The oxidation of an activated carbon prepared from peach stones as well as the adsorption of aqueous ammonia using untreated and modified carbons is described here in. Boehm method in conjunction with temperature-programmed desorption (TPD) were mainly used to assess the chemical changes. These methods were complemented by chemical analysis, pH measurements and FT-IR spectra. Textural characterization was obtained from CO2 and N2 adsorption. Chemical modifications performed under the same experimental conditions with aqueous solutions of HNO3 and H2O2 indicated evidences that carboxylic acids like group formation is enhanced by short periods of time of HNO3 treatment at temperatures about 353 K followed by a mild oven-dry process in atmospheric air. The activated carbon modified under such conditions resulted to be the best ammonia adsorbent