Activated carbons were obtained from rose stems by the pyrolysis method. The experimental variables included activation method and the temperature of pyrolysis. The activated carbons obtained were fully characterized by different physicochemical techniques. The volatile organic compounds (tars) formed during pyrolysis of the biomass were studied. The adsorption of Ni(II) onto the activated carbons was determined from isotherms recorded at variable pH and kinetic curves at constant pH. Increasing the activation temperature and the use of ultrasound induced an increase in the surface area of the material. The solids obtained with ultrasound treatment showed a predominantly microporous character, while those obtained in the absence of ultrasound and at lower temperatures showed jointly mesoporous and microporous character. The adsorption kinetics of Ni(II) were described by a pseudo-second order model in which the highest rate of adsorption (6.41 mg g–1 min–1) was obtained for the carbon treated at 700 °C with ultrasound.