Synthesis and characterisation of mesoporous MgAl2O4 hollow spheres as a high-value product in a waste recovery strategy

Abstract

Micrometre-scale hollow sphere-shaped MgAl2O4 powders were synthesised using a spray-drying method, followed by calcination. An aqueous solution of mixed Mg2+ and Al3+ salts, derived from aluminium slag and serpentine tailings, served as a source of magnesium and aluminium. The secondary raw materials were subjected to acid leaching, and the refined leachates were used to prepare a spray-dried MgAl2O4 precursor, which was heat-treated at temperatures ranging from 550 °C to 1100 °C for 1 h. Characterisation of the resulting MgAl2O4 spinel powders was performed using various physicochemical techniques, including thermogravimetric and differential thermal analysis (TG-DTA), Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and physical adsorption using N2 (BET). The prepared MgAl2O4 spinel demonstrated several unique properties, including ultrafine particles with a uniform distribution (1–5 μm) and minimal particle agglomeration, high sintering activity (beginning at 550 °C), high purity, high specific surface area (110 m2 g-1/750 °C), and open porosity with a narrow pore size distribution (3–7 nm). These properties make the prepared MgAl2O4 spinel a highly valuable product for waste recovery strategies. The simplicity, efficiency, and cost-effectiveness of this process also predispose it to large-scale production of functional mixed metal oxides of various compositions for use in industries such as energy storage, sensing, and 3D printing fillers.