چكيده به لاتين
The effectiveness of using red mud as the aluminum industry waste to fabricat a novel alumina magnetic hybrid nanosorbent, which can remove nitrate from contaminated water was evaluated in current study. Red mud due to its wide production, presence of some radioactive elements, high alkalinity, and salinity, has a dramatic potential to contaminate soil and groundwater. Notwithstanding its drawbacks, Red mud consists several elements, including Ca, Al, Ti, Si, and Fe, in various mineral forms. In the peresent study, stepwise leaching was applied as a proper method to separate and purify the main valuable elements using available and affordable HCl. The pre-leaching step under optimized conditions using HCl (0.2 M) at room temperature for 2 h removed 89% of the calcium content from red mud. To selectively remove the solid silica, the residue was treated with concentrated HCl (3.0 M, L/S of 20 mL/g) at 95 °C, resulting in the dissolution of iron and aluminum content with up to 90% efficiency. After precipitation step, inexpensive red mud was converted into highly valuable nano-sized metal oxides using simple, sustainable techniques and cheap reagents. 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 around 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 a novel alumina magnetic hybrid nanosorbent that effectively removes nitrate from contaminated water, which also has the advantage of rapid separation due to its magnetic properties. Moreover, this technique generates the lowest amounts of waste during the leaching process and all reagents can be recycled for further uses, making this method a sustainable utilization.
