Design, Spectroscopic Analysis, DFT Calculations and Biosorption Evaluation of Pristine Ostrich Bone Biosorbent towards efficient removal of hexavalent chromium and flavoring and coloring agents from wastewater in single and multi-contaminant system

This research describes using pristine ostrich bone wastes (OB) as a biosorbent to adsorb several Azorubine (E122), Ponceau 4R (E124), and Red Allora (E129) dyes, as well as the hexavalent chromium ion Cr(VI). The physicochemical properties and morphology of OB biosorbent were investigated using BET, SEM, FTIR, TGA, 1HNMR, and XRD. The impact of experimental parameters on the removal behavior of the pollutants under study was evaluated by adjusting the contact time, adsorbent amount, solution pH, temperature, and concentration. The adsorbate removal on OB biosorbent was obtained in the following order: E124> Cr(VI)> E122> E129. The adsorption kinetics of the investigated pollutants have been studied for single and multicomponent systems in terms of pseudo-first- and second-order kinetics. Freundlich and Langmuir isotherm models have also been applied to the equilibrium adsorption data. The outcomes demonstrated that the adsorption process adhered to a pseudo-second-order kinetic model was exothermic spontaneous. With the highest adsorption capacity, the Langmuir model provided the greatest fit to the sorption isotherm data at 303 K, being 85.66 mg/g, 86.67 mg/g, 157.76 mg/g, and 180.4 mg/g, for E129, E122, Cr(VI), and E124, respectively. Additionally, DFT calculations were utilized to verify the molecular structure, analysis of Frontier Molecular orbitals (FMOs), molecular electrostatic potential (MEP) and reactivity descriptor for all phases. The plausible mechanism of adsorption of the pollutants onto OB biosorbent is elucidated.