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. (Anacardiaceae), 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 Molecular 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.