The emerging agenda for sustainable development and global warming control searches urgent researches to reduce environmental impacts. In this sense, activated carbons from agroindustrial wastes are widely used as adsorbents in food and pharmaceuticals industries, mainly for the separation and purification of biomolecules, due to their complex pore structure and high surface area. This research evaluates the corn straw activated carbon obtained from the chemical impregnating with phosphoric acid under stirring for 30 min, being sequentially drying at 50 °C and characterized looking for water treatment application. The adsorption of methylene blue from aqueous solutions was investigated by batch experiments carried out at 30 °C and 100 rpm, obtaining 99 mg g-1 as the maximum adsorption capacity. The activated carbon had different functional groups when compared to its precursor material, an iodine value of 405.83 mg I2 g-1 and pHPZC of 5.75, characterizing it as slightly acidic, with a surface area of 409.314 m2 g-1, presenting potential as a biosorbent for technological application.