72 and 157.43 ppmv.

• Korean Journal of Food Science and Technology
• /
• v.36 no.2
• /
• pp.333-338
• /
• 2004

Antioxidant activities of water extracts of 20 medicinal plants (1 mg/mL) on peroxidation of linolic acid were evaluated by thiocyanate method, among which 11 showed strong antioxidant activity (> 70%). Higher hydroxy radical scavenging activity (> 60%) were shown in Corner officinalis, Acanthopanax sessiliflorus, and Epimedium koreanum than the other plants. Epimedium koreanum than the other plants extract showed highest superoxide radical scavenging activity (42%). Total polyphenol contents ranged from $2.6\;(Polygonatum\;odoratum){\sim}81.2(Epimedium\;koreanum)\;mg/g$. Direct correlation between the antioxidant activity and polyphenol content (r=0.8) was established through simple regression analysis. $IC_{50}$ for selected four plant extracts, showing highest polyphenol contents and antioxidant activities, were significantly higher than positive control. Total antioxidant activity of vitamin c was significantly lower than those of Acanthopanax sessiliflorus, Epimedium koreanum, and Erythrina variegata. Superoxide radical scavenging activity of Acanthopanax sessiliflorus was similar to BHA. Results suggest water extracts of some medicinal plants could be potential candidates for natural antioxidants.

• Journal of the Korean Chemical Society
• /
• v.28 no.4
• /
• pp.210-216
• /
• 1984

Solvatochromic comparison methods were applied to determine Taft's solvent parameters, ${\pi}^{\ast}$(solvent polarity-polarizability), ${\alpha}$(solvent hydrogen bond donor acidity) and ${\beta}$ (solvent hydrogen bond acceptor basicity) for MeOH-MeCN solvent mixtures. Swain's solvent parameters A(anion solvation scale) and B(cation solvation scale) were also determined by least square fitting of kinetic data in the same binary solvent mixtures. It was found that: (i)${\beta}$ depends on the basicity of the solvent and increases with the MeOH content owing to the increase in polymeric structure of methanol; (ii) ${\pi}^{\ast}$depends on the dipole moment of the solvent and increases with the MeCN content of the solvent; (iii) ${\alpha}$ increases rapidly with the MeOH content as the hydrogen bond donor acidity of the solvent mixtures increases. Taft's reaction constants a and s and Swain's reaction constants a and b were determined for the reactions reported from our laboratory previously using solvent parameters determined in this work. No meaningful inter-relationship was found between the two set of reaction parameters, but a good linear correlation was found between the ratios a/s and a/b. Solvent effect on the reaction mechanism, substituent effect and leaving group ability were examined in the light of these reaction constants ratios.

• Korean Journal of Food Science and Technology
• /
• v.34 no.6
• /
• pp.998-1001
• /
• 2002

Micro-LC method for the quantitative determination of hydrogen peroxide in foods has been established. This method was carried out on cation-exchange resin gel column using distilled water as mobile phase with 50 mM sodium sulfate as electrolyte. The detection was performed with an electrochemical detector (ECD) at 0.6 voltage. Under this analytical condition, the recovery rates of hydrogen peroxide in tomato and lemon were 98.3 and 97.4%, respectively. Among 28 food types, hydrogen peroxide concentrations were 0.6, 0.5, 1.9, 0.9, 0.5, 0.6, 0.9, 0.8, and 0.4 ppm in banana, peach, orange, strawberry, pepper, onion, cucumber, burdock, and egg plant, respectively, Whereas none was detected in remaing 19 samples.

• Journal of Energy Engineering
• /
• v.20 no.3
• /
• pp.171-177
• /
• 2011

PVA/GLA/$Al_2O_3{\cdot}3SiO_2$ composite membranes were prepared through the reaction polyvinyl alcohol (PVA) with glutaraldehyde (GLA) as a cross-linking agent and subsequently adding aluminum silicate ($Al_2O_3{\cdot}3SiO_2$) as an inorganic material. The water uptake decreased as the GDL contents increased due to cross-linking process of PVA with GDL, and the ion conductivity increased as the $Al_2O_3{\cdot}3SiO_2$ contents increased in PVA/GLA/$Al_2O_3{\cdot}3SiO_2$ composite membranes. The cross-linking structure of the polymers was confirmed using IR and the tendency of water uptake. The thermal analysis of the copolymers was carried out by TGA. TGA results showed that PVA/GLA composite membrane were more heat-resistant than PVA due to the cross-linking of PVA, and the heat stability of the composite membranes improved much more as the concentration of $Al_2O_3{\cdot}3SiO_2$ increased. Membranes prepared in this study seem to be have thermal stability and increase a tendency of the cation conductivity up to $60^{\circ}C$, but to be exhibit lower performance tendency at over $90^{\circ}C$. Therefore, it is necessary to do more aggressive effort to explore the possibility of application as an ion-conductive composite electrolyte.