Equilibrium, Kinetic, Thermodynamic, and in Situ Regeneration Studies about Methylene Blue Adsorption by the Raspberry-like TiO2@yeast Microspheres

The raspberry-like TiO2@yeast hybrid microspheres were fabricated by electrostatic-interaction-driven self-assembly heterocoagulation. The obtained microspheres were used as adsorbents for the removal of cationic dye methylene blue in aqueous solutions. The adsorption performance was investigated by analyzing the influence of factors such as the initial pH, contact time, and temperature at different initial concentrations. Equilibrium data were described by the Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models. It was found that equilibrium data were best represented by the Langmuir isotherm model. The kinetic regression results manifested that adsorption kinetics was more accurately represented by a pseudosecond-order model and intraparticle diffusion was not the only rate-controlling step. The thermodynamic studies indicated that the adsorption process was spontaneous, entropy-gained, and of endothermic nature within the studied temperature range. Moreover, the dye-loaded TiO2@yeast could be effectively regenerated in situ by exploiting the structural advantages of itself.