This study deals with the preparation of adsorbents from a commercial xerogel by chemically modifying its surface with concentrated mineral acids and alkali metal chlorides, their physicochemical characterization, and their use as adsorbents for gallic acid in aqueous solution. The prepared adsorbents have a high specific surface area (347-563 m2 g-1), better pore development for samples treated with alkali metal chlorides than with mineral acids and are more acidic than the initial xerogel (p.z.c range 2.49-6.87 vs. 7.20). The adsorption properties of the commercial xerogel improved over a wide range of pH and temperature. The experimental results indicate that the adsorption process is thermodynamically favored.