• Journal of the Korean Ceramic Society
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• v.31 no.5
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• pp.505-512
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• 1994

It has been reported that a biocement obtained by mixing CaO-SiO2-P2O5 glass powder and ammonium phosphate solution has biocompatibility as well as high strength. However, the compositional dependence on its hardening and hydroxyapatite formation phenomena has not been studied. Therefore, the main objective of this work is to study the effects of P2O5, MgO in CaO-SiO2 system glass on the hardening and hydroxyapatite formation. When more than 50 mole% of CaO containing CaO-SiO2 glasses was reacted with ammonium phosphate solution, CaNH4PO4.H2O crystal was formed, but the glass with less than 50 mol% of CaO formed (NH4)2HPO4 and NH4H2PO4 crystals which are derived from ammonium phosphate solution without reacting with the glasses. As the amount of P2O5 in CaO-SiO2-P2O5 glass system was increased, the formation of CaNH4PO4.H2O crystal was enhanced. When those hardened samples were reacted with tris-buffer solution, hydroxyapatite was obtained only for the sample with CaNH4PO4.H2O. While the substitution of MgO for CaO decreased the formation of CaNH4PO4.H2O crystal. MgNH4PO4.H2O crystla was formed in high MgO containing glass, which did not react with tris-buffer solution.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.617-622
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• 2011

Ozone-based advanced oxidation was applied for the treatment of anaerobic digestion effluent of livestock wastewater. Initial COD and color value were 930 mg/L and 0.04, respectively, and the 1/10-diluted wastewater was used for the study. The treatment characteristics were compared between the conventionally generated ozone ($105{\mu}m$) and microbubbled ozone ($13{\mu}m$). The use of microbubbled ozone improved the removal of chemical oxygen demand (COD) and color by 85% and 26%, respectively, compared with the conventionally bubbled ozone. The application of microbubbled $O_3/UV$, $O_3/H_2O_2$, $O_3/UV/H_2O_2$ combinations resulted in 5~10% higher color removal than ozone alone, which implies that the contribution of UV or $H_2O_2$ is not significant in color removal. On the other hand, COD removal could be increased two folds compared with ozone alone through $O_3/UV/H_2O_2$ combination. The contribution of $H_2O_2$ was bigger than UV for COD removal with microbubbled ozone. Due to the enhancement of dissolved ozone and radical activity, the microbubbling enabled us to additional COD removal even after stopping ozone supply in the presence of UV or $H_2O_2$.

• Bulletin of the Korean Chemical Society
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• v.27 no.11
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• pp.1785-1790
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• 2006

A novel kinetic method for determination of $HO_2{^{\cdot}}/O_2{^{{\cdot}-}}$ in ozone decomposition in water is described. In this study, potential interferences of $O_3$ and the hydroxyl radicals, $^{\cdot}OH_{(O3)}$, are suppressed by $HSO_3{^-}/SO_3{^{2-}}$. $HO_2{^{\cdot}}/O_2{^{{\cdot}-}}$ formed in ozone decomposition reduces $Fe^{3+}$-EDTA into $Fe^{2+}$-EDTA and subsequently the well-known Fenton-like (FL) reaction of $H_2O_2$ and $Fe^{2+}$-EDTA produces the hydroxyl radicals, $^{\cdot}OH_{(FL)}$. Benzoic acid (BA) scavenges $^{\cdot}OH_{(FL)}$ to produce OHBA, which are analyzed by fluorescence detection (${\lambda}_{ex}=320nm$ and ${\lambda}_{ex}=400nm$). The concentration of $HO_2{^{\cdot}}/O_2{^{{\cdot}-}}$ in ozone decomposition has been determined by the novel kinetic method using the experimentally determined half-life ($t_{1/2}$). The steady-state concentration of $HO_2{^{\cdot}}/O_2{^{{\cdot}-}}$ is proportional to the $O_3$ concentration at a given pH. However, the steady-state concentration of $HO_2{^{\cdot}}/O_2{^{{\cdot}-}}$ in ozone decomposition is inversely proportional to pH values. This pH dependence is due to significant loss of $O_2{^{{\cdot}-}}$ by $O_3$ at higher pH conditions. The steady-state concentrations of $HO_2{^{\cdot}}/O_2{^{{\cdot}-}}$ are in the range of $2.49({\pm}0.10){\times}10^{-9}M(pH=4.17){\sim}3.01({\pm}0.07){\times}10^{-10}M(pH=7.59)$ at $[O_3]_o=60{\mu}M$.

• Nuclear Engineering and Technology
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• v.33 no.4
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• pp.386-396
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• 2001

Mixtures Of AUC-UO$_2$and Gd$_2$O$_3$ Powders doped With Cr$_2$O$_3$ or Cr$_2$O$_3$-SiO$_2$ were Pressed and sintered at 1730 t in hydrogen gas witk various water-vapor contents. The density of UO$_2$- 6wt% Gd$_2$O$_3$ pellets can be increased from 91% TD to 94.5% TD in 1 vol% $H_2O$-H$_2$ gases by the addition of 0.02wt% Cr$_2$O$_3$-(0.01~0.04) wt% SiO$_2$. The magnitude of density increase is much larger in (1~3 vol%) $H_2O$-H$_2$ gases than in 0.05 vol% $H_2O$-H$_2$ gas. The densification of U0$_2$- Gd$_2$O$_3$ compact is significantly delayed in the temperature range between 1300 and 1500 t , but that of compacts with Cr$_2$O$_3$-SiO$_2$ is not. The role of Cr$_2$O$_3$ and SiO$_2$ in densification is discussed.

• Journal of Industrial Technology
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• v.29 no.A
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• pp.83-88
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• 2009

The removal efficiency of organic compounds and the toxicity evaluation of microorganism have been studied in dye wastewater treatment using $UV/TiO_2$ and $UV/H_2O_2$ photooxidation system. Sample waters tested in this work were raw dye wastewater and dye wastewater treated in $UV/TiO_2$ and $UV/H_2O_2$ photooxidation system respectively. Total organic carbon(TOC) removal rate was 50% in $UV/TiO_2$ process and 80% in $UV/H_2O_2$ process. It has been investigated with colony counting agar method and paper disk method whether the type of treatment process has affected the microorganism growth. In the raw wastewater, more than four types of microorganisms have survived. But, little of microorganisms were alive at TOC removal rate of 50% in $UV/TiO_2$ system. In contrast to that, two types of microorganisms were found at TOC removal rate of 80% in $UV/H_2O_2$ system.

• Biomedical Science Letters
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• v.14 no.3
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• pp.193-198
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• 2008

In order to evaluate on the effect of kaempferol on the cytotoxicity of oxygen tree radicals, XTT assay was performed to determine the cell viability after skin fibroblasts derived from human (Detroit 51) that were treated with various concentrations of hydrogen peroxide $(H_2O_2)$. And also, the effect of kaempferol on the cytotoxicity induced by H202 that was examined by cell viability, lactate dehydrogenase (LDH) activity and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity in these cultures. $H_2O_2$ decreased cell viability in dose-dependent manner in these cultures and the $XTT_{90}\;and\;XTT_{50}$ values were determined at concentration of $35{\mu}M\;and\;90{\mu}M$ of $H_2O_2$ after skin fibroblasts derived from human were treated with $15{\sim}90{\mu}M$ of $H_2O_2$ for 6 hours, respectively. $H_2O_2$ was highly toxic on cultured skin fibroblasts derived from human by toxic criteria of Brenfreund and Puerner (1984). In the protective effect of kaempferol on $H_2O_2$-induced cytotoxicity, kaempferol increased DPPH radical scavenging activity and significantly decreased LDH activity. From these results, it is suggested that oxygen tree radical, $H_2O_2$, was highly toxic on cultured skin fibroblasts derived from human, and also kaempferol of flavonoid showed the protection on $H_2O_2$-induced cytotoxicity.

• Journal of Korean Society on Water Environment
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• v.28 no.3
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• pp.401-408
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• 2012

High-voltage dielectric discharges are an emerging technique in environmental pollutant degradation, which that are characterized by the production of hydroxyl radicals as the primary degradation species. The initiation and propagation of the electrical discharges depends on several physical, chemical, and electrical parameters such as 1st and 2nd voltage of power, gas supply, conductivity and pH. These parameters also influence the physical and chemical characteristics of the discharges, including the production of reactive species such as OH, $H_2O_2$ and $O_3$. The experimental results showed that the optimum 1st voltage and air flow rate for RNO (N-Dimethyl-4-nitrosoaniline, indicator of the generation of OH radical) degradation were 160 V (2nd voltage of is 15 kV) and 4 L/min, respectively. As the increased of the 2nd voltage (4 kV to 15 kV), RNO degradation, $H_2O_2$ and $O_3$ generation were increased. The conductivity of the solution was not influencing the RNO degradation and $H_2O_2$ and $O_3$ generation. The effects pH was not high on RNO degradation. However, the lower pH and the conductivity, the higher $H_2O_2$ and $O_3$ generation were observed.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.12
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• pp.1147-1153
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• 2010

To evaluate the solar photocatalytic degradation efficiency of chloroform in a real solar-light driven compound parabolic concentrators (CPCs) system, $TiO_2$ was irradiated with a metalhalide lamp (1000 W), which has a similar wavelength to sunlight. The results were applied to a pilot scale reactor system by converting the data to a standardized illumination time. In addition, the effects of initial pH and the $TiO_2$ dose on the photocatalytic degradation of chloroform were investigated. The results were compared with the specific surface area (S.S.A) and particle size of $TiO_2$, which changed according to the pH, to determine the relationship between the S.S.A, particle size and the photocatalytic degradation of chloroform. The experiment was carried out at pH 4~7 using 0.1, 0.2, 0.4 g/L of $TiO_2$. The particle size and specific surface area of $TiO_2$ were measured. There was no significant difference between the variables. However, pH affects the particle size distribution and specific surface area of $TiO_2$. Inaddition, the activation of a photocatalyst did not show a linear relationship with the specific surface area of $TiO_2$ in the photocatalytic degradation of chloroform.

• Bulletin of the Korean Chemical Society
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• v.32 no.6
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• pp.1912-1920
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• 2011

The $SnO_2$ with a particle size of about 300 nm instead of Ni is used in this study to overcome rapid catalytic deactivation by the formation of a $NiAl_2O_4$ spinal structure on the conventional Ni/${\gamma}$-$Al_2O_3$ catalyst and simultaneously impregnated the catalyst with potassium (K). The $SnO_2-K_2O$ impregnated Zeolite Y catalyst ($SnO_2-K_2O$/ZY) exhibited significantly higher ethanol reforming reactivity that that achieved with $SnO_2$ 100 and $SnO_2$ 30 wt %/ZY catalysts. The main products from ethanol steam reforming (ESR) over the $SnO_2$-$K_2O$/ZY catalyst were $H_2$, $CO_2$, and $CH_4$, with no evidence of any CO molecule formation. The $H_2$ production and ethanol conversion were maximized at 89% and 100%, respectively, over $SnO_2$ 30 wt %-$K_2O$ 3.0 wt %/ZY at 600 $^{\circ}C$ for 1 h at a $CH_3CH_2OH:H_2O$ ratio of 1:1 and a gas hourly space velocity (GHSV) of 12,700 $h^{-1}$. No catalytic deactivation occurred for up to 73 h. This result is attributable to the easier and weaker of reduction of Sn components and acidities over $SnO_2-K_2O$/ZY catalyst, respectively, than those of Ni/${\gamma}$-$Al_2O_3$ catalysts.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.3
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• pp.297-307
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• 2006

During January $2002{\sim}April\;2004$, hydrogen peroxide ($H_{2}O_{2}$) measurements were performed at the campus of Korea University, which is located in the northeastern part of Seoul. Gas phase hydroperoxide was collected in aqueous solution and separated by HPLC. Concentrations were determined by fluorescence using postcolumn enzyme derivatization. This measurement system was improved to be run automatically from sample collection at every 10 minutes through chemical analysis for data collection. Detection limits of $H_{2}O_{2}$ is $10{\sim}17\;pptv$, and the overall uncertainty of the measurements is better than 8%. Two-year measurements of $H_{2}O_{2}$ show typical seasonal variations. Concentrations of $H_{2}O_{2}$ were higher during $June{\sim}October$ and lower during $January{\sim}February$. Maximum concentration of 1-hour averaged $H_{2}O_{2}$ was 6.5 ppbv, which was observed in August and September. In general $H_{2}O_{2}$ concentrations were well correlated with $O_{3}$ concentrations and largely affected by meteorological factors such as temperature and wind direction.