Preparation of highly efficient and eco-friendly alumina magnetic hybrid nanosorbent from red mud: Excellent adsorption capacity towards nitrate

The effectiveness of using red mud as the aluminum industry waste to fabricat a novel alumina magnetic hybrid (AMH) nanosorbent, which can remove nitrate from contaminated water was evaluated in current study. The characterization of the prepared nanosorbent were addresed by X-ray diffraction (XRD), X-ray fluorescence (XRF), surface area, transmission electron microscopy (TEM), and field emission scanning electron microscopy (FESEM) analysis. The results indicated the crystallite size of the Fe3O4 and γ -Al2O3 of about 18.7 and 19.6 nm, respectively, amount of Fe3O4 and γ -Al2O3 about 48.1 % and 51.2 % in the structure of nanosorbent, the surface area aroun 125.9 m2/g, and nanoparticles with approximately uniform size less than 25 nm along with a slight agglomeration. Studies on adsorption were performed using various contact time and initial nitrate concentrations, different pH and sorbent dosages. Maximum adsorption capacity was obtained at about 69 mg/g using 1 g/L sorbent dispersed in 100 ppm nitrate solution with a pH of 6 after 80 min. The adsorption data was appropriately fitted with Freundlich isotherm model, indicating multilayer adsorption. Regeneration experiments demonstrated that the nanosorbent could perform effective nitrate adsorption even after four regeneration cycles. The significance of this work is in the development of waste-driven, eco-friendly, and cost-effective creation of an AMH nanoadsorbent that effectively removes nitrate from contaminated water, which also has the advantage of rapid separation due to its magnetic properties.