• Bulletin of the Korean Chemical Society
• /
• 제30권10호
• /
• pp.2485-2488
• /
• 2009

• 대한화학회지
• /
• 제19권4호
• /
• pp.225-232
• /
• 1975

용리액의 pH변화에 따른 몰리브덴산과 텅스텐산의 용리곡선과 이들 산의 분리조건을 얻었다. 이 용리곡선으로부터 이들 산의 중합반응의 평형상수를 크롬산과 중크롬산의 중합반응의 결과와 비교하여 계산했고 분리조건을 pregnant 용액 분리에 적용했다. 이때 얻은 이들산의 중합평형상수 값은 다음과 같다. $7MoO_4^{2-}+8H^+{\longleftrightarrow}Mo7O_{24}^{6-}+4H_2O K=4{\times}10^{53},$$6WO_4^{2-}+7H^+{\longleftrightarrow}HW_6O_{21}^{5-}+3H_2O K=3{\times}10^{54}.$ 이온 교환크로마토그라피를 이용하여 프레그난트용액중의 탄산염을 분리하는 데는 pH8의 0.2M 염화나트륨 용액을 사용했고 몰리브덴을 분리하는데는 pH5의 0.05M $Na_2SO_4+0.5M NH_4Cl$ 혼합용액을, 텅스텐을 분리하는데는 pH 10의 0.5M 염화암모늄 용액을 단계적으로 사용하여 정량적으로 분리했다. 이때 텅스텐은 염화암모늄 용액을 용리액으로 사용했기 때문에 직접 APT(Ammonium para-tungstate)형태로 얻어졌다.

• 한국재료학회지
• /
• 제25권10호
• /
• pp.547-551
• /
• 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.

• 한국토양비료학회지
• /
• 제31권2호
• /
• pp.114-119
• /
• 1998

토양(土壤)의 인산분석(燐酸分析)의 정확도(正確度)를 향상(向上)시킬 수 있는 인산 발색방법을 찾고자 인산농도(燐酸濃度)가 다른 Lancaster, Mehlich II, Mehlich III 추출액(抽出液) 그리고 증류수중(蒸溜水中)의 인산을 Amino - Naphtol -Sulfonic acid(ANS), Ascorbic acid (AA)-Antimony potassium tartarate 그리고 Ascorbic acid-Bismuth subcarbonate(AB) 법(法)등 3개(個) 발색정양법(發色定量法)으로 발색 정치시간(靜置時間)을 달리하면서 Hitachi U-2000 분광분석기(分光分析器)로 분석(分析)한 결과(結果)는 다음과 같다. 인산 발색정치시간을 0.5시간으로 고정하여 분석된 표준액의 인산값과 여러수준의 시간을 두고 분석된 각 시료용액의 인산값간의 상관관계에서 ANS방법을 사용한 경우 발색을 위한 정치시간이 경과 할 수록 색도가 높아져 1차회귀계수가 커졌으나 Ascorbic acid를 사용한 AA와 AB법은 3시간의 발색에서도 흡광도의 안정성을 보였고, 분석치의 변이계수도 ANS법보다 낮았다. 인의 검량범위는 ANS법이 가장 넓으나 저농도에서는 분석의 정확도가 낮고 AA와 AB법은 저농도에서도 정확도가 높았으며 AB법은 AA법보다 넓은 범위의 인 농도 측정이 가능하였다. 따라서 3종의 인산발색법중 수용성 인 분석에는 AA법이 가장 좋았고 시약으로 추출되는 인 분석에는 AB법이 우수한 것으로 판단되었다.

• 자원리싸이클링
• /
• 제12권2호
• /
• pp.36-44
• /
• 2003

전구용 필라멘트 제조 공정에서 발생되는 Mo함유 폐산 내에 암모니아 가스를 취입하여 유가금속인 Mo를 암모늄테트라몰리브데이트($_3$.2NH$4MoO_3$.$H_2$O) 형태로 침전 회수하고, 여과 후 발생되는 중화 여액을 활용하기 위한 연구를 수행하였다. 암모니아 중화법을 이용한 Mo 회수공정에 있어 다양한 공정 변수들에 의한 제품의 회수율, 순도, 입도 등 특성을 평가하였으며, 그 결과로부터 Mo 염의 회수율 99.5% 이상, 순도 99.5% 이상을 확보하기 위한 최적 조업조건을 도출하였다. Bench 및 Pilot규모의 실험을 통하여 상업화 가능성을 확인하였으며, 폐산의 중화반응 후 발생된 여액은 엽면시비용 액상 복합비료의 원료로 사용 가능함을 확인하였다.

• Bulletin of the Korean Chemical Society
• /
• 제24권3호
• /
• pp.311-317
• /
• 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.

• 한국식품영양과학회지
• /
• 제23권3호
• /
• pp.490-495
• /
• 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
• /
• 제19권9호
• /
• pp.918-921
• /
• 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.

• 대한화학회지
• /
• 제16권2호
• /
• pp.84-92
• /
• 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
• /
• 제35권6호
• /
• pp.1687-1691
• /
• 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.