A carbonaceous adsorbent prepared from hulls of Vitexdoniana by H3PO4 treatment was investigated for its efficiency in methylene blue (MB) and of methyl orange (MO) adsorption in aqueous solution. The characterizations of materials are carried out by Fourier Transform Infrared Spectroscopy (FTIR), pH (6.2) and the iodine index measurement which showed that our powder activated carbon is primarily made up of meso and macro pores. The influence of major parameters governing the efficiency of the process such as, solution pH, sorbent dose, initial concentration, ionic strength and contact time on the removal process was explored. The Times of balance of adsorption are obtained to 40 and 50 minutes respectively for the MB and MO. The outputs of elimination of the molecules of the MB and MO to this balance are respectively to 85.92% and 46.60%. The variation of pH showed that the maximum of adsorption of the MB is with pH=10 and for MO, the maximum of adsorption is with pH=3. Four theoretical adsorption isotherms namely Langmuir, Freundlich, Temkin and Dubinin -Radushkevic were used to describe the experimental results. The models of Temkin and Dubinin- Radushkevic describe better the adsorption of the methylene blue. The model of Langmuir is that which corroborates, better than others, with the experimental results in the case of methyl orange. The reaction of adsorption of the two dyes is endothermic and the mechanism of adsorption is chemical. The pseudo-first order kinetic models, pseudo second order, Elovich and intra particulate have been applied to the experimental data and that which is appropriate is the kinetic model of pseudo second order.