The removal of Al (III) ions from aqueous solution by locally abundantly low-cost fresh macrophyte, alligator weed. was examined in batch system. Effect of initial solution pH on Al (III) adsorption was investigated and the Al (III) species present in aqueous solution were identified. The main functional groups of the alligator weed were characterized by Fourier transform infrared spectrometer (FT-IR). The equilibrium data fitted to Freundlich and Langmuir isotherms satisfactorily. The pseudo-second-order equation fitted the kinetic data very well. The intraparticle diffusion played an important role in the Al (III) sorption process. Al (III) ions were favorably adsorbed by alligator weed and the values of K-f and 1/n (Freundlich constant) at 25 degrees C and pH 3.5 were found as 1.9963 (mg/g)/(mg/L)(1/n) and 0.7875, respectively, which are comparable to those of granular activated carbon (2.20 (mg/g)/(mg/L)(1/n) and 0.8695, respectively). (C) 2009 Elsevier B.V. All rights reserved.