Low pressure plasmas can be utilized for surface modification of carbon black and sepiolite granules, in order to improve their adsorption properties for acids in gas or vapour phase. The adsorption improvement can be achieved grafting basic groups (i.e. NH2) on the surface of carbon black in NH3 containing discharges or by depositing thin films, containing basic functionalities, in allylamine fed plasmas on both carbon black and sepiolite. The experimental results show that the adsorption increase, induced by allylamine plasma treatment, is due to chemical effects and not to variations of the surface morphology. The absolute improvement is particularly evident for carbon black. Relative adsorbed equivalents % per gram of carbon black (A)/sepiolite (B) granules, untreated and coated with plasma deposited allylamine thin film.