• Journal of Environmental Science International
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• v.10 no.1
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• pp.13-19
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• 2001

An on-line digestion system based on the flow injection analysis technique was presented for the determination of total phosphorus. The system converts condensed and organic phosphoruses into orthophosphate that can be analyzed spectrophotometically. The reaction between orthophosphate and ammonium molybdate in a strong acid medium forms the yellow complex of phosphomolybdate which is next reduced to a molybdic blue complex by stannous chloride. The quantitation of orthophosphate is based on the absorbance of the molybdic blue. To determine total phosphorus, the digestion system was installed between the sample injector and the reaction coil with the added lines of digestion solution(potassium persulfate+sulfuric acid) and the $H_2O$ carrier. The system has shown that the digestion efficiencies were greater than 95% for the typical condensed and organic phosphoruses. When tripolyphosphate standards were used, the calibration data showed that the linear dynamic range extended to a concentration of 1.5ppm with the detection limit of 25ppb total phosphorus. The typical relative standard deviation was less than 2%. The proposed system was successfully applied to lake water, wastewater, and streamwater. The analytical variables such as digestion efficiency, analysis time, and reproducibility were evaluated and compared with the manual digestion method.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.4
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• pp.627-632
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• 2013

High levels of an extracellular phytase were isolated from kimchi and found to be produced from a bacterial strain of Lactobacillus sakei (designated as L. sakei Wikim001). Phytase activity was measured from liberated inorganic phosphate obtained by a modification of the ammonium molybdate method using brown rice. Phytase activity was also detected in the culture broth supernatant at the stationary phase. The highest levels of phytase activity from L. sakei Wikim001 were detected at pH 5.0~6.5 and $30{\sim}40^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• v.24 no.12
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• pp.1785-1792
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• 2003

Zirconia modified with $MoO_3$ was prepared by impregnation of powdered $Zr(OH)_4$ with ammonium heptamolybdate aqueous solution followed by calcining in air at high temperature. Spectroscopic studies on prepared catalysts were performed by using FTIR, Raman, XRD, and DSC and by measuring surface area. Upon the addition of molybdenum oxide to zirconia up to 15 wt%, the specific surface area increased in proportion to the molybdate oxide content, while acidity measured by irreversible chemisorption of ammonia exhibited a maximum value at 3 wt% of $MoO_3$. Since the $ZrO_2$ stabilizes the molybdenum oxide species, for the samples equal to or less than 30 wt%, molybdenum oxide was well dispersed on the surface of zirconia and no phase of crystalline $MoO_3$ was observed at any calcination temperature above $400^{\circ}C$. The catalytic activities for cumene dealkylation were roughly correlated with the acidity of catalysts measured by ammonia chemisorption method, while the catalytic activities for 2-propanol dehydration were not correlated with the acidity because weak acid sites are necessary for the reaction.

• Journal of Sensor Science and Technology
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• v.28 no.5
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• pp.271-276
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• 2019

Pure and 0.5, 1, 2, 5, and 10 at% of Mo-doped $Co_3O_4$ yolk-shell spheres were synthesized by ultrasonic spray pyrolysis of droplets containing Co nitrate, ammonium molybdate, and sucrose and their gas sensing characteristics to 5 ppm trimethylamine (TMA), ethanol, p-xylene, toluene, ammonia, carbon monoxide, and benzene were measured at $225-325^{\circ}C$. The sensor using pure $Co_3O_4$ yolk-shell spheres showed the highest response to p-xylene and very low response to TMA at $250^{\circ}C$, while the doping of Mo into $Co_3O_4$ tended to increase the overall responses of gas sensors. In particular, the sensor using 5 at% Mo-doped $Co_3O_4$ yolk-shell spheres exhibited the high response to TMA with low cross-responses to other interfering gases. The high response and selectivity of Mo-doped $Co_3O_4$ yolk-shell spheres to TMA are attributed to the electronic sensitization by higher valent Mo doping and acid-base interaction between TMA and Mo components.

• Korean Journal of Environmental Biology
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• v.25 no.4
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• pp.342-348
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• 2007

In a previous study, a new antibacterial activity was found from Paenibacillus polymyxa DY1 isolated from Korean soil, which showed a good growth inhibition against various multidrug resistant enteric bacteria. Thus the effect of nutritional factors and physicochemical conditions on the growth of P. polymyxa DY1 cells and the production of antibacterial activity were evaluated in this study. For the growth of P. polymyxa DY1 cells the optimum condition reaches by incubating at $35^{\circ}C$ for 48 hours by shaking at 180 rpm in the basal medium containing 0.6% dextrose, 1.4% ammonium phosphate dibasic, 0.9% peptone, 2.4% glutamine, and 2 mM sodium molybdate with initial pH 8.0. A maximum level of antibacterial activity was obtained when P. polymyxa DY1 was incubated at $35^{\circ}C$ for 48 hours by shaking at 180 rpm in the basal medium with initial pH 8.0 containing 1% dextrose, 1.5% ammonium sulfate, 1.1% casamino acid, 1.9% aspartic acid, and 2 mM ferrous sulfate.

• Applied Chemistry for Engineering
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• v.8 no.5
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• pp.749-755
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• 1997

Molybdenum phosphate(P/Mo = 0.6) has been synthesized with ammonium molybdate and phosphoric acid under aqueous solution. The kinetics of the ammoxidation of methylpyrazine over molybdenum phosphate catalyst was investigated with the variation of reaction temperature and partial pressure of methylpyrazine, oxygen and ammonia, respectively at atmospheric pressure. The catalytic activity was constant for 300hrs operation under our experimental conditions. Under the steady-state condition, the rate equation of methylpyrazine was shown as $-r=kP_{MP}P_{NH3}{^0}P_{O2}{^{\gamma}}({\gamma}=2.2;1.3{\leq}P_{O2}(kPa){\leq}4)$. The apparent activation energy was 29.6kcal/mol below 623K. The main product obtained in the ammoxidation of methylpyrazine is cyanopyrazine whose selectively was kept always over 90% regardless of conversion.

• Applied Chemistry for Engineering
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• v.27 no.3
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• pp.307-312
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• 2016

Lead molybdate ($PbMoO_4$) was successfully synthesized using a facile surfactant-assisted hydrothermal process and characterized by XRD, Raman, TEM, PL, BET and DRS. We also investigated the photocatalytic activity of these materials for the decomposition of Rhodamine B under UV-light irradiation. From XRD and Raman results, well-crystallized $PbMoO_4$ crystals were successfully synthesized with the particle size of 52-69 nm. $PbMoO_4$ catalysts prepared in the presence of cetyltrimethyl ammonium bromide (CTAB) enhanced the photocatalytic activity compared to that of using P-25 and pure $PbMoO_4$ catalysts. The maximum photocatalytic activity of $PbMoO_4$ catalyst were observed when preparing it in pH 9 solution. The The PL peak at about 540 nm were observed for all catalysts and the excitonic PL signal increased proportionally with respect to the photocatalytic activity of Rhodamine B.

• Korean Journal of Plant Resources
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• v.19 no.6
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• pp.706-715
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• 2006

Nitrate reductase deficient (NR) mutant lines were selected indirectly by their resistance to 100mM chlorate in cell cultures of P. parviflora. A total of 585 chlorate resistant lines were confirmed by a second passage on a high concentration of chlorate. Frequency of spontaneous mutation was $9.7{\times}10^{-7}$ in 3 month old suspension-cultured cells, and in non-selective media containing amino acids as sole nitrogen source. The frequency of mutation could be increased up to 11-fold by culture for 12 months. Out of 40 randomly selected calli, 22 were fully deficient in NR. The rest of the clones contained a decreased level of NR activity. Further characterization was carried out in 13 mutant lines which were fully deficient in NR and in 5 mutant lines containing residual (0-7.0%) NR activity, as compared to wild-type cells cultured on the same medium. The $NR^-$ mutants were tentatively classified as defective in the NR apoenzyme (nia-type; 11 mutant lines including the 5 with residual NR activity) or in the molybdenum cofactor (cnx-type; 7 mutant lines) by the XDH activity. The cnx-type could be further classified into two groups. In one group (5 mutant lines) of these, the NR activity could be partially restored by nonphysiologically high (1.0mM) molybdate in the culture medium. Both types of $NR^-$ mutants were unable to grow on minimal medium containing nitrate as sole nitrogen source, but grew well on amino acids. They also proved to be extremely sensitive to the standard medium ($MSP_1$) containing nitrate and ammonium. Shoot regeneration was obtained only in the $NR^-$ mutants, which contained residual NR activity, but they so far have failed to grow into plants.

• Resources Recycling
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• v.7 no.4
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• pp.64-75
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• 1998

The purpose of this study is to produce high putity composite powder composed of Fe-oxide, Mn-oxide and Mn-ferrite having superior homogencity in composition and particle size distribution by co-roasting process. Binary component metal (Fe, Mn) chloride solutions were produced by dissolving mill scale and ferro-mangancse alloy in hydrochloric acid. These chloride solutions contained the impurities such as SiO$_{2}$, P, Al, Ca and Na, which were originated from the Fe/Mn source materials. The neutralization and polymeric coagulant method were adoped to refine the hydrochloric liquor. When pH is far below the isoelectric point (pH 2-3), the SiO$_{2}$ was the most effectively reduced element, while other impurities remained unchanged. By increasing pH above 3, most of the impurities could be reduced effectively due to the coprecipitation reaction. The polymeric coagulants such as poly vinyl alcohol, resin amine and ammonium molybdate were found to have no effect on the spray roaster designed by the authors. The produced oxide powders were confirmed to be mixtures of Fe-oxide, Mn-oxide and mn-ferrite. the powders were homogeneously mixed and the particle size increased sleeply with increasing co-roasting temperature.

• Journal of the Korean Chemical Society
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• v.8 no.3
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• pp.113-120
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• 1964

The critical examination of the spectrophotometric method for determining microgram quantities of phosphate by the n-butyl acetate extraction as molybdophosphoric acid and subsequent development of the molybdenum blue has been made. In this procedure from 2 to 8 ${\mu}g$. of phosphate-phosphorus can be determined under optimum conditions. The final concentration of ammonium molybdate and the final acidity of perchloric acid for the formation of heteropoly acid are suitable to be ranges of 0.5 to 1.1% and 0. 5 to 1. 1 N respectively, and subsequently extracted with 10 ml. of n-butyl acetate. The extract is developed to molybdenum blue with 5.0 ml. of 1. 3% stannous chloride in 1N hydrochloric acid. The color is stable for at least one hour in the use of perchloric acid for the condensation. In order to determination of submicrogram amounts of phosphate, the sensitivity of the molybdenum blue method is hardly sufficient, a sensitive and stable molybdenum(V)-thiocyanate complex method has been investigated. By the procedure less than 1.2 ${\mu}g$. of phosphate-phosphorus can be determined with an accuracy of less than 5% the relative error. The molybdenum(Ⅵ) extracted by the above procedure is reduced to molybdenum(V) in the extract directly with a solution of 4 to 10% of stannous chloride, 0.5 to 1.5 mM of copper, and 0.1 to 0.9 N of perchloric acid as final concentration in 4.3 to 6.3 N of hydrochloric acid or 9.0 to 13.0 N of sulfuric acid by heating for one minute in boiling water, after cooling, the molybdenum(V)-thiocyanate complex color is developed by adding 6.0 M ammonium thiocyanate solution making the final concentration to be in a range of 0.4 to 0.9 M. This procedure the very sensitive, reliable, and stable can be applied to determining submicrogram amounts of phosphate in natural waters with a precision of 1.6 ${\times}\;10^{-2}$ the standard deviation as absorbance.