• Applied Biological Chemistry
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• v.19 no.3
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• pp.162-171
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• 1976

The determination of rate limiting step in the metabolic process is of great importance to understand the metabolic properties. In this paper the authors propose a modified enzymatic method instead of thermodynamic method. This method is based on the assumption that the over-all rate increment would be larger than by any other steps to which the individual enzyme are added respectively, provided that the enzyme participated in the rate limiting step is added to the reactions composed of n steps of metabolic process with which n kind of enymes are concerned. The present paper deals with analysis and discussion about some factors having influence on the proposed process, mainly about the metabolic process constituted with homogeneous steps. The results show that the determination of rate limiting step by a modified enzymatic method is feasible, provided that some restrictions are added in any type of mechanisms.

• Resources Recycling
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• v.11 no.4
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• pp.37-43
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• 2002

As the consumption of galvanized steels in cans and automobiles and the quantity of scraps increase, the recycling problems of EAF dust become a important problem. Valuable metals such as Fe, Zn, Pb are of continued interest to metallurgists. To recover the valuable metal and to remove the toxicity of EAF dust, high temperature smelting process is or researching as a pilot scale. The Reduction kinetics of Zn in EAF dust is so important in a view of the economic consideration of the process. In this study, the kinetics behavior of Zn in EAF dust were measured as a point of application in high temperature smelting process. The rate control step in ZnO and franklinite is revealed to be chemical reaction on the reaction surface.

• Resources Recycling
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• v.31 no.5
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• pp.59-66
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• 2022

To investigate the rate-determining step of nickel, cobalt and copper electrowinning, experiments were conducted by varying the electrolyte temperature and agitation speed using a rotating disc electrode. Analyzing the rate-determining step by calculating the activation energy in the electrowinning process, it was found that nickel electrowinning is controlled by a mixed mechanism (partly by chemical reaction and partly by mass transport), cobalt is controlled by chemical reaction, and copper is controlled by mass transfer. Electrowinning of nickel, cobalt and copper was performed by varying the electrolyte temperature and agitation speed, and the comparison of the current efficiencies was used the determine the rate-determining step.

• Electrical & Electronic Materials
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• v.4 no.4
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• pp.344-353
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• 1991

무정형 SiC 박막을 수평형 CVD반응기로부터 SiH$_{4}$ 및 H$_{2}$를 반응기체로 하여 실리콘 웨이퍼위에 증착시켜 제조하였다. 박막 성장 속도는 상압에서 650.deg.C와 850.deg.C범위에서 측정되었다. 반응기체의 유량은 1000sccm으로 고정하였으며 SiH$_{4}$와 CH$_{4}$의 유량을 변화시켰다. 증착 반응속도식으로 표면 반응이 율속단계인 Eley-Rideal 모델과 SiH$_{4}$와 CH$_{4}$의 종도에 m차로 비례하는 두가지 속도식을 가정하였다. 증착시간에 따른 SiC 박막두께의 측정으로부터 얻은 증착 반응 속도로부터 회귀 분석법에 의하여 두가지 반응속도식의 반응속도 상수를 구하였다. 얻어진 반응속도식에 의해서 계산된 값과 실험치를 비교한 결과 0.15차의 반응속도식이 Eley-Rideal반응기구보다 약산 더 잘 맞음을 알 수 있으나 두 모델 다 약간씩 실험결과와 차이가 나고 있다. 이것은 본 실험의 증착 조건의 율속단계가 확산 단계와 표면 반응 단계의 전이영역 즉 본 실험의 증착조건에서 확산속도와 표면 반응속도가 비슷하기 때문으로 생각된다. 또한 Eley-Rideal 반응기구에서 부터 얻어진 SiH$_{4}$ 및 CH$_{4}$의 흡착평형상수 $K_{s}$ 와 $K_{c}$ 값을 비교하면 1000K이하에서는 $K_{s}$ 가 $K_{c}$ 보다 큰 값을 가지는데 이것은 Gibbs 자유에너지 최소화 방법에서 구한 결과와 일치하였다.

• Transactions of the Korean hydrogen and new energy society
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• v.10 no.1
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• pp.9-17
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• 1999

The hydriding and dehydriding kinetics were studied for a Mg-25wt.%Ni mixture which has the most excellent hydrogen-storage characteristics among many mechanically-alloyed mixtures. The hydriding and dehydriding rates were measured and the rate-controlling steps were determined by comparing the hydriding and dehydriding rates with the theoretical rate equations. The rate-controlling step in the hydriding reaction is the Knudsen flow and the ordinary gaseous diffusion of hydrogen molecules through interparticle channels, cracks, etc. in the various ranges of weight percentage of absorbed hydrogen $H_a$ below $H_a$=4.0. In the $H_a$ range 4.0 < $H_a{\leq}4.25$, the diffusion of hydrogen atoms through the growing hydride layer is considered the rate-controlling step. The rate-controlling step in the dehydriding reaction is the Knudsen flow and the ordinary gaseous diffusion of hydrogen molecules for all the ranges of weight percentage of desorbed hydrogen $H_d$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.1
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• pp.7-12
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• 2004

The steps related to the nutrient solution management were divided into 4 categories. The resistance for water movement in every steps was proposed. The priorities among the steps were set according to the cultural situation, which were used as the basis for the management in perlite bag culture. The enhancement of historical root development is especially critical, as well as how to supply essential water efficiently by minimizing the water movement distance to the root, which is the narrowest neck of a bottle in solution management.

• Korean Chemical Engineering Research
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• v.54 no.3
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• pp.299-304
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• 2016

Characteristics of self-propagating reaction for the preparation of ZnO powder from precursors composed of nitrate and citrate compounds were examined. The ratio of C/N was maintained in range of 0.7~0.8 to initiate the self-propagating reaction between the reducing citrate and oxidizing nitrate groups. The samples were decomposed thermally by using TGA. The sudden decomposition occurred in the range of X > 0.5 in a very short time with a very sharp decrease of mass, indicating that the self-propagating reaction would occur. Friedman, Ozawa-Flynn-Wall and Vyazovkin methods were employed to predict the activation energy, reaction order and frequency factor of the reaction rate in the rate determining step of X < 0.5 range. The activation energy increased with increasing fractional conversion in the range of 46~130 (kJ/min). The reaction order decreased in the range of 2.9~0.9, while the frequency factor increased in the range of 85~278 ($min^{-1}$), respectively, with increasing the rate of temperature increase.

• Journal of the Korea Organic Resources Recycling Association
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• v.23 no.1
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• pp.23-28
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• 2015

This study was conducted to evaluate the biodegradation characteristics of food waste on various collection systems using anaerobic batch test. The ultimate methane production from food waste in standard plastic garbage bags (sample A) was $285.6mL\;CH_4/g$ volatile solids (VS) which is the lowest, and reaction constant was $0.215d^{-1}$. The ultimate methane production from food waste in waste vessel based on RFID (sample D) was $493.4mL\;CH_4/g$ VS which is the highest, and reaction constant was $0.162d^{-1}$. The determinants of rate limiting step on all samples showed positive numbers, and the methane production step was found a rate limiting step.

• Journal of the Korea Organic Resources Recycling Association
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• v.26 no.2
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• pp.53-63
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• 2018

The hydrolysis of organic solid waste, such as sludge, is the rate-limiting step of the anaerobic digestion. The longer rate-limiting step lead to decrease of treatment efficiency and increase hydraulic retention time and anaerobic digester. Therefore, the pre-treatment has been applied for accelerating the hydrolysis step. This study was investigated the effects of pre-treatment of waste activated sludge using ultrasonic and alkaline integrated treatment simultaneously. The results showed the cumulative methane production and the methane production rate increased while the lag phase decreased. Therefore ultrasonic and alkaline integrated pre-treatment of waste activated sludge resulted in acceleration of hydrolysis step in anaerobic digestion.

• Journal of the Korean Chemical Society
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• v.19 no.5
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• pp.339-342
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• 1975

The rates of consumption of iodine and gas evolution in hydrazine-iodine reaction in the presence of large excess of hydrazine have been studied in the pH range 0.5${\sim}$7. They are the same at very low pH and both increase to respective asymptotic values as pH is increased. The rate of iodine consumption is three orders of magnitude faster than the rate of gas evolution at higher pH. The results are explained by postulating that $N_2H_4$ but not protonated form reacts with iodine and an intermediate, probably $N_2H_2I_2$, is formed which decomposed by first order reaction of rate constant about 1.5${\times}10^{-3}sec^{-1}$ in neutral and weakly acidic solutions.