A B S T R A C T The adsorption of Acid Blue 25 (AB25) ions by aquatic plants, Potamogeton pusillus and Ceratophylum demersum from aqueous solutions was studied. The adsorption was studied as a function of solution pH (2-11), contact time (0-60 min), biomasses dosage (0.1-2.5 g/L), initial dye concentration (30-100 mg AB25 /L), biosorbents particle size (53-500 lm), addition of neutral salts (20-100 mg KNO 3 /L and 20-100 mg KH 2 PO 4 /L), and salinity (0.5-40 g NaCl/L). The results of

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... m adsorption were successfully described through Freundlich and Temkin isotherm for both of the biosorbents. Maximum adsorption capacity of 183.46 and 129.68 mg/g were observed for P. pusillus and C. demersum, respectively. Different kinetic models including pseudo-first order, pseudo-second order, and intra-particle diffusion were examined, and the pseudo-second order was shown to be the best model to fit the adsorption kinetics data. Thermodynamic parameters demonstrated that adsorption of AB25 ions was spontaneous and endothermic at a temperature range of 10-40˚C. FTIR analysis confirmed the responsibility of several functional groups on the surface of the biosorbents for the adsorption of AB25 in this process.