Transient Langmuir model

A successor to PESTANS has recently been developed which allows the user to vary transformation rate and with depth l.e.. It can describe nonhomogeneous (layered) systems (39,111). This successor actually consists of two models - one for transient water flow and one for solute transport. Consequently, much more Input data and CPU time are required to run this two-dimensional (vertical section), numerical solution. The model assumes Langmuir or Freundllch sorption and first-order kinetics referenced to liquid and/or solid phases, and has been evaluated with data from an aldlcarb-contamlnated site In Long Island. Additional verification Is In progress. Because of Its complexity, It would be more appropriate to use this model In a hl er level, rather than a screening level, of hazard assessment. 

Transient deposition of hydrocarbons on zeolites during a cold start operation of the DOC can be modeled by the rate laws based on Langmuir or Temkin mechanism for physical adsorption/desorption (cf., e.g. Goralski et al., 2000 Koltsakis and Stamatelos, 2000 Kruglov and Aris, 1995 Kryl et al., 2005 Twigg, 2006). The rate laws for the adsorption and desorption of hydrocarbons are then... 

The transient response experiments were analyzed by a dynamic isothermal PFR model, and estimates of the relevant kinetic parameters were obtained by global nonlinear regression over all runs. It was found that a simple Langmuir approach could not represent the data accurately, and surface heterogeneity had to be invoked. The best fit was obtained using a Temkin-type adsorption isotherm with coverage-dependent desorption energy ... 

The platinum catalyzed CO oxidation of carbon monoxide was studied using an advanced transient reactor system, referred to as Multitrack. The experiments indicate, that the reaction is taking place according to the Langmuir-Hinshelwood reaction model. The desorption of CO from the catalyst surface was shown to be a kinetically relevant step in the reaction. From experiments performed using it was shown that isotopic mixing occurs on the catalyst surface due to the decomposition of CO present on the catalyst surface. 

A set of equations derived from the model assumptions complemented by Langmuir adsorption isotherm was used by Shi et al. (2009) to describe experimental steady-state and transient performance of a PEMFC in the presence of adsorbed toluene species in the cathode airstream. The model allowed the authors to quahtatively describe air-side toluene contamination observed for four different current densities (0.2,0.5,0.75, and 1.0 A/cm ) and three different concentrations (1,5, and 10 ppm). 

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