As I guess, you would like the process description, e.g. in the form of an equation/equations, to refer to the process mechanism. What are your experimental data?
Mirosław Grzesik Thank you, sir, for replying. I have the experimental data for photocatalytic degradation of an organic compound collected at different time intervals.
A kinetic model is based on a reaction mechanism. It might be simpler than a complete reaction mechanism. In a kinetic model only the reactions affecting the overall rate can be taken into account. Surely, that a mass/charge balance must be also taken into account.
Ansaf V Karim You basically revealed what could be guessed. Not a word about the process conditions, the reactor system, or its geometry. If you can disclose more information, please disclose it. Without it, no help will be possible.