Functionalized hierarchical cellulose aerogel for simultaneous removal of Pb(II), Cd(II), and Cr(VI): performance enhancement and adsorption mechanisms.

To address the combined pollution of Pb(II), Cd(II), and Cr(VI) in water, this study successfully fabricated aldehyde-functionalized aerogels (ACK) and thiol-functionalized aerogels (BCK) with hierarchical structures via periodate oxidation and L-cysteine grafting modification using α-cellulose as raw material, and systematically evaluated their synchronous adsorption performance toward the ternary heavy metal system. The results showed that both BCK and ACK could simultaneously remove Pb(II), Cd(II), and Cr(VI), and the adsorption capacity of BCK was significantly superior to that of ACK. The adsorption process involved both chemisorption and multilayer adsorption. The adsorption of Cd(II) and Cr(VI) onto BCK was endothermic and spontaneous, whereas that of Pb(II) was exothermic. Functional groups on the aerogel, including thiol, amino, hydroxyl, and carboxyl groups, collectively promoted the efficient removal of Pb(II), Cd(II), and Cr(VI) through complexation, chelation, electrostatic interactions, and redox reactions. After five regeneration cycles, the adsorption capacities of BCK for Pb(II), Cd(II), and Cr(VI) remained above 82%, indicating good reusability. This study provides a new strategy for developing green, efficient, and renewable biomass-based adsorbent materials for Pb(II), Cd(II), and Cr(VI) removal.