• Environmental Engineering Research
• /
• v.24 no.2
• /
• pp.309-317
• /
• 2019

This study evaluated the kinetics of acrylamide (AM) biodegradation by mixed culture bacteria and Enterobacter aerogenes (E. aerogenes) in sequencing batch reactor (SBR) systems with AQUASIM and linear regression. The zero-order, first-order, and Monod kinetic models were used to evaluate the kinetic parameters of both autotrophic and heterotrophic nitrifications and both AM and chemical oxygen demand (COD) removals at different AM concentrations of 100, 200, 300, and 400 mg AM/L. The results revealed that both autotrophic and heterotrophic nitrifications and both AM and COD removals followed the Monod kinetics. High AM loadings resulted in the transformation of Monod kinetics to the first-order reaction for AM and COD removals as the results of the compositions of mixed substrates and the inhibition of the free ammonia nitrogen (FAN). The kinetic parameters indicated that E. aerogenes degraded AM and COD at higher rates than mixed culture bacteria. The FAN from the AM biodegradation increased both heterotrophic and autotrophic nitrification rates at the AM concentrations of 100-300 mg AM/L. At higher AM concentrations, the FAN accumulated in the SBR system inhibited the autotrophic nitrification of mixed culture bacteria. The accumulation of intracellular polyphosphate caused the heterotrophic nitrification of E. aerogenes to follow the first-order approximation.

• Journal of Korean Society for Atmospheric Environment
• /
• v.18 no.E3
• /
• pp.165-174
• /
• 2002

A dual -column biofilter system with two different composts was used to investigate the macro-kinetics of dim-ethyl disulfide (DMDS) degradation. The biofilter columns were filled with compost mixtures up to one meter, The gas How rate and DMDS concentration to the biofilters were varied to study their effect on the removal characteris-tics of DMDS. It was found that the biodegradation of DMDS was governed by zero-order reaction -limited macro-kinetics for inlet DMDS concentrations between 10 and 55 ppmv. The overall average zero-order kinetic coeffi-cient for DMDS removal by compost was 0.50 ($\pm$0.1) ppm/sec for both compost mixtures studied. Variations in individual kinetic coefficients were observed due to varying environmental conditions, such as pH and temperature. The kinetic coefficients determined are specific to the system discussed in this work. During high acidity conditions in the filter beds, methyl mercaptan (MM) was observed in the gas samples collected. Appearance of MM was pro-bably due to decreased microbial activity in the lower portions of the biofilter. Considering the neutral pH range required and the presence of methyl mercaptan, it is likely that the microorganisms present in the biofilters used in this research are similar to the T. thioparus (strain E6) species.

• Membrane and Water Treatment
• /
• v.5 no.4
• /
• pp.281-293
• /
• 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.

• Journal of Environmental Science International
• /
• v.25 no.12
• /
• pp.1717-1726
• /
• 2016

In this study, the reductive decolorization of three acid and basic dyes using modified zero-valent iron (i.e., acid-washed iron (Aw/Fe) and palladium coated iron (Pd/Fe)) at various pH conditions (pH 3~5) was experimentally investigated and the decolorization characteristics were evaluated by analyzing the absorbance spectra and reaction kinetics. In the case of acid dyes such as methyl orange and eriochrome black T, color removal efficiencies increased as initial pH of the dye solution decreased. However, the color removal of methylene blue, a basic dye, was not affected much by the initial pH and more than 70% of color was removed within 10 min. During the decolorization reaction, the absorbance of methyl orange (${\lambda}_{max}=464nm$) and eriochrome black T (${\lambda}_{max}=528nm$) decreased in the visible range but increased in the UV range. The absorbance of methylene blue (${\lambda}_{max}=664nm$) also decreased gradually in the visible range. Pseudo-zero order, pseudo-first order, and pseudo-second order kinetic models were used to analyze the reaction kinetics. The pseudo-second order kinetic model was found to be the best with good correlation. The decolorization reaction rate constants ($k_2$) of methylene blue were relatively higher than those of methyl orange and eriochrome black T. The reaction rate constants of methyl orange and eriochrome black T increased with a decrease in the initial pH.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 1999.04a
• /
• pp.62-63
• /
• 1999

Reduction 2,4,6-Trinitrotoluene by zero valent iron was studied in a batch reactor under anoxic conditions. Results showed that the removal of TNT was a pseudo-first order and the rate was dependent on the available metal surface area. Final product, presumably triaminotoluene, accumulated in the solution as well as on the metal surface. However, little amounts of aminodinitrotoluenes were detected. Therefore, it is postulated that the reduction of nitro group occurs simultaneously in all three position.

• Journal of Pharmaceutical Investigation
• /
• v.25 no.1
• /
• pp.47-54
• /
• 1995

Transdermal patch formulations of estradiol to treat post-menopausal symptoms and prevent osteoporosis in women were developed and evaluated for the permeation characteristics through the excised hairless mouse abdorminal skin and the uterotropic effect on the ovariectomized rabbits. The design of patch formulations was optimized by varying several formulation parameters, such as type of enhancers, amount of enhancers, amount of drug loading and coating thickness. Compared to a commercially available transdermal product, several patch formulations showed the similar skin permeation profiles (following zero-order kinetics), but their skin permeation rates were lasted for the longer period (a week). In one-week uterotropic efficacy test in the ovariectimized rabbits, the selected patch formulations showed the positive effect in atrophy of the urogenital epithelium. The mean values of uterus weight in rabbits after application of patches containing estradiol were much higher than those in control group (containing no drug).

• Journal of the Korean Home Economics Association
• /
• v.11 no.1
• /
• pp.44-56
• /
• 1973

The effect of the temperature and the time of scalding, and the addition of various seasoning on the remaining % of total Vitamin C contained in Spinach (Spinacia oleracea) was studied and discussed by means of chemical kinetics. The quantitative measurements of total Vitamin C were made by 2,4-dinitrophenyl hydrazine (DNPH) method with Clinical Electrophotometer (Fisher). The sample spinach contains 39.88mg. % of total vitamin C on the average, and the ratio of oxidized and reduced forms of Vitamin C is 1 : 4.7. When the sample spinach was scalded, the kinetics of the decrease of the remaining total vitamin C. % was observed to follow the first order reactions regardless of the temperatures applied (i,e. 70$^{o}$ , 80$^{o}$ , 90$^{o}$ and 100$^{o}$ ) with half-life range of 2.10 - 1.47 minutes. In the case of the addition of various seasonings, the addition of various seasonings, the kinetics remaining Vitamin C % showed to be the zero order reactions regardless of the kinds of seasonings and storage temperatures. With the addition of seasonings, the stability of Vitamin C was found to be increased in the order table salt+sesame oil+vinegar+soybean sauce, without seasoning, table salt+sesame oil, table salt+sesame oil+soybean sauce.

• Proceedings of the KOSOMBE Conference
• /
• v.1998 no.11
• /
• pp.237-238
• /
• 1998

The kinetics of sulfite oxidation must be fast and the concentration of sulfite must be low to emulate oxygen uptake by blood. The kinetics were studied yielding a first order rate constant in sulfile, zero order in oxygen. Limitations of the technique were evaluated using the experimental rate constant and an adaptation of Lightfoot's approximation, while the reaction of hemoglobin is reversible and essentially instantaneous, that for sulfite is irreversible and finite. Thus if the approach to saturations not monotonic or if the mass transfer resistance is significantly lowered, e. g. when blood film thicknesses are thinner than a few hundred microns, deviations may occur.

• Nuclear Engineering and Technology
• /
• v.4 no.4
• /
• pp.322-326
• /
• 1972

The retention of $^{51}$ Cr was studied as chromate after dissolution of irradiated ammonium chromate with reactor exposure time and various storage time at room temperature. The annealing process of ammonium chromate depending on various storage time at room temperature follows first-order kinetics from zero time value to the pseudo-equilibrium value. The retention is increased with reactor irradiation time, also following first-order kinetics.

• Preventive Nutrition and Food Science
• /
• v.4 no.4
• /
• pp.246-250
• /
• 1999

This study was conducted to develop the fermentation kinetic modeling for the prediction of pH and acidity changes in kimchi at isothermal and nonisothermal fermentation temperatures(0~15$^{\circ}C$) and salt concentrations(1.5~4.0%) using the traditional two-step method and alternative one-step method. The calculations of the two-step method of pH and acidity change during fermentation followed the pattern of the first order and zero order, respectively. The reaction rate constant of pH by the first order was increased from 0.008 {TEX}$day^{-1}${/TEX} to 0.017 {TEX}$day^{-1}${/TEX} by increasing the temperature from $0^{\circ}C$ to 15$^{\circ}C$ at 2.75% of salt concentration, and was decreased from 0.013 {TEX}$day^{-1}${/TEX} to 0.010 {TEX}$day^{-1}${/TEX} by increasing the salt concentration from 1.5% to 4.0% at 5$^{\circ}C$. For the pH and acidity of Kimchi, the zero order had a higher correlation than the first order to the estimate of the kinetics parameters by the one-step method. The {TEX}$E_{a}${/TEX} ranges of pH and acidity were 61.057~66.086 and 62.417~68.772 kJ/mole with different temperatures and salt concentrations. This one-step method had smaller and more realistic estimates of error(p〈0.05). The effective temperatures, {TEX}$T_{eff}${/TEX}, with 0~15$^{\circ}C$ of square function type of 12 hr intervals were 12.85, 11.48 and 12.46$^{\circ}C$ as increasing the salt concentration, 1.50, 2.75 and 4.00%, respectively. The {TEX}$T_{eff}${/TEX} were higher values than the mean temperature(7.5$^{\circ}C$).