Geometry influenced adsorption of fluoxetine over the surface of RuFeO₃ and CeFeO₃ nanoparticles: Kinetics and thermodynamic studies

Novel mesoporous ferrite nanoparticles of ruthenium (RuFeO₃) and cerium (CeFeO₃) with large surface area were successfully fabricated by hydrothermal method and applied for the removal of fluoxetine from aqueous solution. The morphology and physicochemical properties of meso-porous metal ferrites were characterized by different analytical techniques. The obtained results showed that the particle size of 20–30 nm for meso-CeFeO₃, and 80–100 nm for meso-RuFeO₃ respectively. Study of the adsorption of fluoxetine over metal ferrite nanoparticles was explored using UV–vis spectroscopy at different experimental conditions such as temperature, pH, initial fluoxetine concentration and time. The adsorption data were fitted and analyzed with kinetic and different adsorption isotherm models, and the results showed that both the metal ferrites effectively adsorbed fluoxetine (>99%). The maximum adsorption capacity of 729.6 mg g⁻¹ for CeFeO₃, and 683.5 mg g⁻¹ for RuFeO₃ at neutral pH and at 25 °C were observed. The amount adsorbed over the surface of metal ferrite nanoparticles increased with increasing initial fluoxetine concentration, reaction time, and temperature, and the adsorption performance improved under neutral conditions (pH 7 and 8). The pseudo-second order kinetic and Langmuir isotherm models satisfactorily fitted the adsorption data, showing that the adsorption of fluoxetine involved physical adsorption through intermolecular electrostatic force between the metal ferrites and fluoxetine which is further confirmed by intra-particle diffusion model. The observed wide band/gap, 3.815eV for CeFeO₃, and 3.360eV for RuFeO₃ respectively showed their stability towards visible light suggesting their real sample applicability, recovery and reuse capability involving physisorption with fluoxetine molecules. In addition, the feasible adsorption process of fluoxetine is analyzed with its geometry that is determined by theoretical energy calculations using DFT.