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Zero-order Reaction (zero-order + reaction)
Selected AbstractsPotential for octylphenol to biodegrade in some english riversENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2000Andrew C. Johnson Abstract To study octylphenol biodegradation, samples of river water and sediments were taken from the Aire and Calderr vers in the United Kingdom, running through urban/industrial areas, as well as the Thames River running through a more rural area. Using laboratory microcosms, half-lives of 7 to 50 d were obtained for the water samples, with most curves fitting a zero-order reaction. The Calder River was sampled at four separate points along a 45-km length, encompassing rural to increasingly urban/industrial reaches. Little degradation was observed in the sample from the upland/rural reach, while half-lives of 8 to 13 d were seen in the more urban/industrial reaches. Mineralization of the phenyl ring, detected by evolution of 14CO2 from ring-labeled octylphenol, was only observed in water from the Calder River sample. Degradation rate was similar for a range of concentrations from 0.3 to 100 ,,g/L when tested with river water from the Thames River. No degradation was observed over 83 d when bed sediments were spiked with octylphenol and incubated under anaerobic conditions. [source] Convection, diffusion, and exothermic zero-order reaction in a porous catalyst slab: Scaling and perturbation analysisAICHE JOURNAL, Issue 10 2009Joćo P. Lopes Abstract The analysis of the interaction between transport phenomena and chemical reaction inside large-pore catalyst particles needs to include intraparticular convection as an additional mass/heat transfer mechanism. In this work, we describe by a 3D regime diagram the global behavior of a permeable catalyst slab, where an exothermic, zero-order reaction is occurring. An order of magnitude estimate for the maximum temperature change is obtained by scaling techniques in each regime of operation. Specific operating regimes of fast mass/heat transport, dominant reaction and strong intraparticular convection, are then studied in more detail using perturbation analysis. The results include approximate concentration and temperature profiles, which allow the estimation of both the effectiveness factor and maximum temperature attained inside the catalyst in these regimes. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Basic equations of mass transfer through biocatalytic membrane layerASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2009Endre Nagy Abstract The diffusive and convective mass transport through biocatalytic membrane layer (membrane bioreactor), without and with biochemical reactions, have been investigated. Similarly to the two-film theory for gas-liquid system with diffusive mass transport, only, mass transfer rates have been developed for the biocatalytic membrane layer and for the concentration boundary layer on the feed side of the membrane. Overall mass transfer coefficient has also been defined involving the two-layer, simultaneous mass transfer, namely the mass transfer through the concentration boundary layer and biocatalytic membrane layer. The effect of the convective velocity (Pe number) and the biochemical reaction rate, namely first-order and zero-order reactions as limiting cases of the Monod kinetics, are demonstrated on the mass transfer coefficients accompanied by chemical reaction and on the concentration profiles. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | ||||||||||