Biosorption of toxic acidic dye-Acid Blue 25, by aquatic plants

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 mu m), addition of neutral salts (20-100 mg KNO3/L and 20-100 mg KH2PO4/L), and salinity (0.5-40 g NaCl/L). The results of equilibrium 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 degrees C. FTIR analysis confirmed the responsibility of several functional groups on the surface of the biosorbents for the adsorption of AB25 in this process.