Enteromorpha prolifera based-activated carbons were prepared using chemical activation by H 4 P 2 O 7 (PAC) and KOH (KAC) and applied as a potential adsorbent for the adsorption of acid scarlet (GR). N 2 adsorption–desorption isotherms, scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and Boehm titration were used to compare the porous structure, surface chemical property and adsorption behavior of carbon. KAC presented higher surface area (3500m 2 /g) and larger total pore volume (2.872cm 3 /g). To account for the adsorption mechanisms, the kinetic models, including pseudo-first-order model, pseudo-second-order model, intraparticle diffusion model and Boyd model were introduced. The Langmuir isotherm model was better fitted with the equilibrium data than Freundlich and Dubinin–Radushkevich models. The maximum adsorption capacities of GR onto KAC and PAC were 2500mg/g and 454mg/g, respectively. The physical adsorption and ion-exchange were the dominating adsorption mechanism.