• Bulletin of the Korean Chemical Society
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• v.30 no.10
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• pp.2485-2488
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• 2009

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

• Korean Journal of Materials Research
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• v.25 no.10
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• pp.547-551
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• 2015

The present study prepared molybdenum trioxide ($MoO_3$), the most important intermediate of molybdenum metal, by using a fluidized bed reactor for the thermal decomposition of ammonium molybdate (AM) in the presence of an air flow. During the process of fluidizing the sample inside the reactor, the reaction time and temperature were optimized with a close analysis of the X-ray diffraction (XRD) data and with thermogravimetric analysis (TGA). In particular, the temperature level, at which the AM decomposition is completed, is very important as a primary operating parameter. The analysis of the XRD and TGA data showed that the AM decomposition is almost completed at ${\sim}350^{\circ}C$ with a reaction time of 30 min. A shorter reaction time of 10 min. required a higher reaction temperature of ${\sim}500^{\circ}C$ with the same air flow rate to complete the AM decomposition. A sharp rise in the decomposition efficiency at a temperature ranging between 320 and $350^{\circ}C$ indicated a threshold for the AM decomposition. The operating conditions determined in this study can be used for future scale-ups of the process.

• Korean Journal of Soil Science and Fertilizer
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• v.31 no.2
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• pp.114-119
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• 1998

Intensity and stability of the blue color of phospho-molybdate complex in P analysis are known to be influenced by the matrix, reducing regent and acidity of the extractants. Objective of this research was to compare the efficiency of the color-developing reagents for P concentrations in distilled water and extracts of Lancaster, Mehlich II, and Mehlich III methods. Efficiencies on which to base this study were evaluated by the optimum ranges of P, reproducibility of calibration curve and stability of the developed color. Color-developing reagents employed were ammonium molybdate-1,2,4- aminonaphtholsulfonic acid (ANS), ammonium molybdate-ascorbic acid-bismuth subcarbonate (AB), and ammonium molybdate-ascorbic acid-antimony potassium tartarate (AA). The ANS revealed the lowest sensitivity but the widest ranges for P concentrations in color development. On the other hand, the AA bore the narrowest color-developing ranges and its sensitivity was similar to AB. However, at P concentrations lower than $0.5mg\;L^{-1}$, AA was more sensitive than AB. Based on the data on the ranges of calibration curve, stability of color and reproducibility of analytical data. AA reagent was considered to be suitable for the determination of P in distilled water and AB reagent was practically recommendable for soil P analysis in extracts by Lancaster, Mehlich II, and Mehlich III procedures.

• Resources Recycling
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• v.12 no.2
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• pp.36-44
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• 2003

The present work relates to the recovery of dissolved Mo from spent mandrel dissolving acid solution by injecting ammonia gas. In order to optimize the process parameters for high yield and high purity of recovered Mo products, a bench scale and a pilot scale experiments were carried out. As a result, more than 99.5% of Mo in spent acid was recovered in the form of ammonium molybdate(4MoO$_3$.$2NH_3$.$H_2$O). The purity of Mo products recovered was higher than 99.5%. In addition, the mother liquor, residual solution after precipitation and filtration of ammonium molybdate solid particles, could be utilized as fertilizers.

• Bulletin of the Korean Chemical Society
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• v.24 no.3
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• pp.311-317
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• 2003

Vanadium oxides supported on zirconia and modified with MoO₃were prepared by adding Zr(OH)₄powder into a mixed aqueous solution of ammonium metavanadate and ammonium molybdate followed by drying and calcining at high temperatures. The characterization of prepared catalysts was performed using FTIR, Raman spectroscopy and solid-state $^{51}V$ NMR. In the case of a calcination temperature of 773 K, for samples containing low loading of $V_2O_5$, below 15 wt %, vanadium oxide was in a highly dispersed state, while for samples containing high loading of $V_2O_5$, equal to or above 15 wt %, vanadium oxide was well crystallized because the $V_2O_5$ loading exceeded the formation of a monolayer on the surface of $ZrO_2$. The $ZrV_2O_7$ compound was formed through the reaction of $V_2O_5\;and\;ZrO_2$ at 873 K and the compound decomposed into $V_2O_5\;and\;ZrO_2$ at 1073 K, which were confirmed by FTIR spectroscopy and solid-state $^{51}V$ NMR. IR spectroscopic studies of ammonia adsorbed on $V_2O_5-MoO_3/ZrO_2$ showed the presence of both Lewis and Bronsted acids.

• Journal of the Korean Society of Food Science and Nutrition
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• v.23 no.3
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• pp.490-495
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• 1994

Acid phosphatase (EC3.1.3.2) from carrots was partially purified by ammonium sulfate fractionation (30%-80%), Sephacryl S-200 gel filtration, cm-Sepharose CL-6B and DEAE -Sephacel ion exchange chromatography. The optimum ph and temperature of acid phosphatase from carrots were pH 5.5 and 55$^{\circ}C$, respectively. The enzyme was most stable at ph 6.0 and relatively unstable below pH 4.0 . The activation energy of the enayme was determined to be 10.6kcal/mole. The enzyme utilized p-nitrophenyl phosphate as a substrate among tested possible substrates, whereas it hydrolyzed 5' -IMP and 5'-GMP poorly. The Michaelis -Menten constant(Km) of the enzyme with p-nitrophenyl phosphate as a substrate was identified as 0.55mM. Amongtested metal ions and inhibitors, Al+++ Zn++, Cu++ , fluoride, metavanadate and molybdate ions inhibited the enzyme activity drastically.

• Journal of Microbiology and Biotechnology
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• v.19 no.9
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• pp.918-921
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• 2009

In the present study, we examined the inhibitory effects of protein tyrosine phosphatase (PTPase) inhibitors, including sodium orthovanadate (SOV), ammonium molybdate (AM), and iodoacetamide (IA), on cell growth, accumulation of astaxanthin, and PTPase activity in the photosynthetic algae Haematococcus lacustris. PTPase activity was assayed spectrophotometrically and was found to be inhibited 60% to 90% after treatment with the inhibitors. SOY markedly abolished PTPase activity, significantly activating the accumulation of astaxanthin. These data suggest that the accumulation of astaxanthin in H. lacustris results from the concerted actions of several PTPases.

• Journal of the Korean Chemical Society
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• v.16 no.2
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• pp.84-92
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• 1972

A mechanism for the ring formation of nickel phthalocyanine (Ni-Pc) has been proposed based on chemical kinetics. The effect of the catalyst on the rate was examined, and ammonium molybdate has been found to be the most effective. The reaction order of the ring formation was determined to be of the 1st order over all, with only the concentration of urea affecting the rate of the ring formation. All the results including thermodynamic parameters support a conclusion that the rate-determining step seems to be the enolization of the urea-catalyst transition complex, followed by fast decomposition of the tautomeric enolized urea into ammonia and isocyanic acid. These intermediates then reacted with the phthalic anhydride to form imino and diimino-phthalimide, which condense to form nickel phthalocyanine in the presence of the nickel cation.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1687-1691
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• 2014

This study reports on the synthesis of carbon nanofibers via chemical vapor deposition using Co and Cu as catalysts. In order to investigate the suitability of their catalytic activity for the growth of nanofibers, we prepared catalysts for the synthesis of carbon nanofibers with Cobalt nitrate and Copper nitrate, and found the optimum concentration of each respective catalyst. Then we made them react with Aluminum nitrate and Ammonium Molybdate to form precipitates. The precipitates were dried at a temperature of $110^{\circ}C$ in order to be prepared into catalyst powder. The catalyst was sparsely and thinly spread on a quartz tube boat to grow carbon nanofibers via thermal chemical vapor deposition. The characteristics of the synthesized carbon nanofibers were analyzed through SEM, EDS, XRD, Raman, XPS, and TG/DTA, and the specific surface area was measured via BET. Consequently, the characteristics of the synthesized carbon nanofibers were greatly influenced by the concentration ratio of metal catalysts. In particular, uniform carbon nanofibers of 27 nm in diameter grew when the concentration ratio of Co and Cu was 6:4 at $700^{\circ}C$ of calcination temperature; carbon nanofibers synthesized under such conditions showed the best crystallizability, compared to carbon nanofibers synthesized with metal catalysts under different concentration ratios, and revealed 1.26 high amorphicity as well as $292m^2g^{-1}$ high specific surface area.