Illumination of biosorption of Allura Red on Rhus coriaria L. (sumac) plant: equilibrium, kinetic, thermodynamic, and density functional theory–based analyses

In the present paper, the biosorption capability of Rhus coriaria L. (sumac) plant for the effective removal of Allura Red (AR) dye from wastewater was tested in the light of theoretical and experimental tools. The reactive functional groups in the structure of the studied biosorbent and the surface morphology of the mentioned biosorbent were highlighted with the help of FTIR spectrophotometer, SEM (scanning electron microscopy), and EDX (energy-dispersive X-ray analysis). The effect of important parameters such as pH, time, adsorbent mass, and temperature on the biosorption process was checked and discussed in detail. pH 2 was determined as the optimum value for the highest biosorption. Maximum effectiveness was reached at a biosorbent mass of 200 mg. The biosorption process adhered to the Langmuir isotherm and PSO kinetic models, and the process was determined to have a spontaneous and exothermic nature. Through the recovery experiments, it was noted that the studied plant retained approximately 30% of its biosorption capacity after three cycles. To prove the power of the interaction between Allura Red dye and dominant components of Rhus coriaria L. (sumac), density functional theory calculations were performed. Theoretically obtained conceptual DFT-based descriptors, the comments made within the framework of popular electronic structure rules, and calculated adsorption energies were in good agreement with the experimentally obtained data. As a result, it was reported that Rhus coriaria L. can be used as an effective and useful biosorbent for the removal of AR from wastewater.