[borhan_sd@yahoo.com]

Hi,I considered a reaction as Benzene(g)+Activated Carbon(s)==>Saturated adsorbent(s), In fact my system is an adsorption process,but because there isn't this process in fluent,I considered and defined this reaction.I want to consider Langmiur isotherm for the process in an udf as the reaction rate,but we know that "rate" is as d(concentration)/dt,and Langmiur eaquation is cs/qm=bcg/(1+bcg),that cs and cg are the concentrations of adsorbate in bulk and adsorbent ,respectively and b,qm are constants.
My problem is the relation between rate that includes "time" parameter and Langmiur equation mathematically,otherwise how can I define the rate using Langmiur equation?
Can anyone help?