• Journal of Environmental Science International
• /
• v.6 no.2
• /
• pp.153-163
• /
• 1997

In order to fad the most fitted biodegradation model, biodegradation kinetics model to the initial phenol and p-cresot concentrations were investigated and had been fitted by the linear regression. Bacteria capable of degrading p-cresol were isolated from soil by enrichment culture technique. Among them, strain Ml capable of degradillg p.rcresol has also degraded phenal and was identified as the genus Micrococcus from the results from of taxonomical studies. The optimal tonditlons for the biodegradation of phenal and p-cresol by Micrococcus sp. Ml were $NH_4NO_3$ 0.05%, pH 7.0, 3$0^{\circ}C$, respectively, and medium volume 100m1/250m1 shaking flask. iwicrococcus sp. Ml was able to grow on phenal concentration up to 14mM and p-cresol concelltration up to 0.8mM. With increasing substrate concentraction, the lag period increased, but the maximum specific growth rates decreased. The yield coefficient decreased with increasing substrate concentation. The biodegradation kinetics of phenol and p-cresol were best described by Monod with growth model for every experimented concentration. In cultivation of mixed substrate, p-cresol was degraded first and phenol was second. This result implies that p-cresol and phenol was not degraded simultaneously.

• Carbon letters
• /
• v.6 no.3
• /
• pp.158-165
• /
• 2005

Room temperature kinetics of degradation of nerve agent simulants and sarin, an actual nerve agent at the surface of different carbon based adsorbent materials such as active carbon grade 80 CTC, modified whetlerite containing 2.0 and 4.0 % NaOH, active carbon with 4.0 % NaOH, active carbon with 10.0 % Cu (II) ethylenediamine and active carbon with 10.0 % Cu (II) 1,1,1,5,5,5-hexafluoroacetylacetonate were studied. The used adsorbent materials were characterized for surface area and micropore volume by $N_2$ BET. For degradation studies solution of simulants of nerve agent such as dimethyl methylphosphonate (DMMP), diethyl chlorophosphate (DEClP), diethyl cyanophosphate (DECnP) and nerve agent, i.e., sarin in chloroform were prepared and used for the uniform adsorption on the adsorbent systems using their incipient volume at room temperature. Degradation kinetics was monitored by GC/FID and was found to be following pseudo first order reaction. Kinetics parameters such as rate constant and half life were calculated. Half life of degradation with modified whetlerite (MWh/NaOH) system having 4.0 % NaOH was found to be 1.5, 7.9, 1206 and 20 minutes for DECnP, DEClP, DMMP and sarin respectively. MWh/NaOH system showed maximum degradation of simulants of nerve agents and sarin to their hydrolysis products. The reaction products were characterized using NMR technique. MWh/NaOH adsorbent was also found to be active against sulphur mustard.

• Journal of Microbiology and Biotechnology
• /
• v.15 no.5
• /
• pp.946-951
• /
• 2005

Biodegradation of the endocrine-disrupting chemical di-n-butyl phthalate (DBP) was investigated using a bacterium, Pseudomonas fluorescens B-1, isolated from mangrove sediment. The effects of temperature, pH, salinity, and oxygen availability on DBP degradation were studied. Degradation of DBP was monitored by solid-phase extraction using reversed-phase HPLC and UV detection. The major metabolites of DBP degradation were identified as mono-n-butyl phthalate and phthalic acid by gas chromatography-mass spectrometry (GC-MS) and a pathway of degradation was proposed. Degradation by P. fluorescens B-1 conformed to first-order kinetics. Degradation of DBP was also tested in seawater by inoculating P. fluorescens B-1, and complete degradation of an initial concentration of $100{\mu}g/l$ was achieved in 144 h. These results suggest that DBP is readily degraded by bacteria in natural environments.

• Korean Journal of Food Science and Technology
• /
• v.19 no.6
• /
• pp.515-519
• /
• 1987

The kinetics of thermal softening of chinese cabbage was investigated by puncture tests with an Instron. It was concluded that low temperature-long time blanching and pasteurization process provided an opportunity of improving the texture of pasteurized Kimchi. The rate of softening showed apparent first order kinetics, and the apparent Arrhenius activation energies ranged from 2.8-42.4 kcal/mol. The temperature dependency of the softening rate during pasteurization was more profound by blanching at blanching at higher temperature.

• Korean Journal of Materials Research
• /
• v.3 no.3
• /
• pp.276-281
• /
• 1993

In order to study the sintering kinetics of the ternery system, U-Ce-O, its shrinkage rate with time and temperature at the Ar atmoshpere were measured by using the dilatometer. At the sintering kinetics of U-Ce-O, sintering rate curve revealed bimodal and the first extreme point at bimodal curve was affected by the $UO_2$ the second one was due to the $CeO_2$. The sintering of $(U, Ce)O_2$ was delayed as increasing the $CeO_2$. At the same lOwt. % content, the highest sintering rate was observed at the $(U, Ce)O_2$ sample ball-milled for 4 hours.

• Microbiology and Biotechnology Letters
• /
• v.25 no.2
• /
• pp.173-177
• /
• 1997

Glycerol-3-phosphate cytidylyltransferase from Bacillus subtilis was modified with various chemical modifiers to determine the active sites of the enzyme. Treatment of the enzyme with group-specific reagents diethylpyrocarbonate, N-bromosuccinimide, or carbodiimide resulted in complete loss of enzyme activity, which shows histidine, tryptophan, and glutamic acid or aspartic acid residues are at or near the active site. In each case, inactivation followed pseudo first-order kinetics. Inclusion of glycerol-3-phosphate and/or CTP prevented the inactivation, indicating the presence of tryptophan and glutamic acid or aspartic acid residues at the substrate binding site. Analysis of kinetics of inactivation showed that the loss of enzyme activity was due to modification of a two histidine residues, single tryptophan residue, and two glutamic acid or aspartic acid residues.

• Journal of the Korean Chemical Society
• /
• v.16 no.1
• /
• pp.1-5
• /
• 1972

The adsorption kinetics on a membrane filter have been studied by an introduction of acid or alkali in yttrium-90 solution. The change of the adsorption in the filtration process was determined by the filtrate activities with using a microsyringe filter holder connected with a syringe. The over all reaction rate obeyed a reversible first order reaction, and the rate constants thus obtained, showed the values of $k_1$ = 0.12 $sec^{-1}$ and $k_1'$ = 0.039 $sec^{-1}$. As a result of the present studies, it would be reasonable that the rate determining step of the adsorption reaction was the hydrolysis reaction of the adsorbed yttrium ions.

• Journal of the Korean Chemical Society
• /
• v.18 no.3
• /
• pp.153-156
• /
• 1974

The kinetics of gas evolution in the reaction between hydrazine and iodine in a sulfuric acid medium has been studied at $25^{\circ}$. The rate is first order in hydrazine and iodine concentration. The iodide ion retards the reaction whereas the effect of hydrogen ion concentration is rather complicated. The rate of gas evolution is very close to that of iodine consumption.

• Journal of Environmental Health Sciences
• /
• v.14 no.1
• /
• pp.11-22
• /
• 1988

Calcium oxide, lithium oxide and titanium oxide were investigated as additives of zinc oxide for the removal of hydrogen sulfide at high temperature. This experiment was performed in the range of 1.0-2.0 vol.% H$_2$S concentration at 623-873 K reaction temperature, using a thermogravimetric analyzer. A pore blocking model was found to fit the reaction rate and the kinetics data were sucessfully expressed by this model. The reactions between additive sorbents and hydrogen sulfide were first order with respect to hydrogen sulfide concentration in a gaseous mixture with nitrogen. Among the used sorbents, ZnO-CaO 0.5 at.% and ZnO-TiO$_2$ 2.0 at.% sorbents had the best additive effects on the sulfidation reaction between additive sorbents and hydrogen sulfide, whereas the ZnO-Li$_2$O sorbents were ineffective.

• Archives of Pharmacal Research
• /
• v.18 no.2
• /
• pp.75-78
• /
• 1995

The analysis method nad stability test of antineoplaston A10, a new anticancer drug candidate, were established. A10 and phenylacetyl- L-glutamine, one of the degradation products, can be detected by high-performance liquid chromatography. The degradation kinetics of antineoplaston A10 in aqueous solutions from pH 1 to 10 buffers were carried out at 40, 50 and 60.deg.C. Pseudo-first order kinetics were obtained throughout the entire pH ranges studied. The pH-rate profiles showed that antineoplaston A10 was very unstable in alkaline conditions and most stable at pH 4.