Biosorption of Rhodamine B dye from aqueous solution by Rhus coriaria L. plant: Equilibrium, kinetic, thermodynamic and DFT calculations

Water-soluble basic rhodamine B (RhB) was adsorbed onto fruit powders of Rhus coriaria L. (Anacar- diaceae), sumac in batch reactions. Adsorption was optimized by employing concentration, pH, and time parameters. Experimental data were in accordance with the Freundlich isotherm, adsorption obeyed the pseudo-second-order kinetics, and thermodynamic parameters indicated that adsorption was exothermic, spontaneous, and chemical. Results were also evaluated by theoretical means: lowest Unoccupied Molec- ular Orbitals (LUMO), and the Highest Occupied Molecular Orbitals (HOMO). The HOMO energy values of the rhodamine B molecule had the highest activity with -3.3729 at the B3LYP level, -6.0361 at the HF level, and -4.3299 at the M062X level. In the calculations made, it was seen that the rhodamine B molecule has more electron density on the oxygen molecules. Taken together, the findings suggested that the dried fruit of the Rhus coriaria L. could be a useful biosorbent for the removal of dyes from aqueous media.