Activated charcoal for air purifier model

Good morning, I'm quite new with the software and I just would like to ask: what's the proper module to model an air purifier based on activated charcoal technology?

I'd like to have just a 2D model where air + gas to be collected are flowing from one side to the other of a rectangle and in between there is the activated carbon. I'm interested in see the concentration of the gas adsorbed by the charcoal.

Thanks