adsorption of textile dyes on willow tree pollen: determination of equilibrium, kinetics, and thermodynamic

In this study, the characterization and adsorption properties of brilliant cresyl blue (bcb- ald) and acid blue-25 (ab-25) dyes were investigated using willow tree pollen, a low-cost natural adsorbent. all adsorption tests were performed in consideration to contact time, adsorbent concentration, adsorbent dosage, and temperature functions. equilibrium isotherms were explained in terms of the langmuir, freundlich, temkin, and dubinin radushkevich (d-r) linear adsorption equations. it was found that adsorption complied with the langmuir equation. moreover, pseudo-first order, pseudo-second order, and intraparticle diffusion models were used to determine kinetic data. experimental data showed a match with the pseudo-second-order kinetic model. thermodynamic parameters such as enthalpy, gibbs free energy, and entropy were examined for willow tree pollen samples. the data obtained led us to the conclusion that adsorption is a spontaneous process. on the other hand, positive enthalpy indicates that adsorption is endothermic. positive entropy values are a result of changes on the adsorbent surface. characteristic results and dimensionless separation factors (rl) indicate that pollen can be used as an alternative to commercial adsorbents to remove bcb- ald and ab-25 from aqueous solution and wastewater.