Activated carbon from carrot dross (AC) was prepared, magnetized and used for the removal of p-nitrophenol from aqueous solution. The magnetization of AC was carried out by mixing the AC with diluted Fe3O4 sol in two different mass ratios of Fe3O4/AC. The characterization of both magnetized and original AC were studied by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, surface area measurement, elemental analyses, zero point charge measurement, and vibrating sample magnetometer. The surface area measurement of AC and magnetic activated carbons of carrot dross (MAC) with two mass ratios of Fe3O4/AC (1/8 and 1/5) were 447, 435, and 340 m(2) g(-1), respectively. Batch sorption studies for the AC and MAC were carried out at different pH values, solid to liquid ratios, contact times, and initial concentrations of the pollutant in the presence and absence of ultrasonic irradiation. The sorption isotherms were obtained in the range of 50-500 mg L-1. The results for the AC and MAC in the absence of ultrasound and for MAC in the presence of ultrasound fit well with Freundlich isotherm. In contrast, the results for AC in the presence of ultrasonic irradiation fit well with Langmuir model. In the case of AC, the values of intraparticle diffusion rate constant in the presence of ultrasound were greater than conventional method. In the case of MAC, the presence of magnetite nanoparticles on the surface of activated carbon led to a lower surface area but, the magnetic property of MAC facilitated the separation of solid phase from aqueous solution much easier than AC. (C) 2012 Published by Elsevier B.V.