• Journal of the Korean Chemical Society
• /
• v.19 no.4
• /
• pp.225-232
• /
• 1975

The elution behaviour of molybdate and tungstate through anion exchange column has been studied at the various pH. A discussion is made to evaluate the equilibrium constants of the polymerization of these acids comparing with the behaviour of chromate ion and dichromate ion. The eqailibrium constants found at $20^{\circ}$ are $K = 4{\times}10^{53} for 7MoO_4^{2-} + 8H^+ {\longleftrightarrow} Mo7O_{24}^{6- }+ 4H_2O$$ K = 3{\times}10^{54} for 6WO_4^{2-} + 7H^+ {\longleftrightarrow} HW6O_{21}^{5-} + 7H_2O$ referring to this results the conditions of separation of tungstate and molybdate are obtained. iThe quantitative separations of carbonate, molybdate and tungstate from the pregnant solution have been established by anion exchange chromatography, using the $22 cm{\times}44.27 cm^2$ column of Rexyn 201. The optimum eluents for the quantitative separation of those ions are as follows; 0.2M solution of sodium chloride at pH 8 for carbonate, the mixture of 0.5 M ammonium chloride and 0.05 M sodium sulfate at pH 5 for molybdate and 0.5 M solution of ammonium chloride at pH 10 for tungstate. Tungstate is directly recovered from the pregnant solution as a form of ammonium paratungstate, by eluting with ammonium chloride solution.

• Applied Chemistry for Engineering
• /
• v.28 no.6
• /
• pp.619-625
• /
• 2017

In this study, the formation of hydroxyl radical and decomposition characteristics of bisphenol A (BPA) was investigated by quantifying hydrogen peroxide formed as a reaction by-product during the formation stage of hydroperoxyl radical. The direct oxidation reaction by ozone only decomposed BPA just like the Criegee mechanism under the condition where radical chain reactions did not occur. Non-selective oxidation reactions occurred under the conditions of pH 6.5 and 9.5 where radical chain reactions do occur, confirming indirectly the formation of hydroxyl radical. The decomposition efficiency of BPA by the added catalysts appeared in the order of $O_3$/PAC ${\geq}$ $O_3/H_2O_2$ > $O_3$/high pH > $O_3$ alone. 0.03~0.08 mM of hydrogen peroxide were continuously measured during the oxidation reactions of ozone/catalyst processes. In the case of $O_3$/high pH process, BPA was completely decomposed in 50 min of the oxidation reaction, but reaction intermediates formed by oxidation reaction were not oxidized sufficiently with 29% of the removal ratio for total organic carbon (TOC, selective oxidation reaction). In the case of $O_3/H_2O_2$ and $O_3$/PAC processes, BPA was completely decomposed in 40 min of the oxidation reaction, and reaction intermediates formed by the oxidation reaction were oxidized with 57% and 66% of removal ratios for TOC, respectively (non-selective oxidation reactions).

• Journal of Sensor Science and Technology
• /
• v.21 no.6
• /
• pp.451-455
• /
• 2012

Dense Cr-precursor nano-hexaprisms were prepared by heating the Cr-nitrate aqueous solution containing Hexamethylenetetramine and polyvinylpyrrolidone, which were converted into porous $Cr_2O_3$ nano-hexaprisms containing nanoparticles by heat treatment of Cr-precursors at $600^{\circ}C$ for 2 h in air atmosphere. At the sensor temperature of $300^{\circ}C$, porous $Cr_2O_3$ nano-hexaprism showed the high response ($R_g/R_a$, $R_g$: resistance in gas, $R_a$: resistance in air) to 100 ppm $C_2H_5OH$ ($R_g/R_a=69.8$) with negligible cross-responses to 100 ppm CO and 5 ppm $C_6H_6$. The sensitive and selective detection of $C_2H_5OH$ in porous $Cr_2O_3$ nano-hexaprism were discussed in relation to the morphology of nanostructures.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.32 no.8
• /
• pp.1390-1393
• /
• 2003

Measuring in vivo rate of bone collagen synthesis has so far been technically difficult and often subject to quite large errors. In the present study, bone collagen synthesis rate was measured using a precursor-product method, based on the exchange of $^2$$H_2O$ into amino acids. Mass isotopomer abundance in hydroxyproline from bone collagen was analyzed by gas chromatography/mass spectrometry. The $^2$$H_2O$ labeling protocol consisted of an initial intraperitoneal injection of 99.9% $^2$$H_2O$, to achieve approximately 2.5% body water enrichment followed by administration of 4% $^2$$H_2O$ in drinking water for 9 weeks. Body $^2$$H_2O$ enrichments were stable at 2.7 ∼ 3.0% over labeling Period. In growing rats, the fractional synthesis rate ( $k_{s}$) of bone collagen was 0.066 $\pm$ 0.049 w $k^{-1}$ . The unique features of stable $^2$$H_2O$ pools and label incorporation allowed the precursor-product approach to be used for measuring bone collagen synthesis rate..

• The Bulletin of The Korean Astronomical Society
• /
• v.38 no.2
• /
• pp.77.2-77.2
• /
• 2013

We present the interim results of simultaneous time monitoring observations of $^{28}SiO$ v = 1, 2, J = 1-0, $^{29}SiO$ v = 0, J = 1-0 and $H_2O$ $6_{16}-5_{23}$ maser lines toward 10 known water fountain sources at a post-AGB stage. The observations have been carried out from 2009 June to 2013 September using the 21m single dish radio telescopes of the Korean VLBI Network. From six sources, we detected well separated red- and blue-shifted $H_2O$ maser features with large velocity ranges more than 100 km $s^{-1}$. From four sources, we detected red- and/or blue-shifted $H_2O$ maser features depended on observational epochs. However, we could not detected SiO maser emission from any sources and any epochs. For a representative water fountain source W43A, we obtained $H_2O$ maser spectra at 17 epochs which show a clear bipolar and discontinuous mass ejections. They also showed a periodic change between red-shifted and blue-shifted peaks. However, we need a more regular and short-time interval monitoring observations in order to fix the period and peak intensity variation interval.

• The Journal of Internal Korean Medicine
• /
• v.22 no.3
• /
• pp.383-391
• /
• 2001

목적 : 본 연구는 목향순기탕(木香順氣湯)이 인간의 장관상피세포 계열인 Caco-2 세포에서 항산화작용을 증진시키는 효과가 있는지 검증하기 위한 실험이다. 방법 : 배양된 인간장관 세포계열인 Caco-2 세포에서 세포의 사망은 trypan blue의 소실정도에 의해 평가했으며 $H_2O_2$는 표본산화제로 사용되었다. 결과 : $H_2O_2$에서 노출된 세포들은 용량에 비례하여 세포 사망하는 결과를 보였다. 목향순기탕(木香順氣湯)은 $H_2O_2$에 의해 유발된 세포사망을 방지하였고, 0.05-1%의 농도범위에 걸쳐서 효과가 극대화되었다. 목향순기탕(木香順氣湯)과 강력한 항산화제인 DPPD는 $H_2O_2$에 의해 억제된 SOD의 활성에는 영향을 주지는 못했다. 그러나 $H_2O_2$에 의해 유발된 catalase, glutathione peroxidase, hydroperoxide 탈취효소의 활성이 감소되는 것을 억제하였다. 또한 $H_2O_2$에 의해 유발된 glutathione의 감소는 목향순기탕(木香順氣湯)과 DPPD에 의해 억제되었다. 목향순기탕(木香順氣湯)은 $H_2O_2$에 의해 유발된 ATP의 소실을 회복시켰지만 DPPD는 ATP 소실을 회복시키지 못하였다. 결론 : 이러한 결과로 볼 때 Caco-2세포에서 목향순기탕이 세포사망을 억제하는 것은 다른 기전을 통하여 항산화작용을 하는 것으로 볼 수 있다. 따라서 본 연구는 목향순기탕(木香順氣湯)이 반응성산소기에 의해 유발된 인체 위장관질환의 치료에 사용할 수 있을 가능성을 제시하고 있다.

• Journal of Korean Society of Environmental Engineers
• /
• v.29 no.7
• /
• pp.826-832
• /
• 2007

Unpleasant tastes and odors in drinking water cause same problems for water utilities across Korea. Even though tastes and odors do not create health problems, they are main concerns for consumers who determine the safety of their drinking water. In this study, two different odor producing compounds(geosmin 2-MIB) in the Nakdong river water and rapid sand filtered rater were treated by advanced oxidation of $O_3/H_2O_2$ process. The experimental results showed that the removal efficiency of geosmin with the use of 5 mg/L of $O_3$ and $H_2O_2$ was higher than efficiency with the use of $O_3$ alone for both the raw water and the sand filtered water. And in general, the removal efficiency of geosmin was higher than 2-MIB in the sand filtered water. Under the range of $O_3$ concentration $0.5\sim2.0$ mg/L, the removal rate constants(k) of geosmin for the raw and sand filtered waters, and the one of 2-MIB in the sand filtered water were increased rapidly as doses of $O_3$, and $H_2O_2$, increased. The removal rate constants(k) do not increase any more when $H_2O_2/O_3$ ratio increases above the optimum ratio. The optimum ratio of $H_2O_2/O_3$, dose was $1.0\sim2.0$ for both geosmin and 2-MIB. The removal rate constant(k) becomes lower when OH radical consuming materials are present in raw water. The half-life of geosmin decreased rapidly as the $O_3$ and $H_2O_2$ doses increase in the sand filtered water. The half life decreased about 8.5 times with the use of 2 mg/L of $O_3$ and 10 mg/L of $H_2O_2$ than with the use of 2 mg/L of $O_3$ alone for the sand filtered water.

• Journal of Korean Society on Water Environment
• /
• v.20 no.3
• /
• pp.251-255
• /
• 2004

Laboratory experiments were performed to investigate oxidation system using ozone and hydrogen peroxide for treating water contaminated with phenol. We were able to greatly improve the oxidation efficiency of the aqueous phenol using hydrogen peroxide and ozone. Two methods were compared and analyzed in this study. In the consequence through the methods, we concluded that the $O_3/UV$ is superior to the hydrogen the results. The decomposition efficiency of aqueous phenol by $H_2O_2$. was exceeded at 83.3% in the concentration of phenol, 5, 15, 25 ppm, respectively. The rate of decomposition reaction by $H_2O_2$. was very slow. In the occasion of the fractional life, it was determined the value that $1.61{\times}10^{-5}(l/mol)^{1.172}sec^{-1}$, $3.75{\times}10^{-5}(l/mol)^{0.792}sec^{-1}$, $4.11{\times}10^{-5}(l/mol)^{1.782}sec^{-1}$. The rate of decomposition reaction of aqueous phenol by $O_3$ was fast compared to the $H_2O_2$. We concluded that the $O_3$ method is useful with the consideration of the reaction time 30 minutes. In the occasion of the fractional life, it was determined the value that $1.094{\times}10^{-4}(l/mol)^{0.933}sec^{-1}$, $2.1{\times}10^{-4}(l/mol)^{0.842}sec^{-1}$, $7.22{\times}10^{-4}(l/mol)^{1.332}sec^{-1}$.

• Journal of Power System Engineering
• /
• v.18 no.6
• /
• pp.133-139
• /
• 2014

In this research, the photocatalytic degradation of benzothiophene in $TiO_2$ aqueous suspension has been studied. $TiO_2$ photocatalysts are prepared by a sol-gel method. The dominant anatase-structure on $TiO_2$ particles is observed after calcining the $TiO_2$ gel at $500^{\circ}C$ for 1hr. Photocatalysts with various transition metals (Nd, Pd and Pt) loading are tested to evaluate the effect of transition metal impurities on photodegradation. The photocatalytic degradation in most cases follows first-order kinetics. The maximum photodegradation efficiency is obtained with $TiO_2$ dosage of 0.4g/L. The photodegradation efficiency with Pt-$TiO_2$ is higher than pure $TiO_2$ powder. The optimal content value of Pt is 0.5wt.%. Also we investigate the applicability of $H_2O_2$ to increase the efficiency of the $TiO_2$ photocatalytic degradation of benzothiophene. The optimal concentration of $H_2O_2$ is 0.05. The effect of pH is investigated; we obtain the maximum photodegradation efficiency at pH 9. Hydroxy-benzothiophenes and dihydroxy-benzothiophenes are identified as reaction intermediates. It is proposed that benzothiophene is oxidized by OH radical to sequentially form hydroxyl-benzothiophenes, dihydroxybenzothiophenes, and benzothiophenedione.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.26 no.11
• /
• pp.1686-1690
• /
• 1989

Using the anisotropic etching characteristics of N2H4-H2O solutions, Si diaphragm was fabricated for the integrated sensors. The optimal composition and temperature of the etching solution in (100) Si etching process was established to be 50mol% N2H4 in H2O at 105\ulcorner\ulcorner for both higher etch rate (=2.6\ulcorner/min) and better surface quality of etched (100) planes. Based on the above optimal etching condition, the electrochemical etch-stop technique was employed to form n-type Si diaphragm having a thickness of 20\ulcorner and the thickness of diapragm could exactly be controlled to 20\ulcorner\ulcorner.