Application of seed residues from Anadenanthera macrocarpa and Cedrela fissilis as alternative adsorbents for remarkable removal of methylene blue dye in aqueous solutions.

Two novel ecological and low-cost adsorbents were prepared from seed residues of the tree species Anadenanthera macrocarpa and Cedrela fissilis for the removal of methylene blue dye in water. The materials were comminuted and characterized by different techniques. The particles of samples have a rough surface with cavities. The optimum dosage and pH for both materials were 1 g L and pH 8. The pseudo-second-order model was the most suitable for describing the adsorption kinetics for both systems. The Anadenanthera macrocarpa presented a maximum experimental capacity of 228 mg g, while the Cedrela fissilis, a similar capacity of 230 mg g at 328 K. The Tóth model was proper for describing the equilibrium curves for both systems. The thermodynamic indicators show that the adsorption process is spontaneous and endothermic for both materials. The application of materials for the simulated effluent treatment showed 74 and 78% of color removal using Anadenanthera macrocarpa and Cedrela fissilis samples, respectively. Overall, seed residues of Anadenanthera macrocarpa and Cedrela fissilis could be potentially applied for adsorptive removal of colored contaminants in wastewater.