The chemically polyaniline (PANI) powder formed in hydrochloric acid medium was synthesized. The polymer was thermally treated in air at 180 degrees C that leads to changes in the PANI structure due to crosslinking through tertiary amine groups. The different changes in the structure that appears between the conventional PANI and crosslinked PANI were characterized by using X-ray diffraction, Fourier transform infra-red spectroscopy, thermogravimetric analysis, scanning electronic microscope, and Nitrogen adsorption-desorption isotherms. The developed material is agglomerated nanoparticles structure of sizes approximately 30-100 nm and pores that may release the appearance of a spongy structure. The specific surface area was calculated to be 349 (m(2)/g). It was utilized as an adsorbent for cationic dye such as methylene blue (MB) as a model from aqueous solution. The kinetics and the isotherm adsorption models were investigated. The adsorption of MB into the crosslinked PANI was found to obey second order kinetics. (C) 2012 Elsevier B.V. All rights reserved.