Is the adsorption of dissolved iodine onto activated carbon physical adsorption or chemical adsorption?
The mechanism(s) of iodine adsorption into carbons are complex and strongly dependent on each carbon. That is, iodine can be physisorbed in the carbon micro/mesopores, but in carbons with a rich surface chamistry, it can also be chemically adsorbed through charge transfer interactions.
There are many papers about this, but this one shows clear evidence of both mechanisms. (Written by the carbon "connoisseur" Harry Marsh).
They clearly mention:


  Thus, both classical physical adsorption theory and more specific chemical interactions have been proposed to model the adsorption of iodine by carbonaceous materials.


Strong evidence is provided in the paper itself.