Both microwave-assisted and conventional acidic treatments for the purification and functionalization of multi-wall carbon nanotubes were investigated. Impurities such as zeolite, catalyst particles and amorphous carbon were eliminated. In comparison to the harshness of the acidic treatment of a conventional technique, the microwave-assisted procedure makes it possible to obtain a material with a higher degree of purity (>98%) and -COOH functionalization in a shorter time, at a lower temperature, with a smaller amount and lower concentration of acid, as well as without agitation. An extensive step-by-step characterization of the treated samples has shown that the microwave-assisted treatment has limited effects on the significant characteristics of the nanotubes. (C) 2010 Elsevier B.V. All rights reserved.