Coupled physicochemical dual-crosslinking Ti3C2Tx composite aerogels for the selective adsorption of gallium ions in acid fly ash leaching

Herein, in order to extract Ga3+ from acid fly ash leaching, we propose a functionalized Ti3C2Tx-based MXene composite aerogel adsorbent for Ga3+ adsorption. The prepared physicochemical dual-crosslinking network aerogel MPHG-40 possesses good Ga3+ adsorption performance (132.52 mg g- 1) at the pH of 3 and Ga3+ initial concentration of 50 mg L-1 within 6 h. After five adsorption-desorption cycles, the material shows good mass retention and a 95.65 % retention of its initial adsorption capacity, compared to most reported adsorbents. The optimized adsorbent realized good selective adsorption of Ga3+ against Cu2+, Zn2+, Fe3+, and Al3+ in a simulated acid fly ash leaching with the selective coefficient of 8.63, 96.10, 4.49, and 28.30, respectively. The adsorption may comply with a combined mechanism of physical adsorption, electrostatic interactions, ion-exchange mechanism, and ligand chelation, dominated by chemical adsorption, as identified by theoretical calculations based on density functional theory and experimental data. The three-dimensional solid adsorbent constructed in this study provides a new strategy for selective adsorption of Ga3+, making it possible to be applied to solid waste utilization of fly ash.