This study investigates the methyl orange (MO) removal from aqueous solution through the application of ultrasound onto multiwalled carbon nanotubes (MWCNTs). Characterization of MWCNT was carried out using scanning electron microscopy (SEM) and tunneling electron microscopy (TEM). The influences of various parameters on the removal percentage were studied and optimized by a central composite design (CCD) and response surface methodology (RSM). Results indicate that a small amount of proposed adsorbent (0.025 g) is responsible for successful removal of 15 mg L-1 of MO (RE > 99%) in a short time (3.4 min) and pH of 1-2. Adsorption kinetic data are fitted well with pseudo second order model. Equilibrium data followed Langmuir isotherm model with maximum adsorption capacity of 53.76 mg g(-1). (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.