High-yield poly(aniline-co-m-sulfophenylenediamine) (PANSP) particles were synthesized by oxidative copolymerization of aniline (AN) and m-sulfophenylenediamine (SP) in HCl solution without any additional initiators. Morphologies and chemical structures of the as-synthesized PANSP were characterized by SEM, TEM, zeta potential, surface area, XRD, FTIR, UV-Vis and XPS spectra. Adsorption characteristics of the PANSP were examined using methylene blue (MB) as the adsorbate through batch adsorption tests. Results showed that product yield, morphology, chemical structure and adsorption property of the PANSP copolymers depended strongly on AN/SP molar ratios. Of the various PANSP, PANSP (8:2) (AN/SP molar ratio 8:2, product yield 67.1%) showed the best adsorption for MB, and the adsorption was favored at high temperature and in the pH range of 3.5-6.0. The adsorption isotherms followed the Langmuir model, while the adsorption kinetic followed the pseudo-second-order model. Results of the current study indicated that PANSP particles could be employed as an efficient adsorbent for dye removal. (C) 2014 Elsevier B.V. All rights reserved.