Adsorption, kinetic and thermodynamic studies of safranin and methylene blue on a novel adsorbent based on phosphorylated sawdust

The effectiveness of phosphorylated sawdust (RSD@P) for the adsorption of both safranin and methylene blue from aqueous systems has been studied. The related adsorption factors; pH, stirring time, initial dye concentrations and amount of RSD@P have been demonstrated. The adsorption's dependence on temperature, adsorption kinetic and adsorption isotherms were studied. The pseudo-second-order model was more significant (R-2 = 0.99) for describing the adsorption kinetic of both dyes than the pseudo-first-order and Elovich ones. The adsorption process best fitted the Langmuir isotherm model (R-2 = 0.99) rather than the other studied models. The calculated adsorption capacities using the Langmuir model were 109.22, 124.72, 135.9 mg g(-1) for safranin and 123.46, 138.89, 158.73 mg g(-1) for methylene blue at 293, 303 and 318 K, respectively. Thermodynamic studies emphasized that the adsorption process was spontaneous, endothermic and physical in nature (Delta H-o = 12. 48, 12. 83 kj. mol(-1) for safranin and methylene blue, respectively). The results showed the elevation removal of dyes by @P rather than that obtained by raw sawdust using the same dosage (0.01 g) and experimental conditions. Thus, RSD@P can serve as a promising adsorbent for the removal of safranin and methylene blue from aqueous solutions.