• Title, Summary, Keyword: kinetics

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Flocculation Kinetics Using Fe(III) Coagulant in Advanced Water Treatment: The Effect of Sulfate Ion (상수처리시 Fe(III) 응집제를 이용한 응집동력학에 관한 연구 : 황산이온의 영향)

  • 강임석;이병헌
    • Journal of Environmental Science International
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    • v.4 no.4
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    • pp.367-377
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    • 1995
  • The study of flocculation kinetics is of fundamental interest in the field of water treatment, because rational study of the factors affecting the coagulation process should be based on the rate of particle growth. The effect of sulfate on flocculation kinetics were examined using ferric nitrate as a coagulant to coagulate kaolin clay in water under several experimental conditions. Both the particle size distribution data obtained from the AIA and the on-line measurement of turbidity fluctuation by the PDA were used to measure flocculation kinetics. Results show that sulfate ion added to the kaolin suspension played an important role in the flocculation process, not only improving flocculation kinetics at more acidic pH levels but also changing surface charge of particles. The kinetics of flocculation were improved mainly by the enhanced rate and extent of Fe(III) precipitation attributed to the addition of sulfate, and thereby, better interparticle collision frequency, but little by the charge reductions resulting from the sulfate addition. The increase in sulfate concentration beyond $3\times10^{-4}M (up to 2\times10^{-3}M)$ did not induce further improvement in flocculation kinetics, although the higher concentrations of sulfate ion substantially increased the negative ZP value of particles. Key Words : Flocculation Kinetics, Fe(III) Coagulant, Sulfate ion, Turbidity Fluctuation.

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Isoconversional Cure Kinetics of Modified Urea-Formaldehyde Resins with Additives

  • Park, Byung-Dae
    • Current Research on Agriculture and Life Sciences
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    • v.30 no.1
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    • pp.41-50
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    • 2012
  • As a part of abating formaldehyde emission of urea-formaldehyde resin, this study was conducted to investigate the rmalcure kinetics of both neat and modified urea-formaldehyde resins using differential scanning calorimetry. Neat urea-formaldehyde resins with three different formaldehyde/urea mol ratios (1.4, 1.2 and 1.0) were modified by adding three different additives (sodium bisulfite, sodium hydrosulfite and acrylamide) at two different levels (1 and 3wt%). An isoconversional method at four different heating rates was employed to characterize thermal cure kinetics of these urea-formaldehyde resins to obtain activation energy ($E{\alpha}$) dependent on the degree of conversion (${\alpha}$). The $E{\alpha}$ values of neat urea-formaldehyde resins (formaldehyde/urea = 1.4 and 1.2) consistently changed as the ${\alpha}$ increased. Neat and modified urea-formaldehyde resins of these two F/U mol ratios did show a decrease of the $E{\alpha}$ at the final stage of the conversion while the $E{\alpha}$ of neat urea-formaldehyde resin (formaldehyde/urea = 1.0) increased as the ${\alpha}$ increased, indicating the presence of incomplete cure. However, the change of the $E{\alpha}$ values of all urea-formaldehyde resins was consistent to that of the Ea values. The isoconversional method indicated that thermal cure kinetics of neat and modified urea-formaldehyde resins showed a strong dependence on the resin viscosity as well as diffusion control reaction at the final stage of the conversion.

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Comparison of Bioleaching Kinetics of Spent Catalyst by Adapted and Unadapted Iron & Sulfur Oxidizing Bacteria - Effect of Pulp Density; Particle Size; Temperature

  • Pradhan, Debabrata;Kim, Dong-Jin;Ahn, Jong-Gwan;Gahan, Chandra Sekhar;Chung, Hun-Saeng;Lee, Seoung-Won
    • Korean Journal of Metals and Materials
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    • v.49 no.12
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    • pp.956-966
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    • 2011
  • Bioleaching studies of metals from a spent catalyst were conducted using both adapted and unadapted bacterial cultures. The bacterium used in this experiment was Acidithiobacillus ferrooxidans. A comparison of the kinetics of leaching was made between the two cultures by varying the leaching parameters, including the pulp density, particle size and temperature. Both cultures showed similar effects with respect to the above parameters, but the leaching rates of all metals were higher with the adapted compared to the unadapted bacterial cultures. The leaching reactions were continued for 240 h in the case of the unadapted bacterial culture, but only for 40 h in the case of the adapted bacterial culture. The leaching reactions followed first order kinetics. In addition, the kinetics of leaching was concluded to be a diffusion control model; therefore, the product layers were impervious.

Quantitative Polymerase Chain Reaction for Microbial Growth Kinetics of Mixed Culture System

  • Cotto, Ada;Looper, Jessica K.;Mota, Linda C.;Son, Ahjeong
    • Journal of Microbiology and Biotechnology
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    • v.25 no.11
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    • pp.1928-1935
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    • 2015
  • Microbial growth kinetics is often used to optimize environmental processes owing to its relation to the breakdown of substrate (contaminants). However, the quantification of bacterial populations in the environment is difficult owing to the challenges of monitoring a specific bacterial population within a diverse microbial community. Conventional methods are unable to detect and quantify the growth of individual strains separately in the mixed culture reactor. This work describes a novel quantitative PCR (qPCR)-based genomic approach to quantify each species in mixed culture and interpret its growth kinetics in the mixed system. Batch experiments were performed for both single and dual cultures of Pseudomonas putida and Escherichia coli K12 to obtain Monod kinetic parameters (μmax and Ks). The growth curves and kinetics obtained by conventional methods (i.e., dry weight measurement and absorbance reading) were compared with that obtained by qPCR assay. We anticipate that the adoption of this qPCR-based genomic assay can contribute significantly to traditional microbial kinetics, modeling practice, and the operation of bioreactors, where handling of complex mixed cultures is required.

Dependence of an Interfacial Diels-Alder Reaction Kinetics on the Density of the Immobilized Dienophile: An Example of Phase-Separation

  • Min, Kyoung-Mi;Jung, Deok-Ho;Chae, Su-In;Kwon, Young-Eun
    • Bulletin of the Korean Chemical Society
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    • v.32 no.5
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    • pp.1679-1684
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    • 2011
  • Interfacial reactions kinetics often differ from kinetics of bulk reactions. Here, we describe how the density change of an immobilized reactant influences the kinetics of interfacial reactions. Self-assembled monolayers (SAMs) of alkanethiolates on gold were used as a model interface and the Diels-Alder reaction between immobilized quinones and soluble cyclopentadiene was used as a model reaction. The kinetic behavior was studied using varying concentrations of quinones. An unusual threshold density of quinones (${\Gamma}_c$ = 5.2-7.2%), at which the pseudo-first order rate constant started to vary as the reaction progressed, was observed. This unexpected kinetic behavior was attributed to the phase-separation phenomena of multi-component SAMs. Additional experiments using more phase-separated two-component SAMs supported this explanation by revealing a significant decrease in ${\Gamma}_c$ values. When the background hydroxyl group was replaced with carboxylic or phosphoric acid groups, ${\Gamma}_c$ was observed at below 1%. Also, more phase-separated thermodynamically controlled SAMs produced a lower critical density (3% < ${\Gamma}_c$ < 4.9%) than that of the less phaseseparated kinetically controlled SAMs (6.5% < ${\Gamma}_c$ < 8.9%).

The Influence of High-heeled Shoes on Kinematics and Kinetics of the Knee Joint during Sit-to-stand task

  • Park, Ji-Won;Kim, Yun-Jin
    • The Journal of Korean Physical Therapy
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    • v.27 no.5
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    • pp.304-310
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    • 2015
  • Purpose: The purpose of this study was to examine the change in the kinematics and kinetics of the knee joint depending on high-heeled shoes during sit-to-stand (SitTS) task. Methods: Nineteen healthy females participated in this study. The subjects performed the SitTS task wearing high-heeled shoes and barefoot. The experiment was repeated three times for each task with foot conditions. The kinematics and kinetics of the knee joint were measured and analyzed using a 3D motion analysis system. Results: The result of this study showed kinematic and kinetics differences in knee joints during the SitTS task based on high-heeled shoes. Significant differences in knee flexion angle were observed during SitTS. The knee extensor force showed statistically significant differences during SitTS tasks. At the initial of SitTS, the knee flexor and extensor moment showed significant differences. The knee extensor moment showed statistically significant differences at the terminal of SitTS. At the maximum of SitTS, the knee extensor moment showed statistically significant differences. Conclusion: Therefore, wearing high-heeled shoes during SitTS movements in daily life is considered to influence knee joint kinematics and kinetics due to the HH, suggesting the possibility of increased risk of patellofemoral pain, and knee osteoarthritis caused by changes in loading of the knee joint.

Decolorization kinetics and characteristics of the azo dye acid red 18 in MSBR system at various HRTs and SRTs

  • Zonoozi, M. Hasani;Moghaddam, M.R. Alavi;Maknoon, R.
    • Membrane Water Treatment
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    • v.5 no.4
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    • pp.281-293
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    • 2014
  • The present work aimed to study the decolorization kinetics and characteristics of a selected azo dye under the influence of two key operational parameters including hydraulic retention time (HRT) and solid retention time (SRT). The decolorization efficiency and the two important criteria of k and normalized k (k/MLSS) were evaluated in lab-scale membrane sequencing batch reactors (MSBRs) at various HRTs of 48, 24 and 16 h (with constant SRT) and in addition, at various SRTs of infinity, 40 and 10 d (with constant HRT). According to the obtained results, both zero and first-order kinetics were properly fitted the decolorization profiles of the selected azo dye in all of the applied HRTs and SRTs. Increase of both HRT and SRT positively affected the decolorization efficiency. More MLSS concentrations corresponded to the lower HRTs and the higher SRTs resulted in higher decolorization rate constants (k). However, the effect of reducing the HRT was not compensated by increase of the MLSS concentration in order to reach higher decolorization efficiency. In addition, increase of the decolorization efficiency, as a consequence of the higher MLSS concentrations at longer SRTs, was restrained by decrease of the time-limited decolorization capability of biomass (represented by normalized k). Evaluation of both k and normalized k is suggested in order to have a more precise study on the decolorization kinetics and characteristics.