The main objective of the model at this point is to predict the selective and continuous capture of a certain species present in a liquid solution onto the surface of functionalized solid particles. Once the species of interest reaches the surface of the particle, instantaneously an ion exchange reaction takes place; the species of interest is captured by the solid, while another species is released into the liquid medium. The reaction is reversible, although the capture is favoured. No gas phases are involved in my system. 

If DPM is a suitable approach, what type of particles should I consider? How can I include the reversible reaction that takes place between the species present in the liquid solution and the species attached to the solid particle, taking into account that this reaction only takes place once the targeted species get into contact with the solid?  One of the ultimate goals of the model is to obtain the concentration variation of the targeted species from the inlet of the system to the outlet.