Bio-adsorption performances of methylene blue (MB) dye on terrestrial and marine natural fibers: Effect of physicochemical properties, kinetic models and thermodynamic parameters

Biomass residues and algal wastes were used for the first time to produce new efficient adsorbents from lignocellulosic powders from Solanum elaeagnifolium Cavanilles (SE. Cav) and Gelidium elegans (G. elegans), respectively, for the efficient removal of methylene blue (MB) dye in aqueous systems. The physicochemical features and the efficiency of the bio-sorbents were successfully characterized by FTIR, XRD, TGA/DTG, BET, SEM and isoelectric point (pH(pzc)) tests. The results indicate that both bio-adsorbents have an overall surface acid due to the occurrence of hydroxyl and carboxylic groups, which directly impact the binding of cationic molecules to the surface. SE. Cav showed an ultimate monolayer absorbency of 50.607 mg/g at neutral pH (6.8) and room temperature (24 degrees C). However, under the same conditions, G. elegans exhibited a higher value (76.689 mg/g). The adsorption kinetics indicates that both materials fit the pseudo-second-order (PSO) model as the correlation factors are quite near to unity. The parameters obtained from the equilibrium data showed that the experimental results fit well with the Langmuir, Freundlich, Redlich-Peterson and Sips isotherms for both bio-adsorbents. Moreover, the thermodynamic parameters suggest that the MB adsorption process for the two materials was exothermic and spontaneous.

Automated summary

This study for the first time used biomass residues and algal wastes to produce efficient adsorbents for the removal of methylene blue dye from water. The bio-sorbents showed good physicochemical features and efficiency, and the adsorption process was found to be exothermic and spontaneous.