Synthesis of magnetically tuneable molybdic acid-functionalized Fe₃O₄ nanoparticles for efficient dye removal in aqueous media

Abstract: Textile dyes like rose bengal (RB) are infamous sources of pollution in the environment due to their persistence and toxicity. In this study, we explored the use of molybdic acid (MA)-functionalized iron oxide magnetic nanoparticles (MNPs) for the removal of RB dye from wastewater through the adsorption process. Nanoparticles were synthesized using a facile and cost-effective precipitation method and well-characterized for structural, magnetic and surface behaviours using XRD, FTIR, XPS, BET, HRTEM and VSM techniques. Adsorption properties of the nanoparticles were evaluated by varying the parameters, such as initial dye concentration, pH and contact time. Results showed that the MNPs had a high adsorption capacity for RB dye removal at 4 × 10⁻⁵ M concentration with an uptake of up to 89% within 100 min. At the optimal operation conditions, MA-functionalized Fe₃O₄ nanoparticles exhibited a maximum adsorption capacity of 60 mg g⁻¹ for RB dye, which is significant in comparison with the reported literature. Isotherm studies indicated that the adsorption process was spontaneous, exothermic and favoured at room temperature. It is also deduced that the process that occurred was physisorption, primarily the result of electrostatic attractions. Overall, this study suggests that MA-functionalized iron oxide nanoparticles have the potential to be an efficient material for the removal of textile dyes from wastewater. Graphical Abstract: Molybdic acid functionalized Fe₃O₄ nanoparticles prepared through facile co-precipitation method shows intriguing electrostatic interaction with anionic rose Bengal dye. The interaction gets stronger at low pH due to extremely protonated surface of the adsorbent. (Figure presented.)