Aerogel‐Derived Mesoporous MgO for Fluoride Removal: Mechanisms and In Situ Groundwater Remediation Potential

ABSTRACT This study developed a novel aerogel magnesium oxide (AG‐MgO) adsorbent designed for the efficient removal of fluoride from contaminated groundwater. The aerogel method was employed to uniformly mix magnesium nitrate hexahydrate [Mg (NO 3 ) 2 ·6H 2 O] with chitosan to form precursor gel beads. Through high‐temperature calcination (600°C), Mg (NO 3 ) 2 ·6H 2 O was transformed into MgO particles, which were uniformly attached to the carrier for AG‐MgO formation. Batch and column experiments were conducted to characterize the produced AG‐MgO, identify optimal conditions, and evaluate the effectiveness of practical applications. Characterization results indicated that the synthesized AG‐MgO possessed a well‐developed porous structure with a specific surface area of 14.9 m 2 /g, a pore volume of 0.2 cm 3 /g, and an average pore size of 51.5 nm, providing a 3.5‐fold higher surface area than pristine MgO. In batch experiments, the optimal AG‐MgO dosage was determined to be 0.6 g/L for an initial fluoride concentration of 10 mg/L. The adsorption process was exceptionally well‐fitted by the pseudo‐second‐order kinetic model ( R 2 = 0.999) and the Langmuir isotherm model ( R 2 = 0.985); maximum adsorption capacity of 128.2 mg/g, firmly demonstrating that chemisorption was the rate‐controlling, dominant mechanism. Furthermore, continuous column trials validated its long‐term remediation efficacy, achieving an initial fluoride removal efficiency of 85% within the first three pore volumes (PVs), and maintaining a stable average removal efficiency of 62.4% over extended pumping (4–15 PVs). These findings suggest that AG‐MgO can be strategically deployed in practical in situ groundwater remediation, either via early‐stage upstream injection for rapid plume reduction or as a permeable reactive barrier for sustained and long‐term concentration control.