The adsorption process is generally classified as physisorption (characteristic of weak van der Waals forces) or chemisorption (characteristic of covalent bonding).

Perhaps the passive adsorption-physisorption and active -chemisorption.

http://physics111.lib.berkeley.edu/Physics111/Reprints/MSDS%20Sheets/Absorption%20of%20beads204.pdf

you can find difference between passive and forced adsorption (not active)

Dear Setareh,

Suppose you have a giant molecule - like protein which has many functional groups which can interact with a solid surface. Such a groups in jargon are called feet.

When such a foot makes a contact and establishes interaction with SOLID surface -

it is the case of "passive absorrption" --- because ONLY ONE of many feet made an intermolecular contact with the Solid Surface (SS) 

Now - if you subject such a system (with only 1 contact) by stream of e.g. water -

this contact will be broken and the whole protein molecule will go away with the stream.

I have studied the thrombus-resistant (artificial) polymeric materials. And in order to avoid thrombus formation - it is necessary - the protein molecule to form 1 or 2 or very few contacts with the material of an artificial blood vessel -- only in this case - in case

of "passive absorption" (when in  molecular interaction participate few protein's groups ("feet") - the absorption is REVERSIBLE=passive.

But in case of formation of  many feet-contacts - the sorption becomes irreversible

(case of "common"/active sorption).

Please see attachment from the book:"The ELISA Guidebook" where the case of "passive absorption" is explained (I guess) better than I did.

Best Regards,   Leonid

It seems that this is one term used but it seems to have no meaning. Passive makes no sense related to adsorption. There is no will of the adsorbing molecules. Balance of energetic and entropic effects decides whether they will be enriched at the interface or not.

Dear Dr. Vladimirov,

I appreciate your answer to my question. I think you had the exact answer which is directly linked to the subject. It was all informative.

Thank you again with best wishes,

Setareh